Raising the CO${}_x$ methanation activity of a Ru/γ-Al${}_2$O${}_3$ catalyst by activated modification of metal-support interactions

Ru/Al${}_2$O${}_3$ is a highly stable, but less active catalyst for methanation reactions. Herein we report an effective approach to significantly improve its performance in the methanation of CO${}_2$/H${}_2$ mixtures. Highly active and stable Ru/γ-Al${}_2$O${}_3$ catalysts were prepared by high-temperature treatment in the reductive reaction gas. Operando/in situ spectroscopy and STEM imaging reveals that the strongly improved activity, by factors of 5 and 14 for CO and CO${}_2$ methanation, is accompanied by a flattening of the Ru nanoparticles and the formation of highly basic hydroxylated alumina sites. We propose a modification of the metal-support interactions (MSIs) as the origin of the increased activity, caused by modification of the Al${}_2$O${}_3$ surface in the reductive atmosphere and an increased thermal mobility of the Ru nanoparticles, allowing their transfer to modified surface sites. (© 2020 The Authors. Published by Wiley-VCH GmbH)