Considerable amounts of ethanal may form in ethanol deep oxidation over platinum. The selectivity toward CO2increases at higher temperatures and at very low concentrations. An inhibiting effect of primarily formed aldehyde on ethanol conversion rate was observed; a power-law type equation rate is not applicable to describe the kinetics. The dependence of the selectivity on the contact time indicates that the gas-phase aldehyde may adsorb on the catalyst and further react to CO2. At lower temperature direct complete oxidation to CO2and partial oxidation occur as parallel competitive reactions; at higher temperature a series-parallel mechanism takes place