Lavalley, A.M. Le Govic, G. Blanchard

Boulevard du Marechal Juin, 14050 CAEN-Cedex (France) 

Rhone-Poulenc-Recherches, 52 rue de La Haie-Coq, 93308 Aubervilliers (France) 

The purpose of this work is to compare the nature, amount and H2 reducibility of the sulfate species formed from SO2 oxidation on Pt catalysts supported on Ce02, Zr02 and a Ce02-Zr02 solid solution. Two techniques have essentially been used thermogravimetry and IR spectroscopy, both in static conditions. 

Previous works showed the importance of the surface in the formation and reduction of sulfate species (3,4). So, in addition to high surface area samples, the study has been extended to highly calcined samples (900°C) in order to study the ageing effect. 

The cerium-zirconium mixed oxide (Ce/Zr = 64/36, atomic ratio) as well as the pure ceria samples (both without and with Pt) were obtained by a Rhone-Poulenc proprietary process. The purity of the cerium used was higher than 99.5%. For the study of the interaction between Pt and cerium-zirconium mixed oxides, a hexachloroplatinic solution was used as a source of Pt. The OH groups on the surface of the mixed oxides were exchanged by PtCle ions in water. The material obtained was dried in an oven at 120°C and calcined in a muffle furnace at 500°C. For aged catalysts, the calcination was performed at 900°C for 6 hours. The Pt loading was 0.5% (weight %). 

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