Liquid purification or separation – Filter – Material
Reexamination Certificate
2001-02-21
2004-02-17
Walker, W. L. (Department: 1723)
Liquid purification or separation
Filter
Material
C210S500220, C210S509000, C264S045100, C264S045500, C502S064000, C502S078000
Reexamination Certificate
active
06692640
ABSTRACT:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT
The present invention is directed to an MOR zeolite membrane having mordenite zeolite crystals dominantly oriented in a specific crystalline direction on a porous substrate and a method for producing the membrane. Zeolite has a frame or matrix structure of crystalline aluminosilicate, which includes a mesh-like structure composed of fine pores having a minute and uniform diameter. Thus, zeolite is used as a molecular sieve or a catalyst.
For example, JP-A-7-330326 discloses a zeolite membrane which is formed on a single crystal substrate of an oxide, a semiconductor or a metal, and having crystals oriented in a specific crystalline direction. Zeolite membranes of the A type, Y type and Method for Producing the Same the like are disclosed in the examples in JP '326.
In addition, WO92/13631 discloses zeolite membranes including an oriented single crystal layer of ZSM-5 (MFI), an A type, a Y type, an X type and the like. WO97/25272 discloses an MFI zeolite membrane having crystals oriented along the b-axis and a method for producing the membrane. Further, WO96/01683 discloses an MFI zeolite membrane having crystals oriented along the a-axis and the c-axis and the method for producing the membrane.
However, a mordenite (MOR) zeolite membrane having crystals oriented in a specific crystalline direction has not yet been known. An MOR zeolite membrane is superior in acid resistance in comparison with other zeolite membranes, such as, for example, those of an A type, a Y type and the like. Thus, such an MOR zeolite membrane would be greatly desired and extremely useful in a wide variety of applications.
SUMMARY OF THE INVENTION
The present invention has been made in view of the problems associated with the prior art, and a goal of which is to provide an MOR zeolite membrane having crystals dominantly oriented in a specific crystallization direction and a method for producing the membrane. That is, according to the present invention, there is provided a mordenite (MOR) zeolite membrane formed on a porous substrate and having crystals dominantly oriented in a specific crystalline direction.
According to the present invention, there is further provided a method for producing a mordenite (MOR) zeolite membrane including the steps of:
immersing a porous substrate in a gel of raw material which contains zeolite constitution elements and contains 40-400 of SiO
2
/Al
2
O
3
in molar ratio, 10-120 of H
2
O/Na
2
O in a molar ratio, and 10-40 of H
2
O/SiO
2
in molar ratio; and
subjecting the gel in the presence of the porous substrate to a hydrothermal synthesis at 150° C. or more to crystallize the zeolite to form a membrane thereof.
In the above, it is preferable that the porous substrate is disposed in a reaction vessel so that a surface on which a membrane is formed becomes perpendicular, and that the gel of the raw material contains SiO
2
/Al
2
O
3
of 100-400 in molar ratio, H
2
O/Na
2
O of 10-100 in molar ratio, and H
2
O/SiO
2
of 10-30 in molar ratio.
REFERENCES:
patent: 5258339 (1993-11-01), Ma
patent: 5429743 (1995-07-01), Geus et al.
patent: 5871650 (1999-02-01), Lai
patent: 6197427 (2001-03-01), Anstett
patent: 06157025 (1994-06-01), None
patent: 7-330326 (1995-12-01), None
patent: 92/13631 (1992-08-01), None
patent: 96/01683 (1996-01-01), None
patent: 97/25272 (1997-07-01), None
Database WPI, Week 199427, Derwent Publications Ltd., London, GB; AN 1994-221551, XP002168517 & JP 06 157025 A(NOK Corp.), Jun. 3, 1994.
WO 97 33684 A (Exxon Chemical Patents Inc.) Sep. 18, 1997.
Yamazaki, Satoshi, et al., “Synthesis of a Mordenite Membrane on a Stainless-Steel Filter and Polytetrafluoroethylene Plate Substrates,” Microporous Materials, vol. 5, 1995, pp. 245-253.
Burr & Brown
Menon Krishnan S
NGK Insulators Ltd.
Walker W. L.
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