초록 ▼

The present invention is directed to a metal-promoted zeolite beta catalyst useful in the selective catalytic reduction of nitrogen oxides with ammonia in which the zeolite beta is pre-treated so as to provide the zeolite with improved hydrothermal stability. The stabilized beta zeolite is provided

The present invention is directed to a metal-promoted zeolite beta catalyst useful in the selective catalytic reduction of nitrogen oxides with ammonia in which the zeolite beta is pre-treated so as to provide the zeolite with improved hydrothermal stability. The stabilized beta zeolite is provided by incorporating into the zeolite structure non-framework aluminum oxide chains. The aluminum oxide chains can be incorporated into the zeolite structure by a unique steaming regimen or by treatment with rare earth metals, such as cerium. The treatment process is unlike well-known methods of dealuminizing zeolites for the purpose of increasing the silica to alumina ratio. In the present invention, the non-framework aluminum oxide is characterized by FT-IR by a peak at 3781짹2 cm-1, which when present, stabilizes the zeolite against further dealumination such as under oxidizing and harsh hydrothermal conditions.

대표청구항 ▼

We claim: 1. A method for the reduction of nitrogen oxides with ammonia, which comprises: contacting a gaseous stream containing nitrogen oxides and ammonia at a temperature of from about 250째 C. to 600째 C. with a catalyst composition comprising: a metal-promoted aluminosilicate zeolite having impr

We claim: 1. A method for the reduction of nitrogen oxides with ammonia, which comprises: contacting a gaseous stream containing nitrogen oxides and ammonia at a temperature of from about 250째 C. to 600째 C. with a catalyst composition comprising: a metal-promoted aluminosilicate zeolite having improved stability formed by presteaming an aluminosilicate zeolite at a temperature of 600째 C.˜800째 C. for a period of time of 0. 25 to 8 hours, said presteaming not providing significant dealumination of said aluminosilicate zeolite, adding metal to said presteamed zeolite, said zeolite having a silica to alumina mole ratio of at least about 8, and a pore structure which is interconnected in all three crystallographic dimensions by pores having an average kinetic pore diameter of at least about 7 Å. 2. The method of claim 1, wherein said metal is added in amounts of from 0.1 to 30% by weight calculated as metal based on the total weight of the metal and aluminosilicate zeolite. 3. The method of claim 2, wherein the metal promoter is present in the amount of from about 0.5 to 2.5 percent by weight of the total weight of the catalytic material. 4. The method of claim 3, wherein the promoter comprises iron. 5. The method of claim 1, wherein the zeolite is selected from the group consisting of USY, beta and ZSM-20. 6. The method of claim 4, wherein the zeolite is beta. 7. The method of claim 1, wherein the catalyst composition further includes a refractory binder admixed with the zeolite. 8. A method for the reduction of nitrogen oxides with ammonia, which comprises: contacting a gaseous stream containing nitrogen oxides and ammonia at a temperature of from about 250째 C. to 600째 C. with a catalyst composition comprising: a stable, metal-promoted aluminosilicate zeolite prepared by ion exchanging an aluminosilicate zeolite with a lanthinide salt and subsequent to said ion exchange with said lanthinide salt, adding a metal promoter by ion-exchange to said lanthinide ion exchanged aluminosilicate zeolite, said zeolite having a silica to alumina mole ratio of at least about 8, and a pore structure which is interconnected in all three crystallographic dimensions by pores having an average kinetic pore diameter of at least about 7 Å. 9. The method of claim 8, wherein said metal is added in amounts of from 0.1 to 30% by weight calculated as metal based on the total weight of the metal and aluminosilicate zeolite. 10. The method of claim 9, wherein the metal promoter is present in the amount of from about 0.5 to 2.5 percent by weight of the total weight of the catalytic material. 11. The method of claim 10, wherein the promoter comprises iron. 12. The method of claim 8, wherein the zeolite is selected from the group consisting of USY, beta and ZSM-20. 13. The method of claim 12, wherein the zeolite is beta. 14. The method of claim 8, wherein the catalyst composition further includes a refractory binder admixed with the zeolite. 15. A method for the reduction of nitrogen oxides with ammonia, which comprises: contacting a gaseous stream containing nitrogen oxides and ammonia at a temperature of from about 250째 C. to 600째 C. with a catalyst composition comprising: (a) a stabilized aluminosilicate zeolite comprising non-framework chains of alternating aluminum and oxygen atoms separate from the framework of the zeolite, at least 10% of the aluminum oxide of said zeolite, being in the form of said non-framework chain, said zeolite having a silica to alumina mole ratio of at least about 8, and a pore structure which is interconnected in all three crystallographic dimensions by pores having an average kinetic pore diameter of at least about 7 Å.; and (b) a metal promoter. 16. The method of claim 15, wherein said metal is added in amounts of from 0.1 to 30% by weight calculated as metal based on the total weight of the metal and aluminosilicate zeolite. 17. The method of claim 16, wherein the metal promoter is present in the amount of from about 0.5 to 2.5 percent by weight of the total weight of the catalytic material. 18. The method of claim 17, wherein the promoter comprises iron. 19. The method of claim 15, wherein the zeolite is selected from the group consisting of USY, beta and ZSM-20. 20. The method of claim 19, wherein the zeolite is beta. 21. The method of claim 15, wherein the catalyst composition further includes a refractory binder admixed with the zeolite. 22. A method for the reduction of nitrogen oxides with ammonia, which comprises: contacting a gaseous stream containing nitrogen oxides and ammonia at a temperature of from about 250째 C. to 600째 C. with a catalyst composition comprising: a stabilized metal-promoted aluminosilicate zeolite having an FT-IR adsorption peak at 3781짹2 cm-1. 23. The method of claim 22, wherein said metal is added in amounts of from 0.1 to 30% by weight calculated as metal based on the total weight of the metal and aluminosilicate zeolite. 24. The method of claim 23, wherein the metal promoter is present in the amount of from about 0.5 to 2.5 percent by weight of the total weight of the catalytic material. 25. The method of claim 24, wherein the promoter comprises iron. 26. The method of claim 22, wherein the zeolite is selected from the group consisting of USY, beta and ZSM-20. 27. The method of claim 26, wherein the zeolite is beta. 28. The method of claim 22, wherein the catalyst composition further includes a refractory binder admixed with the zeolite. 29. The method of claim 1, wherein said gaseous stream is contacted with said catalyst at a temperature of greater than 500째 C. 30. The method of claim 8, wherein said gaseous stream is contacted with said catalyst at a temperature of greater than 500째 C. 31. The method of claim 15, wherein said gaseous stream is contacted with said catalyst at a temperature of greater than 500째 C. 32. The method of claim 22, wherein said gaseous stream is contacted with said catalyst at a temperature of greater than 500째 C. 33. The stabilized aluminosilicate zeolite catalyst of claim 22, wherein said peak has an area of at least 0.1 absorbance unit횞cm-1. 34. The stabilized aluminosilicate zeolite catalyst of claim 22, wherein said peak has an area of at least 0.2 absorbance unit횞cm-1. 35. The method of claim 22, wherein said peak as an area of at least 0.05 absorbance unit횞cm-1. 36. The method of claim 22, wherein said peak as an area of at least 0.1 absorbance unit횞cm-1. 37. The method of claim 22, wherein said peak as an area of at least 0.2 absorbance unit횞cm-1.