Platinum catalysed aqueous alcohol oxidation: experimental studies and reaction model discrimination

The platinum catalysed aqueous oxidation of alcohols and carboxylic acids is studied using electrochemical methods under circumstances typical for catalytic oxidation reactions, being 40 degrees C and pH 8. The investigated reactants are cyclohexanol (CL), methyl alpha-D-glucopyranoside (MGP), sodium oxalate (OA), and sodium formate (FA). Two catalytic oxidation regimes are distinguished: the intrinsic kinetic regime, and the oxygen transport limitation regime. Save OA, all reactants react on adsorbate-free, reduced platinum. On adsorbate-free, reduced platinum carbonaceous adsorbates are formed, inhibiting catalytic reactions. This situation is found when operating in the oxygen transport limitation regime. Under intrinsic kinetic conditions, platinum catalyst deactivation is caused by platinum oxide formation. Platinum oxide reduction is inhibited by the presence of adsorbed oxygen. A kinetic model for MGP oxidation, platinum deactivation, and reactivation is evaluated. (C) 2000 Elsevier Science B.V. All rights reserved.