Catalytic pyrolysis is an important route for the high-value conversion of biomass. Feedstock pretreatment combined with catalytic pyrolysis is an effective strategy to regulate product distribution and improve bio-oil quality. In this study, corn stover underwent enzymatic hydrolysis pretreatment for varying durations to break down its dense structure and partially degrade cellulose and hemicellulose. Hierarchical ZSM-5 catalysts with varying porosities were also prepared to synergistically upgrade bio-oil and enrich high-value-added products such as aromatics. The results show that an appropriate enzymatic hydrolysis duration facilitates hemicellulose removal, reduces cellulose crystallinity, and exposes lignin, thereby promoting pyrolysis. Notably, both monocyclic aromatic hydrocarbons (MAHs) and phenolic compounds after combined pretreatment and catalytic pyrolysis increased to varying degrees, indicating that the coupling strategy strongly promoted the release and retention of phenolic products. When the enzymatic hydrolysis duration was 4 h, combined with catalytic pyrolysis over microporous ZSM-5, the MAHs yield reached 1.05 times that of direct catalytic pyrolysis of raw corn stover, while the phenol yield reached 1.97 times that of the direct catalytic pyrolysis. The hierarchical porous structure enhances the mass transfer and diffusion of macromolecular species within catalyst pores. Compared with ZSM-5 catalyzed pyrolysis of raw corn stover, the pyrolysis of corn stover pretreated for 4 h over hierarchical 0.3MZ catalyst led to a more pronounced increase in MAHs yield, reaching 3.11 times that of corn stover pyrolyzed over microporous ZSM-5. In addition, the phenolic compound yield was also significantly enhanced, confirming that the coupling strategy achieves simultaneous enrichment of both aromatics and phenols in bio-oil. This study lays a theoretical foundation and offers technical support for the high-value-added utilization of biomass resources.
Catalytic pyrolysis of lignin into benzene, toluene, and xylene (BTX) provides a promising route for producing renewable aromatic chemicals from industrial biomass residues. However, the rational design of highly efficient zeolite-based catalysts remains challenging due to the complex structure of lignin and the strong dependence of product selectivity on catalyst properties. In this study, Fe-modified HZSM-5 catalysts were prepared using sulfate, nitrate, and chloride precursors to elucidate the role of precursor anions in regulating Fe dispersion, textural properties, acidity, and catalytic performance during lignin pyrolysis. The results showed that Fe incorporation preserved the MFI framework while generating secondary mesoporosity and markedly increasing Lewis acidity, leading to a decrease in the Brønsted/Lewis acid site ratio from 3.07 for parent HZSM-5–0.18–0.83 for the Fe-modified samples. Among the catalysts investigated, Fe0.70-Cl/HZSM-5 exhibited the highest BTX relative abundance at 550 °C (69.9%), compared with Fe0.70-S/HZSM-5 (67.2%), Fe0.70-N/HZSM-5 (56.9%), and parent HZSM-5 (41.7%). At 600 °C, Fe0.70-S/HZSM-5 also showed the highest BTX relative abundance (65.3%) than other catalysts, indicating its superior stability over the temperature range of 550–600 °C. In-situ DRIFTS of guaiacol and lignin revealed the progressive removal of methoxy and hydroxyl groups while preserving the aromatic framework. These findings suggested a sequential reaction pathway in which Lewis-acidic Fe sites promoted the activation and deoxygenation of oxygen-containing functionalities, followed by Brønsted-acid-catalyzed cracking, hydrocarbon-pool reactions, and aromatization within the zeolite channels. This study demonstrated that precursor-anion engineering was a simple and effective strategy for tuning the acidity of metal-modified zeolites toward selective lignin valorization to BTX.
The main objective of this study was to produce bio-oil more quality and lower cost through catalytic pyrolysis of castor oil (non-edible) fruit using calcined dolomite catalyst at different ratios (5–25% by weight). In studies of catalyst-free (non-catalytic mode) pyrolysis conducted at different temperatures between 400 and 600°C, the highest yield of liquid product, approximately 61.71%, was obtained at 550°C, and it was also determined that this product contained 60.69% organic phase and 39.31% aqueous phase. For the catalytic pyrolytic liquid, an optimum yield of 56.90% by weight was obtained at 550 °C and a catalyst ratio of 10% calcined dolomite, and the resulting product consisted of approximately 50% aqueous phase. Compared to non-catalytic bio-oil, catalytic bio-oil does not contain C18-C20 carbon number hydrocarbons found in lubricating oils; it also contains less kerosene and diesel, but approximately equal amounts of gasoline. Furthermore, it also has a lower acid and olefin content. Additionally, it was found that calcined dolomite showed a strong improvement effect on the fuel properties of catalytic bio-oil compared to non-catalytic bio-oil in terms of viscosity (52.53% reduction), oxygen content (27.57% reduction), density, API density, and calorific value. In conclusion, it is predicted that, thanks to its improved fuel properties, blending the catalytic bio-oil, after its further improveming, with various commercial fuels can significantly reduce commercial fuel consumption and costs.
The catalytic co-conversion of biomass and plastic waste can enable the simultaneous production of a hydrogen-rich gas and valuable carbon materials, such as carbon nanotubes (CNTs), carbon nanofibers (CNFs), and porous carbon. Gas upgrading, carbon recovery, and catalyst stability can impose competing requirements. This structured narrative review critically compares catalytic co-pyrolysis, downstream reforming, co-gasification, and microwave or plasma-assisted conversion, linking feedstock characteristics, catalyst properties, reactor design, and product quality. Acid sites tend to promote cracking, deoxygenation, and aromatization, while appropriate transition-metal sites aid reforming, dehydrogenation, and filamentous carbon growth. Ni-Fe formulations offer complementary catalytic activities, and staged reactors allow independent control of primary decomposition and subsequent conversion. The success of these approaches depends on catalyst state, support properties, feed composition, and operating conditions. Adding steam and CO2 can enhance gas production while consuming deposited carbon, creating a trade-off between gas upgrading and carbon recovery. Within each process category, reported performance values are compared, with hydrogen yield distinguished from gas concentration and total carbon deposition separated from the yield of recovered functional carbon. Hydrogen yields are harmonized on a common feed-mass basis where the reported data permit; unit normalization alone does not establish experimental comparability. Effective carbon valorization requires assessing morphology, structure, purity, recovery yield, and application-specific performance. Industrial viability also depends on catalyst lifetime, hydrogen purification, carbon separation, energy demand, and life-cycle impacts. This analysis outlines the conditions under which hydrogen and carbon can be co-produced. It identifies priorities for sustained performance, but inconsistent reporting and limited matched comparisons prevent statistically sound rankings of catalysts or reactor configurations.
This study investigates the intrinsic relationship between the caking properties and organic structural evolution of blended coals with varying mass ratios of high-caking coal (HC) to non-caking coal (NC), aiming to provide theoretical guidance for the formulation of carbonaceous reducing agents in industrial silicon smelting. X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) spectroscopy were employed conjointly to characterize the microcrystalline structure and functional group variations of blended coal systems subjected to thermal treatment from 25 °C to 500 °C. The results indicate that, with increasing temperature, the (002) diffraction peaks of all blended coals gradually sharpen, yet fail to develop into fully symmetric narrow profiles, suggesting limited ordering of the aromatic carbon layers. The organic macromolecular framework undergoes differential modifications, remaining predominantly in the form of non-equilibrium structures bearing aromatic moieties. Correlation analyses, combined with curve-fitted infrared spectral parameters, reveal that the aromatic structure, oxygen-containing groups, aliphatic skeleton, and hydroxyl functionalities are most notably influenced by 4H-substitution, aliphatic C–O stretching, –CH deformation, and OH–π interactions, respectively. Among these, the aromatic C–H bond exerts the most significant effect on the caking index across all blending ratios. Furthermore, rising temperature and an increasing NC proportion promote an increase in the proportion of aromatic C–H configurations corresponding to 4 H substitution, which may be associated with the formation of partially hydrogenated aromatic structures and an elevated degree of aliphatic chain branching, collectively leading to a progressive decline in the caking index. These findings offer a mechanistic basis for the efficient utilization of low-rank non-caking coals in silicon-producing electric arc furnaces.
