Search Results (195)

Here, we report a highly efficient and stable catalytic system based on monometallic oxides supported on HY zeolites for the catalytic oxidation of chlorobenzene (CB). Among the transition and rare-earth metal oxides screened, the 30Cu/HY catalyst demonstrates exceptional performance, achieving near 100% CB conversion at 300 °C (500 ppm CB, 10,000 h⁻¹) alongside outstanding 24 h continuous stability without deactivation. Quantitative Py-IR analysis reveals that this superior activity is fundamentally driven by extensive solid-state ion exchange, forming robust Lewis acid centers (Cu-Y structures) that synergize with zeolitic Brønsted acid sites to efficiently polarize and cleave C-Cl bonds. Through an integrated approach combining in situ DRIFTS, real-time mass spectrometry, TGA, and NLDFT pore size analysis, we elucidate that the exceptional deep-oxidation capability of Cu/HY continuously mineralizes carbonaceous intermediates. This property minimizes coke deposition (2.91 wt%) and preserves the hierarchical pore architecture, preventing the coverage of active sites and severe pore blockage by partially oxidized intermediates (such as phenolic, aldehydic, and quinonic species) and stable carbonate species responsible for the deactivation of other metal oxides. These insights provide a mechanistic framework for the rational design of robust, chlorine-resistant catalysts for the sustainable abatement of persistent organic pollutants. Full article

The purpose of this work was to synthesize and study catalytic systems based on a carbon-containing support obtained from coke fines from the Shubarkol deposit as a waste product of the coal industry for the processing of phenolic compounds. Based on the obtained carbon sorbent, mono- and binary catalysts with active phases of transition metal oxides (Fe, Co, Ni) were synthesized by wet impregnation, followed by heat treatment at 500–700 °C, as well as the aluminum oxide compositions. The surface morphology and elemental composition of the samples were studied by scanning electron microscopy (SEM) with energy dispersion analysis and elemental mapping (EDS mapping), and the content of active phases was determined using inductively coupled plasma optical emission spectrometry (ICP-OES). The catalytic activity was studied in phenol hydrogenation reactions. The CoO/C catalyst demonstrated the greatest activity, providing a 62.36% benzene yield during phenol hydrogenation. The catalytic activity of the CoO/C catalyst has also been studied in the hydrogenation reactions of structurally and functionally more complex compounds, pyrocatechol and resorcinol. The yield of benzene was 63.16% in the hydrogenation of pyrocatechol and 48.64% in the hydrogenation of resorcinol. It was found that the CoO/C catalyst exhibits the highest efficiency at a temperature of 420 °C, a pressure of 6–6.5 MPa and a reaction duration of 120 min. The results obtained make it possible to evaluate the prospects of using a carbon sorbent obtained from coke fines from the Shubarkol deposit as a support for CoO as part of an active and stable catalytic system designed for deep processing of phenolic compounds. Full article

Thermal–oxidative coking of aviation fuel remains a critical limitation for fuel-cooled aero-engine systems operating under high heat loads. This study systematically investigates the oxidative coking behavior of RP-3 aviation kerosene, focusing on the coupled evolution of deposit morphology, composition, and operating conditions. Experiments were conducted in an electrically heated stainless-steel tube while independently varying dissolved oxygen concentration, fuel temperature, temperature gradient, operating pressure, and heating duration. Deposit layers were characterized by SEM and XPS, and residual fuel chemistry was analyzed using GC/MS. The results show that dissolved oxygen governs both the extent and mechanism of coking in the autoxidation regime (150–450 °C). Normal and elevated oxygen levels promote autoxidation of straight-chain alkanes, generating oxygen-containing intermediates that form flocculent, oxygen-rich deposits, whereas near-deoxygenated conditions suppress autoxidation but sustain sulfur-dominated, needle-like deposits. Temperature primarily controls deposition rate and morphology, with steep temperature gradients inducing localized coke formation, while pressure exerts only a minor indirect influence. Prolonged operation leads to deposit densification and non-linear accumulation behavior. These findings clarify the links between fuel chemistry, thermal conditions, and deposit architecture, providing a basis for morphology-aware coking models in fuel-cooled aero-engine systems. Full article

CO₂-assisted catalytic pyrolysis presents a viable and promising approach to addressing plastic waste pollution and mitigating climate change. However, the effects of the metal–catalyst combination mode and the spatial distance between metal–acid sites on catalytic performance remain unclear. In this study, the reaction behaviors of the configurations, Fe₃O₄ and ZSM-5 in tandem catalysis (Fe₃O₄&HZ), their physical mixture (Fe₃O₄-HZ), and Fe-loaded ZSM-5 (Fe/HZ), were compared in polypropylene pyrolysis under a CO₂ atmosphere. The aromatic contents followed this order: Fe/HZ > Fe₃O₄-HZ > Fe₃O₄&HZ > ZSM-5 > Fe₃O₄. Specifically, Fe/HZ with the highest degree of metal–zeolite proximity achieved an aromatic content of 66.1%, significantly higher than the 34.2% obtained with Fe₃O₄&HZ, demonstrating that closer metal–acid proximity promoted aromatic formation. Moreover, Fe/HZ significantly reduced coke deposition. Based on characterization results from XRD, SEM, TEM, XPS, and NH₃-TPD, the enhanced spatial proximity between metal and acid sites strengthened the functional synergy between iron-based redox sites and zeolitic Brønsted acid sites. This synergy facilitated the reverse water–gas shift reaction of CO₂, which consumed hydrogen generated during aromatization and shifted the reaction equilibrium toward enhanced aromatic production. These findings would offer theoretical and strategic insights into the optimization of CO₂-assisted catalytic pyrolysis systems for the sustainable upcycling of plastic waste. Full article

Linear alkylbenzene (LAB) is the main raw material used to make biodegradable detergents, and its production process is based on aromatic alkylation. HY zeolites that have undergone controlled dealumination and desilication have led industrial standards amongst solid acid catalysts because of their controllable acidity and hierarchical pore structure. Coke formation in such systems can assume a dual role, which is dependent on its condition. Though the over-deposition is known to cause deactivation by blocking the micropores, Bronsted acid-site masking, and diffusion collapse, the low-level deposition could also be done to increase the monoalkylate selectivity by the pore mouth catalysis, steric modulation, and selective suppression of secondary alkylation pathways. The critical review is done on the structural-kinetic interaction that determines the coke evolution in HY-based catalysts. In order to moderate the acid-site density and enhance hydrothermal stability, dealumination (Si/Al optimization of about 2.5 to 30–100) occurs, but to reduce deep-pore coke formation, desilication (interconnected mesopores) is created. The bimodal porosity and regulated acidity are found to be synergistic, as hierarchical HY zeolites produced through successive cycles of steam and alkaline treatments not only show LAB selectivity in excess of 90% but also exhibit much longer catalyst lifetimes. Quantitative research on the beneficial coke regime revealed that it was composed of about 36 wt% hydrogen-rich species, which were localized at the pore mouths, hence enhancing monoalkylation selectivity by 15–40%. Beyond a critical transition window (e.g., 8–12 wt.%), coke formation to condensed polyaromatic and graphitic products leads to fast deactivated coke formation, which is due to percolation limits and transport-controlled kinetics. More advanced techniques of characterization of the coke, e.g., temperature-programmed oxidation (TPO), ²⁷Al MAAS NMR, and UV-Raman spectroscopy, indicate how the coke is changed to highly structured graphitic deposits of high oxidation activation energy. Activity recovery of 85–98% is obtained in regeneration processes, including controlled oxidative calcination, microwave-based and plasma-based processes, and thermal management protocols, and it would be determined by the chemistry of the coke, its spatial distribution, and the regeneration protocols. This paper has developed a mechanistic coke control system by cross-tuning the acidity and development of an effective pore network, which led to a sustainable aromatic alkylation reaction with minimal activity loss, high selectivity, and long life. Full article

Nickel-supported catalysts over SiO₂-CeO₂ mixed oxides were investigated as catalysts for syngas production via dry reforming of methane. SiO₂-CeO₂ supports were optimized by varying the preparation method and ceria loading with the aim of stabilizing nickel nanoparticles, enhancing the catalytic performance, and improving the resistance to coke formation under high-temperature reforming conditions. To investigate the effect of support composition, SiO₂-CeO₂ mixed oxides with ceria contents ranging from 5 to 30 wt% were prepared using two synthesis routes: sol–gel and wetness impregnation methods. A nickel loading of 5 wt% was deposited on the resulting supports. The catalysts were characterized by XRD, N₂ physisorption, temperature-programmed reduction (TPR), and Raman spectroscopy. Catalytic activity tests were carried out over reduced catalysts in an H₂-He stream at 750 °C, using a feed mixture containing 15 vol% CH₄ and 15 vol% CO₂ in He. The effect of temperature on catalytic performance was evaluated in the range of 450–750 °C. Thermogravimetric, XRD and Raman analyses of spent catalysts were used to assess carbon deposition and the nature of crystalline phases. The results highlight the role of CeO₂ content and preparation method in determining nickel dispersion, reducibility, catalytic performance in DRM, and coke resistance. Full article

As the “flagship” unit of the petrochemical industry, the operational status of ethylene cracking furnaces directly impacts the stability and efficiency of the entire production chain. During long-term operation under extreme temperatures and complex reaction environments, cracking furnace tubes face core bottlenecks primarily related to thermal and coking effects, such as coke deposition, tube metal overheating, and associated creep damage, which restrict the long-term, safe, and efficient operation of the unit. This paper systematically reviews the key technologies for condition monitoring of cracking furnace tubes, providing an in-depth analysis of various monitoring methods—from traditional infrared thermometry and acoustic emission to emerging optical fiber sensing—covering their working principles, application status, and inherent limitations. Furthermore, it elaborates on the evolution from mechanism-based “white-box” models to data-driven “black-box” models, and further to “gray-box” intelligent diagnostic models that integrate expert knowledge. Industrial application cases of integrated monitoring and diagnostic systems are also introduced. Finally, the paper critically addresses the current severe challenges in data fusion, model generalization, real-time performance, and cost-effectiveness, while outlining future development trends toward digital twins, cross-modal fusion, edge intelligence, and self-evolving systems. The aim is to provide valuable references for technological innovation and engineering applications in this field. Full article

This study investigates the improvement of Ni/SiO₂-Al₂O₃ catalysts in the dry reforming of methane (DRM) process by detailed adjustments of calcination temperature (600–900 °C) and duration (1–9 h). N₂ physisorption, H₂-TPR, XRD, TGA, and TEM show that elevated calcination temperatures result in increased surface roughness and reduced specific surface areas. The present investigation indicates that the ideal calcination parameters are 900 °C and 3 h. This helps the catalyst work better. This condition gave the best initial activity (54% CH₄ conversion and 61% CO₂ conversion) and the best long-term stability and resistance to carbon deposition. Using MATLAB R2025b (ODE45) for kinetic analysis, it was found that these factors have a big effect on activation energy. Shorter calcination of 1 h gave high initial activity, but it quickly lost its effectiveness. On the other hand, a longer calcination time of 9 h made the material more stable but less able to condition convert because it sintered too much. These results show that it is very important to carefully control the conditions of calcination in order to make long-lasting, high-performance catalysts for making syngas. Moreover, a 20-h DRM stability run of the optimum catalyst exhibited nearly constant activity, highlighting its strong structural integrity and superior ability to alleviate rapid coke formation. Full article

CO₂ valorization from real feedstocks through CH₄ tri-reforming (CH₄-TR), combining steam reforming (SR), dry reforming (DR), and partial oxidation (CPO) of methane in a single process, is a desirable strategy for greenhouse gas mitigation and syngas (CO + H₂) production. NiCo/γ−Al₂O₃ catalysts prepared by impregnation at different relative metal contents (Ni₅₀Co₅₀ and Ni₃₀Co₇₀) were investigated for CH₄-TR in a fixed-bed reactor under conventional heating and characterized by XRD, FESEM, and Raman spectroscopy after catalytic runs. This study focused on the role of the Ni/Co ratio and feed composition on selectivity for CO₂ valorization, syngas yield, and deactivation resistance. Both the catalysts showed high activity, with a superior performance of Ni₅₀Co₅₀ confirming Ni metal species as the active sites. While in DR, a slow deactivation occurred due to coke deposition, in CH₄-TR, the addition of small O₂ and/or H₂O amounts stabilized activity and selectivity due to surface carbon removal. Large O₂ and H₂O amounts strongly inhibited CO₂ conversion due to competition with CPO and SR, in the order CPO ≥ DR > SR. Interestingly, the stoichiometric CH₄-to-oxidants ratio favored the DR pathway, giving very high CO₂ conversion. Modulating CH₄ addition into real flue mixtures renders CH₄-TR on NiCo/γ-Al₂O₃ catalysts a favorable strategy for effective valorization of CO₂ industrial or biomass-derived streams. Full article

The increasing demand for clean and sustainable energy has driven significant research into hydrogen production from biomass-derived feedstocks. Unlike the gasification route, the pyrolysis of biomass followed by steam reforming of bio-oil (SRBO) offers several advantages, including the liquid nature of bio-oil and the operation at lower temperatures, which facilitate easier transportation and storage compared to raw biomass. The conventional SRBO process faces several limitations, mainly catalyst deactivation due to significant coke formation and metallic sintering, as well as low hydrogen yield and purity. Hence, the intensified sorption-enhanced steam reforming of bio-oil (SESRBO) is a promising strategy to overcome these drawbacks, to simultaneously produce high-purity hydrogen and capture carbon dioxide in situ from the reaction media. This critical review presents an in-depth comparative analysis of conventional and intensified steam reforming of bio-oil, with a focus on associated challenges. Special attention is given to recent developments in the design of bifunctional materials (BFMs), which integrate both catalyst and sorbent into a single particle, along with process optimization focusing on key parameters, i.e., reforming temperature and steam presence. Finally, the review highlights key research gaps and future directions to overcome existing challenges in achieving cost-effective and scalable hydrogen production. Full article

Dry reforming of methane (DRM) is a method whereby two greenhouse gases (methane and carbon dioxide) are synthesized into a high-value gas. Suitable catalysts with optimal compositions are still in development, as problems concerning coking and metal sintering remain unresolved. Since the late 20th century, catalysts prepared via solution combustion synthesis (SCS) have been applied for catalytic reactions, as these materials (catalyst or supports) demonstrate high catalytic performance; for example, SCS catalysts have been tested in DRM. This review describes the history of solution combustion synthesis, compares it with traditional methods of preparing catalysts for DRM, and charts recent developments in SCS catalytic systems based on Ni and Co. SCS catalysts are prepared by burning nitrates (oxidizing agents) and fuels (reducing agents) at mild pre-ignition temperatures. In this review, the effects of fuel type and mixed-fuel systems on the catalyst composition, as well as its activity in DRM, are described. These catalysts have shown high metal dispersion, good coke resistance, and stable catalytic performance in long-term tests. This review demonstrates the main reasons for catalyst deactivation, such as coke deposition on the catalyst surface, and suggests ways to reduce them. Full article

Three-dimensionally ordered macroporous (3DOM) La₂O₃-supported Ni catalysts exhibit outstanding performance for methane dry reforming (DRM). The 5Ni/La₂O₃-3DOM catalyst achieves 79% CH₄ and 84% CO₂ conversions at 800 °C under the reaction conditions of atmospheric pressure, CH₄:CO₂ molar ratio of 1:1, and gas hourly space velocity (GHSV) = 36,000 mL·gcat⁻¹·h⁻¹, outperforming its counterparts (5Ni/La₂O₃-PP prepared by means of co-precipitation and 5Ni/La₂O₃-GNC prepared by means of glycine–nitrate combustion) by 15–20%. Long-term stability tests at 700 °C (same CH₄:CO₂ ratio and GHSV as above) show that the 5Ni/La₂O₃-3DOM catalyst maintains CH₄ and CO₂ conversions at approximately 80% and 85%, respectively, with zero deactivation over 50 h. Meanwhile, its carbon deposition rate plummets to 1.1 mg·g⁻¹·h⁻¹, which is 75% lower than that of the precipitation-derived 5Ni/La₂O₃-PP catalyst. This excellent performance stems from the synergy of nano-confined Ni particles (11.2 nm in crystallite size after reduction) and abundant surface oxygen species (38 μmol·g⁻¹), establishing 3DOM La₂O₃ as a superior anti-coking support platform for scalable H₂ production via DRM. Full article

Methane dry reforming (DRM) represents a promising route for the simultaneous valorization of CH₄ and CO₂ into syngas; however, conventional Ni-based catalysts suffer from rapid deactivation due to sintering and carbon deposition. In this work, we present a synergistically engineered Ni-based catalyst integrating hierarchical SiC confinement, Pd promotion via oleic-acid-assisted complexation, and MgO surface modification to overcome these challenges. Under optimized reaction conditions (CH₄/CO₂ = 1:1, 750 °C, GHSV = 36,000 mL g⁻¹ h⁻¹), the multifunctional NiPd/Si–xMg catalyst achieved steady-state conversions of 85% for CH₄ and 84% for CO₂, maintaining an H₂/CO ratio close to 1.0 over 100 h of continuous operation without noticeable deactivation. In contrast, the reference Ni/SiC and Ni/MgO catalysts exhibited initial conversions of 75–80% but declined by more than 50% within the same period, confirming the superior durability of the optimized system. Thermogravimetric analysis (TGA) revealed a drastic reduction in carbon deposition—from 119.0 mg C g⁻¹ for Ni/SiC to 81.4 mg C g⁻¹ for NiPd/Si-xMg—indicating enhanced coke resistance. Transmission electron microscopy (TEM) confirmed uniform Ni dispersion with an average particle size of 7.2 ± 1.8 nm, while H₂-TPR and CO₂-TPD analyses demonstrated improved reducibility and surface basicity. The combination of SiC confinement, Pd-induced hydrogen spillover, and MgO-mediated CO₂ activation effectively mitigated sintering and carbon accumulation, resulting in high activity, stability, and carbon tolerance. This integrated catalyst design provides a robust pathway toward industrially viable DRM systems for sustainable syngas production. Full article

Alkali metal-modified M-ZSM-5 zeolites (M: Li⁺, Na⁺, K⁺) were synthesized by cationic exchange and characterized using ICP-MS, XRD, N₂ adsorption–desorption, Py-IR and NH₃-TPD techniques to evaluate their elemental composition, structure, textural and acidic properties. In addition, XPS and DFT calculations were employed to study the effects of metal ion doping on the electronic structure and catalytic behavior. The latter catalytic performance was assessed in the methanol-to-olefin (MTO) reaction. The results showed that alkali metal doping facilitated the enhancement of the zeolite structural stability, adjustment of acid density, and increase in the adsorption energy of light olefins onto the active sites. During the reaction, olefin products shifted from Brønsted acid sites to alkali metal sites, effectively minimizing hydrogen transfer reactions. This change in the active site nature promoted the olefin cycle, resulting in higher yields in propylene and butylenes, reduced coke deposition, and prolonged catalyst lifetime. Among all zeolites, Li-exchanged ZSM-5 exhibited the best and extending the catalyst lifetime by 5 h. Full article

This work examines the effect of gadolinium (Gd) promotion on nickel-based SBA-16 catalysts for the dry reforming of methane (DRM), with the goal of improving syngas production by optimizing catalyst composition and operating conditions. Catalysts with varying Gd loadings (0.5–3 wt.%) were synthesised using co-impregnation. XRD, N₂ physisorption, FTIR, XPS, and H₂-TPR–CO₂-TPD–H₂-TPR were used to examine the structural features, textural properties, surface composition, and redox behaviour of the catalysts. XPS indicated formation of enhanced metal–support interactions, while initial and post-treatment H₂–TPR analyses showed that moderate Gd loadings (1–2 wt.%) maintained a balanced distribution of reducible Ni species. The catalysts were tested for DRM performance at 800 °C and a gas hourly space velocity (GHSV) of 42,000 mL g⁻¹ h⁻¹. 1–2 wt.% Gd-promoted catalysts achieved the highest H₂ (~67%) and CO yield (~76%). Response surface methodology (RSM) was used to identify optimal reaction conditions for maximum H₂ yield. RSM predicted 848.9 °C temperature, 31,283 mL g⁻¹ h⁻¹ GHSV, and a CH₄/CO₂ ratio of 0.61 as optimal, predicting a H₂ yield of 96.64%, which closely matched the experimental value of H₂ yield (96.66%). The 5Ni–2Gd/SBA-16 catalyst exhibited minimal coke deposition, primarily of a graphitic character, as evidenced by TGA–DSC and Raman analyses. These results demonstrate the synergy between catalyst design and process optimization in maximizing DRM efficiency. Full article