In this paper, recent results on the de-oxygenation of some organic mo
lecules nitrobenzene, aliphatic carboxylic acids and benzoic acid are
reviewed. The activity pattern of metal oxides in these reactions has
been established, and several factors controlling the selectivity have
been identified. Selectivity in the de-oxygenation (and related) reac
tion is related to the universally operating Mars - Van Krevelen mecha
nism.