Furthermore, the fact that high activities for the formation of rather stable side products reappear also at the beginning of the second and third subsequence means that these species can decompose and desorb during the time between subsequences, when the catalyst is held at 190 °C, but not exposed to the H2/CO2/Ar pulses. Hence, on the time scale of about 5 min and under present reaction conditions, these species are reversibly adsorbed. The same is true also for the reactive intermediates for CH4 formation, which must be replenished after each break in the pulse sequence.