PREPARATION AND CHARACTERIZATION OF ZIRCONIUM DIOXIDE CATALYST SUPPORTS MODIFIED WITH RARE-EARTH ELEMENTS

ZrO2 catalyst supports modified with rare earth elements were prepared by coprecipitation from an aqueous solution of zirconium oxychloride and rare earth chlorides. The crystallization of amorphous hydrous ZrO2 was inhibited by doping with rare earths; the crystallization temperature was elevated as the amount and ionic radius of the rare earth modifiers was increased. Only modification using cerium had no effect on the crystallization process. The behavior of cerium was different from that of other rare earth elements with valency + 3. A metastable cubic phase was formed for ZrO2 modified with 10 mol.% lanthanum, neodymium and samarium by heating at 600-degrees-C. X-ray diffraction and Raman data indicated that the metastable phase had large microstrain and short-range ordering similar to tetragonal symmetry. Rare earth modified ZrO2 showed a large surface area and good thermal stability as a catalyst support. The carbon monoxide oxidation activity of iron was enhanced by modification with neodymium of ZrO2 supports. The results suggest the effectiveness of rare earth modified ZrO2 as catalyst supports.