A density functional theory based elementary reaction mechanism for early steps of Fischer-Tropsch synthesis over cobalt catalyst. 1. Reaction kinetics

Abstract

Fischer-Tropsch synthesis (FTS), an efficient process for production of valuable fuel products from synthesized gas (syngas), has been the subject of many theoretical and experimental studies for decades. This work involves detailed molecular and microkinetic modeling of this catalytic process. By adopting an existing elementary reaction mechanism in the literature, density functional theory (DFT) calculations have been applied to model the kinetics and thermodynamics of FTS elementary steps on a flat Co(0001) catalyst surface. In this regard, using the DFT generalized gradient approximation (GGA) and canonical transition state theory, the rate constants and the activation energies of individual elementary reactions have been calculated. In addition, the necessity for modification of the existing proposed elementary steps and considerations of alternative mechanisms have been probed. Finally, it was determined that the favorable path for CO dissociation, as one of the key steps in the FTS, occurs through a hydrogen-assisted mechanism and the estimated rate parameters have been compared with those of other theoretical studies.