Transient Kinetic Investigation of Chain Growth and the Accumulation of Surface Carbon During CO Hydrogenation on Cobalt Catalysts

Abstract

CO hydrogenation is a promising approach for the storage of renewable energy in the form of hydrocarbons via the Fischer–Tropsch synthesis (FTS). Since transient operation of FTS reactors might be necessary and even be beneficial, transient kinetics for a rational catalyst and reactor design are essential. In order to advance the development of such transient kinetics, the periodic transient kinetics (PTK) method was applied to the CO hydrogenation on a Co/TiO₂ catalyst under FT-like conditions. It was revealed that there are two carbon species of different reactivity, C_α and C_β, present on the catalyst surface during the reaction. C_α forms fast, within a few seconds, and is highly reactive. Whereas C_β forms slowly, is accumulating on the surface over a longer time, and imposes an inhibiting effect. The results indicate an important role of the C_β species to chain growth and the formation of C₂₊ products. Finally, the transient experimental results were evaluated based on a material balance and the amounts of C_α and C_β present on the catalyst surface during the reaction were determined.