Catalysts, Systems and Methods Utilizing Non-Zeolitic Metal-Containing Molecular Sieves Having the CHA Crystal Structure

• US 20090196812A1
• Filed: 01/29/2009
• Published: 08/06/2009
• Est. Priority Date: 01/31/2008
• Status: Abandoned Application

• Current Assignee: BASF Corporation (BASF SE)
• Original Assignee: BASF Catalysts LLC (BASF SE)
• Inventors: Unverricht, Signe, Koermer, Gerald S., Moini, Ahmad, Bull, Ivor
• Application Number:
  US12/361,980
• Publication Number:
  US 20090196812A1
• Time in Patent Office: Days
• US Class Current: 423/239.1
• CPC Class Codes: B01D 2251/2062 Ammonia
• CPC Class Codes: B01D 2251/2067 Urea
• CPC Class Codes: B01D 2255/1021 Platinum
• 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 2255/504 ZSM 5 zeolites
• CPC Class Codes: B01D 2255/915 Catalyst supported on particulate filters
• CPC Class Codes: B01D 2255/9207 Specific surface
• 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 53/945 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 2229/186 not in framework positions
• CPC Class Codes: B01J 29/005 Mixtures of molecular sieves comprising at least one molecular sieve which is not an aluminosilicate zeolite, e.g. from groups B01J29/03 - B01J29/049 or B01J29/82 - B01J29/89
• CPC Class Codes: B01J 29/85 Silicoaluminophosphates [SAPO compounds]
• CPC Class Codes: B01J 35/04 Foraminous structures, sieves, grids, honeycombs
• 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 35/615 100-500 m2/g
• CPC Class Codes: B01J 35/617 : 500-1000 m2/g
• CPC Class Codes: B01J 37/0246 : Coatings comprising a zeolite
• 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 3/2066 : Selective catalytic reduction [SCR]
• CPC Class Codes: Y02C 20/10 : of nitrous oxide (N2O)
• CPC Class Codes: Y02T 10/12 : Improving ICE efficiencies

Abstract

Catalysts comprising metal-loaded non-zeolitic molecular sieves having the CHA crystal structure, including Cu-SAPO-34, methods for preparing such catalysts, and systems and methods for treating exhaust gas incorporating such catalysts are disclosed. The catalysts can be used to remove nitrogen oxides from a gaseous medium across a broad temperature range and exhibit hydrothermal stability at high reaction temperatures.

Claims

1. A catalyst comprising:

a Cu-loaded non-zeolitic molecular sieve having the CHA crystal structure having a Cu loading so that the catalyst is effective to selectively reduce nitrogen oxides with ammonia in the presence of oxygen in an exhaust gas stream at 200°

C. when the catalyst has been deposited on a honeycomb substrate having a cell density of 400 cpsi at a loading between 2 and 2.5 g/in³ and tested at a space velocity of 80,000 hr<sup>−

1</sup> where the feed stream comprises a mixture of 10% O₂, 5% H₂O, 500 ppm NO and 500 ppm NH₃ to provide at least 80% NOx conversion.

2. The catalyst of claim 1, wherein the non-zeolitic molecular sieve comprises Cu-SAPO-34 and the catalyst is effective to provide at least about 85% NOx conversion in the exhaust gas stream at 200°

C.

3. The catalyst of claim 2, wherein the catalyst is effective to provide at least about 90% NOx conversion in the exhaust gas stream at 200°

C.

4. The catalyst of claim 1, wherein the Cu-SAPO-34 material, upon hydrothermal aging in 10% steam at 850°

C. and 6 hours, retains at least 85% on a percentage basis of the NOx conversion at 200°

C.

5. The catalyst of claim 2, wherein the Cu-SAPO-34 material, upon hydrothermal aging in 10% steam at 900°

C. and 1 hour, retains at least 90% of the NOx conversion on a percentage basis at 200°

C.

6. The catalyst of claim 3, wherein the Cu-SAPO-34 material, upon hydrothermal aging in 10% steam at 900°

C. and 1 hour, retains at least 95% of the NOx conversion on a percentage basis at 200°

C.

7. The catalyst of claim 2, wherein the catalyst is effective to reduce NOx so that that ratio of NOx to N₂O in the gas stream after passing through the catalyst is greater than 2.5

8. The catalyst of claim 2, wherein the catalyst is effective to reduce NOx so that that ratio of NOx to N₂O in the gas stream after passing through the catalyst is greater than 5.

9. The catalyst of claim 2, wherein the catalyst is effective to make less than 10 ppm N₂O over the temperature range of 200°

C. to 450°

C.

10. The catalyst of claim 2, wherein the catalyst is effective to make less than 5 ppm N₂O over the temperature range of 200°

C. to 450°

C.

11. The catalyst of claim 2, wherein the Cu-SAPO-34 contains a secondary metal.

12. The catalyst of claim 11, wherein the secondary metal comprises zirconium.

13. The catalyst of claim 2, the Cu-SAPO-34 contains in the range of about 2 weight percent and 4 weight percent Cu.

14. A catalyst composite, wherein the catalyst of claim 2 is deposited on a honeycomb substrate as a washcoat at a loading in the range of about 0.5 g/in³ and 3.5 g/in³.

15. The catalyst composite of claim 14, wherein the honeycomb substrate comprises a wall flow substrate.

16. The catalyst composite of claim 14, wherein the honeycomb substrate comprises a flow through substrate.

17. The catalyst composite of claim 16, wherein at least a portion of the flow through substrate is coated with a washcoat containing Pt and a metal-loaded non-zeolitic molecular sieve to oxidize ammonia in the exhaust gas stream.

18. The catalyst composite of claim 15, wherein at least a portion of the wall flow substrate is coated with a washcoat containing Pt and a metal-loaded non-zeolitic molecular sieve to oxidize ammonia in the exhaust gas stream.

19. An exhaust gas treatment system comprising an oxidation catalyst and the catalyst composite of claim 15.

20. An exhaust gas treatment system comprising an oxidation catalyst and the catalyst composite of claim 16.

21. The catalyst of claim 2, wherein the Cu-SAPO-34 material is combined with a metal containing zeolitic SCR catalyst.

22. The catalyst of claim 3, wherein the Cu-SAPO-34 material is combined with a metal containing zeolitic SCR catalyst.

23. A process for the reduction of oxides of nitrogen contained in a gas stream in the presence of oxygen comprising contacting the gas stream with a Cu-loaded non-zeolitic molecular sieve having the CHA crystal structure and having a Cu loading so that the catalyst is effective to selectively reduce nitrogen oxides with ammonia in the presence of oxygen in an exhaust gas stream at 200°

C. when the catalyst has been deposited on a honeycomb substrate having a cell density of 400 cpsi at a loading between about 2 and 2.5 g/in³ and tested at a space velocity of 80,000 hr<sup>−

1</sup> where the feed stream comprise a mixture of 10% O₂, 5% H₂O, 500 ppm NO and 500 ppm NH₃ to provide at least 80% NOx conversion.

24. An emission treatment system for treatment of an exhaust stream comprising NOx and particulate matter, the emission treatment system comprising:

an oxidation catalyst and a Cu-loaded non-zeolitic molecular sieve having a Cu loading so that the catalyst is effective to selectively reduce nitrogen oxides with ammonia in the presence of oxygen in an exhaust gas stream at 200°

C. when the catalyst has been deposited on a honeycomb substrate having a cell density of 400 cpsi at target a loading between about 2 and 2.5 g/in³ and tested at a space velocity of 80,000 hr<sup>−

1</sup> where the feed stream is a mixture of 10% O₂, 5% H₂O, 500 ppm NO and 500 ppm NH₃ to provide at least 80% NOx conversion.

25. A process for synthesizing Cu-SAPO-34 comprising:

mixing a neutral, nitrogen-containing organic template, an alumina source, a silica source and a phosphorous source in a gel mixture;

heating the gel to less than about 200°

C. for at least about 12 hours to form crystalline SAPO-34;

filtering and washing the crystalline SAPO-34;

calcining the crystalline SAPO-34; and

ion exchanging the crystalline SAPO-34 with a copper salt to provide Cu-SAPO-34.

26. The process of claim 25, wherein the template comprises morpholine and the heating temperature is less than about 185°

C. and the heating time is at least about 24 hours.

27. The process of claim 26, wherein the copper salt comprises copper acetate.

28. The process of claim 25, wherein after ion exchanging the crystalline SAPO-34 with a copper salt to provide Cu-SAPO-34, Cu-SAPO-34 is washed to provide a filtrate having a conductivity less than about 600 μ

Scm<sup>−

1</sup>.

29. The process of claim 25, wherein the Cu-SAPO-34 is washed to provide a filtrate having a conductivity less than about 400 μ

Scm<sup>−

1</sup>.

30. The process of claim 25, wherein the Cu-SAPO-34 is washed to provide a filtrate having a conductivity less than about 200 μ

Scm<sup>−

1</sup> and less than about 200 μ

Scm<sup>−

1</sup>,

31. The process of claim 28, further comprising calcining the washed Cu-SAPO-34 material at a temperature less than about 600°

C.

32. The process of claim 25, wherein the crystalline material has a crystal size having 90% of the crystals less than 20 microns.

33. The process of claim 25, wherein the crystalline material has a crystal size having 90% of the crystals less than 15 microns.

34. A catalyst made by the method of claim 25 having a Cu loading so that the catalyst is effective to selectively reduce nitrogen oxides with ammonia in the presence of oxygen in an exhaust gas stream at 200°

C. when the catalyst has been deposited on a honeycomb substrate having a cell density of 400 cpsi at target a loading between about 2 and 2.5 g/in³ and tested at a space velocity of 80,000 hr<sup>−

1</sup> where the feed stream comprise a mixture of 10% O₂, 5% H₂O, 500 ppm NO and 500 ppm NH₃ to provide at least 80% NOx conversion.

35. A catalyst composite, wherein the catalyst of claim 25 is deposited on a honeycomb substrate as a washcoat at a loading in the range of about 0.5 g/in³ and 3.5 g/in³.

36. The catalyst of claim 35, wherein the honeycomb substrate comprises a wall flow substrate.

37. The catalyst of claim 35, wherein the honeycomb substrate comprises a flow through substrate.