Exhaust system for a lean-burn internal combustion engine including SCR catalyst

Patent metadata

Field	Value
Publication number	US-9259684-B2
Application number	US-201213711138-A
Country	US
Kind code	B2
Filing date	Dec 11, 2012
Priority date	Dec 12, 2011
Publication date	Feb 16, 2016
Grant date	Feb 16, 2016

Abstract

An exhaust system 20 for an internal combustion engine comprises a) a first catalysed substrate monolith 12 comprising a first washcoat coating disposed in a first washcoat zone 16 of the substrate monolith and a second washcoat coating disposed in a second washcoat zone 18 of the substrate monolith, wherein the first washcoat coating comprises a catalyst composition comprising at least one platinum group metal (PGM) and at least one support material, wherein at least one PGM in the first washcoat coating is liable to volatilise when the first washcoat coating is exposed to relatively extreme conditions including relatively high temperatures, wherein the second washcoat coating comprises at least one material supporting copper for trapping volatilised PGM and wherein the second washcoat coating is oriented to contact exhaust gas that has contacted the first washcoat; and b) a second catalysed substrate monolith 14 comprising a catalyst for selectively catalysing the reduction of oxides of nitrogen to dinitrogen with a nitrogenous reductant disposed downstream from the first catalysed substrate monolith.

First claim

The invention claimed is:

1. An exhaust system for an internal combustion engine, which system comprising:
a) a first catalysed substrate monolith comprising a first washcoat coating disposed in a first washcoat zone of the substrate monolith, wherein the first washcoat coating comprises a catalyst composition comprising at least one platinum group metal (PGM) and at least one support material, wherein at least one platinum group metal (PGM) in the first washcoat coating is liable to volatilise when the first washcoat coating is exposed to a temperature of >700° C.; and
a second washcoat coating disposed in a second washcoat zone of the substrate monolith, wherein the second washcoat coating comprises at least one support material supporting copper for trapping volatilised platinum group metal (PGM), wherein the at least one support material supporting copper is a molecular sieve, wherein the molecular sieve is an aluminosilicate zeolite, and wherein the second washcoat coating is oriented to contact exhaust gas that has contacted the first washcoat; and

b) a second catalysed substrate monolith comprising a catalyst for selectively catalysing the reduction of oxides of nitrogen to dinitrogen with a nitrogenous reductant disposed downstream from the first catalysed substrate monolith.

2. An exhaust system according to claim 1 , comprising an injector for injecting a nitrogenous reductant into exhaust gas between the first catalysed substrate monolith and the second catalysed substrate monolith.

3. An exhaust system according to claim 1 , wherein the at least one PGM in the first washcoat coating comprises platinum.

4. An exhaust system according to claim 1 , wherein the at least one platinum group metal (PGM) in the first washcoat coating comprises both platinum and palladium.

5. An exhaust system according to claim 4 , wherein a weight ratio of Pt:Pd is ≦2.

6. An exhaust system according to claim 1 , wherein the at least one support material of the first washcoat coating is at least one metal oxide, a molecular sieve or a mixture of any two or more thereof.

7. An exhaust system according to claim 6 , wherein the at least one metal oxide support is selected from the group consisting of alumina, amorphous silica-alumina, zirconia, ceria, titania, a ceria-zirconia mixed oxide, stabilised alumina, stabilised zirconia, a stabilised ceria-zirconia mixed oxide and a mixture of any two or more thereof.

8. An exhaust system according to claim 6 , wherein the molecular sieve is an aluminosilicate zeolite.

9. An exhaust system according to claim 1 , wherein the first substrate monolith is a flow-through substrate monolith.

10. An exhaust system according to claim 1 , wherein the first substrate monolith is a filtering substrate monolith having inlet surfaces and outlet surfaces, wherein the inlet surfaces are separated from the outlet surfaces by a porous structure and wherein the first washcoat coating of the first zone is applied to the inlet surfaces and the second washcoat coating of the second zone is applied to the outlet surfaces.

11. An exhaust system according to claim 10 , wherein the filtering substrate monolith is a wall-flow filter, wherein inlet channels of the wall-flow filter comprise the first zone and wherein outlet channels of the wall-flow filter comprise the second zone.

12. An exhaust system according to claim 1 , wherein the second substrate monolith is a flow-through substrate monolith.

13. An exhaust system according to claim 1 , wherein the second substrate monolith is a filtering substrate monolith having inlet surfaces and outlet surfaces, wherein the inlet surfaces are separated from the outlet surfaces by a porous structure.

14. An exhaust system according to claim 13 , wherein the filtering substrate monolith is a wall-flow filter.

15. An exhaust system according to claim 1 , wherein the first washcoat comprises an oxidation catalyst or a NO x adsorber catalyst.

16. An exhaust system according to claim 1 , comprising a third substrate monolith, wherein the third substrate monolith is a filtering substrate monolith, which third substrate monolith is disposed downstream of the second catalysed substrate monolith.

17. An exhaust system of claim 16 , wherein the third substrate monolith comprises an oxidation catalyst.

18. An internal combustion engine for a vehicle comprising an exhaust system according to claim 1 .

19. An exhaust system according to claim 1 , wherein the molecular sieve is a medium pore zeolite having a maximum ring size of eight tetrahedral atoms or a large pore zeolite having a maximum of ring size of ten tetrahedral atoms.

20. An exhaust system according to claim 1 , wherein the molecular sieve is a zeolite selected from faujasite, clinoptilolite, mordenite, silicalite, ferrierite, zeolite X, zeolite Y, ultrastable zeolite Y, ZSM-5 zeolite, ZSM-12 zeolite, SSZ-3 zeolite, SAPO-5 zeolite, offretite and a beta zeolite.

21. An exhaust system according to claim 1 , wherein the molecular sieve is a zeolite having a silica/alumina molar ratio of from at least about 25/1.

22. An exhaust system according to claim 1 , wherein the second washcoat coating comprises copper in a total amount of from 10 to 350 g ft −3 .

23. An exhaust system for an internal combustion engine, which system comprising:
a) a first catalysed substrate monolith comprising a first washcoat coating disposed in a first washcoat zone of the substrate monolith, wherein the first washcoat coating comprises a catalyst composition comprising at least one platinum group metal (PGM) and at least one support material, wherein at least one platinum group metal (PGM) in the first washcoat coating is liable to volatilise when the first washcoat coating is exposed to a temperature of >700° C.; and
a second washcoat coating disposed in a second washcoat zone of the substrate monolith, wherein the second washcoat coating comprises at least one support material supporting copper for trapping volatilised platinum group metal (PGM), wherein the at least one support material supporting copper is a molecular sieve, wherein the molecular sieve is a medium pore zeolite having a maximum ring size of eight tetrahedral atoms or a large pore zeolite having a maximum of ring size of ten tetrahedral atoms, and wherein the second washcoat coating is oriented to contact exhaust gas that has contacted the first washcoat; and

b) a second catalysed substrate monolith comprising a catalyst for selectively catalysing the reduction of oxides of nitrogen to dinitrogen with a nitrogenous reductant disposed downstream from the first catalysed substrate monolith.

24. An exhaust system according to claim 23 , comprising an injector for injecting a nitrogenous reductant into exhaust gas between the first catalysed substrate monolith and the second catalysed substrate monolith.

25. An exhaust system according to claim 24 , wherein the at least one PGM in the first washcoat coating comprises platinum.

26. An exhaust system according to claim 24 , wherein the at least one platinum group metal (PGM) in the first washcoat coating comprises both platinum and palladium.

27. An exhaust system according to claim 26 , wherein a weight ratio of Pt:Pd is ≦2.

28. An exhaust system according to claim 24 , wherein the at least one support material of the first washcoat coating is at least one metal oxide, a molecular s

Assignees

• Johnson Matthey Plc

Inventors

• Blakeman Philip Gerald
• Brown Gavin Michael
• Chiffey Andrew Francis
• Gast Jane
• Phillips Paul Richard
• Rajaram Raj Rao
• Spreitzer Glen
• Walker Andrew Peter

Classifications

• Y02A50/20

  Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters · CPC title

• B01D2255/20761

  Copper · CPC title

• B01D2255/1023

  Palladium · CPC title

• B01D2255/1021

  Platinum · CPC title

• B01D2258/012

  Diesel engines and lean burn gasoline engines · CPC title