Search Results (143)

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

Dry reforming of methane (DRM) is a promising method for turning two major greenhouse gases, CO₂ and CH₄, into syngas (H₂ + CO). This syngas has the right H₂/CO ratio for making valuable chemicals and liquid fuels. However, there are significant challenges that make it tough to implement commercially. One big issue is that the process requires a lot of energy because it is highly endothermic, needing temperatures over 700 °C. This high heat can quickly deactivate the catalyst due to carbon build-up (coking) and the thermal sintering of metal nanoparticles. Researchers increasingly recognize mechanochemistry—a non-thermal, solid-state technique employing mechanical force to drive chemical transformations—as a sustainable, solvent-free strategy to address these DRM challenges. This mini-review critically assesses the dual role of mechanochemistry in advancing DRM. First, we examine its established role in creating advanced catalysts at lower temperatures. Here, mechanochemical methods help produce well-dispersed nanoparticles, enhance strong interactions between metal and support, and develop bimetallic alloys that resist coke formation and show great stability. Second, we delve into the exciting possibility of using mechanochemistry to directly engage in the DRM reaction at near-ambient temperatures, which marks a major shift from traditional thermocatalysis. Lastly, we discuss the key challenges ahead, like scalability and understanding the mechanisms involved, while also outlining future directions for research to fully harness mechanochemistry for converting greenhouse gases sustainably. Full article

This study compares unsupported NiO nanoflowers (NiEG) and ZrO₂-supported NiO (25NiZ) for methane activation and hydrogenation, focusing on the impact of catalyst morphology. The NiEG catalyst demonstrated superior performance, achieving a high methane activation rate of 1.79 mol/(s·g_NiO) and unique product selectivity. It produced ethylene and ethane at 503 K and higher hydrocarbons (C₄–C₆) at 593 K. Furthermore, the NiEG catalyst exhibited enhanced coke resistance, forming less-deactivating carbon nanotubes compared to the filamentous coke prevalent on the 25NiZ catalyst. We attribute this performance to the nanoflower morphology, which provides highly exposed and stable Ni sites that facilitate C-H cleavage and stabilize reaction intermediates. Full article

In recent years CO₂ reforming of methane has attracted great interest as it produces high CO/H₂ ratio syngas suitable for the synthesis of higher hydrocarbons and oxygenated derivatives since it is a way for disposing and recycling two greenhouse gases with high environmental impact, CH₄ and CO₂, and because it is regarded as a potential route to store and transmit energy due to its strong endothermic effect. Along with noble metals, all the group VIII metals except for osmium have been studied for catalytic CO₂ reforming of methane. It was found that the catalytic activity of Ni, though lower than those of Ru and Rh, was higher than the catalytic activities of Pt and Pd. Although noble metals have been proven to be insensitive to coke, the high cost and restricted availability limit their use in this process. It is therefore valuable to develop stable Ni-based catalysts. In this contribution, we show how their activity and coking resistivity are greatly related to the size and dispersion of Ni particles. Well-dispersed Ni nanoparticles were achieved by multistep impregnation on a mesoporous silica support, namely SBA-15, obtained through a sol-gel method, using acetate as a nickel precursor and keeping the Ni loading between 5% and 11%. Significant catalytic activity was obtained at temperatures as low as 450 °C, a temperature well below their deactivation temperature, i.e., 700 °C. For the pre-reduced samples, a CO₂ conversion higher than 99% was obtained at approximately 680 °C. As such, their deactivation by sintering and coke formation was prevented. To the best of our knowledge, no Ni-based catalysts with complete CO₂ conversion at temperatures lower than 800 °C have been reported so far. 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

Dry reforming of methane (DRM) into synthesis gas (CO + H₂) is one of the most important chemical reactions for industrial hydrogen production. It also enables the synthesis of hydrocarbons (liquid fuels) and other valuable products, providing an effective route for utilizing greenhouse gases. However, a major challenge limiting the implementation and scale-up of DRM is the high cost of stable and active noble metal-based catalysts, or the rapid deactivation of nickel- and cobalt-based catalysts due to coking and sintering of the active metal particles. In this context, the present work demonstrates that combining a highly active and inexpensive component (Ni) with tungsten carbide produces a composite material exhibiting high catalytic activity and resistance to oxidation and coking during DRM. Tungsten carbide was synthesized using a vacuum-free electric arc method, and nickel was subsequently deposited in varying amounts (1–25 wt.%) using the deposition–precipitation method with NaOH (DP). The resulting catalysts were characterized by X-ray diffraction, temperature-programmed reduction and Raman spectroscopy. Their performance was evaluated under DRM conditions, at atmospheric pressure and 800 °C, using different CH₄:CO₂ ratios. The most effective oxidation/(re)carbonization cycle, ensuring catalyst stability during DRM by balancing the rates of carbon formation and removal from the catalyst surface, was achieved with a nickel content of 20 wt.% and a CH₄ to CO₂ ratio of 0.67 in the feed gas mixture. Full article

This paper presents the results of an investigation into the catalytic activity and selectivity of rhodium-based catalysts supported on natural zeolite clinoptilolite from the Shankanai field (Kazakhstan) in the dehydrogenation of light alkanes from associated petroleum gas (APG). Three modifications of the catalyst have been studied: basic 1%Rh/HCpt, modified with tin 1%Rh/10%SnO/HCpt, and combined with additives of tin and potassium 1%Rh/10%SnO/5%K₂O/HCpt. It has been shown that the addition of tin contributes to increased thermal stability and a decreased coking rate, while the addition of potassium suppresses side reactions (cracking and isomerization), increasing the selectivity for olefins. The highest yield of olefins (~30%) is achieved with the 1%Rh/10%SnO/5%K₂O/HCpt catalyst in the presence of water vapor. Using scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM), improved distribution of active components and reduced catalyst deactivation have been confirmed. The obtained data demonstrate the potential of the developed systems for the efficient processing of APG and the selective synthesis of olefins. Full article

The Ni/SiO₂ and the ceria-promoted Ni-CeO₂/SiO₂ were prepared by the impregnation method and co-impregnation method, respectively. The performance of the carbon dioxide reforming of methane (CDR) over Ni/SiO₂ and Ni-CeO₂/SiO₂ was investigated under the conditions of CH₄/CO₂ = 1.0, T = 800 °C, and GHSV = 60,000 mL·g⁻¹·h⁻¹. As a result, a high CDR performance, especially stability, was obtained over Ni-CeO₂/SiO₂, in which the conversion of CH₄ was very similar to that of the thermodynamic equilibrium (88%), and a negligible decrease in CH₄ conversion was observed after 50 h of the CDR reaction. Ni/SiO₂ and Ni-CeO₂/SiO₂ before and after the CDR reaction were subjected to structural characterization by XRD, TEM, TG–DSC, and physical adsorption. It was found that the addition of CeO₂ into Ni/SiO₂ significantly affected its surface area, the size and dispersion of Ni, the reduction behavior, and the coking properties. Moreover, the redox property of Ce³⁺-Ce⁴⁺, which accelerates the gasification of the coke, made Ni-CeO₂/SiO₂ successfully operate for 50 h without observable deactivation. Thus, the developed catalyst is very promising for the CDR. Full article

In the methylation of pseudocumene with methanol over IM-5 zeolite, the yield of durene can be enhanced. However, poorer stability of the catalytic activity was observed, especially at a higher methanol/pseudocumene ratio. In this paper, conventional characterization methods (XRD, XRF, TGA, SEM, physical adsorption, OH-IR, NH₃-TPD, and Py-IR) were used to characterize fresh and deactivated IM-5 zeolite and ZSM-5. FT-IR, XPS, TG-MS, GC-MS, FT-ICR MS, and NMR were employed to characterize deactivated IM-5 zeolite. It was found that the deactivation of IM-5 zeolite was mainly due to the severe coverage of acidic sites and pore channels by carbon deposits. The carbon deposits within the internal surface had a higher abundance, mainly in the form of linear unsaturated chain-like structures with a high degree of unsaturation. The carbon deposits on the external surface were mainly polycyclic aromatic hydrocarbons with alkyl side chains and a high degree of saturation, accompanied by unreacted methanol. Moreover, graphitized carbon existed on both the internal and external surfaces, which made the conventional coke-burning regeneration method unable to restore the activity of the post-reaction IM-5 zeolite. This work had certain reference significance for modulating the acidity and pore channels of zeolite catalysts, thus improving the activity and stability of the catalysts and extending their service life. Full article

Solid oxide fuel cells (SOFCs) represent a pivotal technology in renewable energy due to their clean and efficient power generation capabilities. Their role in potential carbon mitigation enhances their viability. SOFCs can operate via a variety of alternative fuels, including hydrocarbons, alcohols, solid carbon, and ammonia. However, several solutions have been proposed to overcome various technical issues and to allow for stable operation in dry methane, without coking in the anode layer. To avoid coke formation thermodynamically, methane is typically reformed, contributing to an increased degradation rate through the addition of oxygen-containing gases into the fuel gas to increase the O/C ratio. The performance achieved by reforming catalytic materials, comprising active sites, supports, and electrochemical testing, significantly influences catalyst performance, showing relatively high open-circuit voltages and coking-resistance of the CH₄ reforming catalysts. In the next step, the operating principles and thermodynamics of methane reforming are explored, including their traditional catalyst materials and their accompanying challenges. This work explores the components and functions of SOFCs, particularly focusing on anode materials such as perovskites, Ruddlesden–Popper oxides, and spinels, along with their structure–property relationships, including their ionic and electronic conductivity, thermal expansion coefficients, and acidity/basicity. Mechanistic and kinetic studies of common reforming processes, including steam reforming, partial oxidation, CO₂ reforming, and the mixed steam and dry reforming of methane, are analyzed. Furthermore, this review examines catalyst deactivation mechanisms, specifically carbon and metal sulfide formation, and the performance of methane reforming and partial oxidation catalysts in SOFCs. Single-cell performance, including that of various perovskite and related oxides, activity/stability enhancement by infiltration, and the simulation and modeling of electrochemical performance, is discussed. This review also addresses research challenges in regards to methane reforming and partial oxidation within SOFCs, such as gas composition changes and large thermal gradients in stack systems. Finally, this review investigates the modeling of catalytic and non-catalytic processes using different dimension and segment simulations of steam methane reforming, presenting new engineering designs, material developments, and the latest knowledge to guide the development of and the driving force behind an oxygen concentration gradient through the external circuit to the cathode. Full article

Previous studies have shown that fats, oils, and greases (FOG) can be deoxygenated to fuel-like hydrocarbons over inexpensive alumina-supported Ni catalysts promoted with Cu or Fe to afford excellent yields of renewable diesel (RD). In this study, supports other than alumina—namely, SiO₂-Al₂O₃, Ce_0.8Pr_0.2O₂, and ZrO₂—were investigated to develop catalysts showing improved RD yields and resistance to coke-induced deactivation relative to Al₂O₃-supported catalysts. Results showed that catalysts supported on Ce_0.8Pr_0.2O₂ and ZrO₂ outperformed SiO₂-Al₂O₃-supported formulations, with 20%Ni-5%Fe/ZrO₂ affording a quantitative yield of diesel-like hydrocarbons. Notably, the abundance of weak acid sites varied considerably across the different supports, and a moderate concentration of these sites corresponded with the best results. Additionally, temperature-programmed reduction measurements revealed that Ni reduction is greatly dependent on both the identity of the promoter and catalyst support, which can also be invoked to explain catalyst performance since metallic Ni is identified as the likely active site for the deoxygenation reaction. It was also observed that Ce_0.8Pr_0.2O₂ provides high oxygen storage capacity and oxygen mobility/accessibility, which also improves catalyst activity. Full article

The efficient utilization of heavy oil is of great significance to alleviating the global energy crisis. How to efficiently convert heavy oil into high-value-added light fuel oil has become a hot issue in the field of petrochemicals. As the residual part of crude oil processing, heavy oil has a complex composition and contains polycyclic aromatic hydrocarbons, long-chain alkanes, and heteroatom compounds, which makes it difficult to process directly. Zeolite, as an important type of solid acid catalyst, has a unique pore structure, adjustable acidity, and good thermal stability. It can promote the efficient cracking and conversion of heavy oil molecules, reduce coke formation, and improve the yield and quality of light oil products. This paper systematically reviews the development status of heavy oil cracking technology, focusing on the structural characteristics, acidity regulation of zeolite catalysts, and their applications in heavy oil cracking and hydrocracking. The mechanism of the cracking reaction of polycyclic aromatic hydrocarbons and long-chain alkanes is analyzed in detail, and the catalytic characteristics and modification methods of zeolite in the reaction process are explained. In addition, this paper summarizes the main challenges faced by zeolite catalysts in practical applications, including uneven acidity distribution, limited pore diffusion, and easy catalyst deactivation, and proposes targeted development strategies. Finally, this paper looks forward to the future development direction of zeolite catalysts in the field of heavy oil cracking and upgrading reactions, emphasizes the importance of structural optimization and multi-scale characterization, and provides theoretical support and practical reference for the design and industrial application of efficient zeolite catalysts. Full article

This study investigates the transformation of biogas (methane and carbon dioxide) into high-value liquid products using Ni/Al₂O₃, Fe/Al₂O₃, and Ni-Fe/Al₂O₃ catalysts in a non-thermal plasma (NTP)-assisted process within a dielectric barrier discharge (DBD) reactor, operating at room temperature and atmospheric pressure. We compared the effectiveness of these three catalysts, with the Ni-Fe/Al₂O₃ catalyst showing the highest enhancement in conversion rates, achieving 34.8% for CH₄ and 19.7% for CO₂. This catalyst also promoted the highest liquid yield observed at 38.6% and facilitated a significant reduction in coke formation to 10.4%, minimizing deactivation and loss of efficiency. These improvements underscore the catalyst’s pivotal role in enhancing the overall process efficiency, leading to the production of key gas products such as hydrogen (H₂) and carbon monoxide (CO), alongside valuable liquid oxygenates including methanol, ethanol, formaldehyde, acetic acid, and propanoic acid. The findings from this study highlight the efficacy of combining NTP with the Ni-Fe/Al₂O₃ catalyst as a promising approach for boosting the production of valuable chemicals from biogas, offering a sustainable pathway for energy and chemical manufacturing. Full article

The auto-thermal reforming (ATR) of acetic acid is an effective hydrogen production method, but it suffers from catalyst deactivation by coking. Sm-promoted layered La₂NiO₄ perovskite catalysts were synthesized via the sol–gel method and its catalytic performance in the ATR of HAc was further evaluated. The characterization results demonstrate that the incorporation of Sm into the lattice of La₂NiO₄ perovskite led to the formation of Ni-La-Sm-O species, inducing crystal defects in the perovskite structure which could promote the gasification of coking precursors. Additionally, Sm regulated the reduction characteristics of La₂NiO₄, resulting in the formation of highly dispersed nickel nanoparticles upon the hydrogen reduction, which increased the number of active sites available for acetic acid conversion. Consequently, a stable reactivity without obvious coking was obtained over a Ni_0.42La_0.7Sm_0.36O_2.01±δ catalyst within the ATR of Hac. The hydrogen yield reached 2.53 mol-H₂/mol-HAc along with the complete conversion of acetic acid. Full article