AMMONIA SCR CATALYST AND METHOD OF USING THE CATALYST

• US 20090304566A1
• Filed: 07/09/2009
• Published: 12/10/2009
• Est. Priority Date: 01/09/2007
• Status: Active Grant

• Current Assignee: Catalyst Health Solutions Incorporated (UnitedHealth Group Incorporated)
• Original Assignee: Catalyst Health Solutions Incorporated (UnitedHealth Group Incorporated)
• Inventors: Iretskaya, Svetlana, Golden, Stephen J.
• Granted Patent: US 7,767,175 B2
• Time in Patent Office: Days
• US Class Current: 423/239.200
• CPC Class Codes: B01D 2251/2062 Ammonia
• CPC Class Codes: B01D 2255/204 Alkaline earth metals
• CPC Class Codes: B01D 2255/2063 Lanthanum
• CPC Class Codes: B01D 2255/2065 Cerium
• CPC Class Codes: B01D 2255/2066 Praseodymium
• CPC Class Codes: B01D 2255/2073 Manganese
• CPC Class Codes: B01D 2255/20738 Iron
• CPC Class Codes: B01D 2255/20746 Cobalt
• CPC Class Codes: B01D 2255/20753 Nickel
• CPC Class Codes: B01D 2255/20761 Copper
• CPC Class Codes: B01D 2255/407 Zr-Ce mixed oxides
• CPC Class Codes: B01D 2255/50 Zeolites
• CPC Class Codes: B01D 2255/504 ZSM 5 zeolites
• CPC Class Codes: B01D 2255/9155 Wall flow filters
• 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 23/34 Manganese
• CPC Class Codes: B01J 29/061 containing metallic elements added to the zeolite
• 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 29/48 containing arsenic, antimony, bismuth, vanadium, niobium tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
• CPC Class Codes: B01J 29/7815 Zeolite Beta
• CPC Class Codes: B01J 37/0242 : Coating followed by impregnation
• CPC Class Codes: B01J 37/0246 : Coatings comprising a zeolite

Abstract

A DPF with an SCR catalyst and a method for selectively reducing nitrogen oxides with ammonia, filtering particulates, and reducing the ignition temperature of soot on a DPF are provided. The catalyst includes a first component of copper, chromium, cobalt, nickel, manganese, iron, niobium, or mixtures thereof, a second component of cerium, a lanthanide, a mixture of lanthanides, or mixtures thereof, and a component characterized by increased surface acidity. The catalyst may also include strontium as an additional second component. The catalyst selectively reduces nitrogen oxides to nitrogen with ammonia and oxidizes soot at low temperatures. The catalyst has high hydrothermal stability.

Claims

1. An apparatus for reducing NOx in an exhaust stream, comprising:

a particulate filter; and

a selective catalytic reduction catalyst disposed on the particulate filter, wherein the catalyst comprises;

a first component selected from the group consisting of copper, chromium, cobalt, nickel, manganese, iron, niobium, and mixtures thereof;

a second component selected from the group consisting of cerium, a lanthanide, a mixture of lanthanides, and mixtures thereof; and

at least one material characterized by increased surface acidity.

2. The apparatus of claim 1, wherein the apparatus further comprises a source of ammonia upstream from the particulate filter, wherein the source of ammonia adds ammonia to the exhaust stream.

3. The apparatus of claim 2, further comprising a diesel oxidation catalyst upstream from the particulate filter and upstream from the source of ammonia.

4. The apparatus of claim 2 wherein the source of ammonia comprises urea, ammonium hydroxide, ammonium formate, ammonia gas or other suitable source and combination of any thereof.

5. The apparatus of claim 1 wherein the selective catalytic reduction catalyst further comprises an oxygen storage material.

6. The apparatus of claim 1, wherein the selective catalytic reduction catalyst comprises from about 1 to about 20 percent of the first component calculated on the basis of the metal, from about 2 to about 35 percent of the second component calculated on the basis of the metal, and from about 10 to about 90 percent of the material characterized by increased surface acidity.

7. The apparatus of claim 6, wherein the selective catalytic reduction catalyst further comprises strontium.

8. The apparatus of claim 7, wherein the selective catalytic reduction catalyst further comprises from about 2 to about 35 percent strontium.

9. The apparatus of claim 1, wherein the at least one material characterized by increased surface acidity is selected from the group consisting of aluminum dioxide and zirconium dioxide which had surface properties modified by treatment with a material selected from the group consisting of sulfur, tungsten, phosphorus, silicon, titanium, and molybdenum, or any other materials which could modify surface acidity, and a zeolite.

10. The apparatus of claim 9, wherein the zeolite is selected from the group consisting of ZSM-5, zeolite beta, a ZSM-type zeolites, MCM-type zeolites, mordenite, faujasite, ferrierite, and combinations thereof

11. The apparatus of claim 10, wherein the first component comprises manganese, the second component comprises cerium, and the at least one material characterized by increased surface acidity comprises ZSM-5.

12. The apparatus of claim 5, wherein the selective catalytic reduction catalyst comprises from about 10 to about 90 percent oxygen storage material on the basis of the oxides, and the oxygen storage material is selected from the group consisting of Ce_1-aZr_aO₂ and Ce_1-c-dZr_cLan_dO₂, wherein Lan is selected from the group consisting of Y, La, Pr, Nd, Sm, Eu, Gd, Ho, Yb and mixtures thereof.

13. The apparatus of claim 1, further comprising at least one inorganic oxide selected from the group consisting of alumina, silica, titania, and silica-alumina solutions, composites, and mixtures thereof.

14. The apparatus of claim 1, wherein a wash-coat loading of the selective catalytic reduction catalyst on the particulate filter comprises from about 5 to about 300 g/L.

28. The method of claim 1, wherein the particulate filter comprises a diesel particulate filter.

15. A method for selective catalytic reduction of pollutants in an exhaust stream, removing particulates from an exhaust stream, and reduction of soot ignition temperature in a particulate filter, comprising:

directing the exhaust stream through a particulate filter comprising a selective catalytic reduction catalyst, comprising;

a first component selected from the group consisting of copper, chromium, cobalt, nickel, manganese, iron, niobium, and mixtures thereof;

a second component selected from the group consisting of cerium, a lanthanide, a mixture of lanthanides, and mixtures thereof; and

at least one material characterized by increased surface acidity.

16. The method of claim 15, wherein the particulate filter is a diesel particulate filter, and the method further comprising:

adding ammonia to the exhaust stream; and

introducing the exhaust stream to a diesel oxidation catalyst before adding ammonia to the exhaust stream.

17. The method of claim 16 wherein the source of ammonia comprises urea, ammonium hydroxide, ammonium formate, ammonia gas or other suitable source.

18. The method of claim 15 wherein the selective catalytic reduction catalyst further comprises an oxygen storage material.

19. The method of claim 15, wherein the selective catalytic reduction catalyst comprises from about 1 to about 20 percent of the first component calculated on the basis of the metal, from about 2 to about 35 percent of the second component calculated on the basis of the metal, and from about 10 to about 90 percent of the material characterized by increased surface acidity.

20. The method of claim 19, wherein the selective catalytic reduction catalyst further comprises strontium.

21. The method of claim 20, wherein the selective catalytic reduction catalyst further comprises from about 2 to about 35 percent strontium.

22. The method of claim 15, wherein the at least one material characterized by increased surface acidity is selected from the group consisting of aluminum dioxide and zirconium dioxide which had surface properties modified by treatment with a material selected from the group consisting of sulfur, tungsten, phosphorus, silicon, titanium, and molybdenum, or any other materials which could modify surface acidity, and a zeolite.

23. The method of claim 22, wherein the zeolite is selected from the group consisting of ZSM-5, zeolite beta, a ZSM-type zeolites, MCM-type zeolites, mordenite, faujasite, ferrierite, and combinations thereof

24. The method of claim 23, wherein the first component comprises manganese, the second component comprises cerium, and the at least one material characterized by increased surface acidity comprises ZSM-5.

25. The method of claim 18, wherein the selective catalytic reduction catalyst comprises from about 10 to about 90 percent oxygen storage material on the basis of the oxides, and the oxygen storage material is selected from the group consisting of Ce_1-aZr_aO₂ and Ce_1-c-dZr_cLan_dO₂, wherein Lan is selected from the group consisting of Y, La, Pr, Nd, Sm, Eu, Gd, Ho, Yb and mixtures thereof.

26. The method of claim 15, further comprising at least one inorganic oxide selected from the group consisting of alumina, silica, titania, and silica-alumina solutions, composites, and mixtures thereof.

27. The method of claim 15, wherein a wash-coat loading of the selective catalytic reduction catalyst on the diesel particulate filter comprises from about 5 to about 300 g/L.