Improved Performance of Ru/γ‐Al2O3 Catalysts in the Selective Methanation of CO in CO2‐Rich Reformate Gases upon Transient Exposure to Water‐Containing Reaction Gas

Abstract To better understand the role of water in the selective methanation of CO in CO 2 ‐rich reformate gases on Ru/Al 2 O 3 catalysts, the influence of exposing these catalysts to H 2 O‐rich reformate gases on their reaction characteristics in transient experiments was investigated by employing kinetic and in situ spectroscopic measurements as well as ex situ catalyst characterization. Transient exposure of the ruthenium catalyst to wet reaction gas (5 or 15 % H 2 O) results in significantly enhanced activity and selectivity for CO methanation in subsequent reactions in dry reformate compared with activation and reaction in dry reformate directly. Operando X‐ray absorption spectroscopy results reveal that this is in accordance with a significant decrease in ruthenium particle size, which is stable during subsequent reaction in dry reformate. The implications of these data and additional results from in situ IR spectroscopy on the role and influence of H 2 O on the reaction, also in technical applications, are discussed.