它提供了一个含硅的铈复合氧化物，使用的配方的废气净化催化剂，它具有优良的耐热性和优异的还原率，可以保持高温环境下使用时，即使具有高的比表面积。 本发明表现出的复杂氧化物的韩非的表面积的BET法后的2〜20质量％的SiO的术语和5小时，在1000℃40米/ g以上烘焙，并且，在5小时后，并在1000℃烘烤含硅， 从得自该还原测得的温度增加的结果计算缩小率是50℃kkajiui 900℃具有代表至少30％，特别是适合作为助催化剂，用于在汽车中使用的废气净化催化剂的属性。

It provides a silicon-containing cerium complex oxide, a catalyst for purification of exhaust gas using the recipe and it has excellent heat resistance and excellent reduction rate, which can maintain a high specific surface area even when used under a high-temperature environment. Complex oxide of the present invention exhibit a containing 2 to 20% by weight of silicon in terms of SiO _2, and the at 1000 ℃ specific surface area by the BET method after a 5 hours firing 40m ² / g or more, for 5 hours and baked at 1000 ℃ then, the reduction rate was calculated from the result of the temperature rise from the reduction of measurement 50 ℃ to 900 ℃ has attributes representing at least 30%, in particular, is suitable as a co-catalyst for a catalyst for purification of exhaust gas used in automobiles.