First, we characterized the shape of individual pulses after interaction of the reactants CO2 and H2 with the reduced Ru/Al2O3 catalyst during a sequence of stoichiometric H2/CO2/Ar (H2 : CO2 : Ar = 4 : 1 :1) pulses. This includes the reactants, the products CH4 and H2O, and the internal standard Ar. Under present reaction conditions, at 190 °C, this catalyst is solely active for CO2 methanation, while CO formation via the reverse water-gas shift (RWGS) reaction is inhibited . At higher temperatures, however, also CO formation via the RWGS is activated .