Search Results (488)

This review explores CO₂ methanation and steam methane reforming (SMR) as two key thermochemical processes governed by reversible reactions, each offering distinct contributions to carbon-neutral energy systems. The objective is to provide a comparative assessment of both processes, highlighting how reaction reversibility can be strategically leveraged for decarbonization. The study addresses methane production via CO₂ methanation and hydrogen production via SMR, focusing on their thermodynamic behaviors, catalytic systems, environmental impacts, and economic viability. CO₂ methanation, when powered by renewable hydrogen, can result in emissions ranging from −471 to 1076 kg CO₂-equivalent per MWh of methane produced, while hydrogen produced from SMR ranges from 90.9 to 750.75 kg CO₂-equivalent per MWh. Despite SMR’s lower production costs (USD 21–69/MWh), its environmental footprint is considerably higher. In contrast, methanation offers environmental benefits but remains economically uncompetitive (EUR 93.53–204.62/MWh). Both processes rely primarily on Ni-based catalysts, though recent developments in Ru-based and bimetallic systems have demonstrated improved performance. The review also examines operational challenges such as carbon deposition and catalyst deactivation. By framing these technologies through the shared lens of reversibility, this work outlines pathways toward integrated, efficient, and circular energy systems aligned with long-term sustainability and climate neutrality goals. Full article

The mixed oxides of Ni/ZrO₂, Ni-Ca/ZrO₂, Ni-Ba/ZrO₂, and Ni-Ba-Ca/ZrO₂ were prepared using the co-precipitation method at a pH of precisely 8.3. The catalytic mixed oxides of Ni/ZrO₂, Ni-Ca/ZrO₂, Ni-Ba/ZrO₂, and Ni-Ba-Ca/ZrO₂ were characterized using x-ray diffraction XRD, Brunauer Emmett Teller (BET), scanning electron microscopy (SEM), and metal dispersion for the screening of phase purity, surface area, and morphology. The mixed oxides are subjected to CO₂-TPD to quantify the basicity of every composition. The mixed oxide catalysts of Ni/ZrO₂, Ni-Ca/ZrO₂, Ni-Ba/ZrO₂, and Ni-Ba-Ca/ZrO₂ were screened for oxythermal reforming of CH₄ with CO₂ in a fixed bed tubular reactor at 800 °C. Among all catalysts, the Ba- and Ca- loaded Ni-Ba-Ca/ZrO₂ showed high conversion by the decomposition of methane and CO₂ disproportionation throughout the time on stream of 29 h. The high activity with stability led to less coke formation over Ni-Ba-Ca/ZrO₂ over the surface. The stable syngas production with an active catalyst bed contributed to the improved bimetallic synergy. The high surface basicity of Ni-Ba-Ca/ZrO₂ may keep actively gasifying the formed soot and allow for further stable reforming reactions. Full article

This work deals with the catalytic steam reforming of raw syngas to increase the efficiency of coupling gasification with downstream processes (such as fuel cells and catalytic chemical syntheses) by producing high-temperature, ready-to-use syngas without cooling it for cleaning and conditioning. Such a combination is considered a key point for the future exploitation of syngas produced by steam gasification of biogenic solid fuel. The design and construction of an integrated gasification and gas conditioning system were proposed approximately 20 years ago; however, they still require further in-depth study for practical applications. A 3D model of the freeboard of a pilot-scale, fluidized bed gasification plant equipped with catalytic ceramic candles was used to investigate the optimal operating conditions for in situ syngas upgrading. The global kinetic parameters for methane and tar reforming reactions were determined experimentally. A fluidized bed gasification reactor (~5 kWth) equipped with a 45 cm long segment of a fully commercial filter candle in its freeboard was used for a series of tests at different temperatures. Using a computational fluid dynamics (CFD) description, the relevant parameters for apparent kinetic equations were obtained in the frame of a first-order reaction model to describe the steam reforming of key tar species. As a further step, a CFD model of the freeboard of a 100 kWth gasification plant, equipped with six catalytic ceramic candles, was developed in ANSYS FLUENT^®. The composition of the syngas input into the gasifier freeboard was obtained from experimental results based on the pilot-scale plant. Simulations showed tar catalytic conversions of 80% for toluene and 41% for naphthalene, still insufficient compared to the threshold limits required for operating solid oxide fuel cells (SOFCs). An overly low freeboard temperature level was identified as the bottleneck for enhancing gas catalytic conversions, so further simulations were performed by injecting an auxiliary stream of O₂/steam (50/50 wt.%) through a series of nozzles at different heights. The best simulation results were obtained when the O₂/steam stream was fed entirely at the bottom of the freeboard, achieving temperatures high enough to achieve a tar content below the safe operating conditions for SOFCs, with minimal loss of hydrogen content or LHV in the fuel gas. Full article

Ni-based catalysts have been widely used in catalytic reactions by researchers due to their advantages such as abundant resources, high catalytic activity and lower prices than precious metals. However, the problems of easy agglomeration and poor dispersion of Ni-based catalysts have hindered their large-scale application. Therefore, it is necessary to select a suitable preparation method to reduce the agglomeration of the catalyst and improve its dispersion. In this paper, the Ni-NiAl₂O₄/tourmaline composite material was prepared by using the microwave hydrothermal reduction method. The most favorable conditions for preparing NiAl₂O₄/tourmaline are as follows: using TEOA as the additive, the microwave hydrothermal temperature is 220 °C, the calcination temperature is 800 °C, and the addition amount of tourmaline is 7.4 wt.%. NiAl₂O₄ has a good dispersion over the surface of tourmaline support and the optimal NiAl₂O₄/tourmaline catalyst exhibits a specific surface area of 106.5 m²/g. Metallic nickel was reduced at 650 °C to further obtain Ni-NiAl₂O₄/tourmaline composites. Finally, the Ni-NiAl₂O₄/tourmaline composites showed significantly improved catalytic dry reforming of methane (DRM) activity compared to Ni-NiAl₂O₄ sample under low-temperature conditions (500–600 °C), meaning that the tourmaline carrier could effectively optimize the low-temperature catalytic performance of Ni-NiAl₂O₄. Full article

Olive mill wastewater (OMW) is a highly polluting effluent rich in organic pollutant compounds derived from olive oil production. In this work, the steam reforming reaction of OMW (OMWSR) was performed in a traditional reactor at 400 °C and different pressures (1–4 bar) to treat and valorize this effluent. A commercial catalyst (Rh/Al₂O₃) was used as a reference sample and several new catalysts were prepared (Ni-Ru/Ce-SiO₂) using different preparation methods to study their effect on the activity and stability. The best-performing catalysts were also subjected to long-term operation experimental tests (24 h). It was observed that the preparation method used for the catalysts synthesis influenced the catalytic performance of the samples. In addition, temperature-programmed oxidation (TPO) analysis of the used catalyst showed the presence of carbon deposits: the results showed that periodic oxidative regeneration improved the catalyst stability and sustained H₂ production. Finally, it was verified that the Ni-Ru/Ce³ catalyst stood out during the experimental tests, exhibiting high catalytic activity along the stability test at 400 °C and 1 bar: H₂ yield always over 7 mol_H2·mol_OMW⁻¹ and total organic carbon (TOC) conversion always higher than 94%. Despite these promising results, further research is needed to assess the economic feasibility of scaling up the process. Additionally, future work could explore the development of catalysts with enhanced resistance to deactivation by carbon deposition. Full article

The use of CH₄ and CO₂ as fuels in direct internal reforming solid oxide fuel cells (DIR-SOFCs) is a promising strategy for efficient power generation with reduced greenhouse gas emissions. In this study, Ni catalysts supported on Ce–Pr mixed oxides with varying Pr contents (0–80 mol%) were synthesized, calcined at 1200 °C, and tested for dry reforming of methane (DRM), aiming at their application as catalytic layers in SOFC anodes. Physicochemical characterization (XRD, TPR, TEM) showed that increasing Pr loading enhances catalyst reducibility and promotes the formation of the Pr₂NiO₄ phase, which contributes to the generation of smaller Ni⁰ particles after reduction. Catalytic tests revealed that all samples exhibited low-carbon deposition, attributed to the large Ni crystallites. The catalyst with 80 mol% Pr showed the best performance, achieving the highest CH₄ conversion (72%), a H₂/CO molar ratio of 0.89, and improved stability. These findings suggest that Ni/Ce_0.2Pr_0.8 could be a promising candidate for use as a catalyst layer of anodes in DIR-SOFC anodes. Although electrochemical data are not yet available, future work will evaluate the catalyst’s performance and durability under SOFC-relevant conditions. 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

Waste biomass gasification can contribute to the production of alternative and environmentally sustainable green fuels. Research at the CREC–UWO (Chemical Reactor Engineering Center–University of Western Ontario) considers an integrated gasification process where both electrical power, biochar, and tar-free syngas suitable for alcohol synthesis are produced. In particular, the present review addresses the issues concerning tar removal from the syngas produced in a waste biomass gasifier via a catalytic post-gasification (CPG) downer unit. Various questions concerning CPG, such as reaction conditions, thermodynamics, a Tar Conversion Catalyst (TCC), and tar surrogate chemical species that can be employed for catalyst performance evaluations are reported. Catalyst performance-reported results were obtained in a fluidizable CREC Riser Simulator invented at CREC–UWO. The present review shows the suitability of the developed fluidizable Ni–Ceria γ-alumina catalyst, given the high level of tar removal it provides, the minimum coke that is formed with its use, and the adequate reforming of the syngas exiting the biomass waste gasifier, suitable for alcohol synthesis. Full article

Biochar-based materials have gathered increasing attention as sustainable catalysts for carbon dioxide (CO₂) valorization, offering a green alternative to traditional metal-based systems. Produced from renewable biomass through pyrolysis, biochar possesses key features—such as high surface area, rich porosity and tunable surface chemistry—that make it particularly suited for heterogeneous catalysis. This review highlights recent advances in the use of biochar-derived catalysts for key CO₂ conversion reactions, focusing on cycloaddition to epoxides, dry reforming of methane and catalytic biomass upgrading. Emphasis is given to the role of biochar’s origin and preparation methods, which critically influence its structure, surface functionality and catalytic performance. Feedstocks rich in mineral content or oxygenated groups, for instance, can enhance CO₂ activation and product selectivity. Furthermore, tailored modifications—such as doping with heteroatoms or supporting metal nanoparticles—further boost catalytic activity and stability by tuning acid–base behavior, while maintaining low toxicity and cost-effectiveness. Compared to conventional catalysts, biochar-based systems offer advantages in low cost, recyclability and resistance to deactivation. Challenges remain in standardizing production methods, controlling structural variability, minimizing metal leaching and scaling up. This review presents biochar as a versatile, renewable platform for CO₂ utilization, highlighting the importance of rational design, feedstock selection and functionalization strategies for developing efficient, sustainable catalytic systems, in line with green chemistry and circular economy principles. Full article

This work explores the effect of the incorporation of CeO₂ into Co/SBA-15 catalysts in hydrogen production through acetic acid oxidative steam reforming as a bio-oil aqueous phase model compound. CeO₂ was incorporated (5–30 wt.%) to improve the physicochemical properties of the catalyst. XRD analysis confirmed that the addition of CeO₂ resulted in smaller Co⁰ mean crystallite sizes, while H₂-TPR showed enhanced reducibility properties. The catalytic performance was evaluated in the 400–700 °C range, S/C molar ratio = 2, O₂/C molar ratio = 0.0375, WHSV = 30.2 h⁻¹, and P = 1 atm. Catalysts containing 10 and 20 wt.% of CeO₂ exhibited the best catalytic performance, achieving nearly complete conversions and H₂ yield values, approaching thermodynamic equilibrium at 550 °C. Both samples maintained an acetic acid conversion above 90% after 30 h of time-on-stream, with H₂ yields above 55% along the steam reforming tests. This agrees with their lower coke formation rates (7.2 and 12.0 mg_coke·g_cat⁻¹·h⁻¹ for Co/10CeO₂-SBA15 and Co/20CeO₂-SBA15, respectively). Full article

The dry reforming of methane (DRM) converts two greenhouse gases, CH₄ and CO₂, into H₂ and CO, offering a crucial technological pathway for reducing greenhouse gas emissions and producing clean energy. However, the reaction faces two main challenges: high activation energy barriers require high temperatures to drive the reaction, while sintering and carbon deactivation at high temperatures are common with conventional nickel-based catalysts, which severely limit the further development of the methane dry reforming reaction. In this study, a nitrogen-doped carbon nanotube-loaded nickel catalytic system (Ni/NCNT) was developed to overcome the challenges caused by limited active sites while maintaining the stable structure of the Ni/CNT system. Ni/NCNT catalysts were prepared using different nitrogen precursors, and the impact of the mixing method on catalytic performance was examined. Characterization using H₂-TPR, XPS, and TEM revealed that nitrogen doping enhanced the metal–support interaction (MSI). Additionally, pyridine nitrogen species synergistically interact with nickel particles, modulating the electronic environment on the carbon nanotube surface and increasing catalyst active site density. The Ni/NCNT-IU catalyst, prepared with impregnated urea, exhibited excellent stability, with methane conversion decreasing from 85.0% to 82.9% over 24 h of continuous reaction. This study supports the use of non-precious-metal carbon-based catalysts in high-temperature catalytic systems, which is strategically important for the industrialization of DRM and the development of decarbonized energy conversion. Full article

Among biomass gasification syngas cleaning methods, non-catalytic reforming emerges as a sustainable and high-efficiency alternative. This study employed integrated experimental analysis and kinetic modeling to examine non-catalytic reforming processes of biomass-derived producer gas utilizing a synthetic tar mixture containing representative model compounds: naphthalene (C₁₀H₈), toluene (C₇H₈), benzene (C₆H₆), and phenol (C₆H₅OH). The experiments were conducted using a high-temperature fixed-bed reactor under varying temperatures (1100–1500 °C) and equivalence ratios (ERs, 0.10–0.30). The results obtained from the experiment, namely the measured mole concentration of H₂, CO, CH₄, CO₂, H₂O, soot, and tar suggested that both reactor temperature and O₂ content had an important effect. Increasing the temperature significantly promotes the formation of H₂ and CO. At 1500 °C and a residence time of 0.01 s, the product gas achieved CO and H₂ concentrations of 28.02% and 34.35%, respectively, while CH₄, tar, and soot were almost entirely converted. Conversely, the addition of O₂ reduces the concentrations of H₂ and CO. Increasing ER from 0.10 to 0.20 could reduce CO from 22.25% to 16.11%, and H₂ from 13.81% to 10.54%, respectively. Experimental results were used to derive a kinetic model to accurately describe the non-catalytic reforming of producer gas. Furthermore, the maximum of the Root Mean Square Error (RMSE) and the Relative Root Mean Square Error (RRMSE) between the model predictions and experimental data are 2.42% and 11.01%, respectively. In particular, according to the kinetic model, the temperature increases predominantly accelerated endothermic reactions, including the Boudouard reaction, water gas reaction, and CH₄ steam reforming, thereby significantly enhancing CO and H₂ production. Simultaneously, O₂ content primarily influenced carbon monoxide oxidation, hydrogen oxidation, and partial carbon oxidation. Full article

This study employed a two-stage fixed-bed pyrolysis-reforming reactor to investigate H₂ production behaviors from municipal solid waste (MSW) and biomass with their self-derived catalysts under different operating parameters. The self-derived catalysts are prepared by mechanically mixing pyrolysis-derived chars with CaO and iron powders. The main results are as follows: (1) The higher oxygen content in biomass facilitates oxidative dehydrogenation reactions, enabling in situ generation of H₂O, which results in a higher H₂/CO ratio for biomass compared to MSW under steam-free conditions. (2) There are optimal values for the reforming temperature and steam-to-feedstock ratio (S/F) to achieve best performance. In the presence of steam, MSW generally exhibits superior H₂ and syngas production performance to biomass; (3) Both MSW char (MSWC)- and biomass char (BC)-based catalysts showed satisfied H₂ production and tar cracking performance at 850–900 °C, and the MSWC-based catalyst demonstrated better catalytic activity than the BC-based catalyst due to its higher contents of several active metals. In addition, the iron powder can be recycled easily, proving the effectiveness of the self-derived convenient and cheap catalysts. Full article

This study investigates the effect of potassium (K) promotion on Pt/m-ZrO₂ catalysts in methanol steam reforming (MSR), revealing critical insights into reaction pathways and catalyst performance. While increasing K loading reduces catalytic activity, it selectively enhances the hydrogen-producing formate dehydrogenation and de-carboxylation pathway. Structural analyses using HR-TEM and DRIFTS show that higher K concentrations block Pt sites and promote agglomeration, reshaping catalytic behavior. Notably, the 3.1% K-promoted catalyst achieves high stability at 358 °C, with a CO₂ selectivity exceeding 80% and minimal methane formation, outperforming the unpromoted catalyst in terms of CO and CH₄ selectivity. Temperature studies further demonstrate reduced CO selectivity at higher temperatures, highlighting distinct advantages of K-doped catalysts. These findings underscore the role of K in enhancing surface basicity and its impact on formate interaction, offering valuable insights for optimizing MSR catalysts and advancing hydrogen production technologies. Full article

Photo-reforming waste polyethylene terephthalate (PET) in alkaline aqueous solutions is a novel approach for green hydrogen production. This study focuses on improving the catalytic efficiency of Pt/TiO₂ for the photo-reforming of waste PET using an innovative dark deposition method to deposit Pt single atoms on nano TiO₂ (Pt/TiO₂), thereby increasing the catalytic efficiency while reducing the cost of the catalyst. The precursor concentration was optimized to control the size and distribution of the Pt clusters/atoms, and the TiO₂ support was annealed at different temperatures to modify the properties of Pt/TiO₂. Nine Pt/TiO₂ catalysts were synthesized using different Pt precursor concentrations and annealing temperatures. The catalysts were characterized to measure their morphological, crystalline, and electronic properties, as well as their hydrogen yields via PET photo-reforming. The hydrogen conversion efficiency and external quantum yield (EQY) were calculated and compared with those of traditional direct-deposited catalysts. The correlation between the different characteristics of the dark-deposited and direct-deposited catalysts and their influence on the hydrogen yield in the photo-reforming process was statistically analyzed using principal component analysis. Catalysts deposited under dark conditions exhibited 5-fold and 7-fold enhancements in hydrogen conversion efficiency and EQY, respectively, compared to conventional catalytic systems. These findings indicate that the proposed catalytic system provides a viable solution for minimizing Pt loading, reducing the cost of the catalyst, and maintaining a higher hydrogen conversion efficiency. Full article