Zeolite Catalyst With Improved NOx Reduction in SCR

• US 20100172814A1
• Filed: 01/13/2010
• Published: 07/08/2010
• Est. Priority Date: 12/14/2005
• Status: Active Grant

• Current Assignee: BASF Corporation (BASF SE)
• Original Assignee: BASF Catalysts LLC (BASF SE)
• Inventors: Roth, Stan, Moini, Ahmad, Bull, Ivor, Koermer, Gerald Stephen, Jaglowski, William Michael, Patchett, Joseph Allan
• Granted Patent: US 7,968,068 B2
• Time in Patent Office: Days
• US Class Current: 423/239.200
• CPC Class Codes: B01D 2251/2062 Ammonia
• CPC Class Codes: B01D 2255/20761 Copper
• CPC Class Codes: B01D 2255/50 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: B01J 2229/16 to increase the Si/Al ratio; Dealumination
• CPC Class Codes: B01J 2229/18 to introduce other elements into or onto the molecular sieve itself
• CPC Class Codes: B01J 2229/186 not in framework positions
• CPC Class Codes: B01J 2229/24 to stabilize the molecular sieve structure
• CPC Class Codes: B01J 2229/36 Steaming
• CPC Class Codes: B01J 2229/37 Acid treatment
• CPC Class Codes: B01J 2229/42 Addition of matrix or binder particles
• CPC Class Codes: B01J 29/061 containing metallic elements added to the zeolite
• CPC Class Codes: B01J 29/072 Iron group metals or copper
• CPC Class Codes: B01J 29/076 containing arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
• CPC Class Codes: B01J 29/084 Y-type faujasite
• CPC Class Codes: B01J 29/088 Y-type faujasite
• CPC Class Codes: B01J 29/146 Y-type faujasite
• CPC Class Codes: B01J 29/166 Y-type faujasite
• CPC Class Codes: B01J 29/40 of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively
• CPC Class Codes: B01J 29/46 Iron group metals or copper
• CPC Class Codes: B01J 29/7007 : Zeolite Beta
• CPC Class Codes: B01J 29/7015 : CHA-type, e.g. Chabazite, LZ-218
• 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 29/80 : Mixtures of different zeolites
• CPC Class Codes: B01J 29/85 : Silicoaluminophosphates [SAPO compounds]
• CPC Class Codes: B01J 35/023 : Catalysts characterised by dimensions, e.g. grain size
• CPC Class Codes: B01J 35/04 : Foraminous structures, sieves, grids, honeycombs
• CPC Class Codes: B01J 35/1033 : Pore volume
• CPC Class Codes: B01J 35/1052 : Pore diameter
• CPC Class Codes: B01J 35/1095 : polymodal
• 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 35/63 : Pore volume
• CPC Class Codes: B01J 35/64 : Pore diameter
• CPC Class Codes: B01J 35/695 : polymodal
• CPC Class Codes: B01J 37/0018 : Addition of a binding agent or of material, later completely removed among others as result of heat treatment, leaching or washing,(e.g. forming of pores; protective layer, desintegrating by heat)
• CPC Class Codes: B01J 37/0246 : Coatings comprising a zeolite
• CPC Class Codes: Y02C 20/10 : of nitrous oxide (N2O)

Abstract

The present invention is directed to a novel metal-promoted zeolite catalyst, a method of producing the catalyst and a method of sing the catalyst for the selective catalytic reduction of NO_x with improved hydrothermal durability. The novel metal-promoted zeolite is formed from a low sodium zeolite and is hydrothermally treated after metal ion-exchange.

Claims

1. A method of reducing NOx in an exhaust gas or flue gas stream with ammonia and oxygen by selective catalytic reduction, the method comprising contacting said exhaust gas or flue gas stream with a hydrothermally stable zeolite catalyst comprising a metal-promoted, low sodium zeolite, wherein said metal-promoted, low sodium zeolite has been treated to form extra-framework aluminum and remove a major portion of said extra-framework aluminum from zeolite pores.

2. The method of claim 1, wherein said metal-promoted, low sodium zeolite has a sodium content of less than 3 weight percent as Na₂O following metal ion-exchange and is hydrothermally treated after metal ion-exchange to form the extra-framework aluminum and remove the major portion of the extra-framework aluminum from the zeolite pores.

3. The method of claim 1, wherein the method exhibits improved NOx reduction activity in selective catalytic reduction as compared to a method using a metal-promoted, low sodium zeolite catalyst not treated to form extra-framework aluminum and remove a major portion of said extra-framework aluminum from zeolite pores.

4. The method of claim 3, wherein the improved NOx reduction activity in selective catalytic reduction is at a temperature at or below 350°

C.

5. The method of claim 1, further comprising converting greater than 50% of the NOx gases in the exhaust gas or flue gas stream at temperatures at or below about 250°

C.

6. The method of claim 1, further comprising converting greater than 80% of the NOx gases in the exhaust gas or flue gas stream at temperatures at or below about 300°

C.

7. The method of claim 1, wherein less than 65 wt. % of the total aluminum resides in the zeolite pores.

8. The method of claim 1, wherein said metal-promoted, low sodium zeolite is zeolite Y and said metal is copper.

9. The method of claim 1, wherein said metal-promoted, low sodium zeolite contains mesopores having a diameter in the range of 2 to 50 nm and said mesopores have a pore volume of at least 0.07 cm³/g.

10. The method of claim 1, wherein said metal-promoted, low sodium zeolite contains a metal loading at the external surface of the zeolite from about 1 wt. % to about 10.0 wt. %, based on the weight of the metal-promoted, low sodium zeolite.

11. The method of claim 1, wherein said hydrothermally stable zeolite catalyst is coated onto a substrate.

12. The method of claim 1, wherein a major portion of the extra-framework aluminum has migrated to the external surface of said metal-promoted, low sodium zeolite.

13. The method of claim 1, wherein said metal-promoted, low sodium zeolite is treated by acid dealumination, steam dealumination or extraction of extra-framework aluminum with a complexing agent to remove the major portion of said extra-framework aluminum from the zeolite pores.

14. The method of claim 1, wherein said metal-promoted, low sodium zeolite is selected from the group consisting of zeolite Y, faujasites, ultra-stable Y, ZSM-3, ZSM-20, CSZ-1, ECR-30, LZ-210, zeolite L, ferrierite, MCM-22 and offretite.

15. The method of claim 1, wherein said metal-promoted, low sodium zeolite is promoted with a metal selected from the group consisting of metal ions of vanadium, chromium, manganese, iron, cobalt, nickel, copper and cerium.

16. The method of claim 1, wherein said metal-promoted, low sodium zeolite has a sodium content of less than 3.0 wt. % as Na₂O following metal ion-exchange.

17. The method of claim 16, wherein the sodium content is less than 2.4 wt. % as Na₂O following metal ion-exchange.

18. The method of claim 17, wherein the sodium content is less than 1.0 wt. % as Na₂O following metal ion-exchange.

19. The method of claim 18, wherein the sodium content is less than 0.4 wt. % as Na₂O following metal ion-exchange.