METHOD FOR MAKING MOLECULAR SIEVE SSZ-91
Methods for making a family of new crystalline molecular sieves designated SSZ-91 are disclosed. Molecular sieve SSZ-91 is structurally similar to sieves falling within the ZSM-48 family of molecular sieves, and is characterized as: (1) having a low degree of faulting, (2) a low aspect ratio that inhibits hydrocracking as compared to conventional ZSM-48 materials having an aspect ratio of greater than 8, and (3) is substantially phase pure.
1 . A method of preparing molecular sieve SSZ-27, comprising:
(a) preparing a reaction mixture containing:
at least one source of silicon,
at least one source of aluminum,
at least one source of an element selected from Groups 1 and 2 of the Periodic Table,
hydroxide ions,
hexamethonium cations, and
water; and
(b) subjecting the reaction mixture to crystallization conditions sufficient to form crystals of the molecular sieve;
wherein the molecular sieve comprises:
a silicon oxide to aluminum oxide mole ratio of 40 to 200,
at least 70% polytype 6 of the total ZSM-48-type material present in the product, and
an additional EUO-type molecular sieve phase in an amount of between 0 and 3.5 percent by weight of the total product; and
wherein the molecular sieve has a morphology characterized as polycrystalline aggregates comprising crystallites collectively having an average aspect ratio of between 1 and 8.
2 . The method of claim 1 , wherein the molecular sieve has, in its as-synthesized form, an X-ray diffraction pattern substantially as shown in the following Table:
2-Theta (a)
d-spacing (nm)
Relative Intensity (b)
7.55 ± 0.20
1.170
W
8.71 ± 0.20
1.015
W
12.49 ± 0.20
0.708
W
15.12 ± 0.20
0.586
W
21.18 ± 0.20
0.419
VS
22.82 ± 0.20
0.390
VS
24.62 ± 0.20
0.361
W
26.39 ± 0.20
0.337
W
29.03 ± 0.20
0.307
W
31.33 ± 0.20
0.285
W
3 . The method of claim 1 , wherein the molecular sieve is prepared from a reaction mixture comprising, in terms of mole ratios, the following:
SiO 2 /Al 2 O 3
50-220
M/SiO 2
0.05-1.0
Q/SiO 2
0.01-0.2
OH/SiO 2
0.05-0.4
H 2 O/SiO 2
3-100
wherein M is selected from the group consisting of elements from Groups 1 and 2 of the Periodic Table; and Q is a hexamethonium cation.
4 . The method of claim 1 , wherein the molecular sieve is prepared from a reaction mixture comprising, in terms of mole ratios, the following:
SiO 2 /Al 2 O 3
85-180
M/SiO 2
0.1-0.8
Q/SiO 2
0.02-0.1
OH/SiO 2
0.10-0.3
H 2 O/SiO 2
10-50
wherein M is selected from the group consisting of elements from Groups 1 and 2 of the Periodic Table; and Q is a hexamethonium cation.
5 . The method of claim 1 , wherein the molecular sieve has a silicon oxide to aluminum oxide mole ratio of 70 to 160.
6 . The method of claim 1 , wherein the molecular sieve has a silicon oxide to aluminum oxide mole ratio of 80 to 140.
7 . The method of claim 6 , wherein the molecular sieve comprises at least 90% polytype 6 of the total ZSM-48-type material present in the product.
8 . The method of claim 1 , wherein the crystallites collectively have an average aspect ratio of between 1 and 5.
9 . The method of claim 1 , wherein the molecular sieve comprises between 0.1 and 2 wt. % EU-1.
10 . The method of claim 1 , wherein the molecular sieve comprises at least 80% polytype 6 of the total ZSM-48-type material present in the product.
11 . The method of claim 10 , wherein the crystallites collectively have an average aspect ratio of between 1 and 5.
12 . The method of claim 11 , wherein the molecular sieve comprises between 0.1 and 2 wt. % EU-1.
13 . The method of claim 10 , wherein the molecular sieve comprises between 0.1 and 2 wt. % EU-1.
14 . The method of claim 1 , wherein the molecular sieve comprises at least 90% polytype 6 of the total ZSM-48-type material present in the product.
15 . The method of claim 14 , wherein the crystallites collectively have an average aspect ratio of between 1 and 5.
16 . The method of claim 15 , wherein the molecular sieve comprises between 0.1 and 2 wt. % EU-1.
17 . The method of claim 14 , wherein the molecular sieve comprises between 0.1 and 2 wt. % EU-1.
18 . The method of claim 1 , wherein the crystallites collectively have an average aspect ratio of between 1 and 5.
19 . The method of claim 18 , wherein the molecular sieve comprises at least 90% polytype 6 of the total ZSM-48-type material present in the product.
20 . The method of claim 1 , wherein the crystallites collectively have an average aspect ratio of between 1 and 3.