JPH0699044A - Zeolite membrane and production thereof - Google Patents

Abstract

PURPOSE:To obtain a zeolite membrane available as a functional separation membrane for efficiently and continuously separating alcohol or an organic material from an aq. alcoholic solution or an aq. solution in which the organic material is dissolved. CONSTITUTION:A high performance silicalite membrane is formed by hydrothermally synthesizing silicalite by using a water based gel solution having >=30H2O/SiO2 ratio as a starting material without stirring in a reaction vessel to densely and uniformly deposit a silicalite layer on a porous carrier placed on the bottom of the vessel. Thus, an alcohol selective separation membrane chemically and thermally stable, high in mechanical strength and remarkably large in separation coefft. is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to various separation membranes, and more particularly to a zeolite membrane which is useful as an organic permselective separation membrane and a method for producing the same.

[0002]

2. Description of the Related Art The pervaporation method is a process in which the permeate side of a membrane is evacuated for separation, and is a membrane separation method suitable for separating an organic solution. At present, utilization of a water-permeable membrane for dehydration of an alcohol solution is being studied, and research and development on a separation membrane material to be used are vigorously carried out.
By the way, the direction of recent research has been toward the synthesis of membranes that permeate substances of large molecular size, especially in the development of high-performance alcohol selective permeation type separation membranes, more generally organic matter selective permeation type separation membranes. Most attention. This is because it can be used not only for preferentially permeating and concentrating alcohol from a dilute aqueous alcohol solution of biomass, but also for removing and recovering organic substances from general wastewater and industrial waste liquid.

The separation membrane materials studied so far are mainly polymer membranes such as silicone rubber, polyethylene, and polyphenylene oxide-polydimethylsiloxane graft copolymer, and their separation performance is not yet practical. The development of high-performance organic permselective separation membrane materials has been strongly demanded.

Recently, studies have been conducted to apply zeolite to gas / liquid separation membranes. This utilizes the molecular level pores and properties of zeolite (heat resistance, chemical resistance, hydrophobicity, etc.). A group of Professor Smolders of Twente University (Netherlands) reported that a membrane composed of silicalite and silicone rubber acts as an alcohol permselective separation membrane, and that the separation coefficient increases with the amount of silicalite. (J. Membra
ne Scienec, vol. 35, p. 39). However, this film is only one in which silicalite crystals are embedded in silicone rubber, and naturally there is a limit to the amount of silicalite to be blended. Therefore, separation is not limited to silicalite crystals,
It is also done through silicone rubber, so there is a natural limit to the separation performance.

On the other hand, a method for synthesizing a zeolite membrane on a porous inorganic oxide carrier such as glass or alumina has been disclosed (Japanese Patent Laid-Open Nos. 59-23136 and 63-63).
291809, U.S. Pat. No. 4,800,187 19
However, all of them had drawbacks such as defects (pinholes) in the film and uneven film thickness. This is probably because of the agitation during the synthesis of the zeolite membrane and the high concentration of the starting aqueous gel. In addition, although these membranes have been evaluated for their performance as gas separation membranes,
The separation performance is not practical. further,
The performance of the organic permselective separation membrane has not been evaluated at all.

By the way, the inventors of the present invention have previously proposed to easily synthesize a membrane composed of zeolite crystals alone without using a porous carrier or the like (Japanese Patent Application No. 3-12000).
1). Although this membrane is a membrane formed of zeolite crystals alone, it has problems for use as a separation membrane due to the presence of grain boundaries, weak connections between zeolite crystals, and weak mechanical strength. It was

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a separation membrane, particularly a zeolite membrane useful as an organic permeation type separation membrane and a method for producing the same.

[0008]

The present inventors have completed the present invention as a result of intensive studies to solve the above problems. That is, according to the present invention, there is provided a zeolite membrane made of zeolite that has crystal grown as an integral membrane having no grain interface. Further, according to the present invention, a zeolite skeleton metal source, an alkali metal source, and water are used, and the ratio of water per mol of the zeolite skeleton metal source is 30 to 1.
A carrier is contacted with an aqueous gel mixture of 000 moles and the aqueous gel mixture is heated without causing turbulence to form a zeolite film on the carrier, which has crystal growth in the form of an integral film without particle interfaces. A method for producing a zeolite membrane is provided.

Examples of the zeolite skeleton metal source used in the present invention include various metal sources used in conventional zeolite production, such as alumina, silica, titania, and galleries. These are used alone or in combination of two or more. As the alkali metal source, sodium hydroxide, potassium hydroxide, cesium hydroxide or the like is used.

The aqueous gel mixture used as the zeolite membrane raw material in the present invention is prepared by uniformly stirring and mixing the zeolite skeleton metal source, the alkali metal source and water. The ratio of the zeolite skeleton metal source to water is 30 to 1000 mol of water, preferably 40 to 200 mol, relative to 1 mol of the zeolite skeleton metal source. The ratio of the zeolite skeleton metal source to the alkali metal source is 0.01 mol with respect to 1 mol of the zeolite skeleton metal source.
The ratio is ˜0.3 mol, preferably 0.1˜0.15 mol.

If necessary, a crystallization accelerator can be added to the aqueous gel mixture. As the crystallization accelerator, it is possible to add one which has been used in the conventional production of zeolite, such as tetrapropylammonium bromide or tetrabutylammonium bromide. The addition ratio of the crystallization agent is 0.05 to 0.2 mol, preferably 0.1 to 0.15 mol, based on 1 mol of the zeolite skeleton metal source.

In the present invention, the carrier is brought into contact with the aqueous gel mixture obtained as described above, and the mixture is heated without causing turbulent flow. As a method of contacting the aqueous gel mixture with the carrier, in addition to the method of allowing the carrier to exist in the aqueous gel mixture, a method of forming a part or all of the reaction vessel from a carrier material and filling the vessel with the aqueous gel mixture, etc. There is. As a method for heating the aqueous gel mixture, there are a method of heating the outer wall of the reaction vessel filled with the aqueous gel mixture, a method of allowing a heating source to exist in the aqueous mixture, and the like. The heating temperature of the aqueous gel mixture is the temperature required for the hydrothermal synthesis of the desired zeolite, and is generally 80 to 250 ° C, preferably 100 to 200 ° C.

Any carrier can be used as long as it is formed of a material that can stably exist at the heating temperature. Examples of such carrier materials include metals, alloys, ceramics, plastics and the like. The shape of the carrier may be any shape as long as zeolite can be deposited and grown in a film form on the surface thereof, such as a film form, a plate form, a cylinder form, a pellet form, a particle form, a hollow system form, and a woven fabric. It may have various shapes such as a shape, a non-woven shape, and a paper shape.

When the zeolite is deposited from the aqueous gel mixture on the surface of the support, it is necessary that the aqueous gel mixture is free of turbulence. Of course, a slow flow of the mixture that does not cause turbulent flow is preferable from the viewpoint of increasing the precipitation rate of zeolite on the carrier, and can be adopted as necessary. When vigorous agitation that causes turbulent flow is performed, precipitation and growth of zeolite crystals occur in the mixture, zeolite particles are produced, and the zeolite particles become deposited and fixed on the carrier, which is advantageous. The resulting zeolite membrane has a particle interface, a large porosity, and a low mechanical strength. On the other hand, when heating the aqueous gel mixture without causing turbulent flow, the precipitation of the zeolite in the mixture is prevented, the precipitation of the zeolite selectively on the carrier, the growth occurs, the resulting zeolite membrane is a particulate zeolite It has a high mechanical strength and is substantially free of The thickness of the zeolite membrane formed on the carrier is 30 μm or more, preferably 200 to 500 μm. The thickness of the zeolite membrane on the carrier can be adjusted by the heating time (reaction time), and by lengthening the heating time, a zeolite membrane having a large film thickness can be obtained.

The zeolite membrane according to the present invention is obtained in the form of being fixed and immobilized on a carrier. In this case, when a plastic, for example, Teflon or the like having a weak adherence to the zeolite membrane is used as the carrier, the zeolite membrane can be peeled from the carrier to obtain a single zeolite membrane having no carrier. Also, graphite and carbon,
When a flammable carrier such as plastic is used, the carrier can be removed from the zeolite membrane by incineration to form a single zeolite membrane.

The zeolite membrane fixed on the carrier obtained by the present invention can be directly used as a product zeolite membrane when a porous carrier that allows gas or liquid to pass therethrough is used as the carrier. In this case, any porous carrier may be used as long as it has a pore size of 1 μm or more, usually about 2 to 40 μm. From the viewpoint of mechanical strength and heat resistance, in addition to ceramics such as alumina, mullite and cordierite, porous stainless steel,
Porous glass or the like is preferably used.

[0017]

EFFECT OF THE INVENTION The zeolite membrane of the present invention is dense, has high mechanical strength, and has a porous structure, and can be advantageously used as an adsorbent, a catalyst carrier, a separation membrane and the like. The zeolite membrane of the present invention can be advantageously used as an organic permeation type separation membrane. In this case, the hydrophobic silicalite membrane obtained by using silica as the zeolite skeleton metal source is an organic material that is dissolved in an aqueous solution, for example, an extremely improved performance in selectively separating and separating alcohol. It is suitable as an alcohol-selective separation membrane.

[0018]

EXAMPLES The present invention will be described in more detail below with reference to examples.

EXAMPLE 1 TPABr (tetrapropylammmoinium bromid) was added to an aqueous solution containing colloidal silica (catalyzed Cataloid SI-30).
e), NaOH was added and stirred uniformly to prepare a hydrated gel. The composition of the gel is 0.1TPABr-0.05Na ₂ O-
It was _{(70~1000) H 2 O - SiO} 2.

This gel composition was treated with porous stainless steel (SU) under the conditions of a reaction temperature of 170 ° C. and a crystallization time of 48 hours.
S) Hydrothermal treatment was carried out using a 300 ml autoclave in the presence of a disc (diameter 5 cm, pore size 2-40 microns) to obtain a SUS plate-supporting silicalite membrane.

FIG. 1 shows the results of thin film X-ray diffraction of the obtained film and line analysis of Si by EDX-SEM. Only the diffraction pattern of silicalite was observed in the X-ray diffraction pattern, and the SUS peak of the carrier was not detected. The silicalite film thickness was about 460 microns. These facts indicate that the silicalite film is formed relatively densely on the SUS carrier.

Example 2 A film was formed in the same manner as in Example 1 except that an alumina plate (Nikkato, material number F, apparent porosity 43%) was used as the porous carrier. FIG. 2 shows the results of thin film X-ray diffraction of the obtained film and line analysis of Si by EDX-SEM. The thickness of the silicalite layer was about 60 microns.

Example 3 The pervaporation characteristics of the membrane prepared in Example 1 above were measured.
The result is shown in FIG. This membrane has a pervaporation property at 60 ° C with a separation coefficient α (EtOH / H2O) = 60 and a membrane permeation flux Q.
= 0.76 kg / m ² · h, showing extremely high alcohol-selective separation performance. This value is the highest value ever reported.

Example 4 A hydrated gel was prepared in the same manner as in Example 1 except that fine particle alumina (average particle size: about 60 μm) was used together with colloidal silica. The composition of this gel is 0.
_{1TPABr-0.05Na 2 O-0.005Al 2} O 3
- (70-1000) was H ₂ O. Using this gel composition, a SUS plate-supported zeolite (crystalline aluminosilicate) film was obtained in the same manner as in Example 1. The thickness of this film was about 400 μm.

Comparative Example 4 An experiment was conducted in the same manner as in Example 1 except that the gel composition was stirred to cause turbulent flow in the gel composition.
In this case, no silicalite film was formed on the SUS carrier.

[Brief description of drawings]

FIG. 1 is a diagram showing a thin film X-ray diffraction diagram and a SEM image of a cross section of a SUS plate-supporting silicalite film according to the present invention. (A) Thin film X-ray diffraction diagram (a) SUS plate-supporting silicalite film (b) SUS plate (B) SEM image of cross section

FIG. 2 is a diagram showing a thin film X-ray diffraction diagram and an SEM image of a cross section of an alumina plate-supported silicalite film according to the present invention. (A) Thin film X-ray diffraction diagram (a) Alumina plate-supporting silicalite film (b) Alumina plate (B) SEM image of cross section

FIG. 3 is a diagram showing pervaporation characteristics of a SUS plate-supported silicalite membrane according to the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Dai Kitamoto, 1-1 East Higashi, Tsukuba, Ibaraki Industrial Technology Institute, Institute of Chemical Research (72) Inventor, Kaido Kiyozumi, 1-1, Higashi, Tsukuba, Ibaraki Industrial Technology In the laboratory

Claims (5)

[Claims] 1. A zeolite membrane made of zeolite which is crystal-grown into an integral membrane having no grain interface. 2. The zeolite membrane according to claim 1, wherein the zeolite is silicalite. 3. The method according to claim 1, which is fixed on a porous carrier.
Or the zeolite membrane of 2. 4. An organic permselective separation membrane comprising the zeolite membrane according to claim 1. 5. A carrier is brought into contact with an aqueous gel mixture consisting of a zeolite skeleton metal source, an alkali metal source and water, and the ratio of water per mol of the zeolite skeleton metal source is 30 to 1000 mol, and the carrier is contacted with the aqueous gel mixture. A method for producing a zeolite membrane, which comprises heating the gel mixture without causing turbulent flow to form a zeolite membrane crystal-grown in the form of an integral membrane having no particle interface on the carrier.