The exhaust gas purifying catalyst for a cerium-zirconium composite oxide

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PROBLEM TO BE SOLVED : To provide a cerium-zirconium compound oxide having improved durability at high temperature and stable OSC (oxygen storage capacity) performance. SOLUTION : The cerium-zirconium compound metallic oxide has at least 85% of the total mole number of Ce and Zr with respect to the whole metal mole number in the compound metallic oxide, 1/9 to 9/1 molar ratio of Ce/Zr and over 3.5 isoelectric point of the compound metallic oxide. Preferably the compound metallic oxide has 3/7 to 7/3 molar ratio of Ce/Zr and 3.8 to 5.0 isoelectric point and contains rare earth metals (excluding Ce) by 2as nuclei and ZrO2present around the nuclei. COPYRIGHT : (C)2004, JPO