New evidence for the mechanism of the fischer-tropsch synthesis of hydrocarbons

Abstract

New mechanistic evidence is advanced for Fischer-Tropsch synthesis on Ru-loaded Y-type zeolites, Ru-on-silica and Co promoted on kieselguhr. The experiments were carried out in real Fischer-Tropsch conditions, i.e., at high growth rates. Experiments were done in pulse reactors and under transient reaction conditions. 13C-labeled carbon monoxide was used and addition of water and olefins to the synthesis gas was studied. From a series of well-chosen experiments it is deduced that carbon monoxide disproportionation initiates the reaction. Surface carbon is hydrogenated to methane and the reverse water-gas shift reaction accounts for water formation. Water reacts with surface carbon and forms hydroxy-species which initiate chain propagation. The mechanism accounts for a particle size effect and explains why polar conditions stimulate chain growth.