Methods Utilizing Non-Zeolitic Metal-Containing Molecular Sieves Having The CHA Crystal Structure

• US 20110300042A1
• Filed: 08/22/2011
• Published: 12/08/2011
• Est. Priority Date: 01/31/2008
• Status: Active Grant

• Current Assignee: BASF Corporation (BASF SE)
• Original Assignee: BASF Corporation (BASF SE)
• Inventors: Bull, Ivor, Koermer, Gerald S., Moini, Ahmad, Unverricht, Signe
• Granted Patent: US 10,105,649 B2
• Time in Patent Office: Days
• US Class Current: 423/213.2
• 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 35/56 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, 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 method of treating an exhaust gas stream from a diesel/lean burn engine, the method comprising:

contacting the exhaust gas stream with a catalyst comprising a Cu-loaded non-zeolitic molecular sieve having a 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 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 about 70% NOx conversion.

2. The method of claim 1, wherein the catalyst is effective to provide at least about 80% NOx conversion in the exhaust gas stream at 200°

C.

3. The method of claim 1, wherein the catalyst is effective to provide at least about 90% NOx conversion in the exhaust gas stream at 200°

C.

4. The method of claim 1, further comprising the combination of the non-zeolitic molecular sieve with a metal containing zeolitic SCR catalyst selected from beta zeolite, zeolite Y, and ZSM-5.

5. The method of claim 1, wherein the Cu-loaded non-zeolitic molecular sieve having a CHA crystal structure comprises Cu-SAPO-34.

6. The method of claim 4, wherein the Cu-loaded non-zeolitic molecular sieve having a CHA crystal structure comprises Cu-SAPO-34.

7. The method of claim 5, wherein the catalyst is effective to provide at least about 80% NOx conversion in the exhaust gas stream at 200°

C.

8. The method of claim 5, wherein the catalyst is effective to provide at least about 90% NOx conversion in the exhaust gas stream at 200°

C.

9. The method of claim 5, wherein the Cu-SAPO-34, upon hydrothermal aging in 10% stream at 850°

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

C.

10. The method of claim 5, wherein the Cu-SAPO-34, upon hydrothermal aging in 10% stream at 900°

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

C.

11. The method of claim 5, wherein the catalyst is effective to reduce NOx so that the ratio of NOx to N₂O in the exhaust gas stream after passing through the catalyst is greater than 2.5.

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

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

C. to 450°

C.

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

C. to 450°

C.

15. The method of claim 5, wherein the Cu-SAPO-34 contains a secondary metal.

16. The method of claim 15, wherein the secondary metal comprises zirconium.

17. The method of claim 5, wherein the Cu-SAPO-34 material contains in the range of about 2 wt-% to 4 wt-% Cu.

18. A method of treating an exhaust gas stream from a diesel/lean burn engine, the method comprising:

contacting the exhaust gas stream with a catalyst comprising a Cu-loaded non-zeolitic molecular sieve having a 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 low temperature to provide at least about 70% NOx conversion upon hydrothermal aging.

19. 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 about 70% NOx conversion.