Stabilized microporous crystalline material, the method of making the same, and the use for selective catalytic reduction of NO
View Patent ↗There is disclosed a microporous crystalline material comprising a crystal structure having building units of double-6-rings (d6r) and pore opening of 8-rings, wherein the material comprises a first metal chosen from alkali-earth group, rare-earth group, alkali group or mixtures thereof, and a second metal chosen from copper, iron or mixtures thereof, wherein the material has molar silica to alumina ratio (SAR) from 3 to 12, and is further steamed to enhance stability. Methods of making the crystalline material are also disclosed. There is also disclosed a method of selective catalytic reduction of nitrogen oxides in exhaust gas, comprising at least partially contacting the exhaust gases with an article comprising the disclosed microporous crystalline material.
1. A microporous crystalline material having building units of double-6-rings (d6r) and pore opening of 8-rings, wherein the material comprises a first metal chosen from alkali-earth group, rare-earth group, alkali group or mixtures thereof, and a second metal chosen from copper, iron or mixtures thereof,
wherein the material has a molar silica to alumina ratio (SAR) from 3 to 12; and
exhibits an NH 3 adsorption capacity expressed as the molar NH 3 /Al ratio of 0.7 to 0.9.
2. The microporous crystalline material of claim 1 , wherein the material has pore openings ranging from 3 to 5 Angstroms.
3. The microporous crystalline material of claim 1 , wherein the material comprises structural codes of CHA, LEV, AEI, AFT, AFX, EAB, ERI, KFI, SAT, TSC, and SAV.
4. The microporous crystalline material of claim 3 , wherein the material comprises a CHA structure.
5. The microporous crystalline material of claim 4 , wherein the CHA structure has a unit cell angle below 94.55 degrees, and a [3 2 0] peak below 36.05 degrees 2-theta.
6. The microporous crystalline material of claim 4 , wherein the CHA structure has a unit cell angle ranging from 94.30-94.50 degrees.
7. The microporous crystalline material of claim 1 , where the first metal comprises magnesium, calcium, strontium, barium, lanthanum, cerium, praseodymium, neodymium, mixed rare earth oxides, potassium, rubidium, cesium or mixtures thereof.
8. The microporous crystalline material of claim 1 , where the first and second metals are introduced into the material by liquid-phase or solid ion-exchange, impregnation or incorporated by direct-synthesis.
9. The microporous crystalline material of claim 1 , which has a first metal to aluminum atomic ratio ranging from 0.05 to 0.80.
10. The microporous crystalline material of claim 1 , wherein the first metal comprises calcium, and the material has a calcium to aluminum atomic ratio ranging from 0.05 to 0.50.
11. The microporous crystalline material of claim 1 , wherein the second metal comprises copper, and the material has a copper to aluminum atomic ratio ranging from 0.05 to 0.20.
12. The microporous crystalline material of claim 1 , wherein the second metal comprises iron, and the material has an iron to aluminum atomic ratio ranging from 0.05 to 0.30.
13. The microporous crystalline material of claim 1 , wherein the material has a mean crystal size ranging from 0.3 to 5 microns.
14. The microporous crystalline material of claim 1 , wherein the material has been steamed at temperatures ranging from 400 to 800° C. in the presence of steam containing 1-100% water for a time of at least 0.1 hours.
15. The microporous crystalline material of claim 1 , wherein the material retains at least 80% of its surface area after exposure to conditions that include immersion in water at ambient temperature for 1 hour.
16. The microporous crystalline material of claim 15 , wherein the material retains at least 95% of its surface area after said exposure.
17. A method of selective catalytic reduction of nitrogen oxides in exhaust gas, said method comprising:
at least partially contacting said exhaust gases with an article comprising a microporous crystalline material having building units of double-6-rings (d6r) and pore opening of 8-rings, wherein the material comprises a first metal chosen from alkali-earth group, rare-earth group, alkali group or mixtures thereof, and a second metal chosen from copper, iron or mixtures thereof,
wherein the material has a molar silica to alumina ratio (SAR) from 3 to 12; and
exhibits an NH 3 adsorption capacity expressed as the molar NH 3 /Al ratio of 0.7 to 0.9.
18. The method of claim 17 , wherein the material has pore opening ranging from 3 to 5 Angstroms.
19. The method of claim 17 , wherein the material comprises structural codes of CHA, LEV, AEI, AFT, AFX, EAB, ERI, KFI, SAT, TSC, and SAV.
20. The method of claim 19 , wherein the material comprises a CHA structure.
21. The method of claim 20 , wherein the CHA structure has a unit cell angle below 94.55 degrees, and a [3 2 0] peak below 36.05 degrees 2-theta.
22. The method of claim 21 , wherein the CHA structure has a unit cell angle ranging from 94.30-94.50 degrees.
23. The method of claim 17 , wherein the contacting step is performed in the presence of ammonia, urea, an ammonia generating compound, or a hydrocarbon compound.
24. The method of claim 17 , wherein the first metal comprises magnesium, calcium, strontium, barium, lanthanum, cerium, praseodymium, neodymium, mixed rare earth oxides, potassium, rubidium, cesium, or mixtures thereof.
25. The method of claim 17 , where the material comprises a mean crystal size ranging from 0.3 to 5 microns.
26. A method of making a microporous crystalline material,
said method comprising synthesizing a material having building units of double-6-rings (d6r) and pore opening of 8-rings, where the material has molar silica to alumina ratio (SAR) from 3 to 12, wherein the material exhibits an NH 3 adsorption capacity expressed as the molar NH 3 /Al ratio of 0.7 to 0.9;
mixing sources of sodium, potassium, alumina, silica, water and optionally an organic template to form a gel;
heating the gel in a vessel at a temperature ranging from 80 to 200° C. to form a crystalline material;
ammonium-exchanging said material;
introducing a first metal chosen from alkali-earth group, rare-earth group, alkali group or mixtures thereof, and a second metal chosen from copper, iron or mixtures thereof, into said crystalline material by liquid-phase or solid ion-exchange, impregnation; and
steaming said material at 400 to 800° C. in 1 to 100% steam for at least 0.1 hour.
27. The method of claim 26 , wherein the gel has potassium to silica (K/SiO 2 ) molar ratio of less than 0.5 and hydroxide to silica (OH/SiO 2 ) molar ratio less than 0.35.
28. The method of claim 26 , wherein the gel further comprises a crystalline seed material.
29. The method of claim 26 , wherein said first metal and said second metal are incorporated into the structure by direct-synthesis prior to heating said gel.
30. The method of claim 26 wherein said alumina and silica sources comprise potassium-exchanged, proton-exchanged or ammonium-exchanged zeolite Y or; potassium silicate or mixtures thereof.
31. The method of claim 26 , wherein said crystal structure comprises structural codes of CHA, LEV, AEI, AFT, AFX, EAB, ERI, KFI, SAT, TSC, and SAV.
32. The method of claim 31 , wherein said crystal structure comprises CHA.
33. The method of claim 26 , where said first metal comprises magnesium, calcium, strontium, barium, lanthanum, cerium, praseodymium, neodymium, mixed rare earth oxides, potassium, rubidium, cesium, or mixtures thereof.
34. The method of claim 26 , wherein the material exhibits a first metal to aluminum atomic ratio ranges from 0.05 to 0.80.
35. The method of claim 26 , wherein the first metal comprises calcium and the material has a calcium to aluminum atomic ratio ranging from 0.05 to 0.50.
36. The method of claim 26 , wherein the second metal comprises copper and the material has a copper to aluminum atomic ratio ranging from 0.05 to 0.20.
37. The method of claim 26 , wherein the second metal comprises iron and the material has an iron to aluminum atomic ratio ranging from 0.05 to 0.30.
38. The method of claim 26 , where said material has a mean crystal size ranging from 0.3 to 5 microns.