A Cu/CeO2/Al2O3 catalyst prepared by a single-step sol-gel method was studied for methanol steam reforming (SRM) to gain information on the oxidation state of Cu and the role of oxidized Cu species. The catalyst was tested in a new laboratory-made flow apparatus that allowed on-line analysis of the products and measurement of the oxidation state and dispersion of Cu in situ. The catalyst pre-reduced in H-2 was more active and selective than the not pre-reduced one. The oxidation state, evaluated after SRM tests, suggested the presence of a layer of oxygen atoms on the metallic Cu surface. Treating the pre-reduced catalyst with H2O vapour at 250 degrees C caused dissociative H2O chemisorption and led to a partial oxidation of Cu. The H2O oxidized sample reacted with CH3OH producing CO2 and H-2 as long as oxygen was present on the Cu surface. The results support an oxidation-reduction mechanism. (C) 2010 Elsevier B.V. All rights reserved.