Catalyzed SCR Filter and Emission Treatment System

• US 20080132405A1
• Filed: 02/08/2008
• Published: 06/05/2008
• Est. Priority Date: 08/05/2003
• Status: Active Grant

• Current Assignee: BASF Corporation (BASF SE)
• Original Assignee: BASF Corporation (BASF SE)
• Inventors: Przybylski, Elizabeth Alina, Patchett, Joseph Allan, Dettling, Joseph Charles
• Granted Patent: US 7,902,107 B2
• Time in Patent Office: Days
• US Class Current: 502/74
• CPC Class Codes: B01D 19/0005 with one or more auxiliary substances
• CPC Class Codes: B01D 19/0036 Flash degasification the other groups take precedence
• CPC Class Codes: B01D 2251/2062 Ammonia
• CPC Class Codes: B01D 2251/2067 Urea
• CPC Class Codes: B01D 2255/102 Platinum group metals
• CPC Class Codes: B01D 2255/20715 Zirconium
• CPC Class Codes: B01D 2255/20738 Iron
• CPC Class Codes: B01D 2255/20761 Copper
• CPC Class Codes: B01D 2255/50 Zeolites
• CPC Class Codes: B01D 2255/502 Beta zeolites
• CPC Class Codes: B01D 2255/9155 Wall flow filters
• CPC Class Codes: B01D 2255/9202 Linear dimensions
• CPC Class Codes: B01D 2255/9205 Porosity
• CPC Class Codes: B01D 2257/404 Nitrogen oxides other than dinitrogen oxide
• CPC Class Codes: B01D 2258/012 Diesel engines and lean burn gasoline engines
• CPC Class Codes: B01D 5/0054 General arrangements, e.g. flow sheets
• CPC Class Codes: B01D 5/009 Collecting, removing and/or treatment of the condensate
• CPC Class Codes: B01D 53/9413 Processes characterised by a specific catalyst
• 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 53/945 : characterised by a specific catalyst
• CPC Class Codes: B01D 53/9477 : with catalysts positioned on separate bricks, e.g. exhaust systems
• CPC Class Codes: B01J 29/76 : Iron group metals or copper
• CPC Class Codes: B01J 29/7615 : Zeolite Beta
• 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 35/657 : larger than 1000 nm
• CPC Class Codes: B01J 37/0236 : Drying, e.g. preparing a suspension, adding a soluble salt and drying
• CPC Class Codes: B01J 37/024 : Multiple impregnation or coating
• CPC Class Codes: B01J 37/0246 : Coatings comprising a zeolite
• CPC Class Codes: B01J 37/08 : Heat treatment B01J37/0009, B01J37/0018 take precedence
• CPC Class Codes: F01N 13/009 : having two or more separate purifying devices arranged in series
• CPC Class Codes: F01N 2330/06 : Ceramic, e.g. monoliths
• CPC Class Codes: F01N 2330/30 : Honeycomb supports characterised by their structural details
• CPC Class Codes: F01N 2370/04 : Zeolitic material
• CPC Class Codes: F01N 2510/063 : zeolites
• CPC Class Codes: F01N 2610/02 : the substance being ammonia or urea
• CPC Class Codes: F01N 2610/08 : with prior mixing of the substances with a gas, e.g. air
• CPC Class Codes: F01N 3/0231 : using special exhaust apparatus upstream of the filter for producing nitrogen dioxide, e.g. for continuous filter regeneration systems [CRT]
• CPC Class Codes: F01N 3/10 : by thermal or catalytic conversion of noxious components of exhaust by using other chemical processes, chemical aspects of catalytic conversion, e.g. using specified catalysts, B01D53/34
• CPC Class Codes: F01N 3/106 : Auxiliary oxidation catalysts
• CPC Class Codes: F01N 3/2066 : Selective catalytic reduction [SCR]
• CPC Class Codes: F01N 3/2828 : Ceramic multi-channel monoliths, e.g. honeycombs
• CPC Class Codes: F01N 3/2892 : Exhaust flow directors or the like, e.g. upstream of catalytic device
• CPC Class Codes: Y02T 10/12 : Improving ICE efficiencies
• CPC Class Codes: Y10S 55/10 : Residue burned
• CPC Class Codes: Y10S 55/30 : Exhaust treatment
• CPC Class Codes: Y10T 29/49345 : Catalytic device making

Abstract

Provided is an emission treatment system and method for simultaneously remediating the nitrogen oxides (NOx), particulate matter, and gaseous hydrocarbons present in diesel engine exhaust streams. The emission treatment system has an oxidation catalyst upstream of a soot filter coated with a material effective in the Selective Catalytic Reduction (SCR) of NOx by a reductant, e.g., ammonia. Also provided is a method for disposing an SCR catalyst composition on a wall flow monolith that provides adequate catalyst loading, but does not result in unsuitable back pressures in the exhaust.

Claims

1. A catalyst article comprising a wall flow monolith having a plurality of longitudinally extending passages formed by longitudinally extending walls bounding and defining said passages, wherein the passages comprise inlet passages having an open inlet end and a closed outlet end, and outlet passages having a closed inlet end and an open outlet end, and the wall flow monolith contains an SCR catalyst composition at a loading that achieves suitable NOx conversion efficiency but does not cause an unacceptable increase in backpressure when used in a diesel exhaust system.

2. The catalyst article of claim 1, wherein the SCR catalyst composition is in the form of a washcoat on the walls of the monolith.

3. The catalyst article or claim 2, wherein the SCR catalyst composition permeates the walls of the monolith at a concentration of at least 1.3 g/in³.

4. The catalyst article of claim 3, wherein there is from 1.6 to 2.4 g/in³ of SCR catalyst composition disposed on the wall flow monolith.

5. The catalyst article of claim 1, wherein the SCR catalyst composition is effective to catalyze the reduction of NOx at a temperature below about 600°

C. and able to aid in regeneration of the filter by lowering the temperature at which soot captured by the filter is combusted.

6. The catalyst article of claim 1, wherein the SCR catalyst composition has a thermal resistance to degradation at temperatures greater than 650°

C.

7. The catalyst article of claim 6, wherein the SCR catalyst composition is effective to resist degradation upon exposure to sulfur components.

8. The catalyst article of claim 1, wherein the SCR catalyst composition promotes the oxidation of excess NH₃ with O₂.

9. The catalyst article of claim 1, wherein the SCR catalyst composition comprises a zeolite and base metal component selected from one or more of a copper and iron component.

10. The catalyst article of claim 9, wherein the base metal component is a copper component.

11. The catalyst article of claim 10, wherein the zeolite of the SCR catalyst composition has a silica to alumina ratio of at least about 10.

12. The article of claim 11, wherein the zeolite of the SCR catalyst composition is selected from beta zeolite, USY and ZSM-20.

13. The catalyst article of claim 11, wherein the zeolite of the SCR catalyst composition is a beta zeolite.

14. The catalyst article of claim 9, wherein the zeolite of the SCR catalyst composition has pores with a pore diameter of at least about 7 Angstroms and are connected in three dimensions.

15. The catalyst article of claim 9, wherein the SCR catalyst composition contains one or both of an iron and a copper promoter present in an amount of from about 0.1 to 30 percent by weight of the total weight of promoter plus zeolite.

16. The catalyst article of claim 9, wherein the SCR catalyst composition contains one or both of an iron and a copper promoter present in an amount of from about 1 to 5 percent by weight of the total weight of promoter plus zeolite.

17. The catalyst article of claim 3, wherein the wall flow monolith has a wall porosity of at least 50% with an average pore size of at least 5 microns.

18. The catalyst article of claim 3, wherein the wall flow monolith has a wall porosity of from 50 to 75% with an average pore size of from 5 to 30 microns.

19. A catalyst article comprising a wall flow monolith having a plurality of longitudinally extending passages formed by longitudinally extending walls bounding and defining said passages, wherein the passages comprise inlet passages having an open inlet end and a closed outlet end, and outlet passages having a closed inlet end and an open outlet end, wherein the wall flow monolith comprises an SCR catalyst composition that permeates the walls at a concentration of at least 1.3 g/in³;

wherein the wall flow monolith has a wall porosity of at least 50% with an average pore size of at least 5 microns.

20. The catalyst article of claim 19, wherein there is from 1.6 to 2.4 g/in³ of SCR catalyst composition disposed on the wall flow monolith.