Efficient CO2 hydrogenation over mono- and bi-metallic RuNi/MCM-41 catalysts: Controlling CH4 and CO products distribution through the preparation method and/or partial replacement of Ni by Ru

CO2 methanation is receiving special attention nowadays due to the urgent environmental and energy need to control/recycle CO2 emissions. Herein the reaction is investigated over mono-and bi-metallic RuNi catalysts supported on mesoporous MCM-41 materials. Monometallic-Ru catalysts were always superior to their monometallic-Ni counterparts, while the bimetallic-RuNi, although outperforming monometallic-Ni, were inferior to monometallic-Ru. The CO2 methanation efficiency of monometallic-Ni catalysts was found to be highly dependent on the catalyst preparation method: One-pot synthesis provided catalysts almost completely ineffective for methanation, but very effective for the reverse-water-gas-shift (RWGS) reaction producing syngas at low temperatures. In striking contrast, compositionally identical Ni catalysts prepared by impregnation were efficient in CO2 methanation. An important for practical purposes redispersion of already stabilized large Ni crystallites was achieved by adding small amounts of Ru via the formation of core(Ru)-shell(Ni) nano -configurations. Detailed characterizations, kinetic and in-situ DRIFTS studies allowed the convincing interpretation of the novel findings.

Automated summary

CO2 methanation is a crucial area of research due to the urgent need to control and recycle CO2 emissions for environmental and energy purposes. This study investigates the reaction over mono- and bi-metallic RuNi catalysts supported on mesoporous MCM-41 materials. The results show that mono-metallic Ru catalysts outperform their Ni counterparts, and bi-metallic RuNi catalysts are inferior to mono-metallic Ru but better than mono-metallic Ni. The efficiency of mono-metallic Ni catalysts in CO2 methanation is highly dependent on the catalyst preparation method, with one-pot synthesis being ineffective and impregnation yielding efficient catalysts. By forming core(Ru)-shell(Ni) nano-configurations, small amounts of Ru can induce redispersion of stabilized large Ni crystallites, which is important for practical applications. Detailed characterizations and studies on kinetics and in-situ DRIFTS provide a convincing explanation for these novel findings.