Chabazite zeolite synthesis with organic templates
An as-synthesized microporous material having a CHA structure and containing at least one organic structure directing agent that has the following general structure of the quaternary ammonium cation is disclosed: A microporous crystalline material made from the as-synthesized material is also disclosed. A method of making microporous crystalline material using one or more organic structure directing agents is also disclosed. A method of selective catalytic reduction of nitrogen oxides in exhaust gas that comprises contacting exhaust gases, typically in the presence of ammonia, urea, an ammonia generating compound, or a hydrocarbon compound, with an article comprising the disclosed microporous crystalline is also disclosed.
1. An as-synthesized microporous material having a CHA structure and comprising a first organic structure directing agent (OSDA) that has a general structure of the quaternary ammonium cation as follows:
where R 1 is a C 1 -C 5 derivatized or underivatized alkyl chain, and
R 2 is a C 2 -C 5 derivatized or underivatized alkyl chain,
where X is H (hydrogen) or a C 1 -C 3 alkyl substituent group or groups, derivatized or underivatized, attached to at least one carbon atom constituting the hexahydro-1H-azepinium ring.
2. The as-synthesized microporous material of claim 1 , which has a molar silica to alumina ratio (SAR) of about 10 or higher.
3. The as-synthesized microporous material of claim 2 , wherein the SAR ranges from 10 to 50.
4. The as-synthesized microporous material of claim 1 , further comprising at least one second OSDA, wherein the first OSDA and the second OSDA are a hydroxide or a salt chosen from fluoride, chloride, bromide, iodide, or a mixture of thereof.
5. The as-synthesized microporous material of claim 4 , wherein the second OSDA comprises a compound chosen from an amine, monoquaternary ammonium compound, or diquaternary ammonium compound, capable of forming a zeolite with chabazite (CHA) structure.
6. The microporous crystalline material of claim 5 , wherein the second OSDA is chosen from N,N,N-trimethyl-1-adamantylammonium, N,N-dimethyl-N-ethylcyclohexylammonium, N,N-dimethylpyrrolidinium, N,N-dimethylpiperidinium, N,N-dimethylhexahydroazepinium, benzyltrimethylammonium, and mixtures thereof.
7. The as-synthesized microporous material of claim 1 , wherein at least one of R 1 and R 2 is ethyl.
8. The as-synthesized microporous material of claim 1 , wherein the first OSDA comprises N,N-diethylhexahydro-1H-azepinium.
9. A microporous crystalline material made by calcining and optionally ammonium-exchanging the as-synthesized microporous material of claim 1 .
10. The microporous crystalline material of claim 9 , further comprising at least one catalytically active metal.
11. The microporous crystalline material of claim 10 , where the at least one catalytically active metal comprises copper or iron.
12. The microporous crystalline material of claim 11 , wherein the catalytically active metal comprises copper Cu, which is present as CuO in an amount of 1-10 wt % of the microporous crystalline material.
13. The microporous crystalline material of claim 11 , wherein the catalytically active metal comprises iron Fe, which is present as Fe 2 O 3 in an amount of 0.2-10 wt % of the microporous crystalline material.
14. A method of selective catalytic reduction of nitrogen oxides in exhaust gas, said method comprising contacting said exhaust gases with an article comprising a microporous crystalline material according to claim 11 .
15. The method of claim 14 , where said contacting is performed in the presence of ammonia, urea, an ammonia generating compound, or a hydrocarbon compound.
16. A method of synthesizing a microporous crystalline material having a CHA structure and comprising a first organic structure directing agent (OSDA) that has a general structure of the quaternary ammonium cation as follows:
where R 1 is a C 1 -C 5 derivatized or underivatized alkyl chain, and
R 2 is a C 2 -C 5 derivatized or underivatized alkyl chain,
where X is H (hydrogen) or a C 1 -C 3 alkyl substituent group or groups, derivatized or underivatized, attached to at least one carbon atom constituting the hexahydro-1H-azepinium ring, the method comprising:
mixing sources of alumina, silica, one or more OSDAs, optionally alkali containing additive, water and optionally a seed material to form a gel; and
heating the gel in an autoclave to form a crystalline CHA product.
17. The method of claim 16 , wherein the microporous crystalline material has a molar silica to alumina ratio (SAR) of about 10 or higher.
18. The method of claim 17 , wherein the SAR ranges from 10 to 50.
19. The method of claim 16 , further comprising at least one second OSDA, wherein the first OSDA and the second OSDA are a hydroxide or a salt chosen from fluoride, chloride, bromide, iodide, or a mixture of thereof.
20. The method of claim 19 , wherein the second OSDA comprises a compound chosen from an amine, monoquaternary ammonium compound, or diquaternary ammonium compound, capable of forming a zeolite with chabazite (CHA) structure.
21. The method of claim 20 , wherein the second OSDA is chosen from N,N,N-trimethyl-1-adamantylammonium, N,N-dimethyl-N-ethylcyclohexylammonium, N,N-dimethylpyrrolidinium, N,N-dimethylpiperidinium, N,N-dimethylhexahydroazepinium, benzyltrimethylammonium, and mixtures thereof.
22. The method of claim 16 , wherein at least one of R1 and R2 is ethyl.
23. The method of claim 16 , wherein the first OSDA comprises N,N-diethylhexahydro-1H-azepinium.
24. The method of claim 16 , further comprising calcining said CHA product; and optionally ammonium-exchanging said CHA product.
25. The method of claim 24 , further comprising introducing at least one catalytically active metal into the microporous crystalline material by liquid-phase or solid-phase ion exchange, impregnation, direct synthesis or combinations thereof.
26. The method of claim 25 , where the at least one catalytically active metal comprises copper or iron.
27. The method of claim 26 , wherein the catalytically active metal comprises copper Cu, which is present as CuO in an amount of 1-10 wt % of the microporous crystalline material.
28. The method of claim 26 , wherein the catalytically active metal comprises iron Fe, which is present as Fe 2 O 3 in an amount of 0.2-10 wt % of the microporous crystalline material.
29. The method of claim 16 , where the alkali containing additive comprises a source of potassium or sodium, or a mixture of thereof.