Patent ID: 8048389

Claim:
A method for producing a cerium oxide-zirconium oxide-based mixed oxide comprising: a first step of adding a sulfating agent to a cerous salt to obtain a slurry containing a cerous sulfate-alkali metal mixed salt; a second step of adding a cerium salt and a zirconium salt to the slurry; a third step of adding an alkali to the mixture obtained in the second step to obtain a mixed hydroxide containing (a) cerium hydroxide and (b) zirconium hydroxide mixed with cerium hydroxide; and a fourth step of heat-treating the mixed hydroxide to obtain a mixed oxide containing (a) cerium oxide and (b) zirconium oxide solid solution containing cerium; the cerium oxide-zirconium oxide-based mixed oxide comprising (a) cerium oxide and (b) zirconium oxide solid solution containing cerium, wherein (1) the weight ratio of CeO 2 : ZrO 2 is 60:40 to 90:10, (2) (a) the cerium oxide and the zirconium oxide solid solution containing cerium are present as a mixture, (b) the zirconium oxide solid solution containing cerium is tetragonal or cubic, and (3) in the case of having loaded platinum onto the cerium oxide-zirconium zirconium oxide-based mixed oxide following heat treatment for 3 hours at 900° C., the particle size of platinum is 200 nm or less.