CHABAZITE ZEOLITE SYNTHESIS WITH COMBINED ORGANIC TEMPLATES
An as-synthesized microporous material having a CHA structure and containing a first and a second organic structure directing agent (OSDA), wherein the first OSDA 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 combined 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 further 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 is a methyl or ethyl; and
at least one second OSDA.
2 . The as-synthesized microporous material of claim 1 , which has a molar silica to alumina ratio (SAR) of about 8 or higher.
3 . The as-synthesized microporous material of claim 2 , wherein the SAR ranges from 8 to 50.
4 . The as-synthesized microporous material of claim 1 , 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 1 , 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 as-synthesized microporous 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 the first OSDA comprises choline cation.
8 . A microporous crystalline material comprising a calcined and ammonium-exchanged material of claim 1 .
9 . The microporous crystalline material of claim 8 , further comprising at least one catalytically active metal.
10 . The microporous crystalline material of claim 9 , where the at least one catalytically active metal comprises copper or iron.
11 . The microporous crystalline material of claim 10 , wherein the catalytically active metal comprises copper Cu, which is present in a CuO of 1-10 wt %.
12 . The microporous crystalline material of claim 10 , wherein the catalytically active metal comprises iron Fe, which is present in a Fe 2 O 3 of 0.2-10 wt %.
13 . The microporous crystalline material of claim 8 , where said material comprises a mean crystal size ranging from 0.3 to 5 microns.
14 . A method of selective catalytic reduction of nitrogen oxides in exhaust gas, said method comprising at least partially contacting said exhaust gas with an article comprising a microporous crystalline material of claim 10 .
15 . The method of claim 14 , where the at least partially contacting step 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 OSDA that has a general structure of the quaternary ammonium cation as follows:
where R is a methyl or ethyl; and
at least one second OSDA.
17 . The method of claim 16 , wherein the microporous crystalline material has a molar silica to alumina ratio (SAR) of about 8 or higher.
18 . The method of claim 16 , wherein the SAR ranges from 8 to 50.
19 . The method of claim 16 , 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.
20 . The method of claim 16 , 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.
21 . The method of claim 16 , wherein the second OSDA comprises a compound chosen from as an amine, monoquaternary ammonium compound, or diquaternary ammonium compound, capable of forming a zeolite with chabazite (CHA) structure.
22 . The method of claim 21 , 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.
23 . The method of claim 16 , wherein the first OSDA comprises choline cation.
24 . The method of claim 20 , further comprising calcining the CH A 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 as CuO of 1-10 wt %.
28 . The method of claim 27 , wherein the catalytically active metal comprises iron Fe as Fe 2 O 3 of 0.2-10 wt %.
29 . The method of claim 19 , where the alkali containing additive comprises a source of potassium or sodium, or a mixture of thereof.