Au–Pd/C catalysts for glyoxal and glucose selective oxidations

Abstract

A series of Au–Pd/C catalysts were prepared on an activated carbon named SX PLUS (SX+) by fixing the pH of impregnation in aqueous phase at an optimal value for maximizing the interactions between metals and surface. This bimetallic association leads to highly active catalysts in the oxidation of glyoxal into glyoxalic acid and of glucose into gluconic acid, with the activity correlated to high surface Pd/C ratios measured by XPS and the presence of small metallic Pd particles, even if gold was present as big crystallites. A cooperative effect between the two metals was evidenced on the yield in carboxylic acids in both reactions, which is believed to arise from an interface between the two metals even if they are mostly present as separated phases. The incorporation of Au on Pd rather than the opposite and the concomitant activation of both metals influence positively the catalytic performance. The use of NaBH 4 as activating agent allowed the most active Au–Pd/C catalyst to be obtained, with similar performances to the best bimetallic Bi–Pd/C catalyst so far but without any metal leaching.