Kinetic and spectroscopic studies of vinyl acetate synthesis over Pd(100)

A kinetic study of vinyl acetate (VA) synthesis over a Pd(100) catalyst is described, and the effect of particle-size on this reaction ascertained by comparing the single crystal data with data from supported Pd catalysts (5 wt% Pd/SiO2, d(Pd) = 4.2 nm, and 1 wt% Pd/SiO2, d(Pd) = 2.5 nm). A negative reaction order with respect to ethylene and a positive order with respect to oxygen were found for the model and supported catalytic systems, whereas the catalytic stability was strongly dependent on the particle size. The mechanism for VA synthesis is proposed to be identical on all catalysts studied based on the similarities of the kinetic parameters. Carbon-containing species on the poisoned Pd(100) catalyst were investigated by X-ray photoelectron spectroscopy (XPS), and the coverage was estimated to be approximately 1.5 ML after VA synthesis.