SELECTIVE ELECTROGENERATIVE OXIDATION OF BENZYL ALCOHOL WITH PLATINUM-GRAPHITE PACKED-BED ANODES

The selective electrogenerative oxidation of benzyl alcohol in 1 M sul furic acid solutions was studied on several types of graphite supporte d platinum packed-bed anodes in a hybrid continuous-flow cell with an oxygen gas diffusion cathode. Benzaldehyde formed preferentially on al l three catalytic packed-beds under electrogenerative conditions (E(an ode) < 0.75 V) where the platinum catalyst was-not irreversibly oxidiz ed. Tin-palladium chloride graphite-pretreatment before platinum depos ition through ethanol reduction significantly enhanced catalytic activ ity. This electrocatalyst provided current densities as high as 77 mA cm(-2) (superficial packed-bed cross sectional area) with a platinum l oading of 0.89 wt% Pt on graphite at relative low polarization. The or igin of the catalytic activity is discussed and evidence is presented on the roles of tin and palladium. Benzyl alcohol oxidation appears to provide a sensitive probe reaction for demonstrating the existence of special types of catalytic centres.