Solar-driven low-rank coal gasification technology offers both significant carbon reduction potential and the capability to store intermittent solar energy. Enhancing the efficiency of solar-to-fuel energy conversion remains the core bottleneck for large-scale application of this technology. The unclear structural evolution mechanism of pyrolytic coke under high-intensity irradiation has constrained the optimization of solar reactors and the improvement of efficiency. This study combined in-situ online gas analysis and ex-situ characterization of coke physical-chemical structure to systematically reveal the coke evolution mechanism during solar pyrolysis and its impact on the reaction reactivity for further gasification. Compared to conventional pyrolysis, excessively rapid heating rates of the initial solar pyrolysis result in reduced stacking height and increased interlayer spacing, impeding the orderly stacking of coke microcrystals. This process leads to the formation of a coke structure rich in mesopores with high gasification reactivity. The effects of the later pyrolysis stage at the macroscopic and microscopic levels are illustrated as the destruction of the coke pore structure and the enhancement of lateral growth in the aromatic ring system, respectively. This conversely reduces the gasification reactivity, with both the surface area and pore volume decreasing. As heat flux density increased, the gasification reactivity of coke first rose and then decreased. It was determined by the competitive effects between the development of active porous structures in the initial pyrolysis and the later evolution of inert ordered structures under high heat flux density. This study establishes a theoretical foundation analysis of the gasification mechanisms of solar-driven low-rank coal.

Nitrogen-doped biochar is a promising carbon-based material for catalysis and adsorption. While previous studies emphasized performance enhancement, the structural evolution during pyrolysis and its impact on carbon stability and activity remain unclear. This study explores how urea modification affects the composition, surface functional groups, and defect structures of poplar-derived biochar. Through thermal oxidation, dichromate oxidation, and persulfate activation tests, the role of nitrogen in oxidation resistance and catalytic behavior was revealed. Results show that N-doping increases fixed carbon and volatile content, elevates the H/C and O/C ratios, reduces C-O groups, and enhances N-containing and aromatic functional groups. Between 350 similar to 550 degrees C, thermal oxidation stability improved by 5.3 % on average, attributed to N-facilitated deoxygenation and aromatic condensation. Beyond 550 degrees C, however, chemical stability slightly decreased due to pyrrolic-, pyridinic-, and quaternary-N enhancing oxidation reactivity. Catalytic activity showed contrasting effects: suppressed at 350 similar to 550 degrees C possibly by site blocking, but significantly enhanced at 750 similar to 950 degrees C, with UABC950 achieving a 98 % rhodamine B degradation within 5 mins. These findings provide insights into the carbon sequestration potential and functional applications of N-doped biochar.

Waste plastics pose significant environmental challenges and require effective management strategies. Catalytic pyrolysis offers a promising route for converting waste plastics into high-value carbon nanotubes (CNTs), thereby enabling cleaner and circular carbon material production. In this study, a series of Fe/Al2O3 catalysts modified by chelating agents were developed using ethylenediamine (EDA), ethylenediaminetetraacetic acid (EDTA) and hydroxyethyl ethylenediaminetriacetic acid (HEDTA). An acid-washing process was also employed during the preparation of the Fe/Al2O3 catalysts. The addition of chelating agents effectively enhanced the dispersion of catalyst particles, improving the yield and characteristics of CNTs from pyrolysis of polypropylene (PP) plastics. Among them, EDA and HEDTA suppressed particle agglomeration and reduced the average CNT outer diameters to 15.9 nm and 15.2 nm, respectively. In contrast, EDTA led to the highest CNT yield of 280 mg/gPP, but resulted in a larger average diameter of 19.1 nm due to the weakened metal-support interaction (MSI) associated with its strong chelating effect. H2-TPR and ICP-OES analyses further confirmed that the incorporation of chelating agents effectively weakened the MSI, suppressed the formation of FeAl2O4 and improved Fe dispersion. It was also revealed that Fe3C may constitute the catalytically inactive phase, as indicated by the inverse correlation between the Fe3C particle size and the average CNT diameter. After acid washing, the CNT yield of Fe(A) increased to 315 mg/gPP. While Fe(A)*, EDTA* and HEDTA* increased the average CNT diameter, EDA* exerted negligible influence. Following purification, the carbon material derived from EDTA exhibited a high electrical conductivity of 17080 S/m at 30 MPa, significantly surpassing that of commercial CNTs (8177 S/m). Furthermore, Raman spectra showed that the ID/IG and IG'/IG ratios of Fe(A) were 0.73 and 0.58, respectively, while those of FeEDA*, FeEDTA* and HEDTA* were 0.49/0.82, 0.49/0.88 and 0.46/0.85, respectively. This process demonstrates a cleaner and efficient route for converting plastic waste into functional carbon nanomaterials. The findings provide a potential sustainable solution for plastic valorization and circular carbon material production.

Pyrolysis mechanisms of nitrogen (N)-containing plastics hold significant importance for recovering high-value fuels and chemicals from real plastic waste, whereas current insights remain unclear. This work systematically investigated the pyrolysis behaviors, volatile release characteristics, and backbone decomposition mechanisms of polyamide 6 (PA6), thermoplastic polyurethane (TPU), and polyacrylonitrile (PAN) through integrating TGFTIR-GC/MS and density functional theory (DFT). Kinetic analysis based on Coats-Redfern and Achar methods suggested a higher average activation energy of PA6 (228 kJ/mol) compared to TPU (94 kJ/mol) and PAN (189 kJ/mol). PA6 pyrolysis predominantly produced c aprolactam (92.01 %) at 481 degrees C through the nucleophilic attack of terminal amino group on adjacent amide structure, forming a four-membered transition state with a free energy barrier of 217.0 kJ/mol. Owing to the lower bond dissociation energies (BDEs) of the acyloxy bonds in urethane groups compared to the alkoxy bonds in polyester structures, the hard and soft segments of TPU occurred sequential cracking at 358 and 448 degrees C, releasing 4,4'-diphenylmethane diisocyanate (85.12 %) and cyclopentanone (69.12 %), respectively. PAN backbone preferentially cleaved at mid-chain C-C bonds with lower BDEs, forming acrylonitrile dimer and monomer fragments, which coupled with each other and combined with hydrogen radicals to generate abundant NH3 and fatty nitriles like 2-methylglutaronitrile, 1,3,6-hexanetricarbonitrile, and acrylonitrile. These findings elucidated the intrinsic connection between pyrolysis volatile evolution and backbone degradation mechanisms of N-containing plastics at the molecular level, thereby offering theoretical guidance for optimizing the pyrolysis process of real plastic waste to prepare high-value products.

Potassium is extensively recognized as an effective catalyst promoter in thermocatalytic CO2 hydrogenation, however, its involvement in photothermal catalytic systems, and, more importantly, its working mechanism, remains largely unexplored. Herein, a series of MOF-derived CoFeZn catalysts with systematically varied potassium contents were synthesized to elucidate the role of potassium in photothermal catalytic CO2 hydrogenation. Advanced in situ characterizations, particularly a customized mass spectrometry (MS) setup, reveal that potassium synergistically couples with light irradiation to simultaneously enhance CO2 activation, suppress excessive hydrogenation, and modulate the kinetics and spatial distribution of photo-excited hot electrons, thereby shifting the reaction from thermally strong hydrogenation to thermally-photochemically regulated C-C coupling pathways. Optimization of potassium promoter achieved an impressive C2-C4 hydrocarbon production rate of 2.26 mmol center dot g- 1 center dot h- 1 in a flow-type reactor, nearly a twofold enhancement compared with the dark reaction and 1.74 times that of promoter-free catalyst, while maintaining excellent stability. This study unveils a synergistic interaction between potassium and light, establishing potassium as a multifunctional promoter for pathway-selective, solar-driven hydrocarbon production from CO2.

Torrefaction has been established as an effective method for enhancing the quality of biomass fuel. However, systematic research on the release mechanisms of chlorine and nitrogen during the torrefaction process remains relatively limited. To address this gap, this study investigated the release characteristics and conversion behavior of chlorine and nitrogen during biomass torrefaction under varying atmospheres and temperatures. It was found that chlorine was predominantly converted to chloromethane (CH3Cl) and hydrogen chloride (HCl), with conversion rates increasing monotonically with temperature. At 300 degrees C under N2 torrefaction, the conversion rates were 36.18% and 19.22%, respectively. Compared with N2, CO2 torrefaction enhanced the conversion of chlorine to CH3Cl and HCl, with conversion rates increasing to 38.98% and 20.67% at 300 degrees C, respectively. Nitrogen was primarily released as nitric oxide (NO) and hydrogen cyanide (HCN), with NO emissions were significantly higher than those of HCN. Correspondingly, the conversion rates of nitrogen to these two gaseous products also rose with increasing temperature, reaching 13.12% and 1.43% at 300 degrees C under N2 torrefaction. When CO2 was used for torrefaction, the conversion of nitrogen to NO was promoted only when the temperature exceeded 240 degrees C, and this effect became more pronounced with increasing temperature. However, the generation rate of HCN gradually decreased under these conditions. These findings clarify the coupled effects of temperature and atmosphere and support the selection of optimal conditions to improve fuel quality and mitigate downstream chlorine and nitrogen-related risks.

Potassium additive could effectively upgrade the product portfolio of biomass pyrolysis, leading to highly porous biochar, hydrogen, and phenolic compounds. Shedding light on the effects of temperature is essential for balancing the costs and yields of biomass pyrolysis. In this study, K2CO3-assisted pyrolysis of bamboo was investigated at temperatures of 320~800 °C and the dosage of 1 mmol/g (~6.9 wt.% K), and the pyrolysis products were comprehensively characterized. Results show that 450°C is the temperature favourable for phenol precipitation, potentially corresponding to the substantial formation of phenol-potash structures. As the temperature rises to 800°C, the decomposition of K2CO3 or its reaction with biochar results in a 16 wt.% decrease in liquid yield and a 4 wt.% reduction in solid yield, while gas yield increases by 40 wt.%. Furthermore, K2CO3 facilitates biochar formation by enhancing ring opening, aromatization, debranching, and cross-linking. Meanwhile, defects, mainly 5-membered rings, are also promoted by K2CO3, resulting in porosity development, and the aromatic skeleton grows with hydrogen evolution. This study provides deepened insights into the potassium effect on biochar skeleton through a comprehensive study, which may alter the common sense on the porosity development of biochar with potassium additive.

Catalytic co-pyrolysis of plastic waste with waste cooking oil (WCO) shows potential for producing sustainable aviation fuel (SAF)-range aromatic hydrocarbons. However, the influence of plastic feedstock characteristics on this process remains unclear. In this study, the impacts of plastic chemical structure, physical morphology, and actual composition on product selectivity were investigated, employing a multi-system experimental design that encompasses virgin polymers, common plastics, metallized packaging, and mixed plastics. Results indicate a high selectivity for SAF components, with C8-C16 compounds accounting for 65.29%-70.09% of the liquid oil across different real-world plastics. In polyolefin polymers, high-density polyethylene's linear chains promote reactions between its alkane radicals and oxygenated radicals from WCO to form monocyclic aromatic hydrocarbons (MAHs), with a content of 81.08% (theoretical 73.67%). The high specific surface area and additives of real-world polyolefin plastics enhance interfacial contact with WCO, accelerating pyrolysis rates and MAHs formation. For aromatic-containing polymers, WCO-derived olefins undergo alkylation with their benzylic radicals, thereby promoting the formation of bicyclic aromatic hydrocarbons. Specifically, WCO acts as a hydrogen donor for hydrogen-deficient polyethylene terephthalate (PET), significantly suppressing char formation. The high specific surface area and composition of real-world PET plastic further enhance this effect, elevating liquid oil yield to 48.13% (theoretical 40.10%). In multicomponent real-world plastic systems, WCO serves a dual role: it provides hydrogen to suppress PET coking while promoting polyolefin aromatization. Concurrently, hydrogen-rich polyolefins donate hydrogen to deficient components, collectively optimizing the product distribution. This study provides insight into converting plastic waste and WCO to valuable fuel.

Efficient tar conversion is essential for reliable biomass gasification and downstream hydrogen production. Yolk-shell catalysts, which confine active metals within an inert shell, show strong resistance to sintering and carbon deposition during tar reforming, but their catalytic efficiency still requires improvement. In this work, promoter-modified yolk-shell Ni@SiO2 catalysts incorporating Zr, Ce, and Fe were developed for the steam reforming of toluene as a model tar compound. Among the promoters, Ce showed the most significant enhancement, achieving 100% toluene conversion at 650 degrees C and a steam-to-carbon ratio of 2, with stable performance maintained for 60 h of continuous operation, outperforming the Fe- and Zr-doped catalysts. Mechanistic studies showed that Ce promotion enhanced both activity and stability. TPD-MS results suggested that the introduction of Ce increased the concentration of oxygen vacancies, which promoted H2O adsorption on Cerelated sites while preserving metallic Ni sites for toluene activation. Meanwhile, the cracking and reforming temperatures decreased from 315 degrees C and 398 degrees C to 220 degrees C and 262 degrees C, respectively. In situ DRIFTS identified benzyl alcohol, benzoic acid, and maleic acid as key surface intermediates. These results demonstrate that combining yolk-shell confinement with Ce-induced oxygen vacancy engineering is an effective strategy for stable tar reforming.

This study aims to investigate the influence of the thermochemical conversion behavior of microalgae pellet in molten hydroxide salts(80％NaOH-20％Na2CO3)on hydrogen production.By comparing the temperature evolution,gas release characteristics,and structure evolution of pellet with and without molten salt,and combining with char alkalization experiments,the regulatory mechanism of molten salt on the reaction pathways and hydrogen production behavior of microalgae pellet was systematically analyzed.The results indicate that the molten salt significantly enhances the internal heat transfer efficiency of the pellet,with a central heating rate reaching 177 ℃/s,effectively alleviating thermal hysteresis.Meanwhile,the molten salt promoted pellet pore development through penetration,erosion,and catalytic effects,resulting in a porosity increase of 53.2％-104.3％after 10 s of reaction.It also significantly enhanced the conversion efficiency,with the dominant reaction pathway shifting to char gasification after only 70 s.Furthermore,when the heating rate was increased above 600℃,the hydrogen yield from char alkalization improved more markedly,primarily attributed to the synergistic promotion effect of the molten salt's catalytic effect and the rapid heating process on the volatiles reforming.This study provides a theoretical foundation for a deeper understanding of the mechanisms behind efficient hydrogen production from biomass in molten hydroxide salts.

Agricultural soils are a significant source of nitrous oxide (N2O) emissions. The application of biochar to soil offers a synergistic approach to establishing stable organic carbon (C) storage while reducing greenhouse gas (GHG) emissions, particularly through effective reductions in N2O emissions. However, current biochar application strategies often lack consideration of locally tailored application rates and biochar properties, limiting its N2O mitigation potential. Here, we conduct a spatially explicit analysis to investigate the N2O mitigation potential of straw-derived biochar in China's croplands, exploring optimal application strategies under both ideal and realistic conditions. The key drivers that influence the spatial patterns of straw-derived biochar's mitigation potential and application strategies are also revealed. We find that applying biochar with optimal strategies could avoid approximately 50% and 36% of nationwide cropland N2O emissions under ideal and realistic conditions, respectively. The optimal biochar application rate and properties required to achieve the maximum N2O reduction potential exhibit significant spatial variability, differing among biochar types. Key factors determining the optimal biochar application rate in various regions include N fertilizer application rates and soil organic carbon (SOC) content, while water input-including precipitation and irrigation water input-is the primary factor determining the optimal biochar properties. These findings may inform the development of site-specific biochar application strategies aimed at enhancing the N2O mitigation efficacy in croplands across China.

ABSTRACT Establishing correlations between processing parameters, structural characteristics, and application performance are essential for controlled synthesis of biomass‐derived graphene‐like carbon via flash Joule heating (FJH). Herein, we developed a controlled dual‐phase synthesis strategy in which pre‐pyrolysis stabilizes the carbon framework and programmable FJH subsequently tailors the carbon architecture for different application scenarios. By decoupling the thermodynamic driver (current) from kinetic relaxation (duration), a processing structure phase‐map framework was established to capture and guide the continuous transition from defect‐rich amorphous carbon to highly ordered turbostratic nanographite (TNG). This strategy reduces the reliance on empirical trial‐and‐error. As a demonstrative application for the high‐graphitization regime, targeted TNG exhibited a peak electrical conductivity of 59.06 S cm −1 . Incorporating 1.2 wt.% TNG into epoxy resin increased the flexural modulus by 2.8‐fold and enhanced thermal conductivity, demonstrating the link between programmed structural evolution and macroscopic performance. This strategy offers a route for converting heterogeneous waste biomass into structurally tunable carbon materials.

In this study, Fe-modified Al2O3 catalysts were synthesized for furfural production from microwave-assisted pyrolysis of cellulose in a fixed-bed reactor. The effects of iron chlorides, catalyst-to-cellulose mass ratio, pyrolysis temperature, and microwave heating modes on furfural selectivity in bio-oil were investigated. It shows that the FeCl3 loading of 0.25mmol/g on Al2O3 can increase the weak acid sites, which is conducive to furfural formation. With the increase of the catalyst addition ratio and reaction temperature, the selectivity of furfural first increased and then decreased. Cellulose contacting with SiC directly can increase the furfural selectivity by 79% during in-situ catalytic pyrolysis compared to contacting with quartz sand. The considerable furfural selectivity of 33.74% was obtained under microwave-assisted in-situ catalytic pyrolysis at 400 °C with the catalyst-to-cellulose mass ratio of 4:1 and an FeCl3 loading of 0.25mmol/g on Al2O3. The possible catalytic pyrolysis mechanism for furfural production was proposed: the weak acid site in FeCl3-derived/Al2O3 promoted the decomposition of the sugars into furans, aldehydes and ketones; the synergistic effect between microwave hotspot and suitable amounts of FeCl3-derived/Al2O3 might promote the formation of fewer aldehydes and ketones towards more furans and acids, and meanwhile reduce the competitive reaction that produced less 2,5-dimethylfuran, 2-methylfuran and 2,3-benzofuran, thereby further enhancing the selectivity of furfural. This study can help guide high-selectivity furfural production from cellulose over the economical catalysts in a fixed-bed reactor.