Catalyst system for reducing nitrogen oxides

Patent metadata

Field	Value
Publication number	US-10443463-B2
Application number	US-201515328658-A
Country	US
Kind code	B2
Filing date	Aug 12, 2015
Priority date	Aug 13, 2014
Publication date	Oct 15, 2019
Grant date	Oct 15, 2019

Abstract

The invention relates to a catalyst system for reducing nitrogen oxides, which comprises a nitrogen oxide storage catalyst and an SCR catalyst, wherein the nitrogen oxide storage catalyst consists of at least two catalytically active washcoat layers on a supporting body, wherein a lower washcoat layer A contains cerium oxide, an alkaline earth compound and/or alkali compound, as well as platinum and palladium, and an upper washcoat layer B, which is arranged over the washcoat layer A, contains cerium oxide, platinum and palladium, and no alkali compound and no alkaline earth compound. The invention also relates to a method for converting NOx in exhaust gases of motor vehicles that are operated by means of engines that are operated in a lean manner.

First claim

The invention claimed is:

1. A catalyst system for reducing nitrogen oxides, comprising
a nitrogen oxide storage catalyst and an SCR catalyst, wherein
the SCR catalyst contains a small-pore zeolite with a maximum ring size of eight tetrahedral atoms and a transition metal,
the nitrogen oxide storage catalyst comprises at least two catalytically active washcoat layers A and B on a supporting body,
the washcoat layer A is arranged directly on the supporting body and comprises cerium oxide, an alkaline earth compound and/or an alkali compound, as well as platinum and palladium,
the washcoat layer B is arranged over the washcoat layer A and comprises cerium oxide, as well as platinum and palladium, and is free of alkali and alkaline earth compounds,
a ratio of cerium oxide in washcoat layer B to cerium oxide in washcoat layer A, calculated in kg/m 3 (g/L) and in relation to the volume of the supporting body, is 1:2 to 3:1, and
the sum of cerium oxide in washcoat layer A and washcoat layer B, calculated in kg/m 3 (g/L) and in relation to the volume of the supporting body, is 100 to 240 kg/m 3 (100 to 240 g/L), and
wherein a ratio of platinum to palladium in each of the washcoat layers A and B is 2:1 to 18:1.

2. The catalyst system according to claim 1 , wherein the washcoat layer B comprises cerium oxide in a quantity of 46 to 180 kg/m 3 (from 46 to 180 g/L).

3. The catalyst system according to claim 1 , wherein the washcoat layer A comprises cerium oxide in a quantity of 14 to 95 kg/m 3 (from 14 to 95 g/L).

4. The catalyst system according to claim 1 , wherein the total washcoat loading of the supporting body is 300 to 600 kg/m 3 (300 to 600 g/L), in relation to the volume of the supporting body.

5. The catalyst system according to claim 4 , wherein the loading of washcoat layer A amounts to 150 to 500 kg/m 3 (150 to 500 g/L), and the loading of washcoat layer B amounts to 50 to 300 kg/m 3 (50 to 300 g/L), in relation to the volume of the supporting body in each case.

6. The catalyst system according to claim 4 , wherein the loading of washcoat layer A amounts to 250 to 300 kg/m 3 (250 to 300 g/L), and, the loading of washcoat layer B amounts to 100 to 200 kg/m 3 (100 to 200 g/L), in relation to the volume of the supporting body in each case.

7. The catalyst system according to claim 1 , wherein the alkaline earth compound in washcoat layer A comprises magnesium oxide, barium oxide, and/or strontium oxide.

8. The catalyst system according to claim 1 , wherein the SCR catalyst comprises a zeolite that belongs to the AEI, CHA, KFI, ERI, LEV, MER, or DDR structure type and that is exchanged with cobalt, iron, copper, or mixtures thereof.

9. The catalyst system according to claim 1 , wherein the SCR catalyst comprises a zeolite of a chabazite type that is exchanged with copper, iron, or copper and iron.

10. The catalyst system according to claim 1 , wherein the nitrogen oxide storage catalyst and the SCR catalyst are arranged on different supporting bodies.

11. A catalyst system for reducing nitrogen oxides, comprising
a nitrogen oxide storage catalyst and an SCR catalyst, wherein
the SCR catalyst contains a small-pore zeolite with a maximum ring size of eight tetrahedral atoms and a transition metal,
the nitrogen oxide storage catalyst comprises at least two catalytically active washcoat layers A and B on a supporting body,
the washcoat layer A is arranged directly on the supporting body and comprises cerium oxide, an alkaline earth compound and/or an alkali compound, as well as platinum and palladium,
the washcoat layer B is arranged over the washcoat layer A and comprises cerium oxide, as well as platinum and palladium, and is free of alkali and alkaline earth compounds,
a ratio of cerium oxide in washcoat layer B to cerium oxide in washcoat layer A, calculated in kg/m 3 (g/L) and in relation to the volume of the supporting body, is 1:2 to 3:1, and the sum of cerium oxide in washcoat layer A and washcoat layer B, calculated in kg/m 3 (g/L) and in relation to the volume of the supporting body, is 100 to 240 kg/m 3 (100 to 240 g/L), and wherein
the washcoat layer A comprises
cerium oxide in a quantity of 14 to 95 kg/m 3 (from 14 to 95 g/L),
platinum and palladium in a mass ratio of 8:1 to 10:1, and
magnesium oxide and/or barium oxide;

the washcoat layer B comprises
platinum and palladium in a mass ratio of 8:1 to 10:1, and
cerium oxide in a quantity of 46 to 180 kg/m 3 (from 46 to 180 g/L); and

the SCR catalyst comprises a zeolite or a molecular sieve with a chabazite structure, the zeolite or molecular sieve containing copper in a quantity of 1 to 10 wt %, calculated as CuO and in relation to the SCR catalyst.

12. A catalyst system for reducing nitrogen oxides, comprising
a nitrogen oxide storage catalyst and an SCR catalyst, wherein
the SCR catalyst contains a small-pore zeolite with a maximum ring size of eight tetrahedral atoms and a transition metal,
the nitrogen oxide storage catalyst comprises at least two catalytically active washcoat layers A and B on a supporting body,
the washcoat layer A is arranged directly on the supporting body and comprises cerium oxide, an alkaline earth compound and/or an alkali compound, as well as platinum and palladium,
the washcoat layer B arranged over the washcoat layer A and comprises cerium oxide, as well as platinum and palladium and is free of alkali and alkaline earth compounds,
a ratio of cerium oxide in washcoat layer B to cerium oxide in washcoat layer A, calculated in kg/m 3 (g/L) and in relation to the volume of the supporting body, is 1:2 to 3:1, and the sum of cerium oxide in washcoat layer A and washcoat layer B, calculated in kg/m 3 (g/l) and in relation to the volume of the supporting body, is 100 to 240 kg/m 3 (100 to 240 g/L), and, wherein
the washcoat layer A comprises
cerium oxide in a quantity of 25 to 120 kg/m 3 (from 25 to 120 g/L),
platinum and palladium in a mass ratio of 8:1 to 10:1, and
magnesium oxide and/or barium oxide;

the washcoat layer B comprises
platinum and palladium in a mass ratio of 8:1 to 10:1, as well as and
cerium oxide in a quantity of 50 to 180 kg/m 3 (from 50 to 180 g/L); and

the SCR catalyst comprises a zeolite or a molecular sieve with a chabazite structure, the zeolite or molecular sieve containing copper in a quantity of 1 to 10 wt %, calculated as CuO and in relation to the SCR catalyst.

13. A method for converting NO x in an exhaust gas of a motor vehicle that operates an engine in a lean manner, comprising
feeding the exhaust gas over a catalyst system according to claim 1 .

14. The catalyst system according to claim 1 , wherein the nitrogen oxide storage catalyst and the SCR catalyst are arranged on the same supporting body.

Assignees

• Umicore Ag & Co Kg

Inventors

• Hoyer Ruediger
• Utschig Thomas
• Schiffer Michael
• Seyler Michael
• Schuetze Frank-Walter

Classifications

• F01N3/281

  Metallic honeycomb monoliths made of stacked or rolled sheets, foils or plates · CPC title

• F01N13/009

  having two or more separate purifying devices arranged in series · CPC title

• F01N3/2828

  Ceramic multi-channel monoliths, e.g. honeycombs · CPC title

• B01D2255/20738

  Iron · CPC title

• B01D2255/20746

  Cobalt · CPC title