First principle analysis of the catalytic reaction pathways in the synthesis of vinyl acetate

Acetoxylation of ethylene over supported palladium and palladium/gold is a well established commercial route for the formation of vinyl acetate. While the overall reaction chemistry for the synthesis of vinyl acetate was uncovered some thirty years ago (Eur. Chem. News 1967; World Pet. Cong. Proc. 1968, U.S. Patent 1967 & 1977), the active catalytic surface ensembles, key reaction intermediates, and mechanism are still poorly understood. Issues such as the oxidation state of the active centers (Pd⁰ vs Pd²⁺), particle ensemble size (small clusters versus large particles, rate-determining elementary steps, secondary decomposition routes, and the structural and/or electronic role of Au, have yet to be resolved. Herein, we employ first-principle quantum chemical techniques to model a series of proposed elementary steps representative of vinyl acetate synthesis. Calculations using palladium and oxidized palladium particles of varying size provide a fundamental understanding of the elementary physicochemical steps in the oxidative coupling of ethylene and acetic acid in route to the formation of vinyl acetate.