FORMATION OF THE RHODIUM OXIDES RH2O3 AND RHO2 IN RH NAY/

The oxidation states of Rh in NaY supported catalysts have been studie d by temperature programmed reduction (TPR). After calcination of the exchanged catalyst to 380-degrees-C, both RhO2 and Rh2O3 are identifie d, besides small amounts of RhO+ and Rh3+. Quantitative reduction is p ossible for samples calcined at temperatures not exceeding 500-degrees -C. Re-oxidation of the reduced samples leads to formation of RhO2 and Rh2O3, with negligible protonolysis to Rh3+. The dioxide prevails aft er re-oxidation at 320-degrees-C, but the sesquioxide after oxidation at 500-degrees-C. In the temperature regime where both oxides coexist the reduction of NO with propane is catalyzed even at an O2/C3H8 ratio of 10. Total oxidation of propane reaches 80% at 350-degrees-C.