CATALYST FOR EXHAUST GAS PURIFICATION

文件类型：PDF文档
文件大小：173K
A high NO x -purifying performance at high temperature conditions is achieved with a small amount of precious metal used. An exhaust gas-purifying catalyst (1) includes a substrate (2), a lower layer (3) formed on the substrate (2) and including a first composite oxide, palladium and platinum, and an upper layer (4) formed on the lower layer (3) and including a second composite oxide and rhodium. The first composite oxide includes cerium, zirconium, and an element selected from the group consisting of rare-earth elements other than cerium and alkaline-earth elements. A mass ratio of platinum with respect to palladium falls within a range of 1/50 to 1/20. The second composite oxide includes zirconium and an element selected from the group consisting of rare-earth elements other than cerium and alkaline-earth elements and has an atomic ratio of cerium with respect to zirconium smaller than that of the first composite oxide.