PGM catalyst for treating exhaust gas

• US 9,751,080 B2
• Filed: 04/14/2015
• Issued: 09/05/2017
• Est. Priority Date: 06/05/2011
• Status: Active Grant

• Current Assignee: Johnson Matthey PLC
• Original Assignee: Johnson Matthey PLC
• Inventors: Fedeyko, Joseph Michael, Chen, Hai-Ying, Andersen, Paul Joseph
• Primary Examiner(s): VANOY, TIMOTHY C
• Application Number:
  US14/685,793
• Publication Number:
  US 20150217282A1
• Time in Patent Office: 875 Days
• CPC Class Codes: B01D 2255/1021 Platinum
• CPC Class Codes: B01D 2255/50 Zeolites
• CPC Class Codes: B01D 2255/9155 Wall flow filters
• CPC Class Codes: B01D 2255/9205 Porosity
• CPC Class Codes: B01D 53/56 Nitrogen oxides B01D53/60 takes precedence
• CPC Class Codes: B01D 53/58 Ammonia
• CPC Class Codes: B01D 53/62 Carbon oxides
• 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 53/9431 Processes characterised by a specific device
• 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 53/9477 with catalysts positioned on separate bricks, e.g. exhaust systems
• CPC Class Codes: B01J 2229/183 in framework positions
• 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 29/068 Noble metals
• CPC Class Codes: B01J 29/7015 CHA-type, e.g. Chabazite, LZ-218
• CPC Class Codes: B01J 29/74 Noble metals
• CPC Class Codes: B01J 29/743 CHA-type, e.g. Chabazite, LZ-218
• CPC Class Codes: B01J 29/78 containing arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
• CPC Class Codes: B01J 29/783 : CHA-type, e.g. Chabazite, LZ-218
• CPC Class Codes: B01J 29/85 : Silicoaluminophosphates [SAPO compounds]
• CPC Class Codes: B01J 29/87 : Gallosilicates; Aluminogallosilicates; Galloborosilicates B01J29/005 takes precedence
• CPC Class Codes: B01J 35/19 : Catalysts containing parts with different compositions
• CPC Class Codes: B01J 35/40 : characterised by dimensions, e.g. grain size in a colloidal state B01J35/23; crystallite size B01J35/77
• 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 35/58 : Fabrics or filaments
• CPC Class Codes: B01J 37/0246 : Coatings comprising a zeolite
• CPC Class Codes: Y02C 20/10 : of nitrous oxide (N2O)
• CPC Class Codes: Y02T 10/12 : Improving ICE efficiencies

Abstract

Provided are catalysts comprising a small pore molecular sieve embedded with PGM and methods for treating lean burn exhaust gas using the same.

Claims

1. A catalyst article comprising:

a. a substrate; and

b. a PGM catalyst disposed on the substrate in a discrete outlet zone, said catalyst comprising

i. aluminosilicate molecular sieve crystals having surfaces and porous networks, a mean crystalline size of about 0.01 to about 10 microns, a framework selected from CHA, RHO, LEV, AEI, ANA, LTA, DDR, PAU, UEI, and SOD, a silica-to-alumina ratio of about 8 to about 150, and an alkali content of no more than about 5 weight percent based on the total weight of the molecular sieve crystals; and

ii. 0.1 to 5 weight percent palladium based on the total weight of the molecular sieve crystals, wherein a majority amount of said palladium is disposed in said porous networks relative to said surfaces, and

c. an SCR catalyst disposed on the substrate in a discrete inlet zone, said SCR catalyst having either a molecular sieve promoted with iron and/or copper or vanadium on an alumina support.

2. The catalyst article of claim 1, wherein said substrate is a honeycomb monolith.

3. The catalyst article of claim 1, wherein said substrate is a wall-flow filter.

4. The catalyst article of claim 1, wherein said substrate is a flow-through monolith.

5. The catalyst article of claim 1, wherein the PGM catalyst has a CHA framework.

6. The catalyst article of claim 1, wherein the PGM catalyst has an AEI framework.

7. The catalyst article of claim 1, wherein the PGM catalyst has an LTA framework.

8. The catalyst article of claim 1, wherein the SCR catalyst has a CHA framework.

9. The catalyst article of claim 1, wherein the SCR catalyst has vanadium on an alumina support.

10. The catalyst article of claim 1, wherein the inlet and outlet zones are adjacent to each other.

11. The catalyst article of claim 1, wherein the inlet zone is on the inlet side of the flow-through substrate and outlet zone is on the outlet side of the flow-through substrate.

12. A method for treating emissions comprising:

a. contacting a lean burn exhaust stream containing NO_x and ammonia with a catalyst article according to claim 1 at a temperature of about 150°

C. to about 650°

C.; and

b. reducing at least a portion of said NO_x to N₂ and H₂O at a temperature of about 150°

C. to about 250°

C. and oxidizing at least a portion of said ammonia at a temperature of about 300°

C. to about 650°

C.

13. The method of claim 12, wherein said reducing has a selectivity for N₂ of at least about 90% at a temperature of about 150°

C. to about 250°

C.

14. The method of claim 12, wherein said reducing has a N₂O selectivity of less than about 10% at a temperature of about 150°

C. to about 650°

C.

15. The method of claim 12, wherein said oxidizing has a conversion of at least about 95% at a temperature of about 350°

C. to about 650°

C.

16. A method for treating emissions comprising:

a. contacting a lean burn exhaust stream containing CO and NO with a catalyst article according to claim 1;

b. oxidizing at least one of said CO and NO to form CO₂ and NO₂, respectively, wherein said oxidizing NO to NO₂ results in an exhaust gas stream having an NO;

NO₂ ratio of from about 4;

1 to about 1;

3 by volume.

17. A system for treating exhaust gas comprising:

a. a reductant source;

b. an upstream SCR catalyst; and

c. a downstream PGM catalyst comprising

i. aluminosilicate molecular sieve crystals having surfaces and porous networks, a mean crystalline size of about 0.01 to about 10 microns, a framework selected from CHA, RHO, LEV, AEI, ANA, LTA, DDR, PAU, UEI, and SOD, a silica-to-alumina ratio of about 8 to about 150, and an alkali content of no more than about 5 weight percent based on the total weight of the molecular sieve crystals; and

d. 0.1 to 5 weight percent palladium based on the total weight of the molecular sieve crystals, wherein a majority amount of said palladium is disposed in said porous networks relative to said surfaces;

wherein said SCR catalyst and said PGM catalyst are disposed on separate substrates;

said reductant source, upstream SCR catalyst, and downstream catalyst are in fluid communication with each other and are arranged so that an exhaust gas stream flowing through the system contacts the reductant source prior to the upstream SCR catalyst and contacts the SCR catalyst prior to the downstream SCR catalyst.

18. The system of claim 17, wherein said reductant source is a NO_x absorber catalyst.

19. The system of claim 17, wherein said upstream SCR catalyst has a NO_x conversion efficiency greater than that of said downstream catalyst at a temperature of about 350°

C. to about 650°

C. and said downstream catalyst has a NO_x conversion efficiency greater than that of said upstream SCR catalyst at a temperature of about 150°

C. to about 250°

C.

20. The system of claim 17, wherein said downstream catalyst selectively reduces NOx when contacting said exhaust gas stream at a temperature of about 150°

C. to about 250°

C. and oxidizes the nitrogenous reductant when contacting said exhaust gas stream at a temperature of about 350°

C. to about 650°

C.