1. The significant broadening of the pulse signals of the reactant CO2 as compared to the inert standard Ar points to sizeable interactions with the catalyst surface and repeated adsorption and desorption of CO2 on the way through the catalyst bed. In contrast, very narrow pulse profiles of the reactant H2 and also of the CH4 product point to rapid transport of these species. H2O, which can be generated as a final product of the methanation reaction on the one hand, but also by the reactive removal of active oxygen (Oact), interacts strongly with the catalyst, reflected by significant pulse broadening.