ABSTRACT
Oxidations of polyols of commercial interest currently performed via stoichiometric oxidations with mineral acids or via enzymatic processes can be advantageously replaced by oxidation with air on metal supported catalysts. Thus, glyoxal solutions are oxidized to glyoxylic acid under controlled pH on active charcoal supported, platinum catalysts with a selectivity better than 70% at nearly total conversion. Factors limiting the diffusion of reactants and products in the catalyst are detrimental to the selectivity because any increase of the contact time favors the oxidation into oxalic acid. Glucose is oxidized into gluconate with a 99.3% yield on a Pd/C catalyst prepared by ion-exchange provided bismuth atoms are deposited on the Pd particles. A mechanism is proposed whereby bismuth acts as a cocatalyst preventing the oxygen poisoning of palladium.
