Mixed template synthesis of high silica Cu-CHA
A transition-metal-CHA molecular sieve catalyst and mixed-template synthesis procedure are disclosed.
1. A composition comprising a synthetic zeolite having a CHA framework structure, a molar silica-to-alumina ratio SAR of about 25 to about 150, and copper in the form of non-framework copper uniformly dispersed within the cavities and channels of the zeolite and free copper oxide, wherein the zeolite contains not more than about 5 weight percent free copper oxide, relative to the total amount of the copper in the zeolite, wherein the zeolite has a unit cell volume of about 2355 to about 2375 Å 3 , and wherein the zeolite has a phase purity of at least 95% by weight.
2. The composition of claim 1 , wherein zeolite contains about 0.05 to about 5 weight percent copper.
3. The composition of claim 1 , wherein zeolite contains uniformly distributed ionic copper.
4. The composition of claim 1 , wherein the zeolite contains less than 5 weight percent CuO based on the total weight of the zeolite.
5. A catalyst article for treating exhaust gas comprising a catalyst composition according to claim 1 disposed on and/or within a honeycomb monolith substrate.
6. The composition of claim 1 , wherein the zeolite is essentially free of sodium.
7. A catalyst article for treating exhaust gas comprising a catalyst composition according to claim 6 disposed on and/or within a honeycomb monolith substrate.
8. A method for synthesizing a zeolite comprising:
preparing a reaction mixture comprising (a) at least one source of alumina, (b) at least one source of silica, (c) a copper-amine organic templating agent, (d) seed crystals, and (e) distinct second organic templating agent, wherein each of the first and second templating agents is suitable for forming a CHA framework structure and wherein the reaction mixture is essentially free of fluorine; heating the reaction mixture at crystallization conditions for a sufficient time to form zeolite crystals having a CHA framework, a molar silica-to-alumina ratio SAR of about 25 to about 150, and copper in the form of non-framework copper uniformly dispersed within the cavities and channels of the zeolite and free copper oxide, wherein the zeolite contains not more than about 5 weight percent free copper oxide, relative to the total amount of the copper in the zeolite, wherein the zeolite has a unit cell volume of about 2355 to about 2375 Å 3 , and wherein the zeolite has a phase purity of at least 95% by weight.
9. The method of claim 8 , wherein a majority of the copper is ionic metal dispersed in the crystallized zeolite.
10. The method of claim 8 , wherein the copper-amine organic templating agent is formed in-situ in the reaction mixture from individual metal and amine components.
11. The method of claim 8 , wherein the copper-amine organic templating agent is Cu-TEPA.
12. The method of claim 11 , wherein the second organic templating agent is DMECHA.
13. The method of claim 8 , wherein the zeolite has a SAR of about 30 to about 120.
14. The method of claim 8 , wherein the zeolite contains about 0.05 to about 5 weight percent ionic copper.
15. The method of claim 8 , wherein the zeolite is washed, dried, and calcined to form a Cu-CHA catalyst.
16. The method of claim 8 , wherein the reaction mixture is essentially fee of sodium.
17. A method for treating an exhaust gas comprising contacting a combustion exhaust gas containing NOx and/or NH3 with a catalyst article according to claim 5 to selectively reduce at least a portion of the NOx into N2 and H2O and/or oxidize at least a portion of the NH3.