Journal of Physics and Chemistry of Solids (2009)

In-situ XAS study of the Cu and Ce local structural changes in a CuO CeO2/Al2O3 catalyst under propane reduction and re-oxidation
Geert Silversmit, Hilde Poelman, Veerle Balcaen, Philippe Heynderickx, Maria Olea, Sergey Nikitenko, Wim Bras, Philippe F. Smet, Dirk Poelman, Roger De Gryse, Marie-Fran?oise Reyniers, Guy Marin
Journal of Physics and Chemistry of Solids 70 (2009) 1274-1284

Abstract
The redox behaviour of a CuO?CeO2/Al2O3 catalystis studied under propane reduction and re-oxidation. The evolution of the local Cu and Ce structure is studied with in-situ transmission X-ray absorption spectroscopy (XAS) at the CuK and Ce L3 absorption edges. CuO and CeO2 structures are present in the catalyst as such. No structural effect on the local Cu structure is observed upon heating in He up to 873K or after pre-oxidation at 423K. Exposure to propaneat reaction temperature (600?763K) fully reduces the Cu2+ cations towards metallic Cu0. Quick EXAFS spectra taken during reduction show a small amount of intermediate Cu1+ species. Parallel to the CuO reduction, CeO2 is also reduced in the same temperature range. About 25% of the Ce4+ reduces rapidly toCe3+ in the 610?640K temperature interval, while beyond 640K a further slower reduction of Ce4+ to Ce3+ occurs. At763K, Ce reduction is still in complete with 32% of Ce3+. Re-oxidation of Cu and Ce is fast and brings back the original oxides. The propane reduction of the CuO?CeO2/Al2O3 catalyst involves both CuO and CeO2 reduction at similar temperatures, which is ascribed to an interaction between the two compounds.

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