CATALYTIC WALL-FLOW FILTER WITH PARTIAL SURFACE COATING

• US 20180119589A1
• Filed: 10/26/2017
• Published: 05/03/2018
• Est. Priority Date: 10/28/2016
• Status: Active Grant

• Current Assignee: Johnson Matthey PLC
• Original Assignee: Johnson Matthey PLC
• Inventors: CHANDLER, Guy Richard, FLANAGAN, Keith Anthony, PHILLIPS, Paul Richard, MARVELL, David
• Granted Patent: US 10,808,585 B2
• Time in Patent Office: Days
• CPC Class Codes: B01D 2255/2065 Cerium
• CPC Class Codes: B01D 2255/20776 Tungsten
• CPC Class Codes: B01D 2255/50 Zeolites
• 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 53/944 Simultaneously removing carbon monoxide, hydrocarbons or carbon making use of oxidation catalysts three-way-catalysts [TWC] B01D53/9445
• CPC Class Codes: B01D 53/9472 in different zones
• CPC Class Codes: B01J 23/56 Platinum group metals
• CPC Class Codes: B01J 37/0246 Coatings comprising a zeolite
• CPC Class Codes: F01N 2330/02 Metallic plates or honeycombs, e.g. superposed or rolled-up corrugated or otherwise deformed sheet metal
• CPC Class Codes: F01N 2330/06 Ceramic, e.g. monoliths
• CPC Class Codes: F01N 2330/60 Discontinuous, uneven properties of filter material, e.g. different material thickness along the longitudinal direction; Higher filter capacity upstream than downstream in same housing
• CPC Class Codes: F01N 2370/04 Zeolitic material
• 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: Y02T 10/12 Improving ICE efficiencies

Abstract

A catalytic wall-flow monolith filter for use in an emission treatment system comprises a wall flow substrate having a first and a second face, and first and second pluralities of channels. The first plurality of channels is open at the first face and closed at the second face. The second plurality of channels is open at the second face and closed at the first face. The monolith filter comprises a porous substrate having a first zone extending from the first face towards the second face and a second zone extending from the second face towards the first face. Each of the zones are less that filter length. A first catalytic material is distributed throughout the first zone of the porous substrate, and a second catalytic material covers at least a portion of the surfaces in the second zone of the porous substrate and is not distributed throughout the porous substrate.

Claims

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

wherein the first plurality of channels is open at the first face and closed at the second face, and the second plurality of channels is open at the second face and closed at the first 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 face towards the second face for a distance less than the filter length and a second zone extending in the longitudinal direction from the second face towards the first face and extending in the longitudinal direction for a distance less than the filter length,

wherein a first catalytic material is distributed throughout the first zone of the porous substrate, and

wherein a second catalytic material covers the surfaces in the second zone of the porous substrate and is not distributed throughout the porous substrate.

2. A catalytic wall-flow monolith filter according to claim 1, wherein in the second zone, the surfaces are free of catalytic material at the first plurality of channels.

3. A catalytic wall-flow monolith filter according to claim 1, wherein in the first zone, the catalytic material does not cover a surface of the first or second pluralities of channels.

4. A catalytic wall-flow monolith filter according to claim 1, wherein the filter has a cell density of 100 cpsi to 600 cpsi (15.5 cpscm to 93 cpscm).

5. A catalytic wall-flow monolith filter according to claim 1, wherein the mean minimum thickness of the substrate between adjacent channels is from 8 to 20 mil (0.02 to 0.05 cm).

6. A catalytic wall-flow monolith filter according to claim 1, wherein the catalytic material in the second zone covers the walls of the second plurality of channels as a coating having a thickness of between 10 μ

m to 80 μ

m, inclusive.

7. A catalytic wall-flow monolith filter according to claim 1, wherein the catalytic material distributed throughout the first zone of the porous substrate is the same as the catalytic material covering the surface of the second plurality of channels.

8. A catalytic wall-flow monolith filter according to claim 1, wherein the catalytic material distributed throughout the first zone of the porous substrate is different than the catalytic material covering the surface of the second plurality of channels.

9. A catalytic wall-flow monolith filter according to claim 1, wherein the catalytic material distributed throughout the first zone of the porous substrate and the catalytic material covering the surface of the second plurality of channels is independently selected from small-pore zeolites selected from the AEI, AFT, CHA, DDR, EAB, ERI, GIS, GOO, KFI, LEV, MER, PAU, VNI and YUG structural families, copper beta zeolite, CeO₂ impregnated with W, CeZrO₂ impregnated with W, and ZrO₂ impregnated with Fe and W.

10. A catalytic wall-flow monolith filter according to claim 1, wherein the catalytic material distributed throughout the first zone of porous substrate comprises a small-pore zeolite, preferably selected from the AEI, AFT, CHA, DDR, EAB, EM, GIS, GOO, KFI, LEV, MER, PAU, VNI and YUG structural families.

11. A catalytic wall-flow monolith filter according to claim 1, wherein the catalytic material covering the surface of the second plurality of channels is a large-pore zeolite, preferably a copper beta zeolite, or a non-zeolite material selected from CeO₂ impregnated with W, CeZrO₂ impregnated with W, or ZrO₂ impregnated with Fe and W.

12. 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, preferably about 1;

9.

13. A catalytic wall-flow monolith filter according to claim 1, wherein a portion of the second catalytic material overlaps a portion of the first zone of the filter up to 10%, preferably up to 5%, of the length of the monolith substrate.

14. A catalytic wall-flow monolith filter according to claim 1, wherein the second catalytic material overlaps the first zone of the filter and the second catalytic material is present at up to 100%, up to 90%, up to 85%, up to 80%, up to 75%, up to 70%, up to 65%, up to 60%, up to 55%, up to 50%, up to 45%, up to 40%, up to 35%, up to 30%, up to 25%, up to 20%, up to 25%, up to 20%, up to 15%, up to 10% or up to 5% of the length of the monolith substrate.

15. A catalytic wall-flow monolith filter according to claim 1, further comprising a gap between at least a portion of the first zone and the second zone.

16. A catalytic wall-flow monolith filter according to claim 1, wherein there is no gap between at least a portion of the first zone and the second zone.

17. The catalytic wall flow monolith of claim 1, wherein the wall flow monolith provides one or more of:

reduced soot accumulation, reduced back-pressure, lower light-off temperature, increased NH₃, HC or CO conversion, compared to a wall flow filter having the same components in a different configuration.

18. 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 face is downstream of the second face, or wherein the second face is downstream of the first face.

19. An emission treatment system of claim 18, wherein the system provides one or more of:

reduced soot accumulation, reduced back-pressure, lower light-off temperature, increased NH₃, HC or CO conversion, compared to a wall flow filter having the same components in a different configuration.

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

providing a porous substrate having a first face and a second 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 face and closed at the second face, and wherein the second plurality of channels is open at the second face and closed at the first face;

selectively infiltrating the porous substrate with a washcoat containing a first catalytic material to form a first zone which includes the first catalytic material and a second zone which is free from the first catalytic material, wherein the first zone extends in the longitudinal direction from the first face towards the second face and the second zone extends in the longitudinal direction from the second face and extends to the first zone; and

forming a coating of a second catalytic material, in the second zone, covering the walls of the second plurality of channels.

21. A method for treating a flow of a combustion exhaust gas comprising NO_x and particulate matter, the method comprising passing the exhaust stream through the monolith of claim 1, wherein the first face is downstream of the second face, or wherein the second face is downstream of the first face.

22. The method of claim 21, wherein the method provides for one or more of:

reduced particulate matter downstream of the wall flow monolith and increased NOx conversion, compared to a wall flow filter having the same components in a different configuration.