Selective oxidation of glycerol to sodium glycerate with gold-on-carbon catalyst: an insight into reaction selectivity

Glycerol was oxidised with oxygen in the presence of gold on carbon as the catalyst. Two types of catalysts were identified: one, characterised by well-dispersed nanoparticles with a mean diameter centred at 6 nm, did not maintain the initial selectivity of the oxidation at full conversion; the other, characterised by larger particles (>20 nm), showed constant selectivity from the beginning to the end of the reaction. The experimental conditions were studied to optimise glycerate production with selected catalysts, with particular regard to the effect of the NaOH/glycerol ratio, glycerol concentration, temperature, and glycerol/catalyst ratio. The best result was 92% selectivity to glycerate at full conversion, obtained by oxidising glycerol at 30 °C, with a NaOH/glycerol ratio of 4, a glycerol/Au = 500, and 0.3 M concentration.