In Figure , the CH4 formation rate over TOS normalized to the initial activity is shown, both for steady-state and dynamic operation. As you can see here, both operation modes show an almost identical development over the 12 h TOS and both exhibit a 27 % reduction in CH4 formation rate. Hence, for CO2-methanation the deactivation during periodic operation is identical to that of steady-state operation. Since the deactivation in steady-state and PTK experiment show the same progress when evaluated with respect to TOS, the underlying processes associated with the deactivation can just take place under reactive atmosphere meaning that mechanism is a chemical deactivation. Interestingly, there is some controversy about the origin of the deactivation process in the Nickel catalyzed CO2 methanation. Mutz et al. assume deactivation due to oxidation, which is either a reversible or irreversible chemical deactivation . On the other hand, Ewald et al.