The interaction between reactant / product gases and the catalyst surface as well as possible changes therein during exposure to the reaction gas mixture are analyzed by comparison of the pulse shapes before and after a CO2/H2/Ar multipulse sequence (section 3.1). Furthermore, we quantitatively analyzed the amounts of reactants consumed and products formed during the pulse sequence and the variations therein with time (section 3.2). Utilizing the high time resolution of TAP measurements, this provides information about the dynamics in the initial phase of the reaction. A central part of this paper are detailed TAP measurements on the interaction of CO2 with pre-oxidized catalyst employing isotope labelling techniques (section 3.3). Pulsing isotope marked C 18 O2 over the catalyst, we evaluate the oxygen exchange behavior on pre-oxidized catalysts after different oxidation procedures, including Oact deposition by exposing a reduced catalyst to a H2/CO2/Ar multipulse sequence, or to O2/Ar pulses, and by using a freshly calcined (O150) catalyst. Here we are particularly interested in deriving mechanistic information from a quantitative analysis of the C 18 O2 consumption and the distribution of the resulting CO2 isotopologues, which is analyzed in a quantitative model of the oxygen exchange process (section 3.4). Finally, we evaluate the stability of the adspecies formed during multi-pulse experiments with CO2/H2 and with C 18 O2 in temperature programmed desorption (TPD) measurements to identify possible differences in the stability of the adspecies (section 3.5).