Comparative catalytic pyrolysis of wheat straw for enhanced bio-oil production

Upcycling lignocellulosic biomass using a radial-axial fixed-bed ex-situ catalytic pyrolysis reactor.

This study investigated the conventional fixed-bed catalytic pyrolysis using metal oxides (CaO, Fe₂O₃, and TiO₂) to enhance bio-oil yield from three lignocellulosic biomasses: safflower press cake (SPC), coconut press cake (CPC), and coconut shell (CS). The primary characterization, using ultimate, proximate, and compositional analyses, as well as TGA-DTG-DSC, was carried out in the experiment. SPC biomass had a high hemicellulose content (50.8 ± 0.11%), which is suited for bio-oil applications. An initial non-catalytic pyrolysis experiment was conducted at 550°C with a heating rate of 25°C/min for 30min; the bio-oil yields were 34% (SPC), 29% (CPC), and 26% (CS), respectively. During the catalytic pyrolysis, TiO₂ showed its strongest catalytic activity, primarily combined with SPC biomass. Under optimized conditions 550°C, 25°C/min heating rate, and a 30-minute reaction time SPC with TiO₂ yielded a maximum bio-oil output of 71.75 ± 0.16%. In contrast, under the same conditions without a catalyst, SPC produced 34 ± 0.16% bio-oil, indicating a significant 37.5% improvement with the addition of TiO₂. Among the three biomasses, SPC showed the greatest responsiveness to catalytic enhancement, while CPC offered a better balance between oil quality and char usability. The GC-MS analysis of TiO₂-catalyzed SPC bio-oil confirmed TiO₂'s selective catalytic influence on bio-oil compound distribution by revealing a predominance of phenolic compounds, such as Guaiacol (19.8%), 2,4-Dimethoxyphenol (31.12%), and hydroxy ketones such as -Hydroxy-2-butanone (29.49%) and 1-Hydroxypropan-2-one (26.36%), confirming the superior Lewis acid catalytic mechanism of TiO₂ for the production of phenolic compounds and ketone - rich bio-oil from lignocellulosic agro-industrial wastes.

Catalytic pyrolysis has emerged as a promising approach for converting waste plastics into high-value-added chemicals and fuels. This study aims to investigate the effect of calcination temperature on the catalytic performance of FeCoOx/Al2O3 catalysts for high-density polyethylene (HDPE) pyrolysis and to optimize the catalyst preparation conditions for maximizing valuable product yields. FeCoOx/Al2O3 catalysts were synthesized via a hydrothermal method and calcined at various temperatures (300–700 °C). The results demonstrate that calcination temperature significantly influences product distribution: gas yield increased with rising calcination temperature, whereas carbon yield, hydrogen yield, and hydrogen content decreased accordingly. Among all tested temperatures, the catalyst calcined at 500 °C achieved the optimal performance, yielding solid carbon at 23.0 wt. % with a hydrogen content of 80 vol.%. This superior performance can be attributed to its larger specific surface area, a richer pore structure, and better reducibility compared to those calcined at higher temperatures, which also facilitated the formation of solid carbon with the highest degree of graphitization and purity. This work provides technical guidance for the high-value utilization of waste plastics through catalytic pyrolysis.

Global solid waste management and climate-relevant innovations: A scientometric assessment (2014–2024)

High-value utilization of biomass pellets: Paradigm shift from alternative fuel to multifunctional chemical platform—A review

Porous activated carbon-based solid acid catalysts (AC‑SACs) have gained significant attention as promising materials for biomass conversion due to their high surface area, tunable porosity, and strong acidic functional groups. Biomass conversion is essential for the sustainable production of biofuels, including biodiesel, and other value‑added chemicals, offering an alternative to fossil-based resources. This review summarizes recent advances in the synthesis, characterization, and catalytic performance of AC‑SACs, emphasizing their role in key biomass conversion reactions such as hydrolysis, dehydration, esterification, transesterification, and catalytic pyrolysis. Synthesis strategies encompassing biomass pretreatment, carbonization, activation, and subsequent sulfonation or other functionalization methods are discussed in relation to their impact on hierarchical pore architecture, surface chemistry, and Brønsted/Lewis acidity. The review also examines primary deactivation mechanisms of AC‑SACs-such as -SO3H leaching, chemical derivatization of acid sites, and thermal degradation-and highlights regeneration strategies and design principles for improving long‑term stability. Future research directions are proposed, focusing on enhancing functional group stability, integrating regeneration into process design, and expanding AC‑SAC applications in sustainable chemical processes. The findings underscore the potential of AC‑SACs as versatile and environmentally friendly catalysts for biomass valorization and green chemistry applications.

Physics-informed machine learning prediction of char mass evolution in the catalytic pyrolysis of polyetherimide/graphite nanocomposites

Unlocking the natural acid-base bifunctionality of steel slag for catalytic pyrolysis of biomass to hydrocarbons

Sewage sludge catalytic pyrolysis toward high-value nitrogen-containing compounds: Combined Py-GC/MS and fixed-bed investigation

This study investigates the microwave-assisted catalytic pyrolysis of polyetherimide (PEI). Activated carbon (AC), petroleum coke, graphite, silicon carbide, and AC-supported oxides (Fe₃O₄, Fe₂O₃, Al₂O₃, and ZnO) were chosen as microwave absorbers and/or catalysts to determine the impact of microwave absorber/catalyst type on the decomposition. Experiments were conducted at a microwave power of 400 W, which corresponded to an average bulk temperature of 400 °C, for 10 min in an argon atmosphere. No PEI remained intact after the treatments and the products were in the gas, liquid, wax, and solid phases, with the gas phase being the dominant fraction. Decomposition with the AC–Fe₃O₄ catalyst resulted in the highest gas yield and hydrogen production of up to 20 mmol g⁻¹ PEI, corresponding to 76% of the hydrogen content of PEI. Decomposition without metal oxides produced more wax, whereas metal oxides shifted the product distribution toward gases and/or aromatic condensates (notably toluene), depending on the oxide. The catalysts were deactivated by carbon deposition, degradation of the carbon support and/or reduction of metal oxide species. These results demonstrate that microwave-assisted catalytic pyrolysis of PEI enables hydrogen generation and the recovery of aromatic hydrocarbons (e.g., toluene, styrene, and naphthalene), highlighting its potential as a chemical recycling route for high-performance thermoplastics. • Microwave-assisted PEI decomposition achieved complete polymer conversion. • AC–Fe₃O₄ combined microwave absorption with high H₂ yield from PEI. • Catalyst choice controlled H₂ and aromatic recovery from PEI decomposition.

The catalytic upgrading of biomass-derived compounds in zeolites such as ZSM-5 remains poorly understood at a molecular level, particularly with respect to adsorption and confinement of trapped species. Guaiacol, a key product of catalytic fast pyrolysis of lignocellulosic biomass, exhibits complex behaviour in ZSM-5, yet direct experimental evidence of zeolite-guaiacol host–guest interactions has been lacking. Here, we directly identify distinct in-pore and ex-pore guaiacol species in adsorbed ZSM-5 and trapped unreacted species following catalytic upgrading. These species are distinguished using 1H and 13C magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy differentiating through characteristic differences in chemical shifts, linewidths and relaxation data observables, and are complemented by thermogravimetric analysis coupled with mass spectrometry (TGA-MS) to reveal differences in their desorption profiles. Furthermore, 17O isotopic enrichment of the ZSM-5 framework enables two-dimensional 1H–17O dipolar heteronuclear multiple-quantum coherence (D-HMQC) NMR experiments, providing molecular-level insight into the through-space interactions between guaiacol and framework oxygen atoms. Together, these results suggest the location, confinement and reactivity of guaiacol within ZSM-5 pores, offering atomic-scale observations for the rational design of future zeolite catalysts for sustainable fuel production.

ABSTRACT Healthcare derived polystyrene waste represents a growing and under addressed fraction of plastic waste streams due to contamination risks and limited recyclability. This study aims to investigate the valorization of waste polystyrene foam through catalytic and noncatalytic pyrolysis pathways to evaluate product yield distribution and identify the dominant chemical compounds formed under different reaction conditions. We introduce a novel, low‐cost catalytic pyrolysis strategy based on a thermally fused iron(II) sulfate‐boric acid composite catalyst (FBOC‐C) designed to enhance liquid fuel recovery under simple distillation mood reactor separation. Systematic temperature and residence time optimization has identified 500°C and 30–45 min as optimal conditions for efficient depolymerization. Compared to noncatalytic and single catalytic systems, the composite catalyst achieved the highest liquid yield of 91.3%, with markedly reduced residue to 8.3% and gas formation of 0.4%. Fractional distillation demonstrated superior volatility control, with enhanced recovery of fuel relevant reaction across 80°C–360°C. GCMS analysis confirmed a progressive increase in aromatic selectivity from noncatalytic (78.83%) to FBOC‐C catalyzed oil (93.02%). Structural and morphological characterization (XRD, SEM, EDX, and TGA) revealed a hybrid crystalline amorphous catalyst architecture responsible for synergistic redox acidic interaction that suppresses secondary polymerization and excessive cracking. Unlike conventional zeolite or noble metal‐based systems, this approach integrates economical catalyst synthesis with simple pyrolytic distillation, offering a scalable and energy efficient pathway for high yield fuel production from healthcare polystyrene waste.

Catalytic pyrolysis of lignin, the most abundant natural aromatic polymer, offers a route to obtain value-added products with a low carbon footprint. In such a process, the lignin structure undergoes decomposition through an intricate network of reaction routes. Despite the use of model compounds to gain insights into the decomposition pathways, the formation mechanism of coke and its role in critically affecting catalyst performance remain poorly understood. Herein, we use operando electron paramagnetic resonance (EPR) spectroscopy together with ex situ pulsed EPR experiments and density functional theory (DFT) calculations to understand coke formation in catalytic pyrolysis of phenol over HFAU and HZSM-5 zeolites. Our results pinpoint that coke formation is heavily influenced by zeolite topology. The large cages in HFAU facilitate the initial formation of linear configurations that grow to extended structures, whereas the narrower channels in HZSM-5 promote the formation of more linear structures. These results provide comprehensive mechanistic insights into coke formation and growth that are relevant for the development of lignin valorization strategies and for the general phenomenon of coke formation in zeolites and beyond.

In the context of this study, it is investigated whether catalytic pyrolysis of post-consumer polypropylene might prove an interesting route to the generation of liquid hydrocarbon materials from plastic waste. The optimum product selectivity can be achieved using the appropriate catalyst. To address this problem, we tested three altered natural zeolites as follows: H-ZN, AT-ZN, and AA-ZN, according to a factorial design which accounts for temperature (400–500 °C), heating rate (10–20 °C per minute), and catalyst loading (5–10 percent by weight). Initially, we verified by thermogravimetric and micro-Raman analyses the thermal behavior of the catalytic systems and the consistency of the polypropylene feedstock. This work confirms that the catalyst assists in initiating the chain-scission process, as changes to the zeolites are responsible for the breakdown of polypropylene at a lower temperature. H-ZN showed high liquid recovery (75.4 wt%), particularly under moderate conditions, as confirmed by product-yield analysis. On the other hand, AT-ZN was more conducive to gas formation and light-fraction production at higher temperatures. H-ZN kept the diesel-range fraction (C12–C20) stable nearly to 51%, according to GC–MS; AT-ZN shifted selectivity to gasoline-range hydrocarbons (C6–C11), up to 57% under severe conditions. AA-ZN showed intermediate behavior. The overall conversion and molecular profile of the liquid products were influenced not only by catalyst acidity, temperature, and their interactions but also by Pearson correlation and ANOVA. The results described above indicate that H-ZN is the most promising catalyst for selective polypropylene-to-diesel conversion and prove that modified natural zeolites are an inexpensive and scalable method for valorizing plastic waste in a circular economy.

This research systematically investigated the catalytic pyrolysis of Arab Heavy (AH) and Arab Light (AL) crude oils using NiO supported on Al2O3 or ZSM-5 in a microwave-assisted reactor, with particular emphasis on hydrogen (H2) generation and value-added chemicals. To understand how both the catalyst and feedstock affect reaction products, gas and liquid products as well as catalyst activity were carefully examined. The production of H2 and olefins was significantly enhanced by the NiO/Al2O3 catalyst, especially when using AL crude. This is most likely due to favorable metal-support interactions that increase the dehydrogenation activity. However, when paired with lighter feedstock, NiO/ZSM-5 greatly increased paraffin production and encouraged light alkane synthesis in both phases. GC-MS and FTIR spectroscopy confirmed that NiO/Al2O3 produced liquid products richer in aromatics while also containing a significant fraction of paraffins. Remarkably, the AL over NiO/Al2O3 combination showed very little liquid recovery, indicating that gas generation was higher in these reaction conditions. These results showed how H2 selectivity and hydrocarbon routes in NiO/ZSM-5 and NiO/Al2O3 are controlled by various microwave-catalyst interactions. This work further highlights the importance of matching catalyst properties with feedstock type to control product selectivity, with NiO/Al2O3 showing particular promise for H2-focused applications.

Metal sulphate catalysts are widely used in biomass conversion to produce value-added chemicals, yet their stability in the reaction environment has not been studied. Most often, based on the inherent thermal stability of the pure species, sulphate catalysts are simply assumed stable when the reaction temperatures are low. However, in this paper, through studying the catalytic pyrolysis of cellulose ((C 6 H 10 O 5 ) n ) by experimental investigation, advanced characterisation and density functional theory (DFT) calculation, we prove that the ZnSO 4 - supported MCM-41 (with the inclusion of 1 wt% Pd in its matrix) is unstable at the pyrolysis temperatures of 400-450 °C, which is far below the thermal decomposition temperature of 646 °C for pure ZnSO 4 . This is due to the strong reaction between ZnSO 4 and formaldehyde (HCHO), an intermediate produced from the Grob fragmentation of the methyl group on glucose. It induces the loss of Brønsted acidity and reactivity of catalysts, along with the release of gaseous SO 2 that is environmentally concerning. Nevertheless, upon the inclusion of only 3.5 wt% Al into the MCM-41 matrix, ZnSO 4 was confirmed to remain stable during the cyclic and continuous tests, due to the formation of a strong covalent Zn-SO 4 -Al bond that enhances the dispersion of ZnSO 4 within the MCM mesoporous framework, and the energy demand for the desorption of SO 2 from the catalyst surface . Most significantly, such a hidden benefit of Al is complementary to its primary role in moderating the total acidity and Brønsted/Lewis acid ratio, leading to a record - high furfural (C 5 H 4 O 2 ) selectivity of 44-49.5% and a mass yield of 27.7-31.2 wt% from the pyrolysis of cellulose in batch-scale fixed-bed reactor. The hidden benefit of Al is also applicable to other sulphates, including CuSO 4 and Fe 2 (SO 4 ) 3 , although the extent for the improvement on their stability varies. These findings are expected to offer new insights for the design and use of sulphate-based acidic catalysts in practical applications. • ZnSO 4 @Pd-Al-MCM achieves furfural selectivity of ~49.5% and yield of ~31.2 wt%. • ZnSO 4 @Pd-MCM suffers from instability during cellulose pyrolysis (400-450°C). • HCHO strongly reacts with ZnSO 4 , driving SO 2 release and Brønsted acidity loss. • Al incorporation (3.5 wt%) forms Zn-SO 4 -Al bonds, enhancing sulphate stability. • Al-induced stabilisation is applicable to CuSO 4 and Fe 2 (SO 4 ) 3 sulphates.

Recent advances in CO2-free hydrogen production through catalytic methane pyrolysis: A comprehensive review on iron-based catalysts

Production of aromatic hydrocarbons from lignin via catalytic gas-phase pyrolysis over a PtMo/Ti@Si core-shell catalyst

Components interaction and its impacts on aromatic structures and coking behavior during catalytic and non-catalytic pyrolysis of bio-oil