| 摘要 |
PROBLEM TO BE SOLVED: To obtain a cerium-zirconium composite oxide which is excellent in heat resistance even against rapid temperature variation and can be suitably used for a promoter of a catalyst for cleaning exhaust gas by reforming a surface of a composite oxide containing cerium and zirconium utilizing a surface finishing agent such as a metal halide. SOLUTION: A cerium-zirconium composite oxide is immersed in a metal halide, an alkali halide, an alkali, a halogen-containing organic compound or the like and a part or whole part of a surface of the cerium-zirconium composite oxide is chemically treated. A cerium content of the composite oxide is 1-99 wt.%, preferably 50 wt.% or more, expressed in term of CeO2. Then residual surface finishing agents are removed by baking, washing with a solvent (e.g. methanol), sublimation and the like to reform the surface of the composite oxide. Thereby, the cerium-zirconium compound oxide having high oxygen absorbing-desorbing power in a <=400 deg.C low temperature region even after the composite oxide is oxidized and reduced at a >=1,000 deg.C high temperature is obtained.
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