Gas-phase Oxidation of Alcohols with O2 and N2O Catalyzed by Au/TiO2: A Comparative Study

Abstract

Gas-phase oxidation of alcohols (EtOH, PrOH, i-PrOH, BuOH) to their carbonyl derivatives was used as test reaction to elucidate the mechanism of a low-temper- ature catalytic activity of Au/TiO2. The reactions were carried out in the presence of molecular oxygen, nitrous oxide as well as in the absence of the gas-phase oxidants. The relative contribution of oxidative and non-oxidative dehydrogenation pathways was thus estimated. The pre- sence of oxygen in the feed brought about to a double peak profile of catalytic activity as a function of temperature for all the alcohols. The low-temperature peak fells on 120-130 C. In contrast, the use of N2O as an oxidant gave rise to usual profile of catalytic activity, which is similar to that of anaerobic dehydrogenation of alcohols. The results obtained allowed to suggest the mechanism of the alcohols oxidation. The low temperature peak is probably related to participation of active oxygen species, generated from O2 on the catalyst surface. Oxidation with N2O is interpreted by preliminary dehydrogenation of alcohols to corre- sponding carbonyl derivatives followed by H2 oxidation.