A detailed and in-depth study of the deactivation of Pt and/or Ni-based gamma-Al2O3 catalysts prepared by impregnation and acid and basic sal-gel methods, previously tested in glycerol aqueous phase reforming (APR) for H-2 production, has been made. The aim has been to get a further and advanced understanding of the factors behind this deactivation. Accordingly, all the used catalysts were systematically characterized by appropriate techniques, such as ICP-AES, XRD, XPS and TG/DGT-O-2. Some used samples were also examined by BET, TPD-NH3, TPR-H-2 and TEM. The characterization results corroborate the following: (i) a significant part of gamma-Al2O3 in sol-gel catalysts was structurally transformed into gamma-AlOOH, changing their textural properties, such as surface area and porosity, surface acidity and metal dispersion, and (ii) the Ni metallic particles in the impregnated catalysts underwent major agglomeration, while the Ni particles in the sol-gel counterparts were more affected by re-oxidation phenomena. Data obtained by ICP-AES and thermal analysis indicate, respectively, that Pt and Ni phase leaching and the formation of highly graphitized coke were negligible. However, some adsorption of carbonaceous molecular species has been detected on some catalysts. All these observations clearly confirm that the metallic and acid active sites of Pt and/or Ni-based gamma-Al2O3 catalysts experimented quantitative and qualitative modifications during the glycerol APR process that compromised their catalytic performances. (C) 2013 Elsevier B.V. All rights reserved.