Selective catalytic oxidation with air of glycerol and oxygenated derivatives on platinum metals

Abstract

Platinum metal catalysts, promoted or not with bismuth, have been designed to favour oxidation of either the primary or the secondary alcohol functions of glycerol in aqueous solution. Thus, on palladium catalyst oxidation of the primary function of glycerol predominates and glyceric acid is the chief product (70% yield at 90% conversion, pH=11) whereas on bismuth-promoted platinum catalyst oxidation of the secondary function prevails to give dihydroxyacetone (37% yield at 75% conversion, pH=2). Subsequent oxidation of glyceric acid on platinum gives the tartronate (61% yield at 94% conversion, pH=10–11); improved yields were obtained with the bismuth-promoted catalyst (83% yield at 90% conversion, pH=10–11). On bismuth-promoted platinum oxidation of glyceric acid gives hydroxypyruvic acid as the main product (64% yield at 75% conversion, pH=3–4) and under the same conditions tartronic acid is oxidised to mesoxalic acid (29% yield at 53% conversion, pH=1.5) bismuth adatoms have two roles: they prevent over-oxidation by strongly adsorbed acids and orientate the selectivity towards oxidation of the secondary alcohol function.