In the presented study, the deactivation of supported Nickel catalysts is analyzed during a PTK measurement. The deactivation for CO and CO2 methanation were used as example reactions, giving a clear insight into the reaction system. The results show that deactivation during CO2 methanation is governed by TOS rather than TOT and that it is apparently irreversible under the conditions applied here. At the same time, identical deactivation with respect to TOS is observed for both steady-state and periodic experiments. For CO methanation, the deactivation during PTK is less pronounced compared with the steady-state experiments and depends on the period duration. We attribute this observation to the presence of a partially reversible deactivation mechanism. The many dynamic parameters, which can be modulated during the analysis, indicate the high degree of freedom using the PTK method for deactivation studies.