| 摘要 |
PROBLEM TO BE SOLVED: To provide a cerium system multiple oxide excellent in high temp. durability and capable of well exhibiting oxygen storage capacity even when a gaseous mixture supplied to an engine is controlled to the lean side by providing a specified compsn. SOLUTION: This cerium system multiple oxide is represented by the formula Ce1-x-yRxZryOxide, wherein R is Pr or Tb, 0.1<=x<=0.8, 0<=y<=0.8 and 0.1<=x+y<=0.9. A noble metal such as Rh, Pd or Pt as a catalyst is preferably carried on the multiple oxide. The multiple oxide can be adjusted to the desired compsn. by an alkoxide method or other method. Solns. of alkoxides of Ce, Pr or Tb and, optionally, Zr are mixed so as to attain a prescribed stoichiometric ratio the alkoxides are hydrolyzed by adding deionized water and the resultant hydrolyzates are heat-treated by drying at 50-200 deg.C for 1-48 hr and firing at 350-1,000 deg.C for 1-12 hr. |
