TPD measurements were performed directly after the multi-pulse experiments. The catalyst was heated (heating rate 25 °C min -1 ) from the reaction temperature of 190 °C to 500 °C (after CO2/H2 pulses) or 450 °C (after C 18 O2 pulses), respectively. After keeping the temperature for 5 min at that level, the catalyst was cooled to the initial temperature of 190 °C again (25 °C min -