Nickel supported catalysts for hydrogen production by reforming of ethanol as addressed by in situ temperature and spatial resolved XANES analysis

•Nickel particles are partially reduced during SRE and are more oxidized in ORE.•Spatial-resolved XANES showed that the catalyst bed is oxidized at the entrance.•The type of support does not affect directly the rate of carbon accumulation.•Ni0/Ni2+ ratio depends on oxidizing reactants, temperature and size of Ni clusters.•Ni0/Ni2+ ratio is essential to equilibrate ethanol activation and carbon oxidation.

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 Ni0/Ni2+ ratio can be controlled by manipulating the type of oxidizing reactants (O2, H2O), the reaction temperature and the size of Ni clusters. It is essential to have an adequate Ni0/Ni2+ ratio to maintain catalyst stability for hydrogen production.

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