Synthesis, structure and catalytic properties of Zr-Ce-Pr-O mixed oxides

Zr0.10(Ce1-xPrx)0.90O2 mixed oxides (x = 0-0.75) were prepared by coprecipitation (nitrates) or by the sol-gel route. Zirconium n-propoxide and cerium and/or praseodymium nitrates were used as precursors. "Sol-gel" oxides calcined at 900 C were shown to be cubic with a fluorite-type structure. Coprecipitated oxides could not be obtained as solid solutions. The BET surface area of these samples rapidly decreases for x above 0.5. Raman analysis confirmed that all oxides were cubic, and revealed the presence of oxygen vacancies. The optimum oxygen storage capacity (OSC) was obtained for Zr0.10(Ce0.50Pr0.50)0.90O2. It appears that the substitution of cerium by praseodymium in Zr0.10Ce0.90O2 mixed oxides leads to a material with improved redox properties. The presence of vacancies, associated with Pr3+/Pr4+ ions, is thought to be responsible for these enhanced OSCs. 24 refs.