CATALYST FOR PURIFYING EXHAUST GAS

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PROBLEM TO BE SOLVED : To provide a catalyst for purifying an exhaust gas having a high purifying performance in a hot region. SOLUTION : The catalyst for purifying the exhaust gas comprises a catalyst substrate and a catalyst coated layer formed on the catalyst substrate, wherein the catalyst coated layer has a layered structure including an inner layer a containing the following component (a-1) and component (a-2), and an outer layer b containing the following component (b-1) and component (b-2). The components (a-1) and (b-1) are a noble metal. The component (a-2) is a composite oxide of an element selected from the group consisting of (1) Ce, (2) Zr, and (3) a rare earth element, an alkaline earth element and Y. The ratio of (2) to (1) is in the range of 40/100 to 100/2 in terms of a weight ratio of CeO2 to ZrO2. The component (b-2) is a composite oxide containing at least (5) and (6) in elements selected from the group consisting of (4) Ce, (5) Zr, and (6) a rare earth element, an alkaline earth element and Y. The ratio of (5) to (4) is in the range of 40/100 or less to 100/2 in terms of a weight ratio of CeO2 to ZrO2. COPYRIGHT : (C)2008, JPO&INPIT