Synthesis of ZSM-48 crystals

Patent metadata

Field	Value
Publication number	US-9873614-B2
Application number	US-201414549740-A
Country	US
Kind code	B2
Filing date	Nov 21, 2014
Priority date	Dec 26, 2013
Publication date	Jan 23, 2018
Grant date	Jan 23, 2018

Abstract

Methods are provided for synthesis of substantially pure phase ZSM-48 crystals having a fiber or needle morphology based on synthesis mixtures containing non-sodium alkali metal ions, where the structure directing agent in the synthesis mixture can be a diquaternary alkylammonium salt with a 6-carbon atom chain between the ammonium ions (diquat-6). The methods described herein can be used to make ZSM-48 crystals having a fiber and/or needle crystal morphology from a synthesis mixture containing a diquat-6 structure directing agent. The desired morphology can be achieved in part by reducing, minimizing, and/or eliminating the presence of sodium ions in the synthesis mixture.

First claim

What is claimed is:

1. A method of synthesizing ZSM-48 crystals, at least 25 vol % of the as-synthesized crystals having a fiber morphology, a needle-like morphology, or a combination thereof, the method comprising:
crystallizing a reaction mixture comprising a source of water, a source of SiO 2 , a source of Al 2 O 3 , a source of an alkali metal, M, the alkali metal being Li, K, or a combination thereof, and a source of a structure directing agent in the form of an organic cation, Q, having the structure R 1 —R 3 —R 2 ,
the reaction mixture having a molar ratio of structure directing agent cation, Q, to SiO 2 in said reaction mixture of about 0.01 to about 0.05; a molar ratio of SiO 2 to Al 2 O 3 in said reaction mixture of about 50 to about 120; a molar ratio of water to SiO 2 in said reaction mixture of about 1 to about 500; a molar ratio of hydroxyl group concentration to SiO 2 in said reaction mixture is from about 0.1 to about 0.3; and a molar ratio of alkali metal, M, to SiO 2 in said reaction mixture is from about 0.05 to about 0.4,
where R 1 and R 2 are the same or different, R 1 and R 2 being tetraalkylammonium groups having the formula —N + —RR′R″,
where R, R′, and R″ are each the same or different, the R, R′, and R″ alkyl groups each being an alkyl group having from 1 to 10 carbons, and
where R 3 is a polymethylene group of formula (CH 2 ) n , where n=6.

2. The method of claim 1 , wherein R, R′, and R″ are methyl groups, ethyl groups, or combinations thereof.

3. The method of claim 1 , wherein R, R′, and R″ are alkyl groups containing 4 carbons or less.

4. The method of claim 1 , wherein the reaction mixture further comprises seeds of ZSM-48 in an amount such that a weight percent of seeds relative to total weight of SiO 2 in said reaction mixture is between about 0.1 wt % and about 20 wt %.

5. The method of claim 1 , wherein the reaction mixture has a molar ratio of structure directing agent cation, Q, to SiO 2 in said reaction mixture of about 0.015 to about 0.025 and a molar ratio of hydroxyl group concentration to SiO 2 in said reaction mixture of about 0.14 to about 0.18.

6. The method of claim 1 , wherein the alkali metal, M, comprises substantially no sodium.

7. The method of claim 1 , wherein the reaction mixture comprises substantially no intentionally added sodium.

8. The method of claim 1 , wherein at least 50 vol % of the as-synthesized ZSM-48 crystals have a fibrous morphology.

9. The method of claim 1 , wherein at least 50 vol % of the as-synthesized ZSM-48 crystals have a needle-like morphology.

10. A method of synthesizing ZSM-48 crystals, at least 25 vol % of the as-synthesized crystals having a fiber morphology, a needle-like morphology, or a combination thereof, the method comprising:
crystallizing a reaction mixture comprising a source of water, a source of SiO 2 , a source of Al 2 O 3 , a source of an alkali metal, M, the alkali metal being Li, K, or a combination thereof, and a source of a structure directing agent in the form of an organic cation, Q, having the structure R 1 —R 3 —R 2 ,
the reaction mixture having a molar ratio of structure directing agent cation, Q, to SiO 2 in said reaction mixture of 0.01 to 0.05; a molar ratio of SiO 2 to Al 2 O 3 in said reaction mixture of 50 to 120; a molar ratio of water to SiO 2 in said reaction mixture of 1 to 500; a molar ratio of hydroxyl group concentration to SiO 2 in said reaction mixture is from 0.1 to 0.3; and a molar ratio of alkali metal, M, to SiO 2 in said reaction mixture is from 0.05 to 0.4,
where R 1 and R 2 are the same or different, R 1 and R 2 being tetraalkylammonium groups having the formula —N + —RR′R″,
where R, R′, and R″ are each the same or different, the R, R′, and R″ alkyl groups each being an alkyl group containing 4 carbons or less, and
where R 3 is a polymethylene group of formula (CH 2 ) n , where n=6.

11. The method of claim 10 , wherein R, R′, and R″ are methyl groups, ethyl groups, or combinations thereof.

12. The method of claim 10 , wherein the reaction mixture further comprises seeds of ZSM-48 in an amount such that a weight percent of seeds relative to total weight of SiO 2 in said reaction mixture is between 0.1 wt % and 20 wt %.

13. The method of claim 10 , wherein the reaction mixture comprises substantially no intentionally added sodium.

14. The method of claim 10 , wherein at least 50 vol % of the as-synthesized ZSM-48 crystals have a fibrous morphology.

15. The method of claim 10 , wherein at least 50 vol % of the as-synthesized ZSM-48 crystals have a needle-like morphology.

Assignees

• Lai Wenyih Frank
• Exxonmobil Res & Eng Co

Inventors

• Lai Wenyih Frank

Classifications

• C01B39/48 Primary

  using at least one organic template directing agent · CPC title

• B01J29/703

  MRE-type, e.g. ZSM-48 · CPC title

• C01P2004/10

  extending in one dimension, e.g. needle-like · CPC title