CO 2 Methanation over Supported Ru/Al 2 O 3 Catalysts: Mechanistic Studies by In situ Infrared Spectroscopy

Abstract Alumina supported ruthenium particles with an average diameter of 2 nm were prepared by a modified ethylene glycol reduction method. Catalytic methanation of CO 2 over this catalyst was studied by in situ FTIR spectroscopy. After pretreatment in H 2 , different types of adsorbed species were detected on the catalyst surface at 200 °C. Based on a series of targeted experiments under variation of gas composition, order of addition, reaction time and temperature, a reaction scheme and the rate‐determining steps of CO 2 methanation are proposed. Two potential reaction paths for the hydrogenation of CO 2 to form CH 4 were identified: (I) CO adsorbed on the Ru metal surface acted as active intermediate and the CO methanation followed. The dissociation of CO to form surface carbon represents the rate‐determining step. (II) Formyl species formed by hydrogenation of adsorbed CO 2 are the active intermediate and the formation of formyl was the rate‐determining step.