In this work, the effect of the metal nature on the reaction mechanism of the partial oxidation of ethanol on Pt/CeO2 and Rh/CeO2 catalysts was studied by using diffuse reflectance infrared spectroscopy (DRIFTS) analyses. The results showed that the nature of the metal affected the reaction mechanism. On Pt/CeO2 catalyst, adsorption of ethanol gives rise to ethoxy species, which can be decomposed, producing CH4, H-2 and CO, and dehydrogenated, forming acetaldehyde. The acetaldehyde species are dehydrogenated to acetyl species or may desorb. The acetyl species can be oxidized to acetate species or can be decomposed, forming CH4, H2 and CO. Furthermore, the acetate species previously formed can be decomposed to CH4, CO and/or oxidized to CO2 via carbonate species. On the other hand, for Rh-based catalyst, the ethoxy species can be also dehydrogenated to a cyclic compound (oxametallacycle). This intermediate is dissociated to CO, CHx and C-x which are oxidized to CO2. Furthermore, it was observed that the oxidation of acetyl species to acetate species and the formation of CO2 are favored depending on the presence of the O-2 in the feed on Pt/CeO2 and Rh/CeO2 catalysts, respectively. (C) 2007 Elsevier B.V. All rights reserved.