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

The platinum catalysed aqueous oxidation of alcohols and carboxylic acids i s studied using electrochemical methods under circumstances typical for cat alytic oxidation reactions, being 40 degrees C and pH 8. The investigated r eactants are cyclohexanol (CL), methyl alpha-D-glucopyranoside (MGP), sodiu m oxalate (OA), and sodium formate (FA). Two catalytic oxidation regimes ar e distinguished: the intrinsic kinetic regime, and the oxygen transport lim itation regime. Save OA, all reactants react on adsorbate-free, reduced pla tinum. On adsorbate-free, reduced platinum carbonaceous adsorbates are form ed, inhibiting catalytic reactions. This situation is found when operating in the oxygen transport limitation regime. Under intrinsic kinetic conditio ns, platinum catalyst deactivation is caused by platinum oxide formation. P latinum 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.