Search Results (108)

Dry reforming of methane (DRM) converts the greenhouse gases methane (CH₄) and carbon dioxide (CO₂) into syngas (hydrogen (H₂) and carbon monoxide (CO)). Despite its numerous advantages, DRM has not yet been industrialized due to catalyst deactivation and competing side reactions. While Ni-based catalysts have been widely used, they are prone to increased carbon deposition and sintering, and although bimetallic systems and oxygen-based supports have shown promise, their effects on carbon deposition are yet to be fully understood. In this study, carbon nanotube (CNT)-supported Pt-Ni catalysts incorporating mixed oxides of CeZrO₂ and CeZrLaO₂ were investigated to evaluate the impact of support composition and metal–support interactions in DRM. The catalysts were synthesized and subsequently tested in DRM. Catalysts supported on CNTs displayed higher CH₄ and CO₂ conversions compared to conventional ceria–zirconia, highlighting the beneficial role of the carbon nanotube support in improving dispersion and accessibility of the metal active sites. Addition of Pt was found to promote reverse water–gas shift (RWGS) reaction, whereas the addition of La was found to decrease catalytic activity. Despite the formation of a Ni-Pt alloy, the obtained catalysts favored RWGS over DRM. These findings illustrate key limitations and design considerations for optimization of CNT-supported bimetallic catalysts in DRM. Full article

As the global imperative for climate neutrality intensifies, hydrogen (H₂) from fossil fuels remains central to decarbonizing hard-to-abate sectors. Conventional production via steam methane reforming (SMR), however, is carbon-intensive and, even with carbon capture and storage (CCS), incurs energy penalties and long-term storage constraints. This review develops a harmonized well-to-gate, market-oriented framework to evaluate methane pyrolysis (MP) relative to SMR and autothermal reforming (ATR), with or without CCS, moving beyond reactor-focused assessments toward system-level commercialization analysis. MP decomposes methane into hydrogen and solid carbon, avoiding direct CO₂ formation and the need for CCS infrastructure. Integrating with the reverse water–gas shift (RWGS) reaction enables flexible syngas production with adjustable H₂:CO ratios for methanol and chemical synthesis. A central finding is the dominant role of the “carbon lever”: MP generates approximately 3 kg of solid carbon per kg of H₂, making the carbon market’s absorptive capacity the primary scalability constraint. While carbon monetization can reduce levelized hydrogen costs, large-scale deployment would rapidly saturate existing carbon black and specialty carbon markets. Techno-economic evidence indicates that carbon prices above $500/ton are required to achieve parity with gray hydrogen, whereas $150–200/ton enables competitiveness with blue hydrogen. Lifecycle assessments further show that climate superiority over SMR or ATR with CCS requires upstream methane leakage below 0.5% and very low-carbon electricity. Commercial readiness varies, with plasma MP at TRL 8–9 and thermal, catalytic, and molten-media pathways remaining at the pilot or demonstration stage. Parametric decision-space analysis under harmonized boundary assumptions shows that MP is not a universal substitute for reforming but a conditional pathway competitive only under aligned conditions of low-leakage gas supply, low-carbon electricity, credible carbon monetization, and supportive policy incentives. The review concludes with a roadmap that highlights standardized carbon certification, end-of-life accounting, and long-duration operational data as priorities for commercialization. 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

In this work, a rational catalyst design based on interfacial architecture engineering is proposed for low-temperature dry methane reforming (DMR) at 550 °C. Ni-based catalysts containing 10 wt% Ni were developed on a γ-Al₂O₃ support modified with 9 wt% MgO–1 wt% ZrO₂. Zirconia promoters were introduced either by dry impregnation or via an ammonia vapor-assisted route to construct a Ni–NiO–ZrO₂ interfacial network. The effects of ZrO₂ content (0, 1, and 3 wt%) and synthesis route on metal–support interactions, oxygen mobility, and coke resistance were systematically investigated. ZrO₂ promotion increased the fraction of reducible Ni species and preferentially enhanced CO₂ activation, thereby promoting the reverse water–gas shift (RWGS) reaction and lowering the H₂/CO ratio. In contrast, ammonia vapor-assisted preparation induced the formation of an LDH-derived Ni–NiO–ZrO₂ surface network, which increased the concentration of surface-accessible Ni species, suppressed excessive zirconia coverage, and significantly improved apparent oxygen mobility. These synergistic structural features are consistent with enhanced oxygen-assisted carbon removal and improved coke management through regulation of the nature of carbon species, leading to more balanced activation of CH₄ and CO₂. Overall, this study provides insights into interfacial structure–performance relationships for designing efficient Ni-based catalysts for CO₂ utilization. Full article

Mo/ZZG and W/ZZG nanomaterials for the catalytic reduction of CO₂ were successfully prepared from preformed ZnO-ZrO₂-Ga₂O₃ (ZZG) and HPMo and HPMo heteropolyacids via simple incipient wetness impregnation. To establish the relationship between structural properties and catalytic performance, the prepared catalysts were deeply characterized using XRD, Raman spectroscopy, SEM coupled with EDX, BET, XPS, and H₂-TPR techniques. The catalytic performance of the materials was evaluated in the RWGS reaction under atmospheric pressure, using a feed composition of CO₂/H₂/N₂ = 1/3/1 across a temperature range of 250–600 °C. All materials were active in the reverse water gas shift reaction (RWGS) under these conditions, with the Mo/ZZG catalyst exhibiting the best performance, demonstrating excellent catalytic activity at low temperature with the lowest activation energy and the highest CO₂ to CO conversion efficiency. Full article

Propylene (C₃H₆) is a vital building block in the chemical industry as it serves as a key raw material for producing plastics, synthetic fibers and numerous daily-use chemicals. However, the current production routes of C₃H₆ are energy-intensive and face sustainability challenges, prompting the scientific community to explore alternative technologies for its production. The oxidative dehydrogenation of propane (ODHP) using CO₂ as a soft oxidant offers a safe and sustainable pathway for C₃H₆ production, where CO₂ can act as a hydrogen scavenger, coke suppressor and site re-activator. Gallium- and chromium-based catalysts are among the most studied systems for CO₂-assisted ODHP, yet they operate by distinct mechanisms: Ga catalysts follow pathways where both acidic and basic sites are involved, while Cr catalysts rely on redox cycles involving variations in the oxidation state of chromium. In addition to performance and reaction mechanism, Ga- and Cr-based catalysts differ markedly in terms of sustainability, with Cr systems facing environmental and regulatory challenges associated with Cr⁶⁺ species toxicity, while Ga systems, although less toxic, are constrained by gallium scarcity and cost. This review compares Ga- and Cr-based catalysts side by side, emphasizing how support effects, addition of promoters and mechanistic insights fine tune their performance. The aim is to highlight the advantages, the limitations as well as the sustainability implications of these materials and finally to outline future directions for designing more efficient and environmentally friendly catalysts for propylene production. Full article

The reverse water–gas shift (RWGS) reaction serves as a highly flexible and critical pathway for converting CO₂ into CO, with Pt-based catalysts having been widely investigated. Here, a series of platinum-rare earth (RE) subnanometric bimetallic clusters (SBCs) were successfully prepared on carbon support by the potassium vapor reduction method. Their structure and electronic properties, along with catalytic performance, were systematically characterized and evaluated. The Pt-RE SBC catalysts exhibited excellent catalytic activity, maintaining CO selectivity above 95% at high CO₂ conversion levels and demonstrating stable operation over 100 h at 600 °C. Furthermore, the influence of different supports (carbon black and CeO₂) on the catalytic performance was compared. It was found that Pt-Sc SBCs supported on the carbon exhibited better dispersion, smaller particle size, and superior catalytic performance relative to the CeO₂ supported counterpart. This study provides new insights into the design of highly efficient and stable RWGS catalysts, highlighting the key role of the Pt-RE SBC interface synergistic effect and support selection, which is of great significance for the resource utilization of CO₂. Full article

The biogas dry reforming reaction offers a promising route for syngas production while simultaneously mitigating greenhouse gas emissions. Membrane reactors have proven to be an excellent option for hydrogen production and separation in a single unit, where conversion and yield can be enhanced over conventional processes. In this study, a Pd/YSZ membrane integrated with a Ru/CeO₂ catalyst was evaluated for biogas reaction under varying operating conditions. The selective removal of hydrogen through the palladium membrane improved reactant conversion and suppressed side reactions such as methanation and the reverse water–gas shift. Experiments were performed at temperatures ranging from 500 to 600 °C, pressures of 1–6 bar, and a gas hourly space velocity (GHSV) of 800 h⁻¹. Maximum conversions of CH₄ (43%) and CO₂ (46.7%) were achieved at 600 °C and 2 bar, while the maximum hydrogen recovery of 78% was reached at 6 bar. The membrane reactor outperformed a conventional reactor, offering up to 10% higher CH₄ conversion and improved hydrogen production and yield. Also, a comparative analysis between Ru/CeO₂ and Ni/Al₂O₃ catalysts revealed that while the Ni-based catalyst provided higher CH₄ conversion, it also promoted methane decomposition reaction and coke formation. In contrast, the Ru/CeO₂ catalyst exhibited excellent resistance to coke formation, attributable to ceria’s redox properties and oxygen storage capacity. The combined system of Ru/CeO₂ catalyst and Pd/YSZ membrane offers an effective and sustainable approach for hydrogen-rich syngas production from biogas, with improved performance and long-term stability. Full article

The reverse water–gas shift (RWGS) reaction efficiently converts CO₂ to CO, with vital applications in carbon emission reduction and Fischer-Tropsch chemical production. This study used density functional theory (DFT) to investigate CO₂ adsorption and activation on CeO₂, oxygen-vacancy CeO₂ (CeO_2−x), and single-atom Ni-loaded CeO₂ (Ni/CeO₂). Adsorption energy analysis indicates that CO₂ preferentially adsorbs at the intermediate oxygen sites on CeO₂ and Ni/CeO₂, but on CeO_2−x, it preferentially adsorbs at the oxygen vacancies. Mulliken charge and band gap results indicate that CeO_2−x and Ni/CeO₂ exhibit higher activity than pure CeO₂. Density of states studies indicate that CeO₂, CeO_2−x, and Ni/CeO₂ can activate CO₂ to varying degrees; strong hybridization between Ni’s d-orbitals and CO₂’s O p-orbitals is key to Ni/CeO₂’s high activity. Mechanistically, CeO_2−x follows the RWGS redox mechanism, while Ni/CeO₂ follows the formate-associated mechanism. This work innovatively clarifies differential CO₂ adsorption-activation by vacancies and Ni in CeO₂-based catalysts, providing a theoretical basis for RWGS catalyst design and supporting low-energy carbon conversion development. Full article

The reverse water gas shift reaction (RWGS) is a key step in the valorization of CO₂ to value-added products such as fuel. Metal carbides, particularly molybdenum carbide (Mo₂C), supported on transition metal oxide supports have been reported as promising materials to be used as catalysts for the low-temperature RWGS reaction. A deeper understanding of catalyst support interactions can be greatly beneficial for the development of better and more efficient catalysts in the future. To this end, this study computationally investigated the effect of the interaction between the Mo₂C(001) surface and the MgO(001) surface on the RWGS mechanism. The RWGS mechanisms were explored at the Mo₂C/MgO interface, as well as on the bare surface of Mo₂C. While the pathway at the interface went through an associative-type mechanism and a carboxylate intermediate, the Mo₂C surface was found to go through a redox-type mechanism. Interestingly, both the kinetics and thermodynamics of each pathway were similar, suggesting that the observed differences in the CO₂ hydrogenation pathways were primarily limited by the diffusion of CO₂ across the MgO surface rather than inhibitory energetics resulting from the interplay of the Mo₂C material and MgO support. Full article

Using Excel and its Solver feature, a novel method of analyzing the component reactions of an overall reaction is outlined. As an example, autothermal reforming (300–700 °C) of acetic acid (AA), a significant component of pyrolysis oil, was considered. The overall reaction can be viewed as comprising five individual reactions: reforming, oxidation, water–gas shift, reverse Boudouard, and methanation. A laboratory apparatus was set up in which acetic acid, air, and water were continuously fed to a BASF dual-layer catalytic reactor in plug flow at 1 atm. For this setup, it is easy to construct a material balance in Excel in which five factors, f_i, are defined which represent the fraction of reactant going to each of the individual five reactions. Using the Solver feature of Excel, it can readily be determined which of the five factors f_i produce the best match of the calculated exit gas composition with the measured gas concentrations for CO, CO₂, H₂, CH₄, and O₂. Furthermore, a program such as GasEq or Aspen can then be used to calculate the theoretical equilibrium gas composition at a given condition. Using this equilibrium gas composition and Solver, the individual (f_i)_equilb can be calculated. Thus, the ratio f_i/(f_i)_equilb is an indication of how close each component reaction is to equilibrium. In this way, an idea is gained of which of the individual component reactions need to be improved or inhibited or if operating parameters should be adjusted. For the specific case of autothermal reforming of acetic acid, the steam reforming reaction requires at least 600 °C to approach equilibrium. In contrast, the oxidation reaction goes to equilibrium throughout the temperature range, completely consuming oxygen. The water–gas shift reaction appears to approach equilibrium to the extent of 71–90% throughout the temperature range. The reverse Boudouard reaction is favored at lower temperatures; in fact, coking was predicted and found at the low temperature of 300 °C. Full article

Natural gas (NG) engine catalysts face unique challenges in emission control due to their distinct raw emission characteristics. This study investigates the exhaust conversion and by-product generation of a Palladium-based catalyst of an NG engine through small-sample catalyst experiments, mainly focusing on the effect of feed gas composition on the conversion efficiency and N₂O/NH₃ emissions. Results show that N₂O is generated via NO reduction by H₂ (80~275 °C) and CO (275~400 °C) in the temperature range of 80~400 °C. NH₃ generation occurs at 175~550 °C, mainly via NO reduction by H₂ (supplied from the water–gas shift (WGS) reaction) and CO below 425 °C and exclusively by H₂ (supplied from the steam reforming (SR) reaction) above 425 °C. An increase (0.9705~1.0176) in lambda enhances CO and CH₄ conversion while reducing N₂O and NH₃ emissions, but it inhibits NO conversion and promotes NO₂ formation. A lambda of 0.9941 achieves high conversion efficiency (≥90%) for CO, CH₄, and NO, with reduced N₂O and zero NH₃ emissions. An increase in H₂O (8~16%) accelerates the WGS and SR reactions, improving pollutant conversion. However, it aggravates N₂O and NH₃ emissions, with peak levels rising by 54% and 31%, respectively. Increased H₂ (500~1500 ppm) preferentially consumes NO and reversely shifts the equilibrium of the WGS and SR reactions, reducing CO and CH₄ conversion while improving NO conversion. And it promotes N₂O selectivity at high temperature and NH₃ selectivity at low temperature and peak emissions, with peak concentrations increasing by 58% and 15%, respectively. These findings reveal the by-product formation mechanism in the catalyst, providing valuable insights for the emission control of NG-fueled engines. Full article

Propylene production through the CO₂-assisted oxidative dehydrogenation of propane (CO₂-ODP) is an effective route able to address the ever-increasing demand for propylene and simultaneously utilize CO₂. In this study, a series of alumina-supported gallium oxide catalysts of variable Ga₂O₃ loading was synthesized, characterized, and evaluated with respect to their activity for the CO₂-ODP reaction. It was found that both the catalysts’ physicochemical characteristics and performance were strongly affected by the amount of Ga₂O₃ dispersed on Al₂O₃. Surface basicity was maximized for the sample containing 20 wt.% Ga₂O₃, whereas surface acidity was monotonically increased with increasing Ga₂O₃ loading. A volcano-type correlation was found between catalytic performance and acid/base properties, according to which propane conversion and propylene yield exhibited optimum values for intermediate surface basicity and acidity, which both correspond to the sample containing 30 wt.% Ga₂O₃. The dispersion of a suitable amount of Ga₂O₃ on the Al₂O₃ surface not only enhances the conversion of propane to propylene but also suppresses the formation of side products (C₂H₄, CH₄, and C₂H₆) at temperatures of practical interest. The 30%Ga₂O₃-Al₂O₃ catalyst exhibited very good stability at 550 °C, where byproduct formation and carbon deposition were limited. Mechanistic studies indicated that the reaction proceeds through a two-step oxidative route with the participation of CO₂ in the abstraction of H₂, originating from propane dehydrogenation, through the reverse water–gas reaction (RWGS) reaction, shifting the thermodynamic equilibrium towards propylene generation. Full article

Sorption-enhanced reverse water–gas shift (SE-RWGS), designated as COMAX, was studied using a Pt4A bifunctional catalyst (reactive adsorbent). The bifunctional Pt4A catalyst integrates CO₂ activation and reaction with water adsorption functionality, where the active phase is loaded onto a carrier that provides a surface area for Pt dispersion as well as H₂O adsorption capacity. The 0.3 wt% Pt-4A molecular sieve reactive sorbent was tested at a kg scale in a pressure swing (reactive) adsorption–regeneration process. More than 400 cycles over 50 days of operation were successfully demonstrated without significant decay. Cyclic stability was achieved, provided that the regeneration temperature was sufficiently high to ensure near-complete dehydration. The single-bead structure withstood the pressure swing operation effectively, with only a maximum of 2% of the total recovered reactive sorbent turning to fines (<500 μm). The successful integration of catalytic activity and water adsorption capacity into a single particle presents opportunities for the further intensification of sorption-enhanced reactions for CO₂ conversion. Full article

The CO₂ (Dry) Reforming of Methane (DRM) is a key process for reducing CO₂ and CH₄ emissions while producing syngas with an H₂/CO ratio of 1, ideal for Fischer–Tropsch synthesis. This study explores DRM and the Reverse Water Gas Shift (RWGS) reaction under mild conditions using Ru-based catalysts supported on CeO₂, YSZ, TiO₂, and SiO₂, with three reactant ratios: (i) stoichiometric, PCO₂ = 1 kPa, PCH₄ = 1 kPa, (ii) oxidizing, PCO₂ = 2 kPa, PCH₄ = 1 kPa, and (iii) reducing, PCO₂ = 1 kPa, PCH₄ = 4 kPa. The results highlight the importance of redox support for catalyst stability, with mobile lattice oxygen aiding carbon gasification. While Ru/CeO₂ is stable at high temperatures, it rapidly deactivates at low temperatures, emphasizing the need for precise metal particle size control. This work demonstrates the necessity of fine-tuning catalyst properties for more sustainable DRM, offering insights for next-generation CO₂ utilization catalysts. Full article