JP6413283B2 - Method for producing porous support-zeolite membrane composite - Google Patents

Description

  The present invention relates to a method for producing a porous support-zeolite membrane composite. The porous support-zeolite membrane composite obtained by the production method of the present invention permeates and separates a highly permeable substance from a gas or liquid mixture composed of a plurality of components, and concentrates the low permeable substance. It is something that can be done.

Conventionally, separation or concentration of a gas or liquid mixture containing an organic compound is performed by distillation, azeotropic distillation, solvent extraction / distillation, adsorbent, etc., depending on the properties of the target substance. . However, these methods have drawbacks that they require a lot of energy or have a limited application range for separation and concentration.
In recent years, membrane separation and concentration methods using membranes such as polymer membranes and zeolite membranes have been proposed as separation methods instead of these methods. Polymer membranes such as flat membranes and hollow fiber membranes are excellent in processability, but have the disadvantage of low heat resistance. In addition, polymer membranes have low chemical resistance, and many of them swell when contacted with organic compounds such as organic solvents and organic acids, so that the range of application for separation and concentration is limited.

  Further, the zeolite membrane is usually used for separation and concentration as a zeolite membrane composite in which zeolite is formed into a membrane on a support. For example, the organic compound can be separated and concentrated by bringing a mixture of the organic compound and water into contact with the zeolite membrane composite and selectively permeating water. Separation and concentration using membranes of inorganic materials can reduce the amount of energy used compared to separation by distillation or adsorbent, and can be separated and concentrated in a wider temperature range than polymer membranes. It can also be applied to the separation of mixtures.

  As a separation method using a zeolite membrane, for example, Patent Document 1 uses a type A zeolite membrane composite to selectively permeate water to concentrate alcohol, and Patent Document 2 uses a mordenite zeolite membrane composite. A method of selectively permeating water from a mixed system of alcohol and water and concentrating the alcohol. In Patent Document 3, water is selectively permeated from a mixed system of acetic acid and water using a ferrierite-type zeolite membrane composite. A method for separating and concentrating acetic acid has been proposed.

  Patent Document 4 proposes a method for producing a zeolite membrane composite by forming a zeolite membrane by hydrothermal synthesis and then immersing it in a solution containing a Si compound such as tetraethoxysilane. It is considered that by immersing in a solution containing a Si compound, a layer containing a large amount of the Si compound is formed on the zeolite membrane surface, the hydrophilicity of the membrane surface is improved, and the separation performance can be improved. Further, it is described that the effect of blocking fine defects existing on the membrane surface can be obtained as a secondary effect by modifying the zeolite membrane surface with a Si compound.

JP-A-7-185275 JP 2003-144871 A JP 2000-237561 A International publication WO2013 / 125661 pamphlet

However, even when a zeolite membrane composite obtained by a conventional production method is used for separation of a gas or liquid mixture, sufficient separation performance may not be obtained.
Therefore, the present invention aims to improve the separation performance when using the zeolite membrane composite for separation of a gas or liquid mixture, and provides a method for producing a zeolite membrane composite having such a high separation performance. This is the issue.

As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be solved by controlling the temperature of the support when the zeolite membrane surface is surface-treated with a Si compound or the like. Reached.
That is, the present invention is a method for producing a porous support-zeolite membrane composite obtained by forming a zeolite membrane on a porous support and then surface-treating the zeolite membrane, wherein the zeolite membrane is formed. The present invention resides in a method for producing a porous support-zeolite membrane composite, characterized in that the surface treatment is performed at a temperature of 50 ° C. or higher.

  According to the present invention, when separating and concentrating a specific substance from a gas or liquid mixture composed of a plurality of components, a zeolite membrane having a sufficiently large processing amount for practical use and sufficient separation performance is obtained. A porous support-zeolite membrane composite is provided. This zeolite membrane composite achieves both sufficient throughput and separation performance. By using this as a separation means, it is possible to separate highly permeable substances and concentrate the mixture from a gas or liquid mixture consisting of multiple components. It becomes.

Schematic diagram of measuring device used for gas separation Schematic diagram of the measuring device used for the vapor permeation method

Hereinafter, embodiments of the present invention will be described in more detail. However, the description of the constituent elements described below is an example of embodiments of the present invention, and the present invention is not limited to these contents. Various modifications can be made within the scope of the gist.
The method for producing a porous support-zeolite membrane composite of the present invention is a porous support-zeolite membrane composite obtained by forming a zeolite membrane on a porous support and then surface-treating the zeolite membrane. The surface treatment is performed by setting the temperature of the porous support on which the zeolite membrane is formed to 50 ° C. or higher.

First, the zeolite membrane formed on the porous support, which is a feature of the present invention, will be described.
In the present specification, the porous support and the zeolite membrane formed thereon may be referred to as “zeolite membrane composite”, which may be abbreviated as “membrane composite”. Further, the “porous support” may be abbreviated as “porous support” or “support”.

<Porous support>
In the present invention, the porous support has a chemical stability that allows the zeolite to be crystallized into a film on the surface thereof, and is a support made of an inorganic porous material (inorganic porous support). It can be anything. For example, sintered ceramics (ceramics support) such as silica, α-alumina, γ-alumina, mullite, zirconia, titania, yttria, silicon nitride, silicon carbide, sintered metals such as iron, bronze, and stainless steel, glass And carbon moldings.

Among these porous supports, there are inorganic porous supports (ceramic supports) including sintered ceramics, which are solid materials whose basic components or most of them are composed of inorganic nonmetallic substances. preferable. If this support is used, a part of the support is zeoliticized during the synthesis of the zeolite membrane, thereby improving the adhesion at the interface.
Specific examples include a ceramic sintered body (ceramic support) containing silica, α-alumina, γ-alumina, mullite, zirconia, titania, yttria, silicon nitride, silicon carbide, and the like. Among them, an inorganic porous support containing at least one of alumina, silica, and mullite is preferable. When these supports are used, partial zeolitization is easy, so that the bond between the support and the zeolite becomes strong, and a dense membrane with high separation performance is easily formed.

  The shape of the porous support is not particularly limited as long as it can effectively separate a gas mixture or a liquid mixture. Specifically, for example, a flat plate shape, a tubular shape (for example, a cylindrical tubular shape, a prismatic tubular shape), a honeycomb shape, etc. (For example, a honeycomb having a large number of cylindrical, columnar, and prismatic holes), a monolith, and the like. Among these, a tubular support is particularly preferable, and a cylindrical tubular support is particularly preferable.

In the present invention, zeolite is formed into a film on such a porous support, that is, on the surface of the support. The surface of the support may be any surface or a plurality of surfaces depending on the shape of the support. For example, in the case of a cylindrical tubular support, it may be the outer surface or the inner surface, and in some cases both the outer and inner surfaces.
The average pore diameter on the surface of the porous support is not particularly limited, but those having a controlled pore diameter are preferred. The average pore diameter on the surface of the support is usually 0.02 μm or more, preferably 0.05 μm or more, more preferably 0.1 μm or more, and usually 20 μm or less, preferably 10 μm or less, more preferably 5 μm or less. If the average pore diameter is too small, the amount of permeation tends to be small, and if it is too large, the strength of the support itself is insufficient, and the proportion of pores on the surface of the support increases, making it difficult to form a dense zeolite membrane. Tend.

  The average thickness (wall thickness) of the porous support is usually 0.1 mm or more, preferably 0.3 mm or more, more preferably 0.5 mm or more, usually 7 mm or less, preferably 5 mm or less, more preferably 3 mm. It is as follows. The support is used to give mechanical strength to the zeolite membrane, but if the average thickness of the support is too thin, the zeolite membrane composite will not have sufficient strength and There is a tendency to weaken. If the average thickness of the support is too thick, the diffusion of the permeated material tends to be poor and the permeability tends to be low.

The porosity of the porous support is usually 20% or more, preferably 25% or more, more preferably 30% or more, and usually 70% or less, preferably 60% or less, more preferably 50% or less. The porosity of the support influences the permeation flow rate when the gas is separated, and if it is less than the lower limit, it tends to inhibit the diffusion of the permeate, and if it exceeds the upper limit, the strength of the support tends to decrease.
The surface of the porous support may be polished with a file or the like as necessary. The surface of the porous support means the surface portion of the inorganic porous support that crystallizes the zeolite, and any surface of each shape may be used as long as the surface is a plurality of surfaces. Also good. For example, in the case of a cylindrical tubular support, it may be the outer surface or the inner surface, and in some cases both the outer and inner surfaces.

<Zeolite membrane composite>
In the present invention, a zeolite membrane is formed on the porous support to obtain a zeolite membrane composite.
Components other than zeolite include inorganic binders such as silica and alumina, organic compounds such as polymers, or materials containing Si atoms that modify the zeolite surface as detailed below, or reactants, etc. May be included. Further, the zeolite membrane in the present invention may partially contain an amorphous component.

The thickness of the zeolite membrane is not particularly limited, but is usually 0.1 μm or more, preferably 0.6 μm or more, more preferably 1.0 μm or more, and usually 100 μm or less, preferably 60 μm or less, more preferably 20 μm or less. It is. If the film thickness is too large, the amount of permeation tends to decrease, and if it is too small, the selectivity tends to decrease or the film strength tends to decrease.
The particle diameter of the zeolite is not particularly limited, but if it is too small, the grain boundary tends to increase, and the permeation selectivity tends to decrease. Therefore, it is usually 30 nm or more, preferably 50 nm or more, more preferably 100 nm or more, and the upper limit is the film thickness or less. Furthermore, it is particularly preferred that the zeolite particle size is the same as the membrane thickness. When the zeolite particle size is the same as the membrane thickness, the zeolite grain boundary is smallest. Zeolite membranes obtained by hydrothermal synthesis described later are particularly preferred because the zeolite particle size and membrane thickness may be the same.

The shape of the zeolite membrane composite is not particularly limited, and any shape such as a tubular shape, a hollow fiber shape, a monolith type, and a honeycomb type can be adopted. Also, the size is not particularly limited. For example, in the case of a tubular shape, a length of 2 cm to 200 cm, an inner diameter of 0.05 cm to 2 cm, and a thickness of 0.5 mm to 4 mm are practical and preferable.
One of the separation functions of the zeolite membrane is separation as a molecular sieve, and gas molecules having a size greater than or equal to the effective pore diameter of the zeolite to be used can be suitably separated. There is no upper limit to the molecules used for separation, but the size of the molecules is usually about 100 mm or less.

The zeolite is preferably an aluminosilicate.
The SiO ₂ / Al ₂ O ₃ molar ratio of the zeolite membrane itself is usually 0.5 or more, preferably 5 or more, more preferably 8 or more, further preferably 10 or more, particularly preferably 12 or more, preferably 2000 or less. More preferably, it is 1000 or less, More preferably, it is 500 or less, More preferably, it is 100 or less, Most preferably, it is 50 or less.

The SiO ₂ / Al ₂ O ₃ molar ratio of the zeolite membrane itself is a numerical value obtained by scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDX). In SEM-EDX, information of only a film of several microns can be obtained by measuring the acceleration voltage of X-rays at about 10 kV. Since the zeolite membrane is uniformly formed, the SAR of the membrane itself can be obtained by this measurement.

The main zeolite constituting the zeolite membrane preferably contains a zeolite having a pore structure with an oxygen 8-membered ring or less, and more preferably contains a zeolite having a pore structure with an oxygen 6- to 8-membered ring.
Here, the value of n of the zeolite having an oxygen n-membered ring has the largest number of oxygen in the pores composed of oxygen forming the zeolite skeleton and T element (element other than oxygen constituting the skeleton). Show things. For example, when there are 12-membered and 8-membered pores of oxygen, such as MOR type zeolite, it is regarded as a 12-membered ring zeolite.

  Examples of the zeolite having a pore structure having an oxygen 8-membered ring or less include, for example, AEI, AFG, ANA, BRE, CAS, CDO, CHA, DDR, DOH, EAB, EPI, ERI, ESV, FAR, FRA, GIS, GIU , GOO, ITE, KFI, LEV, LIO, LOS, LTA, LTN, MAR, MEP, MER, MEL, MON, MSO, MTF, MTN, NON, PAU, PHI, RHO, RTE, RTH, RUT, SGT, SOD , TOL, TSC, UFI, VNI, YUG and the like.

Examples of the zeolite having an oxygen 6-8 membered ring structure include AEI, AFG, ANA, CHA, EAB, ERI, ESV, FAR, FRA, GIS, ITE, KFI, LEV, LIO, LOS, LTA, LTN, MAR. , PAU, RHO, RTH, SOD, TOL, UFI and the like.
In addition, in this specification, the structure of a zeolite is shown with the code | symbol which prescribes | regulates the structure of the zeolite which International Zeolite Association (IZA) defines as above-mentioned.

The oxygen n-membered ring structure determines the size of the pores of the zeolite. In the case of zeolite smaller than the oxygen 6-membered ring, the pore diameter is smaller than the kinetic diameter of the H ₂ O molecule. In some cases, the transmittance is small and not practical. In addition, when it is larger than the oxygen 8-membered ring structure, the pore diameter becomes large, and a gas component or liquid component having a small size may deteriorate the separation performance, and the use may be limited.

The framework density (T / 1000 ³ ) of the zeolite is not particularly limited, but is usually 17 or less, preferably 16 or less, more preferably 15.5 or less, particularly preferably 15 or less, usually 10 or more, preferably 11 or more. More preferably, it is 12 or more.
The framework density means the number of elements (T element) other than oxygen constituting the framework per 1000 ³ of the zeolite, and this value is determined by the structure of the zeolite. The relationship between the framework density and the structure of zeolite is shown in ATLAS OF ZEOLITE FRAMEWORK TYPES Sixth Revised Edition 2007 ELSEVIER.

  In the present invention, preferred zeolite structures are AEI, AFG, CHA, EAB, ERI, ESV, FAR, FRA, GIS, ITE, KFI, LEV, LIO, LOS, LTN, MAR, PAU, RHO, RTH, SOD, More preferred structures are AEI, CHA, ERI, KFI, LEV, PAU, RHO, RTH, UFI, more preferred structures are CHA, LEV, RHO, and the most preferred structure is CHA. is there.

  Here, in the present invention, the CHA-type zeolite is a code that defines the structure of the zeolite defined by the International Zeolite Association (IZA) and indicates a CHA structure. This is a zeolite having a crystal structure equivalent to that of naturally occurring chabazite. The CHA-type zeolite has a structure characterized by having three-dimensional pores composed of 8-membered oxygen rings having a diameter of 3.8 × 3.8 mm, and the structure is characterized by X-ray diffraction data.

The framework density (T / 1000 ³ ) of the CHA-type zeolite is 14.5. The SiO ₂ / Al ₂ O ₃ molar ratio is the same as described above.
In the present invention, when the zeolite membrane contains CHA-type zeolite, the intensity of the peak around 2θ = 17.9 ° is the intensity of the peak around 2θ = 20.8 ° in the X-ray diffraction pattern. It is preferable that the size is 0.5 times or more.

  Here, the peak intensity refers to a value obtained by subtracting the background value from the measured value. Peak intensity ratio represented by (Intensity of peak near 2θ = 17.9 °) / (Intensity of peak near 2θ = 20.8 °) (hereinafter, this may be referred to as “peak intensity ratio A”) In other words, it is usually 0.5 or more, preferably 1 or more, more preferably 1.2 or more, and particularly preferably 1.5 or more. Although an upper limit is not specifically limited, Usually, it is 1000 or less.

When the zeolite membrane contains CHA-type zeolite, the intensity of the peak near 2θ = 9.6 ° is 2 of the peak intensity around 2θ = 20.8 ° in the X-ray diffraction pattern. The size is preferably twice or more.
Peak intensity ratio represented by (Intensity of peak near 2θ = 9.6 °) / (Intensity of peak near 2θ = 20.8 °) (hereinafter, this may be referred to as “peak intensity ratio B”) In other words, it is usually 2 or more, preferably 2.5 or more, more preferably 3 or more, more preferably 4 or more, still more preferably 6 or more, particularly preferably 8 or more, and most preferably 10 or more. Although an upper limit is not specifically limited, Usually, it is 1000 or less.

<Method for producing zeolite membrane composite>
In the present invention, for example, after a zeolite membrane is formed on the porous support by hydrothermal synthesis, the temperature of the porous support on which the zeolite membrane is formed is set to 50 ° C. or higher, and the surface treatment is performed with an Si compound or the like. Apply.
Specifically, for example, the zeolite membrane composite contains a reaction mixture for hydrothermal synthesis (hereinafter, this may be referred to as “aqueous reaction mixture”) in which the porous support is adjusted to be uniform in composition. It can be prepared by placing it in a heat and pressure resistant container such as an autoclave, sealing it and heating it for a certain time.

The aqueous reaction mixture preferably contains an Si element source, an Al element source, an alkali source, and water, and further contains an organic template as necessary.
Examples of the Si element source used in the aqueous reaction mixture include amorphous silica, colloidal silica, silica gel, sodium silicate, amorphous aluminum silicate gel, tetraethoxysilane (TEOS), trimethylethoxysilane, and the like.

As the Al element source, for example, sodium aluminate, aluminum hydroxide, aluminum sulfate, aluminum nitrate, aluminum oxide, amorphous aluminosilicate gel, or the like can be used. In addition to the Al element source, other element sources, for example, element sources such as Ga, Fe, B, Ti, Zr, Sn, and Zn may be included.
In crystallization of zeolite, an organic template (structure directing agent) can be used as necessary, but those synthesized using an organic template are preferred. By synthesizing using an organic template, the ratio of silicon atoms to aluminum atoms of crystallized zeolite is increased, and acid resistance and water vapor resistance are improved.

The organic template may be any type as long as it can form a desired zeolite membrane. Further, one type of template or a combination of two or more types may be used.
When the zeolite is of the CHA type, amines and quaternary ammonium salts are usually used as the organic template. For example, organic templates described in U.S. Pat. No. 4,544,538 and U.S. Patent Publication No. 2008/0075656 are preferred.

As the alkali source used in the aqueous reaction mixture, a hydroxide ion of a counter anion of an organic template, an alkali metal hydroxide such as NaOH or KOH, or an alkaline earth metal hydroxide such as Ca (OH) ₂ is used. Can do. The type of alkali is not particularly limited, and Na, K, Li, Rb, Cs, Ca, Mg, Sr, Ba and the like are usually used. Among these, Li, Na, and K are preferable, and K is more preferable. In addition, two or more alkalis may be used in combination, and specifically, Na and K, and Li and K 2 are preferably used in combination.

The ratio of Si element source to Al element source in the aqueous reaction mixture is usually expressed as the molar ratio of the oxides of the respective elements, that is, the SiO ₂ / Al ₂ O ₃ molar ratio. The SiO ₂ / Al ₂ O ₃ molar ratio is not particularly limited, but is preferably 5 or more, more preferably 8 or more, still more preferably 10 or more, and particularly preferably 15 or more. Further, it is usually 10,000 or less, preferably 1000 or less, more preferably 300 or less, and still more preferably 100 or less.

When the SiO ₂ / Al ₂ O ₃ molar ratio is within this range, the zeolite membrane is densely formed, and the membrane has high separation performance. In addition, since moderately Al atoms are present in the produced zeolite, the separation performance is improved with a gas component or a liquid component exhibiting adsorptivity to Al. When Al is within this range, a zeolite membrane having high acid resistance and high water vapor resistance can be obtained.
The ratio of the silica source and an organic template in the aqueous reaction mixture, the molar ratio of the organic template for SiO ₂ (organic template / SiO ₂ molar ratio), usually 0.005 or higher, preferably at least 0.01, more preferably 0 0.02 or more, usually 1 or less, preferably 0.4 or less, more preferably 0.2 or less.

When the organic template / SiO ₂ molar ratio is in the above range, in addition to being able to produce a dense zeolite membrane, the produced zeolite has strong acid resistance and water vapor resistance.
The ratio of the Si element source to the alkali source is M _{(2 / n) 2} O / SiO ₂ (where M represents an alkali metal or alkaline earth metal, and n represents the valence 1 or 2). In general, it is 0.02 or more, preferably 0.04 or more, more preferably 0.05 or more, and usually 0.5 or less, preferably 0.4 or less, more preferably 0.3 or less.

In the case of forming a CHA-type zeolite membrane, it is preferable that K is contained in the alkali metal because a denser and highly crystalline membrane is formed. In this case, the molar ratio of K to all alkali metals and / or alkaline earth metals containing K is usually 0.01 or more and 1 or less, preferably 0.1 or more and 1 or less, more preferably 0.3 or more. 1 or less.
The ratio of Si element source to water is the molar ratio of water to SiO ₂ (H ₂ O / SiO ₂ molar ratio), which is usually 10 or more, preferably 30 or more, more preferably 40 or more, and particularly preferably 50 or more. Usually, it is 1000 or less, preferably 500 or less, more preferably 200 or less, and particularly preferably 150 or less.

When the molar ratio of materials in the aqueous reaction mixture is in these ranges, a dense zeolite membrane can be formed. The amount of water is particularly important in the formation of a dense zeolite membrane, and a denser membrane tends to be formed more easily under conditions where the amount of water is greater than that of the general powder synthesis method.
Further, in the hydrothermal synthesis, it is not always necessary to have a seed crystal in the reaction system, but the crystallization of zeolite can be promoted on the support by adding the seed crystal. The method of adding the seed crystal is not particularly limited, and a method of adding the seed crystal to the aqueous reaction mixture or the method of attaching the seed crystal on the support as in the synthesis of the powdered zeolite is used. Can do.

When producing a zeolite membrane composite, it is preferable to attach a seed crystal on the support. By attaching a seed crystal in advance to the support, a dense zeolite membrane with good separation performance can be easily formed.
The seed crystal to be used is not limited as long as it is a zeolite that promotes crystallization, but it is preferably the same crystal type as the zeolite membrane to be formed for efficient crystallization.

The particle diameter of the seed crystal is usually 0.5 nm or more, preferably 1 nm or more, more preferably 2 nm or more, and is usually 20 μm or less, preferably 15 μm or less, more preferably 10 μm or less.
The method for attaching the seed crystal on the support is not particularly limited. For example, a dip method in which the seed crystal is dispersed in a solvent such as water and the support is immersed in the dispersion to attach the seed crystal, or a seed crystal is attached. For example, a slurry mixed with a solvent such as water or a seed crystal itself may be coated on a support. The dip method is desirable for controlling the amount of seed crystals attached and producing a membrane composite with good reproducibility.

The solvent for dispersing the seed crystal is not particularly limited, but water is particularly preferable.
The amount of the seed crystal to be dispersed is not particularly limited, and is usually 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 0.3% by mass or more, based on the total mass of the dispersion. Usually, it is 20 mass% or less, Preferably it is 10 mass% or less, More preferably, it is 5 mass% or less, More preferably, it is 4 mass% or less, Most preferably, it is 3 mass% or less.

  If the amount of seed crystals to be dispersed is too small, the amount of seed crystals adhering to the support is small, so that a portion where no zeolite is generated on the support during hydrothermal synthesis is created, resulting in a defective film. there is a possibility. The amount of seed crystals adhering to the support by the dip method becomes almost constant when the amount of seed crystals in the dispersion is higher than a certain level, so if the amount of seed crystals in the dispersion is too large, the seed crystals are wasted. It is more disadvantageous in terms of cost.

It is desirable to deposit the seed crystal on the support by dipping or slurry coating, and after drying, form a zeolite membrane.
The amount of the seed crystal to be preliminarily deposited on the support is not particularly limited, and is usually 0.01 g or more, preferably 0.05 g or more, more preferably 0.1 g or more, by mass per 1 m ^{2 of} the base material. Usually, it is 100 g or less, preferably 50 g or less, more preferably 10 g or less, still more preferably 8 g or less.

When a zeolite membrane is formed on a support by hydrothermal synthesis, there are no particular limitations on the method for immobilizing the support, and it can take any form such as vertical or horizontal placement. In this case, the zeolite membrane may be formed by a stationary method, or the aqueous reaction mixture may be stirred to form a zeolite membrane.
The temperature at which the zeolite membrane is formed is not particularly limited, but is usually 100 ° C. or higher, preferably 120 ° C. or higher, more preferably 150 ° C. or higher, usually 200 ° C. or lower, preferably 190 ° C. or lower, more preferably 180 ° C. It is as follows. If the reaction temperature is too low, the zeolite may be difficult to crystallize. If the reaction temperature is too high, a zeolite of a type different from the zeolite in the present invention may be easily generated.

  The heating time is not particularly limited, but is usually 1 hour or more, preferably 5 hours or more, more preferably 10 hours or more, and usually 10 days or less, preferably 5 days or less, more preferably 3 days or less, and even more preferably 2 Less than a day. If the reaction time is too short, the zeolite may be difficult to crystallize. If the reaction time is too long, a zeolite of a type different from the desired zeolite may be easily generated.

The pressure at the time of forming the zeolite membrane is not particularly limited, and the self-generated pressure generated when the aqueous reaction mixture placed in the closed vessel is heated to this temperature range is sufficient. Further, an inert gas such as nitrogen may be added as necessary.
The zeolite membrane composite obtained by hydrothermal synthesis is washed with water, then heated and dried. Here, the heat treatment means that the template is fired when heat is applied to dry the zeolite membrane composite or the template is used.

  The temperature of the heat treatment is usually 50 ° C. or higher, preferably 80 ° C. or higher, more preferably 100 ° C. or higher, and usually 200 ° C. or lower, preferably 150 ° C. or lower, for the purpose of drying. Moreover, when aiming at baking of a template, it is 350 degreeC or more normally, Preferably it is 400 degreeC or more, More preferably, it is 430 degreeC or more, More preferably, it is 480 degreeC or more, Usually 900 degrees C or less, Preferably it is 850 degrees C or less, and more Preferably it is 800 degrees C or less, More preferably, it is 750 degrees C or less.

When firing the template, if the temperature of the heat treatment is too low, the proportion of the remaining organic template tends to increase, and the zeolite has fewer pores, and therefore the permeability during separation and concentration. May decrease. If the heat treatment temperature is too high, the difference in coefficient of thermal expansion between the support and the zeolite becomes large, so the zeolite membrane may be easily cracked, and the denseness of the zeolite membrane may be lost, resulting in poor separation performance. .

The heating time is not particularly limited as long as the zeolite membrane is sufficiently dried or the template is calcined, and is preferably 0.5 hours or more, more preferably 1 hour or more. The upper limit is not particularly limited, and is usually within 200 hours, preferably within 150 hours, and more preferably within 100 hours. The heat treatment for the purpose of firing the template may be performed in an air atmosphere, but may be performed in an atmosphere to which an inert gas such as N ₂ or oxygen is added.

When hydrothermal synthesis is performed in the presence of an organic template, the obtained zeolite membrane composite can be washed with water, and then the organic template can be removed by, for example, heat treatment or extraction, preferably by heat treatment, that is, baking. Is appropriate.
It is desirable that the temperature increase rate during the heat treatment for firing the template is as slow as possible in order to reduce the difference in the thermal expansion coefficient between the support and the zeolite from causing cracks in the zeolite membrane. The temperature rising rate is usually 5 ° C./min or less, preferably 2 ° C./min or less, more preferably 1 ° C./min or less, and particularly preferably 0.5 ° C./min or less. Usually, it is 0.1 ° C./min or more in consideration of workability.

Moreover, it is necessary to control the temperature drop rate after firing in order to avoid cracks in the zeolite membrane. Similar to the rate of temperature increase, the slower the better. The temperature lowering rate is usually 5 ° C./min or less, preferably 2 ° C./min or less, more preferably 1 ° C./min or less, and particularly preferably 0.5 ° C./min or less. Usually, it is 0.1 ° C./min or more in consideration of workability.
The zeolite membrane may be ion exchanged as necessary. In the case of synthesizing using a template, ion exchange is usually performed after removing the template. Ions to be ion-exchanged include protons, alkali metal ions such as Na ⁺ , K ⁺ and Li ⁺ , Group 2 element ions such as Ca ²⁺ , Mg ²⁺ , Sr ²⁺ and Ba ^2+, and transition metals such as Fe and Cu. Examples include ions, ions of other metals such as Al, Ga, and Zn. Among these, protons, alkali metal ions such as Na ⁺ , K ⁺ , and Li ^+, and ions of Fe, Al, and Ga are preferable.

In ion exchange, the zeolite membrane after calcination (such as when a template is used) is replaced with an ammonium salt such as NH ₄ NO ₃ or NaNO ₃ or an aqueous solution containing ions to be exchanged, and in some cases an acid such as hydrochloric acid. What is necessary is just to perform by the method of washing with water etc. after processing at the temperature of 100 degreeC. Furthermore, you may bake at 200 to 500 degreeC as needed.

<Surface treatment>
Subsequently, the formed zeolite membrane is subjected to a surface treatment. Before the surface treatment, the present invention is characterized in that the temperature of the porous support on which the zeolite membrane is formed is 50 ° C. or higher.
For example, it is considered that by performing a surface treatment with a Si compound, a Si layer is formed on the surface of the zeolite membrane, the fine defect diameter between the zeolite crystals present in the zeolite membrane is reduced, and the separation performance can be improved.

However, when the porous support-zeolite membrane composite is actually used as a separation membrane, the porous support-zeolite membrane composite is exposed to high temperature conditions. For example, in the phenol / water separation, the temperature of the liquid is estimated to be about 130 ° C, and the porous support-zeolite membrane composite is also estimated to be about 130 ° C. Under this high temperature condition, the difference in coefficient of thermal expansion between the porous support and the zeolite membrane increases. The present inventors speculated that fine defects existing in the film blocked by the surface treatment may spread again due to the difference in thermal expansion coefficient. Then, it is predicted that the defect that has spread again is a cause of reducing the separation performance, and in the present invention, a method in which the defect is not formed again was studied.

Therefore, by heating the porous support on which the zeolite membrane is formed by an operation such as heating, that is, by setting the temperature to 50 ° C. or higher, the defects that are expected to occur due to the difference in the coefficient of thermal expansion are preliminarily spread and widened. It was thought that by performing surface treatment in such a state, defects can be prevented from actually occurring when used as a separation membrane at high temperatures.
The present invention is characterized in that the temperature of the porous support on which the zeolite membrane is formed before the surface treatment is 50 ° C. or higher, but for the reasons described above, the temperature is maintained above this temperature. It is preferable to perform a surface treatment.

Examples of a method for controlling the temperature of the porous support to 50 ° C. or higher include heating with an oven, an electric furnace, an oil bath, a water bath, and the like. Among these, a method of heating with an oven is preferable from the viewpoint of operability. These methods may be used in combination of two or more methods.
In particular, by controlling to 50 ° C. or higher, it is preferable to dry the zeolite membrane surface and remove adsorbed water adsorbed on the zeolite membrane surface. For example, when the surface treatment described in detail below is performed in a hermetically sealed state, the performance of the zeolite membrane may be reduced due to a reaction between the material used for the surface treatment and the adsorbed water adsorbed on the zeolite membrane surface.
In order to avoid the above reaction and the like, it is preferable to remove the adsorbed water adsorbed on the surface of the zeolite membrane by controlling the temperature of the porous support to 50 ° C. or higher before the surface treatment. The adsorbed water may be removed by.
Examples of other means include dehydration by reduced pressure, dehydration by a desiccant, and a method of blowing a gas such as low-humidity air.
The temperature of the porous support may be 50 ° C. or higher, preferably 75 ° C. or higher, more preferably 100 ° C. or higher, still more preferably 125 ° C. or higher, preferably 200 ° C. or lower, more preferably 175. ° C or lower, more preferably 150 ° C or lower. By being in this range, high separation performance can be obtained.
In addition, the temperature of a support body can be measured by the method using various thermometers, such as a contact-type thermometer, a radiation thermometer, and a thermocouple.

  For the surface treatment, a material that can block defects existing on the surface of the zeolite membrane is used. This material is preferably a material containing Si atoms (hereinafter sometimes referred to as Si compound), specifically, tetraethoxysilane, tetramethoxysilane, methyltriethoxysilane, 3-aminopropyltriethoxysilane, Alkoxysilanes such as 1,1,3,3-tetramethoxy-1,3-dimethylpropanedisiloxane, organosilicon compounds having a siloxane such as hexamethyldisiloxane, and organosilicon compounds having a silazane such as hexamethyldisilazane Silicate oligomers such as methyl silicate oligomer and ethyl silicate oligomer, amorphous silica, fumed silica, colloidal silica, silica gel, sodium silicate, silica sol and the like can be used. From the viewpoint of reactivity and the formation of a Si network, alkoxysilanes and silicate oligomers are preferred. In particular, tetraethoxysilane, 3-aminopropyltriethoxysilane, methyl silicate oligomer, and ethyl silicate oligomer are preferable.

The number of Si atoms in the Si compound is not particularly limited as long as it is 1 or more, and an appropriate one may be selected depending on the required opening diameter and the size of the defect to be blocked, but preferably 2 or more, more preferably 3 or more, More preferably, it is 4 or more. Moreover, it is 120 or less normally, Preferably it is 90 or less, More preferably, it is 70 or less, Most preferably, it is 50 or less. When the Si in the molecule is within this range, the aperture diameter can be effectively narrowed and defects can be closed. If the number of Si atoms in the molecule is too small, the opening diameter may not be sufficiently small, and defects may not be sufficiently blocked.

  The viscosity of the Si compound is usually 0.5 mPas or more, preferably 2 mPas or more, and more preferably 3 mPas. Moreover, it is 150 mPas or less normally, Preferably it is 120 mPas or less, More preferably, it is 100 mPas or less, Most preferably, it is 80 mPas or less. If the viscosity is too low, the Si compound may not remain sufficiently on the surface of the zeolite membrane in a method in which it is immersed in a liquid containing a Si compound, which will be described later, or heated by dropping or spraying a liquid containing the Si compound. is there. If the viscosity is too high, there may be a difference in the amount of Si compound adhering between the upper part and the lower part of the zeolite membrane at the time of pulling up or thereafter, and the uniform treatment may not be achieved. The viscosity can be adjusted as a solution containing a Si compound by adding a solvent.

The surface treatment method is not particularly limited, but an immersion treatment in which a zeolite membrane composite is immersed in a solution or dispersion containing an Si compound, a dropping treatment in which a solution containing Si atoms is dropped into the zeolite membrane composite, or There is a spray process to spray.
When performing a surface treatment using a liquid such as an immersion treatment, the surface treatment liquid used for the surface treatment is not particularly limited as long as the zeolite membrane composite can be treated under the condition of the surface treatment. It may be a solution obtained by adding a solvent to a compound, may be a liquid to which no solvent is added, or may be a sol or gel.

In particular, when a silicate oligomer is used as the Si compound, it is not necessary to add a solvent. Even when the solvent is not further added, as another element source (compound), for example, an Al compound may be included.
Here, the solvent may be water or an organic solvent. In addition, solvents that are liquid under pressure at temperatures above the boiling point are also included in the solvent. The pressure in this case may be an autogenous pressure or a pressurization. Further, as described above, the surface treatment liquid only needs to contain at least a Si compound, and as another element source (compound), for example, an Al compound may be included.

Examples of the organic solvent that can be used include nonpolar solvents such as toluene and hexane, alcohol solvents such as anisole and isopropyl alcohol, and polar solvents such as acetone. Of these, toluene and isopropyl alcohol are particularly preferable. These organic solvents may be used individually by 1 type, and may be used in combination of 2 or more type.
The temperature of the surface treatment liquid is not particularly limited, but is usually 20 ° C. or higher, preferably 40 ° C. or higher, more preferably 50 ° C. or higher, further preferably 60 ° C. or higher, particularly preferably 80 ° C. or higher, usually 200 ° C. The temperature is preferably 150 ° C. or lower, more preferably 130 ° C. or lower. If the temperature is too low, the progress of the dehydration condensation reaction and hydrolysis reaction performed between the Si compound and the film surface and the Si compound is insufficient, and the modification with the Si compound is not performed sufficiently, and the hydrophilicity of the film surface is not sufficiently improved. Sometimes. If the temperature is too high, a part of the zeolite may elute in water and the zeolite membrane may be broken.

  The content of the Si compound in the surface treatment liquid is usually 0.01% by mass or more, preferably 0.1% by mass or more, and usually 20% by mass or less, preferably 10% by mass or less, as the concentration of the Si compound. More preferably, it is 5 mass% or less. The concentration in the case of Si element is usually 0.01% by mass or more, preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and usually 10% by mass or less, preferably 5% by mass. % Or less, more preferably 2% by mass or less.

Further, when an organic solvent is used, water may be added into the system. The concentration of water to be added is usually 0.001% by mass or more, preferably 0.05% by mass or more, more preferably 0.2% by mass or more, and usually 5% by mass or less, preferably 3% by mass or less. Preferably it is 2 mass% or less.
It is preferable that an acid or a base is present in the surface treatment solution as a catalyst for the zeolite surface OH group and the Si compound, a dehydration condensation reaction between the Si compounds, and an alkoxy group hydrolysis reaction. Accordingly, the pH of the solution may be generally 0 to 12, preferably 0.5 to 10, more preferably about 1 to 8.

For example, by adding a basic substance such as NaOH, KOH, or amine to the surface treatment liquid, a trace amount of OH ⁻¹ ions may be actively present. In this case, the OH ⁻¹ ion concentration in the aqueous solution is The concentration is usually 0.01 mol / l or less, more preferably 0.005 mol / l or less, and usually 0.0001 mol / l or more, preferably 0.0005 mol / l or more, more preferably 0.001 mol / l or more. The presence of OH ^-1 ions in the surface treatment liquid makes it possible to obtain the same effect in a shorter time than when no OH ^-1 ions exist. If the OH- ¹ ion concentration in the surface treatment liquid is too high, the zeolite membrane is easily dissolved and broken, and strict control of the treatment time is required.

Examples of the acid present in the surface treatment liquid include organic acids such as carboxylic acid and sulfonic acid, and inorganic acids such as sulfuric acid and phosphoric acid. Among these, carboxylic acid and inorganic acid are particularly preferable.
As the carboxylic acid, for example, formic acid, acetic acid, propionic acid, oxalic acid, malonic acid, maleic acid, phthalic acid, lactic acid, citric acid, acrylic acid and the like are preferable, formic acid, acetic acid and lactic acid are more preferable, and acetic acid is particularly preferable. . As the inorganic acid, for example, sulfuric acid, nitric acid, phosphoric acid, hydrochloric acid and the like are preferable, and sulfuric acid, nitric acid, and phosphoric acid are more preferable.

The concentration of the acidic substance in the surface treatment liquid is preferably 0.01 mol / l or more, more preferably 0.05 mol / l or more, still more preferably 10 mol / l or less, and particularly preferably 1 mol / l or less.
The H ⁺ concentration is usually 1 × 10 ⁻¹⁰ mol / l or more, preferably 1 × 10 ⁻⁸ mol / l or more, more preferably 1 × 10 ⁻⁷ mol / l or more, and particularly preferably 1 × 10 ^{−5. 5} mol / l or more, usually 10 mol / l or less, preferably 5 mol / l or less, more preferably 1 mol / l or less.

A basic substance may coexist so that the H ⁺ concentration falls within the above range. Examples of the basic substance include NaOH, KOH, amine and the like.
The pressure during the surface treatment is not particularly limited, and the atmospheric pressure or the self-generated pressure generated when the treatment solution placed in the sealed container is heated to the above temperature range is sufficient. Further, an inert gas such as nitrogen may be added as necessary.

In particular, when a tubular support is used as the porous support, it is preferable to apply a surface treatment by reducing the pressure inside the tubular support. Thereby, the surface treatment liquid can easily enter the inside of the defect, and an effect of efficiently closing the defect can be obtained.
Examples of the depressurization method include a method using a vacuum pump such as a rotary pump or a diaphragm pump, an aspirator, or the like.

When the immersion treatment is performed, the treatment may be performed by immersing in a surface treatment solution and forming a chemical bond with the Si compound in the immersion solution. After immersion, the zeolite membrane is taken out of the solution. Chemical bonds may be formed with the Si compound attached to the surface, or chemical bonds may be formed both during and after immersion.
The dipping time is usually 30 minutes or longer, preferably 1 hour or longer, more preferably 4 hours or longer, more preferably 8 hours or longer, and usually 100 hours or shorter, preferably 50 hours or shorter, more preferably 24 hours or shorter. .

After the surface treatment, the support may be allowed to stand in a thermostatic bath or the like, and the temperature at this time is usually 20 ° C. or higher, preferably 40 ° C. or higher, more preferably 50 ° C. or higher, more preferably 60 ° C. or higher, Particularly preferably, it is 80 ° C. or higher, usually 200 ° C. or lower, preferably 150 ° C. or lower, more preferably 130 ° C. or lower. The time for standing is usually 5 minutes or longer, preferably 30 minutes or longer, more preferably 60 minutes or longer, and usually 180 minutes or shorter.
In the surface treatment, the surface treatment can be performed by immersing in a liquid containing at least an Si compound, or dropping or spraying a liquid containing at least an Si compound, and then heating. In this case, it can also process without adding a solvent.

  When the zeolite membrane composite is immersed in the liquid containing the Si compound after being immersed in the liquid containing the Si compound or when the liquid containing the Si compound is dropped or sprayed, the tubular zeolite membrane composite is immersed in the liquid containing the Si compound. In this case, it is desirable to prevent a large amount of Si compound from penetrating into the support by covering only the bottom or top and bottom with a silicon rubber stopper or Teflon (registered trademark) tape. By contacting the Si compound only on the surface of the zeolite membrane and preventing penetration into the support portion, the surface of the zeolite membrane can be efficiently surface-treated while maintaining a high permeation amount.

  The heating temperature after dipping or dropping or spraying the liquid containing the Si compound is usually 30 ° C. or higher, preferably 50 ° C. or higher, more preferably 70 ° C. or higher, and usually 300 ° C. or lower, preferably 250 ° C. or lower. More preferably, it is 200 degrees C or less, Most preferably, it is 150 degrees C or less. When the temperature is lower than this range, the modification with the Si compound on the surface of the zeolite membrane may not be sufficiently immobilized. When the temperature is higher than this range, although depending on the boiling point of the Si compound, the Si compound volatilizes from the surface and the modification may not be performed sufficiently.

  When heating after immersion or dropping or spraying the liquid containing the Si compound, the heating time is usually 30 minutes or longer, preferably 1 hour or longer, more preferably 1.5 hours or longer, more preferably 2 hours or longer. Usually, it is 30 hours or less, preferably 25 hours or less, more preferably 20 hours or less, and further preferably 15 hours or less. When the time is shorter than this range, the modification with the Si compound on the zeolite membrane surface may not be sufficiently immobilized. When the time is longer than this range, the modification with the Si compound is heated more than sufficiently fixed, which is disadvantageous in terms of energy.

When heating after immersion or dropping or spraying a liquid containing a Si compound, it is preferable that water be present in the heating system. By coexisting water, the hydrolysis of alkoxysilane contained in the silicate oligomer or the like is likely to proceed, and the surface of the zeolite membrane can be sufficiently modified.
Heating after dipping or dropping or spraying the liquid containing the Si compound can be performed with a normal drier or the like, or the film after dipping may be placed in a sealed container and heated. A small amount of water may be allowed to coexist so as not to come into contact with the film when immersed in a sealed container or when the film containing the Si compound is dropped or sprayed.

The zeolite membrane composite thus produced has excellent characteristics as described above, and can be suitably used as a membrane separation means in the separation or concentration method of the present invention.
The air permeation [L / (m ² · h)] of the porous support-zeolite membrane composite (zeolite membrane composite after heat treatment) thus obtained is usually 1400 L / (m ² · h) or less, preferably Is 1000 L / (m ² · h) or less, more preferably 700 L / (m ² · h) or less, more preferably 600 L / (m ² · h) or less, more preferably 500 L / (m ² · h) or less, particularly preferably 300L / ^(m 2 · h) or less, most preferably 200L / ^{(m 2} ·
h) The following. In lower limit of the transmission amount is not particularly limited, it is generally 0.01L / ^(m 2 · h) or more, preferably 0.1L / ^(m 2 · h) or more, more preferably 1L / ^(m 2 · h) or higher is there.
Here, the air permeation amount is the air permeation amount [L / (m ² · h)] when the zeolite membrane composite is connected to a vacuum line having an absolute pressure of 5 kPa, as will be described later.

<Separation or concentration method>
In the separation or concentration method of the present invention, a porous support-zeolite membrane composite obtained by the above production method is brought into contact with a gas or liquid mixture comprising a plurality of components, and the mixture is highly permeable. It is characterized by concentrating a low-permeability substance by permeating and separating the substance, or by permeating a high-permeability substance from the mixture.

  In the separation or concentration method of the present invention, a gas or liquid mixture composed of a plurality of components is brought into contact with one side of the support side or the zeolite membrane side through an inorganic porous support provided with a zeolite membrane, and the opposite side thereof. By setting the pressure at a lower pressure than the side in contact with the mixture, a substance having a high permeability to the zeolite membrane (a substance in the mixture having a relatively high permeability) is selectively selected from the mixture, that is, the main substance of the permeate. Permeate as a component. Thereby, a highly permeable substance can be separated from the mixture. As a result, the specific component can be separated and recovered or concentrated by increasing the concentration of the specific component (substance in the mixture having relatively low permeability) in the mixture.

The mixture to be separated or concentrated is not particularly limited as long as it is a gas or liquid mixture composed of a plurality of components that can be separated or concentrated by the porous support-zeolite membrane composite in the present invention. It may be a mixture.
When the mixture to be separated or concentrated is, for example, a mixture of an organic compound and water (hereinafter sometimes referred to as “hydrous organic compound”), water is usually highly permeable to the zeolite membrane. So water is separated from the mixture and the organic compound is concentrated in the original mixture. A separation or concentration method called a pervaporation method (permeation vaporization method) or a vapor permeation method (vapor permeation method) is one embodiment of the method of the present invention. The pervaporation method is a separation or concentration method in which a liquid mixture is directly introduced into a separation membrane, so that a process including separation or concentration can be simplified.

  The vapor permeation method is a separation / concentration method in which a liquid mixture is vaporized and then introduced into a separation membrane. Therefore, the vapor permeation method can be used in combination with a distillation apparatus or for separation at higher temperature and pressure. In addition, the vapor permeation method introduces the liquid mixture after vaporizing it into the separation membrane, reducing the effects of impurities contained in the supply liquid and substances that form aggregates and oligomers in the liquid state on the membrane. can do. The inorganic porous support-zeolite membrane composite obtained by the present invention can be suitably used for any method.

  In addition, when performing separation at a high temperature by the vapor permeation method, in general, the higher the temperature and the higher the concentration of the component having low permeability in the mixture, for example, in the case of a mixture of an organic compound and water, Although the separation performance decreases as the concentration of the compound increases, the inorganic porous support-zeolite membrane composite obtained by the present invention has high separation performance even at high temperatures and even when the concentration of the low-permeability component in the mixture is high. Can be expressed. In general, the vapor permeation method separates the liquid mixture after vaporizing it, and therefore usually the separation is performed under harsher conditions than the pervaporation method. Therefore, durability of the membrane composite is also required. The inorganic porous support-zeolite membrane composite obtained by the present invention is suitable for the vapor permeation method because it has durability capable of being separated even under high temperature conditions.

  The porous support-zeolite membrane composite has specific physicochemical properties, so that not only when the concentration of the low-permeability component in the mixture is high, but also when the concentration of the low-permeability component is low However, it exhibits high permeation performance, selectivity, and performance as a separation membrane with excellent durability. For example, a mixture of an organic compound and water exhibits high selectivity regardless of the concentration of water. That is, the zeolite membrane composite having specific physicochemical properties of the present invention is suitable for separation and concentration of a mixture in a wide concentration range.

The high permeation performance here indicates a sufficient throughput, for example, a permeation flux of a substance that permeates the membrane is, for example, a mixture of acetic acid and water having a water content of 10% by mass at 90 ° C. at 1 atm ( When permeated with a pressure difference of 1.01 × 10 ⁵ Pa), 0.5 kg / (m ² · h) or more, preferably 1 kg / (m ² · h) or more, more preferably 1.5 kg / (m ² · h) or more. The upper limit of the permeation flux is not particularly limited, and is usually 20 kg / (m ² · h) or less, preferably 15 kg / (m ² · h) or less.

Further, when a mixture of phenol and water having a water content of 10% by mass is permeated at 75 ° C. with a pressure difference of 1 atm (1.01 × 10 ⁵ Pa), the permeation flux of the substance that permeates the membrane is It means 0.5 kg / (m ² · h) or more, preferably 1 kg / (m ² · h) or more, more preferably 3 kg / (m ² · h) or more. The upper limit of the permeation flux is not particularly limited, and is usually 30 kg / (m ² · h) or less, preferably 20 kg / (m ² · h) or less.

In addition, when a mixture of 2-propanol or N-methyl-2-pyrrolidone having a water content of 30% by mass and water is permeated at 70 ° C. with a pressure difference of 1 atm (1.01 × 10 ⁵ Pa), 1 kg / (M ² · h) or more, preferably 3 kg / (m ² · h) or more, more preferably 5 kg / (m ² · h) or more. The upper limit of the permeation flux is not particularly limited, and is usually 20 kg / (m ² · h) or less, preferably 15 kg / (m ² · h) or less.

Further, high transmission performance can be expressed by permeance (also referred to as “permeance”). Permeance refers to the pressure normalized flux, divided by the product of membrane area, time, and water partial pressure difference. When expressed in units of permeance, for example, a mixture of acetic acid and water having a water content of 10% by mass permeated at 90 ° C. with a pressure difference of 1 atm (1.01 × 10 ⁵ Pa). Usually, 3 × 10 ⁻⁷ mol / (m ² · s · Pa) or more, preferably 5 × 10 ⁻⁷ mol / (m ² · s · Pa) or more, more preferably 1 × 10 ⁻⁶ mol / (m ² · s · Pa) or more. The upper limit of permeance is not particularly limited, and is usually 1 × 10 ⁻⁴ mol / (m ² · s · Pa) or less, preferably 5 × 10 ⁻⁵ mol / (m ² · s · Pa) or less.

Further, when a mixture of phenol and water having a water content of 10% by mass is permeated at 75 ° C. with a pressure difference of 1 atm (1.01 × 10 ⁵ Pa), and 2-propanol having a water content of 30% by mass or When a mixture of N-methyl-2-pyrrolidone and water is permeated at 70 ° C. with a pressure difference of 1 atm (1.01 × 10 ⁵ Pa), the water permeance is usually 3 × 10 ⁻⁷ mol / mol. (M ² · s · Pa) or more, preferably 5 × 10 ⁻⁷ mol / (m ² · s · Pa) or more, more preferably 1 × 10 ⁻⁶ mol / (m ² · s · Pa) or more, in particular It is preferably 2 × 10 ⁻⁶ mol / (m ² · s · Pa) or more. The upper limit of permeance is not particularly limited, and is usually 1 × 10 ⁻⁴ mol / (m ² · s · Pa) or less, preferably 5 × 10 ⁻⁵ mol / (m ² · s · Pa) or less.

Selectivity is represented by a separation factor. The separation factor is the following index representing the selectivity generally used in membrane separation.
Separation factor = (P _α / P _β ) / (F _α / F _β )
[Where P _α is the mass percent concentration of the main component in the permeate, P _β is the mass percent concentration of the subcomponent in the permeate, and F _α is the mass of the component that is the main component in the permeate in the mixture to be separated. The percent concentration, _Fβ, is the mass percent concentration in the separated mixture of components that are subcomponents in the permeate. ]

The separation factor is, for example, when a mixture of acetic acid and water having a water content of 10% by mass is permeated at 90 ° C. with a pressure difference of 1 atm (1.01 × 10 ⁵ Pa), and for example having a water content of 10% by mass. When a mixture of phenol and water is permeated at 75 ° C. with a pressure difference of 1 atm (1.01 × 10 ⁵ Pa), and for example 2-propanol or N-methyl-2-pyrrolidone with a water content of 30% by weight When the mixture of water and water is permeated at 70 ° C. with a pressure difference of 1 atm (1.01 × 10 ⁵ Pa), it is usually 2000 or more, preferably 4000 or more, more preferably 10,000 or more, particularly preferably 20000 or more. It is. The upper limit of the separation factor is the case where only water is completely transmitted. In this case, the separation factor is infinite, but is preferably 10000000 or less, more preferably 1000000 or less.

As a water-containing organic compound, the water content may be adjusted in advance by an appropriate water adjustment method. Examples of the moisture adjustment method include methods known per se, such as distillation, pressure swing adsorption (PSA), temperature swing adsorption (TSA), and desiccant system.
Further, water may be further separated from the water-containing organic compound from which water has been separated by the zeolite membrane composite. Thereby, water can be separated to a higher degree and the water-containing organic compound can be further concentrated.

  Examples of organic compounds include carboxylic acids such as acetic acid, acrylic acid, propionic acid, formic acid, lactic acid, oxalic acid, tartaric acid, benzoic acid, sulfonic acid, sulfinic acid, habituric acid, uric acid, phenol, enol, and diketone type compounds. Organic acids such as thiophenol, imide, oxime, aromatic sulfonamide, primary and secondary nitro compounds; alcohols such as methanol, ethanol and isopropanol (2-propanol); ketones such as acetone and methyl isobutyl ketone Aldehydes such as acetaldehyde, ethers such as dioxane and tetrahydrofuran; organic compounds containing nitrogen such as amides such as dimethylformamide and N-methylpyrrolidone (N-containing organic compounds), esters such as acetates and acrylates Na And the like.

Among these, the effect of the inorganic porous support-zeolite membrane composite stands out when separating the organic acid from a mixture of organic acid and water that can take advantage of both the characteristics of molecular sieve and hydrophilicity. To express. A preferred example is a mixture of carboxylic acids and water, particularly preferably separation of acetic acid and water.
In addition, the organic substance in the case of separating the organic substance and water from the mixture of the organic substance other than the organic acid and water preferably has 2 or more carbon atoms, and more preferably 3 or more carbon atoms.

Among these organic substances other than organic acids, organic compounds containing at least one selected from alcohols, ethers, ketones, aldehydes, and amides are particularly desirable. Among these organic compounds, those having 2 to 10 carbon atoms are preferable, and those having 3 to 8 carbon atoms are more preferable.
Moreover, as an organic compound, the high molecular compound which can form a mixture (mixed solution) with water may be sufficient. Examples of such a polymer compound include those having a polar group in the molecule, for example, polyols such as polyethylene glycol and polyvinyl alcohol; polyamines; polysulfonic acids; polycarboxylic acids such as polyacrylic acid; Carboxylic acid esters; modified polymer compounds obtained by modifying polymers by graft polymerization, etc .; copolymerized polymer compounds obtained by copolymerization of nonpolar monomers such as olefins and polar monomers having polar groups such as carboxyl groups And the like.

  The water-containing organic compound may be a mixture that forms an azeotrope, such as a mixture of water and phenol. In the separation of a mixture that forms an azeotrope, water is selectively used rather than separation by distillation. It is preferable in terms of efficient separation. Specifically, a mixture of alcohols such as ethanol, 1-propanol, 2-propanol, 1-butanol and 2-butanol and water; a mixture of esters and water such as ethyl acetate, ethyl acrylate and methyl methacrylate; A mixture of carboxylic acids such as formic acid, isobutyric acid, valeric acid and water; a mixture of aromatic organic substances such as phenol and aniline and water; a mixture of nitrogen-containing compounds such as acetonitrile and acrylonitrile and water, and the like.

  Further, the water-containing organic compound may be a mixture of water and a polymer emulsion. Here, the polymer emulsion is a mixture of a surfactant and a polymer, which is usually used for adhesives, paints, and the like. Examples of the polymer used in the polymer emulsion include polyvinyl acetate, polyvinyl alcohol, acrylic resin, polyolefin, olefin-polar monomer copolymer such as ethylene-vinyl alcohol copolymer, polystyrene, polyvinyl ether, polyamide, polyester, and cellulose. Thermoplastic resins such as derivatives; thermosetting resins such as urea resins, phenol resins, epoxy resins, polyurethanes; rubbers such as natural rubber, polyisoprene, polychloroprene, butadiene copolymers such as styrene-butadiene copolymers, etc. Can be mentioned. As the surfactant, a known one may be used.

In the method of the present invention, the mixture to be separated or concentrated may be a mixed gas, such as carbon dioxide, oxygen, nitrogen, methane, ethane, ethylene, propane, propylene, normal butane, isobutane, 1 Examples include those containing at least one component selected from -butene, 2-butene, isobutene, sulfur hexafluoride, helium, carbon monoxide, nitrogen monoxide, water and the like. Among these gas components, the gas component with high permeance passes through the zeolite membrane complex and is separated, and the gas component with low permeance is concentrated on the supply gas side.

  In particular, the mixed gas preferably contains at least one gas molecule having a kinetic diameter of 4 mm or less. According to the present invention, particularly in a gas containing at least one of components having a kinetic diameter of 4 mm or less as a component, a component having low permeability due to separation of a component having high permeability or permeation of a component having high permeability. Can be concentrated with high separation performance.

The mixed gas includes at least two components of the above components. In this case, the two components are preferably a combination of a component having a high permeance and a component having a low permeance. Here, permeance (also referred to as “permeance”) is obtained by dividing the amount of the permeated substance by the product of the membrane area, time, and the partial pressure difference between the permeating substance supply side and the permeating side. [Mol · (m ² · s · Pa) ⁻¹ ].

  Specific examples of the mixed gas include a mixed gas containing oxygen, a mixed gas containing methane and helium, a mixed gas containing carbon dioxide and nitrogen, air, natural gas, combustion gas, coke oven gas, It can be used for separation or concentration of biogas such as land file gas generated from a landfill, and steam reformed gas of methane produced and discharged in the petrochemical industry.

When a mixed gas containing oxygen is used, it is preferably used to separate oxygen from the mixed gas or to allow oxygen to permeate from the mixed gas. Examples of the mixed gas containing oxygen include air.
When a mixed gas containing methane and helium is used, it is preferably used to separate helium from the mixed gas or to transmit helium from the mixed gas. Examples of the mixed gas containing methane and helium include natural gas.

When a mixed gas containing carbon dioxide and nitrogen is used, it is preferably used to separate carbon dioxide from the mixed gas or to allow carbon dioxide to permeate from the mixed gas. Examples of the mixed gas containing carbon dioxide and nitrogen include combustion gases.
Oxygen is highly permeable to the zeolite membrane used in the present invention. Therefore, by bringing the mixed gas containing oxygen into contact with the zeolite membrane and separating it, the oxygen-containing mixed gas, for example, the oxygen concentration in the air can be increased, and a high-oxygen-concentrated mixed gas can be produced. it can.

For example, when air is used as the mixed gas, the oxygen concentration can be 30% or more, and further 35% or more.
Moreover, helium has high permeability with respect to the zeolite membrane used in the present invention. Therefore, helium can be separated by contacting the zeolite membrane with, for example, natural gas containing helium or methane.

In addition, carbon dioxide has high permeability with respect to the zeolite membrane used in the present invention. Therefore, carbon dioxide can be separated by bringing the zeolite membrane into contact with, for example, a combustion gas containing carbon dioxide or nitrogen.
The conditions for separating and concentrating these mixed gases may be those known per se according to the target gas species, composition, and the like.

As a form of the separation membrane module having the zeolite membrane composite used for the separation of the mixed gas, a flat membrane type, a spiral type, a hollow fiber type, a cylindrical type, a honeycomb type, and the like can be considered, and an optimum form according to the application target is provided. To be elected.
One example is a cylindrical separation membrane module.
In FIG. 1, a cylindrical zeolite membrane composite 1 is installed in a thermostatic chamber (not shown) in a state of being stored in a pressure vessel 2 made of stainless steel. A temperature control device is attached to the thermostat so that the temperature of the sample gas can be adjusted.

  One end of the cylindrical zeolite membrane composite 1 is sealed with a cylindrical end pin 3. The other end is connected by a connecting portion 4, and the other end of the connecting portion 4 is connected to the pressure vessel 2. An inner side of the cylindrical zeolite membrane composite and a pipe 11 for discharging the permeated gas 8 are connected via the connection portion 4, and the pipe 11 extends to the outside of the pressure-resistant vessel 2. A pressure gauge 5 for measuring the pressure on the supply side of the sample gas is connected to the pressure vessel 2. Each connection part is connected with good airtightness.

In FIG. 1, a cylindrical zeolite membrane composite 1 is installed in a thermostatic chamber (not shown) in a state of being stored in a pressure vessel 2 made of stainless steel. A temperature control device is attached to the thermostat so that the temperature of the sample gas can be adjusted.
One end of the cylindrical zeolite membrane composite 1 is sealed with a circular end pin 3. The other end is connected by a connection portion 4, and the other end of the connection portion 4 is connected to the pressure vessel 2. A pipe 11 that discharges the permeate gas 8 and the inside of the cylindrical zeolite membrane composite 1 are connected via a connecting portion 4, and the pipe 11 extends to the outside of the pressure vessel 2. A pipe 12 for supplying the sweep gas 9 is inserted into the zeolite membrane composite 1 via the pipe 11. Furthermore, a pressure gauge 5 for measuring the pressure on the supply side of the sample gas (mixed gas) and a back pressure valve 6 for adjusting the pressure on the supply side are connected to any part that communicates with the pressure vessel 2. Each connection part is connected with good airtightness.

A sample gas (supply gas 7) is supplied between the pressure vessel 2 and the zeolite membrane composite 1 at a constant flow rate, and the pressure on the supply side is made constant by the back pressure valve 6. The gas passes through the membrane 1 according to the partial pressure difference between the inside and outside of the membrane 1 and is discharged through the pipe 11.
The gas separation temperature from the mixed gas is 0 to 500 ° C. Considering the separation characteristics of the membrane, the temperature is preferably within the range of room temperature to 100 ° C.

Hereinafter, the present invention will be described more specifically based on experimental examples (Examples and Comparative Examples). However, the present invention is not limited to the following experimental examples unless it exceeds the gist.
In addition, the values of various production conditions and evaluation results in the following examples have meanings as preferable values of the upper limit or the lower limit in the embodiment of the present invention, and the preferable range is the value of the upper limit or the lower limit. It may be a range defined by a combination of values of the following examples or values of the examples.

Example 1
A zeolite membrane composite was prepared by hydrothermal synthesis of CHA-type zeolite directly on a porous support.
The following was prepared as a reaction mixture for hydrothermal synthesis.
A mixture of 38.57 g of 10 mol / L-NaOH aqueous solution, 129.77 g of 25% -KOH aqueous solution and 6183 g of water was mixed with 46.84 g of aluminum hydroxide (containing 53.5% by mass of Al ₂ O ₃ , manufactured by Aldrich). In addition, the mixture was stirred and dissolved to obtain a transparent solution. As an organic template, 143.52 g of an aqueous N, N, N-trimethyl-1-adamantanammonium hydroxy (TMADOH) solution (containing 25% by weight of TMADAOH, manufactured by Seychem) was added, and colloidal silica (Snowtech manufactured by Nissan Chemical Co., Ltd.) was added. 40) Add 700.53 g and stir for 2 hours to prepare an aqueous reaction mixture.

As the porous support, cylindrical tubular alumina (outer diameter 16 mm, inner diameter 12 mm) having a length of 100 cm was used. Prior to hydrothermal synthesis, SiO ₂ / Al ₂ O ₃ / NaOH / KOH / H ₂ O / TMADOH = 1 / 0.033 / 0.1 is formed on the support by the dipping method in the same manner as described above. A seed crystal of CHA-type zeolite crystallized by hydrothermal synthesis at 160 ° C. for 2 days with a gel composition of /0.06/40/0.07 was attached.

  The support to which the seed crystal was attached was placed upright in a vertical direction using a jig in a SUS reaction can having an inner diameter of 5 cm and a height of 115 cm containing the reaction mixture, and immersed in the reaction solution. The autoclave was sealed and heated at 160 ° C. for 48 hours under autogenous pressure. After the elapse of a predetermined time, the substrate was allowed to cool, and then the support was taken out from the reaction mixture, washed, and dried at 120 ° C. for 2 hours or more.

After drying, sealing one end of the cylindrical tubular support as it is, connecting the other end to a vacuum line, reducing the pressure inside the tube, and measuring the amount of air permeated with a flow meter installed in the vacuum line The permeation amount was 0 ml / (m ² · min). The support on which the zeolite before template firing was formed was fired in an electric furnace at 500 ° C. for 5 hours.
The support on which the zeolite membrane thus formed was placed in a 100 ° C. constant temperature bath and left to stand for 1 hour to dry, thereby setting the support on which the zeolite membrane was formed to 100 ° C. Then, the top and bottom were plugged with silicone rubber plugs so as to seal the inside of the support. At this time, a Teflon (registered trademark) tube was passed through the upper silicone rubber stopper, and the Teflon (registered trademark) tube and a vacuum pump were connected.

Subsequently, as a surface treatment solution, a methyl silicate oligomer heated to 100 ° C. (MKC (registered trademark) silicate MS51 manufactured by Mitsubishi Chemical Corporation, 52.0 ± 1.0 as SiO ₂ content)
%) Was immersed so that the entire support on which the zeolite membrane was formed was immersed, and then the inside of the support was depressurized by a vacuum pump for 1 minute.
Thereafter, the support is pulled up, allowed to stand in a constant temperature bath at 100 ° C. for 60 minutes, heated in a container coexisting with water at 105 ° C. for 5 hours, and further heated in a dryer at 150 ° C. for 1 hour. A membrane complex was obtained.

The zeolite membrane composite was separated by selectively permeating water from a water / isopropanol (IPA) mixed solution (10/90% by mass) by vapor permeation. The permeation results after 4 hours were a permeation flux: 9.1 kg / (m ² · h) and an IPA concentration in the permeate: 120 ppm.

(Example 2)
After immersion in the surface treatment solution, a zeolite membrane composite was obtained in the same manner as in Example 1 except that the standing time in a constant temperature bath at 100 ° C. was 5 minutes.
In the same manner as in Example 1, separation of selectively permeating water from the IPA mixed solution resulted in a permeation flux of 7.0 kg / (m ² · h) and an IPA concentration in the permeate of 210 ppm. It was.

(Example 3)
After being immersed in the surface treatment liquid and allowed to stand for 80 minutes in a 100 ° C. constant temperature bath, the temperature of the support on which the zeolite membrane was formed was cooled to 25 ° C. and left to stand for 20 minutes. Similarly, a zeolite membrane composite was obtained.
In the same manner as in Example 1, separation of selectively permeating water from the IPA mixed solution resulted in a permeation flux of 7.1 kg / (m ² · h) and an IPA concentration in the permeate of 180 ppm. It was.

Example 4
The steps until the support on which the zeolite membrane was formed were fired in an electric furnace were performed in the same manner as in Example 1, and the subsequent steps were performed as follows.
The top and bottom were plugged with silicone rubber plugs to seal the inside of the support on which the zeolite membrane was formed. At this time, a Teflon (registered trademark) tube was passed through the upper silicone rubber stopper, and the Teflon (registered trademark) tube was passed through the wall surface of the sealed container using a penetration joint, and connected to a vacuum pump.
Subsequently, the sealed container was heated to 130 ° C., and the inside of the support on which the zeolite membrane was formed was dried for 1 hour while reducing the pressure. Thereafter, a methyl silicate oligomer heated to 130 ° C. was injected into the sealed container, and the entire support on which the zeolite membrane was formed was immersed, and then the inside of the support was depressurized for 1 minute by a vacuum pump.
Thereafter, the methyl silicate oligomer was extracted and allowed to stand for 60 minutes while being maintained at 130 ° C., and then water was poured therein. The mixture was immediately sealed and heated for 5 hours. Furthermore, while circulating heated air into the container, it was heated at 150 ° C. for 1 hour to obtain a zeolite membrane composite.
In the same manner as in Example 1, separation of selectively permeating water from the IPA mixed solution resulted in a permeation flux of 7.2 kg / (m ² · h) and an IPA concentration in the permeate of 30 ppm. It was.
(Comparative Example 1)
The temperature of the support on which the zeolite membrane was formed when immersed in the surface treatment liquid was 25 ° C., the temperature of the surface treatment liquid was also 25 ° C., and the inside of the tube was depressurized, and the support was removed from the surface treatment liquid. After raising, a zeolite membrane composite was obtained in the same manner as in Example 1 except that the support was kept at 25 ° C. for 300 minutes without being left in a 100 ° C. constant temperature bath for 1 hour.

In the same manner as in Example 1, separation of selectively permeating water from the IPA mixed solution resulted in a permeation flux of 7.2 kg / (m ² · h) and an IPA concentration in the permeate of 8860 ppm. It was.
As described above, according to the present invention, it has been found that a zeolite membrane composite having a high throughput and high separation performance can be obtained.

1. 1. Zeolite membrane composite 2. Pressure vessel End pin 4. Connection part 5. Pressure gauge 6. Back pressure valve 7. Supply gas 8. Permeated gas 9. Sweep gas10. Exhaust gas 11. Piping 12. Piping 13. Constant temperature bath 14. Zeolite membrane composite module 15. Separation liquid collecting trap 16. Permeate collection trap 17. Cold trap 18. Vacuum pump 19. Liquid to be separated20. Liquid feed pump 21. Vaporizer

Claims (5)

A method for producing a porous support-zeolite membrane composite having a zeolite membrane on a porous support,
After preparing a zeolite membrane containing an organic template on a porous support by hydrothermal synthesis,
A zeolite membrane is formed by firing the zeolite membrane containing the organic template at 350 ° C or higher.
After obtaining the porous support made,
The temperature of the porous support on which the zeolite membrane is formed is 50 ° C. or higher ,
Thereafter, the zeolite membrane is subjected to a surface treatment using a surface treatment solution at 80 ° C. or higher, and a method for producing a porous support-zeolite membrane composite is characterized. The method for producing a porous support-zeolite membrane composite according to claim 1, wherein the surface treatment is performed with a material containing Si atoms. The porous support-zeolite membrane composite according to claim 1 or 2, wherein the zeolite membrane is formed by hydrothermal synthesis in an aqueous reaction mixture containing a Si element source, an Al element source, an alkali source and water. Production method. The method for producing a porous support-zeolite membrane composite according to any one of claims 1 to 3, wherein the porous support is a tubular support. The method for producing a porous support-zeolite membrane composite according to claim 4, wherein the inside of the tubular support is subjected to a surface treatment by reducing the pressure.

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