Liquid Phase, Aerobic Oxidation of Benzyl Alcohol over the Catalyst System (Pt/TiO2+H2O)

Up to four different phases can be present in the heterogeneously catalyzed, liquid phase, aerobic oxidation of benzyl alcohol over Pt/TiO2. It is shown that the rate of benzyl alcohol oxidation is greatly enhanced upon addition of water to the initial reaction mixture but is not affected by the split between the two liquid phases. The rate of reaction correlates with the composition of water in the phase associated with the catalyst, i. e. the water-poor phase. Water may have various kinetic effects, e. g. a change in the distribution of surface species. It is argued on grounds of thermodynamic consistency that the liquid phase surrounding the catalyst is an intricate part of the catalyst in the aerobic benzyl alcohol oxidation over Pt/TiO2; water present in this liquid phase interacts with species on the surface altering the reaction kinetics.