Catalysts supported on alumina, ceria-zirconia, ceria/alumina and ceria-zirconia/alumina with three different nickel loadings were assessed by a series of in-situ temperature and spatial-resolved XANES experiments in both reducing and ethanol reforming atmospheres. Temperature-resolved XANES demonstrated that nickel particles are partially reduced during steam reforming of ethanol and are more oxidized after co-feeding oxygen. Spatial resolved XANES showed that the catalyst bed is predominantly oxidized at the entrance, where ethanol is mainly dehydrogenated to acetaldehyde. Ni particles are gradually reduced towards the exit of the reactor. The type of support does not affect directly the rate of carbon accumulation, but it influences the oxidation state of nickel particles, which also depends on their size. The Ni-0/Ni2+ ratio can be controlled by manipulating the type of oxidizing reactants (O-2, H2O), the reaction temperature and the size of Ni clusters. It is essential to have an adequate N-0/Ni2+ ratio to maintain catalyst stability for hydrogen production. Copyright (C) 2016, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.