Mechanistic aspects of Pd-catalyzed ethylene decomposition in vinyl acetate synthesis

Abstract

Vinyl acetate has a broad range of applications in the market. However, the side reactions of ethylene decomposition and CO2 formation have a significant effect on the selectivity of vinyl acetate synthesis. In this study, a comprehensive reaction network was calculated by the density functional theory (DFT) method to understand the mechanism of the side reactions. The DFT results indicated that the C-H bond is easier to break than C-C bond except for CCH species during ethylene decomposition on the Pd (100) surface. The introduction of Au on the alloy surface inhibits the decomposition of ethylene, which improves the selectivity of the reaction. The adsorbed O atom inhibits the first three dehydrogenation of ethylene but promotes the CCH species dehydrogenation. The pathway for the decomposition of ethylene is: CH2CH2 → CHCH2 → CHCH → CCH → C+CH, and the C-C bond cleavage of CCH is identified as the rate-determining step. The rate-determining step for CO2 formation is the combination of carbon and oxygen atoms to produce CO, and the alloy surface presents a high energy barrier, hindering CO2 production. This study presents a further mechanistic insight into ethylene decomposition and CO2 formation, which has implications for the control of side reactions in vinyl acetate synthesis.