CATALYST FOR THE ABATEMENT OF AMMONIA FROM THE EXHAUST OF GASOLINE INTERNAL COMBUSTION ENGINES

Abstract

Catalyst for the abatement of ammonia from the exhaust of gasoline internal combustion engines

The present invention relates to a catalyst comprising a carrier body having a length L extending between a first end face and a second end face, and differently composed material zones A, B and C arranged on the carrier body, wherein material zone A comprises rhodium and/or nickel and/or cerium; material zone B comprises platinum; and material zone C comprises a zeolite which is able to store ammonia and to catalyze the selective catalytic reduction of NOx.

Claims

1. Catalyst comprising a carrier body having a length L extending between a first end face and a second end face, and differently composed material zones A, B and C arranged on the carrier body, wherein material zone A comprises rhodium and/or nickel and/or cerium, material zone B comprises platinum, and material zone C comprises a zeolite which is able to store ammonia and to catalyze the selective catalytic reduction of NOx.

2. Catalyst according to claim 1, characterized in that material zone A comprises rhodium in an amount of 0.01 to 1 g/l, based on the volume of the carrier body and calculated as rhodium metal.

3. Catalyst according to claim 1, characterized in that material zone A comprises nickel in an amount of 1 to 100 g/l, based on the volume of the carrier body and calculated as NiO.

4. Catalyst according to claim 1, characterized in that material zone A comprises cerium in an amount of 1 to 100 g/l, based on the volume of the carrier body and calculated as CeO.sub.2.

5. Catalyst according to claim 1, characterized in that material zone B comprises platinum supported on aluminum oxide.

6. Catalyst according to claim 1, characterized in that material zone C comprises Cu-AEI, Cu-CHA or Fe-BEA.

7. Catalyst according to claim 1, characterized in that it comprises a material zone D which comprises a zeolite which is able to store ammonia and to catalyze the selective catalytic reduction of NOx.

8. Catalyst according to claim 7, characterized in that material zones C and D contain the identical components in the identical amounts.

9. Catalyst according to claim 1, characterized in that the material zones A, B, C and if present material zone D are present in the form of coatings on the carrier body.

10. Catalyst according to claim 9, characterized in that material zone A extends starting from the first end face of the carrier body over 10 to 90% of the length L, material zone B extends starting from the second end face of the carrier body over 10 to 90% of the length L and material zone C extends starting from the second end face of the carrier body over 10 to 90% of the length L, wherein L=L.sub.A+L.sub.B, wherein L.sub.A is the length of material zone A and L.sub.B is the length of the material zone B and wherein material zone C is located on top of material zone B.

11. Catalyst according to claim 9, characterized in that material zone A extends starting from the first end face of the carrier body over 10 to 90% of the length L, material zone B extends starting from the second end face of the carrier body over 10 to 90% of the length L material zone C extends starting from the second end face of the carrier body over 10 to 90% of the length L, and material zone D extends starting from the first end face of the carrier body over 10 to 90% of the length L, wherein L=L.sub.A+L.sub.B=L.sub.C+L.sub.D, wherein L.sub.A is the length of material zone A, L.sub.B is the length of the material zone B, L.sub.C is the length of material zone C and L.sub.D is the length of material zone D and wherein material zone C is located on top of material zone B and material zone D is located on top of material zone A.

12. Catalyst according to claim 11, characterized in that material zones A, B, C and D all extend over 50% of the length L and material zones C and D are identical.

13. Method for eliminating ammonia from gasoline exhaust gases, characterized in that the gasoline exhaust gas is conducted through a catalyst according to claim 1.

14. Exhaust gas purification system which comprises a three-way catalyst and a catalyst according to claim 1.

Description

[0051] In a first embodiment, [0052] material zone A extends starting from the first end face of the carrier body over 10 to 90% of the length L, [0053] material zone B extends starting from the second end face of the carrier body over to 90% of the length L and [0054] material zone C extends starting from the second end face of the carrier body over to 90% of the length L, [0055] wherein L=L.sub.A+L.sub.B, wherein L.sub.A is the length of material zone A and L.sub.B is the length of the material zone B and wherein material zone C is located on top of material zone B.

[0056] In a preferred first embodiment material zones A, B and C all extend over a length of 40 to 60% of the length L.

[0057] In a more preferred first embodiment material zones A, B and C all extend over 50% of the length L.

[0058] In a second embodiment, [0059] material zone A extends starting from the first end face of the carrier body over 10 to 90% of the length L, [0060] material zone B extends starting from the second end face of the carrier body over to 90% of the length L [0061] material zone C extends starting from the second end face of the carrier body over to 90% of the length L, and [0062] material zone D extends starting from the first end face of the carrier body over 10 to 90% of the length L,
wherein L=L.sub.A+L.sub.B=L.sub.C+L.sub.D, wherein L.sub.A is the length of material zone A, L.sub.B is the length of the material zone B, L.sub.C is the length of material zone C and L.sub.D is the length of material zone D and
wherein material zone C is located on top of material zone B and material zone D is located on top of material zone A.

[0063] In a preferred second embodiment material zones A, B, C and D all extend over a length of 40 to 60% of the length L.

[0064] In a more preferred second embodiment material zones A, B, C and D all extend over 50% of the length L.

[0065] In an even more preferred second embodiment material zones A, B, C and D all extend over 50% of the length L and material zones C and D are identical. This means that material zones C and D form a uniform layer on top of material zones A and B.

[0066] Catalysts according to the present invention can be produced by coating suitable carrier bodies in a manner known per se by means of coating suspensions, so-called washcoats.

[0067] The suspensions are obtained by methods known by the skilled persons and are then ground and applied to the carrier body by one of the standard coating methods. After each coating step, the coated part is dried in a hot air stream and in some cases calcined.

[0068] The Catalysts according to the present invention are suitable for purifying the exhaust gases of gasoline engines, in particular they are suitable to eliminate ammonia formed by an upstream three-way catalyst. Material zones A, B and C take on different functions.

[0069] Material zone A takes over the catalytic decomposition of ammonia to nitrogen in the absence of oxygen, i.e. under rich operating conditions. Material zone B takes over the oxidation of ammonia in the presence of oxygen, i.e. under lean operating conditions. Finally, material zone C and if present material zone D take over the storage and release of ammonia.

[0070] The present invention thus also relates to a method for eliminating ammonia from gasoline exhaust gases, which is characterized in that the gasoline exhaust gas is conducted through a catalyst as described and defined above. In one embodiment of the method the gasoline exhaust gas flows into the carrier body at the first end face and flows out of the carrier body at the second end face. In another embodiment of the method the gasoline exhaust gas flows into the carrier body at the second end face and flows out of the carrier body at the first end face.

[0071] The catalyst according to the present invention is used in particular as constituent of an exhaust gas purification system which includes a three-way catalyst. In such system the catalyst of the present invention is arranged so that the exhaust gas flows through the three-way catalyst first and subsequently through the catalyst according to the invention.

[0072] In addition to the three-way catalyst and the catalyst of the invention, the exhaust gas purification system can comprise a so-called gasoline particulate filter (GPF) which is able to reduce or eliminate particle emissions contained in the exhaust gas of gasoline engines.

[0073] Three-way catalysts and gasoline particle filters are known to the skilled person and extensively described in literature, including relevant textbooks.

[0074] FIG. 1 shows a catalyst of the present invention, where material zones A, B and C all extend over 50% of the length L and where material zone A starts from the first end face and material zones B and C from the second end face of the carrier body.

[0075] FIG. 2 shows a catalyst of the present invention which is based on the catalyst shown in FIG. 1 but which comprises in addition material zone D which extends starting from the first end face over 50% of the length L and which is located on material zone A.