Selective Oxidation of D-Glucose on Gold Catalyst

The selective oxidation of D-glucose to D-gluconic acid was performed at both controlled (7–9.5) and free pH values in an aqueous solution in the presence of a gold on carbon catalyst using dioxygen as the oxidant under mild conditions (323–373 K, pO2=100–300 kPa). No isomerization of glucose to fructose was observed during the reaction, and total selectivity to D-gluconate was obtained. A comparative study of gold and commercial palladium and platinum-derived catalysts highlighted the unique property of supported gold, i.e., it is active at low pH (2.5), whereas at a buffered higher pH (9.5), gold and bismuth-doped platinum-palladium on carbon catalysts show comparable selectivity, though gold has a higher activity. Moreover, upon recycling, gold is more stable toward deactivation, although this also depends on the operative pH.