Microkinetic Modelling of Cobalt-Support Interactions during Periodic Transient CO Hydrogenation

Renewable energy supply systems need storage concepts for times with low energy production. The CO hydrogenation towards CH4 and other hydrocarbons is a promising approach for long-term chemical storage of renewable energy. However, reaction kinetics and mechanisms are still under debate, especially possible metal-support interactions. We applied the periodic transient kinetics method to the CO hydrogenation on two cobalt-based catalyst materials with identical Co particle sizes and different support materials, SiO2 and TiO2. A lumped microkinetic model was developed for model-based evaluation of the experimental results. It was revealed that the different carbon species present on the catalyst surface during reaction apparently correspond to different reaction pathways. These pathways occur to a different extent, depending on the support material. Metal-support interactions between Co and TiO2 increase the CO adsorption strength, leading to both a lower overall activity and a higher selectivity towards C2+ hydrocarbons. We also included the adsorption of H2O on the support material in the microkinetic model, in order to appropriately reflect the experimentally observed oxygen and water dynamics by transient simulations.