Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Co catalysts, based on alumina supports modified with La2O3 and CeO2, have been explored in the steam reforming of ethanol (SRE). The addition of oxygen in the reactants, process called oxy-reforming of ethanol (ORE), and the effect of adding Pt as a promoter were also addressed. One of the main challenges of this system is to hinder carbon deposition that leads to catalyst deactivation. In this work, the stability against carbon deposition was correlated to the control of the Co2+/Co-0 ratio, which was addressed by in situ temperature-resolved X-ray absorption near edge spectroscopy (XANES). Temperature- and spatial resolved XANES indicated that the nature of supports, the presence/absence of Pt promoter and the composition of oxidants (water and oxygen) in the feed stream determine the degree of reduction of Co under reaction conditions. The control of the Co2+/Co-0 ratio can equilibrate the steps of ethanol activation and carbon oxidation, resulting in stable catalysts. (C) 2011 Elsevier Inc. All rights reserved.287124137VALEFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)FINEP (Financiadora de Estudos e Projetos)Brazilian Synchrotron Light Laboratory (LNLS)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)