Chemoselective catalytic oxidation of glycerol with air on platinum metals

The transesterification of triglycerides extracted from oilseeds to obtain biodiesel fuel yields up to 14% by weight of glycerol as by-product. The liquid-phase oxidation of glycerol with air on platinum catalysts was investigated to prepare valuable oxidation products such as glyceric acid or dihydroxyacetone. The effect of the pH (pH range 2–11) and of different metal catalysts was studied. The selectivity to glyceric acid can be as high as 70% at 100% conversion on Pd/C at pH 11. On Pt/C catalyst, glyceric acid was still the main product (55% selectivity); but the deposition of bismuth on platinum particles orientates the selectivity towards the oxidation of the secondary hydroxyl group to yield dihydroxyacetone with a selectivity of 50% at 70% conversion.