Systems utilizing non-zeolitic metal-containing molecular sieves having the CHA crystal structure

• US 8,617,474 B2
• Filed: 08/22/2011
• Issued: 12/31/2013
• 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 Stephen, Moini, Ahmad, Unverricht, Signe
• Primary Examiner(s): WOOD, ELIZABETH D
• Application Number:
  US13/214,445
• Publication Number:
  US 20110300028A1
• Time in Patent Office: 862 Days
• Field of Search: 422/171, 422/172, 422/180, 502/11, 502/214
• US Class Current: 422/171
• 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

Systems for treating exhaust gas incorporating catalysts comprising metal-loaded non-zeolitic molecular sieves having the CHA crystal structure, including Cu-SAPO-34, and methods for preparing 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. An emission treatment system for treatment of an exhaust gas stream comprising NOx and particulate matter, the emission treatment system comprising:

a SCR catalyst substrate containing a catalyst comprising a Cu-loaded non-zeolitic molecular sieve having a CHA crystal structure; and

an ammonia injector or an ammonia-precursor injector positioned upstream of the SCR catalyst substrate for injecting ammonia or an ammonia-precursor, wherein the catalyst is effective to promote the reaction of ammonia with nitrogen oxides to form nitrogen and H₂O selectively.

2. The emission treatment system of claim 1, wherein the Cu-loaded non-zeolitic molecular sieve having a CHA crystal structure comprises Cu-SAPO-34.

3. The emission treatment system of claim 2, wherein the Cu-SAPO-34 contains a secondary metal.

4. The emission treatment system of claim 3, wherein the secondary metal comprises zirconium.

5. The emission treatment system of claim 2, wherein the Cu-SAPO-34 contains in the range of about 2 wt-% to 4 wt-% Cu.

6. The emission treatment system of claim 1, wherein the Cu-loaded non-zeolitic molecular sieve having a CHA crystal structure is combined with a metal containing zeolite SCR catalyst selected from Beta zeolite, zeolite Y, and ZSM-5.

7. The emission treatment system of claim 6, wherein the Cu-loaded non-zeolitic molecular sieve having a CHA crystal structure comprises Cu-SAPO-34.

8. The emission treatment system of claim 1, wherein the system comprises an ammonia-precursor injector including mixing station to mix air with aqueous urea and a valve.

9. The emission treatment system of claim 8, further comprising:

a mixing station for mixing the aqueous urea with air; and

a valve for metering precise amounts of aqueous urea.

10. The emission treatment system of claim 1, further comprising a second substrate interposed between the ammonia injector or ammonia-precursor injector and the SCR catalyst substrate.

11. The emission treatment system of claim 10, wherein the second substrate is coated with a SCR catalyst composition.

12. The emission treatment system of claim 10, wherein the second substrate is selected from a honeycomb flow through substrate, an open cell foam substrate, or a honeycomb wall flow substrate.

13. The emission treatment system of claim 1, further comprising an oxidation catalyst upstream of the ammonia injector or ammonia-precursor injector.

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

a SCR catalyst substrate containing a catalyst comprising a Cu-loaded non-zeolitic molecular sieve having a CHA crystal structure and 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; and

an ammonia injector or an ammonia-precursor injector positioned upstream of the SCR catalyst substrate for injecting ammonia or an ammonia-precursor, wherein the catalyst is effective to promote the reaction of ammonia with nitrogen oxides to form nitrogen and H₂O selectively.