The catalyst performance and the deactivation profiles of CeZrO2 and Pt/CeZrO2 were evaluated for the ethanol decomposition and steam reforming of ethanol reactions at 773 K. Unpromoted CeZrO2 was quite stable whereas Pt/CeZrO2 catalyst deactivated for all feed compositions studied. A reaction mechanism was proposed based on diffuse reflectance infrared spectroscopy analyses carried out under reaction conditions. The decomposition of the dehydrogenated and the acetate species is facilitated by the presence of the metal and resulted in high selectivity to hydrogen, methane, CO and CO2 over Pt/CeZrO2 Diffuse reflectance infrared spectroscopy, transmission electron microscopy and temperature programmed oxidation and desorption analyses indicate that the loss of the Pt-support synergy leads to a buildup of carbonaceous residue, which is the likely reason of the deactivation of Pt/CeZrO2. In addition. once the interfacial boundary is lost, the demethanation of acetate becomes hindered, resulting in an increase in acetaldehyde selectivity with time onstream. (C) 2008 Elsevier B.V. All rights reserved.