Effect of Ce-Zr mixed oxides on the thermal stability of transition aluminas at elevated temperature

Ce-Zr mixed oxides is a kind of promoted oxygen storage capability material widely used in three-way catalysts. Various contents (10, 20, 30 and 40%) of Ce-Zr were physically mixed into the pure gamma-alumina for surface modification. The thermal stability of a series of Ce-Zr/Al2O3 supports was examined. Differential thermal analysis shows Ce-Zr mixed oxides increase the alpha-alumina transformation temperature up to 1222degreesC. The powder X-ray diffraction studies show that minor theta-alumina phase still exists in the samples with greater than or equal to 20% Ce-Zr doping content after aging at 1050degreesC for 50 h. The best stabilizing effect is observed in the case of 20% Ce-Zr/Al2O3. Even after the accelerated aging test, it maintains an acceptable specific surface area (24 m(2) g(-1)) in relation with the delayed transformation of theta into alpha-alumina. (C) 2004 Elsevier B.V. All rights reserved.