Patent ID: 8796172

Claim:
An exhaust gas purification catalyst, comprising: a substrate; a catalyst coating layer that is formed of a porous support and is formed on a surface of the substrate; and a noble metal catalyst that is supported on the porous support of the catalyst coating layer, wherein: the catalyst coating layer is formed as a layer structure having an upper layer relatively farther from the substrate surface and a lower layer relatively closer to the substrate surface; Rh particles are supported as the noble metal catalyst in the upper layer; Pd particles are supported as the noble metal catalyst in the lower layer; the porous support of the lower layer that supports the Pd particles is formed by an ACZ composite oxide made of alumina (Al 2 O 3 ), ceria (CeO 2 ), and zirconia (ZrO 2 ); the ACZ composite oxide is produced by an alkoxide method; starting materials in the alkoxide method are a metal alkoxide and a metal salt; Al, Ce, and Zr are all converted into the metal alkoxide, or at least one of Al, Ce, and Zr is converted into the metal alkoxide; the metal salt is used for components other than the metal alkoxide; the starting materials are dissolved in a solvent and mixed and hydrolysis and polycondensation reactions are carried out, after which the ACZ composite oxide is obtained by a heat treatment; the ACZ composite oxide produced by the alkoxide method is a composite oxide in which the Al, Ce, and Zr become almost uniformly mixed at the atomic or oxide molecular level; and a Ce/Zr atomic ratio in the ACZ composite oxide is not more than 0.6.