Sol-gel processed fluorite-structured PrOy-ZrO2 mixed oxides deposited on alumina

Preparation of PrOy (Pr6O11) or single-phase fluorite-structured PrOy-ZrO2 mixed oxide, supported on high-surface-area gamma-alumina, was achieved for the first time by impregnation of gamma-alumina powder with Pr((OC3H7)-C-1 )(3) or a mixture of Pr((OC3H7)-C-1)(3)and Zr((OC3H7)-C-1)(4)(C3H7OH)-C-.1 and calcination 600 degrees C. Subsequent calculation at 900 degrees C caus ed partial transformation of Pr6O11 to PrAlO3 but only improved the crystal linity of the mixed oxide. Further calcination at 1200 degrees C led to com plete transformation df Pr6O11 but only partial disproportionation of PrOy- ZrO2 to PrAlO3 and ZrO2, transformation of gamma- to alpha-alumina was also inhibited in the case of the mixed oxide. In contrast, there was no eviden ce of any crystalline phase containing praseodymium upon calcination of gam ma-alumina powder impregnated with a mixture of praseodymium nitrate and zi rconium chloride in a 1 :0 or 1 : 1 molar ratio. These results show that pr aseodymium oxide can be supported on alumina and stabilized against reactio n with the alumina by the incorporation of zirconium in the form of the mix ed oxide, PrOy,ZrO2, provided it is deposited using alkoxide precursors. Th is stabilization should allow praseodymia to undergo redox processes and th us provide oxygen storage capacity when supported on alumina in a catalyst washcoat.