CATALYTIC WALL-FLOW FILTER WITH AN AMMONIA SLIP CATALYST

• US 20180264446A1
• Filed: 03/20/2018
• Published: 09/20/2018
• Est. Priority Date: 03/20/2017
• Status: Active Grant

• Current Assignee: Johnson Matthey PLC
• Original Assignee: Johnson Matthey PLC
• Inventors: BURGESS, Garry Adam, CHANDLER, Guy Richard, FLANAGAN, Keith Anthony, MARVELL, David, PHILLIPS, Paul Richard
• Granted Patent: US 10,369,555 B2
• Time in Patent Office: Days
• CPC Class Codes: B01D 2255/1021 Platinum
• CPC Class Codes: B01D 2255/20746 Cobalt
• CPC Class Codes: B01D 2255/2092 Aluminium
• CPC Class Codes: B01D 2255/50 Zeolites
• CPC Class Codes: B01D 2255/502 Beta zeolites
• CPC Class Codes: B01D 2255/9022 Two layers
• CPC Class Codes: B01D 2255/9032 Two zones
• CPC Class Codes: B01D 2255/9035 Three zones
• CPC Class Codes: B01D 2255/9155 Wall flow filters
• CPC Class Codes: B01D 53/9418 for removing nitrogen oxides by selective catalytic reduction [SCR] using a reducing agent in a lean exhaust gas
• CPC Class Codes: B01D 53/9436 Ammonia
• CPC Class Codes: B01D 53/9468 in different layers
• CPC Class Codes: B01D 53/9472 in different zones
• CPC Class Codes: B01J 23/42 Platinum
• CPC Class Codes: B01J 23/888 Tungsten
• CPC Class Codes: B01J 29/763 CHA-type, e.g. Chabazite, LZ-218
• CPC Class Codes: B01J 35/19 Catalysts containing parts with different compositions
• CPC Class Codes: B01J 35/56 Foraminous structures having flow-through passages or channels, e.g. grids or three-dimensional monoliths
• CPC Class Codes: B01J 37/024 Multiple impregnation or coating
• CPC Class Codes: F01N 13/0093 the purifying devices are of the same type
• CPC Class Codes: F01N 2330/06 : Ceramic, e.g. monoliths
• CPC Class Codes: F01N 2370/04 : Zeolitic material
• CPC Class Codes: F01N 2610/02 : the substance being ammonia or urea
• CPC Class Codes: F01N 3/0222 : the structure being monolithic, e.g. honeycombs
• CPC Class Codes: F01N 3/035 : with catalytic reactors , e.g. catalysed diesel particulate filters
• CPC Class Codes: F01N 3/2066 : Selective catalytic reduction [SCR]
• CPC Class Codes: F01N 3/28 : Construction of catalytic reactors
• CPC Class Codes: Y02C 20/10 : of nitrous oxide (N2O)
• CPC Class Codes: Y02T 10/12 : Improving ICE efficiencies

Abstract

A catalytic wall-flow monolith filter for use in an emission treatment system comprises a wall flow monolith comprising a porous substrate having surfaces that define the channels and having a first zone extending in the longitudinal direction from a first end face towards a second end face for a distance less than the filter length and a second zone extending in the longitudinal direction from the second end face towards the first end face and extending in the longitudinal direction for a distance less than the filter length, wherein a first SCR catalyst is distributed throughout the first zone of the porous substrate, an ammonia oxidation catalyst is distributed throughout the second zone of the porous substrate and a second SCR catalyst is located in a layer that covers the surfaces in the second zone of the porous substrate.

Claims

1. A catalytic wall-flow monolith filter for use in an emission treatment system comprises a first end face, a second end face, a filter length defined by the distance from the first end face to the second end face, a longitudinal direction between the first end face and the second end face, and first and second pluralities of channels extending in the longitudinal direction,

wherein the first plurality of channels is open at the first end face and closed at the second end face, and the second plurality of channels is open at the second end face and closed at the first end face,

wherein the monolith filter comprises a porous substrate having surfaces that define the channels and having a first zone extending in the longitudinal direction from the first end face towards the second end face for a distance less than the filter length and a second zone extending in the longitudinal direction from the second end face towards the first end face and extending in the longitudinal direction for a distance less than the filter length,

wherein the first zone comprises a first SCR catalyst distributed throughout the porous substrate, and the second zone comprises an ammonia oxidation catalyst distributed throughout the porous substrate and a second SCR catalyst located in a layer that covers the surfaces in the second zone of the porous substrate.

2. The catalytic wall-flow monolith filter according to claim 1, wherein the second SCR catalyst is present only in the layer that covers the surfaces of the porous substrate in the second zone.

3. The catalytic wall-flow monolith filter according to claim 1, wherein the second SCR catalyst is present in the layer that covers the surfaces of the porous substrate in the second zone and in all or a portion of the porous substrate in the second zone.

4. The catalytic wall-flow monolith filter according to claim 3, wherein the second SCR catalyst is present in the layer that covers the surfaces of the porous substrate in the second zone and in all of the porous substrate in the second zone.

5. The catalytic wall-flow monolith filter according to claim 3, wherein the second SCR catalyst is present in the layer that covers the surfaces in the second zone of the porous substrate and in a portion of the porous substrate in the second zone.

6. The catalytic wall-flow monolith filter according to claim 1, wherein in the first zone, the first SCR catalyst does not cover a surface of the first or second pluralities of channels.

7. The catalytic wall-flow monolith filter according to claim 1, wherein the first SCR catalyst is the same as the second SCR catalyst.

8. The catalytic wall-flow monolith filter according to claim 1, wherein the first SCR catalyst is different than the second SCR catalyst.

9. The catalytic wall-flow monolith filter according to claim 1, wherein at least one of the first SCR catalyst and the second SCR catalyst comprise a small-pore molecular sieve, a medium-pore molecular sieve, a large-pore molecular sieve, or a base metal.

10. The catalytic wall-flow monolith filter of claim 9, wherein the small pore molecular sieve has a framework structure independently selected from the group consisting of AEI, AFT, CHA, DDR, EAB, ERI, GIS, GOO, KFI, LEV, LTA, MER, PAU, VNI and YUG.

11. The catalytic wall-flow monolith filter of claim 9, wherein at least one of the first SCR catalyst and the second SCR catalyst comprises copper beta zeolite.

12. The catalytic wall-flow monolith filter according to claim 1, wherein at least one of the first SCR catalyst and the second SCR catalyst comprises CeO₂ impregnated with W, CeZrO₂ impregnated with W, or ZrO₂ impregnated with Fe and W.

13. A catalytic wall-flow monolith filter according to claim 1, wherein the first SCR catalyst comprises a small-pore molecular sieve having a framework structure selected from the group consisting of AEI, AFT, CHA, DDR, EAB, ERI, GIS, GOO, KFI, LEV, LTA, MER, PAU, VNI and YUG structural families.

14. A catalytic wall-flow monolith filter according to claim 1, wherein the second SCR catalyst is a large-pore molecular sieve or a non-zeolite material selected from CeO₂ impregnated with W, CeZrO₂ impregnated with W, and ZrO₂ impregnated with Fe and W.

15. A catalytic wall-flow monolith filter according to claim 1, wherein the ratio of a length of the second zone to a length of the first zone in the longitudinal direction is from 1:

20 to 1;

5.

16. A catalytic wall-flow monolith filter according to claim 1, wherein the second SCR catalyst is present at from about 10% to about 50% of the length of the monolith substrate.

17. A catalytic wall-flow monolith filter according to claim 1, wherein oxidation catalyst comprises a noble metal.

18. A catalytic wall-flow monolith filter according to claim 1, further comprising a third zone located between the first zone and the second zone, wherein the third zone comprises the first SCR catalyst distributed throughout the porous substrate and the second SCR catalyst located in a layer that covers the surface of the porous substrate and is not distributed throughout the porous substrate.

19. The catalytic wall-flow monolith filter according to claim 18, wherein the third zone has a length up to 10% of the length of the monolith substrate.

20. A catalytic wall-flow monolith filter according to claim 18, further comprising a gap between at least a portion of:

(a) the first zone and the second zone;

(b) the first zone and the third zone;

or (c) the third zone and the second zone.

21. A catalytic wall-flow monolith filter according to claim 18, wherein there is no gap between at least a portion of:

(a) the first zone and the second zone;

(b) the first zone and the third zone;

or (c) the third zone and the second zone.

22. An emission treatment system for treating a flow of a combustion exhaust gas, the system comprising the catalytic wall-flow monolith filter according to claim 1, wherein the first end face is upstream of the second end face.

23. A method for the manufacture of a catalytic wall-flow monolith filter of claim 1, the method comprising:

(a) providing a porous substrate having a first end face and a second end face defining a longitudinal direction therebetween and first and second pluralities of channels extending in the longitudinal direction, wherein the first plurality of channels is open at the first end face and closed at the second end face, and wherein the second plurality of channels is open at the second end face and closed at the first end face;

(b) forming a first zone by selectively infiltrating the porous substrate with a washcoat comprising the first SCR catalyst,

(c) forming the portion of the second zone comprising the ammonia oxidation catalyst by selectively infiltrating the porous substrate with a washcoat comprising an ammonia oxidation catalyst, and

(d) forming a coating of a second SCR catalyst over the ammonia oxidation catalyst in the second zone, where the walls of the second plurality of channels are covered by the coating,

wherein step (b) can be performed before step (c) or step (c) can be performed before step (b).

24. A method for treating a flow of a combustion exhaust gas comprising NO_x, the method comprising passing the exhaust stream through the monolith of claim 1, wherein the first end face is upstream of the second end face.