Theoretical insights into the dissociation and oxidation of ethylene during vinyl acetate synthesis

Abstract

Gas phase synthesis of vinyl acetate from ethylene over Pd-Au catalyst is one of the mainstream processes. During the synthesis of vinyl acetate, the surface C generated by the dissociation of ethylene can be doped into the lattice of Au to form interstitial C. The synergistic effect of interstitial C and Au can promote the production of vinyl acetate. However, the formation mechanism of surface C is not clear. In addition, CO2 is formed during the dissociation and oxidation of ethylene. In order to reduce carbon emissions, it is also necessary to clarify the formation mechanism of CO2. In this study, the reaction mechanism for the dissociation and oxidation of ethylene on the PdAu(100) surface was investigated by density functional theory and kinetic Monte Carlo, and the formation pathways of surface C and CO2 were clarified.The results show that the generation pathway of surface C is CH2CH2→ CH2CH→ CHCH→ CHC→ CC→ CCO→ C+CO. The rate control step is CCO→C + CO with energy barrier of 1.39 eV and reaction heat of 0.52 eV. The generation pathway of CO2 is C → COH → CO → CO2. The rate control step is C+OH→COH with energy barrier of 0.71 eV and reaction heat of -1.12 eV. Clarification of the reaction mechanism for dissociation and oxidation of ethylene on the PdAu(100) surface and the formation pathways of surface C and CO2 can more specifically reduce the consumption of ethylene for by-products, better construct the synergism of surface C and Au, and reduce the emission of CO2 in the process of catalyst improvement and optimization.