| 简介 |
PROBLEM TO BE SOLVED : To provide a catalyst for cleaning exhaust gas and a means capable of keeping the catalytic performance thereof over a long period of time even after being used.
SOLUTION : An upper layer 11 of the catalyst for cleaning exhaust gas has : a carrier containing an alumina-added ceria-zirconia compound oxide; rhodium deposited on the carrier; and lanthanum-added alumina and a lower layer 12 of the catalyst has : another carrier containing lanthanum-added alumina; palladium deposited on the carrier; another ceria-zirconia compound oxide containing at least one rare earth element; a different ceria-zirconia compound oxide; and barium sulfate. The ceria-zirconia compound oxide containing the rare earth element contains at least one selected from the group consisting of lanthanum, yttrium and praseodymium and has 0.02 or higher intense ratio [I(14/29) value] and 0.08 or lower intense ratio [I(28/29) value] when the ceria-zirconia compound oxide is heated at 1, 100°C in the atmosphere and a heated sample thereof is put under X-ray diffraction measurement, [I(14/29) value] means a ratio of the intensity when 2θ of an X-ray diffraction pattern (CuKα) is 14.5° to that when 2θ of the X-ray diffraction pattern (CuKα) is 29° and [I(28/29) value] means another ratio of the intensity when 2θ of the X-ray diffraction pattern (CuKα) is 28.5° to that when 2θ of the X-ray diffraction pattern (CuKα) is 29°.
SELECTED DRAWING : Figure 1
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