COMPOSITE OXIDE FOR EXHAUST-GAS PURIFICATION CATALYST, PROCESS FOR PRODUCING SAME, COATING MATERIAL FOR EXHAUST-GAS PURIFICATION CATALYST, AND FILTER FOR DIESEL EXHAUST-GAS PURIFICATION

摘要

A composite oxide for an exhaust gas purification catalyst is provided which can burn PM in diesel engine exhaust gas at low temperatures and has a good S desorption property. The composite oxide for an exhaust gas purification catalyst is composed of Ce, Bi, Pr, R, and oxygen in a molar ratio of Ce:Bi:Pr:R = (1 - x - y - z) :x:y:z. The ratios of Ce, Bi, Pr, and R satisfy 0 < x + y + z ‰¤ 0.5 and preferably 0 < x ‰¤ 0.1, 0 < y ‰¤ 0.25, and 0 < z ‰¤ 0.3. Particularly, when R is Zr, the composite oxide exhibits a good S desorption property at a temperature of about 600°C and can recover its catalytic activity at low temperatures. Therefore, the exhaust gas purification catalyst is suitable as a PM combustion catalyst.