The role of water in ethanol oxidation over SnO2-supported molybdenum oxides

The role of water in the oxidation of ethanol to acetic acid on Sn-Mo-O cat alysts was studied by catalytic test and FTIR spectroscopy of adsorbed spec ies. The reaction showed a typical behavior of series reactions involving o xidation of ethanol to acetaldehyde and of the latter to acetic acid and CO 2. Addition of water to the feed gas decreased the oxidation rate and signi ficantly increased the selectivity to acetic acid, strongly contributing to decreasing the number of secondary products. FTIR analyses showed that wat er promotes desorption of ethanol and carboxylates, present as bridging and monodentate species. Decreasing catalytic rate values and increasing selec tivity to acetic acid in the presence of water follow from site blocking by hydroxyl groups.