Abstract: Disclosed is a vapor phase catalytic oxidation process for preparing an aliphatic carboxylic acid ester of a monoaromatic compound having 1 to 2 hydroxymethyl substituents, such as benzyl acetate, p-methylbenzyl acetate, p-xylylenediacetate, benzyl propionate and benzyl butyrate. A gaseous feed comprised of a benzene compound having 1 to 2 methyl substituents, an aliphatic monocarboxylic acid having 2 to 4 carbon atoms and molecular oxygen is contacted with an improved catalyst. The metal ingredients of the catalyst consist essentially of (a) palladium, (b) arsenic and (c) at least one metal selected from alkali metals and alkali earth metals, and the atomic ratio of palladium:arsenic:the alkali or alkali earth metal is 1:0.05-4:0.1-10.