Multimetallic catalysis based on heterometallic complexes and clusters.

CO2 methanation is a well-known reaction that is of interest as a capture and storage (CCS) process and as a renewable energy storage system based on a power-to-gas conversion process by substitute or synthetic natural gas (SNG) production. Integrating water electrolysis and CO2 methanation is a highly effective way to store energy produced by renewables sources. The conversion of electricity into methane takes place via two steps: hydrogen is produced by electrolysis and converted to methane by CO2 methanation. The effectiveness and efficiency of power-to-gas plants strongly depend on the CO2 methanation process. For this reason, research on CO2 methanation has intensified over the last 10 years. The rise of active, selective, and stable catalysts is the core of the CO2 methanation process. Novel, heterogeneous catalysts have been tested and tuned such that the CO2 methanation process increases their productivity. The present work aims to give a critical overview of CO2 methanation catalyst production and research carried out in the last 50 years. The fundamentals of reaction mechanism, catalyst deactivation, and catalyst promoters, as well as a discussion of current and future developments in CO2 methanation, are also included.

Supported Catalysts for CO2 Methanation: A Review

Methanation of coal-or biomass-derived carbon oxides for production of synthetic natural gas (SNG) is gaining considerable interest due to energy issues and the opportunity of reducing greenhouse gases by carbon dioxide conversion. The key component of the methanation process is the catalyst design. Ideally, the catalyst should show high activity at low temperatures (200-300 degrees C) and high stability at high temperatures (600-700 degrees C). In the past decades, various methanation catalysts have been investigated, among which transition metals including Ni, Fe, Co, Ru, Mo, etc. dispersed on metal oxide supports such as Al2O3, SiO2, TiO2, ZrO2, CeO2 etc. have received great attention due to their relatively high catalytic activity and selectivity. Furthermore, over the past few years, great efforts have been made both in methanation catalysts development and reaction mechanism investigation. Here we provide a comprehensive review to these most advancements, covering the reaction thermodynamics, mechanism and kinetics, the effects of catalyst active components, supports, promoters and preparation methods, hoping to outline the pathways for the future methanation catalysts design and development for SNG production.

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Recent advances in methanation catalysts for the production of synthetic natural gas

This Review describes recent advances in the design, synthesis, reactivity, selectivity, structural, and electronic properties of the catalysts for reforming of a variety of oxygenates (e.g., from simple monoalcohols to higher polyols, then to sugars, phenols, and finally complicated mixtures like bio-oil). A comprehensive exploration of the structure–activity relationship in catalytic reforming of oxygenates is carried out, assisted by state-of-the-art characterization techniques and computational tools. Critical emphasis has been given on the mechanisms of these heterogeneous-catalyzed reactions and especially on the nature of the active catalytic sites and reaction pathways. Similarities and differences (reaction mechanisms, design and synthesis of catalysts, as well as catalytic systems) in the reforming process of these oxygenates will also be discussed. A critical overview is then provided regarding the challenges and opportunities for research in this area with a focus on the roles that systems of ...

Catalytic Reforming of Oxygenates: State of the Art and Future Prospects.

Copper-containing cerium oxide materials have received considerable attention both in catalysis and electro-catalysis fields due to their unique physicochemical characteristics in conjunction to their lower cost compared to noble metals (NMs)-based catalysts. Nowadays, it is well documented that the complex Copper–Ceria interactions (either geometric or electronic) have a key role on the catalytic performance. Hence, considerable efforts have been devoted on the understanding and the fine-tuning of metal–oxide interactions. Despite the growing progress in the field, several crucial issues related to the influence of: i) particle’s shape and size, ii) active site’s chemical state, iii) charge transfer between interfacial sites, and iv) intrinsic defects (e.g., surface oxygen vacancies) on the interfacial activity are still under investigation. This survey summarizes the recent advances in the last 10 years on the fundamental origin of Copper–Ceria interactions and their implications on the catalytic activity. The insights lately obtained by means of: i) ex situ advanced characterization techniques, ii) in situ sophisticated studies (e.g., operando techniques), iii) theoretical analysis (e.g., DFT calculations), and iv) innovative probing approaches (such as the inverse CeO2/CuO model system) are provided. The state-of-the-art catalytic applications of CuO/CeO2 binary oxides (water gas shift (WGS) reaction, preferential oxidation (PROX) of CO, CO2 hydrogenation, selective catalytic reduction (SCR), N2O decomposition, etc.) in relation to the aforementioned aspects are discussed. Some guidelines towards the fine-tuning of the surface chemistry of CuO/CeO2 catalysts for real life energy and environmental application are provided.

The role of Copper–Ceria interactions in catalysis science: Recent theoretical and experimental advances

Performance of Ni/CeO2 catalysts for selective CO methanation in hydrogen-rich gas

Three noble metal catalysts (Rh-, Pt-, Ru/Ce0.75Zr0.25O2–δ) for reforming of hydrocarbons were studied in steam and autothermal process conditions. Each catalyst was prepared by sorption-hydrolytic deposition with a metal loading of 0.1 mmol/g. The main idea of this technical approach was to form a solution of “metal complex + alkaline agent” that was metastable at given conditions (temperature, concentrations) with respect to homogeneous metal hydroxide precipitation, due to the kinetic inertness of the metal complexes for ligand exchange. As the support surface accelerated heterogeneous nucleation and growth of metal hydroxide particles, addition of the support to the reagent mixture initiated the hydrolysis which led to uniform depositing of 1–2 nm metal particles over the support surface. The Rh-based catalyst synthesized surpassed the Ru- and Pt-based catalysts in activity and stability in that under the experimental conditions, complete n-hexadecane conversion and equilibrium reformate product distribution were observed for 1-wt. % Rh/Ce0.75Zr0.25O2–δ for 17 h. This catalyst also showed competitive performance in autothermal reforming of diesel fuel providing stable operation for 9 h.

Highly dispersed Rh-, Pt-, Ru/Ce0.75Zr0.25O2–δ catalysts prepared by sorption-hydrolytic deposition for diesel fuel reforming to syngas

The reactions of the CO and CO2 methanation in the excess of hydrogen were studied over Ni/CeO2 and Ni(Cl)/CeO2 catalysts prepared from nitrate and chloride precursors, respectively. Macrokinetic parameters of the CO and CO2 methanation over Ni/CeO2 and Ni(Cl)/CeO2 catalysts were determined. The nature of surface species during the CO and CO2 methanation over Ni/CeO2 and Ni(Cl)/CeO2 catalysts was studied by the Fourier transform infrared spectroscopy in situ technique. It was shown that the CO methanation proceeds similar ways over both Ni/CeO2 and Ni(Cl)/CeO2 catalysts via CO and H2 chemisorption on the surface of Ni particles. The CO2 methanation over Ni/CeO2 catalyst proceeds via the CO2 adsorption on the ceria surface and stepwise hydrogenation to methane through hydrocarbonate and formate intermediates by the hydrogen spilled over from Ni particles. With the Ni(Cl)/CeO2 catalyst, this reaction pathway is locked due to the ceria surface blockage by chlorine, to inhibit the CO2 methanation and therefore provide a high efficiency of Ni(Cl)/CeO2 catalyst in preferential CO methanation in the presence of CO2.

Pavel V. Snytnikov

Papers

Performance of Ni/CeO2 catalysts for selective CO methanation in hydrogen-rich gas

Highly dispersed Rh-, Pt-, Ru/Ce0.75Zr0.25O2–δ catalysts prepared by sorption-hydrolytic deposition for diesel fuel reforming to syngas

On the Mechanism of CO and CO 2 Methanation Over Ni/CeO 2 Catalysts

Selective CO methanation in H2-rich stream over Ni–, Co– and Fe/CeO2: Effect of metal and precursor nature

Preferential CO oxidation over bimetallic Pt-Co catalysts prepared via double complex salt decomposition