Copper CHA Zeolite Catalysts

• US 20090285737A1
• Filed: 06/08/2009
• Published: 11/19/2009
• Est. Priority Date: 02/27/2007
• Status: Active Grant

• Current Assignee: BASF Corporation (BASF SE)
• Original Assignee: BASF Catalysts LLC (BASF SE)
• Inventors: Koermer, Gerald S., Moini, Ahmad, Dettling, Joseph C., Bull, Ivor, Patchett, Joseph A., Caudle, Matthew T., Boorse, R. Samuel, Jaglowski, William M., Burk, Patrick, Xue, Wen-Mei
• Granted Patent: US 8,404,203 B2
• Time in Patent Office: Days
• US Class Current: 423/213.700
• CPC Class Codes: B01D 2251/206 Ammonium compounds
• 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 2255/9155 Wall flow filters
• CPC Class Codes: B01D 2258/012 Diesel engines and lean burn gasoline engines
• 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 23/42 Platinum
• CPC Class Codes: B01J 23/8926 Copper and noble metals
• CPC Class Codes: B01J 29/072 Iron group metals or copper
• CPC Class Codes: B01J 29/723 CHA-type, e.g. Chabazite, LZ-218
• CPC Class Codes: B01J 29/763 CHA-type, e.g. Chabazite, LZ-218
• CPC Class Codes: B01J 35/19 Catalysts containing parts with different compositions
• 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 37/0246 Coatings comprising a zeolite
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies
• CPC Class Codes: Y10T 428/24149 Honeycomb-like

Abstract

Zeolite catalysts and systems and methods for preparing and using zeolite catalysts having the CHA crystal structure are disclosed. The catalysts can be used to remove nitrogen oxides from a gaseous medium across a broad temperature range and exhibit hydrothermal stable at high reaction temperatures. The zeolite catalysts include a zeolite carrier having a silica to alumina ratio from about 15:1 to about 256:1 and a copper to alumina ratio from about 0.25:1 to about 1:1.

Claims

1. A process for the preparation of a Cu CHA catalyst comprising ion-exchanging a zeolite having the CHA crystal structure in an aqueous solution of copper acetate.

2. The process of claim 1, wherein the copper acetate is copper acetate monohydrate.

3. The process of claim 1, wherein the Cu CHA catalyst has a mole ratio of silica to alumina of from about 15 to about 256 and an atomic ratio of copper an aluminum of from about 0.25 to about 0.5.

4. The process of claim 1, wherein the Cu CHA catalyst contains at least about 2.5 weight percent copper oxide.

5. The process of claim 1, further comprising applying the Cu CHA catalyst as a washcoat slurry to a honeycomb substrate to provide a catalytic article.

6. The process of claim 5, wherein the washcoat slurry further comprises a binder.

7. The process of claim 6, wherein the binder is a zirconium precursor.

8. The process of claim 5, further comprising drying and calcining the catalytic article.

9. The process of claim 5, further comprising providing the catalytic article in an exhaust emission treatment system.

10. The process of claim 9, wherein the NOx conversion performance of the catalytic article at about 200°

C. after hydrothermal aging in 10% steam at 850°

C. for 6 hours is at least 90% of the NOx conversion performance of the catalyst at about 200°

C. prior to hydrothermal aging.

11. The process of claim 9, wherein the exhaust emission treatment system further comprises one or more of a reductant, a SCR catalyst, an oxidation catalyst and a catalyzed soot filter.

12. The process of claim 11, wherein the reductant is ammonia or an ammonia precursor.

13. The process of claim 1, wherein treating the CHA zeolite comprises ion-exchanging NH₄⁺-CHA with the aqueous solution of copper acetate.

14. The process of claim 13, wherein the aqueous solution of copper acetate comprises from about 0.30 M to about 0.40 M [Cu²⁺].

15. The process of claim 14, wherein the ion-exchange reaction is performed at a temperature of from about 45 to about 70°

C.

16. The process of claim 1, wherein ion-exchanging the CHA zeolite with the aqueous solution of copper acetate comprises applying the CHA zeolite as a washcoat slurry to a substrate, drying the substrate, and then dipping the substrate into the aqueous solution of copper acetate.

17. The process of claim 16, wherein the zeolite is NH₄⁺-CHA.

18. The process of claim 1, wherein ion-exchanging the CHA zeolite with the aqueous solution of copper acetate comprises mixing the CHA zeolite and the copper acetate together in slurry form.

19. The process of claim 18, wherein the zeolite is NH₄⁺-CHA.

20. A process for the reduction of oxides of nitrogen contained in a gas stream in the presence of oxygen wherein said process comprises contacting the gas stream with a catalyst comprising zeolite having the CHA crystal structure and a mole ratio of silica to alumina from about 15 to about 256 and an atomic ratio of copper to aluminum from about 0.25 to about 0.50.

21. The process of claim 20, wherein the catalyst is disposed on a honeycomb flow through substrate.

22. The process of claim 21, wherein at least a portion of the flow through substrate is coated with CuCHA adapted to oxidize ammonia in the exhaust gas stream.

23. The process of claim 21, wherein at least a portion of the flow through substrate is coated with Pt and CuCHA adapted to oxidize ammonia in the exhaust gas stream.

24. The process of claim 20, wherein the catalyst is disposed on a honeycomb wall flow substrate.

25. The process of claim 24, wherein at least a portion of the wall flow substrate is coated with CuCHA adapted to oxidize ammonia in the exhaust gas stream.

26. The process of claim 24, wherein at least a portion of the wall flow substrate is coated with Pt and CuCHA adapted to oxidize ammonia in the exhaust gas stream.

27. The process of claim 20, further comprising contacting the exhaust gas stream with a catalyzed soot filter.

28. The process of claim 27, wherein said catalyzed soot filter is upstream of said catalyst.

29. The process of claim 27, wherein said catalyzed soot filter is downstream of said catalyst.

30. The process of claim 27, further comprising contacting the exhaust gas stream with a diesel oxidation catalyst.

31. The exhaust process of claim 30, wherein said diesel oxidation catalyst is upstream of said catalyst comprising a zeolite having the CHA crystal structure.

32. The exhaust process of claim 31, wherein said diesel oxidation catalyst and catalyzed soot filter are upstream from said catalyst comprising a zeolite having the CHA crystal structure.