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• Mn-promoted Ni catalysts on silica-modified alumina (SA) prepared. • Increasing Mn/Ni ratio yields more active and stable methanation catalysts. • Ni/SA methanation performance promoted by MnO at 1 bar and 20 bar. • Mn addition improves Ni reducibility and dispersion, CO 2 adsorption and activation. • Mn present as MnO clusters on Ni active phase in reduced catalysts. The viability of the Power-to-Gas (PtG) concept is strongly dependent on the development of highly active and stable methanation catalysts obtained from cheap and abundant elements. In this paper, the promotional effect of MnO on Ni catalysts supported on silica-modified γ-Al 2 O 3 (SA) was investigated in CO 2 and CO methanation on catalysts with Mn/Ni atomic ratios between 0 and 0.25. Significantly higher methanation rates and CH 4 selectivities were obtained for Mn-promoted compositions compared to Ni-only catalysts. The optimal NiMn/SA (Mn/Ni = 0.25) catalyst exhibited improved stability compared with unpromoted Ni/SA at 20 bar. The nature of the catalyst precursor and active catalyst was studied with STEM-EDX, XPS, and X-ray absorption spectroscopy (XAS). Evidence of a mixed Ni-Mn oxide in the catalyst precursor was obtained by EXAFS. EXAFS measurements revealed that the reduced catalyst consisted of metallic Ni particles and small oxidic Mn2+ species. Moreover, Mn addition improved the Ni dispersion and enhanced the Ni2+ reducibility by weakening the interaction between the Ni-oxide precursor and the support. A mechanistic study involving IR spectroscopy and steady-state isotopic (13CO 2) transient kinetic analysis (SSITKA) showed that the presence of Mn enhanced CO 2 adsorption and activation. [ABSTRACT FROM AUTHOR]

CO 2 utilization nowadays is one of the most important challenges posed by global warming. CO 2 conversion to methane is considered as a stage of the Power-to-X technology that uses green electricity for hydrogen production. Sustainable utilization of agricultural wastes is also a hot topic of the responsible consumption and production. In this work rice husk (RH) was used to produce Ni-based catalysts of CO 2 methanation. We suggested different treatments of RH for the synthesis of various catalyst supports. The purity of the support was found to be a crucial parameter determining the catalyst structure, activity, and selectivity. Sulfur, phosphorous, alkali and alkaline-earth metal impurities decreased the CO 2 conversion and methane selectivity, while promotion with manganese strongly enhanced the catalyst efficiency. Up to 86 % CO 2 conversion and 100 % methane selectivity were observed even at 250 °C over the Mn-promoted Ni-based catalysts supported on amorphous silica and purified RH ash. The stability of the catalyst depended on its specific surface area and chemical composition. The oxide-based supports with the highest specific surface areas were the most stable and active in CO 2 conversion. The RH-derived samples showed a promising activity at rather low operation temperatures and can be considered as green, cheap, and stable catalysts for the Power-to-X technology. [Display omitted] • Rice husk derived supports for Ni-based catalysts of CO 2 methanation. • A variety of supports produced by different treatments of rice husk. • 86 % CO 2 conversion and 100 % CH 4 selectivity at 250 °C over Mn-promoted catalysts. • Supports purity affects catalyst structure, activity, and selectivity. • Catalyst stability depends on specific surface area and composition of support. [ABSTRACT FROM AUTHOR]

A highly active and selective manganese oxide-promoted silica-supported cobalt catalyst for the Fischer-Tropsch reaction is reported. Co/MnO/SiO catalysts were prepared via impregnation of a cobalt nitrate and manganese nitrate precursor, followed by drying and calcination in an NO/He flow. The catalysts were studied with STEM-EELS, infrared spectroscopy measurements of adsorbed CO and Steady-State Isotopic Transient Kinetic Analysis experiments. Based on those experiments, a relation between C-selectivity and surface-coverages of CH-intermediates on cobalt was found. [ABSTRACT FROM AUTHOR]

Abstract: The Strong Electrostatic Adsorption (SEA) method was applied to the rational design of a promoted Co catalyst for Fischer–Tropsch (FT) synthesis. A series of Mn/Co/TiO2 catalysts were prepared by selective deposition of the [MnO4]− anion onto the supported Co3O4 phase. Qualitative ICP-OES and XPS measurements of the prepared catalysts with increasing Mn loading displayed the preferential association of the Mn species with Co3O4 and not the TiO2 support. The SEA preparation method seemed to minimize the migration of Mn away from the Co to the TiO2 support during reduction procedures to ensure a more intimate interaction between the Mn and the Co species during FT reactivity measurements. This led to an increase in light olefins, C5+ selectivity and chain growth probability. It is anticipated that the SEA preparation method is a viable synthesis strategy for other promoted and/or bimetallic catalyst systems where intimate contact between the catalyst components is highly desired. [Copyright &y& Elsevier]