To provide an exhaust gas purifying catalyst that requires a smallest possible quantity of rhodium for developing the activity effectively, so as to produce an excellent purifying performance economically, a zirconium complex oxide on which rhodium and platinum are previously supported, and a cerium
To provide an exhaust gas purifying catalyst that requires a smallest possible quantity of rhodium for developing the activity effectively, so as to produce an excellent purifying performance economically, a zirconium complex oxide on which rhodium and platinum are previously supported, and a cerium complex oxide on which platinum and/or palladium are previously supported are contained in an exhaust gas purifying catalyst.
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1. An exhaust gas purifying catalyst comprising:a lower layer directly coated on a catalyst and an upper layer formed on the lower layer, wherein the lower layer comprises an alumina the upper layer comprises a zirconium complex oxide supporting rhodium and platinum thereon, and a cerium complex oxi
1. An exhaust gas purifying catalyst comprising:a lower layer directly coated on a catalyst and an upper layer formed on the lower layer, wherein the lower layer comprises an alumina the upper layer comprises a zirconium complex oxide supporting rhodium and platinum thereon, and a cerium complex oxide supporting platinum thereon; and palladium is supported only on the alumina of the lower layer. 2. The exhaust gas purifying catalyst according to claim 1, wherein the zirconium complex oxide comprises zirconium and cerium in the proportion of a zirconium content being more than a cerium content, and wherein the cerium complex oxide comprises cerium and zirconium in the proportion of a cerium content being more than a zirconium content.3. The exhaust gas purifying catalyst according to claim 2, wherein the zirconium complex oxide is a heat resisting oxide expressed by the general formula (1) given below:Zr1?(a+b)CeaNbO2?c??(1) (In the formula, N represents alkali earth metal or rare earth metal, c represents oxygen vacancy, a represents a proportion of atom of 0.10-0.35, b represents a proportion of atom of 0-0.20, and 1?(a+b) represents a proportion of atom of 0.45-0.90), and wherein the cerium complex oxide is the heat-resisting oxide expressed by the general formula (2) given below: Ce1?(x+y)ZrxMyO2?z??(2) (In the formula, M represents alkali earth metal or rare earth metal, z represents oxygen vacancy, x represents a proportion of atom of 0.20-0.70, y represents a proportion of atom of 0-0.20, and 1?(x+y) represents a proportion of atom of 0.10-0.80). 4. The exhaust gas purifying catalyst according to claim 3, wherein the alkali earth metal represented by N in the general formula (1) and the alkali earth metal represented by M in the general formula (2) comprises at least one material selected from the group consisting of Mg, Ca, Sr and Ba, and wherein the rare earth metal represented by N in the general formula (1) and the rare earth metal represented by M in the general formula (2) comprises at least one material selected from the group consisting of Y, Sc, La, Pr and Nd.5. The exhaust gas purifying catalyst according to claim 1, which is in the form of a coating layer formed on a catalyst carrier.6. The exhaust gas purifying catalyst according to claim 1, wherein a quantity of rhodium supported is less than 1 g per liter of catalyst carrier.7. The exhaust gas purifying catalyst according to claim 1, wherein at least a part of the zirconium complex oxide and/or the cerium complex oxide is a solid solution.8. The exhaust gas purifying catalyst according to claim 1, wherein the platinum to be supported on the zirconium complex oxide and on the cerium complex oxide is supported in a proportion that a quantity of the platinum supported on the cerium complex oxide is in the range of 1-5 parts by weight per part by weight of the platinum supported on the zirconium complex oxide.9. An exhaust gas purifying catalyst comprising:a lower layer directly coated on a catalyst and an upper layer formed on the lower layer, wherein the lower layer comprises an alumina; the upper layer comprises a zirconium complex oxide supporting rhodium and platinum thereon, a cerium complex oxide supporting platinum thereon and an alumina supporting platinum thereon; and palladium is supported only on the alumina of the lower layer. 10. The exhaust gas purifying catalyst according to claim 9, wherein the zirconium complex oxide comprises zirconium and cerium in the proportion of a zirconium content being more than a cerium content, and wherein the cerium complex oxide comprises cerium and zirconium in the proportion of a cerium content being more than a zirconium content.11. The exhaust gas purifying catalyst according to claim 10, wherein the zirconium complex oxide is a heat resisting oxide expressed by the general formula (1) given below:Zr1?(a+b)CeaNbO2?c??(1) (In the formula, N represents alkali earth metal or rare earth metal, c represents oxygen vacancy, a represents a proportion of atom of 0.10-0.35, b represents a proportion of atom of 0-0.20, and 1?(a+b) represents a proportion of atom of 0.45-0.90), and wherein the cerium complex oxide is the heat-resisting oxide expressed by the general formula (2) given below: Ce1?(x+y)ZrxMyO2?z??(2) (In the formula, M represents alkali earth metal or rare earth metal, z represents oxygen vacancy, x represents a proportion of atom of 0.20-0.70, y represents a proportion of atom of 0-0.20, and 1?(x+y) represents a proportion of atom of 0.10-0.80). 12. The exhaust gas purifying catalyst according to claim 11, wherein the alkali earth metal represented by N in the general formula (1) and the alkali earth metal represented by M in the general formula (2) comprises at least one material selected from the group consisting of Mg, Ca, Sr and Ba, and wherein the rare earth metal represented by N in the general formula (1) and the rare earth metal represented by M in the general formula (2) comprises at least one material selected from the group consisting of Y, Sc, La, Pr and Nd.13. The exhaust gas purifying catalyst according to claim 9, which is in the form of a coating layer formed on a catalyst carrier.14. The exhaust gas purifying catalyst according to claim 9, wherein a quantity of rhodium supported is less than 1 g per liter of catalyst carrier.15. The exhaust gas purifying catalyst according to claim 9, wherein at least a part of the zirconium complex oxide and/or the cerium complex oxide is a solid solution.16. The exhaust gas purifying catalyst according to claim 9, wherein the platinum to be supported on the zirconium complex oxide and on the cerium complex oxide is supported in a proportion that a quantity of the platinum supported on the cerium complex oxide is in the range of 1-5 parts by weight per part by weight of the platinum supported on the zirconium complex oxide.
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이 특허에 인용된 특허 (5)
Sung Shiang ; Smaling Rudolf M., Catalyst composition.
Aubert Maryline,FRX ; Birchem Thierry,FRX ; Blanchard Gilbert,FRX ; Touret Olivier,FRX, Composition based on zirconium oxide and cerium oxide, preparation method therefor and use thereof.
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