Synthesis of AFX framework type molecular sieves
A method is provided for the synthesis of AFX framework type molecular sieves using a structure directing agent selected from one or more of hexamethonium dications, 1,6-bis(N-methylpyrrolidinium)hexane dications, and 1,4-bis(N-methylpyrrolidinium)butane dications.
1. A method of synthesizing a molecular sieve of AFX framework type, the method comprising:
(a) preparing a reaction mixture comprising:
(1) a source of silicon oxide;
(2) a source of aluminum oxide;
(3) a source of a Group 1 metal (M) comprising sodium, but substantially no potassium;
(4) a structure directing agent (Q) comprising one or more of hexamethonium dications, 1,6-bis(N-methylpyrrolidinium)hexane dications, and 1,4-bis(N-methylpyrrolidinium)butane dications;
(5) a source of hydroxide ions; and
(6) water; and
(b) subjecting the reaction mixture to crystallization conditions sufficient to form crystals of the molecular sieve.
2. The method of claim 1 , wherein the reaction mixture has a composition, in terms of molar ratios, as follows:
SiO 2 /Al 2 O 3
5 to 100
M/SiO 2
0.05 to 1.00
Q/SiO 2
0.05 to 0.50
OH/SiO 2
0.05 to 1.00
H 2 O/SiO 2
10 to 60.
3. The method of claim 1 , wherein the reaction mixture has a composition, in terms of molar ratios, as follows:
SiO 2 /Al 2 O 3
30 to 80
M/SiO 2
0.30 to 0.60
Q/SiO 2
0.05 to 0.20
OH/SiO 2
0.20 to 0.70
H 2 O/SiO 2
15 to 40.
4. The method of claim 1 , wherein the crystallization conditions include a temperature of from 125° C. to 200° C.
5. A molecular sieve of AFX framework type and, in its as-synthesized form, comprising one or more of hexamethonium dications, 1,6-bis(N-methylpyrrolidinium)hexane dications, and 1,4-bis(N-methylpyrrolidinium)butane dications in its pores.
6. The molecular sieve of claim 5 , having a SiO 2 /Al 2 O 3 molar ratio in a range of from 5 to 50.
7. The molecular sieve of claim 5 , having a SiO 2 /Al 2 O 3 molar ratio in a range of from 5 to 25.