| Summary: | Understanding the chain growth mechanism is of vital importance for the development of catalysts with enhanced selectivity towards long-chain products in cobalt-catalyzed Fischer-Tropsch synthesis. Herein, we discriminate various C<sub>1</sub> + C<sub>1</sub> coupling reactions by theoretical calculations and kinetic isotope experiments. CH<sub>x(x=0−3)</sub>, CO, HCO, COH, and HCOH are considered as the chain growth monomer respectively, and 24 possible coupling reactions are first investigated by theoretical calculations. Eight possible C<sub>1</sub> + C<sub>1</sub> coupling reactions are suggested to be energetically favorable because of the relative low reaction barriers. Moreover, five pathways are excluded where the C<sub>1</sub> monomers show low thermodynamic stability. Effective chain propagation rates are calculated by deconvoluting from reaction rates of products, and an inverse kinetic isotope effect of the C<sub>1</sub> + C<sub>1</sub> coupling reaction is observed. The theoretical kinetic isotope effect of CO + CH<sub>2</sub> is inverse, which is consistent with the experimental observation. Thus, the CO + CH<sub>2</sub> pathway, owing to the relatively lower barrier, the high thermodynamic stability, and the inverse kinetic isotope effect, is suggested to be a favorable pathway.
|
|---|
