Kinetics modelling of Fischer–Tropsch synthesis over an industrial Fe–Cu–K catalyst

The kinetic experiments of Fischer–Tropsch synthesis (FTS) over an industrial Fe–Cu–K catalyst are carried out in a micro-fixed-bed reactor under the conditions as follows: temperature of 493–542 K, pressure of 10.9–30.9 bar, H2/CO feed ratio of 0.98–2.99, and space velocity of 4000–10 000 h−1. The effects of secondary reactions of olefins are investigated by co-feeding C2H4 and C3H6. A detailed kinetics model taking into account the increasingly proven evidence of the olefin re-adsorption mechanism is then proposed. In this model, different sites are assumed for FTS reactions and water gas shift (WGS) reaction, respectively. Rate expressions for FTS reactions are based on the carbide polymerisation mechanism, in which olefin re-adsorption is considered to be a reverse step of olefin desorption reaction. Rate expression for WGS reaction is based on the formate mechanism. An integral reactor model considering both FTS and WGS kinetics is used to describe the reaction system, and the simultaneous estimation of kinetic parameters is conducted with non-linear regression procedure. The optimal model shows that the rate determining steps in FTS reactions proceed via the desorption of hydrocarbon products and the adsorption of CO and the slowest step in WGS reaction is the desorption of gaseous carbon dioxide via formate intermediate species. The activation energies of FTS reactions and WGS reaction are in good agreement with literature values.