JP2001097715A - Method for forming zeolite film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for efficiently producing a zeolite film having no defect and a uniform thickness on a supporter having complicated shape or a supporter having a large area. SOLUTION: This method for producing the zeolite film comprises subjecting a slurry containing seed crystals to crossflow filtration by an alumina porous supporter having 1 μm average pore diameter to make the porous supporter carry a seed crystal layer having 6 μm thickness in the interior of the pore or the surface of the supporter, and growing the seed crystal in the seed crystal layer by hydrothermal synthesis to provide the objective zeolite film having 7 μm thickness.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a zeolite membrane and a method for forming the same, and more particularly, to a method for forming a zeolite membrane on a porous support. The zeolite membrane has pores of several angstroms in the crystal, and it can be applied to separation membranes such as gas separation by molecular sieve using these pores, pervaporation, membrane reactors, gas sensors, etc. Have been.

According to the zeolite membrane forming method of the present invention,
By forming a zeolite membrane on a porous support, a zeolite membrane element that can be used for the above applications can be manufactured.

[0003]

2. Description of the Related Art Various techniques have been studied as a technique for forming a zeolite membrane. As a typical film forming method, as described in Japanese Patent Publication No. 4-80726, a sol or gel having a zeolite composition is supported on a support and then crystallized by hydrothermal treatment to produce a zeolite membrane. JP-A-7-89714 discloses a method in which a gel having a zeolite composition is supported on a support, followed by hydrothermal treatment in steam for crystallization, or a synthesis raw material for zeolite as described in JP-A-6-99044. After the support is immersed in a sol or gel containing, a hydrothermal treatment is performed to synthesize a zeolite membrane on the support.

[0004] Among them, a method which has been generally studied at present is to immerse the support in a sol or gel containing a synthetic raw material of zeolite as described in JP-A-6-99044, and then carry out hydrothermal treatment. This is a method of synthesizing a zeolite membrane on a support. In this method, the raw material constituting zeolite is supplied from a sol or gel, and a zeolite membrane is formed on the support. Therefore, the support is performed simply by immersing the support in the synthesis sol and performing hydrothermal synthesis. Film can be formed on the body surface. However, in this method, crystals are generated even in the sol or gel and adhere to the surface of the support, so that a membrane defect is easily generated, and high separation performance cannot be obtained.

In order to improve this, Japanese Patent Application Laid-Open No. 9-2026 discloses
No. 15, a method of forming a membrane inside the pores of a support as described in JP-A No. 15, and “Pervaporation separation using a zeolite membrane” (Hidetoshi Kita, “Membranes”, 20 (3), 169-182 (199)
5)) a method of forming a film by hydrothermal treatment after supporting the seed crystal on the support as in the above, or a method of forming the seed crystal as described in JP-A-7-109116 or JP-A-10-57784. Methods for hydrothermal synthesis and film formation under the condition that crystals do not grow in the liquid after being supported are described in the above-mentioned respective publications, and it has been confirmed that the separation performance is improved in each case.

[0006]

However, it is difficult to efficiently form a uniform zeolite membrane having no defects on a support having a complicated shape or a large-area support by the conventional film forming method. . An object of the present invention is to efficiently form a zeolite membrane having a uniform thickness without defects on a support having a complicated shape or a large-area support.

[0007]

According to a first aspect, according to the present invention, there is provided a method comprising the steps of: growing a seed crystal of a seed crystal layer and forming a zeolite membrane in close contact with a porous support. A method for forming a zeolite membrane, wherein the seed crystal layer is a seed crystal supporting layer having a substantially uniform thickness and supporting the seed crystal-containing slurry by filtering the slurry with a porous support on the porous support. Thereby, the above object can be achieved. This zeolite membrane forming method can be performed as follows.

The seed crystal supporting layer has a thickness of 0.1 to 20.
It can be substantially uniform within the range of μm. The seed crystal of the seed crystal layer can be grown by hydrothermal synthesis. The slurry can be subjected to cross-flow filtration or total filtration through the porous support. The cross-flow filtration conditions were set so that the seed crystal concentration in the slurry was 50 to 5000.
ppm, flow rate 0.1-10 l / min, differential pressure 0.1-10 k
gf / cm ² and the ratio A / B of the average particle diameter A of the seed crystal to the average pore diameter B of the porous support is 0.01 to 10
Can be zero.

The total filtration conditions were as follows: a seed crystal concentration of 0.1 to 100 ppm in the slurry, a differential pressure of 1 to 50 cmH ₂ O.
The ratio A / B of the average particle diameter A of the seed crystal to the average pore diameter B of the porous support can be 0.01 to 100. The seed crystal supporting layer is formed only inside the pores of the porous support, with the ratio A / B of the average particle diameter A of the seed crystals to the average pore diameter B of the porous support being 0.01 to 1. However, the seed crystal supporting layer can not be formed on the outer surface of the porous support.

In a second aspect, according to the present invention, the above object is achieved by a zeolite membrane element obtained by forming a zeolite membrane on a porous support by the zeolite membrane forming method of the present invention. Can be.

[Invention of the Invention] In the above conventional film forming method, when a film is formed on a support having a large area and a complicated shape,
It is considered that a method of supporting the seed crystal on a support and growing the seed crystal to form a film is most effective. In this case, important factors affecting the membrane performance include the state of supporting the seed crystal and conditions during hydrothermal synthesis. Among these conditions, it has been clarified that high performance can be obtained by forming a film under the condition that crystallization does not occur in the liquid as described above as conditions for hydrothermal synthesis. Is not much discussed.

The inventors of the present invention have studied the effect of the state of supporting the seed crystal on the membrane performance. As a result, when the seed crystal layer is not uniformly supported at a constant thickness, a zeolite film is likely to cause a membrane defect. And came to the conclusion. That is, if the seed crystal layer is too thick, a portion that does not crystallize remains in a part of the layer. If the seed crystal layer is too thin and not uniform, a film that sufficiently covers the region where the zeolite film is to be formed on the support is not formed. However, the conventional method of supporting seed crystals, such as dip coating, can cope with a small support.However, a support having a complicated shape such as a large support or a monolith has a large thickness unevenness of a support layer. The film could not be formed with good reproducibility.

Therefore, the present inventors have conducted intensive studies and as a result, even if the support has a complicated shape such as a large support or a monolith, the slurry containing the seed crystal is filtered through the porous support. As a result, the present inventors have found that the porous support can support a seed crystal layer having a substantially uniform thickness, and have completed the present invention. Hereinafter, first, the outline of the present invention will be described.

[Summary of the Invention] FIGS. 1 and 2 are schematic views showing a process of forming a zeolite membrane. FIG. 2 shows a crystal nucleus 22 generated in a liquid (a liquid capable of generating crystal nuclei) 21 in a film forming process without using a seed crystal.
Adheres to the surface of the support 23 and grows to become the grown crystal 22 ′ and further to the film 24. However, since nucleation and crystal growth proceed at random, film defects 25 as shown in FIG. 2 are likely to occur.

As a method of solving such a problem,
As shown in FIG. 1, the seed crystal 2 is previously supported on the surface of the support 3, and the hydrothermal reaction is performed in a liquid (a liquid capable of growing the seed crystal) 1 under conditions such that only the supported seed crystal grows. If the synthesis is performed, it is considered that the seed crystal becomes a grown crystal 2 ′, and further, a zeolite membrane 4 having no defect can be formed. I have.

Conventionally, various methods have been studied as a method for supporting a seed crystal. Among them, a slurry in which zeolite seed crystals are dispersed in a solvent is prepared as a method for supporting a seed crystal, which is less restricted by the shape of the support. A method of carrying using this is conceivable. As the simplest method, a method of supporting a seed crystal on the surface of the support by dip coating can be considered. However, when the zeolite membrane was actually formed by this method and a zeolite membrane was formed, only a membrane having low separation performance was obtained.

Examination of the cause revealed that it was due to uneven thickness of the seed crystal supporting layer. If there is a difference in the thickness of the layer depending on the location, this unevenness does not disappear even after crystal growth by hydrothermal synthesis, and it is difficult to form a film having a uniform thickness. It was found that when there was a thin portion or a thin portion, a high performance zeolite membrane could not be formed because defects tend to occur in the thick portion and the thin portion.

FIG. 3 shows the occurrence of these defects in FIG. 3. When the thickness of the seed crystal supporting layer formed on the support is too large, all of the seed crystals in the excessively thick portion are removed. The seed crystal that is not crystallized but closer to the support is not crystallized and defects are likely to occur between the support and the zeolite membrane. In this case, since the zeolite membrane does not adhere to the support, the zeolite membrane is easily peeled or cracked.

When the seed crystal supporting layer formed on the support is too thin, the zeolite membrane is formed on the portion of the seed crystal supporting layer where the seed crystal is not applied (the portion where the seed crystal abundance is low). It is not formed, the support surface remains exposed,
Since the zeolite film is not formed to cover the entire support region where the zeolite film is to be formed by supporting the seed crystal layer, a defect occurs.

Summarizing the above results, it is considered that the ideal state of supporting the seed crystal is that the seed crystal is uniformly supported on the support with a thickness of a certain value or less. As a result of examining the thickness of such a seed crystal supporting layer, at least 0.1
It has been clarified that the above-mentioned defects do not occur in the range of ２０20 μm. Note that the range of 0.1 to 20 μm is defined by the conditions of the support used in the examples, but depends on the support if a more uniform support is obtained.

The thickness of the seed crystal supporting layer is preferably within the range of 0.1 to 20 μm so that the seed crystal can be grown without generating defects to form a defect-free zeolite membrane. It may be substantially uniform. For example, the relationship (LS) / r between the maximum thickness L, the minimum thickness S, and the seed crystal diameter r at 1 mm ² is 5 or less (preferably 3 or less, more preferably 1 or less). It is sufficient if the pressure is uniform to some extent.

Next, as a result of examining various supporting methods for realizing such an ideal state of supporting the seed crystal, the supporting method using a slurry in which the seed crystal is dispersed is most effective because of simplicity and the like. Was determined to be good. However, in the normal dip coating, thickness unevenness is likely to occur as described above, and as a result of examining a method for uniformly supporting the slurry, the slurry is filtered through the porous support, so that the porous support forms a seed crystal layer. It was confirmed that the carrier could be supported with a uniform thickness.

As a filtration method for filtering a slurry containing seed crystals through a porous support and supporting the seed crystal layer on the porous support, as shown in FIG. 4, a total filtration method and a cross-flow filtration method are used. Law is conceivable. The seed crystal layer supported by total filtration is not supported by using the penetration of the slurry solvent into the support by capillary condensation as in dip coating, but is forced by applying pressure to the seed crystal as shown in the upper part of FIG. Since the support layer is formed on the support, the seed crystal layer having a uniform thickness can be supported on the support if the slurry preparation conditions and the filtration conditions are optimized.

In the cross-flow filtration, as shown in the lower part of FIG. 4, a seed crystal-containing slurry is caused to flow on a surface of a support on which a seed crystal is to be supported, and a liquid (dispersion medium) is applied to the wall of the support by a differential pressure. It flows in a direction perpendicular to the wall so as to penetrate and particles (dispersoids), in this case a part of the zeolite seed crystal, are trapped on the surface of the support. However, when the flow speed of the slurry is high, the trapped particles are scraped and dispersed again in the slurry, the thickness of the support surface layer is kept constant, and the differential pressure and the flow rate are controlled. The thickness of the zeolite membrane can also be controlled.

In each of the above methods, the seed crystal may enter the pores of the support depending on the particle size (dimension). Therefore, if the conditions are further narrowed down, it becomes possible for the support to support the seed crystal layer with a constant thickness only on the inner wall surface inside the support pores as well as on the outer surface of the support.

The main factors that affect the supported state include the concentration of seed crystals in the slurry, the flow rate, the differential pressure, and the ratio of the average particle size of the zeolite seed crystals to the average pore size of the support. As a result of the test, it became clear that the following range was appropriate.

The concentration range of the zeolite seed crystals in the slurry is 0.1 to 100 ppm (preferably 0.1 ppm) by total filtration.
1 to 50 ppm, more preferably 0.1 to 10 pp
m), 50 to 5000 ppm (preferably 100 to 3000 ppm, more preferably 500 ppm) by cross-flow filtration.
If the concentration is lower than the minimum value of the concentration range in each filtration, the time required for supporting the seed crystal becomes too long and is not practical,
When the concentration is higher than the maximum value of the concentration range in each filtration, only a too thick membrane can be supported even if other conditions are changed. The difference in the concentration range between the total filtration and the cross-flow filtration is because cross-flow filtration requires a higher concentration than the total filtration because a force for peeling off the seed crystal layer supported on the surface of the porous support is also applied. It is.

The flow rate in the case of cross-flow filtration is 0.1 to
10 l / min (preferably 1 to 10 l / min, more preferably 1 to 3 l / min) is appropriate, and if it is slower than 0.1 l / min, the seed crystal adheres thickly to the surface of the support, and
If it is faster than 0 l / min, the amount of seed crystals trapped inside the pores tends to be small, and the efficiency tends to be poor. The appropriate range of differential pressure is 0.1 to 10 kgf / cm by cross-flow filtration.
² (preferably 0.1-1 kgf / cm ² , more preferably 0.1-0.5 kgf / cm ² ), and 1-50
cmH ₂ O (preferably 1 to 30 cmH ₂ O, more preferably 5 to ₂₀ cmH ₂ O), and when the differential pressure is higher than the maximum value of the respective appropriate range, a thick layer is formed on the surface of the support. If the respective values are lower than the minimum values of the appropriate ranges, the thickness unevenness of the seed crystal layer will increase.

The ratio A / B of the average particle diameter A of the zeolite seed crystal to the average pore diameter B of the porous support is preferably in the range of 0.01 to 100 (preferably 0.1 to 100) in the case of cross-flow filtration. 10, more preferably 0.3 to 5),
In the case of total filtration, it is in the range of 0.01 to 100 (preferably 0.
It is important to be within the range of from 01 to 50, more preferably from 0.1 to 10, and even more preferably from 0.3 to 5), and if the value is smaller than the minimum value in the above range for each filtration, the seed crystal is supported. There is a tendency to permeate the body pores, and if it is larger than the maximum value of the above range for each filtration, the seed crystals can not be sufficiently supported because the seed crystals tend not to enter the inside of the pores Or the seed crystal layer becomes thicker even if it is carried.

[0030]

[Preferred Embodiment] [Zeolite Membrane Forming Method] The zeolite membrane forming method of the present invention comprises a step of growing a seed crystal of a seed crystal layer to form a zeolite membrane before the step of forming a zeolite membrane. And a seed crystal layer supporting step of supporting the seed crystal layer on the porous support by filtering the slurry containing the seed crystals with a porous support.

As a method for forming a zeolite film by growing a seed crystal layer, a hydrothermal synthesis method is preferably used. Various methods can be applied as the hydrothermal synthesis method, and for example, a method as described in JP-A-10-57784 can be used. As a starting material, preferably, a zeolite skeleton metal source, an alkali metal source, and water are used, and a crystallization promoter can be added as necessary.

As the zeolite framework metal source, various metal sources used in the conventional zeolite synthesis, for example,
Silica and alumina are applicable. Silica colloid sol as a silica source, water glass, aluminum nitrate, sodium aluminate, boehmite sol as an alumina source,
A silica-alumina composite colloid is used. As the alkali metal source, sodium hydroxide, potassium hydroxide, or the like is used.

As the crystallization accelerator, those used for conventional zeolite production, for example, tetrapropylammonium bromide (TPABr), tetrabutylammonium hydroxide and the like can be added.

The crystal system of the synthesizable zeolite is M
There are various zeolites such as FI, A type, Y type and X type, and various metal sources such as iron, chromium, titanium and the like can be applied as the skeleton metal source.

As a mixing method, in addition to stirring and mixing, in addition to ordinary pulverization and mixing using a general ball mill, attritor, etc., submicron-order pulverization and mixing using a diamond fine mill (manufactured by Mitsubishi Heavy Industries, Ltd.). Special mills capable of dispersing are also possible. Further, as a material of the cobblestone that is the grinding media, preferably, a material that does not easily cause impurities to be mixed into the solution for hydrothermal synthesis, for example, various materials such as zirconia can be applied. Further, ultrasonic waves can be used to disperse the aggregated particles.

Various kinds of zeolite crystals can be used depending on the type of zeolite to be synthesized. As the seed crystal, a commercially available zeolite crystal, a crystal obtained by pulverizing the zeolite crystal to obtain fine particles, or a zeolite crystal synthesized by various methods can be used. Further, the “seed crystal” in the present invention includes a precursor of a zeolite seed crystal at a stage before changing to a zeolite seed crystal.

The grain size of zeolite in the seed crystal is as follows:
For example, it can be 0.01 to 10 μm, preferably 0.01 to 5 μm (more preferably 0.01 to 1 μm).
m).

The material of the porous support may be, for example, a single element metal, alloy, ceramic or the like. The shape may be any shape capable of growing the zeolite, and various shapes such as a film shape, a plate shape, a tubular shape, a pellet shape, a hollow fiber shape, and a honeycomb shape are conceivable. As the production method, a production method such as extrusion molding, press molding, and casting molding can be selected according to the shape of the support. The support structure is 2
A structure having more than two layers may be used, and a method such as dip coating can be used for the second and subsequent layers.

The porous support may be any as long as it can support the seed crystal by filtering the slurry containing the seed crystal.
The porosity of the porous support is preferably 10 to 60% (more preferably 20 to 50%, further preferably 30 to 45%).
%).

The hydrothermal treatment (hydrothermal synthesis) is preferably carried out in a pressure vessel generally at about 80 to 250 ° C. for 1 hour to 18 hours.
It is performed for about 0 hours. After the hydrothermal treatment, the support supporting the zeolite membrane is washed and dried, and then subjected to a heat treatment to remove a thermally decomposable component such as a crystallization promoter.

According to the method for forming a zeolite membrane of the present invention,
The thickness of the zeolite membrane is in the range of 0.1 to 20 μm, and a zeolite membrane having a uniform thickness, a small thickness variation and no defects can be formed on the porous support. For example,
Maximum thickness L, minimum thickness S and seed crystal diameter r at 1 mm ²
(L-S) / r of 5 or less (3 or less, further 1 or less) can be formed.

[0042]

EXAMPLES Example 1 A-type zeolite powder having a particle size of 0.4 μm was dispersed in water on a tubular α-alumina porous support (outer diameter 10 mm × inner diameter 7 mm, length 150 mm) having an average pore diameter of 1 μm. The seed crystal was supported on the support by a cross-flow filtration method using the suspension (slurry) thus obtained.

The cross-flow filtration was performed at a suspension seed crystal concentration of 4000 ppm, a flow rate (flow rate) of 5 l / min, and an operating pressure (differential pressure) of 0.2 kgf / cm ² . A deposited layer of zeolite seed crystals could not be confirmed on the surface of the support due to a large flow rate, but a trapped zeolite seed crystal layer having a thickness of 5 μm could be confirmed inside the pores of the support.

Next, a zeolite membrane was formed by hydrothermal synthesis. As raw materials, sodium silicate is used as a silica source, aluminum hydroxide is used as an alumina source, sodium hydroxide is used as an alkali source, and reverse osmosis water.
₂ O: Al ₂ O ₃ : SiO ₂ : H ₂ O = 90: 1: 9: 57
The above raw materials were mixed so as to be 60 to prepare a solution for hydrothermal synthesis. The support supporting the seed crystal was immersed in this solution, and an A-type zeolite membrane was formed at 80 ° C. by hydrothermal synthesis.

After hydrothermal synthesis for 5 hours, the zeolite membrane of the washed and dried sample (porous support having a zeolite membrane formed thereon) was subjected to SEM (scanning electron microscope; the same applies hereinafter).
As a result of observation at a magnification of 00, it was confirmed that the cubic crystals were connected to one surface to form a polycrystalline film, and it was confirmed from XRD (X-ray diffraction, the same applies hereinafter) that the crystals were A-type zeolite. Also, the cross section of the hydrothermally synthesized film was SEM (1
As a result, it was confirmed that a thin zeolite layer having a thickness of about 7 μm was formed in the pores of the alumina support.

Example 2 The used seed crystal was 3 μm in particle size.
Operating pressure of 0.36 kgf / cm ^Two, Flow
Except that the speed was 2.5 l / min, the same method as in Example 1 was used.
Olite film was produced. After seed crystal loading during fabrication process
As a result of observing the cross section of the support by SEM, a thickness of 14
μm thin zeolite seed crystal support layer
It was confirmed that it was formed on the surface of the holding body. Also water
Formation of this hydrothermally synthesized film from XRD measurement after thermal synthesis
The crystal is confirmed to be type A zeolite.
Was.

Example 3 The slurry concentration was 2000 pp
A zeolite membrane was produced in the same manner as in Example 2 except that m was used. As a result of observing the cross section of the support after supporting the seed crystal by SEM in the production process, it was confirmed that a thin zeolite seed crystal supporting layer having a thickness of 9 μm was formed inside the pores of the porous alumina support. X after hydrothermal synthesis
From the RD measurement, it was confirmed that the crystals forming the hydrothermally synthesized film were A-type zeolites.

Example 4 A zeolite membrane was prepared in the same manner as in Example 1 except that the flow rate was 0.5 l / min, the concentration was 500 ppm, and the operating pressure was 0.1 kgf / cm ² .
In the manufacturing process, the cross section of the support after supporting the seed crystal was SEM
As a result, it was confirmed that a thin zeolite seed crystal support layer having a thickness of 8 μm was formed on the outer surface and the inside of the pores of the porous alumina support. XRD measurement after hydrothermal synthesis confirmed that the crystals forming the hydrothermally synthesized film were A-type zeolites.

Example 5 The pore size of the porous support was set to 0.
A zeolite membrane was prepared in the same manner as in Example 1, except that the particle diameter of the seed crystal was 2 μm and the particle diameter of the seed crystal was 0.1 μm. SEM observation of the cross section of the support after seed crystal support during the fabrication process confirmed that a thin zeolite seed crystal support layer having a thickness of 1 μm was formed on the outer surface and inside the pores of the alumina porous support. did it. XRD measurement after hydrothermal synthesis confirmed that the crystals forming the hydrothermally synthesized film were A-type zeolites.

Example 6 A zeolite membrane was prepared in the same manner as in Example 1 except that the seed crystal was supported on the porous support by total filtration at a seed crystal concentration of 50 ppm in the slurry and a pressure difference of 20 cmH ₂ O. A film was formed. As a result of observing the cross section of the support after supporting the seed crystal by a SEM during the film forming process, it was found that a thin zeolite seed crystal supporting layer having a thickness of 7 μm was formed on the outer surface and the inside of the pores of the alumina porous support. It could be confirmed. XRD measurement after hydrothermal synthesis confirmed that the crystals forming the hydrothermally synthesized film were A-type zeolites.

Example 7 A zeolite membrane was prepared in the same manner as in Example 1 except that a seed crystal of Y-type zeolite was used as a seed crystal. As a result of observing the cross section of the support after supporting the seed crystal by SEM in the production process, it was confirmed that a thin zeolite seed crystal supporting layer having a thickness of 5 μm was formed inside the pores of the porous alumina support. XRD measurement after hydrothermal synthesis confirmed that the crystals forming the hydrothermally synthesized film were FAV zeolite.

Comparative Example 1 A zeolite membrane was produced in the same manner as in Example 1, except that the seed crystal concentration in the slurry was 10,000 ppm. When the cross section of the support after supporting the seed crystal was observed by SEM in the manufacturing process, the seed crystal was supported on the support with a thickness of 250 μm. Defects that were not formed were confirmed.

Comparative Example 2 A zeolite membrane was produced in the same manner as in Example 1 except that the flow rate was 30 l / min. Observation of the fracture surface of the support after supporting the seed crystal in the manufacturing process revealed that the thickness of the seed crystal supporting layer was 1 μm or less, and a portion where no seed crystal was supported was also confirmed. Observation of the fracture surface of the support after hydrothermal synthesis also confirmed a defective portion where the zeolite membrane was not formed.

Comparative Example 3 A zeolite membrane was formed in the same manner as in Example 1 except that the seed crystal was supported by a dip coating method. When the fracture surface of the support was observed after the seed crystal was supported, the thickness of the seed crystal supporting layer was 7 μm or less, and the thickness varied widely. Observation of the fracture surface of the support after hydrothermal synthesis also confirmed a defective portion where the zeolite membrane was not formed.

Example 8 By the pervaporation (PV) method,
Examples 1 to 7 and Comparative Examples 1 to 1 in an aqueous ethanol system
The separation performance of the zeolite membrane obtained in each of No. 3 was evaluated. Using a PV device as shown in FIG.
The test was performed at 30 ° C. using a 0% by weight aqueous ethanol solution.
The concentrations of the feed solution and the permeate were measured by gas chromatography. The separation coefficient α was calculated by the following equation.

[0056]

(Equation 1)

Here, X ₁ is the molar concentration on the supply side of ethanol (mol%), and X ₂ is the molar concentration on the supply side of water (mol%).
%), Y ₁ is the molar concentration on the permeation side of ethanol (mol)
%) And Y ₂ indicate the molar concentration on the permeation side of water (mol%), respectively.

Table 1 shows the results of the separation test (the results of the evaluation of the PV characteristics of the zeolite membrane). As can be seen from the results, all the A-type zeolite membranes in which the seed crystal supporting layer was controlled were 1000
High separation performance of 0 or more was shown. 100 for Y type
A membrane showing a degree of separation performance was obtained. However, as shown in the comparative example, when the seed crystal supporting layer is thick or thin,
Film defects were likely to occur, resulting in poor PV performance.
In addition, in the case of supporting by dip coating, the thickness unevenness is large compared to the filtration method, and defects are likely to occur in the formed film.
V performance has dropped.

[0059]

[Table 1]

Example 9 An α-alumina support having an average pore diameter of 1 μm and having a diameter of 30 mm as shown in FIG.
A seed crystal was supported on the support by a cross-flow filtration method using a suspension of the MFI zeolite powder dispersed in water. The cross-flow filtration was performed at a seed crystal concentration of 4000 ppm in the slurry, a flow rate of 5 l / min, and an operating pressure (differential pressure) of 0.2 kgf / cm ² . No deposited layer of zeolite seed crystals was found on the surface of the support due to the large flow rate, but zeolite seed crystals trapped were found inside the pores of the support, and the thickness was 6 μm.

In the hydrothermal synthesis, as starting materials, sodium hydroxide, TPABr (tetrapropylammonium bromide), distilled water, silica sol (Catalyst Kasei Kogyo: SI-
30) was used. These raw materials are converted into TPABr: Na
₂ O: SiO ₂ : H ₂ O = 0.1: 0.05: 0.1: 8
The mixture was mixed so as to have a ratio of 0 to obtain a sol for zeolite synthesis. The sol was stirred and mixed with a magnetic stirrer, and then pulverized and mixed with a zirconia ball (diameter 0.3 mm) using a diamond fine mill (manufactured by Mitsubishi Heavy Industries, Ltd.). The support supporting the sol and the seed crystal was placed in an autoclave, the inside of the autoclave was evacuated, bubbles in the pores of the support were removed, and the pores were filled with a sol for synthesis. Hydrothermal synthesis was performed for 72 hours.

After completion of the hydrothermal synthesis, the support was washed with warm water of 80 ° C., further ultrasonically washed, and replaced with distilled water.
Dry at 0 ° C. for 24 hours. Thereafter, firing was performed at 600 ° C. for 2 hours to remove TPABr in the crystal. Zeolite membrane is X
From the result of RD, it was confirmed that it was MFI. Also, from the result of XRD, the pore diameter was considered to be about 0.6 nm, which coincided with the pore diameter of general MFI.

Comparative Example 4 A zeolite membrane was formed in the same manner as in Example 9 except that the seed crystal concentration in the slurry was 10,000 ppm. When the cross section of the seed crystal supporting layer was observed by SEM in the process of film formation, the seed crystal layer was supported on the support with a thickness of 50 μm, and the film was formed by observation of the fracture surface of the support after hydrothermal synthesis. The part that did not exist could be confirmed.

Comparative Example 5 Example 9 was performed without using a seed crystal.
Hydrothermal synthesis was performed in the same manner as described above to form a zeolite membrane.

Example 10 Examples 7 and 9, Comparative Example 4,
Table 2 shows the results (permeability, transmission coefficient ratio) of the gas separation test performed on the zeolite membrane formed in Example 5. The gas separation test was performed by the following method. First, as shown in FIG. 7, both ends of the monolith sample are connected to the flow path of the test gas via the sample fixing jig. Next, a mixed gas of 10% by volume of carbon dioxide and 90% by volume of nitrogen as a test gas was supplied from the inner surface side of the sample, and gas permeating through the zeolite membrane and out of the support was collected and analyzed by gas chromatography. The transmittance and the separation coefficient were calculated by the following equations.

[0066]

(Equation 2)

In the above formula, Q is the transmittance (mol / m
² · s · Pa), A is the permeation amount (mol), _Pr is the supply side pressure (Pa), P _p is the permeation side pressure (Pa), S is the membrane area (m ² ), and T is time (s). Represents

The separation coefficient was calculated by the following equation. In addition,
In the following formula, gas type 1 is carbon dioxide, and gas type 2 is nitrogen.

[0069]

(Equation 3)

[0070] In the above formula, P _r is the total pressure of the feed side gas (Pa), total pressure P _p is the permeate side gas (Pa), R _p is the permeate side flow rate (mol / min), P _a is the opening pressure (Pa), T is temperature (K), T _o is the standard temperature (K), P _o is the standard pressure (P
a), C _p1 is the concentration (%) of the permeate gas (1), C _r1 is the concentration (%) of the supply gas (1), and C _p2 is the permeate gas (2).
, _Cr2 is the concentration (%) of the supply gas (2),
Q ₁ is the gas (1) transmittance (mol / m ² · s · Pa);
Q ₂ is the gas (2) transmittance (mol / m ² · s · Pa);
α ^* is a separation coefficient (permeability coefficient ratio).

As can be seen from the results of the gas separation performance of the zeolite membrane shown in Table 2, the samples prepared according to the present invention were prepared by using a seed crystal in which the thickness of the seed crystal layer was not appropriate as shown in the comparative example or using a seed crystal during synthesis. It was confirmed that the sample exhibited higher separation performance than the sample without the sample.

According to the results of the PV test and the gas separation test, the sample prepared by supporting the seed crystal while controlling the supporting thickness by a filtration method was used when the thickness of the supporting layer was not appropriate or when another supporting method was used. As compared to the case where no seed crystal was used, it was confirmed that high performance was exhibited, and high performance was exhibited even when the use of the sample was different.

[0073]

[Table 2]

[0074]

The method for forming a zeolite membrane according to any one of claims 1 to 7, comprising a step of growing a seed crystal of a seed crystal layer and forming a zeolite membrane in close contact with a porous support, thereby forming a film.
Since the seed crystal layer is a seed crystal support layer having a substantially uniform thickness in which the slurry containing the seed crystal is filtered through the porous support and supported on the porous support, the following basic effects are obtained. Can be played.

A zeolite membrane having a uniform thickness without defects in the support can be efficiently formed. In particular, a zeolite membrane having a uniform thickness without defects can be efficiently formed even with a support having a complicated shape or a support having a large area.

The method for forming a zeolite membrane according to claims 2 to 7 is
Since the above-mentioned respective configurations are further provided, the above-described basic effects are remarkable.

The zeolite membrane element of claim 8 is obtained by forming a zeolite membrane on a porous support by the zeolite membrane forming method of the present invention, so that the zeolite membrane has no defects and a uniform thickness.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a film forming process using a seed crystal in a zeolite film forming method of the present invention.

FIG. 2 is a schematic diagram showing a film forming process without using a seed crystal in a conventional zeolite film forming method.

FIG. 3 is a diagram showing the occurrence of defects in a zeolite membrane.

FIG. 4 is a diagram showing a method of supporting a seed crystal on a support by filtering the slurry containing the seed crystal on the support in the method for forming a zeolite membrane of the present invention, wherein the upper stage shows This is the case of total filtration, and the lower stage is the case of cross-flow filtration.

FIG. 5 is a diagram schematically showing a PV (pervaporation) apparatus for evaluating the separation performance of a zeolite membrane.

FIG. 6 is a diagram showing an end surface of a substantially cylindrical α-alumina support having 91 substantially cylindrical holes in a longitudinal direction thereof (a 91-hole monolith substrate).

FIG. 7 is a schematic sectional view of a gas separation test sample in a gas flowing direction.

[Explanation of symbols]

 1, 21 liquid 2 seed crystal 22 crystal nucleus 2 ', 22' grown crystal 3, 23 support 4, 24 zeolite membrane 25 membrane defect

Continued on the front page (72) Inventor Takeo Yamaguchi 3-15-2 Dobashi, Miyamae-ku, Kawasaki-shi, Kanagawa Prefecture (72) Inventor Yasunori Ando 3-36 Noritakeshinmachi, Nishi-ku, Nagoya-shi, Aichi Prefecture Noritake Co., Ltd. F term (reference) 4D006 GA25 GA41 HA77 KE03P KE07P KE08P KE12P KE13P MA06 MA22 MA31 MB03 MB04 MC02 MC03X NA46 NA50 PA01 PB14 PB20 PB32 PB63 PB64 PC69 4G046 JA00 JB06 JB18 4G073 BD18 CZ11 C06 C08 CZ01 C06 C08

Claims (8)

[Claims] 1. A method comprising the step of growing a seed crystal of a seed crystal layer and forming a zeolite membrane in close contact with a porous support to form a film, wherein the seed crystal layer comprises a slurry containing a seed crystal. A method for forming a zeolite membrane, comprising a seed crystal supporting layer having a substantially uniform thickness that is filtered by a porous support and supported on the porous support. 2. The seed crystal supporting layer has a thickness of 0.1 to 20.
The method for forming a zeolite membrane according to claim 1, wherein the zeolite membrane is substantially uniform within a range of μm. 3. The method for forming a zeolite membrane according to claim 1, wherein the seed crystal of the seed crystal layer is grown by hydrothermal synthesis. 4. The method according to claim 1, wherein said slurry is subjected to cross-flow filtration or total filtration through said porous support.
4. The method for forming a zeolite membrane according to any one of 3. 5. The cross-flow filtration conditions include a seed crystal concentration of 50 to 5000 ppm in the slurry and a flow rate of 0.1 to 5000 ppm.
10 l / min, differential pressure 0.1 to 10 kgf / cm ² , ratio A / B of the average particle diameter A of the seed crystal to the average pore diameter B of the porous support is 0.01 to 100 The method for forming a zeolite membrane according to claim 4, characterized in that: 6. The total filtration conditions include a seed crystal concentration in the slurry of 0.1 to 100 ppm and a differential pressure of 1 to 50 cmH ₂ O.
The zeolite membrane formation according to claim 4, wherein the ratio A / B of the average particle diameter A of the seed crystal to the average pore diameter B of the porous support is 0.01 to 100. Method. 7. The ratio A / B of the average particle diameter A of the seed crystal to the average pore diameter B of the porous support is 0.01 to 1, and
The method according to claim 1, wherein the seed crystal support layer is formed only inside the pores of the porous support, and the seed crystal support layer is not formed on an outer surface of the porous support. The method for forming a zeolite membrane according to the above. 8. A zeolite membrane element obtained by forming a zeolite membrane on a porous support by the method for forming a zeolite membrane according to any one of claims 1 to 7.