The Periodic Transient Kinetics Method for Investigation of Kinetic Process Dynamics Under Realistic Conditions: Methanation as an Example

Due to rising interest for the integration of chemical energy storage into the electrical power grid, the unsteady-state operation of chemical reactors is gaining more and more attention with emphasis on heterogeneously catalyzed reactions. The transient response of those reactions is influenced by effects on different length scales, ranging from the active surface via the individual porous catalyst particle up to the full-scale reactor. The challenge, however, is to characterize unsteady-state effects under realistic operation conditions and to assign them to distinct transport processes. Therefore, the periodic transient kinetics (PTK) method is introduced, which allows for the separation of kinetic process dynamics at different length scales experimentally under realistic operation conditions. The methodology also provides the capability for statistical analysis of the experimental results and therefore improved reliability of the derived conclusions. Therefore, the PTK method provides the experimental basis for model-based derivation of reaction kinetics valid under dynamic conditions. The applicability of the methodology is demonstrated for the methanation reaction chosen as an example process for heterogeneously catalyzed reactions relevant for chemical energy storage purposes.