| 摘要 |
PROBLEM TO BE SOLVED: To provide a composite oxide maximally developing the characteristics of respective metal elements constituting the composite oxide and useful as a carrier of an exhaust gas cleaning catalyst. SOLUTION: More than one kinds of aqueous solutions of acid salts of metals are prepared and a plurality of acid salts are successively added to an alkali aqueous solution capable of neutralizing all of the acid salts to form a precipitate which is, in turn, baked to manufacture the composite oxide wherein an oxide or solid solution comprising, for example, Al2 O3 , CeO2 and ZrO2 is dispersed in flocculated particles with a particle size of 20 μm or less as fine particles with a particle size of 50 nm or less and the flocculated particles are different in the distribution of metal elements between the surfaces and interiors thereof. For example, in constitution such that Al2 O3 is much in the surfaces of the flocculated particles, the surface concentration of CeO2 is lowered and, therefore, the deterioration of Rh can be suppressed in a case supporting Rh as a catalyst. If the composite oxide is precipitated from an aqueous solution containing Al and La, La2 O3 is contained only in Al2 O3 and the heat resistance of Al2 O3 is enhanced and Al2 O3 forms a solid solution along with CeO2 -ZrO2 to make it possible to suppress the lowering of oxygen occluding and discharge capacity. |
