SUBSTRATE MONOLITH COMPRISING SCR CATALYST

• US 20130149207A1
• Filed: 12/11/2012
• Published: 06/13/2013
• Est. Priority Date: 12/12/2011
• Status: Active Grant

• Current Assignee: Johnson Matthey PLC
• Original Assignee: Johnson Matthey PLC
• Inventors: CHIFFEY, ANDREW FRANCIS, PHILLIPS, PAUL RICHARD, RAJARAM, RAJ RAO, WALKER, ANDREW PETER, CASTAGNOLA, MARIO JAIME
• Granted Patent: US 9,333,461 B2
• Time in Patent Office: Days
• US Class Current: 422/177
• CPC Class Codes: B01D 2255/1021 Platinum
• CPC Class Codes: B01D 2255/1023 Palladium
• CPC Class Codes: B01D 2255/104 Silver
• CPC Class Codes: B01D 2255/106 Gold
• CPC Class Codes: B01D 2255/20738 Iron
• CPC Class Codes: B01D 2255/50 Zeolites
• CPC Class Codes: B01D 2255/502 Beta zeolites
• 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 53/9472 in different zones
• CPC Class Codes: B01D 53/9481 Catalyst preceded by an adsorption device without catalytic function for temporary storage of contaminants, e.g. during cold start
• CPC Class Codes: B01J 21/04 Alumina
• CPC Class Codes: B01J 2229/186 not in framework positions
• CPC Class Codes: B01J 2229/42 Addition of matrix or binder particles
• CPC Class Codes: B01J 23/40 of the platinum group metals
• CPC Class Codes: B01J 23/42 Platinum
• CPC Class Codes: B01J 23/44 Palladium
• CPC Class Codes: B01J 23/50 Silver
• CPC Class Codes: B01J 23/52 Gold
• CPC Class Codes: B01J 23/63 with rare earths or actinides
• CPC Class Codes: B01J 23/72 Copper
• CPC Class Codes: B01J 29/7415 : Zeolite Beta
• CPC Class Codes: B01J 29/7615 : Zeolite Beta
• 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 37/0036 : Grinding
• CPC Class Codes: B01J 37/0215 : Coating
• CPC Class Codes: B01J 37/0246 : Coatings comprising a zeolite
• CPC Class Codes: B01J 37/038 : to form slurries or suspensions, e.g. a washcoat
• CPC Class Codes: F01N 2510/0682 : having a discontinuous, uneven or partially overlapping coating of catalytic material, e.g. higher amount of material upstream than downstream or vice versa
• 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: Y02A 50/20 : Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
• CPC Class Codes: Y02T 10/12 : Improving ICE efficiencies

Abstract

A substrate monolith 6 having a length L and comprising a first zone 11 of substantially uniform length defined at one end by a first end of the substrate monolith, which first zone comprising a selective catalytic reduction (SCR) catalyst for reducing oxides of nitrogen with a nitrogenous reductant in exhaust gas emitted from an internal combustion engine and a second zone 8 of substantially uniform length less than L defined at one end by a second end of the substrate monolith, which second zone comprising (a) at least one particulate metal oxide or a mixture of any two or more thereof for trapping gas phase platinum group metal (PGM), which at least one particulate metal oxide does not act as a support for any other catalytic component; or (b) a component capable of trapping and/or alloying with gas phase PGM.

Claims

1. A substrate monolith having a length L and comprising a first zone of substantially uniform length defined at one end by a first end of the substrate monolith, which first zone comprising a selective catalytic reduction (SCR) catalyst for reducing oxides of nitrogen with a nitrogenous reductant in exhaust gas emitted from an internal combustion engine and a second zone of substantially uniform length less than L defined at one end by a second end of the substrate monolith, which second zone comprising (a) at least one particulate metal oxide or a mixture of any two or more thereof for trapping gas phase platinum group metal (PGM), which at least one particulate metal oxide does not act as a support for any other catalytic component;

or (b) a component capable of trapping and/or alloying with gas phase PGM.

2. A substrate monolith according to claim 1, wherein the at least one particulate metal oxide of (a) is selected from the group consisting of optionally stabilised alumina, amorphous silica-alumina, optionally stabilised zirconia, ceria, titania, an optionally stabilised ceria-zirconia mixed oxide and mixtures of any two or more thereof.

3. A substrate monolith according to claim 1, wherein the component capable of trapping and/or alloying with gas phase PGM comprises a metal selected from the group consisting of gold, palladium and silver.

4. A substrate monolith according to claim 3, wherein the component capable of trapping and/or alloying with gas phase PGM comprises a mixture or an alloy of palladium and gold.

5. A substrate monolith according to claim 1, wherein the first zone extends over the entire length L and wherein the second zone overlies the first zone.

6. A substrate monolith according to claim 5, wherein the SCR catalyst in the first zone is present as a coating on the substrate monolith.

7. A substrate monolith according to claim 5, wherein the component capable of trapping and/or alloying with gas phase PGM is supported by the SCR catalyst per se.

8. A substrate monolith according to claim 5, wherein the component capable of trapping and/or alloying with gas phase PGM comprises at least one metal oxide on which the component capable of trapping and alloying with gas phase PGM is supported.

9. A substrate monolith according to claim 1, wherein the SCR catalyst in the first zone is present as a coating on the substrate monolith of substantially uniform length less than L, wherein the component capable of trapping and/or alloying with gas phase PGM comprises at least one metal oxide on which the component capable of trapping and alloying with gas phase PGM is supported and wherein there is substantially no overlap between the first zone and the second zone.

10. A substrate monolith according to claim 1 which 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.

11. A substrate monolith according to claim 10, wherein the filtering substrate monolith is a wall-flow filter, and wherein the SCR catalyst is disposed in open channels at the first end of the wall-flow filter and the second zone is disposed in open channels at the second end thereof, wherein the porous structure defines a transition between the first washcoat zone and the second washcoat zone.

12. An exhaust system for a vehicular lean-burn internal combustion engine, which system comprising:

a catalysed substrate monolith which comprises a catalyst comprising at least one PGM; and

a substrate monolith having a length L and comprising a first zone of substantially uniform length defined at one end by a first end of the substrate monolith, which first zone comprising a selective catalytic reduction (SCR) catalyst for reducing oxides of nitrogen with a nitrogenous reductant in exhaust gas emitted from an internal combustion engine and a second zone of substantially uniform length less than L defined at one end by a second end of the substrate monolith, which second zone comprising (a) at least one particulate metal oxide or a mixture of any two or more thereof for trapping gas phase platinum group metal (PGM), which at least one particulate metal oxide does not act as a support for any other catalytic component;

or (b) a component capable of trapping and/or alloying with gas phase PGM; and

wherein the at least one PGM is disposed upstream of the substrate monolith, and the second end of the substrate monolith is oriented to an upstream side.

13. An exhaust system according to claim 12, wherein the catalyst comprising PGM is a diesel oxidation catalyst or a NO_x absorber catalyst.

14. An exhaust system according to claim 12, wherein the substrate monolith which comprises a catalyst comprising PGM is a filtering substrate monolith.

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

16. An exhaust system according to claim 12 comprising means for injecting ammonia or a precursor thereof between the catalysed substrate monolith and the substrate monolith comprising the SCR catalyst.

17. A lean-burn internal combustion engine comprising an exhaust system according to claim 12.

18. A method of reducing or preventing platinum group metal from poisoning a selective catalytic reduction (SCR) catalyst for reducing oxides of nitrogen with a nitrogenous reductant in exhaust gas emitted from an internal combustion engine in an exhaust system of a lean-burn internal combustion engine, which platinum group metal (PGM) is present on a catalysed substrate monolith of an exhaust system of a lean-burn internal combustion engine and is liable to volatilise when in use and migrate to a surface of a substrate monolith comprising the SCR catalyst, which substrate monolith is disposed downstream of the catalysed substrate monolith, which substrate monolith having a length L and comprising a first zone of substantially uniform length defined at one end by a first end of the substrate monolith, which first zone comprising a selective catalytic reduction (SCR) catalyst for reducing oxides of nitrogen with a nitrogenous reductant in exhaust gas emitted from an internal combustion engine and a second zone of substantially uniform length less than L defined at one end by a second end of the substrate monolith, which second zone comprising (a) at least one particulate metal oxide or a mixture of any two or more thereof for trapping gas phase PGM, which at least one particulate metal oxide does not act as a support for any other catalytic component;

or (b) a component capable of trapping and alloying with gas phase PGM and wherein the second zone is oriented to contact exhaust gas exiting the catalysed substrate monolith before the first zone, which method comprising trapping and/or alloying PGM in the second zone.