In-situ DXAS study on the reduction behavior of Ce0.9Zr0.1O2 nanocatalysts

M.G. ZIMICZ; LARRONDO S.A.; R.J. PRADO; D.G. LAMAS

Activity Report of the Brazilian Synchrotron Light Laboratory

Editora Cubo

Año: 2011 p. 1 - 2

1518-0204

Ceria-based catalysts has been thoroughly studied for the combustion of hydrocarbons, especially for methane total oxidation, due to the well-known easy and reversible redox process of cerium cations (Ce4+/Ce3+) when exchanging oxygen with the surroundings. It is well established that zirconia and ceria form solid solutions in all proportions with different crystal structures, and that the incorporation of zirconia in the ceria structure enhances de reducibility of Ce4+ cations, which strongly depends on both composition and crystal structure of the as-formed solid solution. Nevertheless, the true mechanism of Ce4+ reduction process is not completely known, especially in the case of nanocatalysts, where higher surface to bulk Ce ratio could have important influence in the reduction mechanism of Ce4+ cations and in the catalytic activity in the methane catalytic oxidation reaction. The aim of this investigation was to study the evolution of the Ce3+/Ce4+ ratio in Ce-Zr nanosized mixed oxide catalysts under a reducing atmosphere, by in-situ DXAS experiments at the Ce LIII-edge. In this way, we were able to measure XANES spectra as function of temperature and atmosphere. The compositionally homogeneous mixed oxide tested had nominal composition Ce0,9Zr0,1O2 and was synthesized via different a-aminoacid-nitrate gel-combustion processes using glycine, lysine and alanine as fuels.