JPWO2017081841A1 - Crystalline silica membrane composite, production method thereof, and fluid separation method - Google Patents

Abstract

A porous substrate and a pure silica film formed on the surface of the porous substrate, the pure silica film having a CHA-type crystal structure, and a permeance ratio between H ₂ and SF ₆ : H ₂ / SF ₆ is a crystalline silica film composite having a crystalline silica membrane composite with a CHA type crystal structure in an aqueous suspension containing water, silica material, organic structure directing agent and hydrofluoric acid Is produced by bringing a porous base material coated with hydrothermal synthesis into contact with each other, provided that the silica material contains crystalline silica powder having a CHA type crystal structure.

Description

  The present invention relates to a crystalline silica membrane composite having a crystalline pure silica membrane whose framework is substantially free of aluminum.

Technical background

  As a technique for separating and purifying gas and / or liquid (hereinafter collectively referred to as fluid), an adsorption separation method, an absorption separation method, a distillation separation method, a cryogenic separation method, a membrane separation method, and the like are known. Among these, the membrane separation method is considered promising from the viewpoint of energy saving. According to the membrane separation method, molecules can be separated without phase change, and the apparatus can be made compact.

  As a separation membrane used in the membrane separation method, a polymer membrane, an organic-inorganic composite membrane, and the like have been developed, but an inorganic membrane is desirable in terms of excellent heat resistance, pressure resistance, and durability. The silica film is classified as an inorganic film because it has a framework (silica network) of silica (silicon dioxide) formed by Si—O bonds as a basic skeleton. Silica membranes can be used as molecular sieve membranes because they allow smaller molecules to penetrate and inhibit the passage of larger molecules than silica networks. In general, a silica film is synthesized by a sol-gel method (liquid phase reaction), a CVD method (gas phase reaction) or the like, but an amorphous silica network is formed by these methods.

  However, the amorphous silica film is easily affected by moisture, and when exposed to high-temperature water vapor, the framework is denatured and the molecular sieving ability is lowered. On the other hand, the use of crystalline pure silica having a zeolite topology as a separation membrane can increase the water vapor resistance of the separation membrane.

  A general zeolite is known as a crystalline aluminosilicate, and is a porous material containing silica and alumina (aluminum oxide) as main components and an alkali metal cation as charge compensation. Crystalline aluminosilicate is easier to form a separation membrane than crystalline pure silica and easy to manufacture. However, it is known that aluminosilicate has molecular permeation inhibition due to adsorption of water molecules and is poor in water vapor resistance, chemical resistance, and thermal stability. Non-Patent Document 1 proposes a CHA type aluminosilicate film.

  On the other hand, crystalline pure silica does not contain aluminum in the framework, and thus has high hydrophobicity and is excellent in water vapor resistance, chemical resistance, and thermal stability. As typical examples of crystalline pure silica, Patent Documents 1 to 3 report DDR type pure silica zeolite (Si-DDR), and Patent Document 4 and Non-Patent Document 2 report MFI type pure silica zeolite (Si-MFI). It has also been reported that these can be used as separation membranes (Patent Documents 5 and 6). Non-Patent Document 3 proposes a method for producing CHA type pure silica zeolite (Si-CHA) powder. Furthermore, Yogo et al. Have proposed Si-CHA and a carbon dioxide separation method using the same (Patent Documents 7 and 8).

JP 2005-67991 A JP 2004-105942 A International Publication No. 2007/119286 Pamphlet JP 2010-208948 A JP 2003-159518 A JP 2005-289735 A JP 2009-114007 A JP 2009-214101 A

J. Mater. Chem. A, 2, 13083-13092 (2014) Micropor. Mesopor. Mater., 108, 136-142 (2008) Chem. Commun., 1881 (1998)

  Since Si-MFI has a developed three-dimensional pore structure and a large pore volume, it can form a separation membrane having a high fluid permeation rate (permeance). However, the pores of Si-MFI have a large opening diameter of 5.6 × 5.3 mm or 5.5 × 5.1 mm, insufficient molecular sieving ability, and it is difficult to obtain desired selectivity. is there.

  On the other hand, Si-DDR pores have an opening diameter of 3.6 × 4.4 mm, and thus have an advantage in that they have excellent molecular sieving ability and can easily obtain good selectivity. However, since the pores of Si-DDR have a two-dimensional pore structure and a small pore volume, it is difficult to obtain a desired permeance.

  Si-CHA has a three-dimensional pore having an opening diameter of 3.8 × 3.8 mm and a large cavity. The pore volume of Si-CHA is located between Si-MFI and Si-DDR, and is expected to achieve both desired permeance and selectivity.

  However, Si-CHA is produced under limited conditions. Specifically, since Si-CHA is crystallized from an aqueous suspension having a very low water content (or a solid), there is a drawback that the productivity of the separation membrane is low. In addition, since Si-CHA crystals tend to be isolated particles with good dispersibility, it is difficult to form them as a dense film on the surface of the porous substrate. Therefore, no synthesis example of a dense Si—CHA film having a desired molecular sieving ability has been reported so far.

  In view of the above, the present invention provides an effective method for forming a pure silica film (Si-CHA film) having a CHA-type crystal structure as a dense film on the surface of a porous substrate, and a crystal having excellent molecular sieving ability. A porous silica membrane composite.

One aspect of the present invention includes a porous substrate and a crystalline pure silica film formed on a surface of the porous substrate, the pure silica film having a CHA-type crystal structure, and H Permeance ratio of ₂ to SF ₆ : relates to a crystalline silica membrane composite having H ₂ / SF ₆ exceeding 10.

  According to another aspect of the present invention, (i) a step of preparing a porous substrate having a first surface and a second surface and having pores that allow the first surface and the second surface to communicate with each other; ii) a step of applying a crystalline silica powder having a CHA-type crystal structure to at least one selected from the first surface and the second surface; and (iii) water, a silica material, an organic structure directing agent (SDA) And (iv) bringing the aqueous suspension into contact with the surface on which the crystalline silica powder of the porous substrate has been applied, and a step of preparing an aqueous suspension containing hydrofluoric acid (HF). And a step of growing a crystalline pure silica film having a CHA type crystal structure on the surface by hydrothermal synthesis, wherein the silica material contains a crystalline silica powder having a CHA type crystal structure. For manufacturing method of silica membrane composite To.

  In a preferred embodiment, the porous substrate has a first surface and a second surface, and has pores that allow the first surface and the second surface to communicate, and the first surface and the second surface. The pure silica film is formed on at least one of the above. At this time, still another aspect of the present invention is a fluid separation method for separating a specific component from a mixed fluid using the crystalline silica membrane composite, wherein (i) the first surface and the second surface are separated. On the other hand, supplying a mixed fluid containing a first component and a second component having different permeances with respect to the pure silica film to the first space communicating with the pores; (ii) the first surface and the first Recovering a permeated fluid that has permeated the pure silica membrane from a second space communicating with the pores on the other of the two surfaces, and recovering a non-permeated fluid from the first space. .

  According to the present invention, a crystalline pure silica film (Si-CHA film) having a CHA type crystal structure densely formed on the surface of a porous substrate can be obtained. Therefore, it is possible to provide a crystalline silica film composite having excellent water vapor resistance, chemical resistance, and thermal stability and having an excellent molecular sieving ability. The crystalline silica membrane composite can be applied to various fluid separation methods.

It is an expanded sectional view which shows notionally an example of the structure of a crystalline silica membrane composite. It is a perspective view which shows notionally an example of a cylindrical crystalline silica membrane composite. It is a scanning electron micrograph (SEM image) of the surface of the film product of the comparative example 1 and Examples 1-4. 2 is a SEM image of a cross section of the film product of Example 1. FIG. 1 is a conceptual diagram of a cross-sectional structure of a film product of Example 1. FIG. It is the schematic of the apparatus for performing the permeation | transmission test of various probe gas. FIG. 2 shows adsorption isotherms (a) of propylene and propane for the Si—CHA powder prepared in Example 1 and adsorption isotherms (b) of propylene and propane for the CHA-type aluminosilicate powder prepared in Reference Example 3. FIG. It is the schematic of the apparatus for performing the dehydration test from the alcohol aqueous solution by pervaporation separation.

The crystalline silica membrane composite according to the present invention comprises a porous substrate and a crystalline pure silica membrane formed on the surface of the porous substrate. However, the pure silica membrane has a CHA type crystal structure, is dense, and has high selectivity. Specifically, the permeance ratio between H ₂ and SF ₆ : H ₂ / SF ₆ exceeds 10, and can be 50 or more, or 100 or more. In the pure silica film, CHA-type crystals are precipitated by random orientation, but a uniform film is formed in appearance.

  Here, the pure silica film refers to a film in which the framework of the crystal structure is formed of crystalline silica that does not substantially contain aluminum. The crystalline silica forming the pure silica film is allowed to contain a small amount of impurities, but the content of the third element other than silicon and oxygen contained in the crystalline silica is 1% by mass or less. desirable. Such impurities or the third element are dissolved from, for example, the porous substrate and mixed into the crystalline silica. Even when the crystalline silica contains a trace amount of aluminum, it can be regarded as substantially free of aluminum if the aluminum content is 1% by mass or less.

  The indications such as CHA, DDR, and MFI are codes that specify the structure of the zeolite determined by the International Zeolite Association (IZA). It is shown that.

The permeance ratio is a permeation rate (permeance: mol / m ² · s · Pa) or permeation ratio measured for two kinds of fluids, and is an index indicating the selectivity of the separation membrane. When the density of the pure silica film decreases and the number of defects in the film increases, the permeance ratio: H ₂ / SF ₆ approaches the Knudsen coefficient ratio. In other words, the larger the permeance ratio, the denser the pure silica film.

A dense pure silica crystal having a CHA type crystal structure has a large pore volume, and can achieve a pore volume of, for example, 0.25 cm ³ / g or more, and further 0.3 cm ³ / g or more. Since the permeance of the fluid is increased due to the large pore volume, the fluid can be separated and purified with a pure silica membrane efficiently.

The permeance of H ₂ due to the pure silica film exceeds, for example, 5 × 10 ⁻⁷ mol / m ² · s · Pa, and can achieve 1 × 10 ⁻⁶ mol / m ² · s · Pa or more. However, an excessively high permeance means that the denseness of the pure silica film is low and there are many defects. The permeance of H ₂ is, for example, less than 1 × 10 ⁻⁵ mol / m ² · s · Pa, and preferably 5 × 10 ⁻⁶ mol / m ² · s · Pa or less.

Since the pure silica membrane has high selectivity, the permeance ratio of CO ₂ and N ₂ : CO ₂ / N ₂ is also large, for example, exceeding 2, and being able to achieve 3 or more or 5 or more.

  The thickness of the pure silica film is not particularly limited, but it is preferably 10 μm or less from the viewpoint of forming a film with small defects and realizing high selectivity, and is 0.5 to 5 μm or 1 to 5 μm. Preferably there is. The pure silica film formed on the surface of the porous substrate usually has a composite layer of the porous substrate and silica. A preferable range of the thickness of the pure silica film is a thickness range when the composite layer is excluded.

  The material of the porous substrate is preferably an inorganic material from the viewpoint of durability, and is preferably a sintered porous body of ceramic or metal having air permeability. Examples of ceramics that can be used include metal oxides such as silica, alumina, mullite, zirconia, cordierite, and titania. Furthermore, metals such as stainless steel, copper, aluminum, and titanium, and nitrides and carbides such as silicon nitride and silicon carbide can also be used. These may be used alone or in combination of two or more.

  Although the shape of a porous base material is not specifically limited, Usually, it has a 1st surface and a 2nd surface, and has a pore which connects a 1st surface and a 2nd surface. At this time, a crystalline pure silica film may be formed on at least one of the first surface and the second surface.

  FIG. 1 shows a crystalline silica film composite 10 having a porous base material 13 having a first surface 11 and a second surface 12 and a crystalline pure silica film 14 formed on the first surface 11. An expanded sectional view is shown with a conceptual diagram. FIG. 2 is a conceptual diagram showing a perspective view of a crystalline silica film composite 10A having a cylindrical porous substrate 13A and a crystalline pure silica film 14A formed on the outer peripheral surface thereof.

  The crystalline silica membrane composite can be used in a fluid separation method for separating a specific component from a mixed fluid. For example, a mixed fluid containing a first component and a second component having different permeances with respect to the crystalline pure silica film in a first space communicating with the pores of the porous substrate on one of the first surface and the second surface. When supplied, either the first component or the second component preferentially passes through the crystalline pure silica film and the pores of the porous substrate. As a result, the permeated fluid having a different composition from the mixed fluid supplied to the first space moves to the second space communicating with the pores of the porous substrate on the other of the first surface and the second surface. The first component or the second component can be separated by collecting the permeated fluid and repeating the same operation as necessary.

  Specific applications of the crystalline silica membrane composite include purification of natural gas or biogas, hydrogen transport using organic hydride, purification of light hydrocarbons, dehydration of alcohol, acetic acid and the like.

Natural gas and biogas contain methane as a main component, and contain at least one selected from the group consisting of carbon dioxide, carbon monoxide, nitrogen, and C ₂ or higher hydrocarbons (ethane, propane, etc.) as subcomponents. It is a mixed fluid. For example, biogas contains a large amount of carbon dioxide in addition to methane. When biogas is supplied to the first space, carbon dioxide (first component) having high permeance moves to the second space, and methane (second component) is concentrated in the first space. The blast furnace gas is a mixed fluid containing hydrogen (first component) which is a useful component and at least one (second component) selected from the group consisting of carbon dioxide, carbon monoxide and nitrogen. By using the crystalline silica membrane composite, methane and hydrogen can be concentrated.

The hydrogen transport using organic hydride is, for example, formula (1):
C ₆ H ₁₁ CH ₃ (methylcyclohexane) ⇔C ₆ H ₅ CH ₃ (toluene) + 3H ₂
This means that hydrogen is transported as an organic hydride (methylcyclohexane) using the reversible reaction. When an organic hydride dehydrogenation reaction is performed, a mixed fluid containing hydrogen (first component) and an aromatic compound (second component) is generated. By using the crystalline silica membrane composite, the aromatic compound (toluene) can be removed from the mixed fluid, and hydrogen as the first component can be concentrated. Under conditions of high temperature and low pressure, dehydrogenation reaction from methylcyclohexane is dominant, and under conditions of low temperature and high pressure, toluene hydrogenation reaction (hydrogenation reaction) is dominant. Toluene produced by dehydrogenation is hydrogenated again and recycled as organic hydride.

  To purify light hydrocarbons, it is usually necessary to repeat multiple stages of distillation. For example, when producing polypropylene which is a general-purpose resin, propylene gas having a purity of 99.5% or more is used. High purity propylene gas is produced by separating propylene from a mixed fluid containing propylene (first component) and propane (second component). However, separation of propylene and propane is difficult, and ultraprecise distillation of 300 stages or more is required. On the other hand, when a crystalline silica membrane composite is used, propylene can be easily separated.

  In addition to the above, the crystalline silica membrane composite is suitable for separating water from a mixed fluid of water and at least one selected from the group consisting of ethanol, 2-propanol and 2-methyl-1-propanol. ing. For example, separation of water from a mixed fluid containing acetic acid (second component) and water (first component) in the acetic acid production process, ethanol (second component) and water (first component) in the bioethanol production process. Separation of water from mixed fluid, separation of water from mixed fluid containing 2-propanol (second component) and water (first component) used for semiconductor cleaning, 2-methyl- in the bioisobutanol production process The present invention can also be applied to various dehydration processes such as separation of water from a mixed fluid containing 1-propanol (second component) and water (first component).

Next, a method for producing a crystalline silica membrane composite according to the present invention will be described.
First, (i) a step of preparing a porous substrate having a first surface and a second surface and having pores that allow the first surface and the second surface to communicate with each other; and (ii) a CHA on the first surface. And applying a crystalline silica powder having a type crystal structure (hereinafter referred to as seed crystal powder). In order to form Si-CHA in a dense state on the surface of the porous substrate and form a dense Si-CHA film, crystals are preferentially grown on the surface of the porous substrate, not on the liquid phase side. There is a need. For this purpose, it is important to attach a seed crystal powder prepared in advance to the surface of the porous substrate before hydrothermal synthesis. The seed crystal powder may be applied to at least one of the first surface and the second surface.

  The seed crystal powder may be a crystalline silica powder having a CHA type crystal structure, and if the framework can produce a Si-CHA film substantially free of aluminum, the CHA type having a very low aluminum content. Aluminosilicate may be used. However, from the viewpoint of improving steam resistance, chemical resistance, and thermal stability as much as possible, it is desirable to use CHA type pure silica zeolite (Si-CHA) powder as seed crystal powder.

  The method for producing a crystalline silica membrane composite according to the present invention further comprises (iii) a step of preparing an aqueous suspension containing water, a silica material, SDA and HF, and (iv) a porous material in the aqueous suspension. And a step of bringing the surface of the porous base material coated with the seed crystal powder into contact, and growing a crystalline pure silica film having a CHA type crystal structure on the surface by hydrothermal synthesis.

  However, in order to grow crystals preferentially on the surface of the porous substrate, it is important to include crystalline silica powder (seed crystal powder) having a CHA type crystal structure in the aqueous suspension. The seed crystal powder used at this time may be the same as or different from the seed crystal powder applied to the surface of the porous substrate.

  Under the above conditions, it is possible to perform hydrothermal synthesis at a lower temperature than conventional. For example, the porous base material is immersed in an aqueous suspension and crystallized on the surface of the porous base material by hydrothermal synthesis at a temperature of 80 to 150 ° C. or 80 to 130 ° C. for 24 to 168 hours. A pure silica film can be grown. Further, even if the molar ratio (water / Si ratio) of water and silicon atoms contained in the silica material contained in the aqueous suspension is higher than before, crystalline pure silica having a CHA type crystal structure Produces.

  Here, the ratio of the number of Si atoms contained in the seed crystal powder to the total number of Si atoms contained in the silica material is preferably 0.01 to 50%, and preferably 0.1 to 10%. More preferably, it is 0.5 to 5%. By using the seed crystal powder in such a range, it becomes easier to obtain a denser Si—CHA film.

  SDA is a material that serves as a template for forming a crystal structure. For SDA of Si-CHA, it is desirable to use N, N, N-trimethyl-1-adamantanamine hydroxide (TMAdaOH). Thereby, it becomes easy to produce crystalline pure silica having a CHA type crystal structure.

Hereinafter, steps (ii) to (iv) will be described in more detail.
(Preparation of seed crystal powder)
Although the manufacturing method of Si-CHA powder used as seed crystal powder is not particularly limited, for example, Si-CHA powder can be synthesized by the following method. First, SDA (preferably TMAdaOH) and a silicon compound having a hydrolyzable group (preferably tetraethyl orthosilicate) are mixed and sufficiently stirred to prepare a mixture (reaction solution). The mixture is then heated to evaporate moisture until it becomes solid. Next, HF is added to the solid to neutralize the solid. Thereafter, the water content of the solid is adjusted to prepare an aqueous suspension.

The composition of the aqueous suspension is preferably controlled within the following range, for example.
(1) The molar ratio (SDA / Si ratio) between SDA and silicon atoms contained in the aqueous suspension is preferably in the range of 0.5 to 3, preferably in the range of 0.5 to 2.5. It is more preferable that it is in the range of 1.1 to 1.5. By setting the SDA / Si ratio to 0.5 or more, a sufficient amount of SDA is supplied, and the crystallinity of the seed crystal can be improved. The SDA / Si ratio may exceed 3, but only the SDA becomes excessive. By setting the SDA / Si ratio to 3 or less, an increase in manufacturing cost can be suppressed.

  (2) The molar ratio (water / Si ratio) between water and silicon atoms contained in the aqueous suspension is preferably 2 or more from the viewpoint of producing Si-CHA efficiently and in high yield. More preferably, it is 3.2 or more. On the other hand, when the water / Si ratio becomes too large, the concentration of Si atoms in the aqueous suspension becomes thin, and the production rate of Si-CHA tends to be slow. Therefore, the water / Si ratio is preferably 20 or less.

  (3) The molar ratio (SDA / HF ratio) between SDA and HF contained in the aqueous suspension is used to adjust the pH of the reaction solution to near neutrality and to define the CHA type crystal structure. When pure silica zeolite is produced, the reaction solution for performing the hydrothermal synthesis reaction is preferably pH 7-9, for example. When TMAdaOH or the like is used as SDA, it is particularly important to use HF because SDA is a strong alkali. At this time, the SDA / HF ratio is preferably 0.7 to 1.3, and more preferably 0.9 to 1.1. In addition, although the density | concentration of HF is not specifically limited, Usually, the high concentration goods whose HF content is 40-55 mass% are used.

Next, a crystalline product can be obtained by putting the aqueous suspension in a pressure vessel and heating it at 130 to 180 ° C. for 12 to 72 hours to carry out hydrothermal synthesis. This crystal product is a Si-CHA crystal containing SDA, and after washing and drying, pure Si-CHA powder containing no organic matter is obtained by baking at, for example, 500-680 ° C. for 24-72 hours. Can do. A seed crystal powder can be obtained by pulverizing the Si-CHA powder until the average particle size is about 100 to 200 nm.
Here, the average particle diameter is a median diameter in a volume-based particle size distribution, and can be measured by, for example, a laser diffraction particle size distribution measuring apparatus. The same applies hereinafter.

(Preparation of a composite of silica material and SDA)
Next, in order to obtain an aqueous suspension used in forming a pure silica film, first, a composite of a silica material and SDA is prepared. The silica material may be amorphous or crystalline.

  As a raw material of the silica material, that is, a Si element source, colloidal silica containing water may be used, or commercially available fine powder silica (for example, fumed silica) may be used. Alternatively, amorphous or crystalline silica may be prepared by hydrolysis of a silicon compound, which may be pulverized and used as a Si element source. As the silicon compound, a compound having a hydrolyzable group (alkoxy group, halogen group, etc.) may be used. For example, tetraethyl orthosilicate, tetramethyl orthosilicate and the like are preferable.

  It is desirable to use a silicon compound as the Si element source and use TMAdaOH as the SDA that forms the template of the CHA crystal structure. Specifically, a silicon compound may be added to an SDA aqueous solution, and hydrolysis may be gradually advanced with sufficient stirring. Thereafter, if the reaction solution is heated to evaporate the water until it becomes solid, a solid that becomes a precursor of crystalline silica can be obtained. At this time, the water / Si ratio before evaporating the water may be, for example, 6 to 55. Again, the molar ratio of SDA to silicon atoms (SDA / Si ratio) is preferably in the range of 0.5-3, more preferably in the range of 0.5-2.5, A range of 1.1 to 1.5 is particularly preferable.

  Next, the composite of silica material and SDA is obtained by mixing seed crystal powder with the obtained solid. At this time, the ratio of the number of Si atoms contained in the seed crystal powder to the total number of Si atoms contained in the silica material may be 0.01 to 50%. The size of the seed crystal powder particles to be added is not particularly limited, but submicron-sized particles are preferably used so that dissolution by HF can easily occur. Specifically, the seed crystal powder particles are preferably 10 μm or less, more preferably 5 μm or less, and even more preferably 1 μm or less.

(Preparation of aqueous suspension)
The aqueous suspension is prepared by adding water, HF and optionally additional SDA to the composite of silica material and SDA. Here, the aqueous suspension widely includes a wet composition having a relatively low water content to a liquid (dispersion) having a sufficiently high water content.

  In the aqueous suspension, it is desirable to select the molar ratio (water / Si ratio) between water and silicon atoms contained in the silica material so that the Si—CHA film can be obtained efficiently and in a high yield. Usually, Si-CHA is difficult to produce unless the water / Si ratio is very small. On the other hand, when the seed crystal powder is applied to the surface of the porous substrate and the seed crystal powder is also included in the aqueous suspension, the water / Si ratio can be increased. Therefore, the water / Si ratio can be 5 or more, and further 20 or more. On the other hand, when the water / Si ratio becomes too large, the concentration of Si atoms in the aqueous suspension becomes thin, and the production rate of Si-CHA tends to be slow. Therefore, the water / Si ratio is preferably 40 or less, and more preferably 30 or less.

(Formation of crystalline pure silica film)
A Si—CHA film can be formed on the surface of the porous substrate by immersing the porous substrate coated with the seed crystal powder in the aqueous suspension and performing hydrothermal synthesis. The hydrothermal synthesis of Si—CHA usually proceeds at 150 to 200 ° C., but here it proceeds at 80 to 150 ° C., and even 80 to 130 ° C. The synthesis time is, for example, 24 to 168 hours, and it is desirable to control the conditions so as to be completed in 24 to 72 hours.

  Here, the hydrothermal synthesis is a general term for a synthetic reaction of substances generally performed at high temperature and high pressure in the presence of water, and is suitable as a method for producing zeolite. Hydrothermal synthesis is usually performed under pressure of water vapor generated by heating in a sealed container made of fluororesin covered with a stainless steel exterior. The pressure is usually 0.1 to 3 MPa, preferably 0.4 to 2 MPa.

  Since the film product produced by hydrothermal synthesis contains SDA, it is desirable to remove the SDA by baking. Specifically, after washing and drying, the film product is baked at 400 to 800 ° C., preferably 500 to 700 ° C., for example, in the air for 1 to 48 hours, preferably 4 to 12 hours. A crystalline silica film composite having a Si—CHA film from which is removed can be obtained.

  Thereafter, if necessary, the crystalline silica film composite may be treated with a vapor of a volatile silicon compound. For example, the crystalline pure silica film having the crystalline pure silica film after removing the SDA is exposed to vapor of a volatile silicon compound while being heated at 60 to 120 ° C. Silica derived from a volatile silicon compound can be vapor-deposited on the surface. Silica derived from a volatile silicon compound closes the grain boundary pores of crystals constituting the silica film, so that the denseness of the silica film can be improved. In addition, the partial pressure of the volatile silicon compound in the atmosphere containing the volatile silicon compound vapor is not particularly limited, and may be, for example, 10 to 100 kPa. As the volatile silicon compound, alkoxy silicon, silicon halide or the like can be used, and tetramethyl orthosilicate is preferable.

[Example]
EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples.

Example 1
Process (i)
An alumina tube having an average pore diameter of 0.1 μm, an outer diameter of 10 mm, and an inner diameter of 7 mm as a porous base material having a first surface and a second surface and having pores that allow the first surface and the second surface to communicate with each other ( Nippon Zushi Co., Ltd. (hereinafter referred to as alumina substrate) was used. The alumina base material was cut to a length of 100 mm, washed by boiling with ultrapure water, and then used after drying. The outer peripheral surface of the alumina base material corresponds to the first surface, and the inner peripheral surface corresponds to the second surface.

Step (ii)
Using a rubbing method, a crystalline silica powder having a CHA-type crystal structure (seed crystal powder) synthesized in the following manner is applied to the central 50 mm width portion of the outer peripheral surface (first surface) of the alumina substrate. And applied.

(Synthesis of seed crystal powder)
Here, Si-CHA powder was synthesized according to the method described in Non-Patent Document 3 (MJDiaz-Cabanas et.al., Chemical Comunications, Royal Society of Chemistry, 1881 (1998)). First, 30.2 g of TMAdaOH aqueous solution (TMAdaOH content 24.9% by mass, manufactured by SACHEM, Inc.) was placed in a 100 mL container made of fluororesin, and 15.0 g of tetraethyl orthosilicate (Wako Pure Chemical Industries, Ltd.). Yakuhin Co., Ltd.) was added and allowed to stir overnight. Thereafter, the reaction solution was heated to evaporate water until it became solid. To the solid after concentration, 1.5 g of HF (46.9 mass%, manufactured by Wako Pure Chemical Industries, Ltd.) was added little by little to neutralize the solid. Thereafter, the moisture content was adjusted to prepare a solid precursor with Si / TMAdaOH / HF / H ₂ O = 1.0 / 0.5 / 0.5 / 3 (molar ratio).

  The solid precursor was placed in a stainless steel pressure resistant vessel with a fluororesin inner cylinder having an internal volume of 100 ml and heated at 150 ° C. for 40 hours for hydrothermal synthesis. The product was then filtered, washed and dried. The washed product was baked at 580 ° C. for 24 hours to obtain Si—CHA powder. The average particle size of the obtained powder was about 10 μm. This Si-CHA powder was wet pulverized in an agate mortar to obtain a seed crystal powder having an average particle diameter of about 200 nm.

Step (iii)
In the following manner, a composite of silica material and SDA was prepared, and HF and water were added thereto to prepare an aqueous suspension.

(Preparation of a composite of silica material and SDA)
In a 100 mL container made of fluororesin, 48.4 g of TMAdaOH aqueous solution (TMAdaOH content 24.9% by mass, manufactured by SACHEM, Inc.) was placed, and 15.0 g of tetraethyl orthosilicate, which is a Si element source. (Wako Pure Chemical Industries, Ltd.) was added and allowed to stir overnight. Thereafter, the reaction solution was heated to evaporate water until it became solid, and a concentrated solid was obtained. 0.43 mg of the seed crystal powder was added to the obtained solid to obtain a composite of silica material and SDA. At this time, the ratio of the number of Si atoms contained in the seed crystal powder to the total number of Si atoms contained in the silica material was 0.01%.

(Preparation of aqueous suspension)
To the above composite, 3.04 g of HF (HF content 46.9% by mass, manufactured by Wako Pure Chemical Industries, Ltd.) was added little by little to neutralize the solid. Thereafter, the water content was adjusted to prepare an aqueous suspension with Si / TMAdaOH / HF / H ₂ O = 1.0 / 0.8 / 0.8 / 5.7 (molar ratio).

Step (iv)
Next, the alumina substrate having the first surface coated with the first seed crystal powder is immersed in the aqueous suspension, and in a stationary state, heated at 150 ° C. for 72 hours to perform hydrothermal synthesis. A silica film was grown on the surface. Thereafter, the membrane product containing the silica membrane was washed with ultrapure water, dried, and fired at 500 ° C. in an air atmosphere to obtain a silica membrane composite. The temperature increase and decrease rate during firing was 0.5 ° C./min, and the holding time was 120 hours.

(Comparative Example 1)
A silica membrane composite was produced in the same procedure as in Example 1 except that 0.43 mg of seed crystal powder was not added to the solid before neutralization with HF.

(Example 2)
A silica membrane composite was produced in the same procedure as in Example 1 except that the hydrothermal synthesis temperature was changed to 120 ° C. and the synthesis time was changed to 168 hours.

(Comparative Example 2)
A silica membrane composite was produced in the same procedure as in Comparative Example 1 except that the hydrothermal synthesis temperature was changed to 120 ° C. and the synthesis time was changed to 168 hours.

(Example 3)
A silica membrane composite was produced in the same procedure as in Example 1 except that the hydrothermal synthesis temperature was changed to 80 ° C. and the synthesis time was changed to 168 hours.

Example 4
The composition of the aqueous suspension was changed to Si / TMAdaOH / HF / H ₂ O = 1.0 / 0.8 / 0.8 / 28.5, the hydrothermal synthesis temperature was 120 ° C., and the synthesis time was changed to 168 hours. A silica membrane composite was produced in the same procedure as in Example 1 except that.

(Example 5)
The silica membrane composite produced in the same manner as in Example 2 was housed in an airtight container together with an open container containing liquid tetramethyl orthosilicate (TMOS), and the silica membrane composite and TMOS were heated at 80 ° C. for 2 hours. did. At this time, the silica film is exposed to the vapor of TMOS, and it is considered that TMOS-derived silica is generated at the crystal grain boundary.

(Example 6)
A silica membrane composite was produced in the same procedure as in Example 1 except that 4.3 mg of seed crystal powder was added to the solid before neutralization with HF.

(Evaluation of membrane product structure)
For the film products of Examples 1 to 6 and Comparative Examples 1 and 2, the structure was determined using an X-ray diffractometer (RINT2000, manufactured by Rigaku Corporation) and a scanning electron microscope (SU9000, manufactured by Hitachi High-Tech Corporation). evaluated.

(X-ray diffraction measurement)
In the X-ray diffraction measurement, it was confirmed that the diffraction patterns of the film products of Examples 1 to 6 and Comparative Example 1 (other than Comparative Example 2) coincided with the CHA type topology. When the relative intensity of the main peak was evaluated, the (100) / (2-10) ratio (peak intensity around 2θ = 9.6 ° / peak intensity around 2θ = 20.7 °), (100) / (10 -1) ratio (2θ = peak intensity around 9.6 ° / peak intensity around 2θ = 12.9 °), (100) / (111) ratio (2θ = peak intensity around 9.6 ° / 2θ = The peak intensity around 18.0 ° showed a relative intensity comparable to that of the seed crystal powder. From the above, it was found that the film products of Examples 1 to 6 and Comparative Example 1 were crystalline silica films and included Si—CHA films having random orientation.

  The film product of Comparative Example 2 was confirmed to have an amorphous structure, and it was found that no Si—CHA film was formed. On the other hand, in Example 2 having the same temperature and the same composition and Example 3 having a low synthesis temperature, a Si—CHA film was obtained. From the above, it has been found that adding Si-CHA seed crystal powder to an aqueous suspension has an effect of lowering the synthesis temperature of Si-CHA. Moreover, since the Si—CHA film was obtained also in Example 4 where the water / Si ratio was 28.5, high water / Si was obtained by adding Si—CHA seed crystal powder to the aqueous suspension. It was confirmed that the Si—CHA film could be prepared even by the ratio.

(Scanning electron microscope observation)
The film products of Comparative Example 1 and Examples 1 to 4 were crushed, and the surface and cross section were observed with a scanning electron microscope (SEM). FIG. 3A shows an SEM image of the surface of the film product of Comparative Example 1. 3B to 3E show SEM images of the surfaces of the film products of Examples 1, 2, 3, and 4, respectively. FIG. 3F is an SEM image of the surface of the alumina base material immediately after the seed crystal powder is applied.

  It can be seen that the film product of Comparative Example 1 has a structure in which relatively large crystal grains are deposited, and has a film structure with many defects (FIG. 3A). In the cross-sectional observation, a deposited layer of crystal particles having a thickness of about 20 μm was observed. On the other hand, the film product of Example 1 had a dense film structure in which smaller crystals were connected to each other, and pinholes and cracks could not be confirmed within the observation range (FIG. 3B). In cross-sectional observation, a dense polycrystalline layer having a thickness of about 5 μm was observed. The same evaluation was performed on the silica films of Examples 2 to 4, and it was confirmed that there were no pinholes and cracks (FIGS. 3C to 3E).

(EDX measurement)
When the cross section of the film product (crystalline silica film) of Example 1 was evaluated by EDX, the Si-CHA film composed only of silicon and oxygen is about 2 μm from the film surface. It was confirmed that a composite layer of the porous substrate was formed. FIG. 4A shows an SEM image of a cross section of the film product of Example 1. FIG. In FIG. 4B, the conceptual diagram of the cross-section of the film | membrane product of Example 1 is shown. On the other hand, the thickness of the silica film of Example 2 was about 4 μm, and the Si-CHA film was from the film surface to about 3 μm. From the above, it was found that the thickness of the Si—CHA film can be increased by lowering the hydrothermal synthesis temperature. This is presumably because the dissolution of the porous substrate accompanying hydrothermal synthesis is suppressed and the thickness of the composite layer is reduced.

(Permeance measurement)
The permeance ratio of the probe gas is used as an index for evaluating the denseness of the film. In the case of a dense film structure in which gas molecules are difficult to permeate the crystal grain boundary, the gas molecule permeance ratio is larger than the reciprocal of the square root of the molecular weight ratio (Knudsen coefficient ratio). In the case of hydrogen and sulfur hexafluoride, the Knudsen coefficient ratio is 8.54, and the higher this value, the denser the film.

  First, an apparatus for performing a transmission test will be described with reference to FIG. The apparatus 100 fixes the cylindrical silica membrane composite 10 and both ends of the silica membrane composite 10 and exposes only the central 50 mm width portion (silica membrane forming portion 10s) on the outer peripheral surface side of the alumina base material. A pair of hollow supports 120a and 120b to be made, a chamber 130 covering the silica film forming part 10s, and a heating device 140 for controlling the temperature in the chamber 130 are provided. One end of one support 120a is closed in the illustrated example, and a temperature sensor (thermocouple) 150 is inserted. The hollow of the other support 120 b communicates with the soap film flow meter 160. The inside of the chamber 130 is isolated from the outside air, and the probe gas can be introduced from the gas introduction port 171. A part of the probe gas introduced into the chamber 130 passes through the silica film forming unit 10 s and is introduced into the soap film flow meter 160. The pressure in the chamber 130 is controlled by a back pressure valve 180. The composition of the gas introduced into the soap film flow meter 160 can be confirmed by the gas chromatography 190 provided therewith.

  Using the apparatus 100, the membrane products produced in Examples 1, 2, 5, 6 and Comparative Example 1 were subjected to various probe gas permeation tests to determine probe gas permeance (permeation rate or transmittance). Calculated.

  Before the permeation test, the silica membrane composite 10 was pretreated by heating at 200 ° C. for 12 hours under an inert gas (Ar) flow. Next, the probe gas was introduced from the gas supply source 170 into the chamber 130 through the gas inlet 171 while controlling the temperature in the chamber 130 and the hollow of the silica membrane composite 10 to 40 ° C. At this time, the supply pressure (outer peripheral surface or first surface side) pressure of the silica membrane composite is 0.2 MPa, and the permeation side (inner peripheral surface or second surface side) pressure of the silica membrane composite is 0.1 MPa (atmospheric pressure) ) And the permeance of the probe gas was calculated by measuring the gas flow rate on the permeate side with a soap film flow meter 160.

The gas permeance was calculated from the following formula: Q = A / {(P1−P2) · S · t}. Where Q is probe gas permeance (mol / m ² · s · Pa), A is probe gas permeation (mol), P 1 is supply side pressure (Pa), P 2 is permeation side pressure (Pa), S represents the apparent area (m ² ) of the silica film, and t represents the measurement time (seconds) when the permeation amount is A.
Hydrogen, carbon dioxide, nitrogen, methane, and sulfur hexafluoride were used as the probe gas. The obtained permeance and permeance ratio (H ₂ / SF ₆ and CO ₂ / N ₂ ) are shown in Table 1.

  Table 1 shows the corresponding data of the Si-MFI film (Reference Example 1) described in Non-Patent Document 2 (S. Rezai et al., Micropor. Mesopor. Mater., 108, 136-142 (2008)). The corresponding data of the Si-DDR film (Reference Example 2) described in Patent Document 2 (Japanese Patent Laid-Open No. 2004-105942) is also shown.

  Table 1 further shows CHA type aluminosilicate according to the method described in Non-Patent Document 1 (N. Hosinov et al., J. Mater. Chem. A, 2, 13083-13092 (2014)). The result of producing a membrane composite (Reference Example 3) and conducting a permeation test in the same manner as described above is also shown.

Since the permeance ratio: H ₂ / SF ₆ of the film product of Comparative Example 1 is generally coincident with the Knudsen coefficient ratio, it is considered to be a film structure having many defects, which coincides with the result of SEM image observation. On the other hand, since the film products of Example 1 and Example 2 have a permeance ratio: H ₂ / SF ₆ of more than 200, it can be seen that they are dense films.

  When the gas permeation performance is compared with other crystalline pure silica films (Reference Examples 1 and 2), the Si-CHA films of Examples 1 and 2 are the Si-MFI film of Reference Example 1 and the Si-DDR of Reference Example 2. It can be seen that the separation membrane has both gas permeation rate and selectivity compared to the membrane.

The aluminosilicate film having the CHA type crystal structure of Reference Example 3 is a film having aluminum in the framework and containing sodium ions. Therefore, although the film product of Reference Example 3 has the same crystal structure as the film product of Example 2, the permeance ratio: H ₂ / SF ₆ was less than half that of Example 2. Since the Si-CHA film does not contain charge-compensating cations in the framework, it is considered that the pore volume is large and high permeance is exhibited.

(Water vapor exposure test)
The film products of Example 1 and Reference Example 3 were evaluated for water vapor resistance. The inside of the apparatus including the film product for which the permeance measurement was completed was heated to 150 ° C., and the film product was exposed to a mixed gas of water / argon = 90: 10 (molar ratio) for 5 hours. At this time, the gas supply amount was 5 mmol / min in total, the supply side pressure was 0.2 MPa, and the permeation side pressure was 0.1 MPa (atmospheric pressure). After the water vapor exposure, the permeance ratio at 40 ° C .: H ₂ / CO ₂ was measured again to evaluate the change in gas permeation performance. The results are shown in Table 2.

  The Si—CHA film of Example 1 was not confirmed to have a decrease in gas permeation performance before and after exposure to water vapor. On the other hand, the membrane product of Reference Example 3 was confirmed to have a decrease in gas permeation performance, and after exposure to water vapor, a decrease in permeance of 20% for hydrogen and 29% for carbon dioxide was confirmed. When the film product of Reference Example 3 was crushed and subjected to SEM observation, it was confirmed that a part of the film surface was amorphized. The surface of the aluminosilicate film is hydrophilic and easily adsorbs water vapor. It is considered that the aluminum portion in the framework was hydrolyzed by the adsorbed water, so that the amorphization progressed. Since the Si—CHA film retains its crystal structure even when exposed to heated steam, it can be used in harsh environments that cannot be applied to an aluminosilicate film.

(Hydrogen / toluene separation test)
The Si-CHA membranes of Example 1 and Example 5 were subjected to a test assuming hydrogen separation from a hydrogen / toluene mixed gas generated by the dehydrogenation reaction of methylcyclohexane. The apparatus 100 shown in FIG. 5 was used for the test. As a test gas, liquid toluene was supplied to the vaporizer 173 via the pump 172 and vaporized at 200 ° C. At that time, hydrogen was introduced into the vaporizer 173 from a hydrogen line and supplied to the chamber 130 as a mixed gas of hydrogen / toluene = 98/2 (molar ratio). The hydrogen / toluene ratio was controlled by the amount of toluene supplied. The measurement temperature was 120 ° C., the total gas supply amount was 40 mmol / min, the supply side pressure was 0.3 MPa, and the permeation side pressure was 0.1 MPa (atmospheric pressure). The gas flow rate on the permeate side was measured with a soap film flow meter 160, and the hydrogen / toluene concentration ratio was measured with a gas chromatography 190. The results of the hydrogen / toluene separation test are shown in Table 3.

In the Si—CHA film of Example 1, the hydrogen concentration on the permeate side was 99.9% or higher. Further, a hydrogen permeance of 8.8 × 10 ⁻⁷ mol / m ² · s · Pa, a permeance ratio of 42 hydrogen / toluene (TOL), and a hydrogen / toluene separation factor of 28 were shown. On the other hand, in the Si—CHA film of Example 5, the hydrogen concentration on the permeate side was 99.99% or more, hydrogen permeance of 7.6 × 10 ⁻⁷ mol / m ² · s · Pa, hydrogen of 230 A toluene permeance ratio and a hydrogen / toluene separation factor of 150 were shown. It was confirmed that hydrogen / toluene could be separated with high hydrogen permeance by applying the Si-CHA film.

(Carbon dioxide / methane separation test)
The Si—CHA membrane of Example 6 was subjected to a carbon dioxide separation test from a carbon dioxide / methane mixed gas. In the test, a separation test was performed using the apparatus 100 shown in FIG. 5 in the same manner as the hydrogen / toluene separation test. As the test gas, each gas was introduced from a carbon dioxide and methane line, and supplied to the chamber 130 as a mixed gas of carbon dioxide / methane = 50/50 (molar ratio). The measurement temperature was room temperature (26 ° C.), the gas supply amount was 134 mmol / min in total, the supply side pressure was 0.2 to 0.5 MPa, and the permeation side pressure was 0.1 MPa (atmospheric pressure). The gas flow rate on the permeate side was measured with a soap film flow meter 160, and the carbon dioxide / methane concentration ratio was measured with a gas chromatography 190. The results of the carbon dioxide / methane mixed gas separation test are shown in Table 4.

At a supply pressure of 0.2 MPa, a carbon dioxide permeance of 39.6 × 10 ⁻⁷ mol / m ² · s · Pa and a carbon dioxide / methane permeance ratio of 130 were shown. Although the carbon dioxide permeance tended to decrease with increasing supply pressure, the carbon dioxide permeance was extremely high. At a supply pressure of 0.5 MPa, the carbon dioxide permeance was 19.3 × 10 ⁻⁷ mol / m ² · s · Pa, and the carbon dioxide / methane permeance ratio was 45. The decrease in separation performance caused by the pressure increase is considered to be caused by concentration polarization, and it is considered that concentration polarization can be avoided by optimizing the shape of the chamber 130 and the gas introduction method. From the above, it was shown that carbon dioxide can be separated at high speed by using the Si—CHA film of the present invention.

(Propylene / propane separation test)
The adsorption isotherm of propylene and propane of the Si-CHA powder prepared in step (ii) of Example 1 was measured. Further, the permeance of propylene and propane of the Si-CHA film was measured.

<Adsorption test>
The adsorption isotherm of propane and propylene was measured using a high-accuracy gas adsorption amount measuring device (BELSORPmax) manufactured by Microtrac Bell. The equilibrium judgment condition was that the pressure change for 500 seconds was less than 0.3%. FIG. 6A shows the results when using Si—CHA powder, and FIG. 6B shows the results when using the CHA type aluminosilicate powder according to Reference Example 3.

As shown in FIG. 6A, Si-CHA hardly adsorbed propane, and the adsorption amount ratio at 100 kPa: C ₃ H ₆ / C ₃ H ₈ was 200. On the other hand, as shown in FIG. 6B, the CHA type aluminosilicate adsorbed propane, and the adsorption amount ratio C ₃ H ₆ / C ₃ H _{8 at} 100 kPa was 2. As mentioned above, it became clear that Si-CHA shows selective adsorptivity with respect to propylene. Black circles and squares indicate adsorption from 0 kPa to 100 kPa, and white circles and squares indicate desorption from 100 kPa to 0 kPa.

<Permeance measurement>
For the silica membrane composite produced in Example 5, the permeance of propylene and propane was measured under the same conditions as in Table 1. The results are shown in Table 5. Propylene showed 3.8 times higher permeance than propane. Since CHA type pure silica easily adsorbs propylene, it is considered that the permeance is higher than that of propane. Considering the adsorption selectivity, it is considered that the propylene / propane separation performance can be further improved by improving the denseness of the silica membrane.

(Water / alcohol separation test)
A dehydration test by pervaporation was performed using an aqueous solution with an ethanol content of 90% by volume and an aqueous solution with an isopropanol content of 90% by mass.
First, an apparatus for performing a dehydration test will be described with reference to FIG. The apparatus 200 includes a chamber 230 that contains a mixed solution 201 of alcohol and water, a sealing body 231 that seals the opening of the chamber 230, and a cylinder that is immersed perpendicularly to the liquid level of the mixed solution 201 in the chamber 230. A silica membrane composite 10, a lid 210 that closes one end located in the liquid of the silica membrane composite 10, and a cylinder 220 that is connected to the other end of the silica membrane composite 10 and penetrates the sealing body 231. The pipe 260 into which the steam introduced into the cylindrical body 220 from the hollow of the silica membrane composite 10 is introduced, the cold trap 270 for cooling the steam introduced from the pipe 260, the cold trap 270 and the pipe 260, A pump 280 for depressurizing the inside of the cylindrical body 220 and the hollow inside of the silica membrane composite 10. A heating device 240 that controls the temperature of the solution in the chamber 230 is provided around the chamber 230. A temperature sensor 250 is immersed in the mixed solution 201, and the temperature sensor 250 communicates with the heating device 240.

  Using the apparatus 200, the silica membrane composite produced in Example 2 was subjected to a permeation test of an ethanol aqueous solution and an isopropanol aqueous solution, and the amount of water permeation and the separation factor were calculated. Specifically, the alcohol aqueous solution is heated to a predetermined temperature while being stirred using a stirrer 232 and a stirrer 233, and the inside of the silica membrane composite 10 is decompressed to 20 Pa or less by a pump to permeate the silica membrane. The steam was condensed in a cold trap. Thereafter, the mass of the condensate and the water concentration were measured, and the amount of permeated water and the separation factor were calculated. The water separation factor indicates the water concentration of the condensate / the alcohol concentration of the condensate) / (the water concentration of the alcohol aqueous solution / the alcohol concentration of the alcohol aqueous solution). The water concentration was measured using a Karl Fischer moisture meter (manufactured by Hiranuma Sangyo Co., Ltd.). The results are shown in Table 6.

  Table 6 also shows the results of the permeation test of the Si-DDR film described in Patent Document 3 (International Publication No. 2007/119286 pamphlet) as Reference Example 4.

  From Table 6, the Si-CHA film showed a higher water permeation amount than the Si-DDR film. This was attributed to the high pore volume of Si-CHA and was found to show high molecular permeability not only in the gas system but also in the liquid system.

  The crystalline silica membrane composite according to the present invention is excellent in water vapor resistance, chemical resistance, and thermal stability, and has an excellent molecular sieving ability. Therefore, it can be used for various fluid separation methods and separation purification apparatuses. I can expect.

  10, 10A: crystalline silica film composite, 10s: silica film forming part, 11: first surface, 12: second surface, 13, 13A: porous substrate, 14, 14A: crystalline pure silica film, 100 : Apparatus for performing gas permeation test, 120a, 120b: support, 130: chamber, 140: heating device, 150: temperature sensor, 160: soap film flow meter, 170: gas supply source, 171: gas inlet, 172: Pump: 173: vaporizer, 180: back pressure valve, 190: gas chromatography, 200: device for performing dehydration test by pervaporation separation, 201: mixed solution, 210: lid, 220: cylinder, 230: chamber, 231 : Sealing body, 232: Stirrer, 233: Stirrer, 240: Heating device, 250: Temperature sensor, 260: Pipe, 270: Cold trap, 280: Pump

[0006]
Dissolves from the porous substrate and mixes with the crystalline silica.
[0021]
The indications such as CHA, DDR, and MFI are codes that define the structure of zeolite defined by International Zeolite Association (IZA). For example, CHA-type zeolite is a zeolite having a crystal structure equivalent to chabazite. It is shown that.
[0022]
The permeance ratio is a permeation rate (permeance: mol / m ² · s · Pa) or permeation ratio measured for two kinds of fluids, and serves as an index indicating the selectivity of the separation membrane. When the density of the pure silica film decreases and the number of defects in the film increases, the permeance ratio: H ₂ / SF ₆ approaches the Knudsen coefficient ratio. In other words, the larger the permeance ratio, the denser the pure silica film.
[0023]
A dense pure silica crystal having a CHA type crystal structure has a large pore volume, and can achieve a pore volume of, for example, 0.25 cm ³ / g or more, further 0.3 cm ³ / g or more. Since the permeance of the fluid is increased due to the large pore volume, the fluid can be separated and purified with a pure silica membrane efficiently.
[0024]
The permeance of H ₂ by the pure silica film exceeds, for example, 5 × 10 ⁻⁷ mol / m ² · s · Pa, and can achieve 1 × 10 ⁻⁶ mol / m ² · s · Pa or more. However, an excessively high permeance means that the denseness of the pure silica film is low and there are many defects. The permeance of H ₂ is, for example, less than 1 × 10 ⁻⁵ mol / m ² · s · Pa, and preferably 5 × 10 ⁻⁶ mol / m ² · s · Pa or less.
[0025]
Since the pure silica membrane has high selectivity, the permeance ratio of CO ₂ and N ₂ : CO ₂ / N ₂ is also large, for example, exceeding 2, and being able to achieve 3 or more or 5 or more.
[0026]
The thickness of the pure silica film is not particularly limited, but it is 10 μm or less from the viewpoint of forming a film with small defects and realizing high selectivity.

Claims (16)

A porous substrate;
A crystalline pure silica film formed on the surface of the porous substrate,
The pure silica film has a CHA-type crystal structure;
Permeance ratio between H ₂ and SF ₆ : Crystalline silica membrane composite with H ₂ / SF ₆ exceeding 10. The crystalline silica membrane composite according to claim 1, wherein the permeance ratio of CO ₂ and N ₂ : CO ₂ / N ₂ exceeds 2. The crystallinity according to claim 1 or 2, wherein the permeance of H ₂ is more than 5 × 10 ^-7 mol / m ² · s · Pa and less than 1 × 10 ^-5 mol / m ² · s · Pa. Silica membrane composite.   The crystalline silica membrane composite according to any one of claims 1 to 3, wherein the pure silica membrane has a thickness of 10 µm or less.   The material of the porous substrate is at least one selected from the group consisting of silica, alumina, mullite, zirconia, cordierite, titania, silicon nitride, silicon carbide, stainless steel, copper, aluminum, and titanium. Item 5. The crystalline silica membrane composite according to any one of Items 1 to 4.   The porous substrate has a first surface and a second surface, and has pores that allow the first surface and the second surface to communicate with each other, and is selected from the first surface and the second surface The crystalline silica film composite according to any one of claims 1 to 5, wherein the pure silica film is formed on at least one of the surfaces. (I) preparing a porous substrate having a first surface and a second surface, and having pores for communicating the first surface and the second surface;
(Ii) applying a crystalline silica powder having a CHA-type crystal structure to at least one selected from the first surface and the second surface;
(Iii) preparing an aqueous suspension comprising water, silica material, organic structure directing agent and hydrofluoric acid;
(Iv) Crystalline pure silica having a CHA-type crystal structure brought into contact with the aqueous suspension by contacting the surface of the porous base material coated with the crystalline silica powder and hydrothermal synthesis on the surface. Growing a film, and
A method for producing a crystalline silica membrane composite, wherein the silica material comprises a crystalline silica powder having a CHA type crystal structure.   The crystal according to claim 7, wherein a ratio of the number of Si atoms contained in the crystalline silica powder having the CHA-type crystal structure to the total number of Si atoms contained in the silica material is 0.01 to 50%. For producing a porous silica membrane composite.   The method for producing a crystalline silica membrane composite according to claim 7 or 8, wherein the organic structure directing agent comprises N, N, N-trimethyl-1-adamantanamine amine hydroxide.   The crystalline pure silica film grown in step (iv) is baked to remove the structure directing agent, and then the crystalline pure silica film is exposed to vapor of a volatile silicon compound to form the crystalline The method for producing a crystalline silica membrane composite according to any one of claims 7 to 9, wherein a pure silica membrane is reacted with the volatile silicon compound. A fluid separation method for separating a specific component from a mixed fluid using the crystalline silica membrane composite according to claim 6,
(I) A mixed fluid containing a first component and a second component having different permeances with respect to the pure silica film is supplied to a first space communicating with the pores on one of the first surface and the second surface. Process,
(Ii) recovering the permeated fluid that has permeated the silica membrane from the second space communicating with the pores on the other of the first surface and the second surface, and recovering the non-permeated fluid from the first space. And a fluid separation method. The first component is hydrogen or carbon dioxide;
The fluid separation method according to claim 11, wherein the second component is at least one selected from the group consisting of methane, carbon monoxide, nitrogen, and C ₂ or more hydrocarbons. The first component is hydrogen;
The fluid separation method according to claim 11, wherein the second component is at least one selected from the group consisting of toluene and methylcyclohexane. The first component is propylene;
The fluid separation method according to claim 11, wherein the second component is propane. The first component is water;
The fluid separation method according to claim 11, wherein the second component is acetic acid. The first component is water;
The fluid separation method according to claim 11, wherein the second component is at least one selected from the group consisting of ethanol, 2-propanol, and 2-methyl-1-propanol.