ABSTRACT. Solid–fluid reactive systems are fundamental to thermochemical biomass conversion technologies such as pyrolysis and gasification. Further progress in these processes requires a detailed understanding of the coupled transport, reaction, and structural evolution phenomena occurring at the scale of individual particles, which may govern reactor performance [1]. In pyrolysis reactors, particle-scale heat and mass transfer strongly interact with chemical reactions and evolving material properties, directly affecting conversion rates and product yields [1]. However, resolv-ing intra-particle dynamics remains computationally expensive, and most reactor-scale models therefore rely on simplified particle representations. Spatially resolved continuum particle models provide detailed descriptions of intra-particle temperature gradients and transport–reaction coupling but typically assume isotropic properties, uniform boundary conditions, and idealized particle geometries. These assumptions do not generally hold for biomass, due to its hierarchical structure, anisotropic pore network, and non-spherical shape. Pore-resolved studies have demonstrated the importance of intra-particle anisotropic transport during pyrolysis and gasification [2-5], but their computational cost limits their applicability to very small systems. To bridge the gap between physical fidelity and computational efficiency, this work presents a three-dimensional, pore-informed, continuum particle model for biomass pyrolysis. The model incorporates pore-informed and direction-dependent transport properties, derived from pore-resolved simulations, to account for the influence of pore network on heat and mass transport, as well as on transport-chemistry interactions during pyrolysis. This approach enables spatially resolved predictions of intra-particle temperature and conversion at a computational cost suitable for practical simulations and integration into multiphase reactor models. Model development and validation are supported by a dedicated experimental campaign measuring internal (several intra-particle positions) and surface particle (with phosphor thermometry) temperatures during pyrolysis. The impact of anisotropic intra-particle pore structure is addresed by comparing natural with densified particles, both using beech wood. Experiments are perfor-med under constant heating rates, representative of slow pyrolysis, and under rapid, isothermal heating conditions relevant to industrial reactors. The combined experimental and simulation results demonstrate the critical role of particle anisotropy and heating mode on intra-particle transport and pyrolysis behavior, providing a physically grounded and computationally efficient pathway for improved particle-scale modeling in biomass pyrolysis. [1] P. N. Ciesielski, M. B. Pecha, N. E. Thornburg, M. F. Crowley, X. Gao, O. Oyedeji, H. Sitaraman, N. Brunhart-Lupo, Energy & Fuels 35 (18) (2021) 14382–14400. doi:10.1021/acs.energyfuels.1c02163. [2] M. F. Crowley, H. Sitaraman, J. Klinger, F. Usseglio-Viretta, N. E. Thornburg, N. Brun-hart-Lupo, M. B. Pecha, J. H. Dooley, Y. Xia, P. N. Ciesielski, Frontiers in Energy Rese-arch 10 (2022). doi:10.3389/fenrg.2022.850630. [3] A. Dernbecher, S. Bhaskaran, N. Vorhauer-Huget, J. Seidenbecher, S. Gopalkrishna, L. Briest, A. Dieguez-Alonso, Particuology 98 (2025) 172–190. doi:10.1016/j.partic.2025.01.006. [4] M. F. Crowley, R. Seiser, M. A. S. Posada, J. C. Maya, F. Chejne, H. Sitaraman, F. Usseglio-Viretta, A. K. Starace, P. N. Ciesielski, Energy & Fuels (2025). doi:10.1021/acs.energyfuels.5c04362. [5] D. Liang, S. Singer, Proceedings of the Combustion Institute 39 (3) (2023) 3293–3302. doi:10.1016/j.proci.2022.07.098.

ABSTRACT. This study presents an innovative integrated pathway for the efficient, clean production of hydrogen-rich syngas from biomass, addressing key challenges of conventional gasification such as high tar yields and inefficient feedstock utilization. The proposed strategy synergistically combines low-temperature pyrolysis pretreatment, co-briquetting of pyrolysis products, and subsequent steam-oxygen gasification. The process begins with the low-temperature pyrolysis of biomass (corn stalks as a primary feedstock) in a continuous-feed rotary kiln reactor across a temperature range of 300–500℃. The resulting bio-oil is separated by settling, and its heavy fraction—typically difficult to utilize due to its high viscosity and macromolecular content—is repurposed as an effective binder. This heavy bio-oil is mixed with the solid pyrolytic biochar and co-briquetted under pressure to form dense, mechanically robust oil-char briquette fuels. Finally, these briquettes undergo steam-oxygen gasification in a fixed-bed reactor, with systematic optimization of critical parameters including pyrolysis temperature, gasification temperature, equivalence ratio (ER), and steam-to-carbon ratio (S/C). The results demonstrate that low-temperature pyrolysis at 400 ℃ optimally transforms corn stover biochar, significantly lowering its O/C and H/C atomic ratios, developing a porous structure, and enriching catalytically active alkali metals. Using the heavy bio-oil fraction (20 wt% of biochar) as a binder successfully solved the technical challenge of poor briquetting associated with pyrolytic biochar, significantly enhancing the mechanical strength of the briquettes to meet industrial standards while providing a value-added outlet for the heavy oil. Gasification performance was markedly superior using these briquette fuels compared to raw biomass. Under optimized conditions (gasification temperature of 1000 ℃, ER=0.15, S/C=3), the briquette fuel derived from 400 ℃ pyrolysis achieved exceptional results: a high H₂ yield of 32.47 mol/kg, an H2 mole fraction of 46.87% in the syngas, and an H2/CO ratio of 1.42. Crucially, this two-stage pyrolysis-briquetting-gasification process led to a dramatic reduction in tar yield compared to the direct gasification of corn stalks, particularly when the initial pyrolysis temperature exceeded 400 ℃. Tar content was reduced to approximately 90 mg/Nm³, with GC/MS analysis showing a significant decrease in polycyclic aromatic hydrocarbons. Parameter optimization revealed that increasing the gasification temperature from 700 °C to 1000°C enhanced endothermic reactions, raising total gas yield and cold gas efficiency (CGE). An optimal S/C ratio of 3 maximized H2 production by promoting the water-gas shift reaction without excessively cooling the reaction zone. The ER effectively modulated the syngas composition, with lower ER favoring higher H2 concentration. Furthermore, the universality of this integrated route was validated using diverse biomass feedstocks, including wheat straw, rice husk, bean shell, and sawdust. While wheat straw-derived briquettes exhibited the best mechanical strength due to its fibrous structure, bean shell-derived fuel yielded 26.36 mol H2/kg, demonstrating the broad applicability of the technique. A mixture of feedstocks showed synergistic effects, indicating potential for further optimization. In conclusion, this work establishes a technically feasible and effective strategy for the fractional and value-added utilization of all biomass pyrolysis components. By integrating low-temperature pyrolysis, product co-briquetting, and optimized gasification, it enables the clean production of high-quality, hydrogen-rich syngas with low tar content.

ABSTRACT. The demand for sustainable materials is greater than ever. The utilisation of cellulose materials, such as cellulose nanocrystals (CNCs), as support materials for catalysis together with catalytically active metals has been documented in literature for some time. CNCs are also frequently used as reducing agents in the synthesis of metal nanoparticles, combining reductive and support functionalities. The present study compares two novel methods for catalyst production. The aim is to produce highly porous carbon materials doped with catalytically active iron species. As starting material cellulose-based Pickering emulsions were used. These emulsions contain high concentrations of iron salt, which, after conversion to iron-containing nanoparticles, will form the active catalytic fraction. In an autogenic pressure carbonisation (APC) process, emulsions were freeze-dried to remove all liquid components (water and oil) after which they were carbonised. In a second approach, we used hydrothermal carbonisation (HTC) where the emulsion remains in its liquid form and is carbonised in an autoclave reactor. The collected hydrochar product is then separated from the liquid phase by vacuum filtration, after which it is carbonised further in a tube furnace. The products were characterised using SEM and SAXS to obtain information about the porosity and surface structure. Additionally, WAXS measurements were performed to identify emerging iron species and to characterize crystallinity. XPS was further carried out to gather information about the chemical composition, especially on the surface of the sample, to determine whether the existing compounds could potentially promote catalytic processes and to obtain information about the carbonisation.

ABSTRACT. Biomass-derived furfural is a critical platform chemical with broad applications in production of high value-added pharmaceuticals, agriculture and biofuels. Its global production capacity exceeds 1 million tons annually, and over 70% is produced in China. On the other hand, the global furfural market surpasses $1 billion in 2024, while keeping an annual growth rate (CAGR) of 4-5% over the past decade. Despite its great potential, the industrial-scale production of furfural is hindered by the formation of humin via complex side reactions. This study examines the pivotal roles of steam and catalyst in regulating the conversion process of biomass to furfural in terms of raising the product yield to its possibly highest value. A special focus made to clarify how the humin formed in the process affects the final production of furfural. We clarified the mechanism of humin formation and the precise effects of Brønsted acids, Lewis acids, and their synergistic interactions in the sequential reactions of hydrolyzing hemicellulose to xylose and dehydrating xylose to furfural. Beyond catalysis, the influence of reaction media is deeply analyzed, by comparing the solubility and protective capabilities of monophasic mixtures versus those of biphasic extraction systems. Analyzing literature data reveals that coordinating acid sites and appropriate organic solvents can effectively suppresses humin formation and enhance furfural production. The most important cognition is that the formed furfural can react with xylose to form humin. Using Brønsted acid lowers the activation energy of this humin formation reaction to a large extent, thus speeding up the total loss of furfural as well as xylose to decrease the yield of furfural. Based on these insights, a series of experiments were designed to mimick the industrial furfural production process widely adopted in China, where corn cob was used as feedstock and sulfuric acid as the catalyst. These experiments aimed to explore practically feasible approaches to improve the furfural yield. Leveraging the experimental data about the effects of sulfuric acid dosage, reaction temperature and pressure, as well as of the packing state of corn cob, reactor connection mode and steam-flow velocity, we well identified the key factors that determine the furfural yield in the currently existing industrial. (1) A good balance between water evaporation and vapor condensation. It is critical to ensure a possibly sufficient supply of water to the involved biomass valorization reactions, while simultaneously removing the produced furfural from the reactor timely. (2) The precise control of water vapor flow rate, temperature and pressure in the reactor to maximize the furfural yield effectively.

References: [1] Y. Wang, C. Zhang, C. Cai, C. Huang, X. Shen, H. Lou, C. Hu, X. Pan, F. Wang, J. Xie, Advances in humins formation mechanism, inhibition strategies, and value-added applications, Chinese Journal of Catalysis 71 (2025) 25-53. [2] E. Cousin, K. Namhaed, Y. Peres, P. Cognet, M. Delmas, H. Hermansyah, M. Gozan, P.A. Alaba, M.K. Aroua, Towards efficient and greener processes for furfural production from biomass: A review of the recent trends, Sci Total Environ 847 (2022) 157599.

ABSTRACT. Pyrolysis, as an important way to achieve efficient conversion and utilization of coal and waste plastics, can convert them into liquid fuels or high-value-added chemicals. The co-pyrolysis of coal and waste plastics not only improves the yield and quality of tar, but also achieves the resource utilization, harmless treatment, and clean treatment of waste plastics. However, the existence of PVC (about 56% chlorine) in waste plastics makes the process complicated, which causes environmental pollution and reduces the quality of the oil product. Extensive research on co-pyrolysis of coal and non-halogen waste plastics has been conducted to understand their performances and synergistic mechanisms, and also the single PVC pyrolysis behavior and chlorine migration. However, waste plastics are often recycled in the form of mixtures, which contain non-halogen plastics, such as polyethylene (PE), polystyrene (PS), and PVC, the co-pyrolysis behavior and mechanism of coal with PVC or mixed plastics containing PVC are still to be explored. In this topic, the co-pyrolysis of coal with PVC, or the mixed plastics of PVC/LDPE or PVC/PS were carried out to investigate the pyrolysis behavior, product distribution and composition, the synergistic effect and mechanism of coal and plastics. The results show that in co-pyrolysis of Pingshuo coal (a low rank coal) with PVC, benzene has the highest relative content among the volatile products, which is mainly generated at low temperature stage (below 327 oC). High temperature (327 to 650 oC) is beneficial to enhance the cyclization/ alkylation reaction and promote the production of light tar. In coal/PVC co-pyrolysis system, the addition of LDPE facilitates the production of butene and benzene at low temperatures. Moreover, LDPE promotes the cleavage of Cal-Car and Cal-O bonds connected to the aromatic ring in coal, increasing the production of phenolic products. The addition of PS to coal/PVC can significantly promote the generation of styrene with the highest content and benzene with the second highest content in the volatile products. The addition LDPE or PS to coal/PVC all makes the reduction of chlorinated compounds content and improves the tar quality.

Figure 1: Relative content of primary volatiles from Coal/PVC/PS (6:1:1) pyrolysis.

References [1] Yang, J., Wu, Y., Zhu, J., Yang, H., Li, Y., Jin, L., Hu, H. 2023. Insight into the pyrolysis behavior of polyvinyl chloride using in situ pyrolysis time-of-flight mass spectrometry: aromatization mechanism and Cl evolution. Fuel, 331, 125994. [2] Wang, K., Ban, Y., Wu, Y., Jin, L., Hu, H. 2023. Synergistic effect and chlorine migration behavior in co-pyrolysis of Pingshuo coal and polyvinyl chloride and directional chlorine enrichment using calcium oxide. Fuel, 349, 128749. [3] Zhang K., Wu Y., Wang D., Jin L., Hu H. 2021. Synergistic effect of co-pyrolysis of pre-dechlorination treated PVC residue and Pingshuo coal. : J Fuel Chem Technol, 49(8), 1086.

ABSTRACT. Co-pyrolysis of coal and waste tire presents a promising waste-to-energy strategy, however, sulfur migration poses significant environmental concern. Therefore, this study investigated the sulfur transformation behaviors during co-pyrolysis based on the distribution of total sulfur in gaseous, liquid, and solid products under varying heating rates, temperatures and blend ratios, along with the existence forms and bonding states of sulfur in derived chars to elucidate the sulfur migration mechanism. Results showed that high heating rate facilitated the transfer of sulfur from solid phase to liquid phase. Meanwhile, the release of sulfur-containing gases in both individual pyrolysis and co-pyrolysis increased with the heating rate, however, the generation of H2S was significantly suppressed under high heating rate. Sulfur is mainly concentrated in char during tire pyrolysis, different from coal pyrolysis where sulfur primarily distributed in liquid-phase products. The temperature affected the distribution of sulfur in co-pyrolysis products. When the temperature is above 550 oC, co-pyrolysis promoted the transfer of sulfur from solid and gas phases to liquid phase. Additionally, the yield of sulfur-containing gases during individual pyrolysis and co-pyrolysis increased as the temperature increased. Similarly, co-pyrolysis suppressed the generation of H2S with the temperature being over 550 oC, while the generation of COS and CH3SH was related with the mixing ratio of coal and waste tire. Further analysis of the occurrence forms of sulfur on co-pyrolysis chars at 600 oC revealed that the peak intensities corresponding to ZnS and ZnO in co-pyrolysis chars are significantly reduced, and their experimental relative contents were lower than theoretical relative contents compared to char from tire pyrolysis, which was in correspondence with the inhibitory effect on sulfur distribution in co-pyrolysis char. The study provided an insight into sulfur migration behavior during co-pyrolysis of coal and waste tire, contributing to reducing pollutant emission and enhancing waste valorization, which supports the development of cleaner co-processing technologies for sustainable energy production and effective waste management.

ABSTRACT. Coal is a precious resource in many countries around the world. The aromatic ring structure plays a crucial role in the composition of coal, being interconnected through bridging, ether, and thioether bonds, along with diverse side chains. The development of directed hydrogenolysis of coal under mild conditions to yield aromatic compounds signifies a pioneering approach for the non-energy utilization of coal, effectively augmenting the added value of coal-derived products. In this work, a synergistic catalyst system composed of PtPdCoNiCu/C high-entropy alloy and H4SiW12O40 has been formulated for the catalytic hydrogenolysis of C-O bonds in coal-derived compounds and low-rank coal. The conversion of benzyl phenyl ether achieves an impressive 99.8%, with yields of toluene (99.8%) and phenol (99.2%) at 50 °C and 0.1 MPa H₂ for 2 h. The apparent activation energy (Ea) for this synergistic catalyst system is merely 31.6 kJ/mol, significantly lower than that of the PtPdCoNiCu/C catalyst alone (86.4 kJ/mol), suggesting that hydrogen spillover facilitates the surface hydrogenolysis of C-O bonds. The products formed are aromatic compounds, devoid of any over-hydrogenated derivatives. Furthermore, an effective method for the hydrogenolysis of C-O bonds by microwave catalysis has been developed. The collaboration of the Pt/CB catalyst with H4SiW12O40, coupled with a high-permittivity polar solvent (1,4-butyrolactone), enhances the microwave-assisted hydrogenolysis of the C-O bonds in the coal-derived platform molecule (benzyl phenyl ether). The microwave heating proves to be more effective than the conventional electric heating. Following optimization of the catalytic conditions, the Pt/CB and H4SiW12O40 catalyst presents highly efficient in 10 min and 300 W with benzyl phenyl ether conversion of 99.9%. This metal-acid catalytic strategy is applied to the hydrogenolysis of other coal-based aromatic ethers and Naomaohu coal, possible providing new opportunities for producing value-added aromatics from coal.

ABSTRACT. The catalytic pyrolysis of polyethylene over acidic zeolites such as ZSM-5 is a promising approach for the selective production of added-value hydrocarbons. However, the majority of experimental studies are still performed using powdered catalysts, which limits their applicability to realistic reactor configurations and hinders process scale-up. Addressing this gap requires not only appropriate reactor design but also the development of shaped engineered catalyst particles with mechanical strength and controled particles sizes.

In this study, ZSM-5 zeolite was shaped (with binders) into millimetric granules using an extrusion–granulation approach designed to preserve its acidic and textural properties while ensuring sufficient mechanical strength and a tailored particle size for its use in fixed-bed or stirred reactors. The influence of catalyst shaping and positioning on polyethylene pyrolysis was systematically investigated using 2 complementary reactors (batch and continuous).

First, batch sample boat experiments were conducted to compare the catalytic behavior of powdered ZSM-5 and shaped ZSM-5 under identical operating conditions. In addition to direct catalyst–polymer contact (in-situ), a fixed-bed catalytic zone was installed downstream of the sample boat reactor to study ex-situ configuration with the shaped ZSM-5. The zeolites was further evaluated in a continuous staged reactor. In the in-situ configuration, the catalyst was introduced directly into a stirred continuous pyrolysis reactor, ensuring intimate contact with the molten polymer. In contrast, the ex-situ configuration involved positioning the shaped zeolite in a downstream fixed bed reactor, where it selectively interacts with pyrolysis vapors.

This work highlights the effect of both zeolite shaping and catalyst positioning in catalytic polyethylene pyrolysis. It assesses the catalytic behavior of zeolites under conditions relevant to scalable reactor designs, and supports the development of engineered catalytic particles for plastic waste pyrolysis.

ABSTRACT. The exponential growth in plastic waste streams, particularly polyolefin-based wastes such as waste polypropylene (WPP), necessitates the development of scalable and sustainable valorization routes beyond incineration and low-value recycling [1]. Herein, an integrated waste-to-chemicals approach, coupling thermo-catalytic pyrolysis of WPP with in-line CO2 reforming of pyrolysis gases for the coproduction of high-value liquid hydrocarbons and synthesis gas, is demonstrated [2]. Pyrolysis of WPP was performed in a two-stage configuration, in which pyrolysis vapors produced during thermal cracking were subsequently upgraded over FAU, BEA, and MFI (ZSM-5) zeolite catalysts featuring similar Si/Al ratios. The goal was to establish clear structure-activity-selectivity relationships in catalytic pyrolysis of WPP over zeolites of different framework. From the results as presented in Fig. 1a, noticeable differences in product distributions were observed as a function of zeolite framework topology. Furthermore, based on the analysis of pyrolysis oils, ZSM-5 was found to catalyze extensive secondary cracking and dehydroaromatization resulting in aromatics-rich pyrolysis oil dominated by BTEX (benzene, toluene, ethylbenzene, and xylenes). In contrast, FAU and BEA promoted the formation of aliphatic hydrocarbons. Clear differences were also observed in the composition of the gaseous products when different zeolites were employed as catalysts. Nevertheless, in all cases, the hydrocarbons observed ranged from C1 to C5. A further goal of this work was to upgrade the pyrolysis gases into syngas. For this purpose, CO2 reforming of the pyrolysis gases was carried out over hydrotalcite-derived mono (Ni) and bimetallic (Ni-Co) catalysts at 650–800 °C. Despite exhibiting high activity at temperatures above 750 °C, monometallic Ni catalysts suffered from pronounced coke formation, which adversely affected the overall syngas yield. In contrast, the coke formation was significantly suppressed by doping Ni -hydrotalcite catalyst with cobalt. In particular, among a series of formulations screened, Ni9.5Co0.5 was identified to have the most favorable combination of activity and stability, providing high CO2 and hydrocarbon conversions, improved coke resistance, and excellent syngas yield (Fig. 1b). The superior performance of the bimetallic catalysts can be ascribed to the synergistic Ni-Co interactions, which enhance CO2 activation, and promote the activation of surface oxygen species, thereby facilitating in-situ carbon gasification [3].

Acknowledgment: This work was financially supported by the ESF in “Waste as an alternative source of energy” project, reg. nr. CZ.02.01.01/00/23_021/ 0008590 within the Programme Johannes Amos Comenius and by REFRESH – Research Excellence For Region Sustainability and High-tech Industries, CZ.10.03.01/00/22_003/0000048 and large research infrastructure ENREGAT supported by MŠMT, project no. LM2023056.

Reference: [1] S.Z. Khairul Anuar, A.H. Nordin, S.M. Nur Husna, A.H. Yusoff, S.H. Paiman, S.F. Md Noor, M.L. Nordin, S.N. Ali, Y.M. Nazir Syah Ismail, Journal of Environmental Management, 380 (2025) 124867. [2] A. Inayat, A. Inayat, K. Klemencova, W. Schwieger, P. Lestinsky, Fuel, 371 (2024) 131975. [3] S. Das, M. Sengupta, A. Bag, M. Shah, A. Bordoloi, Nanoscale, 10 (2018) 6409.

ABSTRACT. Understanding the carbon deposition process from plastic pyrolysis carbon sources is of great significance for the design and synthesis of carbon materials or the development of anti-coking catalysts. This study investigates the key factors influencing carbon nanotube (CNT) yield by selecting model compounds representing specific plastic pyrolysis carbon sources for experiments and combining them with DFT calculations to establish a correlation between carbon yield and the bond dissociation energy (BDE) of the carbon sources. The results show a positive correlation between liquid alkane carbon sources with different carbon numbers and carbon yield. DFT calculations of the BDE for carbon sources with different chain lengths and isomers reveal that carbon yield is negatively correlated with the average BDE, particularly showing a more significant negative correlation with lower BDEs. In contrast, for higher BDEs, carbon yield does not exhibit a clear linear relationship. As the number of carbon atoms in the carbon source increases, the interlayer spacing of the carbon nanotubes shows an expanding trend, while the outer diameter exhibits a pattern of first increasing and then decreasing. Using liquid carbon sources enables the synthesis of various CNT morphologies, including multi-walled hollow rings, slender straight tubes, tubes with different wall thicknesses, and helical structures. The carbon layers of these nanotubes can precipitate at different sites of metal particles and stack to form walls consisting of up to dozens of layers. The precipitated carbon layers can either stack onto existing carbon walls or merge with other carbon walls through alternative growth pathways, thereby forming thicker wall structures. These findings provide a theoretical basis for the precise control of CNT structure and the enhancement of yield, laying the groundwork for the controllable preparation of carbon nanotubes in the resource utilization of waste plastics.

ABSTRACT. In Chile, mining operations generate approximately 49,000 tons per year of waste mining truck tires (MTWT), accounting for 28% of the country's total end-of-life tires. This accumulation poses severe logistical and environmental challenges to the productive sector and the ecosystems, respectively. In response, Chile's Extended Producer Responsibility Law (REP Law 20.920) mandates 100% recycling of MTWT by 2030, incentivizing the development of advanced valorization technologies such as pyrolysis. During pyrolysis, the polymeric fraction of waste tires thermally decomposes to yield vapors enriched in limonene (over 20 wt.% of the pyrolytic oil)—a renewable precursor to valuable monoaromatics like cymene. However, the selectivity of cymene formation under non-catalytic conditions is typically <10%, requiring catalytic systems. Here, we investigate the mechanistic role of bifunctional Pd/S (S = TiO₂, ZrO₂, TiO₂–ZrO₂) catalyst in the selective transformation of limonene to cymene. Catalysts with varying densities of acid sites were synthesized via wet impregnation (1 %wt. Pd) and featured similar textural (SBET = 50 m2.g-1) and structural properties (Metal Dispersion ≈ 56%). Moreover, their acidity (predominantly Lewis) ranked as follows: TiO₂ < Pd/TiO₂ < ZrO₂–TiO₂ < Pd/ZrO₂–TiO₂. Catalytic screening and kinetic studies were quantitatively conducted using a Frontier tandem microreactor system (Rx-3050TR) coupled to a GC-MS/FID, where pyrolysis of natural rubber (model tire) occurred at 400–500 °C. The catalytic vapor-phase upgrading was carried out in ex-situ mode between 300 – 500 °C, with catalysts mass of 1.1 – 8.3 mg. Based on the non-catalytic and catalytic experiments the limonene-to-cymene reaction involves (1) isomerization of limonene to terpinenes followed by dehydrogenation to cymene; (2) direct dehydrogenation of limonene to p-cymenene; and (3) parallel side reactions forming alkenes and cycloalkenes. Catalytic performance was governed by acid site distribution rather than total acidity. While normalized limonene conversion remained nearly constant (~15%/mgcat⁻¹), the cymene formation rate increased linearly with the proportion of weak acid sites (W/TS), from 10.1 to 14.5 μmol·mg_cat⁻¹·s⁻¹. This trend supports a bifunctional mechanism where weak Lewis’s acid sites promote isomerization to terpinene intermediates, followed by dehydrogenation to cymene on Pd sites. Cymenene production was significantly lower (1.0–3.7 μmol·mgcat⁻¹·s⁻¹), confirming selective activation of the exocyclic double bond and preferential cymene formation. These results highlight the synergistic role of acid–metal interfaces in directing product selectivity. A Langmuir–Hinshelwood kinetic model accounting for competitive adsorption of reactants and byproducts reveals that the initial hydrogen abstraction from limonene and dehydrogenation of terpinenes are rate-limiting for pathways (2) and (1), respectively. This work offers a mechanistic and kinetic framework for fundamental understanding the catalytic upgrading of pyrolysis vapors and contributes to the advancement of waste-to-aromatics strategies for circular economy applications in mining.

ABSTRACT. Mixed plastic was converted into high-performance porous carbon for supercapacitor electrodes using a pyrolysis–KOH activation strategy. Pyrolysis char derived from PET, PC, PU, PS, and ABS was activated to develop a high surface area and hierarchical pore structure. Feed composition significantly influenced pore evolution, where PS promoted pore development and PU contributed nitrogen functionalities. The resulting carbons exhibited well-developed micro/mesoporosity favorable for ion transport. Electrochemical evaluation showed enhanced capacitive behavior and rate performance, demonstrating the suitability of mixed-plastic-derived carbons for supercapacitor applications. This study highlights the composition–structure–performance relationship and provides a sustainable pathway for transforming plastic waste into value-added electrochemical energy storage materials.

ABSTRACT. Waste plastics can be easily depolymerized via pyrolysis to oil, which can be further valorized to produce base chemicals. A wide distillation range of plastic pyrolysis oils results in a high melting point, and the amount of heteroatoms exceeds limits for steam cracking feedstocks. Those aspects complicate the direct valorization of plastic oil in steam cracking, and oil upgrading is thus desired. In this research, we studied a complex hydroprocessing strategy to upgrade oil from the pyrolysis of mixed post-consumer waste polyolefins in a flow-fixed-bed catalytic unit at a wide range of conditions. The waxy oil produced by industrial-scale continuous pyrolysis exhibited a wide distillation range of over 600°C and contained significant amounts of heteroatoms, especially nitrogen, and metals. In the first step, the sample was hydrotreated over a sulfided Ni-Mo/γ-Al2O3 catalyst to reduce the nitrogen content to below 25 mg/kg, thereby preventing deactivation of the hydrocracking catalyst. The hydrotreated sample was hydrocracked over a sulfided Ni-W catalyst at various conditions in the following step. Two approaches were compared: (i) hydrocracking of the whole sample and (ii) the sample free of the naphtha fraction. Hydrogen consumption and off-gas composition were monitored online during hydroprocessing using a refinery gas analyzer. The comprehensive analysis of liquid products was carried out using GC×GC-FID/MS. During the conference, the following aspects will be discussed: 1) The effect of hydrotreating temperature on the olefin’s saturation and heteroatom’s removal. 2) The stability of the hydrotreating catalyst during the processing of 30 kg of plastic pyrolysis oil. 3) The effect of the hydrocracking conditions on a liquid product's final boiling point reduction and its composition changes regarding the use as a feedstock for steam cracking. 4) The benefit of sample distillation before hydrocracking, including hydrogen savings. 5) Overall comparison of the studied hydroprocessing approaches, including the mass balance from plastic waste to steam cracking feedstock.

ABSTRACT. Hybrid thermochemical-biological is a relatively novel way to overcome the complexity of bio-oils derived from biomass’s pyrolysis. In this approach, microorganisms in both single or mixed cultures are used to funnel the aqueous phase liquid (APL) of bio-oil and incondensable products obtained from the thermochemical step into few valuable products such as methane or volatile fatty acids (VFA) [1]. However, despite the efforts, the direct fermentation of APL has been proved to be feasible only in presence of a easily fermentable co-feed, which may be provided by sugary addition to the fermentation broth, making the process economically unsustainable [2]. To overcome this issue, combination of hydrothermal carbonization (HTC) and pyrolysis has been proposed as a way to deliver a sugar enriched thermochemical output [3,4], however the fermentation of the obtained solution was not yet tested. In this study, HTC performed at two temperatures (150 and 200°C) and both intermediate and fast pyrolysis were coupled. The solutions obtained, namely HTC liquids and APL from pyrolysis, were individually fermented utilizing mixture cultures and anaerobic conditions (nitrogen environment and 55°C). Daily analyses were performed to trace the production of VFA and biogas (chemical oxygen demand content, GC-MS, GPC). As a result, APL derived from fast pyrolysis from both HTC pre-treated and not, were not converted even after 100 days of experiment, meanwhile intermediate pyrolysis APLs solutions display degradation after only 5 days (Figure 1). Moreover, APL derived from HTC pre-treatment displayed a similar degradation as for direct pyrolysis, highlighting an increased share of chemical energy converted when HTC is applied.

Figure 1. Levoglucosan trend during fermentation of APL from intermediate and fast pyrolysis.

Bibliography [1] R.C. Brown, Hybrid thermochemical/biological processing: Putting the cart before the horse?, in: Springer, 2007: pp. 947–956. https://doi.org/10.1007/s12010-007-9110-y. [2] Y. Küçükağa, A. Facchin, S. Kara, Tülin Yılmaz Nayır, D. Scicchitano, S. Rampelli, M. Candela, C. Torri, Conversion of Pyrolysis Products into Volatile Fatty Acids with a Biochar-Packed Anaerobic Bioreactor, Cite This Ind Eng Chem Res 2022 (2022) 16624–16634. https://doi.org/10.1021/acs.iecr.2c02810. [3] A. Facchin, Y. Küçükağa, D. Fabbri, C. Torri, Analytical evaluation of the coupling of hydrothermal carbonization and pyrolysis (HTC-Py) for the obtainment of bioavailable products, J. Anal. Appl. Pyrolysis 175 (2023) 106185. https://doi.org/10.1016/j.jaap.2023.106185. [4] M. Usman, H. Chen, K. Chen, S. Ren, J.H. Clark, J. Fan, G. Luo, S. Zhang, Characterization and utilization of aqueous products from hydrothermal conversion of biomass for bio-oil and hydro-char production: a review, Green Chem. 21 (2019) 1553–1572. https://doi.org/10.1039/C8GC03957G.

ABSTRACT. Fast pyrolysis of lignocellulosic biomass represents a powerful thermochemical route for the conversion of renewable carbon resources into value-added materials. In this contribution, we report the synthesis of carbon dots (CDs) through the fast pyrolysis of biomass performed in a modified wire-mesh reactor, referred to as a heated strip reactor (HSR). The HSR differs from conventional wire-mesh reactors in that the metallic grid traditionally used as a sample holder is replaced by a pyrolytic graphite foil, which acts both as a mechanical support and as a resistive heating element. This configuration allows the reactor to reach temperatures as high as 2073 K while maintaining extremely high heating rates, on the order of 10⁴ K s⁻¹, which are ideal conditions for probing intrinsic fast-pyrolysis pathways. Small amounts of lignocellulosic biomass were deposited on the graphite strip and subjected to rapid heating under controlled atmospheres. Under these conditions, thermal decomposition occurred within milliseconds, generating volatile species that were immediately quenched upon leaving the hot zone. The rapid quenching, enabled by the strong temperature gradient between the heated strip and the surrounding environment, effectively suppressed secondary reactions of the vapors, such as cracking, repolymerization, and gas-phase aromatization. The volatile products condensed on a Pyrex glass bridge positioned above the HSR collected and were subjected to solvent extraction and fractionation using organic solvents of different polarity (acetone and N-methylpyrrolidone, NMP), allowing the separation of fractions with distinct chemical compositions. These fractions were characterized by spectroscopic techniques, Size Exclusion Chromatography (SEC) and gas chromatography mass spectrometry (GC-MS, only in the case of acetone fraction) in order to check their fluorescence, size and chemical composition, respectively. The first extraction in acetone allowed isolating species, which exhibit intense blue photoluminescence under UV–visible excitation and size in the range 1.5-2.5 nanometers. The fraction insoluble in acetone was dissolved in NMP, obtaining species fluorescing in green region and having size in 1.7- 2.8 nm range. The formation of CDs is attributed to the rapid thermal breakdown of biopolymers followed by the nucleation of small aromatic clusters, whose growth is arrested by the extremely short residence time at high temperature and by immediate quenching. The surface chemistry, rich in oxygen-containing functional groups inherited from the biomass precursor, is believed to play a key role in CD photoluminescent behavior. This study demonstrates that fast pyrolysis reactors, when operated under well-controlled high heating rate and short vapor residence time conditions, can be exploited not only for fuel and chemical production, but also as one-step approach to synthesize functional bio-derived carbon nanomaterials. The possibility of selectively isolating different classes of CDs through solvent fractionation further highlights the versatility of the approach. The CDs obtained show significant potential for applications in photonics, optoelectronics, chemical sensing, and other advanced materials fields. Overall, the work emphasizes the added value that fast pyrolysis can provide in the context of sustainable materials synthesis, opening new perspectives for the integration of pyrolysis science with nanomaterials engineering.

ABSTRACT. Pyrolysis is a key technology for transforming lignocellulosic biomass into liquids that can be further processed into high-value fuels and chemicals. Conventional pyrolysis requires relatively high operating temperatures. However, a slow heat transfer can negatively affect depolymerization efficiency and product selectivity. Molten salt-assisted thermal treatment has therefore attracted increasing interest in biomass conversion, as molten salts can enhance heat transfer through their high thermal conductivity and heat capacity. In earlier work from our group, pyrolysis of sawdust in the presence of a molten salt mixture at a salt-to-biomass weight ratio of 10:1 resulted in a total liquid yield of 46% at 450 °C, with highly selective formation of acetic acid and furfural as the organic liquid. Such selective production of target compounds is advantageous, as it reduces the need for extensive downstream separation compared to the complex bio-oil mixtures typically obtained from conventional biomass pyrolysis. In the present study, the molten salt-assisted sawdust pyrolysis was systemically optimized using a eutectic ZnCl2-KCl-NaCl mixture (44.3:41.9:13.8 mol%), which exhibits a low minimum melting temperature. Experiments were conducted in a staged free-fall pyrolysis reactor that enabled controlled feeding of the salt-biomass feed mixture into the reactor. The setup further allowed efficient screening of reaction conditions, while enabling the collection of sufficient sample quantities for detailed analysis. A Design of Experiments (DoE) approach was applied to evaluate the influence of pyrolysis temperature (340-410°C) and biomass fraction in the feed (5-94 wt%) on product yields and liquid-phase composition. The highest liquid yield (71.2 wt%) was obtained at 375°C using a feed containing 5 wt% biomass and 95 wt% molten salt, which is significantly higher than that obtained in salt-free pyrolysis at otherwise the same reaction conditions (31.9 wt%). This shows the optimization potential of using molten salts in the pyrolysis of biomass, due to the improved heat transfer and slight catalytic role of the molten-salt medium. At high salt loadings, the liquid phase consisted predominantly of water, with a yield of only 4.5 wt% of organic liquid phase products. Under these conditions, the organic fraction was composed almost exclusively of acetic acid and furfural. Increasing the biomass loading in the feed to 94 wt% reduced the total liquid yield; however, the highest organic liquid yield (18.8 wt%) was obtained. In this case, the organic liquid phase had a more complex composition with a broader distribution of organic compounds. These results clearly demonstrate a tradeoff between maximizing total liquid production and selectivity towards specific organic products. A statistical model was developed that was able to describe the product yields as a function of temperature and biomass-to-salt ratio with high accuracy (R2 exceeding 0.98, with most model terms exhibiting p-values below 0.05). The model enables the prediction of optimal operating conditions, depending on whether a high total liquid yield or high selectivity towards specific organic products is targeted.

ABSTRACT. Beer production generates large quantities of by-products, among which brewery spent grains (BSGs), the insoluble solid fraction of grains, are the most abundant, accounting for 85% of total brewing waste [1]. Nearly 36.4 million tons per year of BSGs are produced globally and are typically landfilled, releasing ~513 kg CO2 per ton, or diverted to low-value livestock feed. However, their high lignin (~30% dry weight, dw) and moisture content (>70%) severely limit their shelf life. Despite this, BSGs are rich in structural carbohydrates (e.g., 19% dw cellulose), proteins, and essential mineral elements, making them an attractive feedstock for circular biorefinery approaches. Hydrothermal carbonization (HTC) and liquefaction (HTL) have emerged as promising thermochemical pathways for the valorization of wet lignocellulosic biomasses such as BSGs, as they can be applied to wastes with up to 80–95% moisture, eliminating energy-intensive pre-drying steps [2]. The reactions take place near the critical point of water (TC = 374 °C, PC = 22 MPa), where it exhibits a reduced dielectric constant and behaves similarly to a non-polar solvent. Under subcritical conditions, the elevated ionic product of water (Kw > 10⁻¹⁴) favors ionic reaction mechanisms, whereas radical and non-ionic pathways dominate under supercritical conditions. These processes convert biomasses into a solid fraction (hydrochar), an organic fraction (biocrude), gases, and an aqueous phase (AP), that is considered a secondary by-product. All these fractions hold potential as fuel precursors or as sources of value-added chemicals. Chlorella sp. is a widely investigated microalga for sustainable bio-based applications, including wastewater treatment and the production of biofuels and bioproducts, thanks to its ease of cultivation and high lipid content. In this context, Tarhan et al. demonstrated the successful cultivation of Chlorella minutissima in diluted AP obtained from HTC of olive and orange pomace, achieving high growth rates and efficient nutrients removal [3]. The resulting biomass, enriched in carbohydrates, proteins, and lipids, was suitable for the production of value-added biofuels and chemicals. Following this approach, the present project investigates the optimization of operating conditions for HTC and HTL applied to BSGs, evaluating the yields of hydrochar, subsequently tested as functional carbon material, biocrude, as potential source of added-value chemicals, and gases. Chemical and energetic valorization were carried out on all process streams to evaluate their potential end uses. Particular attention was also devoted to the energetic and nutritional valorization of HTC/HTL by-product, i.e. AP, which is characterized by high organic (~30,000 mg/L) and ammonia content (~500 mg/L). Chlorella sp. was cultivated under mixotrophic conditions in CO2-supplemented tubular systems to simultaneously recover nutrients from diluted AP, enabling further valorization of this process stream and reducing thermochemical treatment costs.

References [1] M. Jakowski et al., Energies 13 (2020) 2058 [2] B. Ciuffi et al., Sci Rep. 11 (2021) 15504 [3] S. Z. Tarhan et al., J. Water Process Eng. 40 (2021) 10178

ABSTRACT. Biomass fast pyrolysis can support decarbonization by replacing fossil fuels, enabling carbon neutral energy and supplying hard to decarbonize sectors with renewable fuels and platform chemicals. During fast pyrolysis, biomass quickly decomposes to biochar, bio-oil and gases through a complex network of series-parallel thermally activated chemical reactions. However, bio-oil is characterized by high viscosity, acidic pH and limited stability. These issues stimulate research activities aimed at improving the design of pyrolytic converters and process conditions to maximize yield/selectivity toward valuable compounds. Fluidized bed reactors represent a favourable environment for biomass fast pyrolysis, due to their robustness, efficient multiphase contact and superior thermal performance. However, particle heating and time-temperature history, biomass and volatile/gas residence times, gas-solids contacting and mixing need to be controlled to drive conversion along the prescribed chemical pathway. A specific concern regards the course of secondary reactions between depolymerization products and char, whose progress may alter the quantity/quality of the bio-oil [1,2]. The relevance of the heterogeneous vapor-char interaction to bio-oil production emphasizes the importance of proper control of char loading establishing during steady operation of a fluidized bed pyrolytic converter, a state variable of the system that must be carefully controlled by proper reactor design and operation [3]. In the present study fluidized bed pyrolysis of biomass is assessed with a focus on operational modes that maximize the yield to depolymerization products: pyrolytic sugars, from decomposition of holocellulose; BTX and substituted monoaromatics, from decomposition of lignin. Accordingly, the reactor design and operating conditions are selected so as to minimize secondary interaction between primary pyrolytic vapours and biochar. Hence, a shallow fluidized bed with overbed feeding of relatively fine biomass particles is assumed (Figure 1). A one-dimensional model including the key features of the fluidized bed pyrolytic converter is developed. The remarkable feature of the model is careful consideration of processes that control the establishment of a steady char loading in the bed, namely, entrainment, elutriation, attrition, and bed drain/regeneration. Primary pyrolytic decomposition of biomass and secondary reactions have been modeled using a semi-detailed reaction scheme. Different kinetic mechanisms are considered for the secondary reactions of the main macropolymers (cellulose, hemicellulose and lignin), including sugars dehydration and fragmentation, demethoxylation and demethylation of guaiacyl-containing structures from lignin depolymerization, uptake and decomposition of aromatic structures on char surface. Model results elucidate the role of heterogeneous secondary reactions, the main composition of bio-oil and the proper management of char loading during fluidized bed pyrolysis, providing criteria for optimal reactor design and operation. References: [1] H. Zhu et., 2021. The Effects of Char and Potassium on the Fast Pyrolysis Behaviors of Biomass in an Infrared-Heating Condition. Energy, 214, 119065. [2] C. Plouffe et al., 2022. The Role of Biochar in the Degradation of Sugars during Fast Pyrolysis of Biomass. J. Anal. Appl. Pyrolysis, 161, 105416. [3] M. Troiano et al., 2022. Fluidized Bed Pyrolysis of Biomass: A Model-Based Assessment of the Relevance of Heterogeneous Secondary Reactions and Char Loading. Energy Fuels, 36, 9660. Figure 1. Fluidized bed pyrolytic converter.

ABSTRACT. Low-temperature pyrolysis of lignocellulosic materials remains insufficiently characterised, despite its critical relevance for long-duration heating scenarios such as concealed smouldering, storage degradation, and sub-critical fire exposures. In contrast to conventional short-duration laboratory experiments, prolonged exposure to moderate temperatures can trigger slow but cumulative physicochemical transformations that significantly affect thermal stability, ignition propensity, and char formation pathways. However, experimental data addressing such extended time scales remain scarce. In this study, beech (Fagus sylvatica L.) and spruce (Picea abies Karst.) wood specimens (150 × 150 × 20 mm³) were subjected to long-term thermal treatment at 150 °C for up to one year in an electrically heated furnace under oxidative atmosphere. Internal temperatures were continuously monitored using embedded thermocouples to ensure stable and homogeneous thermal conditions within the samples. Mass loss was determined at six-week intervals by extracting and weighing all specimens. Three samples were removed for detailed analysis of thermal, chemical, and optical changes at the same intervals. Beech consistently exhibited higher degradation rates than spruce throughout the exposure period, reflecting species-specific differences in chemical composition and thermal sensitivity. Colour measurements revealed an early convergence of both wood species, already after six weeks of storage, particularly with respect to lightness. With increasing exposure time, a gradual darkening was observed. The colour differences between beech and spruce diminished with prolonged heating. Simultaneous thermal analysis demonstrated a continuous depolymerisation of the wood matrix, manifested by a systematic reduction of the pyrolysis onset temperature with increasing storage duration. This behaviour is attributed to oxidative processes, progressive depolymerisation reactions, and the formation of thermolabile structures during long-term heat exposure. FTIR spectroscopy confirmed these trends, showing early hemicellulose deacetylation and cellulose depolymerisation, followed by an increasing dominance of lignin-derived structures in the residual matrix at longer treatment times. Ultimate and proximate analyses revealed a gradual increase in carbon content accompanied by a loss of oxygen and hydrogen, while ash content increased with mass loss. Simultaneously, volatile matter decreased and fixed carbon content increased, indicating a slow transition towards a char-like material. Overall, this study demonstrates that extended low-temperature exposure at 150 °C induces substantial and time-dependent changes in wood chemistry and thermal behaviour, underscoring the importance of duration effects in low-temperature pyrolysis. The results are not only relevant to pyrolysis science and fire safety, but also to a broader range of disciplines concerned with the long-term thermal ageing of wood. In particular, they broaden the understanding of self-heating and spontaneous ignition of biomass, smouldering combustion and deep-seated fire scenarios, and the durability and fire resistance of timber structures exposed to sustained moderate temperatures. Furthermore, the observed progressive heat induced disintegration links the findings to biochar formation and biomass conversion, highlighting the influence of storage and pre-treatment on devolatilisation behaviour and reaction kinetics. Finally, the work has implications for material testing and standardisation, as it demonstrates that short-duration laboratory protocols may not adequately capture time-dependent degradation processes relevant under real long-term thermal exposure conditions.

ABSTRACT. Micro-Raman spectroscopy (μRS) is an established analytical tool enabling facile determination of the structural ordering within carbonaceous materials, including the particulate-matter found in vehicle deposits and environmental matrices. However, if fluorescent species are present within the material under examination, analysis by μRS can be at best complicated and at worst impossible. Common methods to circumvent this issue, such as changing the excitation laser wavelength and/or photobleaching, are not always possible. In this study, we demonstrate pyrolysis under high hydrogen pressures (hydropyrolysis, HyPy) as an effective thermal treatment for the removal of fluorescent species at relatively low temperatures (350 oC), without significantly altering the structure of the parent carbonaceous material. This was illustrated through μRS investigation of a series of six carbon reference samples, whereby, after HyPy, the interference from fluorescence was significantly reduced, whilst the positions, widths and intensity ratios of the diagnostic D and G bands remained largely unchanged. Application of hydropyrolysis to a series of internal diesel injector deposits (IDIDs) enabled a μRS investigation of the physicochemical structure of the deposited carbons for the first time. Moreover, mass spectrometry analysis of the volatile species removed during HyPy of IDIDs where engine failures had occurred suggested that linear polyunsaturated n-C16 and n-C18 alkenes were likely responsible for the fluorescence. As HyPy can be readily applied to a variety of carbonaceous materials, for example, petroleum source rocks contaminated with drilling muds, the approach we describe here represents a general strategy for fluorescence suppression enabling structural investigation of carbons by μRS.

ABSTRACT. The transition to a climate-neutral society will significantly depend on the production of low-cost, low-emission hydrogen (H2), given its role as a sustainable chemical feedstock and energy carrier. Global H2 production is projected to increase from 99.8 Mt in 2024 to 150 Mt by 2030. In this context, methane pyrolysis represents a promising technology for producing low-emission H2 by decomposing any source of renewable or fossil methane into H2 and value-added solid carbon by-product, thereby improving overall process economics. To enable methane pyrolysis at lower temperatures, catalysts are employed to enhance radical formation, which is essential for initiating the methane cracking chemistry and promoting solid carbon growth via acetylene deposition. Methane pyrolysis in carbon-catalyzed systems herein mitigates coking-induced deactivation, a major limitation of metal-based catalysts, where active sites are susceptible to blockage by carbon deposits. Furthermore, fluidization of the carbon catalyst prevents pressure build-up and reactor blockage caused by coke accumulation, commonly encountered in conventional fixed-bed reactors at temperatures exceeding 950 °C. However, the impact of carbon deposition on the carbon structure evolution, potential defluidization, and gas product distribution, particularly the formation of polyaromatic hydrocarbons (PAHs) responsible for equipment fouling and operational downtime, remains unclear. In this work, carbon black Pearls 2000 and SMC2 ordered mesoporous carbon, synthesized through a soft-templating technique on a colloidal silica template, have been thoroughly characterized (N2-physisorption, Raman spectroscopy, CHN/O elemental analysis, XPS, and BF-STEM) to determine the carbon structure prior to and after performing methane pyrolysis in a laboratory scale fluidized-bed reactor. SMC2 exhibited the highest initial H2 yield due to its high specific surface area (1243 m²/g_cat) and initial oxygen content (7.7 wt.%), but gradually deactivated through pore filling and blockages. Carbon black Pearls 2000 demonstrated greater stability, achieving the highest cumulative carbon yield (3.9 g_carbon/g_cat) after 6 hours of reaction at 1000°C. Carbon deposition led to the formation of graphitic domains around the primary carbon black particles, reducing structural heterogeneities and defects in the overall carbon framework. Additionally, with increasing reaction time, the PAH distribution, as identified using both Van den Dool–Kratz and Lee retention indices, shifts from mostly triaromatics, with vinylphenanthrene as the most abundant PAH (0.019 mol.%), to mostly monoaromatics after 6 h of reaction, notably benzene (0.04 mol.%). The identification of naphthalene, acenaphthalene, phenanthrene, pyrene, and their corresponding vinyl-substituted derivatives indicates that the hydrogen-abstraction carbon-addition mechanism (HACA) via consecutive acetylene addition is the dominant pathway for PAH growth during methane pyrolysis. Finally, a two-phase fluidized-bed reactor model was developed, comprising a low density, dominantly gas phase and a high density, dominantly solid phase, coupled to a freeboard section. Transitions between bubbling, turbulent, and fast fluidization were explicitly accounted for using probability density functions on the critical transition velocities. The model integrates homogeneous gas-phase and heterogeneous surface kinetics through the Cantera framework and was validated against the fluidized-bed experiments. Under the assumption of reactor isothermicity, the model will be used to quantify axial heat requirements, providing key insights for the design and scale-up of electrified industrial fluidized-bed reactor systems.

ABSTRACT. Methane pyrolysis via molten media catalysis offers a promising route to low-carbon hydrogen production, concurrently generating valuable solid carbon rather than CO2. The process offers a dynamically refreshed reaction interface where forming carbon is continuously separated and buoyed away by rising gas bubbles, effectively enabling catalyst anti-coking and high reaction throughput. This study reports integrated progress in bubble behavior simulation, solid carbon synthesis, and scale-up of this promising technology. A coupled VOF-DPM model was developed to quantitatively elucidate the bubble dynamics inside the melt, linking hydrodynamics to reactor performance. Building on this foundation, bubbling chemical vapor deposition was systematically employed to control solid carbon morphology. By regulating bubble size and residence time, the selective synthesis of zero-dimensional carbon black, two-dimensional graphene, or three-dimensional graphitic microspheres was achieved, establishing a direct link between fluid dynamics and tailored material architecture. Finally, the technology has been advanced toward pilot-scale implementation, demonstrating continuous hydrogen production and solid carbon co-generation in a scalable reactor configuration. This work provides a cohesive framework from fundamental multiphase modeling to controlled material synthesis and process engineering, underscoring the potential of catalytic molten media systems for combined decarbonization and valuable solid carbon with tailored structure production.

ABSTRACT. Catalytic Methane Pyrolysis (CMP, CH4=2H2+C(s), ∆H°=75 kJ/mol) is receiving increasing attention to produce COx-free hydrogen along with solid carbon (3:1=C:H2 wt.). The latter represents a valuable by-product whose valorization is essential to make the process economically competitive. However, its deposition poses significant challenges to process design and scale-up. In this work, CMP performances of iron-alumina catalyst are experimentally investigated on multiple scales to elucidate mechanisms governing C-growth and deactivation. Furthermore, changes in morphology and reactivity of the resulting iron-carbon materials (i.e. spent catalyst) are assessed as function of operating conditions. Attention is focused on carbon-purity and graphitization-degree (G) with the aim of evaluating the valorization potential in steelmaking as reducing agent for waste iron recovery, to couple hydrogen production with circular iron and carbon management strategies.

Fe-Al2O3 catalysts were prepared by fusion-decomposition method and tested in thermogravimetric balance (TG, 0.004gcat), packed-bed (PBR, 0.75gcat), and fluidized-bed (FBR, 3.50gcat) reactors. The effects of Fe-loading (5-100wt.% Fe), temperature (700-850°C), space velocity (GHSV, 1-100 NL/h/gcat), and inlet CH4 (2.5-95vol.%) on catalytic performances were assessed. Furthermore, fresh, reduced and spent catalysts were characterized, including microscopic (e.g. BET, XRD, RAMAN, SEM) and macroscopic (e.g. particle size and density) properties. Finally, the obtained spent-catalyst was pelletized with waste mill scales (60wt.%FeO + 30wt.%Fe3O4) and used as reducing agent for the carbothermal conversion of the mixed FexOy into metallic-iron (FexOy+yC(s)=xFe0+yCO(g), 750-1500°C, 100vol.%Ar).

Firstly, a screening campaign in TG identified the Fe-Al2O3 catalyst (52wt.%Fe) as the best formulation in terms of activity and C-accumulation capacity. This catalyst was further tested in PBR to explore the effect of operating conditions on CH4 conversion and the corresponding C-load (gC/gcat). In all tests, a rapid decrease in conversion was observed due to carbon deposition, becoming more pronounced at increasing CH4 feed and temperature. Notably, operating at temperature and GHSV below 780°C and 5 NL/h/gcat, respectively, maximized catalyst lifetime and C-load up to 5 gC/gcat, a key requirement for scale-up. A dynamic reactor model was developed in order to predict C and H2 productivity in a wide operating range. However, PBR operations were inherently limited due to C-induced overpressure and clogging. These limitations were overcome in FBR, where bubbling fluidization regime minimized overpressure, enabled longer experiments, favored carbon growth, its discharge and post-characterization. Notably, time on stream and C-load were identified as the primary parameters governing the evolution of spent solid properties. Carbon was deposited either as encapsulating-C or bent and twisted multi-walled carbon nanotubes. The latter were the responsible of the reduction in bulk density (700-45 kg/m3) and enlargement of particle size (150-400 µm) observed with the C-load growth in FBR. Over time, carbon became more ordered as evidenced by XRD (G > 50%) and Raman spectroscopy (IG/ID > 2), while C-purity increased with increasing C/Fe-Al2O3 ratio. When applied to self-reducing agglomerates, spent catalysts (C-load >1.0 gC/gcat) exhibited performances comparable to those of metallurgical-grade coke. Promising reduction degree above 80% were achieved at 1375°C, while iron recovery increased with carbon purity, highlighting the potential synergy between pyrolysis and steelmaking.

ABSTRACT. Coal gasification is a key route for coal clean utilization. As the mainstream technology in modern coal chemical industry, entrained-flow coal gasification features a carbon conversion rate exceeding 99% and broad feedstock adaptability, and is advancing toward independent technology upgrading, feedstock-product diversification, and green low-carbon development [1]. However, the annual output of coal gasification slag in China exceeds 70 million tons, with stockpiling and landfilling as the primary disposal method. The hazardous elements contained pose potential environmental risks, and the utilization rate of gasification slag is below 20% [2]. During gasification, the slag is divided into CS (quenched and collected in the quench chamber, ~60%–80% of total slag, low carbon content) and fine slag (carried out of the gasifier by syngas, ~20%–40% of total slag, high carbon content) [3]. During entrained-flow gasification, to clarify the migration, enrichment and regulation mechanisms of Hg, Cd, Pb, Cr and As in coal gasification slag, this study systematically investigated the leaching and enrichment characteristics of these five elements. Combining FactSage calculations with experimental analysis, it explored their enrichment and speciation in CS and FS, leaching behaviors under different heating rates, and the effect of Fe2O3 on Cr migration. Results showed that weakly volatile Cd was mainly enriched in slag, with a higher proportion in FS, existing as Cd, CdO and CdS. Highly volatile Hg only accounted for 15.6% of the total in slag (10.5% in FS), dominated by HgO with low Hg and HgS contents. Partially volatile Pb was more concentrated in FS, with PbS as the dominant species. As exhibited a similar enrichment pattern to Cd, with 81.9% remaining in slag. Heating rate significantly affected element distribution: rapid heating induced coal particle porosification and larger specific surface area, accelerating Cd and As volatilization while enhancing their adsorption, resulting in higher contents in slag than slow heating. Pb content showed no obvious change due to mineral combination under slow heating versus volatilization-adsorption balance under rapid heating. Under the reductive atmosphere, Fe mainly existed as FeO. Fe2O3 addition affected Fe speciation transformation: 1 wt.% addition increased Fe(Ⅱ) contents, while excessive addition reduced them. Cr primarily existed as highly stable CrO in slag. This study provides theoretical support for heavy metal pollution control of coal gasification slag. References [1] Yifan Zhang, et al. Distribution, occurrence, and leachability of typical heavy metals in coal gasification slag. Science of The Total Environment, 2024, 926, 172011. [2] Tao Wu et al. Characterisation of residual carbon from entrained-bed coal water slurry gasifiers. Fuel, 2007, 86(7–8): 972-982. [3] Wenke Jia. et al, Chongdian Si. Co-combustion of carbon-rich fraction from coal gasification fine slag and biochar: Gas emission, ash sintering, heavy metals evolutions and environmental risk evaluation, Chemical Engineering Journal, 2023, 471, 144312

ABSTRACT. Effective management of plastic waste is an increasingly urgent global challenge, and catalytic pyrolysis of polyolefins offers a promising route to convert waste plastics into high value base chemicals. Despite extensive research, catalyst discovery efforts remain fragmented, with most studies relying on milligram scale tools such as thermogravimetric analysis (TGA) and micropyrolysis GC×GC FID/MS. These approaches often use inconsistent methodologies, limiting comparability across studies and raising uncertainty about the transferability of small scale results to larger scale systems. This work introduces a rational, standardized catalyst screening methodology and provides the first systematic validation of its predictive power across scales. A fast and robust workflow was developed to evaluate catalyst activity, stability, and selectivity for the direct in situ catalytic pyrolysis of LDPE and PP melts. Catalyst activity was quantified using three TGA derived temperature metrics (ΔTonset, ΔTmidpoint, ΔTmax), with ΔTmidpoint identified as the most reliable indicator due to its sensitivity to catalytic effects and its ability to normalize feedstock variability. Catalyst stability was assessed via coke content, reflecting the extent of deactivation through active site blockage. A unique 2D TGA method was established to simultaneously determine catalytic activity (ΔTmidpoint) and stability (coke content) in a single experiment. Plotting these metrics in a 2D scatterplot enabled rapid categorization of catalyst performance (high, moderate, low). Applied to more than 60 heterogeneous catalysts, this approach provided an unprecedented comparative overview of catalyst behavior in polyolefin pyrolysis. For LDPE, ZSM 5 (25) and ASA [40] HPV emerged as the top performing zeolite and non zeolite catalysts, respectively. For PP, USY (40) and ASA [70] HPV were found optimal from the scatterplot. These catalysts reduced polymer degradation temperatures by more than 125 °C relative to thermal pyrolysis. To evaluate transferability to larger-scale reactors, selected catalysts were tested in a gram scale semi batch slurry reactor. Activity (Tonset) and stability (coke content) were quantified and compared to small scale results using regression analysis. A distinction was made between qualitative transferability (preservation of performance ranking; assessed via R² and F tests) and quantitative transferability (accurate prediction of absolute values; assessed via slope and intercept confidence intervals). Qualitative trends for activity, stability, and selectivity were successfully transferred for both LDPE and PP. Quantitative transferability, however, was limited. For LDPE, coke contents were systematically higher at lab scale, likely due to longer residence times. For PP, although coke levels were also higher, the difference was not statistically significant. Selectivity trends, captured via the average carbon number (ACN), were qualitatively transferable for both polymers, while quantitative agreement was confirmed only for PP. This study delivers the first statistically validated framework demonstrating that TGA and micropyrolysis GC×GC FID/MS reliably predict qualitative catalyst behavior in polyolefin pyrolysis. While quantitative predictions remain setup dependent, the methodology enables rapid, comparable, and community wide catalyst assessment, providing a foundation for more coherent catalyst development strategies in plastic waste valorization.

ABSTRACT. Fast pyrolysis (FP) of lignocellulosic biomass notably produces bio-oils rich in oxygenated platform molecules. Catalytic fast pyrolysis (CFP), particularly when zeolite catalysts are used, alters the reaction pathways of conventional FP and promotes the formation of hydrocarbons such as benzene, toluene, ethylbenzene, and xylenes (BTEX). Conventionally, pyrolysis studies rely on bio-oil production in a pyrolysis reactor for each condition, followed by offline chromatographic analysis, often coupled with mass spectrometry. Alternatively, direct infusion high-resolution mass spectrometry (HRMS) can be employed. While powerful, these approaches are time-consuming and may introduce compositional biases due to chemical evolution of bio-oils or reactions with recovery solvents. Moreover, they provide limited insight into the dynamic evolution of pyrolysis reactions.

To accelerate CFP optimization, we developed a high-throughput methodology enabling direct HRMS analysis of pyrolysis products. This approach allows rapid characterization of the molecular species formed during pyrolysis as a function of key parameters such as catalyst type, biomass, and temperature. The methodology was validated using cellulose CFP over Socony Mobil Five (ZSM-5) zeolites, extensively reported in the literature for their upgrading performance in catalytic pyrolysis.

Commercial ZSM-5 catalysts with Si/Al ratios ranging from 0 to 75 and Brønsted acid site densities between 0 and 980 µmol/g were investigated. Avicel® PH-101 cellulose was selected as a model biomass. FP experiments required less than 1 mg of sample and were performed in a glass capillary mounted on a modified direct injection probe (DIP). The probe incorporates a controlled nitrogen flow through the capillary, minimizing residence time of the pyrolysis vapors in the heated zone and efficiently transferring products to an atmospheric pressure chemical ion (APCI) source. Temperatures up to 530 °C were reached. For CFP experiments, a fixed-bed catalyst layer was introduced downstream of the biomass. Product ions were analyzed using a Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS), and the resulting data was processed with Punc'Data software for molecular formula assignment and graphical representation.

Under non-catalytic conditions, anhydro-oligosaccharides such as levoglucosan and cellobiosan, two markers of cellulose pyrolysis, were prominently detected, together with dehydrated and secondary products. In contrast, catalytic conditions strongly suppressed these species and favored the formation of less oxygenated molecules, such as furfural, as well as fully deoxygenated hydrocarbons, including BTEX. Catalyst screening revealed an increase in the relative abundance of hydrocarbons with decreasing Si/Al ratio and increasing Brønsted acid site density. In addition, the degree aromaticity of the products increased with catalyst acidity, in agreement with previously reported trends.[1,2]

These results demonstrate that combining micro-scale CFP with direct HRMS analysis provides a rapid, low-sample and low-catalyst demand, and realistic assessment of CFP performance. This methodology opens new perspectives for high-throughput and in-depth investigation of CFP mechanisms across a wide range of catalysts, operating conditions, and feedstock.

[1] Mihalcik et al., Journal of Analytical and Applied Pyrolysis, 2011, 92, 1 [2] Engtrakul et al., Catalysis Today, 2016, 269

Figure: Schematic overview and results of analysis obtained with the modified DIP methodology, using Punc'data software for comparison of FP and CFP products.

ABSTRACT. The rapid growth of electrical and electronic waste (e-waste) plastics, along with the need for a circular economy and sustainability, poses a significant opportunity for e-waste recycling. Pyrolysis is one such technique that focuses on waste valorization through catalytic pyrolysis of e-waste. In this study, catalytic pyrolysis of e-waste plastics was performed using red mud , an effluent from the alumina industry, as a low-cost and sustainable catalyst. Thermal and catalytic pyrolysis experiments were conducted to analyze the influence of red mud on product yield, composition, and fuel quality. Fresh, regenerated red mud and spent FCC catalyst were compared to assess catalytic activity and stability. A comprehensive characterization of the feedstock, catalyst, and pyrolysis products was carried out using proximate analysis, TGA DSC, XRD, FTIR, GC-MS, and CHNS analysis. The utilization of redmud for catalytic pyrolysis significantly enhanced the cracking reactions, improving the fuel oil quality as compared to thermal pyrolysis. The plastic from e-waste, composed of Acrylonitrile Butadiene Styrene (ABS) and High Impact Polystyrene (HIPS), underwent catalytic pyrolysis at 550 °C with 15 wt% of redmud as a catalyst in a bench-scale reactor. It generated approx. 75 wt% aromatic hydrocarbon-based oil. It was observed that the pyrolysis oil properties closely match those of gasoline. The utilization of regenerated redmud resulted in similar oil yields. The pyrolysis oil can be suitably blended with conventional fuels for engine applications. Overall, the study demonstrates the potential of redmud as an effective catalyst for e-waste plastic pyrolysis, offering an environmentally sustainable route of utilizing two major waste streams – one for fuel production and another for catalyst synthesis

ABSTRACT. With the urgent need to valorise over 80% of global plastic waste polluting the environment, many strategies have been developed to address this challenge, with one of the most promising routes with long-term solutions being catalytic pyrolysis of plastic waste into useful hydrocarbons and chemicals. Thermal cracking of polyethylene requires high activation energy and produces more waxy products. The use of catalysts in the pyrolysis of plastics reduces this activation energy, yielding lower molecular weight hydrocarbons and providing selectivity for target products. However, the rapid deactivation of these catalysts, caused by carbon coke deposits common to the most expensive synthetic zeolite-based catalysts, and the loss of activity during regeneration processes, have motivated research into cheaper alternatives, such as clay-based catalysts. Developing a low-cost catalyst with efficient activity for the degradation of plastic into value-added hydrocarbons is key. Clay catalysts are low-cost and naturally occurring materials that can be modified to increase activity through acid activation. In this study, seven (7) commercially available acid-activated clays were investigated for the effects of their acidity and textural properties on the degradation of PE plastic into value-added hydrocarbons and chemicals using thermogravimetry analysis. Acid-montmorillonite clay with unknown acidity details from two sources was used. The catalysts were characterised for their acidity using temperature-programmed desorption of ammonia on active acid sites (NH₃-TPD), their Si/Al ratio by SEM-EDX, and cationic exchange capacity was also determined. The textural properties of the surfaces and pore volumes of the catalysts were determined using nitrogen gas adsorption/desorption. The catalytic degradation of the PE over a clay-based catalyst was carried out using a thermal analyser with a catalyst-to-plastic ratio of 1:1 and 1:10. of The result showed that the clay-based catalysts' total acidity ranges from 0.26 to 0.53 mmol NH₃/g catalyst, exhibiting four distinct acidity levels: weak acidity (WA), medium acidity (MA), strong acidity (SA) and very strong acidity (VSA), which were categorised based on their desorption temperature ranges: 150–250°C, 250–350°C, 350–500°C and above 500°C, respectively. Analysis of the results for the temperature shift, which is the difference between peak degradation temperatures of the catalysed and uncatalysed PE mass loss, shows that K10 exhibited the highest temperature shift of 87℃ and 56℃ at a catalyst-to-plastic ratio of 1:1 and 1:10, respectively and performed better than zeolite based catalyst at catalyst to plastic ratio of 1:1.The greater the temperature shift, the better the catalyst effectiveness to reduce the energy requirement for degradation. Clay catalyst acidities, surface area, and mesoporosity correlate with the most effective catalyst for PE degradation. The clay catalyst's medium and very strong acidities contribute significantly to the shift in temperature during catalytic degradation, with correlation coefficient R² values of 0.90 and 0.84 for catalyst-to-plastic ratios of 1:1 and 1:10, respectively, resulting in low coke yield.

ABSTRACT. Benzene, toluene, and xylenes (collectively known as BTX) are essential feedstocks in the manufacture of a wide range of chemical products. Currently, practically all BTX is produced from fossil-carbon sources in the petrochemical industry. However, recent advances have been made on BTX production from waste plastics, offering a promising method for the valorization of hard-to-recycle plastic waste. In such process, waste plastics are first pyrolyzed to crack the plastic chains into a complex mix of hydrocarbon vapor stream ( generally represented mainly by C5-C12 paraffins) and precipitate out inorganic impurities as solids. The produced vapor is subsequently upgraded to BTX in a second reactor through catalytic aromatization, typically with a zeolite catalyst. Light olefin and paraffin gases are formed as byproducts. This study addresses the catalytic aromatization of plastic-derived hydrocarbons in a lab-scale fluidized bed reactor using a HZSM-5 catalyst and model hydrocarbons as the feed (i.e., hexane, dodecane, or 1-hexene). The hydrocarbon feed was diluted with N2 before entering the reactor. BTX reaction products were recovered by a series of condensation steps followed by biodiesel scrubbing. the remaining gaseous product was collected for compositional analysis and to determine the mass balance. The effect of reactor operating conditions (temperature, feed concentration, contact time) on the BTX and gaseous product yields was systematically evaluated with hexane as the feed. at temperatures between 500 - 600 °C and molar N2 to feedstock ratios of 1.2 to 3.6. An increase in temperature significantly improved the total BTX yield, from 10 wt% at 500 °C to 21 wt% at 600 °C. Furthermore, operating temperature had a considerable effect on the BTX product distribution. Toluene was the most abundantly formed aromatic product, with 48% selectivity at 600 °C. Benzene yield increased at higher temperatures, from ~1.0 wt% to ~5.3 wt%. Xylene selectivity was mostly independent of temperature, remaining within ~20–28%. Feed dilution experiments at 550 °C strongly affected the BTX formation. Increasing molar nitrogen to hydrocarbon ratio 1.2 to 3.6 resulted in a lower total BTX yield, with especially less toluene (~9.2 vs. ~6.8 wt%) and xylenes (~6.9 vs. ~3.8 wt%) formed. The benzene yield remained relatively equal (~2.5–2.8 wt%), indicating a higher thermal stability. Overall, increased feed dilution suppressed secondary aromatization and alkylation by reducing effective residence time. Experiments with 1-hexene or dodecane as alternative hydrocarbon feeds highlighted the role of feed structure on BTX formation. The olefinic feed strongly enhanced BTX formation, increasing toluene yield to ~16.0 wt%, compared to ~7.8 wt% with hexane as the feed under otherwise the same reaction conditions. Xylene and benzene yields reached ~10.7 wt% and ~5.3 wt%, respectively. In contrast, dodecane produced lower BTX yields and higher fractions of light non-aromatic hydrocarbons. The presented experimental study provides insight into the optimized conditions for BTX formation from plastic-derived feeds, aiding reactor design and scale-up towards a maximized BTX yield or selective production of targeted BTX compounds.

ABSTRACT. The European Union promotes the cascaded use of wood in new products to support a carbon sink functionality and the non-energy valorisation of biomass. Thermally modified wood (TMW) building products, such as cladding and decking, are increasingly utilised in modern architecture. Being produced using mild pyrolysis, TMW is chemical-free, which facilitates its reuse in bioeconomy applications. The cascaded use of TMW in urban landscapes contributes to more sustainable building practices and alleviates pressure on forest ecosystems where virgin wood is harvested. Despite rapid growth in TMW volumes over the last decade, this resource remains largely unmapped and unmanaged in our cities.

In this study, the TMW sector in Europe is illuminated and mapped. Light is shed on the details of the pyrolytic modification process, selection of raw material species, by-products generated, standing volumes of TMW in key markets and the potential of end-of-life TMW materials. Through networking with key partners, recent developments in the field including policy considerations are also described.

The findings paint a picture of a rapidly maturing TMW industry with great market appeal for both environmental and technical performance reasons. The presented results include specific evidence from preliminary and on-going research work. The conclusions reached are that TMW materials (both end-of-life and production by-products) are of high-value in the bioeconomy and their uniqueness greatly enhances the potential for the cascaded use of wood.

ABSTRACT. Millions of paddle and tennis balls are used worldwide each year. These balls are nearly identical in composition and have a very short lifespan, resulting in a significant amount of waste. Additionally, they are primarily made of rubber coated with textile felt, making them more difficult to manage as waste. Similar to end-of-life tires, the main conventional disposal methods for these balls are energy recovery and material recovery. However, incorporating this type of waste into more circular economy strategies is essential, and chemical recycling methods, such as pyrolysis, are necessary to achieve this goal. Pyrolysis retains the carbon embedded in end-of-life products, making it available for new processes and reducing the consumption of fossil resources. Based on this, the present study evaluates the thermochemical recycling of end-of-life padel balls (ELPBs) via pyrolysis. To this end, thermogravimetric analysis (TGA) was performed, and the Distributed Activation Energy Model (DAEM) was employed to analyze the kinetics of the rubber and textile felt. Additionally, a laboratory-scale fixed bed reactor at the third technology readiness level (TRL-3) was employed to assess the impact of temperature (350–600°C) on the yields and primary characteristics of the resulting products. There are no detailed studies on the kinetics of this particular waste; and therefore there are no mathematical expressions describing conversion (X) and reaction rate (dX/dt) with respect to temperature (T). Kinetics is essential to incorporate into both particle and reactor models, i.e. when designing and scaling up the process. In addition, the activation energy (Ea) distribution of the rubber was found to fluctuate between 170 and 300 kJ/mol, suggesting the presence of complex, multistep reactions, including parallel, competitive, and consecutive reactions. All of the experimental kinetic curves were satisfactorily reproduced, and the deviations between the experimental and predicted data revealed the soundness and robustness of the DAEM application to these complex samples. On the other hand, the proof-of-concept trials demonstrate the technical feasibility of pyrolyzing these wastes, paving the way not only to determine the effectiveness of this chemical recycling process, but also to take it to a higher level of maturity. In this sense, the pyro-oil yield stabilizes at 45.0 wt% at 400 °C, and contains up to 5 wt% of limonene, which is associated with rubber depolymerization. Monocyclic aromatic hydrocarbons (BTEX) were also detected, increasing as the pyrolysis temperature increased. The solid fraction was found to stabilize at 400 °C, reaching a yield above 50 wt%. It is composed mainly of Ca (18 wt%), followed by Al (5.0 wt%), S (2.2 wt%), Ba (2.5 wt%), Zn (2.25 wt%), and Mg (1.25 wt%). Meanwhile, the gas fraction is predominantly rich in H₂ (20 vol%), CH₄ (14 vol%), and C₄ (14 vol%). These data are expected to provide the fundamental knowledge necessary to assess the technical feasibility of pyrolysis for thermochemical recycling of ELPBs.

ABSTRACT. The current linear economic model, which relies heavily on fossil-based resources, has caused a continuous increase in plastic waste generation worldwide. This growing amount of plastic waste creates serious environmental challenges and highlights the need for efficient recycling strategies to produce secondary raw materials and support the transition to a circular economy. In this context, chemical recycling technologies have received increasing attention because they allow the recovery of valuable chemical compounds from plastic waste streams that are not suitable for conventional mechanical recycling. Among chemical recycling options, pyrolysis is considered one of the most promising technologies. It involves the thermal degradation of polymers under inert conditions, typically at temperatures between 400 and 600 °C. Depending on the operating conditions and the type of plastic, pyrolysis can produce a liquid composed of oils and/or waxes, which can be further upgraded into fuels or chemical feedstocks, as well as gaseous and solid products. However, the large-scale application of conventional endothermic pyrolysis (CEP) is still limited by poor heat transfer efficiency. In most reactors, heat is supplied externally through the reactor walls or heating media. As reactor size increases, this surface-based heat transfer becomes inefficient, while the energy demand remains distributed throughout the entire reactor volume. This mismatch represents a major limitation for process scalability and energy efficiency. Thermo-Oxidative degradation (TOD) has been proposed as an alternative route to overcome some of these limitations. In this approach, small and controlled amounts of air or oxygen are introduced into the reactor. This promotes exothermic oxidation reactions that generate heat in situ, partially compensating for the endothermic cracking reactions of the polymer. As a result, thermal homogeneity is improved and the need for external energy input is reduced. Although this strategy has been successfully applied to biomass feedstocks, its application to plastic waste remains relatively unexplored. In this work, the TOD of polystyrene waste (PSW) was investigated using thermogravimetric analysis under varying oxygen concentrations to evaluate its thermal behavior. Complementary experiments were conducted in a laboratory-scale fixed-bed reactor. The objective was to assess energy consumption, product distribution, and product quality, and to evaluate the potential of oxygen-assisted process intensification while preserving selectivity toward high-value liquid products. Thermogravimetric results showed a reduction in the main decomposition temperature of PSW from 475 to 450 °C with the introduction of low oxygen concentrations. Reactor experiments demonstrated a 16% reduction in external energy demand, attributed to a 50 °C decrease in operating temperature under TOD conditions compared to CEP. At an oxygen concentration of 5% O₂/N₂, higher overall conversion yields were achieved, with only a minor reduction (below 4%) in the liquid fraction and a marginal increase in gas production. Liquid characterization revealed a significantly higher styrene content under TOD conditions (57.6 wt%) compared to CEP (39.2 wt%). These results demonstrate that TOD is a promising strategy for process intensification in plastic chemical recycling, offering improved energy efficiency, enhanced product quality and greater sustainability, thereby contributing to the development of scalable and circular solutions for plastic waste management.

ABSTRACT. Pyrolysis oil, obtained through the pyrolysis of waste polymeric materials, is utilized as a feedstock for both alternative petroleum based-fuels and recycled polymers. This process is regarded as a crucial technological pathway toward achieving a circular economy. GCxGC-Time-of-Flight mass spectrometry (TOFMS) is widely used for characterizing pyrolysis oils; however, it requires a long measurement time. In contrast, the direct MS methods, including FD (Field Desorption)-TOFMS and blank tube FI (Field Ionization)-TOFMS, have shorter measurement times. Analysis time can also be shortened by combining the Kendrick Mass Defect (KMD) analysis. In this study, we investigated the complementary analysis of pyrolysis oils using the above three methods. Pyrolysis oils are produced by adjusting the blending ratio of polyethylene (PE) and polypropylene (PP). For GCxGC-TOFMS, JMS-T2000GC (JEOL Ltd.) was combined with INSIGHT-Thermal modulator (SepSolve Analytical). For the FD-TOFMS and blank tube FI-TOFMS, the samples were introduced directly without the use of GC separation. The molecular ions of a complex mixture of hydrocarbons were observed in mass spectra. By using KMD analysis, the distribution of the number of carbons and DBEs can be visualized in the KMD plots. As a result, it was possible to confirm the difference in pyro-oil due to the PE/PP blend ratio using all three methods. GCxGC-TOFMS enables the elucidation of structural information due to its high separation capability. The FD-TOFMS and the blank tube FI-TOFMS facilitate the confirmation of the hydrocarbon profile in a short time. By combining these methods, a complementary analysis can be efficiently performed.

ABSTRACT. The accumulation of waste polypropylene (PP) presents a critical environmental challenge but also offers a significant opportunity to produce high-value petrochemical feedstocks. This study investigates a novel two-stage upcycling process integrating pyrolysis with non-thermal plasma (NTP) catalysis to maximize the yield of single-ring aromatic hydrocarbons (BTEX). We systematically evaluated the catalytic performance of microporous Y-zeolite versus shape-selective β-zeolite, followed by an optimization of β-zeolite supported metal promoters (Ni, Ga, Mo, Zn). Experimental results demonstrate that β-zeolite outperforms Y-zeolite due to its unique pore topology, which favors the diffusion of aromatic intermediates while suppressing coke formation. The introduction of NTP (40 W) at 500 °C significantly enhanced reaction efficiency. Among the metal-modified catalysts, the Ga/β-zeolite exhibited superior performance, achieving a record BTEX yield of 45.6%. This enhancement is attributed to a "triple synergy": (1) high-energy plasma species activate stable alkane intermediates; (2) Ga species (likely GaO) specifically promote the rate-determining dehydrogenation-cyclization steps; and (3) the β-zeolite pore structure provides shape-selective confinement for aromatization. Additionally, Ga and Zn promoters were found to maintain substantial gas yields alongside high aromatic conversion, indicating a balanced product distribution. This work provides a mechanistic understanding of plasma-catalyst interactions and proposes a highly efficient route for circular plastic economy.

ABSTRACT. Microwave-assisted chemical recycling represents an attractive approach for the low-temperature conversion of polyolefin waste; however, the influence of catalyst properties under microwave irradiation remains insufficiently understood. This study investigates the low-temperature microwave-assisted decomposition of high-density polyethylene (HDPE) using activated carbon (AC) as both a microwave absorber and catalyst, with particular emphasis on the role of water inherently present in the carbon structure. Two types of activated carbon were examined: untreated activated carbon containing naturally adsorbed moisture (AC-W, ~16 wt.%) and thermally dried activated carbon (AC-D, ~1.5 wt.%). Experiments were performed at 260 °C under a mildly oxidising atmosphere (3 vol.% O2 in N2), enabling HDPE conversion at significantly lower temperatures than those required in conventional pyrolysis processes. Product yields and compositions were analysed as a function of residence time using gravimetric methods, gas chromatography (GC), and GC–MS. Although similar overall HDPE conversion levels were achieved with both absorbers, substantial differences in product distribution were observed. The use of AC-W resulted in increased wax formation, with wax yields reaching approximately 25 wt.% and consisting predominantly of long-chain n-alkanes. In contrast, AC-D strongly favoured gas-phase products, particularly hydrogen and light hydrocarbons, indicating more extensive polymer chain scission and secondary dehydrogenation reactions. Hydrogen yields were markedly higher for AC-D, while AC-W exhibited elevated formation of CO and CO2. The findings demonstrate that moisture in activated carbon plays a decisive mechanistic role rather than acting as an inert component during microwave-assisted HDPE degradation. Control of the water content in activated carbon offers an effective strategy for tuning product selectivity between hydrogen-rich gases and hydrocarbon waxes, providing new opportunities for the targeted and energy-efficient chemical recycling of plastic waste.

Funding: The work was supported by the OP JAK project "INOVO!!!", No. CZ.02.01.01/00/23_021/0008588 supported by the Ministry of Education, Youth and Sports and co-financed by the European Union. Experimental results were accomplished by using Large Research Infrastructure ENREGAT supported by the Ministry of Education, Youth and Sports of the Czech Republic under projects no. LM2018098 and LM2023056.

ABSTRACT. Plastics have become an essential product of the current lifestyle, because of their excellent properties and versatility. Consequently, annual plastic waste world generation has increased and will continue to increase in the future. For this reason, the management or recovery of this waste is indispensable. Chemical recycling, and especially pyrolysis, is a promising option to recover high value-added products from plastics. The use of catalyst is necessary to obtain a narrow product distribution and increase the selectivity of valuable products. ZSM5 zeolite has demonstrated a great selectivity to olefins and aromatics [1,2,3].

In this work, the pyrolysis and in-line catalytic cracking of a HDPE over a ZSM5 zeolite catalyst has been studied, which was agglomerated with alumina and bentonite. The plastics pyrolysis step has been carried out in a conical spouted bed reactor, and the volatile stream has been fed in line to a fixed bed catalytic reactor. Specifically, the effect of catalytic bed temperature (400-550 ºC) and catalyst space-time (2-15 gcatalyst min gplastic) on the distribution of product yields at zero-time stream have been studied. In addition, the influence of the residence time has been assessed, by varying nitrogen flow rate in the 2-8.5 L/min range. The determination of product distribution has been carried out by gas chromatography.

Light olefins (predominantly propylene and butene) have been obtained as the primary products. By increasing temperature and space-time time, the cracking reactions of heavier fractions, as well as secondary olefin condensation reactions, are favoured. Therefore, the yield of light olefins and BTX increase with a maximum of 86 % and 6.4 %, respectively at 550 ºC and 15 gcatalyst min gplastic. In contrast, nitrogen flow rate has an opposite effect on light olefins and BTX yields. In other words, decreasing the nitrogen flow rate reduces the yield of light olefins because secondary reactions are favoured. As a result, the yield of BTX and light alkanes increases up to a maximum of 9.6 % at 2 L/min (Figure 1).

1Soni, V.K..; Singh, G.; Vijayan; B.K..; Chopra, A.; Kapur, G.S.; Ramakumar, S.S.V. Energy Fuels 2021, 35, 12763-12808. 2Artetxe, M.; Lopez, G.; Amutio, M.; Elordi, G.; Bilbao, J.; Olazar, M. Chem. Eng. J. 2012, 207, 27-34. 3Lopez, G.; Artetxe, M.; Amutio; M.;Bilbao, J.; Olazar, M. Renewable Sustainable Energy Rev. 2017, 73, 346-368.

ABSTRACT. Polystyrene is among the most widely used plastics due to its numerous advantageous properties, but its large-scale consumption generates substantial waste and significant management challenges. Pyrolysis offers a promising alternative to landfilling and incineration, which provide only partial solutions. This work focuses on the pyrolysis of polystyrene blended with road asphalt waste to evaluate possible synergistic effects, improve liquid yields, and maximize the recovery of BTEX compounds. Experiments were conducted in a semi-batch reactor equipped with a reflux system under atmospheric nitrogen at 500°C. The resulting liquid products were characterized using FTIR and GC–MS/FID, while gaseous products were analyzed with a µ-GC.

Co-pyrolysis was found to be effective in increasing the liquid yield for all mass ratios tested, compared with the yield obtained from polystyrene alone. The strongest synergistic effect occurred at a PS/asphalt mass ratio of 67/33, producing a liquid yield of 93%, corresponding to a 9.3% increase relative to pure PS. Increasing the proportion of asphalt beyond this point reduced the observed synergy.

Analysis of the liquid fraction showed styrene to be the dominant product in all experiments. The asphalt content exhibited a notable influence on the distribution of BTEX compounds: an increase of asphalt content from 18% to 33% leads to an increase of styrene yield in the liquid products from 80% to 84% before it decreases to around 74% when asphalt content was 67%.This decrease in styrene yield accompanied by an increase in ethylbenzene suggests a catalytic contribution from the mineral fraction, particularly when asphalt is present in excess.

These results highlight the potential of PS/asphalt co-pyrolysis as a promising approach for the valorization of polystyrene waste, enabling its conversion into value-added products. In particular, the recovery of styrene offers opportunities for closed-loop recycling, as it can be reused directly as a monomer in new PS production.

ABSTRACT. Due to global population growth, the production and consumption of waste plastics have steadily increased, making recycling a critical challenge. Meanwhile, biomass is a carbon-neutral resource that can be utilized as a clean fuel through appropriate treatment. This study evaluated the potential for waste resource circulation by comparing the pyrolysis characteristics of polyethylene (PE) and woody biomass under both single and co-pyrolysis conditions. Experiments were conducted in a lab-scale fluidized-bed reactor at 400, 600, and 800 ℃ under a nitrogen atmosphere with a superficial gas velocity to minimum fluidization velocity ratio (ug/umf) of 1.5. The produced gases were analyzed using NDIR and GC-FID, while the pyrolysis oils were characterized by GC–MS. Concentrations of H2, CO, CH4, CO2, and C2–C3 hydrocarbons in the pyrolysis gas were quantified, and oil compositions were determined by integrating the mass spectrometric peak areas of individual compounds. Co-pyrolysis was carried out using a 1:1 mixture of PE and woody biomass. Biomass exhibited a maximum oil yield at 600 ℃, whereas PE predominantly produced wax rather than oil at the same temperature. Biomass-derived oils consisted mainly of phenolic and ester compounds, with phenolic concentrations increasing as the temperature rose. This study demonstrates the potential of converting waste plastics and biomass into pyrolysis oils as a viable pathway for waste recycling and sustainable resource circulation.

ABSTRACT. The versatility of plastics, characterized by their high chemical and mechanical resistance, has positioned them as essential components in material science. Consequently, global production has increased exponentially over the last three decades, as documented by the Organisation for Economic Co-operation and Development (OECD) [1]. However, this widespread use has led to the accumulation of persistent waste that resists complete degradation, eventually fragmenting into microplastics (MPs), ranging from 5 mm to 1 µm, and nanoplastics (NPs), with sizes lower than 1 µm. These particles pose a severe environmental threat due to their mobility across ecosystems, such as seawater. In response to the urgent need for standardized determination methods, this study presents the development of an analytical methodology based on pyrolysis coupled with gas chromatography-mass spectrometry (Py-GC/MS) for the simultaneous determination of twelve MNPs, including ten listed in the Commission Delegated Decision (UE) 2024/1441 [2] (polyethylene, polypropylene, polystyrene, among others), and four micro/nanobioplastics (MNBPs) (polylactic acid, polycaprolactone, polybutylene adipate terephthalate and poly 3-hydroxybutyrate) within a total analysis time of 26 minutes. While the goal is environmental monitoring, the primary objective of this current work is the design and rigorous performance evaluation of the method using controlled aqueous matrices to ensure its efficacy. For this purpose, a sequential filtration with 1.00, 0.45 and 0.10 µm cellulose nitrate filters was carried out to fractionate the sample and assess the particle size distribution, as Py-GC-MS analysis does not differentiate by size. Simulated seawater samples were employed during method development to ensure reliable results. Moreover, a comparison between full scan and Selected Ion Monitoring (SIM) was carried out as acquisition mode, observing that SIM mode was more selective and sensitive than full scan, improving the reliability during the identification of the polymers. The proposed method was validated through linearity, precision and recovery evaluation ranging from 0.005 to 0.1 mg. Finally, this method was evaluated analysing ten seawater samples from Mediterranean Sea (samples were selected according to their closeness to populated areas). The proposed analytical method enabled the simultaneous identification of MPs of polyethylene (5.12-21.31 mg·m-3) and polyvinyl chloride (0.85-5.83 mg·m-3) in all the seawater samples, as well as polylactic acid (1.38-3.75 mg·m-3) in two of them. In addition, NPs of polyvinyl chloride and polylactic acid were detected. This methodology offers a robust, high-throughput alternative to traditional microspectroscopy techniques, establishing a validated framework for future application in complex seawater samples.

This publication is part of project PID2022-137122OB-I00, funded by MICIU/AEI/10.13039/501100011033/ and ERDF, EU. Encarnación López Rodríguez acknowledge grant FPU21/00858, funded by MICIU/AEI/10.13039/501100011033 and ESF+. Jesús Marín Sáez acknowledges the Andalusian government, the Counselling of University, Investigation and Innovation (CUII) and European Social Fund plus (Andalusia ESF+ 2021–2027) for financial support (POST_2024_00151).

[1] OECD (2024), Policy Scenarios for Eliminating Plastic Pollution by 2040, OECD Publishing, Paris, https://doi.org/10.1787/76400890-en. [2] European Commission, 2024. Commission Delegated Decision (EU) 2024/1441 of 11 March 2024 supplementing Directive (EU) 020/2184 of the European Parliament and of the Council by laying down a methodology to measure microplastics in water intended for human consumption.

ABSTRACT. With the aim of valorizing the underutilized resource to explore new horizons in the energetic field, this work investigates the potential of Parapenaeus longirostris shrimp, an abundant species in the Mediterranean Sea, as a valuable source of chitin for the synthesis of high-energetic polysaccharide, namely nitrochitosane. And compares the impact of conventional extraction of chitin through acid hydrolysis and a DES- based extraction using lactic acid/choline chloride as a deep eutectic solvent, on the targeted products. Chitin was extracted from the shrimp shells using both methods, and high-quality chitosan (DDA% > 92%) was obtained through deacetylation process. Subsequently, nitrochitosan was synthesized from the chitosan derived from both extraction methods as well as a commercial source, resulting in three distinct types of nitrochitosan: NCS-Con, NCS-DES, and NCS-C. This article presents comprehensive assessments of the studied inert and energetic polysaccharides, including physiochemical properties (1.531 ≤ DCT ≤ 1.558, 1.531, 1.501 ≤ DCS ≤ 1.511, 1.698 ≤ DNCS ≤ 1.710), structural and morphological features, thermal behavior, thermal and mechanical sensitivities (110.8 °C ≤ Ti ≤ 117.1 °C, Is = 15 J, Fs > 360), combustion parameters and estimation of energetic performances (248 s ≤Isp≤ 251 s, 7865 ≤D≤ 7882). In addition, thermokinetic study was conducted to determine the energy of activation of each (74 kJ/mol ≤ Ea1ststep ≤ 86 kJ/mol, 117 kJ/mol ≤Ea2ndstep≤153 kJ/mol) among many other revelations. Figure 1: Graphical abstract.

ABSTRACT. An in-depth understanding of co-pyrolysis interaction mechanisms is essential for efficient conversion of raw materials and optimizing the regulation of products. Herein, the interaction between enzymatically hydrolyzed lignin (EHL) and waste tires (WT) during co-pyrolysis was investigated using a novel strategy which combines principal component analysis (PCA) and characterization analysis (e.g., FT-ICR-MS, GC–MS, EPR, and so on). Results indicated that cooperative interactions were observed during the co-pyrolysis of EHL and WT, resulting in measured activation energy lower than theoretical calculation. PCA indicated that co-pyrolysis interaction pri marily occurred at 345–470 ◦C and was controlled by WT. The contribution of co-pyrolysis to the activation energy and radical spin concentration was most significant with WT blending ratio of 25 %, while the contri bution to the bio-oil yield was most significant when the ratio was 50 %. The mechanism analysis indicated that radical-mediated interactions are the key factors influencing the formation of pyrolysis products. Co-pyrolysis improved the bio-oil quality. When a small amount of WT was blended, the co-pyrolysis was manifested as WT-generated hydrocarbon radicals attacking the chemical sites of EHL-derived aromatic rings to form aromatic compounds with fatty structures. When a large amount of WT was blended, it was manifested as sufficient hy drocarbon radicals promoting the demethylation and dehydration of phenolic compounds to form aromatic compounds through hydrogen transfer. Notably, the aromatics content increased significantly from 0.64 % to 18.67 % when WT blending ratio was 75 %. The findings reveal the co-pyrolysis interaction mechanism from the perspective of free radicals and provide a theoretical basis for the targeted regulation of pyrolysis products.

ABSTRACT. Polystyrene (PS) is well-known as one of the most used commodity plastic; however, the recycling rate of PS is accounted only to 7% globally. Mechanical recycling overwhelmingly dominates current polystyrene reprocessing, while chemical recycling, particularly thermal pyrolysis provides a great potential for closing the material loop and tackling contaminated or mixed waste streams. Polystyrene has a backbone of saturated carbon-carbon (C–C) bonds similar to polyolefins, but its key distinguishing feature is the presence of pendant aromatic (phenyl) rings attached to every other carbon atom in the backbone. This structural motif creates relatively weaker benzylic C–H and C–C bonds adjacent to the aromatic rings, which are more reactive and easier to cleave during depolymerization compared to the stronger, more inert aliphatic C–C and C–H bonds in polyolefins. Additionally, the benzylic position stabilizes radicals formed during bond scission thus lowering the energy required for bond cleavage and making depolymerization by thermal or catalytic means more efficient . The mechanism of thermal PS pyrolysis and process peculiarities were extensively studied in small scale. However, the upscaling always requires additional optimization in order to obtain higher target product yield. When it comes to upscaling, use of an efficient reactor and optimized reaction conditions are critical factors. Conical spouted bed reactor (CSBR) configuration is known to be particularly effective when high selectivity and productivity are the primary objectives. Among the advantages of a CSBR are (i) short residence times, thereby minimizing secondary reactions, (ii) cyclic movement of the sand, accordingly avoiding defluidization and (iii) excellent mass and heat transfer. In the current research the influence of different parameters was studied for PS thermal pyrolysis in CSBR and evaluated using statistical modeling. The data analysis revealed temperature and feeding rate as crucial reaction parameters largely defining the styrene yield. The developed model allowed to predict the optimal conditions for maximization of the target product yield which were further successfully validated using real post-consumer waste PS as feedstock.

ABSTRACT. To address key challenges in the pyrolysis of retired fluorine (F)-containing photovoltaic (PV) module backsheets, namely unclear F migration mechanisms, insufficient experiment-simulation coupling, and ambiguous F distribution/hydrogen fluoride formation pathways, this study combines experiments with ReaxFF molecular dynamics simulations. Pyrolysis characteristics and F transformation behaviors of polyvinyl fluoride (PVF), PV backsheets, and PV modules containing backsheets were systematically investigated. Experimentally, thermogravimetric analysis (TGA), high-temperature combustion hydrolysis coupled with anion selective electrode (ISE), alkali fusion-ISE, and gas chromatography-mass spectrometry quantified F distribution among gas, liquid, and solid products at 400-600℃. Results showed more F retained in tar than gas, with characteristic fluorinated compounds identified. Parallel ReaxFF molecular dynamics simulations based on a 12,050-atom PVF model were conducted to elucidate atomic-scale C-F cleavage mechanisms, HF formation pathways, and competitive F reaction dynamics. The simulation results showed qualitative agreement with TGA experiments. F was preferentially released as HF in gas, while most F radicals from C-F bond cleavage recombined with carbon to form complex fluorohydrocarbons in tar. Fluorine critically promoted radical-driven cyclization of fluorinated carbon chains through electronic effects, promoting free radical generation, intramolecular bonding, and small-to-large ring conversion. Distinct temperature-dependent F behaviors were observed during backsheet pyrolysis. At low temperatures, F predominantly accumulated in the tar, whereas at high temperatures, 90.10% of F migrated to gas. Ethylene vinyl acetate synergistically affected F transformation. HF formation was dominated by F• capturing H atoms, and the largest detected fluorinated fragment (C1060H548F252) retained 12.6% of the total F, influencing char graphitization through cross-linked structures. Overall, this study provides integrated experimental-simulation evidence that clarifies F transformation pathways during PV backsheet pyrolysis, and offers guidance for development of low-F-emission recycling processes.

ABSTRACT. The development of predictive models for plastic pyrolysis is required to achieve a mechanistic understanding of the underlying phenomena and, in turn, to facilitate and accelerate the deployment of pyrolysis-based recycling technologies through improved process design and operation. However, the strong variability of real plastic waste streams and the complexity of degradation mechanisms still represent major challenges for reliable model formulation, validation, and extension. In this work, an existing modelling framework is assessed and supported through a set of well-characterized experiments designed to probe degradation pathways at increasing levels of complexity and to identify directions for further model refinement. A well-defined virgin polymer system is selected as a starting point to ensure consistency between experimental observations and model assumptions before progressively moving toward more complex reaction environments. Low-density polyethylene (LDPE) virgin pellets were selected as a reference material to generate high-quality experimental data suitable for model validation and development. Thermogravimetric analysis was first performed under an inert nitrogen atmosphere to investigate the intrinsic thermal degradation behaviour of LDPE, primarily associated with primary decomposition reactions. Experiments were conducted up to 800 °C with a heating rate of 20 °C/min, representative of fast and flash pyrolysis conditions, providing insight into the main degradation stages and overall conversion behaviour. Pyrolysis experiments were subsequently carried out in a laboratory-scale batch setup capable of reproducing reaction environments of increasing complexity and enabling the development of secondary chemistry. Both single-stage and double-stage pyrolysis configurations were investigated. In the single-stage configuration, pyrolysis was performed in a single reactor operated at 500 °C, whereas in the double-stage configuration a second reactor operated at 800 °C was placed downstream of the first one to promote further thermal cracking and secondary reactions. Both reactors were continuously fed with nitrogen at 300 mL/min to ensure inert conditions and to transport pyrolysis products through the system. The reaction section was followed by a separation unit, where condensable vapours were collected using a cryogenic condensation system based on a liquid CO2-ethanol mixture, while permanent gases were collected in Tedlar® bags and analysed by microGC to determine their volumetric composition. Solid, liquid, and gaseous products were quantified at the end of each experiment to calculate product yields, and samples were collected for further characterization. The resulting dataset, including thermal degradation profiles, product yields, and gas compositions under different pyrolysis configurations, is used to validate and further develop a semi-detailed kinetic model for LDPE thermochemical recycling based on a functional-group approach. The model explicitly accounts for primary degradation reactions as well as secondary reaction pathways and is applied to reproduce mass-loss profiles and product speciation under static and dynamic conditions at moderate to high temperatures. This study represents a first step toward a systematic, model-driven description of plastic pyrolysis, with the long-term goal of extending the approach to increasingly complex plastic mixtures and real waste-derived feedstocks.

ABSTRACT. Pyrolysis offers a practical route for large-scale waste plastic treatment, particularly for polyolefins where other approaches do not offer success. However, diverse product distributions from polyolefin pyrolysis are typically observed where complex interplay between chemical kinetics and mass transfer exists. In this work, we demonstrate the use of dimensionless Damköhler numbers to guide the modulation of chemical kinetics–mass transfer coupling in both neat and catalytic polyolefin pyrolysis for tuning product distributions. High-density polyethylene (HDPE) is selected as an illustrative example, and its pyrolysis was conducted at pressures between near vacuum and 1 atm in a microreactor to vary the mass transfer environments, with USY zeolite catalysts used to alter chemical kinetics. Our experiments revealed that neat pyrolysis at near-vacuum conditions gave a product distribution closer to that obtained from the kinetic-limited regime, representing primary products that readily escape from the reaction zone. Increasing pressure and adding catalysts both promoted HDPE conversion, caused by decelerated species outflow and increased reaction rate in the gas phase, respectively, facilitating continued decomposition of the primary products. Two dimensionless Damköhler numbers, one for the melt polymer phase and the other for the headspace directly above the vapor–liquid interface, are defined to characterize the competition between mass transfer and continued decomposition of a species. It is shown that the first Damköhler number is small for all experimental conditions studied (see Figure), suggesting fast escape of the products from the melt polymer phase. On the other hand, the second Damköhler number suggests that higher system pressure or the presence of a catalyst favors continued decomposition in the headspace. This Damköhler number analysis accurately predicts the experimental findings. Such a dimensionless analysis provides insights into future pyrolysis process optimization or novel catalyst design to manipulate chemical kinetics–mass transfer coupling in polyolefin pyrolysis for achieving desired product distributions, advancing plastic recycling technologies for full circularity.

ABSTRACT. Polyolefin plastics primarily polyethylene (PE) and polypropylene (PP) are the most abundant components of plastic waste globally, driving a significant portion of the world's pollution crisis. Waste plastic is one of the most promising resources for fuel production. We can convert waste plastic into valuable energy resources. Thermochemical conversion technologies primarily combustion, gasification and pyrolysis are recognized globally as advanced cleaner alternatives to more than traditional landfilling waste management. Pyrolysis offers significant advantages by turning waste into valuable resources (char, oils, gas) through heat in an oxygen-free environment. Reducing landfill dependency, lowering greenhouse gas emissions compared to incineration, enabling energy recovery and supporting the circular economy.The reported is that chemically, pyrolytic oil is constituted by paraffin, olefins, and aromatics. Moreover, the relevant physical properties (density, viscosity, pH value etc) and the heating value of pyrolytic oil are like those of diesel. In this study, 1:1 mixture of waste polyethylene and waste polypropylene was pyrolyzed at a reaction temperature of 550 °C using auger system with a maximum capacity of 15 kg/hr. Additionally, CaO and talc 2.5 wt.% was added to reduce the chlorine content in the pyrolytic oil. The proximately and ultimate analysis results of the feedstocks are described in Table 1. An auger system is a device utilizing a rotating helical screw blade enclosed in a tube to transport feedstocks. The experimental apparatus consisted of a stainless-steel tube with an electric furnace and a temperature controller (as shown in Fig. 1). A staged oil recovery system was applied to capture high boiling point wax and low boiling point oil together. Nitrogen gas (N2) was introduced during the pyrolysis experiment. The yield of pyrolytic oil was about 51 wt.%. The recovered pyrolytic oil was properties analyzed by GC-MS(Gas Chromatography - Mass Spectrometry), Combustion-IC(Ion Chromatography) and kinetic vicosity. In GC-MS analysis, obtained pyrolytic oil components mainly consisted of Naphtha (as shown in Fig. 2). Combustion-IC analysis results showed that the chlorine concentration inside the pyrolytic oil without additives was 34.9 ppm. When 2.5 wt.% of CaO and talc were added, the chlorine concentration in the pyrolytic oil was confirmed to be 21.2 ppm. It was confirmed that 32.9 wt.% of chlorine in the pyrolytic oil was removed through the addition of additives. At this time, The kinematic viscosity of pyrolytic oil was about 1.0 cSt.

ABSTRACT. Hierarchical ZSM-5 catalysts were synthesized via a one-pot route at crystallization temperatures between 120 and 220 °C and applied to microwave-assisted catalytic pyrolysis of plastic waste at 500 °C under continuous operation. All materials preserved the MFI framework, while crystallization temperature strongly tuned secondary porosity and acidity; for example, the mesopore volume increased from 0.075 cm³ g⁻¹ (T-220) to 0.157 cm³ g⁻¹ (T-180). Catalyst lifetime was quantified using a TGA-defined gasoline fraction (≤200 ℃) of the condensed liquid as a product-relevant activity descriptor. The gasoline fraction decreased monotonically with time-on-stream for all catalysts, but with markedly different decay rates. T-120 showed the highest stability, maintaining gasoline yields above 70% for 6.83 h and still achieving 63.55% after 11 h, whereas catalysts synthesized at higher crystallization temperatures deactivated much faster, with T-200 and T-220 crossing the 70% threshold after only 2.36 and 3.16 h, respectively. Time-resolved product analysis further revealed that deactivation is accompanied by a strong decline in aromatic upgrading (e.g., BTX dropping from 38.3 to 4.0 wt% for T-140) and an increase in less-upgraded aliphatic fractions. These results demonstrate that controlling crystallization temperature offers a simple, scalable means to balance hierarchical porosity and acidity, thereby extending catalyst lifetime and improving liquid-fuel quality in plastic waste valorization.

ABSTRACT. The resource utilization of waste polyolefin plastics is expected to be achieved through upgrading and reconstruction processes, but the primary scientific challenge lies in the development of efficient and cost-effective catalysts. In this paper, we present Ni nanoparticles supported on Nb2O5 with tunable acid sites (Ni/Nb2O5-T) as noble-metal-free catalysts for the upcycling of waste plastics. These catalysts efficiently facilitate a one-pot, solvent-free hydrogenolysis-isomerization of waste plastics, converting them into aromatic-free, highly branched alkane aviation fuels under mild conditions. Notably, the bifunctional Ni/Nb2O5-400 catalyst, characterized by highly dispersed metallic Ni sites and strong Brønsted acid sites, promotes key reactions such as hydrogenation/dehydrogenation, skeletal rearrangements, and β-scission of linear low-density polyethylene. This process achieves 100% conversion with a yield of over 80% for liquid products at 250 °C and 3 MPa H₂ for 4 hours. The carbon distribution of the resulting liquid fuels primarily ranges from C6 to C18, with 71% consisting of isoparaffins, highlighting them as promising candidates for aviation fuels. Additionally, the Ni/Nb2O5-400 catalyst exhibits versatile activity, delivering high yields of highly branched alkane aviation fuels through the chemical upcycling of various types of waste polyolefin plastics. A techno-economic analysis further confirms that this Ni-catalyzed plastic-to-fuel process offers significant economic advantages, underscoring its potential for industrial-scale implementation.

ABSTRACT. The rising volume of postconsumer plastic waste (PCW) necessitates recycling strategies capable of processing highly contaminated post-consumer feedstocks. direct feedstock-catalyst contact, or in-situ catalytic pyrolysis is a promising route to selectively convert PCW into valuable chemicals such as light olefins, naphtha or BTX fractions. However, catalyst deactivation caused by feedstock impurities (i.e., polymer sorting errors, (in)organic additives and use phase contaminants) remains a key challenge that needs to be addressed. From an in-house developed two-dimensional thermogravimetric analysis (2D-TGA) method, two promising catalysts are taken as model catalysts: an MFI zeolite catalyst and an amorphous silica alumina catalyst. Upon reaction with PCW feedstocks, both catalysts show high degrees of deactivation. In this work, a hydrothermal pretreatment strategy for sorted PCW waste mitigates deactivation from multilayer polymer contaminants including polyamides (PA) and polyethylene terephthalate (PET) as well as food residues and selected additives. Pretreatment using biphasic water/n-butanol mixtures, rather than water alone, significantly reduces the presence of catalyst-poisoning species due to hydrolysis/alcoholysis pathways. Removal of these impurities prior to catalytic conversion preserves acid catalyst activity and enhances process robustness. This impurity-focused pretreatment enables the direct catalytic valorisation of low-value post-consumer polyolefins and represents an important step toward scalable, resilient plastic recycling.

ABSTRACT. The rapid accumulation of mixed textile waste—dominated by cotton (CT) and polyester (PET)—poses a growing environmental challenge because blended fibers are difficult to recycle and PET is resistant to biological degradation. Pyrolysis is an attractive valorization route; however, conventional textile-derived oils often contain abundant oxygenates and exhibit poor storage stability, limiting their direct use as transportation fuels. Here, we propose a two-stage “waste-to-jet” strategy that deliberately converts CT–PET mixtures into cycloalkane-rich fuel components suitable for blending into Sustainable Aviation Fuel (SAF).

In stage 1, CT and PET are converted by microwave-assisted catalytic co-pyrolysis using a cost-effective Korean loess (KL)/ZSM-5 hybrid catalyst. The KL component provides mineral-derived acidity and hierarchical porosity, while ZSM-5 promotes shape-selective aromatization. The hybrid catalyst enhances cross-interactions between the oxygen-rich CT fraction and hydrogen-rich PET fraction, suppressing highly oxygenated products (e.g., acids, carbonyls, and furans) and steering carbon toward monocyclic aromatics (BTX-range compounds). Rather than treating these aromatics as an endpoint, we position the resulting aromatic-enriched oil as a tailored intermediate for jet-fuel upgrading.

In stage 2, the BTX-rich stream is targeted for hydrotreatment (hydrogenation and hydrodeoxygenation) to saturate aromatic rings and remove residual oxygen, producing cycloalkanes such as cyclohexane and methylcyclohexane. Cycloalkanes are valuable for aviation applications because they provide high volumetric energy density and thermal stability, supporting the performance requirements specified in ASTM D7566 for aviation turbine fuels. Preliminary assessments indicate that the in situ deoxygenation and aromatic selectivity achieved during catalytic co-pyrolysis can reduce the heteroatom burden of the feed and, consequently, lower hydrogen demand during downstream upgrading. Overall, this work highlights a scalable pathway that couples natural mineral-based catalysts with microwave-driven processing to transform mixed textile waste into refinery-compatible precursors for drop-in SAF, linking waste mitigation with circular carbon utilization.

ABSTRACT. In this work, we present a systematic screening of 46 acidic zeolite catalysts with varying pore dimensionality for the catalytic pyrolysis of polystyrene. Initial activity trends were established through thermogravimetric analysis and subsequently validated at larger scale in a bench-scale semi-batch reactor to assess the effects of catalyst activity and stability on product formation. Comprehensive product distribution analysis studied by GC-MS/FID and GC-VUV methods, combined with detailed acidity characterization, enabled the establishment of clear structure–performance relationships. The results demonstrate that external acid sites govern the initiation of polystyrene degradation, while internal porosity and acid site distribution strongly influence product selectivity and coke formation. Zeolites with narrow pore channels exhibited slower deactivation and reduced coke yields, whereas three-dimensional frameworks promoted rapid coke accumulation due to their complex intersecting pore architectures.

ABSTRACT. Steam cracking is one of the key technologies for the production of light olefins, especially ethylene and propylene. The conventional feedstock for steam cracking is refinery-derived naphtha, characterized by a narrow boiling point range and strict quality specifications. In recent years, several studies have investigated the compatibility of sustainable sourced hydrocarbon fractions with existing technologies. This work focuses on the feasibility of heavy hydrocarbon fractions obtained from plastic waste pyrolysis as alternative feedstocks in bench-scale experiments. Waste plastic pyrolysis results hydrocarbons with high carbon numbers, as well, which can be characterized by high final boiling point, complex compositions and contaminants. Beside feedstock composition, operating parameters such as reaction temperature and steam-to-hydrocarbon ratio play a crucial role in product properties and coke formation. In this work, the effect of main process parameters using waste plastic derived hydrocarbons as steam cracker feedstock to the product yield and properties had been investigated.

ABSTRACT. The rapid growth of plastic production has intensified environmental challenges, while conventional management routes such as recycling or incineration remain constrained by costs, emissions, and limited circularity. In this context, pyrolysis emerges as a key enabling step within multi-stage thermochemical routes for plastic conversion. This contribution critically assesses the role of pyrolysis as the primary platform for hydrogen-oriented valorization, highlighting its ability to convert diverse polymeric feedstocks into intermediate gas and liquid streams. The effects of operating parameters, including temperature, residence time, heating rate and particle size on product distribution are analyzed. Downstream upgrading strategies, such as gasification, catalytic and thermal reforming, water-gas shift reactions, and plasma-assisted processes, are described, emphasizing their synergistic contribution to enhancing hydrogen yield and purity. Thermal and catalytic pathways are comparatively analyzed, together with emerging integrated configurations. Finally, recent techno-economic and life-cycle assessments are examined to evaluate scalability, energy efficiency, and environmental performance. Overall, pyrolysis is positioned as a pivotal gateway step for sustainable hydrogen production from plastic waste within circular economy frameworks. [1] Journal of Analytical and Applied Pyrolysis 193 (2026) 107480

ABSTRACT. The work presents a catalytic study focused on the valorization of the gas fraction generated during the pyrolysis of non-recyclable plastic waste. It encompasses both the development of catalytic materials and the optimization of a two-step process aimed at improving the gas composition toward a hydrogen-rich stream. The catalysts were synthesized through a simple and scalable solvent-less approach. The most promising material, a ternary Co2O3/B/Carbon system, not only exhibited remarkable catalytic activity but also displayed magnetic properties that facilitate its separation during the insitu pyrolysis stage. The study identifies and discusses the roles of the Co-related metallic components supported on carbon, as well as the contribution of the minor boron species. Overall, this work provides clear evidence of the potential of a two-step catalytic configuration for the valorization of plastic residues that currently accumulate in landfills.

ABSTRACT. Multilayer plastic-containing packaging represents difficult-to-recycle waste streams. An example is the polyethylene (PE)–aluminum films present, e.g., in Tetra Pak® beverage cartons. These days, only paper is recycled from this waste. In this research, we studied the pyrolysis of beverage cartons under various conditions to produce hydrocarbon-rich feedstock suitable for the steam cracking process. This enabled increasing the valorization potential of this waste in line with the circular economy.

During the conference, the results of this ongoing research will be presented. The following aspects will be discussed during the presentation: 1) The mass balance of the process, including the yield of gas, liquid, and solid product 2) The dependence of oil properties and composition on pyrolysis conditions 3) The oil quality comparison with the specifications for steam cracking feedstock

ABSTRACT. Tire pyrolysis oil (TPO) is one of the main products resulting from the pyrolysis of end-of-life tires (ELTs). Recently, this fraction has begun to play an important role as an alternative to petroleum-derived fractions, reducing the use of fossil resources in the petrochemical industry. This is because of the significant deployment of various pyrolysis technologies for both ELTs and plastic waste, which have reached the highest technology readiness level (TRL-9). Depending on the type of tire pyrolyze (passenger car or truck tire) and the conditions employed in the pyrolysis reactors, the TPO can contain significant amounts of limonene. Additionally, single aromatics such as benzene, toluene, ethylbenzene and xylenes (BTEX) are also commonly found it in the TPO. This study used a fully instrumented, laboratory-scale, TRL-4 packed distillation column equipped with a 1250 mm long wire mesh packing (approximately 40 theoretical plates) and a DN25 column diameter. The system features a 2 L removable glass flask equipped with electric heating and magnetic stirring. The distillation column was used to assess the effect of reflux ratio (0, 1 and 2) and different temperature cuts on limonene recovery. All tests were conducted using a TPO derived from an industrial-scale TRL-9 pyrolysis plant containing 3.6 wt% limonene and 5.2 wt% BTEX. Four temperature cuts were evaluated by setting the low cut at <150 °C and the high cut at >180 °C, while varying the low-middle and high-middle cuts between 150 °C and 180 °C, to maximize limonene recovery. The experimental results revealed a yield of 11 wt% for the high-middle cut (160-180 °C), which had the highest limonene concentration (26.4 wt%) among all the experiments performed. This cut accounted for over 80% of limonene recovery when the distillation column operated with a reflux ratio of 2. Under these conditions, the low-cut yield (<150 °C) was 14.1 wt%, resulting in a BTEX concentration of 31.6 wt%. Limonene is a valuable compound in the petrochemical industry with many uses. It is widely used as a solvent, cleaning agent, and dispersing agent. It is also a key ingredient in various pesticides and repellents. It can also be used as a precursor for plasticizers and adhesives. Similarly, BTEX is a valuable commodity with diverse applications in the plastics and polymers industry. The results of this study serve as a foundation for designing large-scale purification plants to meet the growing global demand for carbon-based chemicals and derivatives while sustainably utilizing waste.

ABSTRACT. In this study, the pyrolysis of multilayer plastics was investigated in a bench-scale fluidized bed reactor with the aim of optimising the process conditions for the recovery of valuable products, especially caprolactam. The effects of temperature, residence time, catalyst share and the of steam as carrier gas, were systematically studied. The influence of these parameters on product distribution and caprolactam yield was evaluated. The results show that process conditions have a significant impact on both the overall conversion and the selectivity towards target compounds. The findings provide practical insights for improving the efficiency of multilayer plastic recycling through pyrolysis and for supporting the development of more sustainable chemical recycling routes.

ABSTRACT. This study assesses the catalytic steam cracking of plastic wastes as a valorization route for producing valuable chemicals and fuels. The work evaluates the application of a fountain confined conical spouted bed reactor (FCSBR) for the steam cracking of high-density polyethylene (HDPE) at 600–700 °C, while systematically examining the performance of three commercial fluid catalytic cracking (FCC) catalysts under these reaction conditions. The FCSBR represents an efficient configuration for plastic conversion, minimizing defluidization problems associated with fused polymers and ensuring stable operation at elevated temperatures [1]. The FCC catalysts differ in origin and pretreatment, enabling evaluation of the influence of catalyst condition on product distribution. One catalyst was collected from the purge stream at the outlet of the FCC unit regenerator at Petronor (Spain). The remaining two catalysts were supplied by Albemarle: one was used without pretreatment (fresh), whereas the other underwent severe steaming at 816 °C for 8 h following a procedure reported elsewhere [2]. This treatment alters catalyst composition through dealumination and modifies structural properties such as surface area, potentially affecting cracking pathways and selectivity toward light olefins and aromatics. HDPE pellets (4 mm) were supplied by Dow Chemical Company (Tarragona, Spain) with an average molecular weight of 46.2 kg mol⁻¹, polydispersity of 2.89, and density of 940 kg m⁻³. The higher heating value (43 kJ kg⁻¹) was measured using a isoperibolic bomb calorimetry (Parr 1356). Experiments were conducted at 600, 650, and 700 °C with a bed containing 100 g of FCC catalyst (90–150 μm). Steam was fed at 2 mL min⁻¹, ⁻¹, equivalent to 2.49 NL min⁻¹ of steam. Products were analyzed online using an Agilent 7890 GC through a line maintained at 250 °C. Products were grouped into six fractions: CO and CO₂, hydrogen, light alkenes (C1–C4), light olefins (C2–C4), BTX (benzene, toluene, and xylenes), and a remaining liquid fraction composed of C5+ hydrocarbons (excluding BTX). The FCC catalysts exhibited high selectivity toward gasoline-range liquids and light olefins. At 600 °C, the liquid fraction predominated for both the steamed catalyst and the Petronor catalyst (36.2 and 38.2 wt%, respectively); however, increasing temperature shifted the primary product toward light olefins, reaching about 40 wt% at 650 °C. ). Although the higher acidity of the fresh catalyst would suggest greater BTX yields, it showed the highest production at 600 °C (9.2 wt%) but lower yields at 700 °C (14.7 wt%) than the other catalysts due to dealumination at elevated temperatures and the resulting reduction in active sites. In addition to typical cracking products, CO and CO₂ were detected, reaching maximum yields of approximately 3 wt% at 700 °C for all catalysts, likely promoted by steam reforming reactions. [1] M. Mollick, L. Santamaria, Z. Wang, P. Comendador, M. Artetxe, E. Fernandez, M. Olazar, G. Lopez. Particuology, 103, pp 206-216, 2025. [2] T.F. Degnan, G.K. Chitnis, P.H. Schipper, Micropor. Mesopor. Mater. 35–36, pp 245-252, 2000.

ABSTRACT. The increasing consumption of plastics has intensified challenges in plastic waste management, particularly for polyvinyl chloride (PVC), which contains a high chlorine content that leads to hydrogen chloride (HCl) release and toxic by-product formation during thermal treatment. Consequently, effective dechlorination pretreatment is essential for safe energy recovery and material valorization. Hydrothermal carbonization (HTC) has attracted attention as an alternative technology capable of dechlorinating PVC under subcritical water conditions, primarily through dehydrochlorination reactions that become pronounced above approximately 220 °C. However, when PVC is treated alone, sufficiently high dechlorination efficiency generally requires elevated reaction temperatures, limiting process efficiency and practical applicability.

To overcome these limitations, co-hydrothermal carbonization (co-HTC) with biomass has been proposed, as biomass-derived organic compounds can promote dechlorination via substitution reactions under hydrothermal conditions. In this study, spent coffee grounds (CG) were employed as a co-feedstock due to their high organic content and favorable fuel properties. Co-HTC experiments were conducted in a 1 L batch reactor using PVC and CG mixed at mass ratios of 3:7 and 5:5, alongside single-feedstock HTC for comparison. Approximately 50 g of feedstock was reacted with distilled water at 180–280 °C for 0.5–1.5 h. After reaction, hydrochar was recovered and analyzed to evaluate hydrochar yield, chlorine content, and alkali and alkaline earth metal (AAEM) concentrations.

In PVC-alone HTC, dechlorination was initiated at temperatures above 220 °C; however, the solid fuel chlorine standard (≤2 wt%) was not satisfied under most conditions. In contrast, co-HTC of PVC with CG resulted in a significant reduction in chlorine content at comparable temperatures, with higher CG mixing ratios leading to enhanced dechlorination efficiency (DE). Notably, experimentally obtained DE values exceeded theoretically calculated values based solely on the dilution effect, clearly demonstrating a synergistic effect arising from material interactions during co-HTC. This synergistic behavior was most pronounced at intermediate temperatures, whereas thermochemical reactions became dominant at higher temperatures.

Additionally, experimental hydrochar yields under co-HTC conditions were consistently lower than calculated values, indicating non-additive behavior beyond simple dilution. The simultaneous reduction in hydrochar yield and enhancement in DE suggest that synergistic interactions—primarily substitution reactions on C–Cl bonds and HCl-induced acid catalysis—played a key role in promoting PVC dechlorination while facilitating AAEM removal. As a result, the co-HTC process produced hydrochar with reduced chlorine and AAEM contents, thereby improving solid recovered fuel (SRF) quality. Overall, these findings demonstrate that co-HTC of PVC and spent coffee grounds is an effective material recycling and recovery strategy for simultaneously valorizing chlorine-containing plastic waste and biomass through synergistic reaction pathways.

ABSTRACT. The performance of biomass pyrolysis is strongly governed by mineral matter and catalytic species, which influence thermal degradation pathways, product distribution, and solid carbon stabilisation. This study investigates the use of BECCS-derived ash as an in-situ catalytic additive during biomass pyrolysis, with a focus on enhancing biochar yield, carbon retention, and overall pyrolysis process efficiency.

Co-pyrolysis experiments were conducted using agricultural residues blended with BECCS ash under controlled slow pyrolysis conditions. The presence of ash significantly altered devolatilisation behaviour and secondary char-forming reactions, promoting enhanced solid carbon formation. Compared to conventional pyrolysis, ash-assisted pyrolysis increased biochar carbon retention by 20.1–27.9% and produced biochars with carbon contents of 63.1–84.3% (dry ash-free basis). Thermochemical analysis indicates that alkaline and alkaline-earth metal species in the ash catalysed cracking, tar reforming, and gas-solid interactions, shifting reaction pathways toward increased char formation and reduced volatile carbon losses.

In addition to improving solid product yields, the ash-assisted pyrolysis process demonstrated favourable impacts on reactor mass balance and process performance, with implications for optimising residence time, heating rate, and additive loading. The resulting biochars exhibited properties suitable for long-term carbon storage and downstream applications.

These results demonstrate that BECCS-derived ash can function as a low-cost, circular catalytic material for process-intensified biomass pyrolysis, linking waste mineral streams with enhanced thermochemical conversion performance. This work highlights a new route for coupling carbon capture residues with advanced pyrolysis systems to improve biochar production efficiency and carbon stabilisation in thermal biomass conversion.

ABSTRACT. Biomass derived materials are emerging as sustainable and cost effective platforms for water remediation. In this work, bamboo based biochars (BBs) were produced via fast and slow pyrolysis at temperatures ranging from 300 to 1000 °C under N₂ and CO₂ atmospheres and subsequently evaluated as carriers for laccase immobilisation. The resulting enzyme functionalised BBs were integrated into a packed column flow system to investigate their performance in removing organic pollutants through combined adsorption and catalytic oxidation. The removal efficiency was found to depend strongly on both the concentration of carbon centred persistent free radicals (PFRs) within the BB (10¹⁶–10¹⁹ spins g⁻¹, quantified by electron paramagnetic resonance, EPR) and the redox activity of immobilised laccase. Experiments conducted with and without oxygen purging demonstrated the crucial role of dissolved oxygen in generating reactive oxygen species (ROS), particularly hydroxyl radicals (•OH), and in promoting laccase mediated oxidation in the absence of chemical mediators. Using a newly developed BB packed flow system, we quantified the removal efficiency (R%) of organic polluntans under controlled oxygenation conditions. The results reveal a synergistic mechanism in which PFR driven radical generation and laccase redox catalysis act cooperatively, enabling an advanced oxidation process (AOP) without the need for external chemical oxidants. This work highlights the potential of engineered bamboo based biochars as multifunctional catalytic materials for sustainable water treatment and points toward the development of greener AOP technologies with reduced operational costs and environmental impact.

References: 1. O. Ginoble Pandoli, "Permanent free radicals in bamboo biochar-based flow bed reactor: a sustainable solution for dye degradation via adsorption and radical oxidation", Catal. Sci. Technol., 15, 20, (2025): 10.1039/D5CY00632E. 2. O. G. Pandoli, "Pivotal Contribution of EPR-Characterized Persistent Free Radicals in the Methylene Blue Removal by a Bamboo-Based Biochar-Packed Column Flow System", ChemCatChem, 16, 21, (2024): https://doi.org/10.1002/cctc.202401042. 3. S. Riva et al., Biocatalysis with Laccases: An Updated Overview Catalysts 2021, 11, 26. https://doi.org/10.3390/

ABSTRACT. Coffee grounds are largely available under-valorised biowaste stream with significant potential for conversion into functional carbonaceous materials through pyrolysis. Among the products of thermal decomposition, biochar is particularly attractive due to its structure and surface chemistry that can be tailored by tuning process conditions, enabling their use as functional building blocks in advanced materials. Coffee-derived biochar was obtained by pyrolysis at 550 °C in a tubular furnace with a heating rate of 15 °C/min to preserve the surface textures. Coffee biochar was integrated into a silicon elastomer matrix via solvent-free route. Commercial polydimethylsiloxane (PDMS) and its curing agent were mixed with the biochar to prepare three formulations: neat PDMS (0 wt% filler) and composites containing 10 wt% and 20 wt% biochar. The mixtures were cast on glass and cured for 24 h at room temperature to obtain free-standing films. This solvent-free approach was selected to minimise potential alteration of the char surface and to demonstrate the feasibility of translating pyrolysis-derived solids into functional composite materials with minimal post-processing. Gas-material interactions were investigated using dynamic vapour sorption as an analytical screening tool. Measurements were performed at 40 °C under stepwise relative partial pressures (p/p0 = 0.2, 0.4, 0.6, 0.8) for N2, H2, CO2, and CH4, enabling consistent comparisons across gases and compositions. This protocol provides insight into gas-dependent uptake behaviour and into how biochar loading influences gas-material interactions in a rubbery polymer matrix, thereby informing subsequent separation-relevant evaluation. Overall, the study highlights pyrolysis as an enabling technology for transforming coffee waste into a functional solid that can be directly leveraged in composite materials. The work illustrates a practical route from biowaste to new materials and supports the potential of coffee-biochar as building blocks for composites-based membranes.

ABSTRACT. Sustainable management of biowaste plays a crucial role in reducing environmental impacts, improving soil quality, and supporting long-term carbon sequestration. Pelletized rhizomes of Miscanthus × giganteus were processed into biochar using a pilot scale continuous pyrolysis unit within the ENREGAT large research infrastructure. The pyrolysis was carried out at 600 °C with a feed rate of 2.1 kg h⁻¹ and a residence time of 1 h under an argon atmosphere. The produced biochar was subsequently applied to soil, illustrating a closed-loop approach. ENREGAT provides a comprehensive platform for both fundamental and applied research focused on waste valorization and resource recovery. In the area of thermochemical processes, this includes conventional and microwave reactors operating at different scales, supported by a strong analytical background allowing detailed characterization of input materials, process performance, and resulting products. In addition, ENREGAT serves as a unique base for research on combustion, anaerobic digestion, catalytic, sorption, and photocatalytic gas cleaning and membrane-based separation. ENREGAT operates under a free open access policy, promoting research with high industrial relevance. To date, more than 600 projects from universities and institutions within the Academies of Sciences worldwide have been granted open access status.

Acknowledgment: Financial support from MEYS, project No. LM2023056 is acknowledged.

ABSTRACT. This study presents the first reported preparation and evaluation of bonechar and activated bonechar derived from waste animal bones for the adsorption of xylene from waste gas streams. To enhance their adsorption performance, the activated bonechar were chemically activated using K₂CO₃, H₃PO₄ and KOH under optimised microwave-assisted pyrolysis conditions. Microwave pyrolysis of waste animal bones, performed without chemical activation, showed no clear correlation between the applied microwave power levels and the development of the porous structure. The materials exhibited meso- and macroporous structure, but no significant microporosity. Activated bonechar with K₂CO₃ shows improved porous structure made by micro-, meso- and macropores. The meso- and macropores dominate the total pore volume, significantly contributing to the increased surface area. The treatment with H₃PO₄ and KOH resulted in the formation of meso- and macroporous activated bonechar structures with no micropores. In the case of H₃PO₄, the acid reacts with the inorganic salt matrix, disrupting the original layered arrangement of hydroxyapatite and CaCO₃. This reaction yields randomly deposited CaHPO₄ particles within the disintegrated matrix, forming predominantly mesopores. Similarly, activation with KOH induces structural modifications within the hydroxyapatite matrix, reducing the surface area and total pore volume. Of all the textural and structural parameters and surface functional groups investigated, the key factors influencing xylene adsorption performance were identified as a combination of total pore volume, specific surface area, fixed carbon content, graphitization and metal cation content. These results highlight the potential of activated bonechar as a sustainable, low-cost adsorbent for removing VOCs, contributing to the fulfilling of demands of circular economy.

Funding: The work was supported by the OP JAK project "INOVO!!!", No. CZ.02.01.01/00/23_021/0008588 supported by the Ministry of Education, Youth and Sports and co-financed by the European Union. Experimental results were accomplished by using Large Research Infrastructure ENREGAT supported by the Ministry of Education, Youth and Sports of the Czech Republic under projects no. LM2018098 and LM2023056.

ABSTRACT. Water treatment represent one of the key applications of biochar. Nowadays, it is generally limited to the removal of pollutants such as organic and inorganic contaminants. Nevertheless, the biochar surface tailoring can open the way to advance applications including bacterial removal. In this work, we functionalized the biochar through carbothermal reduction process creating a iron tailored material for promoting the bacterial removal. The antibacterial activity of biochar was evaluated against two common waterborne pathogenic bacteria, E. coli and S. aureus, using an initial bacterial concentration of approximately log 3 CFU/mL, two biochar dosages (1.5 g/L and 2.0 g/L) were tested. Preliminary assessments were conducted on solid agar media, where the highest inhibition zones were observed at a dosage of 2.0 g/L, measuring (20.5 ± 6.3) mm for E. coli and (15.2 ± 1.0) mm for S. aureus. Furthermore, antibacterial efficacy was examined in liquid suspension. The results demonstrated complete reduction (100%) of E. coli and a 98% reduction of S. aureus at the 2.0 g/L dosage. This work represent a first approach of potabilization of water using biochar as antimicrobial agent.

ABSTRACT. Pyrolysis of biogenic waste streams is an important strategy for producing sustainable materials and managing circular resources. Livestock bones are a particularly interesting pyrolysis feedstock due to their distinct organic-mineral composition, which is dominated by collagen and calcium phosphate phases. This unique composition can produce mineral-rich chars with potential environmental functionality, as well as hydrocarbon-rich bio-oil and gaseous products due to the presence of fat. This study examines reindeer (Rangifer tarandus fennicus) bones, an underutilised regional waste resource in Nordic regions, through controlled slow pyrolysis to assess the impact of pyrolysis temperature on product yields, material properties, and potential valorisation pathways, particularly focusing on pyrolytic char as a functional material for wastewater treatment. Pyrolysis experiments were carried out using a laboratory fixed-bed reactor in an inert atmosphere at three different temperatures: 350, 500, and 650 °C for 30 minutes. The products yield (solid, liquid, and gas) was quantified by applying mass balance calculations across the system. The compositions of liquid and gaseous products were analysed using gas chromatography/mass spectrometry and micro gas chromatography. Characterisation methods used on chars included Fourier transform infrared (FT-IR) spectroscopy, suspension pH, point of zero charge (PZC) measurements, and elemental analysis. Preliminary phosphorus adsorption experiments were performed using produced chars to demonstrate their environmental valorisation potential. Initial results indicate that pyrolysis temperature strongly affects the distributions of products and their properties. The solid char fraction dominated the product distribution at all pyrolysis temperatures ranging from 74 % at 350 °C to 53 % at 650 °C. Analyses of chars showed alkaline behaviour, with pH increasing from 7.7 to 11.0 as pyrolysis temperature increased due to the increasing inorganic (ash) fraction of the char. Subsequently, the PZC shifted toward higher values (7.8 to 11.3), indicating progressively more positively charged surfaces under neutral conditions. FT-IR analysis showed that increasing pyrolysis temperature progressively removes collagen-derived functional groups and enriches calcium phosphate mineral phases, leading to increasingly inorganic, apatite-dominated char surfaces as evidenced by increased pH and PZC. Batch adsorption experiments revealed that chars from pyrolysis at 500 °C performed best, removing 57% of orthophosphate from water, which may be attributed to an optimal balance between surface charge, mineral exposure, and solution pH. This study contributes to the growing body of applied pyrolysis research focusing on product characterisation and environmental value by linking pyrolysis conditions to product yields, char characteristics, and functional performance and the findings serve as a foundation for future optimisation of bone-derived chars for wastewater treatment and resource recovery applications.

ABSTRACT. Selective vapors condensation is a critical technology for producing high‑quality bio‑oil from biomass pyrolysis. Existing research has largely been confined to low‑to‑medium condensation temperature ranges, limiting its applicability for process optimization across wider temperature spans. This study systematically investigates the selective condensation behaviors of biomass pyrolysis vapors over an extended temperature range of 280–573 K. An integrated approach, combining fractional condensation recovery, vapor-composition inversion through functional fitting, and data-driven machine learning, was employed to systematically investigate the condensation characteristics and yield distributions of key bio-oil constituents, specifically water and phenolic compounds. Experimental results indicate that increasing the condensation temperature from 280 K to 337 K facilitates a 50% recovery of the aqueous phase, albeit with a concomitant increase in condensation residence time. In contrast, an equivalent recovery of guaiacol was achieved within a significantly shorter duration. Within the 280–364 K range, while the Logistic function exhibited a localized prediction accuracy below 50%, it maintained a robust global predictive accuracy of approximately 70% for representative components. Under small-sample constraints, a second-order polynomial regression model demonstrated superior performance, showing excellent alignment with experimental yields, with minimal deviations of -1.47% at 100 °C and -1.21% at 250 °C. This study establishes a comprehensive component-evolution profile and a predictive framework for the selective condensation of biomass pyrolysis vapors across a wide temperature range. These findings offer critical theoretical insights and technical benchmarks for optimizing cross-temperature selective condensation processes, thereby advancing the efficient production of high-quality bio-oil. Graphical abstract: heat maps of representative components & prediction and validation curves for AI and the logistic function. References: [1] Vilas-Boas ACM, Tarelho LAC, Marques CC, Moura JMO, Santos MC, Paradela F, et al. Improving bio-oil fractions through fractional condensation of pyrolysis vapors from Eucalyptus globulus biomass residues in a prototype auger reactor. J Anal Appl Pyrol. 2025;192:107329. [2] Li L, Luo Z, Miao F, Du L, Wang K. Prediction of product yields from lignocellulosic biomass pyrolysis based on gaussian process regression. J Anal Appl Pyrol. 2024;177:106295. [3] Chai S, Kang BS, Valizadeh B, Valizadeh S, Hong J, Jae J, et al. Fractional condensation of bio-oil vapors from pyrolysis of various sawdust wastes in a bench-scale bubbling fluidized bed reactor. Chemosphere. 2024;350:141121. [4] Akinpelu DA, Adekoya OA, Oladoye PO, Ogbaga CC, Okolie JA. Machine learning applications in biomass pyrolysis: From biorefinery to end-of-life product management. Digital Chemical Engineering. 2023;8:100103. [5] Zhang Y, Liang Y, Li S, Yuan Y, Zhang D, Wu Y, et al. A review of biomass pyrolysis gas: Forming mechanisms, influencing parameters, and product application upgrades. Fuel. 2023;347:128461. [6] Wang C, Diao R, Luo Z, Zhu X. Study on the influence of residence time on the componential evolution of biomass pyrolysis vapors during indirect heat exchange process through a combining method of bio-oil composition inversion and function fitting. Applications in Energy and Combustion Science. 2022;9:100047.

ABSTRACT. Crystal Violet (CV), a cationic dye belonging to the triarylmethane family, is primarily used in the textile industry, printing processes, and inks due to its strong tinting power and high chemical stability. However, CV is toxic and highly water-soluble, a property facilitated by its cationic groups (–N⁺(CH₃)₂), which allows for easy dispersion in aqueous environments. Increasing attention has been given to biochar as a promising, sustainable strategy capable of removing organic and inorganic pollutants from water bodies [1], making it a viable and cost-effective solution also for CV removal. By acting on the pyrolysis conditions, depending on the initial feedstock composition, it is possible to direct the process toward conditions producing biochar with properties effective for dye removal, such as well-developed porosity and the presence of active functional groups (e.g., carboxyl, hydroxyl, aromatic rings). To improve the biochar performance as an adsorbent, ball milling stands out as a mechanical approach able to modify the structure and the chemical functionalities of biochar by reducing particle size, increasing the BET surface, and introducing oxidized functional groups on the biochar surface, thereby enhancing the overall adsorption performance of the biochar [2]. In this study, we provide a novel and systematic investigation of the combined effect of pyrolysis temperature and ball milling on the physicochemical properties of biochar relevant for CV adsorption. Wheat straw was selected as the feedstock, as it represents an abundant agricultural residue whose valorization into high-value biochar aligns with circular economy principles and promotes the sustainable recycling of biomass waste. The performance of wheat straw-derived biochar, produced via slow pyrolysis at temperatures ranging from 360 to 600°C, is evaluated and compared before and after ball milling for its ability to remove different concentrations of CV from aqueous solutions. Overall, ball milling significantly improves the adsorption performance primarily by accelerating the adsorption kinetics, with the most pronounced benefit observed at intermediate temperature (450°C), where the milled biochar achieves near-complete dye removal within a few hours, demonstrating the highest performance in adsorption.

ABSTRACT. A circular economy could increase the efficiency of bio-resource use and improve bio-waste handling practices. Considering lignocellulosic plant residues from agriculture and manure as the most abundant and inexpensive feedstock for the biorefinery model in agriculture, a valuable approach could be the integration of different processes aimed at biofuel, biomaterial, and chemical production. Hydrothermal liquefaction (HTL) process is considered a viable thermochemical route to convert high-water-content biomasses in a liquid energy vector (biocrude). In fact, in HTL conditions (200–374°C and 40–200 bar), water acts as a catalyst, reactant, and thermal flywheel, and thus the biomass organic components can be directly converted without a drying step. While biocrude oil can be upgraded to bio-fuels for liquid transport and as a source of other chemical products, there is still considerable uncertainty for the carbon solid residue from HTL, the hydrochar (HC). HC is not under regulation for its use as a soil amendment, but its transformation into biochar could be a valuable route for a safe and standard application [1]. Nowadays, biochar is gaining ever greater recognition as a material with valuable applications in several fields, ranging from soil improvement and carbon sequestration to bio-based material for soil/water remediation, energy production, or filler as composite materials [2]. This study is focused on the exploitation of digestate through the HTL process for biocrude production and co-pyrolysis of HC and straw (S), lignocellulosic biomass representative of agricultural waste, to obtain the biochar and evaluate its properties. HTL of digestate will be performed in a 500 mL batch autoclave reactor, to study the yield and properties of the biocrude produced at different temperatures (300 and 350°C) and isothermal reaction times (0–30 min) [3]. Co-Pyrolysis of blends composed by different ratios of S and HC will be tested for biochar production, and the volatile phase will be explored as an energy vector to sustain the whole process. Preliminary results on biochar produced at a pyrolysis temperature of 450°C showed that the yields, for blends ranging from S90%-HC10% to S50%-HC50%, are in the range of 42.8–62.9 wt%. The corresponding biochars produced have respectively 28.3 to 51.66% ash content, whereas the H/C values are in the range 0.68 to 0.61. Both ranges of values are within the threshold limits reported in Regulation (EU) 2019/1009 for fertilizers and specified in detail in the Italian regulation (D. Lgs. 75/10, all. 2) that include biochar in their agricultural and environmental frameworks.

ABSTRACT. Woody biomass such as wood and herbaceous plants is composed of cells with cell walls. These cell walls exhibit a nanostructured assembly in which cellulose microfibrils—having a cross-sectional size on the nanometer scale—are embedded in a matrix of hemicelluloses (xylan and glucomannan) and lignin. Our research group has been investigating the supramolecular structure of wood cell walls by analyzing the thermal degradation behavior of their constituent polymers. In this presentation, we will introduce our recent findings.

Within the cell wall, molecular mobility is restricted, leading to pyrolytic reactivities that differ from those of isolated components. For instance, hemicelluloses such as xylan exhibit greater thermal stability within the cell wall than in their isolated forms. Although isolated xylan with uronic acid groups decomposes at lower temperatures than glucomannan, this difference in reactivity is significantly reduced in the native cell wall. The pyrolytic reactivity of these wood polysaccharides can be assessed by measuring the yield of hydrolyzable sugars obtained from hydrolysis of the pyrolysis char. While no reliable method had previously existed for evaluating the pyrolytic behavior of lignin in the cell wall, we have developed a TG–MS-based approach that enables such evaluation, allowing us to assess the reactivity of cellulose, hemicellulose, and lignin during wood pyrolysis.

Using this approach, we evaluated the pyrolytic behavior of five softwood and five hardwood species. The results revealed species-specific differences; however, when using samples in which the exchangeable cations—present as salts of xylan’s uronic acid groups—were replaced with only one type of cation, either an alkali metal (Na⁺, K⁺) or an alkaline earth metal (Mg²⁺, Ca²⁺), we found that the thermal degradation behavior of the components was determined solely by the cation species, irrespective of tree species. Notably, we discovered that these cations, although associated with xylan, primarily influenced the pyrolytic reactivity of glucomannan and cellulose, rather than xylan itself. In particular, cellulose decomposed at temperatures approximately 30 °C lower in the presence of Na⁺ and K⁺ compared to Mg²⁺ and Ca²⁺. Interestingly, lignin was found to degrade in synchrony with cellulose at this lower temperature. These findings led us to propose a novel supramolecular structure in which cellulose and lignin are closely associated.

ABSTRACT. Many cultural heritage items utilize lacquer, a natural polymer material. The tree species used for lacquer are primarily classified into three types: Toxicodendron vernicifluum, found in Japan, the mountainous regions of southern China, and Korea; Toxicodendron succedaneum, found in the coastal areas of southern China and Vietnam; and Gluta usitata, found in Thailand and Myanmar. While the main components and chemical compositions of these species differ by region of origin, their molecular structures are similar to each other. Therefore, identification methods using Py-GC/MS (Pyrolysis Gas Chromatography/Mass Spectrometry), which focuses on pyrolysis products specific to each species, have been effectively utilized as an analytical tool. However, conventional Py-GC/MS analysis involves cutting samples vertically for sampling, making it difficult to individually identify materials in each layer of multi-layered cultural properties. In contrast, a method involving interlayer delamination by gradually shaving small amounts from the sample surface to obtain material information per layer has been explored. However, problems such as sample disintegration during delamination have prevented its practical implementation. Therefore, in previous studies, the identification of lacquer tree species for each layer has primarily been performed using non-destructive methods, mainly IR analysis [1]. On the other hand, specimens embedded in epoxy resin for the purpose of cross-sectional observation of cultural heritage often have unused portions remaining that are not used for observation. These embedded specimens, reinforced by the epoxy resin, potentially allow for easier collection of micro-samples from each layer. However, analyzing microfragments collected from embedded specimens using Py-GC/MS presents a challenge: pyrolysis products derived from the epoxy resin are detected, interfering with the measurement results. Therefore, this study focused on existing research [2] that recovered carbon fibers embedded in epoxy resin and investigated a method to selectively decompose only the epoxy resin used to embed the specimens. Establishing this method would enable Py-GC/MS analysis of embedded samples, potentially yielding information on organic materials aligned with the coating's layered structure (Figure (a)). This is expected to enable more detailed and reliable tree species identification and material characterization based on Py-GC/MS, complementing conventional layer analysis using IR spectroscopy. In this study, we attempted to recover lacquer coatings (approximately 10 mg) embedded in epoxy resin by decomposing the epoxy resin using NaOH in a DMI solvent. As a result, we successfully decomposed only the epoxy resin and recovered the lacquer coating as a black precipitate. Analysis of the recovered precipitate by Py-GC/MS detected biomarkers derived from Toxicodendron vernicifluum, confirming the selective recovery and detection of the lacquer coating (Figure (b)). Furthermore, considering practical application to cultural property analysis, we also investigated micro-scale sample collection, resin decomposition, and lacquer coating recovery, which are reported here. [1] Nguyen, T. H. et al. Comprehensive multi-analytical investigations on the Vietnamese lacquered wall-panel “The Return of the Hunters”. Scientific Reports, (2019) 9, 17003. [2]Yasunori Minami et al. Degradation of stable thermosetting epoxy resins mediated by bases in amide solvents. Polymer Journal, (2025) 57, 149–162.

ABSTRACT. The growing global demand for clean water has intensified interest in sustainable technologies for desalination and wastewater purification. Among these, Solar Steam Generation (SSG) has emerged as a promising passive approach due to its low energy requirements, minimal carbon footprint, and ability to operate without fossil fuels. A key challenge in advancing SSG lies in identifying scalable, low-cost, and environmentally materials capable of efficiently converting solar energy into heat. Interfacial solar steam generation (ISSG), particularly when employing bio-derived carbon materials, offers significant advantages such as localized heating, enhanced evaporation rates, and compatibility with low-resource settings. In this study, we present a simple, sustainable ISSG device fabricated from untreated bamboo through low-temperature slow pyrolysis. Bamboo is an abundant, low-cost, and renewable biomass resource, making it particularly suitable for freshwater-stressed regions and low-income communities. Building on our previous investigations of bamboo’s electric, electrochemical, and paramagnetic properties across a broad pyrolysis range (200–1000 °C), we examined how controlled thermal treatment between 300 and 1000 °C affects the photothermal performance of monolithic bamboo-derived carbon under simulated solar irradiation [1-2]. The fabrication route, schematically shown here, preserves the intrinsic hierarchical architecture of bamboo—including microchannels, parenchymatic cell arrays, and interconnected porosity—while converting the native lignocellulose matrix into a black monolithic carbon [3]. Pyrolysis temperature and residence time were found to be critical in tuning key physicochemical parameters such as porosity, hydrophilicity, microchannel integrity, degree of graphitization, and thermal and electrical conductivities. Among all investigated samples, the monolith pyrolyzed at 400 °C (B400) exhibited the most advantageous balance of structural and functional properties. Under one-sun illumination, B400 reached a maximum temperature of 59 °C for a single cube and an average of 65 °C for an array of nine cubes, with a rapid heating rate of 0.29 °C s−1. The material maintained stable performance over ten heating–cooling cycles, demonstrating robust reproducibility. The preserved channel-like bamboo architecture facilitated efficient water transport and vapor escape, enabling an evaporation rate of 1.17 kg m−2h−1. These results confirm B400’s strong potential for solar thermal water purification applications. Notably, the enhanced photothermal response was achieved without chemical activation, dopants, or post treatment additives. The performance originates solely from the bamboo microstructure and the optimized low-temperature pyrolysis conditions. This minimal processing approach reduces environmental impact, lowers fabrication cost, and simplifies scalability, aligning with sustainable materials design principles. Overall, this work demonstrates that untreated, low-temperature pyrolyzed bamboo can serve as an efficient, durable, and entirely bio-derived photothermal material for ISSG. The findings open pathways toward affordable solar evaporators and broaden the use of biomass-derived carbon architectures in renewable energy and water purification technologies.

References 1. O.G.Pandoli, 3D conductive monolithic carbons from pyrolyzed bamboo for microfluidic self-heating system, Carbon (2023) 2. O.G.Pandoli, Permanent free radicals (PFR) in bamboo biochar-based flow bed reactor: a sustainable solution for dye degradation via adsorption and radical oxidation, Catal. Sci. Technol., (2025) 3. O.G.Pandoli et al. An investigation of the fluid-holding cavities in a lignocellulose-based bamboo matrix via a combined X-ray microtomography and proton time-domain NMR approach, Cellulose, (2023)

ABSTRACT. Among the various thermochemical methods for utilizing biomass, hydrothermal carbonization (HTC) is a promising technology. HTC converts renewable carbon sources, such as lignocellulosic biomass, into an energy-dense carbonized solid product known as hydrochar. Hydrochars of carbohydrates (i.e., glucose, cellulose, starch) and woody biomass samples (i.e., sawdust of fir and larch) were prepared by HTC at 200 °C for 24 h. The hydrochar yields of glucose, cellulose, and starch were nearly 40 % by mass, while larch and fir wood yielded a higher ratio at around 51 % due to their hydrothermally more stable lignin content. The properties of the hydrochars were characterized by ultimate analysis, higher heating values (HHV), Fourier transform infrared (FTIR) spectroscopy. In addition, morphological characteristics of the surface of the hydrochars were presented by scanning electron microscopy (SEM). The thermal behavior of the feedstocks and the hydrochars was determined by thermogravimertry/mass spectrometry (TG/MS), which also allowed us monitoring the evolution of devolatilizing compounds in the lower range of molecular weight. The comparison of the thermogravimetric curves showed that the carbohydrate contents significantly degraded during HTC, but a smaller volatile fraction remained in the hydro¬chars. Based on this observation, two-staged pyrolysis–gas chromatography/mass spectrometry (Py-GC/MS) measurements of the hydrochars were performed for the detailed analysis of the volatile contents of the hydrochars of carbohydrates and woody biomass samples. The findings of this study may enhance the production of hydrochars from different sources, which have the potential to be used as substitute products for coal and other fossil-based energy sources.

ABSTRACT. Hydrothermal carbonization (HTC) offers a promising pathway for converting organic residues with high moisture content into solid fuel without the need of energy-intensive drying. Conventional pyrolytic processes typically require a preliminary drying step, which limits the efficient utilization of wet biomass. Goat manure is an underutilized, highly available biomass with high moisture content in specific regions. In this work various HTC experiments were carried out on goat manure using a laboratory-scale, teflon-lined stainless-steel reactor. The influence of carbonization temperature was studied at four different temperatures between 200 and 275 °C using 8 h isotherm period. To evaluate the effect of carbonization time, HTC experiments were also performed at 225 °C with residence times of 4, 8, 12 and 24 h. The solid yield of the hydrochar products varied between 38 and 63 %, which decreased by the increasing process temperature. Proximate analysis, elemental analysis, and Fourier transform infrared (FTIR) spectroscopy measurements have been performed in order to characterize the composition of the samples. The raw goat manure sample had significant amounts of inorganic content (36 % ash), while the ash content of the hydrochars was even higher, indicating the dominating presence of water-insoluble inorganic components. The van Krevelen diagram of the raw and hydrochar samples reflected substantial deoxygenation during HTC with clear temperature-dependent trends. Hydrochars produced at 250 and 275 °C reached carbonization levels comparable to those of bituminous coal. The thermal behavior and the evolution profile of volatiles released from the raw and hydrothermally carbonized goat manure samples were characterized by thermogravimetry/mass spectrometry (TG/MS). The shape of the thermogravimetric curves reflected the development of carbonization increasing with residence time and process temperatures of HTC. The DTGmax temperature shifted to higher temperatures and the amount of residual char increased. A small decomposition peak at 650 °C in raw manure shifted to slightly higher temperatures in all HTC samples. This step was accompanied by the evolution of CO2, which indicated the decomposition of inorganic carbonates.

ABSTRACT. This study examines the thermal degradation behavior in nitrogen of three agro-waste feedstocks—pomegranate peel (Po), pistachio shell (Pi), and walnut shell (W)—under two stabilization methods: freeze-drying (F) and oven-drying (O). Thermogravimetric analysis (TGA) was used to determine onset temperature (Tonset), peak temperature (Tmax), and biochar yield. The aim was to establish TGA/DTG-based criteria for selecting suitable biomass feedstocks and pyrolysis conditions for high-performance porous carbon production. Results showed distinct differences in thermal stability and volatile release among the feedstocks. Pomegranate peel displayed the lowest stability, with Tonset values of 240 °C (PoF) and 235 °C (PoO). In the active pyrolysis zone (200–400 °C), mass losses were about 47.6 % (PoF) and 46.4 % (PoO), with DTG peaks at 249 °C and 348 °C corresponding to hemicellulose and cellulose decomposition, respectively. Freeze-dried PoF exhibited a higher total mass loss up to 1000 °C (71 %) compared with oven-dried PoO (68 %). This behavior aligns with reports that freeze-drying preserves thermally labile phenolics and creates a more open structure, promoting extensive devolatilization [1,2]. Conversely, oven drying partially degrades and densifies the peel matrix, resulting in slightly higher char residue [4]. Walnut shells exhibited higher thermal stability, with Tonset values of 267 °C (WF) and 265 °C (WO), and the highest Tmax (≈355 °C), reflecting their lignin-rich composition. In the active pyrolysis region (290–400 °C), mass losses were substantial (56.1 % for WF; 58.1 % for WO), leading to total losses of about 73.9 and 73.7 % up to 1000 °C. Despite different drying treatments, the final biochar yields remained nearly identical. Due to the dense, woody structure of the walnut shell, the drying method had no significant effect on the devolatilization process [3]. Pistachio shells exhibited the highest thermal stability (PiF Tonset = 276 °C; PiO Tonset = 274 °C), accompanied by the largest total mass loss (77.23–77.67 %). In the 290–400 °C range, devolatilization accounted for 64.7 % (PiF) and 61.7 % (PiO) with DTG maxima at 291 °C and 345 °C (hemicellulose and cellulose, respectively). The drying method had little effect: freeze-dried PiF showed a slightly higher Tonset than PiO, while Tmax and total mass loss were nearly identical, indicating limited structural or compositional change due to drying [5]. Overall, pistachio shells exhibited high thermal stability but released substantial volatiles during pyrolysis, resulting in moderate biochar yields. Pomegranate peel, less thermally stable, showed a stronger response to freeze-drying, with increased mass loss and lower biochar yields due to preservation of labile sugar and phenolic-rich fractions. The drying method exerted minimal influence on the hard shells but markedly affected pomegranate peel, as reflected by shifts in Tmax for the freeze-dried sample.

References:

1. Coklar H, Akbulut M, Kilinc S, Yildirim A, Alhassan I. doi:10.15835/nbha46211027 2. Anil S Ghorband1 and Suvidha P Kulkarni. doi:10.51470/FAB.2024.5.1.25 3. Uzun BB, Yaman E. doi:10.1016/j.joei.2016.09.001 4. Ao TJ, Wu J, Chandra R, et al. doi:10.1039/D5GC02029H 5. Kumar VK, Hallad SC, Panwar NL. doi:10.1007/s43937-024-00030-y

ABSTRACT. The iterative unchecked growth of Chaetomorpha linum, an invasive macroalga, in nutrient-rich lagoon ecosystems like Orbetello Lagoon (Italy) makes it necessary to find environmentally friendly ways to get rid of and utilize the algae. This paper is a proof-of-concept for Hydrothermal Liquefaction (HTL), a process that could potentially yield energy-dense biocrude and material products from this wet and tough-to-digest biomass without the energy loss of drying the feedstock first. Experimentally, parametric optimization studies in a batch reactor equipped with temperature control and pressure matching were implemented to explore a wide range of process conditions. Reaction temperatures of 240-340 °C, processing times of 10-120 minutes, different biomass-to-water ratios, and the use of homogeneous alkaline catalysts were the variables tested. The experimental data revealed that the degree of the process has a strong effect on the distribution of the products. The best conversion was carried out under subcritical conditions of temperature 340 °C and duration of 60 minutes, which corresponded to the production of 19% biocrude and 56% solid hydrochar by weight, the rest was divided between the aqueous phase (16%) and gaseous products. The chemical characterization clearly shows that the different fractions obtained have a range of uses. The biocrude, which is formed of a mixture of aromatic hydrocarbons, nitrogenated heterocycles, and long-chain fatty acids, can be upgraded to transportation biofuels, or the platform molecules can be extracted for the chemical industry. Additionally, the heavier biocrude fractions have been found to possess the characteristics of bituminous additives or binders that are renewable sources. On the other hand, the solid fraction (hydrochar) is still a good source though it contains a considerable amount of ash. The combination of a large surface area and a porous structure makes it a candidate low-cost adsorbent for the remediation of heavy metals in wastewater; furthermore, after proper desalting and removal of other inhibitory components, it can be used as a fertilizer for the soil in agriculture. The nutrients and organics in the aqueous phase make it worth recovering by integrating it with biological treatment processes. It is here highlighted that by adjusting the HTL parameters, a flexible C. linum biomass valorization route can be opened without the input of a fossil resource-consuming step, whereby an environmental nuisance is converted into a suite of renewable energy, chemicals, and materials within a circular bioeconomy framework.

ABSTRACT. The transition toward a bio-based economy necessitates the development of versatile platform chemicals, among which isosorbide (structure 1 in fig. 1a) (1,4:3,6-dianhydrosorbitol) is a primary candidate. While isosorbide is widely utilized for addition reactions to create polymers, solvents, and surfactants, its elimination products — specifically dihydrofuro[3,2-b]furan and 1,4:2,5:3,6-trianhydro-D-mannitol (structures 4 and 5 in fig. 1a) — have remained overlooked due to incomplete understanding of their formation and the lack of low-cost synthesis routes. This conference contribution shows for the first time how to harness the power of pyrolysis as a tool to simply synthesize these new elimination products.

By utilizing the pyrolysis-driven Ei β-elimination mechanism of isosorbide esthers and carbonates (fig. 1b), we successfully triggered the formation of the target elimination products from isosorbide at good yield and selectivity.

Key findings revealed that (i) isosorbide bis(dimethylcarbonate) (ISBMC, structure 15a in fig. 1b) is a superior precursor to elimination products compared to the diacetyl ester and (ii) the reaction time is crucial to achieve good yield and selectivity. Indeed, flash pyrolysis of ISBMC at 550 °C produced traces of dihydrofuro[3,2-b]furan (relative peak area of 2.16 area%). To maximize the yield of dihydrofuro[3,2-b]furan, prolonged residence times were applied at a lower temperature. ISBMC yielded a staggering selectivity of 21.22 area% for the target dihydrofuro[3,2-b]furan elimination product at 450 °C after 30 minutes (fig. 1c).

This work thus demonstrates that by optimizing temperature and reaction time, heat can be used as a sustainable tool to unlock new chemical building blocks from isosorbide, avoiding the need for hazardous reagents typically found in traditional multi-step liquid-phase synthesis. Therefore, we deem this contribution to be fit for the pyro conference.

ABSTRACT. The decline of fossil fuel resources and the negative impact of fuel combustion on the environment are forcing scientists to develop new technologies for producing functional carbon materials with various useful properties. To obtain carbon-containing materials with specified properties (shape, size, functional groups), interest arose in the thermochemical process of hydrothermal carbonization (HTC), due to the mild operating conditions (temperature up to 300 °C, self-generated pressure) in a subcritical water environment. The main objective of this work is to use analytical pyrolysis (Py-GC/MS) to expand our understanding of the chemical composition and structural characteristics of hydrochars during the formation of microspheres-containing carbons obtained by hydrothermal carbonization of monosaccharides – glucose and 1,6-beta-D-anhydroglucopyranose (levoglucosan). Two feedstocks were used for hydrothermal synthesis (HTC) – glucose (G) and levoglucosan (LG obtained at the Latvian State Institute of Wood Chemistry ). 1, 10 and 20% feedstock solutions were prepared, which were subsequently treated at 200, 250 and 300 °C for 4 hours in in a 250 ml high pressure autoclave. After separation the carbonized solid particles will be studied by elemental analysis, Py-GC/MS and SEM. Liquid by-products will be tested by HPLC-UV/ELSD/MS. This work not only provides a study of the properties of solid and liquid products after hydrothermal treatment of biomass, but also offers a theoretical platform for obtaining new efficient carbon materials for energy.

ABSTRACT. The agricultural industry generates significant amounts of wet organic wastes, offering the potential for bioenergy generation through thermochemical processes [1]. Hydrothermal carbonization (HTC) converts wet feedstocks into value-added products (i.e., hydrochar) without the need for drying. Thus, coupling HTC and hydrochar pyrolysis seems to be a promising alternative for enhancing energy recovery from agricultural biomass wastes. This study explores the pyrolysis behavior, kinetics, and hydrochar production from Olive Pomace Waste (OPW) and Agave Salmania bagasse (AB) for renewable biofuel production (pyrolytic oil and gas) via fast pyrolysis, which is critical for advancing the industrial implementation of integrated HTC–pyrolysis systems. For this purpose, TGA experiments were conducted at 1000 °C as final pyrolysis temperature and at three different heating rates (100, 400, and 800 °C/min). The pyrolysis runs were carried out for the two raw feedstocks (OPW and AB) and hydrochars produced at different HTC conditions: (i) 180 °C, 30 min (HC1) and (ii) 250 °C, 30 min (HC2), with the lowest (~ 20%) and highest (~ 35%) fixed carbon content, respectively. It was seen that increasing the severity of HTC improved the thermal stability of hydrochars by increasing pyrolysis' characteristic temperatures (Ti, Tm and Tf) in terms of onset, maximum decomposition and burnout throughout the process. Moreover, three common model-free methods including Flynn-Wall-Qzawa (FWO), Kissinger-Akahira-Sunose (KAS) and Friedman, were examined for their suitability to determine the pyrolysis kinetics of the hydrochars and raw feedstocks under study. According to linear regression and statistical analysis, FWO presented the best linear fit for analyzing the mean activation energy (Ea), represented as 64.18 and 58.10 kJ/mol for HC1OPW and HC2OPW, respectively, vs. 59.95 kJ/mol for the raw OPW feedstock. Conversely for AB, the mean activation energies exhibited an increased trend from 51.31 kJ/mol for raw AB feedstock to 104.79 kJ/mol (HC1AB) and 67.24 kJ/mol (HC2AB). A representative lignin extract from AB was further investigated based on biomass fractionation, which presented great stability at high conversions (α>0.8), showing that biomass chemical composition influences the thermal degradation of the feedstock. Finally, thermodynamic analysis indicated the feasibility for the pyrolysis of hydrochars due to the low difference between Ea and ΔH for all samples. In addition, reactions were nonspontaneous needing additional energy to take place while demonstrating less disorder throughout the progress of the pyrolytic process. These findings clearly show the potential for transforming wet agro-industrial biomass residues and waste into valuable biofuels and renewable energy production through HTC and hydrochar pyrolysis.

[1] Sangaré, D.; Bostyn, S.; Moscosa-Santillan, M.; Garcia-Alamilla P. ; Belandria, V.; Gökalp. I. Bioresour. Technol., 2022, 346, 126598.

ABSTRACT. • Context/Purpose: This study evaluates the bioenergy, spe-cifically hydrogen, potential of date seeds (DS), spent cof-fee grounds (SCG), and their blends, using a Deep Learn-ing model to optimize pyrolysis efficiency. • Methods: This study combines experimental methods—including compositional and thermogravimetric analysis (TGA), kinetic thermodynamic studies, and pyrolysis tests--with advanced predictive modeling using Long Short-Term Memory (LSTM) neural networks. By integrating experimental and AI-driven approaches, this study advanc-es biomass-based hydrogen production, contributing to a cleaner energy transition and a more circular hydrogen economy. • Results: Proximate, ultimate, fiber, TGA/DTG, kinetic, thermodynamic, and Pyrolysis tests were conducted for DS, SCG, and blends (75% DS–25% SCG, 50% DS–50% SCG, 25% DS–75% SCG). The blend ratio of 25%DS–75% SCG demonstrated the highest hydrogen yield potential. Three kinetic models were tested where KAS emerged as the most accurate one. An LSTM model, trained with lig-nocellulosic data, achieved exceptional accuracy in predict-ing TGA curves (R²: 0.9996–0.9998) • Interpretation: The analysis of the kinetic parameters for the three blends reveals that the blend ratio can signifi-cantly affect the activation energy (Ea) and the energy ef-ficiency of the pyrolysis process. Among the blends, Blend 1 emerges as the most energy-efficient option compared to the other blends and pure samples, with the lowest average activation energy. The pyrolysis results demonstrate that blending DS with SCG alters thermal degradation dynamics, favoring volatile release over char production and Blend 3 (25% DS- 75% SCG) is the best candidate for a better hydogen production quality. This study demonstrates the effectiveness of LSTM models in predicting TGA profiles for pure biomass and their blends, achieving comparable or superior accura-cy to ANN models from the literature. • These advancements have the potential to reduce reliance on TGA machines, cutting energy costs and streamlining thermal analysis processes • Conclusion: This research emphasizes the importance of shifting from fossil fuel-based “gray hydrogen” to renewa-ble “green hydrogen,” and highlights how underutilized biomass resources as well as machine learning (specifically deep learning) applications can contribute to this transi-tion

ABSTRACT. Agro-industrial residues such as pomegranate and prickly pear peels are abundant by-products with strong potential for renewable energy applications. This study examines their thermal degradation behavior and kinetic parameters, both individually and as a binary mixture, using thermogravimetric analysis (TGA) under a nitrogen atmosphere. Experiments were carried out from ambient temperature to 800 °C at heating rates of 5, 20, and 50 °C/min. Thermogravimetric (TGA) and derivative thermogravimetric (DTG) curves revealed multiple decomposition stages corresponding to moisture evaporation, degradation of hemicellulose and cellulose, and gradual lignin decomposition. Iso-conversional kinetic methods, including Flynn–Wall–Ozawa (FWO), Kissinger–Akahira–Sunose (KAS), and Friedman, were applied to determine the apparent activation energy and pre-exponential factor without assuming a reaction model. The calculated activation energies ranged from 96.61 kJ/mol for prickly pear peel to 185.72 kJ/mol for pomegranate peel, indicating differences in thermal stability and chemical composition. The binary mixture exhibited intermediate activation energy values (102.27–112.75 kJ/mol), suggesting possible interactions between the two biomasses during thermal decomposition. These results provide fundamental kinetic and thermochemical insights that are useful for the thermal conversion and energetic valorization of pomegranate peel, prickly pear peel, and their blends as sustainable biomass resources.

ABSTRACT. As the largest coal consuming country in the world at present, coal continue to be an important strategic resource for the overall development of Chinese society for a long time to come. Entrained-flow gasification is the core technology for clean and efficient utilization of coal, and is a leading and key technology in process industries such as coal based bulk chemical synthesis, coal to liquid fuel, coal to natural gas, and hydrogen production. The opposed multi-burner (OMB) entrained-flow coal-water slurry (CWS) gasification technology developed by the research team from East China University of Science and Technology ranks first in the world in terms of production capacity and achieved good economic benefits. The behavior of coal particles in an entrained-flow gasifier is critically linked to the stable operation of the system. During the gasification process, the thermal behaviors of the particles have significant effects on the heat transfer and reaction in the gasifier. However, observing these particles has been a significant challenge due to the high temperatures and complex atmosphere within the gasifier. In this study, utilizing a bench-scale OMB CWS entrained-flow gasifier and a visualization system equipped with high-temperature endoscopes and high-speed cameras of varying specifications, the comprehensive behaviors of particles within the gasifier are thoroughly investigated. Detailed discussions are provided on CWS atomization, particle fragmentation, devolatilization, volatile combustion, coke oxidation, gasification and deposition. The findings reveal that as the relative velocity between oxygen and CWS increases, the primary atomization mode transitions from a Rayleigh-type breakup to a superpulsating atomization mode. The occurrence of pyrolysis and gasification reactions results in the consumption of the carbon matrix, which affects the internal skeleton structure of the particles and forms a porous structure that is prone to causing the main body of the particles to break. The fragmentation probability reaches an extreme value due to the combined shock of the upward impinging-flow from the burner plane and the reverse flow from the arch at a distance of 400 mm above the burner plane. The detailed conversion patterns between different particle types near the burner plane, above the burner plane, and below the burner plane with different axial positions are discussed, respectively. Additionally, it is noted that within the gasifier, the char oxidation process typically has the longest duration, ranging from 200 to 2000 ms. Deposition behaviors in the gasifier are categorized into three droplet deposition modes and four particle deposition modes. Ultimately, a comprehensive particle evolution model corresponding to the droplet/particle deposition stage is established.

ABSTRACT. Hydrogen-rich blast furnace (HBF) technology holds significant potential for reducing carbon emissions in metallurgical industry. In HBF, H₂O generated via reverse water-gas shift reaction (RWGSR) influences coke dissolution loss (CDL) behavior. It is essential to understand these mechanisms to develop high-performance coke suitable for HBF. In this study, using conventional coke CA as a reference, cokes CB and CC were prepared by adding 5% coking coal and lignite thermal dissolution solubles (TDS), respectively. The reactivity (CRI) and strength after reaction (CSR) of these cokes were evaluated under CO₂ and H₂-enriched atmospheres. Microstructural characterization and CDL kinetic analysis of the coke were performed. Results showed that both coking coal and lignite TDS additions improved coke quality, reducing CRI and increasing CSR. In 5–10% H₂ atmospheres, CRI decreased and CSR increased for all cokes, indicating H₂’s inhibitory effect on CDL. However, at 15% H₂, CRI increased and CSR decreased for CA and CB, as H₂O from RWGSR promoted CDL. In contrast, CC maintained stable performance. Kinetic studies under CO₂+10%H₂ revealed a significant decrease in the CDL reaction rate and activation energy, with the pre-exponential factor dropping by nearly two orders of magnitude, suggesting an altered reaction pathway. Due to its high diffusivity, H₂ preferentially occupies active sites in coke, reducing effective collisions with CO₂. In CC, oxygen-containing functional groups enable H₂ to be firmly adsorbed via hydrogen bonds, resisting displacement by H₂O and thereby mitigating its promoting effect on CDL. This study proposes a novel approach for producing high-quality HBF coke: adding low-rank lignite-TDS during coking can expand coking coal resources, reduce costs, and yield coke with superior resistance to CDL under H₂-rich conditions.

ABSTRACT. The non-fuel valorization of low-rank coals, particularly lignite, represents a promising strategy for sustainable carbon utilization and CO2 mitigation. Mild depolymerization in alkaline media offers an attractive pathway to high-value oxygenated products such as humic acids, fulvic acids and aromatic carboxylic acids. However, the process efficiency is intrinsically governed by the complex macromolecular architecture of lignite, especially its cross-linked network composed of aromatic clusters, aliphatic bridges and oxygen-containing functional groups, which impedes solubilization and selective bond cleavage. In this study, several Chinese lignites were employed to elucidate the critical structure–reactivity relationships during the depolymerization in alkaline aqueous with different oxidative-assistance strategies, including O2 oxidation and electro-oxidation. Results reveal that depolymerization efficiency inversely correlates with cross-linking density and positively relates to the abundance of labile linkages and oxidizable moieties. Mild oxidation intensifies depolymerization and improves product selectivity. Notably, electro-oxidation not only circumvents the need for chemical oxidants but also enables concurrent hydrogen evolution at the cathode, thereby converting part of the oxidation energy into valuable H2 rather than dissipating it as heat. The tailored depolymerization products exhibit extensively potential for advanced materials applications, such as carbon dots, superplasticizer. This improved understanding of lignite’s structural reactivity supports the rational design of mild, efficient, and low-waste processes for producing oxygen-containing chemicals. Ultimately, leveraging the intrinsic structural features of lignite paves the way for its conversion from a low-grade fuel into a renewable feedstock for high-value applications, in alignment with circular carbon economy principles.

ABSTRACT. The coal gasification fine slag (CGFS) with high carbon content and poor reactivity are the difficulties in the resource utilization of solid waste from entrained-flow coal gasification. Achieving graded utilization is essential to promote the valorization of CGFS. This study mainly employs CGFS as the feedstock for preparing biomass pyrolysis catalysts, and utilizes flotation-enhanced separation to isolate carbon-rich fractions (CF) for subsequent thermal conversion. Specifically, CGFS is activated via a combined NaOH/air–steam treatment and co-calcined with urea to synthesize N-doped catalysts, which are applied to corn-stalk pyrolysis for the production of phenol-rich bio-oil; the effects of catalyst preparation conditions on phenolic yield and the corresponding catalytic conversion pathways are systematically investigated. Meanwhile, mild oxidation was mainly utilized to regulate the structure of CF in order to improve its reactivity. The results show that the N-doped CGFS-based catalyst increases the yield of phenolic compounds in bio-oil by a factor of approximately 1.35 relative to non-catalytic pyrolysis. Nitrogen-derived basic sites promote C–O and C–C bond cleavage as well as demethoxylation and decarbonylation, while suppressing secondary polymerization and coking, thereby enabling highly selective production of phenolic compounds. Besides, oxidation treatment can also improve the secondary gasification or combustion reactivity of CF, and the increase in pore structure is the main reason for the improvement of the reactivity of oxidized CF, which is benefit for the utilization of CGFS.

ABSTRACT. This study proposes a metal oxide/zeolite tandem catalytic system that, through synergistic catalysis, more efficiently directs the conversion of lignite pyrolysis volatiles into light aromatics. Concurrently, the pre-cracking stage effectively removes oxygen-containing components, thereby reducing coke deposition on the zeolite and extending catalyst lifetime. Experiments were conducted in a drop-type fixed-bed reactor, where volatiles generated in the pyrolysis zone at 600 oC were carried directly by the carrier gas into the tandem catalytic section. The first stage consisted of a metal oxide catalyst bed (e.g., CaO, MgO, ZnO), in which large molecules in the volatiles primarily underwent deoxygenation, cracking, and partial reforming reactions. The second stage contained an HZSM-5 zeolite bed (SiO2/Al2O3 = 25), where the products from the first stage mainly underwent aromatization reactions, resulting in increased yields of light aromatics. The upper metal oxide with basic sites effectively promotes the cracking of volatiles, significantly increasing the yields of hydrogen-rich gases and light aromatics while notably decreasing coke formation and effectively extending catalyst lifetime. This work confirms the feasibility of tandem catalysis for the directional conversion of lignite volatiles and provides a new strategy for the high-value utilization of coal resources.

ABSTRACT. Residual biomass is expected to play a central role in decarbonization strategies as a renewable resource aligned with sustainability goals. Among thermochemical conversion technologies, fast pyrolysis represents a promising approach for the production of liquid biofuels (bio-oils), chemicals, and renewable energy from biomass. However, crude bio-oil obtained from fast pyrolysis is typically characterized by a high content of oxygenated compounds, responsible for its unfavourable properties, including low heating value, high acidity, chemical instability, and poor storage performance. To overcome these limitations, several strategies have been investigated to reduce the complexity and abundance of oxygen functionalities in pyrolysis products. These approaches aim to promote efficient deoxygenation of bio-oils, thereby improving their physicochemical quality and conventional refinery compatibility. In this context, particular attention has been devoted to catalytic and non-catalytic co-pyrolysis processes, which represent promising solutions to enhance bio-oil quality. Due to the intrinsically high oxygen content of biomass feedstocks, the co-processing of biomass with hydrogen-rich materials, such as plastics, as well as the use of a catalyst, has been explored as an effective strategy to enhance deoxygenation efficiency. In co-pyrolysis, in fact, synergistic interactions between biomass- and plastic-derived intermediates can occur, with oxygenated compounds from biomass pyrolysis reacting with olefins generated from plastic degradation. These interactions can promote further deoxygenation and improve hydrocarbon selectivity toward more desirable products [1]. In the present study, preliminary co-pyrolysis tests of low-density polyethylene (LDPE) and Olive Stone (OS) were carried out using a plastic-to-biomass ratio of 10/90. Experiments were performed both in absence and in the presence of H-ZSM-5 zeolite catalyst (pore size ~5.8 Å, SiO₂/Al₂O₃ of 40) to evaluate its influence on the distribution and quality of the pyrolysis products. Acidic zeolites are well known for their effectiveness in enhancing selectivity toward valuable pyrolysis products, particularly aromatic hydrocarbons [2]. Reactor configuration also plays a crucial role in pyrolysis performance. Recently, spouted bed reactors have attracted increasing interest due to their distinctive hydrodynamic regime, which is favourable for achieving high bio-oil yields while limiting undesired, non-selective secondary cracking reactions, often promoted by prolonged contact with char particles. Therefore, in the present study, steady-state co-pyrolysis experiments were performed in a bench-scale plant consisting of a spouted bed reactor followed by an in-line fixed bed catalytic cracking reactor loaded with sand or zeolite catalyst. Both the pyrolysis and catalytic cracking stages were operated at 500 °C. The gas residence time in the spouted bed reactor was approximately 1 s, while catalytic tests were carried out at a space time of 20 (gcatalyst min/gOS). Preliminary results show that the presence of the catalyst affects both the yield distribution and the chemical quality of the pyrolysis products. However, an increase in the production of polycyclic aromatic hydrocarbons (PAHs) was also detected, highlighting the need for further optimization of operating conditions.

Figure 1. Schematic representation of the experimental setup.

[1] X. Zhang, H. Lei, S. Chen and J. Wu, Green Chemistry, 18 (2016) 4145-4169. [2] R. Cai, X. Pei, H. et al., Energy and Fuel, 34 (2020) 11771–11790.

ABSTRACT. To enhance the yield and quality of coal tar, coupling the water gas shift (WGS) reaction with gradient temperature pyrolysis of coal has been demonstrated to significantly improve the quality of both tar and pyrolysis gas. However, the underlying mechanism by which this integrated process enhances tar and gas product quality under steam atmosphere remains poorly understood. In this study, a two-section moving bed with independent temperature control as the pyrolysis reactor was employed, and deuterated water was used as a tracer to systematically investigate hydrogen migration pathways and reaction mechanisms during gradient temperature pyrolysis of coal in the presence of steam. The results show that, compared with the N2 atmosphere, under steam atmosphere at the high-temperature zone with temperature of T2 at 700 ℃, tar yield increased by 22.1% (a 1.2-fold increase) and H2 yield reached 4.7 mmol/g, representing a 2.4-fold enhancement relative to the control condition. Steam also enhanced tar quality by increasing the contents of light fractions (e.g., light oil and phenol oil), benzene, naphthalene, aliphatic hydrocarbons and phenols. Furthermore, under these conditions, hydrogen derived from steam migrates into all pyrolysis products. The distribution of migrated hydrogen among pyrolysis water, pyrolysis gas, tar, and char were found to be 19.8%, 29.5%, 4.5%, and 72.1%, respectively. As the T2 temperature increases, both char gasification in the high-temperature zone and WGS reactions in the low-temperature zone are promoted, facilitating the incorporation of •D and •OD radicals derived from steam into reactive sites such as DUar, Dα, and Dβ within tar fragments. Furthermore, under steam atmosphere, the proportion of inherent hydrogen in coal converted into pyrolysis gas (mainly H2 and CH4) and tar (including CH2Cl2-soluble tar and water-soluble tar) significantly increases, whereas the proportions converted to char and pyrolysis water decrease correspondingly. This also indicates that steam promotes the transfer of inherent hydrogen from coal to tar components while suppressing secondary reactions of volatiles, thereby reducing the formation of char and pyrolysis water. This process is governed by a combination of chemical and physical mechanisms, including thermal cracking, WGS reaction, char gasification, hydrogenation, and steam entrainment effects. These findings provide a solid theoretical basis for the in-situ efficient utilization of coal resources.

ABSTRACT. Sewage sludge biochar (SSB) is a circular material with strong potential to enhance the ecological performance of extensive green roofs while valorizing nutrient-rich waste streams. This study presents results from a 40-month rooftop monitoring experiment conducted under temperate climatic conditions, assessing the effects of SSB incorporation (10% and 20% v/v) on substrate physicochemical properties, hydrological behavior, runoff quality, vegetation dynamics, and microbial diversity. Amendment with SSB decreased bulk density and increased total porosity and water-holding capacity, thereby improving substrate moisture availability. These changes translated into enhanced water retention, with annual runoff reduced by 3.3–8.5%. The greatest reduction was observed in the SB20 treatment during the driest year (2022), while cumulative seasonal retention reached up to 76% in dry years. Although SSB originates from nutrient-rich feedstock, runoff nutrient concentrations showed an initial increase followed by stabilization, reflecting gradual nutrient release patterns. Vegetation cover increased to 73% in the control and to 84% (SB20) and 89% (SB10) over the monitoring period, with no statistically significant difference between amendment rates. Microbial analyses demonstrated higher bacterial and fungal richness in SSB-amended substrates, particularly at the 20% v/v level. Structural equation modelling revealed that variations in microbial richness were linked to changes in runoff chemistry (pH, electrical conductivity, total suspended solids) and interannual variability, rather than being attributable to a single controlling factor. Overall, this long-term rooftop study provides robust evidence of the systemic responses of extensive green roofs amended with SSB, particularly in terms of water balance regulation, substrate physical development, and microbial diversity enhancement.

ABSTRACT. In-situ detection is an important technique to realize catalytic cracking of coal pyrolysis volatiles. In this, catalytic cracking of Naomaohu coal pyrolysis volatiles over Fe and Al components in red mud was investigated using in-situ pyrolysis vacuum ultraviolet photoionization time-of-flight mass spectrometry with acid-treated red mud (ARM), Fe2O3, and Al2O3 as catalysts.

ABSTRACT. TBD

ABSTRACT. INTRODUCTION: According to the Global Waste Management Outlook of 2024 [1], 2.1 billion tons of municipal solid waste were produced in 2023, and only 13% of the controlled fraction was disposed of using the waste-to-energy approach.Hydrothermal liquefaction (HTL) is a promising thermochemical method that transforms wet bioresources into biocrude (BC) without expensive pre-drying [2]. To our knowledge, the existing literature contains just one study that examined the impact of hydrolytic pretreatment on the quality of BC produced through HTL of microalgae [3]. Furthermore, the literature indicates that acidic and alkaline additions enhance biofeedstock degradation during pretreatments, as well as improve the production and quality of BC in HTL processes. This work provides a first comparative examination of acid and alkaline pretreatment utilizing two kinds of real waste biofeedstocks, sewage sludge (SS) and olive oil pomace (OOP) residues, for BC production by HTL. The objective was to do an empirical systematic investigation to elucidate the impact of specific pretreatments on the distribution of the organic and inorganic fractions of the feed. RESULTS Following the HTL of pretreated SS, we were able to get larger yields of BC that were richer in aliphatic chains, along with higher values of H/C ratios and overall energy recovery. It is worth noting that pretreating SS with KOH resulted in the minimization of chemical species containing oxygen and nitrogen from the feedstock. Additionally, the H/C ratio of the BC obtained after HTL increased from 1.79 to 1.93 at 300°C and from 1.67 to 1.85 at 350°C. After HTL at 350 °C, SS that had been pretreated with HCOOH showed a significant increase in both the yield of BC and the amount of energy recovered. This can be due to the favorable impact that acid pretreatment has on increasing the organic content of the matrix. A densification of chemical energy in the generated BC is made possible, according to the data that was collected, by pretreatment with HCOOH and by ensuring that the kinetic severity of HTL is appropriate. CONCLUSIONS Hydrolytic pretreated SS as HTL feedstock increased BC yield from 18% to 23 and 34%; increased H/C ratios led to higher HHV values; and reduced relative intensity of the olefinic and aromatic C=C stretching bands, suggesting that the pretreatment may increase the aliphatic character of BC generated from hydrolysis. OOP pretreated feedstocks had lower BC yields than native ones and no significant HHV improvement. These findings show that pretreatments improve BC yield more for heterogeneous and mixed biofeedstocks like SS than for homogeneous matrices as OOP.

ACKNOWLEDGEMENTS PRIN Refuel (PRJ-0900) Progetti di Rilevante Interesse Nazionale 2022 funded by Ministero dell’Università e della Ricerca is acknowledged for supporting and funding this work

REFERENCES [1] Programme. Global Waste Management Outlook 2024: beyond an age of waste – turning rubbish into a resource. Nairobi. [2] Demirbas A. Energy Convers Manag 2001;42:1357–78. [3] Zhang B, He Z, Chen H, Kandasamy S, Xu Z, Hu X, Guo H.Bioresour Technol 2018;270:129–37.

ABSTRACT. Hard carbons derived from biomass are widely investigated as negative electrode materials for sodium-ion batteries (SIBs), particularly when produced through thermochemical routes that enable control over morphology, microstructure and surface chemistry. In this study, hard carbons (HCs) were synthesized from waste hemp hurd (WHH) using a scalable two-step thermochemical process consisting of hydrothermal carbonization (HTC) followed by high-temperature carbonization under inert atmosphere. The influence of acid-assisted HTC and the incorporation of metallic tin particles on the structural features and electrochemical performance of the resulting materials was systematically investigated. Acid-assisted HTC was employed to promote controlled polymerization and aromatization, while Sn-containing hybrid carbons were prepared following two different strategies: (i) addition of SnCl2 during the HTC pre-treatment step, and (ii) hydrothermal post-treatment of the already carbonized HC with SnCl2, followed by thermal treatment. This approach enabled a direct comparison of the effect of the Sn incorporation stage on the morphology, dispersion of the metallic phase and electrochemical performance of the hybrid materials. SEM-EDX images/analysis showed that Sn particles were effectively embedded within the carbon matrix in both hybrid materials, although a more homogeneous spatial distribution was achieved when Sn was introduced prior to the HTC step. This observation suggests that early-stage Sn incorporation favors a more intimate interaction between the metallic species and the evolving carbon framework during subsequent carbonization. Electrochemical characterization in sodium half-cells revealed that the incorporation of Sn led to a marked enhancement in performance compared to Sn-free HCs. Among the Sn-containing materials, the sample synthesized following strategy (i), exhibited the highest specific capacities, delivering up to 620 mA h g–1 at 0.1 A g–1 and retaining comparatively high capacities at increased current densities. The corresponding post-treated Sn-containing material also showed improved electrochemical behavior, although to a lesser extent, suggesting that Sn addition after carbon formation is less effective in achieving an optimal hybrid structure. By contrast, Sn-free samples displayed lower specific capacities and inferior rate capability, particularly in the absence of acid-assisted pre-treatment, highlighting the combined effect of HTC conditions and metal incorporation on Na-ion storage performance.

ABSTRACT. Biorefineries employing fast pyrolysis convert lignocellulosic feedstocks into bio-oil, biochar, and non-condensable gases, enabling renewable energy and chemical production. However, these processes generate complex mixtures of volatile organic compounds, including carbonyl species such as formaldehyde, which pose occupational health and safety concerns. Understanding the distribution and transformation of these compounds across feedstock and product streams is critical for risk mitigation, occupational health and safety controls, and environmental compliance. This research investigates the chemical evolution of volatile carbonyls and other hazardous species during a fluidized bed fast pyrolysis run at Natural Resources Canada’s CanmetENERGY-Ottawa facility. Each feedstock and resulting product—solid biochar, liquid bio-oil fractions, and gaseous outputs—will be sampled and analyzed using Solid Phase Microextraction (SPME) coupled with gas chromatography and flame ionization/mass spectrometric detection (GC-FID/MS). Universally applicable to each product stream, SPME enables selective, reproducible headspace sampling, providing a robust approach for tracking trace volatiles without matrix interference. Both on-fibre derivatization or direct analysis strategies will be explored, with a focus on enhancing analytical sensitivity and specificity. This work contributes to a deeper understanding of thermal conversion chemistry while addressing critical occupational health considerations in emerging bioenergy technologies.

ABSTRACT. This study clarifies relations between structures and caking properties of coals by correlating the structural features with caking behavior of the solvent-separated group components and their sub-fractions of coals. Sequential extraction and counter-extraction of four raw coals (RCs) of differing ranks with a mixed carbon disulfide/N-methyl-2-pyrrolidone (CS2-NMP) solvent were conducted to isolate various components. The characterizations of distinct components were conducted to clarify their structural features, and caking properties of each component were determined. A strong positive correlation is observed between the mass fraction of the medium component (MC) and maximum plastic layer thickness (Y) as well as caking index (G) of RCs. Heavy component (HC) possesses high graphitized carbon (CGR) content, low hydrogen-donating capacity, and negligible caking properties (G < 10). In contrast, the MC primarily comprises amorphous carbon (CAM) with low CGR, forming cross-linked networks of polycyclic aromatic hydrocarbons (PAHs) and alkyl groups. The G value of MCs correlates negatively with carbon unsaturation and positively with hydrogen-donating capacity. Crucially, this work distinguishes two sub-fractions of MC: The loose medium component (LMC) features smaller PAHs structures, longer side alkyl chains (SACs), and high caking properties (G > 90). Conversely, the dense medium component (DMC) poses larger PAHs structures, shorter but more SACs, higher hydrogen-donating capacity, and exceptionally strong caking properties (G > 100). This work shells light on the structural determinants (PAH size, alkyl chain length, hydrogen radical availability, carbon ordering) of caking properties and these results can be used to promote the targeted utilization of specific coal components to optimize coking efficiency.

ABSTRACT. The global demand for high-performance, energy-dense, and cleaner-burning fuels has driven the development of advanced hydrocarbon-based alternatives for propulsion and power generation applications. Conventional hydrocarbon fuels, while widely used due to their mature infrastructure and high energy content, face increasing scrutiny due to environmental concerns, inefficient combustion under extreme conditions, and the growing need for fuel systems compatible with next-generation aerospace and defense platforms. One promising strategy for improving fuel performance is structural modification at the molecular level, particularly through ring strain engineering. In this context, cyclopropanation—the introduction of three-membered cyclopropyl rings into hydrocarbon structures—has emerged as a viable route to enhance the energetic characteristics of fuels. Cyclopropane rings are known for their unique chemical and physical properties arising from their significant ring strain (approximately 115 kJ/mol), which leads to higher enthalpies of combustion, increased energy densities, and improved reactivity. Incorporating such rings into fuel molecules not only increases the gravimetric and volumetric heat of combustion but also modifies their thermal decomposition and ignition behaviors, making them attractive candidates for use in high-speed propulsion systems such as scramjets and advanced gas turbines. Despite the potential advantages, the design and development of practical cyclopropanated fuels require a deep understanding of their synthesis, stability, and combustion mechanisms under relevant conditions. In recent years, pyrolysis studies of highly strained fuels like cubane, bicyclo-octanes, and dicyclopropyl compounds have demonstrated that ring strain can dramatically alter reaction kinetics, promoting early ring-opening and subsequent fragmentation. However, most of these studies remain limited to fundamental molecules, and detailed kinetic models for practical multi-cyclopropanated fuels are scarce. In particular, experimental data on large cyclopropanated structures under combustion-relevant conditions are lacking, which hinders model validation and predictive development. This work investigates the pyrolysis characteristics of a novel cyclopropanated fuel, exo,exo-tetracyclo[3.3.1.02,4.06,8]nonane (exo-TCN), synthesized from norbornadiene via the Simmons–Smith cyclopropanation method. exo-TCN is a highly strained three-membered ring fuel with high density, high net heat of combustion, and good low-temperature performance, making it a promising candidate for high-energy-density liquid fuels. The pyrolysis experiments were performed in a micro flow tube reactor under varying temperatures and pressures. Reaction intermediates and final products were analyzed using gas chromatography coupled with mass spectrometry, providing detailed speciation data. These results were complemented by high-level quantum chemical calculations and rate constant predictions using RRKM/master equation analysis to elucidate the underlying reaction pathways and kinetic parameters. A detailed kinetic model was constructed to describe the pyrolysis behavior of exo-TCN. The model includes a reaction mechanism that accounts for the cleavage of cyclopropyl rings, ring-opening isomerizations, hydrogen abstractions, and β-scissions, as well as the formation and consumption of key intermediates such as allenes and propargyl. Model validation was performed by comparing simulation results with experimental data over a wide range of conditions, demonstrating good agreement and predictive capabilities. The validated model provides new insights into the thermal decomposition mechanisms of cyclopropanated fuels and establishes a framework for the future design and optimization of similar molecules.

ABSTRACT. Fast pyrolysis has attracted considerable attention for coal conversion owing to its capacity to shorten reaction time and enhance tar yield, while the influence of the reaction conditions on the pyrolysis behavior remains inadequately quantified. Here, an infrared fast heating reactor was employed and the effect of coal mass, final temperature and heating rate on product yield and composition of a typical tar-rich coal was thoroughly studied at a larger experimental scale than commonly used (tens of grams instead of milligrams). The results showed that during fast pyrolysis (heating rate 100 ℃/s), with the increase of sample mass from 10 g to 100 g, the volatiles could not be discharged from the reactor in time, and the intensified polycondensation or insufficient pyrolysis caused the gradually decreasing yields of tar and gas. With the increase of final temperature from 500 ℃ to 800 ℃, more chemical bonds were broken, resulting in the generation of more volatiles, and the tar yield increased to a peak and then decreased, while the gas yield gradually increased. The high temperature increased the secondary cracking and polycondensation reactions, which could also be confirmed by the decrease of the aliphatics and the increase of naphthalenes, anthracene, and PAHs in the tar. Under certain conditions (large sample masses, high final temperatures), fast pyrolysis can produce tar yields comparable to or even lower than those from slow pyrolysis, which challenges the widespread assumption that fast pyrolysis always maximizes tar yield. The investigation of the heating rate further demonstrated that an appropriate heating rate was beneficial for the increase of tar yield. This study concluded that lower sample mass and optimal final temperature were conducive to increasing the tar yield during fast pyrolysis, which was expected to provide valuable insights for fast pyrolysis research.

ABSTRACT. The increasing demand for lightweight, sustainable, and multifunctional materials for electromagnetic interference (EMI) shielding and microwave absorption has stimulated growing interest in biochar-based composites as environmentally benign alternatives to conventional carbonaceous fillers. Tailored biochar, derived from the controlled pyrolysis of biomass, offers a unique combination of hierarchical porosity, tunable electrical conductivity, surface chemistry, and structural disorder, making it a highly promising platform for enhancing electromagnetic properties in polymer, ceramic, and hybrid composites. This work presents a comprehensive overview of the design, tailoring, and application of biochar as an advanced functional filler for the development of composites with enhanced electromagnetic performance. The electromagnetic response of biochar-based composites is strongly governed by the intrinsic physicochemical characteristics of the biochar, which can be precisely engineered through feedstock selection, pyrolysis temperature, heating rate, residence time, and post-treatment strategies. High-temperature pyrolysis promotes graphitization and electrical conductivity, favoring conduction loss mechanisms, while lower temperatures preserve oxygenated functional groups that contribute to dipolar polarization and interfacial loss. Additionally, the development of multiscale porosity and defect-rich microstructures enhances multiple scattering and impedance matching, thereby improving microwave absorption efficiency over broad frequency ranges. Surface functionalization and heteroatom doping further expand the electromagnetic tunability of biochar by modulating charge distribution, dielectric relaxation behavior, and interfacial polarization phenomena. When integrated into polymeric or ceramic matrices, tailored biochar establishes percolated conductive networks and extensive interfacial regions, which synergistically enhance dielectric loss, suppress electromagnetic wave reflection, and improve absorption-dominated shielding effectiveness. Hybridization with magnetic phases, such as ferrites or transition metal nanoparticles, enables the development of biochar-based composites exhibiting combined dielectric–magnetic loss mechanisms, thus achieving superior EMI shielding and radar absorption performance at reduced filler loadings.

Beyond electromagnetic functionality, biochar-based composites offer significant advantages in terms of low density, thermal stability, cost-effectiveness, and environmental sustainability. The utilization of renewable or waste biomass as a carbon source aligns with circular economy principles and contributes to carbon sequestration strategies, positioning tailored biochar as a strategic material for next-generation green electromagnetic composites. Potential applications span aerospace structures, stealth and radar-absorbing materials, flexible electronics, energy devices, and construction materials requiring EMI mitigation. Here, we presented our more recent advancements in the tailoring of biochar for the preparation of electromagnetic enhanced properteis.

ABSTRACT. Phytoremediation, as a low-cost, green and highly efficient way for soil remediation, has been increasingly applied in China. However, the phytoremediation plant will lead to secondary pollution without appropriate treating. In this work, the co-pyrolysis of poplar (for soil remediation) and duckweed (for wastewater remediation) was investigated for the first time. The co-pyrolysis experiments were carried out successively in thermogravimetric analyzer and horizonal fixed-bed system, and the characteristics of three-phase products as well as the environmental risk assessment of Zn, Cd, and Pb were analyzed. The results indicated that with the blending ratio of duckweed rising (10% → 50%), the biochar yield generally showed an upward trend, while that of bio-oil decreased to some extent. The overall yield of gaseous product increased with the temperature rising (300 ℃ → 600 ℃), and the addition of duckweed promoted the production of H2, thereby achieving a higher heating value. It also shows that co-pyrolysis can improve the surface chemical structure and inorganic crystal phase composition of biochar, forming richer functional groups containing oxygen, nitrogen, and phosphorus, and generating stable phosphate/pyrophosphate structures, thereby providing more heavy metal complexation and fixation sites. Furthermore, toxicity characteristic leaching procedure (TCLP) and diethylenetriaminepentaacetic acid (DTPA) leaching tests were conducted to determine the mobility and ecological risk of heavy metals in biochar. It was found that the co-pyrolysis process was conductive to reduce the toxic leaching rate and enhance the stability, with the effectiveness following the order: Pb > Cd > Zn. Meanwhile, the bioavailability of Cd and Pb also decreased to a certain extent.

ABSTRACT. Hydrogen is widely recognized as a promising alternative carbon-free energy carrier due to its versatility in production from different energy sources. Dry reforming and thermocatalytic decomposition of methane using different types of catalysts have been studied to replace conventional hydrogen production technology by steam reforming [1]. Biochars, generated from biomass pyrolysis, offer compelling advantages, including low cost, high carbon content, and good textural properties. They exhibit significant catalytic activity for cracking of hydrocarbons such as methane [2], and they are also interesting support materials for the synthesis of metal/carbon catalysts [3]. Beside studies on biochars production from conventional lignocellulosic biomasses, the last decade showed a great interest on the valorisation of agricultural residues which are widely available in many countries.

Nevertheless, the differences in biopolymers and mineral mater composition of biomasses can lead to variable properties of the biochars. The aim of this study was to compare a conventional lignocellulosic biomass with catalysts obtained from douglas and corn cobs. The biochars were produced by fast pyrolysis at 800°C in a tubular reactor. Their physicochemical properties were determined by different characterization technics (Elemental Analysis, TGA, XRF, Raman, XRD, NMR 13C, SEM, N2 and CO2 adsorption). In order to improve their reactivity and textural properties, douglas and corn cobs biochars were activated physically by steam, CO2 and air. Some activated biochars were impregnated with nickel nitrate salts to obtain Ni/C catalysts. The catalytic performances of these materials were studied for dry reforming of methane (DRM) and thermocatalytic decomposition of methane (TDM) at temperatures between 750°C and 850°C during 30 min in a fixed-bed reactor. The reaction was followed by exhaust gas analysis by a micro gas chromatograph, and the spent catalysts were characterized after reaction.

A reaction rate analysis based on gas phase analysis and carbon mass balance was done for DRM and TDM experiments, allowing to quantify the different chemical processes: direct methane cracking, boudouard reaction, reverse water gas shift. Gasification reaction is strongly dependant of the catalyst precursor and preparation method while thermal cracking is less influenced. The addition of nickel nanoparticles induces an important increase of gasification rate for wood-based catalyst while this effect is lower for corn cob material. The thermal cracking is less modified. The study of the deactivation of the catalyst allowed to explore the different competitive processes: carbon deposits in pores and on nickel particles, gasification of the deposits and of the support.

1 Dufour, A et al. Catalytic Conversion of Methane over a Biomass Char for Hydrogen Production: Deactivation and Regeneration by Steam Gasification. Appl. Catal. Gen. 2015, 490, 170–180. 2 Mahmoudi,M et al. Evaluation of Activated Carbons Based on Olive Stones as Catalysts during Hydrogen Production by Thermocatalytic Decomposition of Methane. Int. J. Hydrog. Energy 2017, 42, 8712–8720. 3 Mahmoudi, M.et al. Hydrogen Production by Methane Decomposition over Ni Doped Activated Carbons: Effect of the Activation Method. Comptes Rendus Chim. 2022, 25, 225–236.

ABSTRACT. Global nylon-6 (polyamide-6, PA-6) production is projected to reach 10.4 million t/y by 2027, necessitating effective recycling of waste streams like fishing nets and other synthetic fiber residues. Research on PA-6 chemical recycling has focused primarily on solvolysis, whereas pyrolysis offers greater feedstock flexibility, faster reaction times, and ambient-pressure operation, while avoiding the use of costly solvents and unrecoverable catalysts [1]. The literature indicates that pyrolysis can efficiently depolymerize PA-6 to its monomer, ε-caprolactam. However, studies on PA-6 pyrolysis and catalytic pyrolysis remain limited and largely confined to analytical-scale investigations, and only a few laboratory- and bench-scale studies report robust quantitative product analysis and closed mass balances. Here, we report a PA-6 chemical recycling route based on catalytic pyrolysis using acidic and basic catalysts to selectively recover ε-caprolactam, demonstrated in a batch laboratory fixed bed reactor with thorough condensate analysis and quantitative ε-caprolactam measurements. Ε-caprolactam, standard PA-6, and waste fishing nets were pyrolyzed in a fixed-bed reactor at 300-600 °C using in situ and ex situ Y, ZSM-5, MgO, and KOH/Al2O3 catalysts. Gas, solid, and condensate products were collected and analyzed. Ε-caprolactam in the condensate was quantified by GC–FID calibrated with internal and external standards. Thermal pyrolysis demonstrated ε-caprolactam’s thermal stability at 300-400 °C, resulting in 99-100 wt.% recovery in the condensate, while at 500 °C limited degradation reduced recovery to 94 wt.%. Thermal pyrolysis of standard PA-6 at 500 °C yielded 96 wt.% condensate but quantitative GC-FID showed only 33 wt.% ε-caprolactam content, with the remainder comprising of oligomers, confirmed by GPC. Similar results were obtained with waste fishing nets. Ex situ catalytic pyrolysis with ZSM-5 and MgO reduced oligomers but marginally increased ε-caprolactam recovery from 31 wt.% to 32 wt.% and 36 wt.%, respectively. Y exhibited the highest activity for the conversion of oligomers but also for the decomposition of ε-caprolactam, resulting in reduced overall recovery. On the other hand, in situ catalytic pyrolysis enabled depolymerization at lower temperatures and increased ε-caprolactam selectivity, reaching up to 90 wt.% ε-caprolactam content in the condensate using KOH/Al2O3. However, KOH/Al2O3 deactivated rapidly due to carbon deposition, and regeneration by oxidation was not feasible because high temperatures decomposed KOH. MgO was the next most active catalyst, yielding condensates with 72 wt.% ε-caprolactam content, while also allowing high-temperature regeneration due to its superior thermal stability. Overall, ε-caprolactam was recovered from PA-6 via pyrolysis. However, the condensate comprised primarily of oligomers, resulting in lower recoveries than previously suggested. Ex situ catalytic pyrolysis yielded condensates with reduced oligomers, but ε-caprolactam recovery marginally benefited due to byproduct formation. In situ catalytic pyrolysis with a benchmark KOH/Al2O3 yielded condensates with 90 wt.% ε-caprolactam, consistent with previous reports, but deactivated rapidly and could not be regenerated. MgO yielded condensates with high ε-caprolactam content as well, and could be regenerated after use.

Figure. Comparison of PA-6 pyrolysis strategies for the selective recovery of ε-caprolactam.

[1] S. Czernik, C.C. Elam, R.J. Evans, R.R. Meglen, L. Moens, K. Tatsumoto, Journal of Analytical and Applied Pyrolysis, 46 (1998) 51–64.

ABSTRACT. Polyvinyl chloride (PVC) is a common thermoplastic widely used thanks to its properties and relatively low cost. However, its production results in large quantities of chlorinated waste and associated disposal issues. A more sustainable solution is chemical recycling. Compared to other standard thermoplastics, PVC decomposes at a significantly lower temperature. To prevent autocatalytic dehydrochlorination of PVC and improve its stability and end-use properties, additives such as heat stabilisers and plasticisers are incorporated into pure PVC. Catalytically active additives, such as metal salts, can accelerate or inhibit the dehydrochlorination reaction. Therefore, the pure PVC decomposition mechanism may not fully explain the pyrolysis behaviour of PVC waste due to the presence of various additives. This work aimed to investigate the influence of additives in real PVC waste on the pyrolysis mechanism. Representative samples of PVC waste containing additives, such as hard and soft PVC, along with the purest possible PVC sample, were analysed using X-ray diffraction, attenuated total reflectance Fourier-transform infrared spectroscopy and inductively coupled plasma optical emission spectrometry. The samples were then pyrolysed in a μg pyrolyser for reference purposes. The resulting volatile pyrolysis products were identified using gas chromatography-mass spectrometry. A comparison was made between the observed pyrolysis products and the identified components corresponding to the additives and their decomposition products. The possible influences on the pyrolysis mechanism were then discussed. In general, PVC degrades via a two-step process: at 290 °C, dehydrochlorination occurs, resulting in the formation of a conjugated polyene. This is then followed by the formation of aromatic hydrocarbons at 424 °C¹. Many additives, such as the carboxylic acid groups found in plasticisers and the alcohol groups found in heat stabilisers, can replace the unstable chlorine atoms in PVC. It is therefore assumed that cyclisation of the dehydrochlorinated PVC backbone is suppressed during primary pyrolysis. This could lead to reactions resulting in cross-linking of the macromolecule. Consequently, the formation of benzene and naphthalene is also suppressed. During the second stage of the mechanism, cleavage of the cross-linked macromolecule predominantly forms substituted derivatives. Due to stronger cross-linking, it is also assumed that cleavage of the polyene shifts to higher temperatures. Additionally, metal salts such as calcium carbonate bind chlorine, thereby reducing the amount of free HCl present. This probably suppresses the autocatalytic effect of HCl as a hydrogen sink. Consequently, there may be fewer radical positions in the PVC hydrocarbon backbone, meaning it tends to react to form cross-linked macromolecules rather than undergo cyclisation. Various chlorine-containing components were also identified, presumably arising mainly from the replacement of the OH group with HCl in the cracked products of the additives. When real PVC waste containing additives is pyrolysed, fewer HCl molecules are released at lower temperatures. The reduced presence of unsaturated polyenes means that a smaller quantity of aromatic by-products is produced. Additionally, there is less coke formation. These observations will be investigated further in the future using quantitative analysis of the pyrolysis products of real PVC waste. 1 J. Yang et al., Fuel 331 (2023) 125994, doi: 10.1016/j.fuel.2022.125994

ABSTRACT. Mixed plastic waste generated in municipal organic waste treatment plants represents a critical challenge for both composting efficiency and material recovery. In this study, the mixed plastic waste was collected from a waste treatment facility producing compost, where plastic carrier bags are separated during the pretreatment of the organic fraction. These bags consist of a heterogeneous mixture of biopolymers, mainly Mater-Bi and polylactic acid (PLA), together with polyethylene (PE). To enable the recovery of polyethylene through chemical recycling, two alternative processing routes are proposed and investigated. The first route involves anaerobic digestion of the mixed plastic waste, aiming to biologically convert the biodegradable polymer fraction into biogas, while producing a polyethylene-rich solid residue subsequently processed by pyrolysis for fuel oil production. The second route is based on hydrothermal treatment as a selective pretreatment to decompose PLA/Mater B, yielding a solid residue mainly composed of polyolefin, which is then converted by pyrolysis into a high-quality fuel oil. In particular, the hydrothermal degradation of PLA was systematically investigated, focusing on the effect of temperature in the range of 150–250 °C and of reaction time (0-120 min) on polymer decomposition. The objective was to promote controlled depolymerization of PLA/Mater B, enabling the recovery of its monomeric products and thus opening the possibility of material recycling. The composition and properties of the solid residues obtained after hydrothermal treatment were evaluated to assess their suitability as feedstock for pyrolysis. The results demonstrate that temperature of 180 °C and 30 min are needed to have 100 % depolymerization of PLA compounds. The main compounds obtained in HT are lactic acid and oligomers, from GC-MS analyses the maximum concentration of lactic acid was obtained at 220 °C for 10 min of reaction time. The sold residue was weighted resulting to be about 60 % of the mixed plastic waste and was analyzed by FT-IR, TGA and elemental analysis in order to assess its purity in polyolefin species. The analysis revealed that still some oxygen is present in the solid residue, probably due to the presence of PLA oligomers. However the amount of O is highly reduced from 20 % wt. of the feedstock to 7 % wt. The results of AD+pyrolysis are less attractive since Mater B and PLA are non easy to be decomposed in AD and so the reduction of oxygen in solid residue is limited going form 20 % to 14 % wt.

ABSTRACT. Pyrolysis and gasification of waste are well-known methods for their recycling. The effect of raw materials and process parameters is widely investigated by analytical or bench scale equipment. However, limited information is available on the experimental results performed in larger-scale facilities. There are also many opened questions about the further use of the products of pyrolysis and gasification and their integration into existing industrial infrastructure. To answering these questions, a complex experimental infrastructure consisting of different reactor systems on a pilot scale has been established, which can be used to investigate the recycling of solid waste (e.g. biomass, sewage sludge, plastic, etc.) and their integration into a circular economy. Primarily pyrolysis oil from plastic waste had been obtain with a system containing several different reactors, from which petrochemical raw materials for polymerization purposes was produced with a scaled-up steam cracking facility. Synthetic hydrocarbons or alcohols from synthesis gas obtained by biomass, paper, sewage sludge, heavy oil or contaminated plastic waste gasification had been also produced at high pressure and high temperature. The primary goal is to improve the yield and quality of valuable products and investigate the techno-economy aspects of the processes towards the circular economy.

ABSTRACT. In a bid to address the ever-growing quantities of industrial and domestic biomass waste, while also providing a sustainable alternative to crude oil based fuels, biomass valorization has gained increasing attention. Major thermochemical valorization pathways include gasification, pyrolysis, and hydrothermal liquefaction (HTL). Among these, HTL is particularly significant due to its ability to process wet biomass feedstocks without the need for energy-intensive and time consuming drying. It has proven especially effective for sewage sludge valorization, delivering promising results in terms of conversion efficiency and product quality. This research focused on the production and characterization of biocrude oil from sewage sludge digestate using a bench-scale HTL process. Sludge digestate was collected from a municipal wastewater treatment facility in the south Apulia region. A slurry containing 15 wt.% solid digestate was prepared with water and processed in a 500 mL high pressure/high temperature PARR reactor. Reaction temperatures were varied between 280 °C and 320 °C, with retention times of 30, 45, and 60 minutes, in order to identify the optimal conditions for maximum biocrude yield and improved product quality. Ethyl acetate was used as the organic solvent for the separation of biocrude from hydrochar. The recovered biocrude was characterized using CHNS/O elemental analysis, Fourier Transform Infrared Spectroscopy (FTIR), Gas Chromatography–Mass Spectrometry (GC–MS) and Nuclear Magnetic Resonance (NMR) spectroscopy, while the hydrochar was characterized by FTIR and Scanning Electron Microscopy (SEM). An intensive experimental campaign, which lasted more than three months and involved over seventy experimental runs, was conducted under varying operational conditions, yielding a total of approximately 650 grams of biocrude oil, targeting subsequent engine testing and/or oil upgrading. The highest average biocrude yield (24%) was obtained at 300 °C with a retention time of 30 minutes, corresponding to a hydrochar yield of 48%. The GC-MS result of this biocrude fraction showed that it is dominated by long-chain fatty acids with moderate phenolic and ketonic fractions. While the carbon chain length favors good energy density, the abundance of oxygenated functional groups necessitates additional treatment for fuel applications. The observation of the chemical and physical properties of the biocrude oil samples (8-9 grams) collected at each test allowed to identify the operating conditions for producing biocrude oil with the highest quality for direct use as a fuel as well as the upgrading requirements to be fulfilled through hydrotreating.

Figure 1: Sludge digestate used as the feedstock, the HTL experimental setup based on a 500 mL batch reactor, the biocrude oil produced from repeated experiments.

ABSTRACT. Plant based carbons (PCs) have emerged as promising anode materials for sodium ion batteries (NaIBs) due to their low sodiation potential (below 1.0 V vs. Na⁺/Na), good reversible capacities (200–300 mAh g⁻¹), low cost, and inherently low toxicity. Biomass derived carbons are receiving increasing attention as scalable, renewable alternatives to conventional graphitic carbon, whose production remains costly and resource intensive for large scale HEV/EV applications. Among biomass sources, bamboo represents an ideal precursor: although botanically a grass, its high carbon content, hierarchical pore architecture, rapid growth rate, and global availability make it a sustainable platform for energy storage materials [1]. Previous studies have demonstrated that pyrolyzed bamboo can produce conductive, mechanically robust carbon monoliths suitable for microfluidic heaters, electrochemical devices, and even lithium and sodium ion batteries. Low temperature pyrolysis produces resistive 3D carbons (σ ≈ 6.6 S m⁻¹), while higher temperature treatments up to 1000 °C yield finely tuned graphitic domains with electrical conductivity up to 250 S m⁻¹[2]. Bamboo derived carbons have also shown strong redox behavior linked to persistent free radicals, enabling efficient degradation of organic dyes through electron transfer pathways [3,4]. In this work, bamboo based biochars (BBs) were synthesized using optimized slow pyrolysis and fast pyrolysis with CO₂ activation under N₂/CO₂ atmospheres at 800 °C and 1000 °C. The resulting materials were evaluated as NaIB anodes using an environmentally friendly electrode configuration consisting of carboxymethyl cellulose (CMC) as an aqueous binder and aluminum as the current collector, replacing the more resource intensive copper. Electrochemical testing revealed that fast pyrolyzed samples with CO₂ activation (800FPy and 1000FPy) delivered superior cycling performance, maintaining stable reversible capacities of approximately 110 mAh g⁻¹ and 140 mAh g⁻¹, respectively, over more than 200 cycles. In contrast, slow pyrolyzed samples (800SPy and 1000SPy) exhibited higher initial capacities but suffered from reduced capacity retention, highlighting the beneficial role of CO₂ induced porosity and defect engineering in promoting stable Na⁺ storage. The results align with sodium storage mechanisms in disordered carbons, including Na⁺ adsorption at defects and pores, interlayer insertion, and pore filling by quasi metallic sodium clusters. Overall, this study demonstrates that untreated bamboo derived carbons, produced through simple and scalable pyrolysis routes, represent viable and environmentally friendly anode materials for next generation sodium ion batteries. Their tunable microstructure, low cost fabrication, and robust cycling stability underscore their potential to support sustainable, large scale energy storage technologies.

rRferences [1] Pandoli, O.G. et. al., Biomass Bioenergy 2025, 107511 [2] Pandoli, O.G. et.al, Carbon 2023, 118214. [3] Pandoli, O.G. et.al, ChemCatChem 2024, e202401042. [4] Pandoli, O.G. et.al, Catalysis Science & Technology, 2025.

ABSTRACT. Methane pyrolysis is attracting growing interest as a sustainable route to CO2-free hydrogen production and advanced carbon materials. However, the fundamental mechanisms governing carbon nucleation and growth on reactor walls and solid substrates remain only partially understood, particularly under conditions relevant to industrial operation. This work presents a combined experimental and characterization study of carbon deposited on quartz walls and graphite plate surfaces during methane pyrolysis, with the objective of elucidating how operating conditions and gas-phase chemistry govern the resulting carbon morphology and structure. Methane pyrolysis experiments were conducted in a tubular flow reactor (length 40 cm, inner diameter 1.5 cm) containing a graphite plate (13×25 mm) positioned at the reactor centerline. The system was operated over a temperature range of 875–975 °C, residence times adjusted via methane inlet flow rates of 30–60 mL/min, and exposure durations of 0.75–3 hours. This parametric design enabled systematic investigation of temperature, flow rate, and operation time effects on carbon deposition. The morphology and structure of surface-grown carbon were characterized ex situ by scanning electron microscopy (SEM), Raman spectroscopy, and Brunauer–Emmett–Teller (BET) surface area analysis. These complementary techniques enabled discrimination between amorphous particles, pyrolytic carbon, and filamentous structures, while providing quantitative insight into morphology, structural disorder, and specific surface area. Results demonstrate that carbon deposition during methane pyrolysis is strongly governed by temperature. At lower temperatures (875 °C), filamentous carbon structures formed and grew with increasing residence time, with structure complexity and branching features modulated by gas mean residence time in the reactor. Increasing temperature suppressed filament formation in favor of more compact, two-dimensional carbon growth. This morphological transition was quantitatively confirmed by BET measurements, which showed a dramatic decrease in specific surface area from 75 m²/g at 875 °C to 5 m²/g at 975 °C, consistent with the loss of high-surface-area filamentous features. Raman spectroscopy revealed that carbon deposits on the graphite plate exhibited lower structural order than the substrate itself, with intensity ratios ID/IG ranging between 0.93 and 0.96, indicating substantial disorder and defect density in the deposited material. Overall, this study provides quantitative data and mechanistic insight into carbon formation on surfaces during methane pyrolysis, bridging the gap between homogeneous gas-phase decomposition chemistry and heterogeneous carbon formation. These findings are directly relevant for optimizing methane pyrolysis reactor design and operation for low-carbon hydrogen production, as well as for understanding and controlling carbon deposition, fouling, and selective carbon growth in high-temperature industrial processes.

ABSTRACT. Understanding hydrocarbon cracking and coke formation at the molecular level is critical for advancing industrial thermal cracking processes. Conventional molecular dynamics simulations are typically limited to unrealistically high temperatures in order to overcome large and widely distributed reaction barriers, which can distort reaction pathways and product distributions. In this work, we present an enhanced sampling framework, termed OPES_CVHD, which integrates on-the-fly probability-enhanced sampling (OPES) with collective variable-driven hyperdynamics (CVHD), enabling efficient and kinetically reliable simulations of complex cracking and coking chemistry at moderate temperatures.

In OPES_CVHD, the bias potential is constructed from the marginal probability distribution of collective variables and adaptively updated through a self-consistent barrier parameter. A damping strategy is introduced to regulate bias growth near transition states, preventing excessive bias deposition and preserving accurate reaction kinetics. This framework requires minimal prior knowledge of reaction pathways and is particularly suited for systems involving multiple competing reactions with widely separated energy barriers.

The performance of OPES_CVHD is demonstrated through simulations of styryl radical β-scission and, more importantly, the pyrolysis of methylcyclohexane (MCH), a representative cycloalkane fuel. Simulations conducted at 1000–1500 K reproduce MCH conversion, product distributions, and reaction kinetics consistent with conventional enhanced sampling simulations and experimental observations. Compared with standard CVHD, OPES_CVHD achieves significantly improved sampling efficiency, enabling deeper cracking within the same computational cost.

Crucially, OPES_CVHD enables direct observation of the early-stage formation of aromatic and polycyclic aromatic hydrocarbons at temperatures far below those required in conventional molecular dynamics simulations. The simulations resolve detailed formation pathways of monocyclic and bicyclic aromatic species, revealing highly reversible reaction networks involving β-scission, radical addition, hydrogen abstraction, isomerization, and cyclization. The predicted H/C ratios and carbon-number distributions of coke precursors are in good agreement with experimental measurements, demonstrating the physical reliability of the approach.

Overall, OPES_CVHD provides a powerful and flexible molecular simulation framework for investigating hydrocarbon cracking and early coke precursor formation under industrially relevant conditions, offering new mechanistic insights into thermal cracking and coking processes.

ABSTRACT. Oil-based drill cuttings (OBDC), generating during shale gas extraction, contain high levels of total petroleum hydrocarbons (TPHs), heavy metals, and polycyclic aromatic hydrocarbons (PAHs), which can pose significant risks to both human health and the environment. The effective treatment and utilization of OBDC constitutes a major challenge for the oil and gas industry. This study conducted catalytic pyrolysis experiments on OBDC using a two-stage fixed bed reactor with OBDC pyrolysis slag as catalyst. The influence of calcination temperatures (400~700 °C) of OBDC slag on the distribution and properties of pyrolysis products produced from both the fast and the slow pyrolysis modes was explored. Results indicated that the slag catalyst can enhance gas yield while reducing liquid yield, with char production remaining almost unchanged. It can also promote oil lightening and deoxygenation/desulfurization. The slag calcined at 700℃ exhibited the superior catalytic performance for OBDC under the fast pyrolysis mode: it increased the light fraction (<C12) by 28.90%, reduced the heavy species (>C22) by 35.62%, and elevated aromatic yield by 31.98% (compared to non-catalytic conditions). The aromatics primarily comprised 1-ring and 2-ring species such as benzene, indene, and naphthalene, up to 65.12% in yield. The catalytic activity of slag catalyst primarily stemmed from the synergistic interactions between residual metals and their compounds on the surface, along with the surface acid sites. Furthermore, the large pore volume/pore size of slag catalyst can suppress the deactivation process. Overall, OBDC slag catalyst demonstrates great potential when used as a catalyst for the pyrolytic treatment of oil waste.

ABSTRACT. The development of high-performance biochar via pyrolysis represents a sustainable solution for addressing the global challenge of per- and polyfluoroalkyl substances (PFAS) contamination. This study focuses on macadamia nut shells as a high-density, carbon-rich feedstock chosen for its physical integrity and high fixed carbon content during surface modification. A critical factor in determining the effectiveness of the final adsorbent is the influence of pyrolysis kiln characteristics on the biochar prior to functionalisation. This research systematically evaluates biochar produced across three scales of thermal conversion: lab-scale tube furnace, artisanal kiln (retort kiln), and community-scale biochar kiln. Each kiln type imposes distinct heating rates, residence times, and oxygen limitations, which fundamentally alter the pore structure and surface chemistry of the resulting biochar.

The raw biochar was produced through slow pyrolysis, at 550°C to ensure a stable and porous carbon structure. The structural and chemical evolution of the biochar from each kiln was analysed to identify the optimal precursor for subsequent Iron (Fe) impregnation. Biochar characterisation included CHNS elemental composition to evaluate carbon mass balance and degree of carbonization. Furthermore, surface morphology and specific surface area were quantified through BET analysis, while functional group distribution was analysed using FTIR spectroscopy to verify the availability of binding sites. The results demonstrate that the dense pyrogenic structure of the macadamia shell is highly resistant to significant pore blockage, but the variability in kiln performance significantly impacts the uniformity of the aromatic carbon matrix.

Identifying the best biochar matrix is essential for the stage of modification, where the material is impregnated with iron-based solutions to induce positive surface charges. The Fe-impregnated biochar target PFAS removal through synergistic mechanisms: electrostatic attraction between the positively charged iron sites and the anionic headgroups of PFAS molecules, and hydrophobic interactions between the fluorinated tails and the aromatic biochar surface (Hassan et al., 2022; Teng et al., 2025). While lab-scale production offers the highest parameter controls, evaluating artisanal and community-scale kilns is vital for scaling up mass production and environmental remediation efforts in a engineered biochar for adsorption material.

The comparative analysis reveals how differences in kiln-induced thermal gradients affect the structural density and porosity of macadamia biochar, directly influencing its capacity to support a high distribution of metal on biochar surface. By optimising the feedstock-kiln relationship, this study identifies pathways for creating value-added adsorption materials from agricultural residues while addressing the emerging challenge of persistent organic pollutants. Future experiments will quantify the PFAS removal efficiency of these kiln-specific iron-modified composites in complex water matrices to determine the most cost-effective and scalable production route.

References Hassan, M., Du, J., Liu, Y., Naidu, R., Zhang, J., Ahsan, M.A. and Qi, F. (2022) Magnetic biochar for removal of perfluorooctane sulphonate (PFOS): interfacial interaction and adsorption mechanism. Environmental Technology & Innovation. 28, 102593. Teng, B., Zhao, Z., Wu, J., Xia, L., Wang, Y., Cheng, J., Zhang, W. and Wang, H. (2025) Study on PFAS removal by different forms of iron-modified biochar: adsorption effects and catalytic activity. Journal of Environmental Chemical Engineering. 13(6), 120333.

ABSTRACT. Bamboo is a fast-growing, renewable lignocellulosic biomass that represents a highly attractive and sustainable feedstock for the production of functional carbon materials. In this work, untreated Dendrocalamus giganteus was converted into bamboo-derived activated carbons (BACs) via fast pyrolysis under an inert nitrogen atmosphere at temperatures ranging from 300 to 600 °C, followed by in situ CO₂ activation. This combined approach enabled a fine control over the structural, morphology, porosity surface, chemical and paramagnetic properties, such as permanent free radical (PFR) formation of the resulting biochars.

Comprehensive physicochemical characterization was performed using diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET) surface area analysis, electron paramagnetic resonance (EPR), and ATR-FT-IR spectroscopy. These techniques provided complementary insights into surface functional groups, elemental composition, electronic structure, porosity development, and carbon-centered radical as a function of thermal treatment.

Nitrogen adsorption–desorption measurements combined with Density Functional Theory (DFT) pore size analysis revealed a strong dependence of pore architecture on pyrolysis temperature. The material produced at 600 °C (B600) was predominantly microporous, with pore widths below 2 nm. In contrast, B500 exhibited a well-developed mesoporous network with pore sizes between 2 and 50 nm, while B400 displayed a macroporous structure with pore diameters exceeding 50 nm. These structural differences were identified as critical parameters for subsequent enzyme immobilization.

The biochars were then evaluated as solid supports for Candida antarctica lipase B (CaLB), an industrially relevant enzyme characterized by a highly hydrophobic surface. Enzyme immobilization occurred through a combination of surface adsorption and pore entrapment, with larger pores generally favouring higher enzyme loading. However, the results clearly demonstrate that immobilization efficiency is not dictated by pore size alone, but rather by a balance between surface chemistry, morphology, and accessibility. The immobilization process was monitored by Bradford assay, which showed a progressive decrease in free enzyme concentration in the supernatant and complete immobilization of the protein of interest on all supports after 24h.

The catalytic performance of immobilized CaLB was assessed using a model polycondensation reaction of 1,8-octanediol and dimethyl adipate, producing an aliphatic polyester with methanol as a by-product. Monomer conversion and polymer physio-chemical properties were analyzed by NMR spectroscopy and Gel Permeation Chromatography (GPC). High monomer conversions were achieved across all materials (98% for B400, 94% for B500, and 77% for B600) and substantial differences were observed in the obtained polymer molecular weight. B400 enabled the formation of polyesters with a number-average molecular weight of approximately 11 kDa, compared to 7.5 kDa for B500 and only 1.5 kDa for B600. These results indicate that macroporous biochars promote more favourable enzyme orientation and accessibility, whereas microporous structures impose steric constraints that limit polymer chain growth.

References: Pandoli, O; Catal. Sci. Technol., 2025,15, 6161-6178 https://doi.org/10.1039/D5CY00632E Pandoli, O; ChemCatChem, 2024, 16, https://doi.org/10.1002/cctc.202401042

ABSTRACT. Improving soil quality is essential for sustainable agriculture and long-term soil resilience. Biochar, a carbon-rich material derived from biomass pyrolysis, has shown great potential to enhance nutrient retention, microbial activity and soil carbon storage. Its effectiveness depends strongly on its physicochemical properties and the specific soil challenges it is intended to address. Many conventional biochar materials are not optimised for targeted functions and tailoring surface chemistry, and porosity can markedly improve performance in acidic, nutrient-poor or contaminated soils while supporting circular, low-input soil management and carbon storage strategies.

Preliminary experiments with unmodified biochar produced from pinewood (PWBC) and wheat straw (WSBC) evaluated their impact on soil properties and microbial activity. PWBC exhibited a high carbon content of 85.1%, suggesting strong potential for long-term carbon sequestration, while WSBC contained higher concentrations of essential nutrients. In 5% soil amendments, WSBC increased soil pH from 6.6 to 7.1, electrical conductivity from 300 to 570 µS cm⁻¹ and plant-available potassium from 289 to 849 mg L⁻¹. Microbial responses varied with feedstock and incubation time. Total heterotrophic bacterial counts declined by approximately three log units across all treatments after 30 days, while dehydrogenase activity in WSBC-amended soil peaked at nearly four times the control after 90 days, compared to a twofold increase under PWBC. These findings highlighted that nutrient-rich WSBC enhances short-term microbial activity and nutrient availability, whereas recalcitrant PWBC primarily contributes to stable carbon retention. Selected biochar samples were subsequently subjected to targeted chemical modification treatments to improve their surface chemistry, porosity and cation exchange capacity. Traditional chemical reagents, including sulphuric acid, hydrochloric acid, acetic acid and phosphoric acid, were used as benchmarks to evaluate modification effectiveness. Alongside these conventional treatments, the aqueous-phase pyrolysis liquid produced during the same process will be employed as a sustainable chemical modifier, offering a circular approach to biochar enhancement. Rich in organic acids and phenolic compounds, this by-product can functionalise biochar surfaces while reducing the need for external reagents and minimising waste. Key process variables such as mixing method, liquid concentration, contact time and post-treatment removal will be optimised to enhance biochar functionality for soil applications. This research aims to establish practical, scalable methods for producing biochar that maximises both its physicochemical performance and its contribution to soil health and climate resilience.

These laboratory findings will be taken forward into a scalable soil-improvement strategy. The modified biochar samples will be benchmarked against specific parameters and metrics (functional groups, porosity, cation exchange capacity and nutrient sorption. Their agronomic and biological effects will then be tested in controlled soil incubations (greenhouse and field trials), tracking pH buffering, plant-available nutrients, enzyme activities and shifts in microbial abundance over time. Direct comparison of aqueous-phase liquid modification with mineral-acid and organic-acid benchmarks will quantify whether the circular approach delivers equivalent or improved functionality with lower chemical inputs and reduced waste. The outcome will be practical guidance linking feedstock choice and modification route to specific soil constraints, supporting resilient, low-input soil management and long-term carbon storage.

ABSTRACT. Polypropylene (PP) accounts for roughly 20% of plastic waste streams [1] and remains difficult to recycle using conventional methods [2,3]. Conventional pyrolysis is widely used in polymer chemical recycling, yet polypropylene often yields broad product distributions and unsaturated/aromatic fractions under conventional thermal routes [3]. Tandem dehydrogenation and olefin cross-metathesis (TDOCM) has recently emerged as a mild, catalyst-directed pathway for polyethylene depolymerization [4–6]. This study reports the first documented catalytic degradation of polypropylene via tandem dehydrogenation and olefin cross-metathesis, employing a Pd/γ-Al2O3 catalyst for dehydrogenation in combination with a WOx/SiO2 catalyst for metathesis, with n-decane serving as co-reactant. Under mild conditions (300 °C and ~35 bar), complete PP conversion is achieved in 3 h, yielding predominantly saturated. PP was converted to liquid hydrocarbons (81 wt% liquid; 19 wt% gas), with no solid residue remaining after 3 h. After 1 hour, 17.5 wt% wax residues were recovered, and liquid and gas yields were reduced by 12 and 5 wt%, respectively. Gel permeation chromatography (GPC) confirmed PP depolymerization and reported a reduction in molecular weight – decreasing from 250,000 g/mol (feed; PDI = 3.73) to 995 g/mol (wax; PDI = 2.6). Liquid products comprised only alkanes and were dominated by branched iso-alkanes in the C8–C18 range, consistent with PP’s tertiary-carbon structure and retention of methyl substituents in fragments. The results differ from conventional pyrolysis, which produces fractions of unsaturated compounds and aromatics [3]. It was found that an excess of n-decane co-reactant suppresses polymer–polymer metathesis and β-scission pathways (minimizing wax and gas formation), whereas insufficient co-feed leads to increased yields of waxes and light gases [6]. Elevated pressures improved hydrogen retention and promoted saturation of intermediates, shifting the product distribution toward heavier alkanes. The method is effective across different PP feedstocks, including both virgin and recycled PP, fully converting them under these conditions. Overall, this application of tandem dehydrogenation and olefin cross-metathesis to polypropylene establishes a selective pathway for PP upcycling with high yields of liquid alkanes under mild operating conditions.

Proposed reaction scheme for the tandem dehydrogenation and olefin cross-metathesis (TDOCM) of polypropylene (PP) and n-decane.

1. Faraca and Astrup. Plastic waste from recycling centres: Characterisation and evaluation of plastic recyclability. Waste Manag. 2019, 95, 388–398. 2. Schyns and Shaver. Mechanical recycling of packaging plastics: A review. Macromol. Rapid Commun. 2021, 42, 2000415. 3. Huang et al. Chemical recycling of plastic waste for sustainable material management: A prospective review on catalysts and processes. Renew. Sustain. Energy Rev. 2022, 154, 111866. 4. Jia et al. Efficient and selective degradation of polyethylenes into liquid fuels and waxes under mild conditions. Sci. Adv. 2016, 2, e1501591. 5. Ellis et al. Tandem heterogeneous catalysis for polyethylene depolymerization via an olefin-intermediate process. ACS Sustain. Chem. Eng. 2021, 9, 623–628. 6. Kim et al. Metathesis, molecular redistribution of alkanes, and the chemical upgrading of low-density polyethylene. Appl. Catal. B Environ. 2022, 318, 121873.

ABSTRACT. The rapid global expansion of solar energy infrastructure has created critical environmental challenges, especially the management of end-of-life (EoL) photovoltaic (PV) modules. As these modules reach the end of their functional lifespan, recovering valuable constituents such as high-purity glass, silver, silicon, and aluminum becomes essential for a sustainable circular economy. However, the primary technical bottleneck lies in the "de-encapsulation" process, where the multi-layer structure protected by ethylene-vinyl acetate (EVA) and polyvinyl fluoride composite backsheet (TPT) is notoriously difficult to separate. Traditional inert pyrolysis often suffers from poor heat transfer and slow reaction rates. Based on these, this study proposed oxidative pyrolysis as a high-efficiency alternative. This study first utilized thermogravimetric analysis (TGA) to evaluate the pyrolysis characteristics and kinetic parameters of individual EVA and TPT components, as well as their mixtures, under both inert (N2) and low-concentration oxygen environments. The results indicated that the optimal oxygen concentration for achieving a stable, autothermal reaction ranges between 2% and 4%. Specifically, the pyrolysis of pure EVA occurred in two distinct stages (290–410 ℃ and 410–515 ℃), with the average activation energy (Ea) dropping significantly from 238.64 kJ/mol in N2 to 195.81 kJ/mol in 2% O2. Similarly, pure TPT pyrolysis occurred between 375–520 °C, with Ea values decreasing from 204.42 kJ/mol in N2 to 187.84 kJ/mol in 4% O2. The co-pyrolysis of EVA/TPT mixtures followed a two-stage process (290–410 ℃ and 410–525 ℃), where the Ea was recorded at 226.91 kJ/mol in 2% O2, compared to 253.04 kJ/mol in an inert atmosphere. A notable synergistic effect was observed during co-pyrolysis, where oxidative conditions lowered the energy barrier and shifted the maximum weight loss peak temperatures forward by 20–50 ℃. To understand the underlying chemistry, thermogravimetry-fourier transform infrared spectroscopy (TG-FTIR) was employed to monitor evolved gases and reaction pathways. In an inert atmosphere, decomposition followed sequential bond scission: EVA released acetic acid, CH4, and CO2, while TPT yielded HF and CO. In contrast, the introduction of oxygen fundamentally reshaped these pathways, as oxidation became the dominant mechanism. This shift suppressed the formation of alkanes and HF while significantly increasing CO2 evolution, suggesting that oxygen catalyzes the reaction by replacing slow hydrocarbon chain cleavage with direct oxidation. Furthermore, a unique "oxidative coupling effect" was identified in the mixed components. While synergy under inert conditions stemmed from the capture of EVA intermediates by TPT-derived radicals, aerobic conditions upgraded this interaction, resulting in CO2 yields that far exceeded those of individual components. Ultimately, oxidative pyrolysis offers a dual advantage by significantly reducing energy consumption through lower activation energy and ensuring more complete decomposition of organic components. This study elucidates the complex reaction kinetics and chemical pathways involved, establishing a crucial theoretical foundation for developing efficient, industrial scale recycling processes to address next generation solar waste sustainably.

ABSTRACT. Thermochemical conversion offers an efficient route for the high-value utilization of waste plastics; however, the intrinsic complexity of process control, the difficulty in tailoring product distributions, and the relatively high energy consumption continue to hinder further technological advancement. Centered on the core scientific challenge of green, low-energy, and selective conversion of waste plastics, this study establishes a microwave-enhanced thermochemical conversion framework and systematically elucidates the regulatory roles of microwave fields in plastic cracking pathways, interfacial polarization behavior, and product distribution. In addition, microwave-responsive zeolite catalysts with hierarchically ordered macro–meso–microporous architectures have been developed, leading to pronounced improvements in target-product selectivity and catalyst lifetime. By constructing a microwave-responsive interfacial reaction microenvironment, precise energy coupling and synergistic intensification of PET depolymerization are achieved, advancing polyester chemical recycling toward high-value, high-efficiency, and environmentally benign pathways. Furthermore, an efficient heat-carrier utilization strategy is proposed, and a hybrid down-flow microwave pyrolysis reactor is developed and validated at the pilot scale. Collectively, this work provides critical theoretical foundations and enabling reactor technologies for the selective conversion of waste plastics into high-value chemicals.