Catalyzed SCR filter and emission treatment system

• US 7,229,597 B2
• Filed: 08/05/2003
• Issued: 06/12/2007
• Est. Priority Date: 08/05/2003
• Status: Active Grant

• Current Assignee: BASF Corporation (BASF SE)
• Original Assignee: BASF Catalysts LLC (BASF SE)
• Inventors: Patchett, Joseph Allan, Dettling, Joseph Charles, Przybylski, Elizabeth Alina
• Primary Examiner(s): Johnson; Edward M.
• Application Number:
  US10/634,659
• Publication Number:
  US 20050031514A1
• Time in Patent Office: 1,407 Days
• Field of Search: 422/168, 422/177, 422/180, 422/181, 423/239.1, 423/239.2, 502/74, 502/326, 502/331, 502/345
• US Class Current: 422/177
• 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. An emission treatment system for treatment of an exhaust stream comprising NOx and particulate matter, the emission treatment system comprising:

a) an oxidation catalyst;

b) an injector in fluid communication with and downstream of the oxidation catalyst, wherein the injector periodically meters ammonia or an ammonia precursor into the exhaust stream; and

c) a wall flow monolith in fluid communication with and downstream of the injector, wherein the wall flow monolith has 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.

2. The emission treatment system of claim 1, wherein the SCR catalyst composition that permeates the walls of the wall flow monolith so that the walls have a wall porosity of from 50 to 75% with an average pore size of from 5 to 30 microns.

3. The emission treatment system 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.

4. The emission treatment system of claim 3, wherein the base metal component is a copper component.

5. The emission treatment system of claim 4, wherein the zeolite of the SCR catalyst composition has a silica to alumina ratio of at least about 10.

6. The emission treatment system of claim 5, wherein the zeolite of the SCR catalyst composition is a beta zeolite.

7. The emission treatment system of claim 1, wherein there is from 1.6 to 2.4 g/in³ of SCR catalyst composition disposed on the wall flow monolith.

8. The emission treatment system of claim 1, wherein the oxidation catalyst comprises a platinum group metal component.

9. The emission treatment system of claim 8, wherein the oxidation catalyst further comprises a zeolite component.

10. The emission treatment system of claim 1, further comprising a diesel engine upstream of, and in fluid communication with the oxidation catalyst.

11. The emission treatment system of claim 1, wherein the oxidation catalyst is disposed on a honeycomb flow through monolith substrate or an open cell foam substrate.

12. The emission treatment system of claim 1, wherein the injector comprises an aqueous urea reservoir and a pump.

13. The emission treatment system of claim 1, wherein the injector comprises gaseous nitrogen based reagent.

14. The emission treatment system of claim 1, wherein the inlet passages of the wall flow monolith are coated with the SCR catalyst.

15. The emission treatment system of claim 14, wherein the inlet passages and the outlet passages are coated with the SCR catalyst.