The decomposition of alcohols (methanol, ethanol, n-propanol, i-propanol) on TiO2 and Pd/TiO2 catalysts has been studied using temperature programmed desorption. The alcohols mainly decompose via a dehydration pathway on TiO2 catalysts, with no evidence for reactions involving alpha C-C scission or dehydrogenation. However, the reaction pathway was fundamentally altered by the presence of Pd nanoparticles, and products of alpha C-C scission became dominant due to decarbonylation pathways. For the reaction with ethanol, there was no evidence of the dehydration product ethylene even though the surface is mainly composed of titania, indicating that diffusion of alkoxy species from the support to the Pd occurs efficiently during TPD. However, competing dehydration reactions did occur on Pd/TiO2 in the cases of n-propanol and i-propanol decomposition which is postulated to be due to more limited diffusivity of the bulkier alkoxides. (C) 2013 Elsevier B.V. All rights reserved.