The reaction of vinyl acetate with Pd(1Â 1Â 0) studied with TPD and molecular beams

The adsorption and reaction of vinyl acetate with the clean Pd(1 1 0) surface has been investigated using temperature programmed desorption and molecular beam reaction measurements. These show that, under low pressure conditions, the main reaction pathway above 400 K is total dehydrogenation to yield hydrogen and carbon dioxide in the gas phase, and surface carbon. This occurs at a steady state, notwithstanding the fact that carbon is being deposited continuously onto the surface. The reaction continues because the vast majority of this carbon is lost from the surface to the bulk of the sample. Between about 320-380 K the reaction profile is somewhat different; the molecule dissociates at the CH3COOCHCH2 bond, producing the most stable intermediate, the acetate, and the reaction stops after the build-up of adsorbed acetate and surface carbonaceous species. At ∼300 K, the products are very similar to those for acetaldehyde adsorption (namely, methane, CO and some surface carbon), and they evolve in a non-steady state manner due to the build up of adsorbed CO on the surface. Thus the mechanism is dominated here by dissociation at the CH3COOCHCH2 bond, and formation of the acetyl intermediate. Consideration is given to the connection between these data and vinyl acetate synthesis.