JP7844997B2 - Method for manufacturing zeolite membranes - Google Patents

Description

This invention relates to a method for producing zeolite films.

Zeolite membranes are used as separation membranes to separate and remove water from aqueous solutions of organic compounds. A known method for producing zeolite membranes involves hydrothermal synthesis without the use of an organic template, in the presence of a seed crystal (see, for example, Patent Document 1). This method eliminates the need for a calcination step to remove the organic template after film formation, thus yielding an uncalcined zeolite membrane.

International Publication No. 2015/159986

However, in the conventional techniques described above, when separating and removing water-soluble organic compounds by contacting an aqueous solution containing water-soluble organic compounds with a zeolite membrane and allowing water to permeate, the inventors have found that a large amount of water-soluble organic compounds may permeate along with the water being separated. Specifically, in membrane separation using the molecular sieving effect of a zeolite separation membrane to separate a mixture of relatively permeable and relatively impermeable components by allowing the relatively permeable component to pass through, the inventors have found that a large amount of the relatively impermeable component may permeate. Thus, when the amount of the relatively impermeable component accompanying the separation increases, the separation efficiency decreases.

One aspect of the present invention aims to realize a zeolite membrane capable of reducing the amount of relatively permeable components in a mixture during separation of the mixture by molecular sieving effect using an untreated zeolite membrane.

To solve the above problems, a method for producing a zeolite film according to one aspect of the present invention includes a step of contacting an uncalcined zeolite film with a dehydration condensation reaction accelerator.

According to one aspect of the present invention, in the separation of a mixture by molecular sieving effect using an untreated zeolite membrane, it is possible to realize a zeolite membrane capable of reducing the amount of relatively low permeability components transmitted from the mixture.

This diagram schematically shows the configuration of the apparatus used in the pervaporation method with an uncalcined zeolite film in the example.

An embodiment of the present invention will be described below.

[Contact process]
A method for producing a zeolite film according to one aspect of the present invention includes a step of contacting an untreated zeolite film with a dehydration condensation reaction accelerator (hereinafter also referred to as the "contact step"). In the contact step, contacting the untreated zeolite film with the dehydration condensation reaction accelerator means applying the dehydration condensation reaction accelerator to at least the surface of the untreated zeolite film. This contact can be carried out by passing the dehydration condensation reaction accelerator through the untreated zeolite (e.g., by passing liquid or air through it), or by immersing the untreated zeolite in the dehydration condensation reaction accelerator or by flowing the dehydration condensation reaction accelerator down the surface of the untreated zeolite.

[Untreated zeolite membrane]
An untreated zeolite film in one aspect of the present invention is a zeolite film that has not undergone a treatment process. The treatment process is a process in which, after the process, the amount of relatively low permeability components that permeate the zeolite film is reduced compared to before the process. Specifically, it is a process of performing one or more operations such as heating, calcination, surface treatment, and contact with a dehydration condensation reaction accelerator. Although the detailed mechanism is speculative, it is thought that the amorphous portion contained in the untreated zeolite film reacts, reducing the amount of relatively low permeability components that pass through the amorphous portion.

Heating is a process of heating the zeolite membrane to a temperature that satisfies the conditions of the aforementioned steps. The heating temperature is 120°C or higher, preferably 150°C or higher, and more preferably 200°C or higher. From the viewpoint of preventing damage due to the difference in thermal expansion coefficient between the separation membrane and the substrate (support), the temperature is preferably 900°C or lower, more preferably 850°C or lower, even more preferably 800°C or lower, particularly preferably 750°C or lower, and most preferably 500°C or lower.

Firing involves heating the zeolite film to a temperature at which the organic template agent, when synthesized using an organic template agent, is thermally decomposed to a size that allows it to pass through the pores of the zeolite, thereby removing it. From the viewpoint of sufficiently removing the organic template agent, the firing temperature is preferably 350°C or higher, more preferably 400°C or higher, even more preferably 430°C or higher, and particularly preferably 450°C or higher. From the viewpoint of preventing fracture due to the difference in thermal expansion coefficient between the separation membrane and the substrate (support), the temperature is preferably 900°C or lower, more preferably 850°C or lower, even more preferably 800°C or lower, particularly preferably 750°C or lower, and most preferably 500°C or lower. The firing time is preferably 24 hours or more from the viewpoint of sufficiently removing the organic template agent, and preferably 72 hours or less from the viewpoint of productivity. Surface treatment is treatment with a compound such as a silane coupling agent.

The untreated zeolite film may be a manufactured product or a commercially available product. A manufactured untreated zeolite film is, for example, a zeolite film synthesized without using an organic template that restricts the zeolite's crystal structure, and which has not been calcined. Alternatively, a manufactured untreated zeolite film may be a zeolite film synthesized using an organic template, with the organic template removed by an oxidizing agent, and which has not been calcined. The untreated zeolite film can be produced by hydrothermal synthesis, and more specifically, by the method described in, for example, Patent Document 1.

Contact with the dehydration condensation reaction accelerator is described below.

The crystal structure of the untreated zeolite film is not limited and can be appropriately selected from various known structures. Examples of such crystal structures include chabasite (CHA), faujasite (FAU), and type A (LTA), MFI, MER, MOR, EMT, SOD, CAN, JBW, HEU, BRE, ABW, ANA, BEA, MTW, NES, LEV, MAZ, MEL, MSE, MTT, MTW, PAU, RTH, SZR, TON, and VET. The untreated zeolite film can generally be produced by hydrothermal synthesis, for example, by the method described in Patent Document 1 mentioned above.

The cations used in hydrothermal synthesis are not limited. Examples of cations include K ⁺ , Na ⁺ , Li ⁺ , Rb ⁺ , Cs ⁺ , ^Sr²⁺ , and ^Ca²⁺ .

The untreated zeolite film may contain K ⁺ , Na ⁺ , Li ⁺ , Rb ⁺ , Cs ⁺ , Sr2 ⁺ , and Ca2 ⁺ as countercations in the amorphous portion. These countercations are located near _AlO2- in the ^amorphous portion. When ^K+ , Na ⁺ , Li ⁺ , Rb ⁺ , Cs ⁺ , Sr2 ⁺ , and Ca2 ⁺ are included as countercations, they may be incorporated into the untreated zeolite film by using K ⁺ , Na ⁺ , Li ⁺ , Rb ⁺ , Cs ⁺ , Sr2 ⁺ , and Ca2 ⁺ as cations during hydrothermal synthesis, or by performing cation exchange after hydrothermal synthesis.

[Dehydration condensation reaction accelerator]
In one aspect of the present invention, the dehydration condensation reaction accelerator is a component that promotes the dehydration condensation reaction in an untreated zeolite membrane. The dehydration condensation reaction in an untreated zeolite membrane will be described later. The dehydration condensation reaction accelerator can be in any form that allows for sufficient contact with the untreated zeolite membrane. Examples of forms of the dehydration condensation reaction accelerator include liquids, gases, solutions, and supercritical fluids. By bringing the dehydration condensation reaction accelerator into contact with the untreated zeolite membrane, the amount of water-soluble organic compounds that permeate through the untreated zeolite membrane when it is used for the concentration of water-soluble organic compounds can be reduced.

Ethanol is a specific example of a dehydration condensation reaction accelerator. Ethanol may be used in aqueous solution. When using an aqueous ethanol solution as a dehydration condensation reaction accelerator, the ethanol content in the aqueous solution is preferably 90% by volume or more, more preferably 95% by volume or more, and even more preferably 97% by volume or more, from the viewpoint of sufficiently reducing the amount of water-soluble organic compounds that permeate the untreated zeolite membrane.

The temperature at which ethanol is used as a dehydration condensation reaction accelerator can be appropriately determined within a range that allows sufficient treatment of the untreated zeolite film by contact. From the viewpoint of shortening the treatment time during the contact step of the untreated zeolite film, the temperature of the ethanol used as a dehydration condensation reaction accelerator is preferably 25°C or higher, more preferably 50°C or higher, even more preferably 75°C or higher, particularly preferably 90°C or higher, and most preferably 100°C or higher. Furthermore, from the viewpoint of suppressing thermal decomposition of the untreated zeolite film, the temperature of the ethanol is preferably 135°C or lower, more preferably 130°C or lower, and even more preferably 120°C or lower. The above temperature ranges are defined as temperatures under conditions of atmospheric pressure or higher.

Another specific example of a dehydration condensation reaction accelerator is carbon dioxide. Carbon dioxide can be used in a fluid state and is preferably used as a gas or supercritical fluid. When using carbon dioxide as a dehydration condensation reaction accelerator, the conditions can be appropriately determined from the range that allows sufficient treatment of the untreated zeolite film by contact and the state of the carbon dioxide. For example, when carbon dioxide is a gas, it is preferable to use dry carbon dioxide, and it is preferable to use commercially available dry gas. From the above viewpoint, the temperature of the carbon dioxide should be above dry room temperature, and is preferably 100°C or higher. Using heated carbon dioxide is preferable because, although this is hypothetical, it increases the rate of the dehydration condensation reaction of the silanol groups of the amorphous portion or the dissociated silanol groups, and it eliminates the need for an additional drying step. In particular, when a potassium salt is used as the base when synthesizing the zeolite, the potassium carbonate produced by the reaction with carbon dioxide has low water solubility, so it is preferable to increase the reaction rate to rapidly increase the concentration of potassium carbonate and exceed the saturation concentration earlier. Furthermore, if carbon dioxide is a supercritical fluid, the temperature and pressure should be above the critical point. From the viewpoint of simplifying the equipment, it is preferable to use carbon dioxide as a gas, and its pressure should preferably be less than 1 MPa. Alternatively, carbon dioxide may be used as a mixed gas with a gas inert to the untreated zeolite membrane, such as nitrogen.

The dehydration condensation reaction accelerator can also be determined based on the type of countercation present in the amorphous portion of the untreated zeolite membrane. In this case, the dehydration condensation reaction accelerator can be selected to produce a salt that reacts with the countercation to form a salt that is poorly soluble in water, or a salt that is a stronger acid than silicic acid.

For example, NaF and sodium urate are examples of salts that are poorly soluble in water. Therefore, when the countercation is Na ⁺ , using a dehydration condensation reaction accelerator that forms NaF or sodium urate makes it easier to carry out an irreversible dehydration condensation reaction and maintain a state in which the permeatement of water-soluble organic compounds is reduced. Another specific example of a dehydration condensation reaction accelerator is a fluoride solution or a fluorocomplex solution. Examples of fluoride solutions or fluorocomplex solutions include aqueous solutions of fluoride or aqueous solutions of fluorocomplexes. An example of a compound containing a fluorocomplex _{is Na₂SiF₆} . The amount of fluoride used and the applicable temperature may also be appropriately determined from the above viewpoint. When using _Na₂SiF₆ , the zeolite film is immersed in a saturated aqueous _solution of _Na₂SiF₆ at room temperature for a certain period of time _, and then dried.

Furthermore, when the countercation is Na ⁺ , uric acid solution can be used as another specific example of a dehydration condensation reaction accelerator. The concentration and application temperature of the uric acid solution may be determined appropriately from the standpoint of ensuring sufficient treatment of the untreated zeolite membrane by contact. When using uric acid solution, the zeolite membrane is immersed in a saturated aqueous solution of uric acid with warm water for a certain period of time, and then heated and dried.

[Other processes]
A method for producing a zeolite film according to one aspect of the present invention may further include other steps besides the contact step described above, to the extent that the effects of the present invention can be obtained. An example of other steps is a step of growing zeolite crystals by hydrothermal synthesis to produce an untreated zeolite film (hereinafter also referred to as the "production step").

[Generation process]
The production process can be carried out by known methods for producing the aforementioned untreated zeolite film. The production process may be carried out prior to the aforementioned contact process. Examples of the production process include a step of growing zeolite crystals without using an organic template compound to produce an untreated zeolite film, and a step of growing zeolite crystals in the presence of an organic template compound, and then treating the resulting zeolite film with an oxidizing agent to remove the organic template compound from the zeolite film to produce an untreated zeolite film. The former can be carried out by a method such as that described in Patent Document 1 mentioned above. The latter can be carried out by a method such as that described in "Microporous and Mesoporous Materials 2005, 87, 45-51."

The above-mentioned organic template compounds are organic compounds that act as templates for regulating the crystal structure of zeolites. When using organic template compounds in the production process, they can be appropriately selected from compounds known as templates in the production of zeolite films, depending on the desired crystal structure of the zeolite film. Examples of organic template compounds include organic amines, and more specifically, N,N,N-trimethylammonium compounds, N,N,N-tripropylammonium compounds, and N,N,N-trimethyladamantanammonium compounds.

Furthermore, the oxidizing agent used to treat the organic template compound is a component that acts on the organic template compound in the crystal structure of the zeolite film, decomposing the compound and making it removable from the zeolite film. The oxidizing agent can be appropriately selected from components known to decompose the organic template compound in the crystal structure of the zeolite film during its production. Examples of oxidizing agents include ozone and atomic oxygen obtained by irradiating ozone with ultraviolet light. The conditions for using the oxidizing agent should be such that the dehydration condensation reaction of the silanol group does not proceed completely.

[Consideration]
According to a manufacturing method in one aspect of the present invention, an untreated zeolite membrane can be obtained that reduces the amount of water permeate from an aqueous solution of a water-soluble organic compound when separating and removing water from the aqueous solution using the untreated zeolite membrane. The reason for this is not entirely clear, but it is thought to be as follows.

In hydrothermal synthesis, the reaction does not proceed until amorphous moieties grow within the zeolite membrane to form a zeolite cage. Unreacted regions (Si-OK if the T atom is Si and the countercation is K ⁺ , with the T atom being the central atom of the tetrahedral substructure in the zeolite skeleton) remain within the zeolite membrane, and these unreacted regions are thought to become pathways for organic compounds during subsequent use.

In one aspect of the present invention, in the aforementioned contact step, a dehydration condensation reaction accelerator is brought into contact with the untreated zeolite film. Since the permeation of water-soluble organic compounds is suppressed by contact with the dehydration condensation reaction accelerator, it is considered that the reaction proceeds in the rightward direction, as shown in the following equation, during the contact step.

Thus, it is thought that in the unreacted region, the silanol group becomes a siloxane bond through dehydration condensation. Since the siloxane bond site cannot serve as a channel for the water-soluble organic compound, the amount of water-soluble organic compound permeating through it is thought to be reduced.

It is thought that because ethanol has a low dielectric constant, the stability of the silanol group is higher than that of the Si-OK group, and that ethanol absorbs water to form a siloxane bond.

It is believed that carbon dioxide reacts in the untreated zeolite membrane in a similar manner to how iron molds are made, where water glass and sand are mixed and carbon dioxide gas is blown in to solidify them. Specifically, it is thought that when carbon dioxide comes into contact with the untreated zeolite membrane, it neutralizes the weakly basic Si-OK group as carbonic acid, forming a weaker basic silanol group with potassium carbonate, resulting in the reaction proceeding to the right in the above reaction equation.

It is thought that the fluoride solution reacts in the untreated zeolite film in a similar manner to when _NaSiF6 is used to cure water glass as an adhesive, generating a countercation salt, similar to carbon dioxide, and allowing the reaction to proceed from right to left in the above reaction equation. Furthermore, if the countercation is Na ⁺ , it is thought that an insoluble salt is formed with the countercation, making the above reaction irreversible.

It is thought that uric acid solution, like carbon dioxide and fluoride solutions, generates a salt of the countercation, thus allowing the reaction to proceed to the right in the above reaction equation. Furthermore, it is thought that urine spray, like fluoride solutions, forms an insoluble salt with the countercation when the countercation is Na ⁺ , thus preventing the reaction to proceed to the left in the above reaction equation.

〔summary〕
As is clear from the above description, a method for producing a zeolite membrane according to one aspect of the present invention includes a step of contacting an untreated zeolite membrane with a dehydration condensation reaction accelerator. Therefore, according to one aspect of the present invention, a zeolite membrane capable of reducing the permeation of water-soluble organic compounds can be realized when separating and removing water from an aqueous solution of a water-soluble organic compound using an untreated zeolite membrane.

In one embodiment of the present invention, ethanol may be used as the dehydration condensation reaction accelerator. This configuration is even more effective from the viewpoint of easily preventing the permeation of organic compounds.

In one embodiment of the present invention, an aqueous ethanol solution containing 95% by volume or more of ethanol may be used as the dehydration condensation reaction accelerator. This volume percentage is the value at 20°C. If it is 95% by mass or more, it means 95% by volume or more. This configuration is even more effective from the viewpoint of sufficiently preventing the permeation of water-soluble organic compounds through the zeolite membrane and from the viewpoint of enabling the separation membrane that has undergone the dehydration condensation reaction to be used in fields requiring safety, such as food applications.

When ethanol is used as the dehydration condensation reaction accelerator, the temperature of the accelerator may be 25°C or higher. This configuration is even more effective in shortening the contact process time and increasing productivity.

When ethanol is used as a dehydration condensation reaction accelerator, the temperature of the accelerator may be 120°C or lower. This configuration is even more effective from the standpoint of accelerating the reaction and being economical.

In one embodiment of the present invention, carbon dioxide may be used as the dehydration condensation reaction accelerator. This configuration is even more effective in sufficiently preventing the permeation of water-soluble organic compounds through the zeolite membrane.

When carbon dioxide is used as a dehydration condensation reaction accelerator, the carbon dioxide may be in gaseous form. This configuration is even more effective because it easily prevents the permeation of water-soluble organic compounds, simplifies the equipment by eliminating the use of flammable materials in the process, and allows the manufactured separation membrane to be used in fields requiring safety, such as food applications.

When carbon dioxide is used as a dehydration condensation reaction accelerator, the carbon dioxide may be in a supercritical state. This configuration is expected to improve both the diffusion and action of carbon dioxide, making it even more effective from the standpoint of improving the effects of the aforementioned contact process and increasing productivity by shortening the contact process time.

In one embodiment of the present invention, the process further includes a step of growing zeolite crystals by hydrothermal synthesis to produce an untreated zeolite film prior to the contact step, wherein the untreated zeolite film contains Na ⁺ or K ⁺ as a countercation, and in the contact step, a compound that forms a water-insoluble salt with the countercation may be used as a dehydration condensation reaction accelerator. This configuration is expected to prevent the reconfiguration of the flow channels of organic compounds, and is therefore even more effective in suppressing the unintended permeation of water-soluble organic compounds when using the untreated zeolite film.

In the case where the generation step is further included and the countercation is Na ⁺ , a fluoride solution may be used as the dehydration condensation reaction accelerator, or uric acid solution may be used as the dehydration condensation reaction accelerator. This configuration is even more effective in suppressing the unintended permeation of water-soluble organic compounds when using the untreated zeolite membrane in the above case.

If the process further includes a production step, the production step may be a step of growing zeolite crystals without using an organic template compound, which is a template agent that regulates the crystal structure of the zeolite, in order to produce an untreated zeolite film. Alternatively, if the process further includes a production step, the production step may be a step of growing zeolite crystals in the presence of an organic template compound, which is a template agent that regulates the crystal structure of the zeolite, and then treating the resulting zeolite film with an oxidizing agent to remove the organic template compound from the film and produce an untreated zeolite film. This configuration, since it does not require calcination, is even more effective than methods for producing zeolite films that require calcination, from the standpoint of increasing the productivity of zeolite films and saving labor.

In one aspect of the present invention, an untreated zeolite film is obtained in which the change in the permeate amount of water-soluble organic compounds is reduced. Therefore, one aspect of the present invention is expected to contribute to the widespread adoption and development of technologies using zeolite films, and to contribute to the achievement of the Sustainable Development Goals (SDGs) related to industry and technological innovation.

The present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included within the technical scope of the present invention.

The present invention will be described in more detail by examples, but the present invention is not limited to the following examples unless it exceeds the essence of the invention.

In the following examples, the particle size distribution, air permeability, and vaporization performance of the seed crystals were measured using the following methods.

The dispersion for measuring the particle size distribution of seed crystals was prepared by adding water to the ultrasonic dispersion bath of the measuring device, stirring it with a stirrer, circulating the dispersion through a flow cell, and adding seed crystals to the water in the ultrasonic dispersion bath until the intensity of the light transmitted through the dispersion fell within the appropriate light intensity range displayed on the device. Typically, the amount of water used as the dispersion solvent was 250 mL, and the amount of seed crystal dispersed was typically 0.01 g. When using powdered seed crystals, the dispersion was subjected to ultrasonic waves for 5 minutes to remove aggregated seed crystals before measurement. Measurements were performed using a flow method.
From the obtained data, the primary particle values D10, D50, and D90 were acquired.

[Measurement of secondary particle size]
The secondary particle size of the seed crystal was measured under the following conditions.
• Device name: ELSZ-2000ZS (manufactured by Otsuka Electronics Co., Ltd.)
• Measurement method: Dynamic light scattering method • Measurement range: 0.02 to 44.3 μm
• Light source: High-power semiconductor laser • Detector: High-sensitivity APD
• Dispersion solvent: Water. The median diameter of the secondary particle size was obtained from the acquired data.

[Air permeability]
A cylindrical porous support-zeolite membrane composite, in which an untreated zeolite membrane is supported on the surface of a porous support, was sealed at one end, and the other end was connected to a 5 kPa vacuum line in a sealed state. The airflow rate was measured using a mass flow meter placed between the vacuum line and the porous support-zeolite membrane composite, and the air permeability was expressed as [L/( ^m² ·h)]. A KOFLOC 8300 mass flow meter for _N2 gas with a maximum flow rate of 500 mL/min (at 20°C and 1 atm) was used as the mass flow meter. When the KOFLOC 8300 mass flow meter reading was 10 mL/min (at 20°C and 1 atm) or less, a Lintec MM-2100M mass flow meter for air gas with a maximum flow rate of 20 mL/min (at 0°C and 1 atm) was used for measurement.

[Pervaporation performance measurement]
Performance measurements using a porous support-zeolite membrane composite by pervaporation were performed under the following conditions, by selectively permeating water from a 100°C water/ethanol aqueous solution (5/95 mass%) which was the liquid to be treated.

A schematic diagram of the apparatus used in the pervaporation method is shown in Figure 1. As shown in Figure 1, the apparatus comprises a raw material tank 1 containing an aqueous solution of organic compounds as raw materials, a membrane module 2 containing a porous support-zeolite membrane composite, and a vacuum pump 3 connected to the membrane module 2. A measuring trap 4 is connected between the membrane module 2 and the vacuum pump 3.

The membrane module 2 comprises a metal cylinder, a connecting member connected to one end of the cylinder (the side facing the measurement trap 4), and a sealing member that can be opened and closed to seal the other end of the cylinder. The membrane module 2 houses a porous support-zeolite membrane composite. One end of the porous support-zeolite membrane composite is connected to the connecting member, and the inner circumferential space of the porous support-zeolite membrane composite is isolated from the outer circumferential space of the porous support-zeolite membrane composite, while communicating with the measurement trap 4 via the connecting member. The other end of the porous support-zeolite membrane composite is sealed.

The raw material tank 1 is configured to supply raw materials to the membrane module 2 via the supply tank 5 and the heater 6. Furthermore, the raw materials within the membrane module 2 are configured to be returned to the supply tank 5 or to the raw material tank 1 via the cooler 7. The raw materials are also configured to circulate between the supply tank 5 and the heater 6. Additionally, the raw materials returned from the cooler 7 to the raw material tank 1 are configured to be sampled. Pumps P1, P2, and valves V1 to V12 are appropriately arranged in the flow path of the apparatus.

[Example of manufacturing a porous support-zeolite membrane composite]
37.6 g of aluminum hydroxide (containing 53.5% by mass _{of Al₂O₃} , manufactured by Aldrich), 243.0 g of 25 wt% KOH aqueous solution, and 1910.2 g of water were added and mixed and stirred to dissolve the mixture. 232.5 g of colloidal silica (Nissan Chemical Snowtec-40) was added to this and stirred for 2 hours to obtain an aqueous reaction mixture. The composition (molar ratio) of this aqueous reaction mixture was _SiO₂ / _Al₂O₃ / _KOH / _H₂O = 1/0.125/0.7/80/ and _SiO₂ / _Al₂O₃ = ₈ .

As the inorganic porous support, a porous alumina tube (outer diameter 12 mm, inner diameter 9 mm, length 1200 mm) was used. The average pore size of this porous alumina tube was 1.3 μm, and the porosity was 42%.

FAU-type zeolite was obtained by mixing 10.0 g of proton-type Y-type zeolite (HY (SAR=5), manufactured by Shokubai Kasei Kogyo Co., Ltd.) with 5.00 g of NaOH and 100 g of water, heating the mixture at 100°C for 7 days, and then filtering, washing with water, and drying. When the volume-based particle size distribution of this FAU-type zeolite was measured, the _D50 was 1.73 μm, with maximum values of 1.32 μm and 2.98 μm (particle size: approximately 2 μm).

This FAU-type zeolite was used as a seed crystal, and the above support was immersed in a solution of 2% by mass of this seed crystal dispersed in water for a predetermined time, and then dried at 100°C for more than 5 hours to allow the seed crystal to adhere. The mass of the attached seed crystal was 3 g/ ^m² .

A support with attached seed crystals was immersed vertically in a 200 ml Teflon® inner cylinder containing the aqueous reaction mixture. The autoclave was sealed and heated from room temperature to 180°C over 5 hours. After heating was complete, the autoclave was heated at 180°C for 24 hours under self-sustaining pressure. After the predetermined time, it was allowed to cool, and the porous support-zeolite membrane composite was removed from the aqueous reaction mixture. After washing, it was dried at 100°C for 4 hours. Thus, a porous support-zeolite membrane composite was obtained, in which an untreated CHA-type zeolite membrane was supported on the outer surface of the porous support.

[Contrastive Example]
A permeation vaporization performance test was conducted on the porous support-zeolite membrane composite obtained in the above manufacturing example. The "porous support-zeolite membrane composite obtained in the above manufacturing example" corresponds to an untreated zeolite membrane that has not been "contacted with a dehydration condensation reaction accelerator". The aforementioned permeation vaporization performance test was performed on this. The results were a water permeation flux (Qw) of 3236 [g/ ^m² ·h] and an ethanol permeation flux (Qa) of 256 [g/ ^m² ·h]. The results are shown in Table 1.

[Examples]
A permeation vaporization performance test was performed on the porous support-zeolite membrane composite after use in the control example. The "porous support-zeolite membrane composite after use in the control example" is a porous support-zeolite membrane composite that has been in contact once with the treated liquid, a 100°C water/ethanol aqueous solution (5/95 mass%), in the permeation vaporization performance test. The aforementioned permeation vaporization performance test was performed on this porous support-zeolite membrane composite. The results were a water permeation flux (Qw) of 3372 [g/ ^m² ·h] and an ethanol permeation flux (Qa) of 102 [g/ ^m² ·h]. The results are shown in Table 1.

As shown in Table 1, the porous support-zeolite membrane composite that had never been in contact with a 100°C water/ethanol aqueous solution (5/95 mass%) showed a high amount of ethanol permeation compared to the control example. On the other hand, the examples showed that the porous support-zeolite membrane composite that had been in contact with a 100°C water/ethanol aqueous solution (5/95 mass%) showed a significant reduction in ethanol permeation. Thus, by contacting the porous support-zeolite membrane composite with the above-mentioned water/ethanol aqueous solution, the water permeation flux Qw remained substantially the same, while the ethanol permeation flux Qa after ethanol treatment decreased significantly, indicating an improvement in ethanol recovery.

This invention can be used to produce zeolite membranes that exhibit low permeability of relatively less permeable components in the separation of water-soluble organic compounds and water mixtures.

1. Raw material tank 2. Membrane module 3. Vacuum pump 4. Measurement trap 5. Supply tank 6. Heater 7. Cooler P1, P2 pumps V1-V12 valves

Claims (13)

A method for producing a zeolite film, comprising the step of contacting an untreated zeolite film containing countercations with a dehydration condensation reaction accelerator. The method for producing a zeolite film according to claim 1, wherein the dehydration condensation reaction accelerator contains ethanol. The method for producing a zeolite membrane according to claim 2, wherein the dehydration condensation reaction accelerator uses an aqueous ethanol solution containing 95% by volume or more of ethanol. A method for producing a zeolite film according to claim 2 or 3, wherein the temperature of the dehydration condensation reaction accelerator is 25°C or higher. A method for producing a zeolite film according to any one of claims 2 to 4, wherein the temperature of the dehydration condensation reaction accelerator is 120°C or lower. The method for producing a zeolite membrane according to claim 1, wherein the dehydration condensation reaction accelerator contains carbon dioxide. The method for producing a zeolite film according to claim 6, wherein the carbon dioxide is a gas and the temperature of the carbon dioxide is room temperature. The method for producing a zeolite film according to claim 6 or 7, wherein the carbon dioxide is in a supercritical state. Prior to the contact step, the process further includes a step of growing zeolite crystals by hydrothermal synthesis to produce the untreated zeolite film,
The untreated zeolite film contains Na ⁺ or K ⁺ as the countercation ,
In the contact step, a compound that forms a water-insoluble salt with the counter cation is used as the dehydration condensation reaction accelerator.
A method for producing a zeolite film according to any one of claims 1 to 8. The method for producing a zeolite film according to claim 9, wherein the countercation is Na ⁺ and a fluoride solution is used as the dehydration condensation reaction accelerator. The method for producing a zeolite membrane according to claim 9, wherein the counter cation is Na ⁺ and uric acid water is used as the dehydration condensation reaction accelerator. The method for producing a zeolite film according to any one of claims 9 to 11, wherein the step of generating the film is a step of growing zeolite crystals without using an organic template compound, which is an organic compound and acts as a template agent that regulates the crystal structure of the zeolite, thereby producing the untreated zeolite film. The method for producing a zeolite film according to any one of claims 9 to 11, wherein the step of production involves growing zeolite crystals in the presence of an organic template compound, which is an organic compound and acts as a template agent that regulates the crystal structure of the zeolite, and then treating the resulting zeolite film with an oxidizing agent to remove the organic template compound from the zeolite film and produce the untreated zeolite film.