JP6213062B2 - Method for separating or concentrating gas and method for producing high oxygen concentration mixed gas - Google Patents

Description

  The present invention relates to a gas separation or concentration method that uses a zeolite separation membrane to separate a highly permeable substance by permeating and separating a highly permeable substance from a mixed gas containing a plurality of gas components. .

  Gas separation / concentration methods include membrane separation method, adsorption separation method, absorption separation method, distillation separation method, cryogenic separation method, etc., but membrane separation method is almost accompanied by phase change during the separation. First, the pressure difference is used as driving energy, and the separation is performed by the difference in velocity of the gas passing through the membrane. Separation by adsorption / absorption requires a process of desorbing the adsorbed / absorbed gas and is a batch process, so multiple units are required to make a continuous process. This is possible and the equipment scale can be made relatively small. Distillation and cryogenic separation methods can be processed continuously, but a large amount of energy is required with the phase change in the separation. However, in the membrane separation method, energy-saving separation using a pressure difference as a driving force is possible.

As a gas separation method using a membrane, a method using a polymer membrane has been proposed since the 1970s. However, while the polymer film has the characteristics of excellent processability, it has a problem that the performance deteriorates due to deterioration due to heat, chemical substances, and pressure, and the usable condition range is not sufficient.
In order to solve these problems, inorganic films having good chemical resistance, oxidation resistance, heat resistance, and pressure resistance have been proposed. Examples of inorganic films include dense films such as Pd films and composite oxide films, and porous films such as silica films and zeolite films. In the case of a dense membrane, separation is based on the principle of dissolution and diffusion. However, in the case of a porous membrane, separation is performed using molecular sieving and adsorptivity, and components that do not dissolve in the membrane can be separated. Among them, the zeolite membrane has crystallinity and has regular sub-nanometer pores, so the pore diameter is uniform, the molecular sieving effect is high, and the separation performance is excellent. Adsorption control can also be expected by changing the composition. Furthermore, since it is crystalline, it is excellent in stability as compared with an amorphous silica film or the like.

Known zeolite membranes for gas separation include zeolite membranes such as A-type membranes, FAU membranes, MFI membranes, SAPO-34 membranes, and DDR membranes. Specific examples of mixed gas membrane separation include separation of gaseous fossil resources and separation of gas discharged from thermal power plants and petrochemical industries, etc. There are separation of hydrocarbon, hydrogen and oxygen, hydrogen and carbon dioxide, nitrogen and oxygen, paraffin and olefin, helium and methane, etc.
Among the zeolite membranes that can be used, the A-type zeolite membrane has poor water vapor stability, and it is difficult to form a membrane without crystal gaps, so that there are many gases passing through the crystal gaps, and the separation performance is not sufficient. The FAU membrane has a zeolite pore size of 0.6 to 0.8 nm, and has a size that allows two small gas molecules such as hydrogen to enter the zeolite pores. No sifting effect can be expected. This membrane is suitable for the separation of molecules that do not have adsorption properties into zeolite pores, for example, separation of carbon dioxide and nitrogen. However, non-adsorbing molecules are difficult to separate and have a narrow application range. The pore diameter of the MFI membrane is 0.55 nm, and this also has a slightly large pore for separating gas molecules, as in the FAU membrane, and the separation performance is not high.
DDR (patent document 1), SAPO-34 (non-patent document 1), and SSZ-13 (non-patent document 2) are known as membranes having small pore diameters and suitable for separating small gases. Further, the present inventors have proposed a zeolite membrane composite having excellent permeability, water resistance, and separation properties and a gas separation method using the zeolite membrane, which are problems of these membranes (Patent Document 2).

JP 2004-105942 A JP 2012-066242 A

Shiguang Li et al., "Improved SAPO-34 Membranes for CO2 / CH4 Separation", Adv. Mater. 2006, 18, 2601-2603 Halil Kalipcilar et al., "Synthesis and Separation Performance of SSZ-13 Zeolite Membranes on Tubular Supports", Chem. Mater. 2002, 14, 3458-3464

The pore diameters of these membranes are the crystallographic channel diameters determined by International Zeolite Association (IZA), DDR is 3.6 × 4.4 mm, and 3 for CHA, which is the crystal structure of SAPO-34 and SSZ-13. .8 × 3.8 mm. On the other hand, the kinetic diameters of gases expected to be separated are, for example, 2.6 ヘ リ ウ ム for helium molecules, 3.5 は for oxygen molecules, and 3.6 窒 素 for nitrogen molecules, which are larger than the major diameter of the pore size of DDR and CHA membranes. Small (kinetic diameter: Laurence W McKeen, Film Properties of Plastics and Elastomers Third Edition, Elsevier, 2012)
.

When separating and concentrating a gas mixture that has such a relationship between pore size and molecular size, any gas molecule can permeate the membrane, so separation by molecular size order and diffusion rate is possible. Also, the molecular sieving effect did not work, and the separation performance was not sufficient.
The present invention provides a method for separating or concentrating a gas mixture containing a gas having a size of 4 mm or less, in which various small kinetic diameter gases can be separated with high separability. The issue is to provide.
Another object of the present invention is to provide a method for producing a mixed gas having a high oxygen concentration by utilizing a separation or concentration method.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that a zeolite membrane composite having certain physical properties has excellent characteristics for separating a gas mixture, and reached the present invention.
That is, the gist of the present invention resides in the following (1) to (15).
(1) A gas mixture containing a plurality of gas components is brought into contact with a separation membrane, and the highly permeable component is separated from the mixed gas by allowing a highly permeable component to pass through the mixed gas. Alternatively, a gas separation or concentration method for condensing a low-permeability component by permeating a high-permeability component from the mixed gas,
The separation membrane is a zeolite membrane formed on an inorganic porous support, and the zeolite membrane contains a zeolite having a pore structure of an oxygen 8-membered ring or less,
A method for separating or concentrating a gas, wherein the zeolite membrane surface has a SiO ₂ / Al ₂ O ₃ molar ratio of 50 or more, which is a numerical value obtained by X-ray photoelectron analysis (XPS) .
(2) The gas separation or concentration method according to (1), wherein the mixed gas is a mixed gas containing oxygen, and oxygen is separated from the mixed gas or oxygen is permeated from the mixed gas. (3) The gas mixture according to (1), wherein the gas mixture is a gas mixture containing methane and helium, and helium is separated from the gas mixture, or helium is permeated from the gas mixture. Separation or concentration method.
(4) The gas according to (1), wherein the mixed gas is a mixed gas containing carbon dioxide and nitrogen, and carbon dioxide is separated from the mixed gas or carbon dioxide is permeated from the mixed gas. Separation or concentration method.
(5) The zeolite membrane according to any one of (1) to (4), which is obtained by forming a zeolite by hydrothermal synthesis and then treating it in a solution containing an Si compound. Separation or concentration method.
(6) The natural gas is brought into contact with the separation membrane, and the highly permeable component of the natural gas is permeated to separate the highly permeable component from the natural gas, or the highly permeable component from the natural gas. A method for separating or concentrating natural gas by concentrating components with low permeability by permeating the components,
The separation membrane is a zeolite membrane formed on an inorganic porous support, and the zeolite membrane contains zeolite having a pore structure of an oxygen 8-membered ring or less, and is obtained by X-ray photoelectron analysis (XPS). A method for separating or concentrating natural gas, wherein the zeolite membrane surface SiO ₂ / Al ₂ O ₃ molar ratio, which is a numerical value obtained, is 50 or more.
(7) The natural gas separation or concentration method according to (6), wherein the highly permeable component is helium.
(8) By separating the highly permeable component from the combustion gas by bringing the combustion gas into contact with the separation membrane and permeating the highly permeable component of the combustion gas, or having a high permeability from the combustion gas. A method for separating or concentrating a combustion gas that concentrates a component with low permeability by permeating the component,
The separation membrane is a zeolite membrane formed on an inorganic porous support, and the zeolite membrane contains a zeolite having a pore structure of an oxygen 8-membered ring or less,
A method for separating or concentrating combustion gas, wherein the zeolite membrane surface has a SiO ₂ / Al ₂ O ₃ molar ratio of 50 or more, which is a numerical value obtained by X-ray photoelectron analysis (XPS) . (9) The natural gas separation or concentration method according to (8), wherein the highly permeable component is carbon dioxide.
(10) A method for producing a mixed gas having a high oxygen concentration by bringing a mixed gas containing oxygen into contact with a separation membrane, wherein the separation membrane is a zeolite membrane formed on an inorganic porous support. Yes,
The zeolite membrane includes a zeolite having a pore structure having an oxygen 8-membered ring or less,
A method for producing a high oxygen concentration mixed gas, wherein the zeolite membrane surface has a SiO ₂ / Al ₂ O ₃ molar ratio of 50 or more, which is a numerical value obtained by X-ray photoelectron analysis (XPS) .

  According to the present invention, it is possible to increase the difference in permeability between a component having high permeability and a component having low permeability from a gas composed of a plurality of components. In particular, at least one of the components includes a component having a kinetic diameter of 4 mm or less. Even in a gas, it is possible to separate components with high permeability, or concentrate components with low permeability by transmitting components with high permeability with high separation performance.

Schematic diagram of measuring device used for gas separation XRD pattern of zeolite membrane formed on the inorganic porous support of Example 3 XRD pattern of powdered CHA-type zeolite

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.
In the gas separation or concentration method of the present invention, a mixed gas containing a plurality of gas components is brought into contact with a separation membrane, and a highly permeable component of the mixed gas is allowed to permeate from the mixed gas. A gas separation or concentration method for concentrating a low-permeability component by separating a high-permeability component or by allowing a high-permeability component to permeate from the mixed gas, wherein the separation membrane is inorganic porous A zeolite membrane formed on a porous support, the zeolite membrane comprising a zeolite having a pore structure of an oxygen 8-membered ring or less, and a SiO ₂ / Al ₂ O ₃ molar ratio on the surface of the zeolite membrane of 25 or more It is characterized by being.

First, the zeolite membrane formed on the inorganic porous support, which is a feature of the present invention, will be described.
In the present specification, the inorganic porous support and the zeolite membrane formed thereon may be referred to as “zeolite membrane composite”, which may be abbreviated as “membrane composite”. In addition, the “inorganic 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 the gas mixture can be effectively separated. Specifically, for example, a flat plate, a tube, or a cylindrical, columnar or prismatic hole is provided. There are many honeycomb-shaped materials and monoliths.
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 tube 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 tube 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.
In addition to zeolite, the components constituting the zeolite membrane include inorganic binders such as silica and alumina, organic compounds such as polymers, Si compounds that modify the zeolite surface as detailed below, or reactants thereof as necessary. You may go out. In addition, the zeolite membrane in the present invention may partially contain an amorphous component or the like, but a zeolite membrane substantially consisting only of zeolite is preferable.

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.

In the present invention, the molar ratio of SiO ₂ / Al ₂ O ₃ on the zeolite membrane surface (hereinafter sometimes referred to as “SAR on the membrane surface”) is 25 or more.
The zeolite is preferably an aluminosilicate.
The SiO ₂ / Al ₂ O ₃ molar ratio on the zeolite membrane surface is a numerical value obtained by X-ray photoelectron spectroscopy (XPS). XPS is an analysis method for obtaining information on the film surface, and the SAR on the film surface can be obtained by this analysis method.

The SiO ₂ / Al ₂ O ₃ molar ratio on the zeolite membrane surface may be 25 or more, more preferably 28 or more, still more preferably 30 or more, still more preferably 32 or more, particularly preferably 50 or more, and most preferably 80 or more, preferably 3000 or less, more preferably 2000 or less, further preferably 1000 or less, particularly preferably 500 or less, and most preferably 300 or less. It is considered that when the SiO ₂ / Al ₂ O ₃ molar ratio on the zeolite membrane surface is 25 or more, the pore diameter of the membrane surface on the membrane surface is narrowed and the separation performance is improved. Further, since the SAR on the film surface is not more than the upper limit, there is an advantage that the permeability is not reduced in terms of adsorptivity.

The SiO ₂ / Al ₂ O ₃ molar ratio of the zeolite membrane itself is preferably 5 or more, more preferably 8 or more, still more preferably 10 or more, particularly preferably 12 or more, preferably 2000 or less, more preferably 1000 or less. More preferably, it is 500 or less, more preferably 100 or less, particularly preferably 50 or less. When the SAR of the membrane itself is equal to or higher than the lower limit, durability tends to be improved. When the SAR is equal to or lower than the upper limit, there is an advantage that the permeability is not reduced in terms of adsorptivity.

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.

  In the present invention, the SAR on the film surface is preferably 20 or more larger than the SAR on the film itself, but this value (a value obtained by subtracting the SAR on the film itself from the SAR on the film surface) is more preferably 22 Above, more preferably 25 or more, particularly preferably 30 or more. The upper limit of this value is not particularly limited, but is usually 1000 or less, preferably 700 or less, more preferably 500 or less, and particularly preferably 400 or less.

When the above value (the value obtained by subtracting the SAR of the membrane itself from the SAR of the membrane surface) is 20 or more, it is considered that the pore diameter on the membrane surface is narrowed and the separation performance is improved.
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, 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, LTN, MAR, and 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 pore size of the zeolite, and in zeolites smaller than the oxygen 6-membered ring, the pore diameter is smaller than the kinetic diameter of the H ₂ O molecule, so the permeability is reduced and practical. It may not be. In addition, when it is larger than the oxygen 8-membered ring structure, the pore diameter becomes large, and a gas component having a small size may lower the separation performance, which may limit the application.

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 framework density and zeolite structure is shown in ATLAS OF ZEOLITE FRAMEWORK TYPES Fifth Revised Edition 2001 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, TOL and UFI are more preferable structures, and AEI, CHA, ERI, KFI, LEV, PAU, RHO, RTH, and UFI are more preferable structures. CHA and LEV are more preferable structures, and CHA is the most preferable structure.

  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.

The X-ray diffraction pattern here refers to the surface on the side where the zeolite is mainly attached.
X-rays with uKα as a radiation source are irradiated to obtain a scanning axis of θ / 2θ. The shape of the sample to be measured may be any shape that can irradiate the surface of the membrane composite to which the zeolite is mainly attached, with X-ray irradiation. The body itself or the one cut into an appropriate size restricted by the apparatus is preferable.

Here, the X-ray diffraction pattern may be measured by fixing the irradiation width using an automatic variable slit when the surface of the zeolite membrane composite is a curved surface. An X-ray diffraction pattern using an automatic variable slit refers to a pattern in which variable → fixed slit correction is performed.
Here, the peak in the vicinity of 2θ = 17.9 ° refers to the maximum of the peaks present in the range of 17.9 ° ± 0.6 ° among the peaks not derived from the base material.

The peak in the vicinity of 2θ = 20.8 ° refers to the maximum peak in the range of 20.8 ° ± 0.6 ° among the peaks not derived from the base material.
The peak in the vicinity of 2θ = 9.6 ° refers to the maximum of the peaks present in the range of 9.6 ° ± 0.6 ° among the peaks not derived from the base material.
According to COLLECTION OF SIMULATED XRD POWTER PATTERNS FOR ZEOLITE Third Revised Edition 1996 ELSEVIER (hereinafter sometimes referred to as “Non-Patent Document 1”), the peak near 2θ = 9.6 ° in the X-ray diffraction pattern is rhombohedral. Set the space group

(No. 166), it is a peak derived from the plane having an index of (1, 0, 0) in the CHA structure.
Further, in the X-ray diffraction pattern, the peak around 2θ = 17.9 ° is a space group in rhombohedral setting according to Non-Patent Document 1.

(No. 166) is a peak derived from the (1,1,1) index in the CHA structure.
According to Non-Patent Document 1, the peak near 2θ = 20.8 ° in the X-ray diffraction pattern is a space group in the rhombohedral setting.

(No. 166) is a peak derived from the (2, 0, -1) index in the CHA structure.
The typical ratio (peak intensity ratio B) of the peak intensity derived from the (2, 0, -1) plane of the peak intensity derived from the (1, 0, 0) plane in the CHA type aluminosilicate zeolite membrane is Halil Kalipcilar et al., “Synthesis and Separation Performance of SSZ-13 Zeolite Membranes on Tubular Supports”, Chem. Mater. 2002, 14, 3458-3464 (hereinafter sometimes referred to as “Non-Patent Document 2”). ) Is less than 2.

Therefore, this ratio of 2 or more means that, for example, the zeolite crystal is oriented so that the (1, 0, 0) plane when the CHA structure is a hombohedral setting is oriented almost parallel to the surface of the membrane composite. Is considered to mean that the crystals are oriented and growing. Orientation and growth of zeolite crystals in the zeolite membrane composite is advantageous in that a dense membrane with high separation performance can be formed.

The typical ratio (peak intensity ratio A) of the peak intensity derived from the (1, 1, 1) plane and the peak intensity derived from the (2, 0, -1) plane in the CHA type aluminosilicate zeolite membrane is According to Non-Patent Document 2, it is less than 0.5.
Therefore, this ratio of 0.5 or more means, for example, that the (1, 1, 1) plane when the CHA structure is a rhombohedral setting is oriented so that the orientation is almost parallel to the surface of the membrane composite. It is thought to mean that the crystals are oriented and growing. Orientation and growth of zeolite crystals in the zeolite membrane composite is advantageous in that a dense membrane with high separation performance can be formed.

As described above, the fact that any one of the peak intensity ratios A and B is a value in the above-mentioned specific range means that the zeolite crystals are oriented and grow, and a dense membrane with high separation performance is formed. Is shown.
The peak intensity ratios A and B indicate that the larger the value, the stronger the degree of orientation, and generally the stronger the degree of orientation, the more dense the film is formed. In general, the stronger the orientation, the higher the separation performance tends to be. However, the optimum degree of orientation in which the separation performance becomes higher differs depending on the mixture to be separated. It is desirable to select and use the membrane complex.

<Method for producing zeolite membrane composite>
In the present invention, the method for producing the porous support-zeolite membrane composite is not particularly limited. For example, after the zeolite is formed on the inorganic porous support by hydrothermal synthesis, the solution is contained in a solution containing the Si compound. A method of treatment such as immersion is preferred.
Specifically, for example, a zeolite membrane composite is prepared by mixing a reaction mixture for hydrothermal synthesis (hereinafter sometimes referred to as an “aqueous reaction mixture”) having a uniform composition and a porous support. It can be prepared by placing in a heat-resistant pressure-resistant container such as an autoclave, which is gently fixed inside, and sealing and heating 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.

  Specific examples include cations derived from alicyclic amines such as cations derived from 1-adamantanamine, cations derived from 3-quinacridinal, and cations derived from 3-exo-aminonorbornene. It is done. Among these, a cation derived from 1-adamantanamine is more preferable. When a cation derived from 1-adamantanamine is used as an organic template, CHA-type zeolite capable of forming a dense film is crystallized. By forming a dense membrane, a CHA-type zeolite with high separation performance can be obtained.

  Of the cations derived from 1-adamantanamine, the N, N, N-trialkyl-1-adamantanammonium cation is more preferred. The three alkyl groups of the N, N, N-trialkyl-1-adamantanammonium cation are usually independent alkyl groups, preferably a lower alkyl group, more preferably a methyl group. The most preferred compound among them is the N, N, N-trimethyl-1-adamantanammonium cation.

Such cations are accompanied by anions that do not harm the formation of CHA-type zeolite. Representative examples of such anions include halogen ions such as Cl ⁻ , Br ⁻ and I ⁻ , hydroxide ions, acetates, sulfates, and carboxylates. Of these, hydroxide ions are particularly preferably used.
As another organic template, N, N, N-trialkylbenzylammonium cation can also be used. Also in this case, the alkyl group is an independent alkyl group, preferably a lower alkyl group, more preferably a methyl group. Among them, the most preferred compound is N, N, N-trimethylbenzylammonium cation. The anion accompanied by this cation is the same as described above.

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 usually 5 or more, preferably 8 or more, more preferably 10 or more, and further 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. Furthermore, since moderately Al atoms are present in the produced zeolite, the separation performance is improved with a gas 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.
As described above, the addition of K to the aqueous reaction mixture is performed by changing the space group in the rhombohedral setting.

(No. 166), the peak intensity in the vicinity of 2θ = 9.6 °, which is a peak derived from the (1, 0, 0) index surface in the CHA structure, and the (2, 0, −1) surface The peak intensity ratio in the vicinity of 2θ = 20.8 ° (peak intensity ratio B), which is a peak derived from the above, or the peak derived from the plane of (1,1,1), in the vicinity of 2θ = 17.9 ° There is a tendency to increase the ratio between the peak intensity and the peak intensity in the vicinity of 2θ = 20.8 ° (peak intensity ratio A), which is a peak derived from the (2, 0, −1) plane.

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.

In general, the amount of water in the synthesis of powdered CHA-type zeolite is about 15 to 50 in terms of H ₂ O / SiO ₂ molar ratio. Zeolite membrane composite with high separation performance in which CHA-type zeolite is crystallized into a dense membrane on the support by using a high H ₂ O / SiO ₂ molar ratio (50 to 1000), that is, water-rich conditions. You can get a body.
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.
When forming a CHA type zeolite membrane, it is preferable to use seed crystals of CHA type zeolite.

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 method in which a slurry mixed with a solvent such as water is coated on a support can be used. 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 the amount of the seed crystal is less than the lower limit, it becomes difficult to form a crystal, and there is a tendency that the film growth becomes insufficient or the film growth becomes uneven. In addition, when the amount of the seed crystal exceeds the upper limit, surface irregularities are increased by the seed crystal, or spontaneous nuclei are likely to grow due to the seed crystal falling from the support, thereby inhibiting film growth on the support. Sometimes. In either case, it tends to be difficult to form a dense zeolite membrane.

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. The bundle may be reduced. 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. Examples of 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 transitions such as Fe, Cu and Zn. Examples include metal ions. Among these, alkali metal ions such as proton, Na ⁺ , K ⁺ , and Li ⁺ are preferable.

For ion exchange, the zeolite membrane after calcination (such as when using a template) is replaced with NH ₄
An aqueous solution containing an ammonium salt such as NO ₃ or NaNO ₃ or an ion to be exchanged, or an acid such as hydrochloric acid in some cases, is usually treated at a temperature of room temperature to 100 ° C. and then washed with water. Furthermore, you may bake at 200 to 500 degreeC as needed.
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, it is 300 L / (m ² · h) or less, most preferably 200 L / (m ² · h) or less. 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.
Subsequently, the zeolite membrane composite is subjected to a treatment such as immersion with a liquid containing a Si compound, which is a compound containing one or more Si atoms. Thereby, the zeolite membrane surface can be modified with the Si compound to have the specific physicochemical properties described above. For example, by forming a Si layer on the zeolite membrane surface, it is considered that the opening diameter is smaller than the pore diameter inherent in zeolite, and the separation performance can be improved. In addition, by modifying the zeolite membrane surface with a Si compound, an effect of closing fine defects existing on the membrane surface may be obtained as a secondary effect.

  The liquid used for the surface treatment is not particularly limited as long as the zeolite membrane composite can be treated under the surface treatment conditions, and may be a solution obtained by adding a solvent to the Si compound. It may be a liquid, not a sol or a gel. 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. Furthermore, 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 contained.

  Examples of the Si compound include methyltriethoxysilane, 3-aminopropyltriethoxysilane, alkylalkoxysilanes such as 1,1,3,3-tetramethoxy-1,3-dimethylpropanedisiloxane, hexamethyldisiloxane, and the like. Siloxane-containing organosilicon compounds such as hexamethyldisilazane, silicates such as tetramethoxysilane and tetraethoxysilane, silicate oligomers such as methylsilicate oligomer and ethylsilicate oligomer, amorphous silica, fume Dosilica, colloidal silica, silica gel, sodium silicate, silica sol and the like can be used.

Among these, silicates or silicate oligomers are preferable in terms of reactivity, and tetraethoxysilane and methyl silicate oligomers are particularly preferable.
These Si compounds may be used individually by 1 type, and may be used in combination of 2 or more type.
As a treatment method, it may be immersed in a liquid and may form a chemical bond with the Si compound in the immersed liquid, or after the immersion, the zeolite membrane is taken out of the liquid and the Si compound is attached to the surface. The chemical bond may be formed by the above, or the chemical bond may be formed both during and after the immersion.

First, the case where water is used as a solvent will be described.
When water is used as a solvent, the temperature of the solution is usually 20 ° C. or higher, preferably 60 ° C. or higher.
More preferably, it is 80 degreeC or more, Usually, 200 degrees C or less, Preferably it is 150 degrees C or less, More preferably, it is 130 degrees C or less. 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 immersion time is usually 1 hour or longer, preferably 4 hours or longer, more preferably 8 hours or longer, and is usually 100 hours or shorter, preferably 50 hours or shorter, more preferably 24 hours or shorter. If the immersion time is too short, the change of the film surface does not proceed sufficiently and a sufficient effect may not be obtained. If the soaking time is too long, the zeolite may partially dissolve in water and break the zeolite.

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.
The content of the Si compound in the solution 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 molar concentration of the Si compound. 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.

It is preferable that an acid or a base is present in the 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 in water, a trace amount of OH ⁻¹ ions may be actively present. In that case, the OH ⁻¹ ion concentration in the aqueous solution is usually 0. 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 water 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 water 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 aqueous solution 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 aqueous solution is preferably 0.01 mol / l or more, more preferably 0.05 mol / l or more, further 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.
Next, the immersion treatment using an organic solvent will be described.
In this case, the temperature of the solution is usually 20 ° C. or higher, preferably 60 ° C. or higher, more preferably 80 ° C. or higher, and is usually 200 ° C. or lower, preferably 150 ° C. or lower, more preferably 110 ° 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 membrane surface and the Si compound is insufficient, and the modification with the Si compound is not performed sufficiently, and the separation performance may not be sufficiently improved. . If the temperature is too high, the zeolite membrane may be broken.

  The immersion time is usually 0.5 hours or longer, preferably 1 hour or longer, more preferably 3 hours or longer, and usually 50 hours or shorter, preferably 24 hours or shorter, more preferably 10 hours or shorter. If the immersion time is too short, the change of the film surface does not proceed sufficiently and a sufficient effect may not be obtained. If the soaking time is too long, the zeolite may partially dissolve in water and break the zeolite.

The pressure during the surface treatment is not particularly limited, and atmospheric pressure can be performed under reflux conditions as necessary. Or you may process under the self-generated pressure which arises when the processing solution put into the airtight container was heated to the said temperature range as needed. Further, if necessary, an inert gas such as nitrogen may be added.
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.

Further, when an organic solvent is used, water may be added into the system. The concentration of water that can 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, More preferably, it is 2 mass% or less.
The content of the Si compound in the solution 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, as the Si element concentration. Preferably it is 5 mass% or less, More preferably, it is 2 mass% or less. The content of the Al compound 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 as Al element concentration. Is 5% by mass or less, more preferably 1% by mass or less.

  In the surface treatment, the surface treatment can be performed by immersing in a liquid containing at least an Si compound and then heating. In this case, it can also process without adding a solvent. 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.

  When the surface treatment is performed without adding a solvent, the immersion temperature is usually 1 ° C. or higher, preferably 5 ° C. or higher, more preferably 10 ° C. or higher, particularly preferably 15 ° C. or higher, and usually 200 ° C. or lower, preferably 150 ° C. ° C or lower, more preferably 130 ° C or lower, particularly preferably 100 ° C or lower, most preferably 80 ° C or lower. If the temperature is too low, the fluidity of the Si compound becomes low, and the Si compound does not uniformly adhere to the surface of the zeolite membrane composite, and the modification may become partial. If the temperature is too high, the reaction between the Si compounds proceeds quickly, and the adhesion to the surface of the zeolite membrane composite and the reaction may not proceed sufficiently.

The immersion time is usually 0.5 seconds or more, preferably 1 second or more, more preferably 2 seconds or more, particularly preferably 3 seconds or more, and usually 10 hours or less, preferably 7 hours or less, more preferably 5 hours or less. More preferably, it is 3 hours or less, particularly preferably 1 hour or less.
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.

  When heat treatment is performed after immersion in a liquid containing Si compound, when the zeolite membrane composite is immersed in a liquid containing Si compound, in the case of a tubular zeolite membrane composite, only the bottom or top and bottom of the silicone rubber plug It is desirable to prevent a large amount of Si compound from penetrating into the support by covering with a Teflon (registered trademark) tape or the like. 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 immersion 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 200 ° C. or lower, particularly preferably 150 ° C. It is below ℃. 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, 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 30 hours or shorter, preferably 25 hours or shorter. More preferably, it is 20 hours or less, More preferably, it is 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, it is preferable to coexist water 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.
The heating after the immersion can be performed with a normal dryer or the like, or the film after the immersion can be put in a sealed container and heated. When the immersed film is placed in a sealed container, a small amount of water may be allowed to coexist so as not to contact the film.
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.

<Separation or concentration method>
In the separation or concentration method of the present invention, a mixed gas containing a plurality of gas components is brought into contact with the separation membrane described in detail above, and a highly permeable component of the mixed gas is allowed to permeate from the mixed gas. The highly permeable component is concentrated by separating the highly permeable component or by allowing the highly permeable component to permeate from the mixed gas.

In the separation or concentration method of the present invention, a mixed gas containing a plurality of gas components 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. By selectively setting the opposite side to a pressure lower than the side in contact with the mixed gas, the component having high permeability to the zeolite membrane (substance in the mixture having relatively high permeability) is selectively selected from the mixed gas. That is, it is permeated as the main component of the permeable substance. Thereby, a highly permeable substance can be separated from the mixed gas. As a result, the specific component can be separated and recovered or concentrated by increasing the concentration of the specific component (the substance in the mixed gas having relatively low permeability) in the mixed gas.

The mixed gas to be separated or concentrated is not particularly limited as long as it is a mixed gas that can be separated or concentrated by the porous support-zeolite membrane composite in the present invention.
In the method of the present invention, examples of the mixed gas to be separated or concentrated include carbon dioxide, oxygen, nitrogen, methane, ethane, ethylene, propane, propylene, normal butane, isobutane, 1-butene, 2-butene, Examples include those containing at least one component selected from 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.

<Measurement of physical properties and separation performance>
In the following experimental examples, physical properties and separation performance were measured as follows unless otherwise specified.
(1) X-ray diffraction (XRD) measurement XRD measurement of the zeolite membrane was performed under the following conditions.
-Device name: X'PertPro MPD manufactured by PANalytical, the Netherlands
Optical system specifications Incident side: Enclosed X-ray tube (CuKα)
Soller Slit (0.04 rad)
Divergence Slit (Variable Slit)
Sample stage: XYZ stage
Light receiving side: Semiconductor array detector (X 'Celerator)
Ni-filter
Soller Slit (0.04 rad)
Goniometer radius: 240mm
Measurement conditions X-ray output (CuKα): 45 kV, 40 mA
Scanning axis: θ / 2θ
Scanning range (2θ): 5.0-70.0 °
Measurement mode: Continuous
Reading width: 0.05 °
Counting time: 99.7 sec
Automatic variable slit (Automatic-DS): 1 mm (irradiation width)
Lateral divergence mask: 10 mm (irradiation width)

X-rays were irradiated in a direction perpendicular to the axial direction of the cylindrical tube. Also, X-rays are not the sample table surface, but the sample table surface, out of two lines where the cylindrical tubular membrane complex placed on the sample table and the surface parallel to the sample table surface are in contact with each other so that noise and the like do not enter as much as possible. It was made to hit mainly on the other line above the surface.
In addition, the irradiation width was fixed to 1 mm by an automatic variable slit and measured, and Materials Data, Inc. XRD analysis software JADE 7.5.2 (Japanese version) was used to perform variable slit → fixed slit conversion to obtain an XRD pattern.

(2) SEM-EDX measurement SEM-EDX measurement of the zeolite membrane was performed under the following conditions.
-Device name: SEM: FE-SEM Hitachi: S-4800
EDX: EDAX Genesis
・ Acceleration voltage: 10 kV
The entire field of view (25 μm × 18 μm) at a magnification of 5000 was scanned, and X-ray quantitative analysis was performed.
By this SEM-EDX measurement, the SiO2 / Al2O3 molar ratio of the produced zeolite membrane itself was determined. In the SEM-EDX measurement, information on only the zeolite membrane of several microns can be obtained by setting the X-ray irradiation energy to about 10 kV.

(3) XPS measurement XPS (X-ray photoelectron spectroscopy) measurement of the zeolite membrane surface was performed under the following conditions.
・ Device name: Quantum2000 manufactured by PHI
-X-ray source: Monochromatic Al-Kα, output 16 kV-34 W (X-ray generation area 170 μmφ)
・ Charge neutralization: Combined use of electron gun (5μA) and ion gun (2V) ・ Spectroscopic system: Pulse energy 187.85 eV @ Wide spectrum
117.40 eV @ narrow spectrum (Al2p)
29.35 eV @ narrow spectrum (C1s, O1s, Si
2p)
Measurement area: Spot irradiation (irradiation area <340 μmφ)
・ Extraction angle: 45 ° (from the surface)
By this XPS measurement, the SiO ₂ / Al ₂ O ₃ molar ratio on the surface of the produced zeolite membrane was determined.

(4) Air permeation amount At atmospheric pressure, one end of the zeolite membrane composite is sealed, and the other end is connected to a 5 kPa vacuum line while maintaining airtightness. The flow rate of the air that permeated the zeolite membrane composite was measured with a mass flow meter installed in between, and the air permeation amount [L / (m ² · h)] was obtained. As the mass flow meter, 8300 manufactured by KOFLOC, for N ₂ gas, and a maximum flow rate of 500 ml / min (20 ° C., converted to 1 atm) were used. When the mass flow meter display on KOFLOC 8300 is 10 ml / min (20 ° C, converted to 1 atm) or less, Lintec MM-2100M, for Air gas, maximum flow rate 20 ml / min (converted to 0 ° C, 1 atm) It measured using.

(5) Single component gas permeation evaluation The single component gas permeation test was performed as follows using the apparatus schematically shown in FIG. The sample gases used were carbon dioxide (purity 99.9%, manufactured by High Pressure Gas Industries), methane (purity 99.999%, manufactured by Japan Fine Products), nitrogen (purity 99.99%, manufactured by Toho Oxygen Industries), Helium (purity 99.99, manufactured by Japan Helium Center).

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. Further, a pipe (sweep gas introduction 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 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.

In the apparatus of FIG. 1, when performing a single component gas permeation test, a sample gas (supply gas 7) is supplied between the pressure-resistant container 2 and the zeolite membrane complex 1 at a constant flow rate, and is supplied by a back pressure valve 6. The pressure of is constant. The flow rate of the exhaust gas 10 discharged from the pipe 11 is measured.
More specifically, in order to remove components such as moisture and air, the sample temperature and the supply gas of the zeolite membrane composite 1 are supplied after drying at a temperature higher than the measurement temperature and purging with a supply gas to be exhausted or used. The flow rate of the sample gas (permeate gas 8) permeated through the zeolite membrane composite 1 was measured after the permeate gas flow rate was stabilized with the differential pressure between the 7 side and the permeate gas 8 side constant, and the gas permeance [mol · (M ² · s · Pa) ⁻¹ ] is calculated. As the pressure for calculating the permeance, a pressure difference (differential pressure) between the supply side and the permeation side of the supply gas is used.

Based on the measurement result, the ideal separation coefficient α is calculated by the following equation (1).
α = (Q ₁ / Q ₂ ) / (P ₁ / P ₂ ) (1)
Wherein (1), _{Q 1} and _{Q 2,} respectively, the amount of transmission of high permeability gas and low permeability gas indicates ^{[mol · (m 2 · s} ) -1], P 1 and _{P 2} Respectively show the pressure [Pa] of the highly permeable gas and the low permeable gas that are the supply gas. ]

(6) Mixed gas permeation test The mixed gas permeation test of the zeolite membrane composite was performed as follows using the apparatus schematically shown in FIG. The sample gas used is compressed air.
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 high-temperature bath 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 are connected via the connection 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. Further, a pressure gauge 5 for measuring the pressure on the supply side of the sample gas and a back pressure valve 6 for adjusting the pressure on the supply side are connected to the pressure vessel 2. Each connection part is connected with good airtightness.

  In the apparatus of FIG. 1, the sample gas (supply gas 7) is supplied between the pressure-resistant container 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. On the other hand, the sweep gas 9 is caused to flow from the pipe 12 to the inside of the zeolite membrane complex 1, and the flow rate of the exhaust gas discharged from the pipe 11 (the exhaust gas of the sweep gas 9 and the accompanying permeated gas 8) is measured. The exhaust gas is collected and component analysis is performed by gas chromatography.

At this time, the flow velocity of each component gas that has passed through the zeolite membrane composite 1 is measured as described above, and the gas permeation [mol · (m ² · s) ⁻¹ ] is calculated.
Based on the measurement result, the separation coefficient α ′ is calculated by the following formula (2).
α ′ = (Q ′ ₁ / Q ′ ₂ ) / (P ′ ₁ / P ′ ₂ ) (2)
Wherein (2), Q _'1 and Q' _2, respectively, represents the permeability of the high permeability gas and low permeability gas ^{[mol · (m 2 · s} ) -1], P '1 And P ′ ₂ indicate the partial pressure [Pa] of the highly permeable gas and the low permeable gas in the supply gas, respectively. ]

(Comparative Example 1)
A membrane complex of an inorganic porous support and a CHA-type zeolite membrane was prepared as follows by directly hydrothermally synthesizing CHA-type zeolite on the inorganic porous support.
The following was prepared as a reaction mixture for hydrothermal synthesis.
Aluminum hydroxide (containing 53.5% by mass of Al ₂ O ₃ , manufactured by Aldrich) mixed with 0.29 g of lithium hydroxide monohydrate, 13.9 g of 1 mol / L-KOH aqueous solution, and 104.0 g of water 1 .32 g was added and stirred to dissolve to obtain a transparent solution. As an organic template, 2.35 g of an aqueous solution of N, N, N-trimethyl-1-adamantanammonium hydroxide (hereinafter referred to as “TMADAOH”) (containing 25% by mass of TMADAOH, manufactured by Seychem) was added, and colloidal. 10.4 g of silica (Snowtech-40 manufactured by Nissan Chemical Co., Ltd.) was added and stirred for 2 hours to obtain a reaction mixture.

The composition (molar ratio) of this reaction mixture was SiO ₂ / Al ₂ O ₃ / LiOH / KOH / H ₂ O / TMADAOH = 1 / 0.1 / 0.1 / 0.2 / 100 / 0.04, SiO ₂ / Al ₂
O ₃ = 10.
As the inorganic porous support, an alumina tube (outer diameter 12 mm, inner diameter 9 mm) was cut to a length of 80 mm, washed with an ultrasonic cleaner and dried.

As a seed crystal, the gel composition (molar ratio) of SiO ₂ / Al ₂ O ₃ / NaOH / KOH / H ₂ O / TMADAOH = 1 / 0.033 / 0.1 / 0.06 / 40 / 0.07 is 160. A CHA-type zeolite crystallized by hydrothermal synthesis at 2 ° C. for 2 days was used. The support was immersed in a dispersion obtained by dispersing the seed crystal in 1% by mass of water for a predetermined time, and then dried at 100 ° C. for 5 hours to adhere the seed crystal. The mass of the attached seed crystal was 1.2 g / m ² .

  A total of three of the support to which the seed crystal was attached in this way and two supports to which the seed crystal was similarly attached was perpendicular to the Teflon (registered trademark) inner cylinder (200 ml) containing the reaction mixture. The autoclave was sealed by dipping in the direction, and was heated in a stationary state at 160 ° C. for 48 hours under an autogenous pressure. After the elapse of a predetermined time, the support-zeolite membrane complex was taken out of the reaction mixture after being allowed to cool, and dried at 100 ° C. for 2 hours or more after washing.

The zeolite membrane composite before template firing was fired in an electric furnace at 500 ° C. for 5 hours. The mass of the CHA-type zeolite crystallized on the support, which was determined from the difference between the mass of the membrane composite after firing and the mass of the support, was 145 g / m ² .
The air permeation amount of the zeolite membrane composite after calcination was 177 L / (m ² · h).
When XRD of the produced membrane was measured, it was found that CHA-type zeolite was produced.

With respect to this zeolite membrane composite, the SiO ₂ / Al ₂ O ₃ molar ratio on the zeolite membrane surface measured by XPS was 11.4.
Using the obtained inorganic porous support-CHA type zeolite membrane composite, single component gas permeation evaluation was performed at 50 ° C. using the apparatus shown in FIG. As pretreatment, the zeolite membrane composite is introduced at 140 ° C. and carbon dioxide as the supply gas 7 is introduced between the cylinders of the pressure vessel 2 and the zeolite membrane composite 1 until the permeation amount of carbon dioxide is stabilized. Dried. The gases evaluated are carbon dioxide, methane, nitrogen and helium.

Table 1 shows the CO ₂ / N ₂ , He / CH ₄ permeance ratio, and He permeance thus obtained. The CO ₂ / N ₂ permeance ratio was 12, and the He / CH 4 permeance ratio was 13, indicating that the separation performance was insufficient.
Using the obtained inorganic porous support-CHA type zeolite membrane composite, air separation was evaluated at 50 ° C. using the apparatus shown in FIG. Air was supplied from the pipe 7, the back pressure valve 6 was adjusted so that the back pressure was 0.1 MPa, and air separation was performed.
The obtained separation results are shown in Table 1. The oxygen concentration after the separation was 28%, and although the oxygen concentration was higher than that before the separation, the concentration was not sufficient.

(Comparative Example 2)
An inorganic porous support-CHA type zeolite membrane composite was prepared in the same manner as in Comparative Example 1 except that the heating time was 24 hours. The mass of the attached seed crystal is 1.0 g / m ² , and the mass of the CHA-type zeolite crystallized on the support obtained from the difference between the mass of the membrane composite after firing and the mass of the support is 126 g / m ^2. It was m ^2.

The air permeation amount of the zeolite membrane composite after calcination was 155 L / (m ² · h).
With respect to this zeolite membrane composite, the SiO ₂ / Al ₂ O ₃ molar ratio on the zeolite membrane surface measured by XPS was 19.0.
Using the obtained inorganic porous support-CHA type zeolite membrane composite, 5 as in Comparative Example 1
Single component gas permeation evaluation was performed at 0 ° C. Table 1 shows the CO ₂ / N ₂ , He / CH ₄ permeance ratio, and He permeance thus obtained. The CO ₂ / N ₂ permeance ratio was 15 and the He / CH ₄ permeance ratio was 16, which was insufficient as separation performance.

  Using the obtained inorganic porous support-CHA type zeolite membrane composite, air separation was evaluated at 50 ° C. using the apparatus shown in FIG. The obtained separation results are shown in Table 1. The oxygen concentration after the separation was 27%, and although the oxygen concentration was higher than that before the separation, the concentration was not sufficient.

(Comparative Example 3)
An inorganic porous support-CHA type zeolite membrane composite was prepared in the same manner as in Comparative Example 1 except that a mullite tube was used as the inorganic porous support. The mass of the attached seed crystal is 0.7 g / m ² , and the mass of the CHA-type zeolite crystallized on the support determined from the difference between the mass of the membrane composite after firing and the mass of the support is 140 g / m ^2. It was m ^2.

  The zeolite membrane composite thus obtained was surface treated as follows. Tetraethoxysilane was plugged with a plug having an air hole on the upper end face and a plug having no hole on the lower end face, soaked at room temperature for about 5 seconds and pulled up. Then air-dried, and a Teflon (registered trademark) inner cylinder filled with about 1 g of water at the bottom, standing vertically using a jig, sealing the autoclave, heating at 100 ° C. for 6 hours, and after a predetermined time, After allowing to cool, the zeolite membrane composite was taken out and further heat-treated at 150 ° C. for 1 h.

For this zeolite membrane composite, the SiO ₂ / Al ₂ O ₃ molar ratio on the zeolite membrane surface measured by XPS was 23.0, and treatment with tetraethoxysilane increased the proportion of Si on the surface, increasing the value. It is thought that.
Single component gas permeation evaluation was performed at 50 ° C. in the same manner as in Comparative Example 2 using the obtained inorganic porous support-CHA type zeolite membrane composite. The obtained CO ₂ / N ₂ , He / CH ₄ permeance ratio, and He permeance are shown in Table 1. The CO ₂ / N ₂ permeance ratio was 17 and the He / CH ₄ permeance ratio was 17, which was insufficient although the separation performance tended to improve.

  Using the obtained inorganic porous support-CHA type zeolite membrane composite, air separation was evaluated at 50 ° C. using the apparatus shown in FIG. The obtained separation results are shown in Table 1. The oxygen concentration after the separation was 27%, and although the oxygen concentration was higher than that before the separation, the concentration was not sufficient.

Example 1
The following was prepared as a reaction mixture for hydrothermal synthesis.
A mixture of 10.8 g of 1 mol / L-NaOH aqueous solution, 7.2 g of 1 mol / L-KOH aqueous solution and 103.3 g of water was mixed with aluminum hydroxide (containing 53.5 mass% of Al ₂ O ₃ , manufactured by Aldrich). 91 g was added, stirred and dissolved to obtain a transparent solution. To this, 2.43 g of TMADAOH aqueous solution (containing 25% by mass of TMADAOH, manufactured by Seychem Co.) is added as an organic template, and 10.8 g of colloidal silica (Snowtech-40 manufactured by Nissan Chemical Co., Ltd.) is added and stirred for 2 hours. A mixture was obtained.

The composition (molar ratio) of this reaction mixture was SiO ₂ / Al ₂ O ₃ / NaOH / KOH / H ₂ O / TMADAOH = 1 / 0.067 / 0.15 / 0.1 / 100 / 0.04, SiO 2 ₂ / Al ₂ O ₃ = 15.
The same alumina tube as in Comparative Example 1 was used as the inorganic porous support.
As seed crystals, SiO ₂ / Al ₂ O ₃ / NaOH / KOH / H ₂ O / TMADAOH
= CHA-type zeolite crystallized by hydrothermal synthesis at 160 ° C. for 2 days with a gel composition (molar ratio) of 1 / 0.033 / 0.1 / 0.06 / 20 / 0.07. The support was immersed in a dispersion in which this seed crystal was dispersed in 0.3% by mass of water for a predetermined time, and then dried at 100 ° C. for 5 hours to adhere the seed crystal. The mass of the attached seed crystal was 0.6 g / m ² .

Thus, the support body to which the seed crystal was adhered was heated, washed and dried in the same manner as in Comparative Example 2. The mass of the CHA-type zeolite crystallized on the support, determined from the difference between the mass of the membrane composite after firing and the mass of the support, was 125 g / m ² . The air permeation amount of the zeolite membrane composite after calcination was 17 L / (m ² · h).

  The zeolite membrane composite thus obtained was surface treated as follows. A solution in which methyl silicate oligomer (MKC (registered trademark) silicate, MS-51, manufactured by Mitsubishi Chemical Corporation) is mixed at 30% by mass with isopropyl alcohol is capped with an air hole on the upper end surface, and the lower end surface The zeolite membrane composite with plugs without holes was soaked at room temperature for about 5 seconds and pulled up. Then air-dried, and a Teflon (registered trademark) inner cylinder filled with about 1 g of water at the bottom, standing vertically using a jig, sealing the autoclave, heating at 100 ° C. for 6 hours, and after a predetermined time, After allowing to cool, the zeolite membrane composite was taken out and further heat-treated at 150 ° C. for 1 h.

With respect to this zeolite membrane composite, the SiO ₂ / Al ₂ O ₃ molar ratio on the zeolite membrane surface measured by XPS was 69.0.
Using the obtained inorganic porous support-CHA type zeolite membrane composite, single component gas permeation evaluation was performed at 50 ° C. in the same manner as in Comparative Example 1. The obtained CO ₂ / N ₂ , He / CH ₄ permeance ratio, and He permeance are shown in Table 1. The CO ₂ / N ₂ permeance ratio was 17 and the He / CH ₄ permeance ratio was 17, which was insufficient although the separation performance tended to improve.

  Using the obtained inorganic porous support-CHA type zeolite membrane composite, air separation was evaluated at 50 ° C. using the apparatus shown in FIG. The obtained separation results are shown in Table 1. The oxygen concentration after separation was 40%, and it was found that a higher concentration of oxygen was obtained than in Comparative Examples 1, 2, and 3.

(Example 2)
In the same manner as in Comparative Example 3, an inorganic porous support-CHA type zeolite membrane composite was prepared. The mass of the attached seed crystal was 1.9 g / m ² , and the mass of the CHA-type zeolite crystallized on the support, which was obtained from the difference between the mass of the membrane composite after firing and the mass of the support, was 146 g / m ^2. It was m ^2. The membrane composite thus obtained was subjected to a surface treatment in the same manner as in Example 1.

This zeolite membrane composite, _SiO 2 / _Al 2 _{O 3} molar ratio of the zeolite membrane itself was measured by SEM-EDX is 33.6, _SiO 2 / _Al 2 _{O 3} molar ratio of the zeolite membrane surface as measured by XPS 200 It can be seen that the ratio of Si on the surface is high.
Using the obtained inorganic porous support-CHA type zeolite membrane composite, single component gas permeation evaluation was performed at 50 ° C. in the same manner as in Comparative Example 1. The obtained CO ₂ / N ₂ , He / CH ₄ permeance ratio, and He permeance are shown in Table 1. The CO ₂ / N ₂ permeance ratio was 35 and the He / CH ₄ permeance ratio was 145, indicating that the membrane had high separation performance.

Using the obtained inorganic porous support-CHA type zeolite membrane composite, air separation was evaluated at 50 ° C. using the apparatus shown in FIG. The obtained separation results are shown in Table 1. The oxygen concentration after separation was 44%, and it was found that a higher concentration of oxygen was obtained than in Comparative Examples 1, 2, and 3.

(Example 3)
An inorganic porous support-CHA type zeolite membrane composite was prepared in the same manner as in Comparative Example 1 except that the concentration of the seed crystal dispersion was 0.3% by mass. The mass of the attached seed crystal is 0.5 g / m ² , and the mass of the CHA-type zeolite crystallized on the support obtained from the difference between the mass of the membrane composite after firing and the mass of the support is 146 g / m ^2. It was m ^2.

The XRD pattern of the produced zeolite membrane is shown in FIG. “*” In the figure is a peak derived from the support. From XRD measurement, it was found that CHA-type zeolite was produced. Further, (the intensity of the peak near 2θ = 9.6 °) / (the intensity of the peak near 2θ = 20.8 °) = 2.
4. (Intensity of peak near 2θ = 17.9 °) / (Intensity of peak near 2θ = 20.8 °) = 5.9.

FIG. 3 shows an XRD pattern of powdered CHA-type zeolite (zeolite generally referred to as SSZ-13 in US Pat. No. 4,544,538, hereinafter referred to as “SSZ-13”). (Intensity of peak near 2θ = 9.6 °) / (Intensity of peak near 2θ = 20.8 °) = 0.91, (Intensity of peak near 2θ = 17.9 °) / (2θ = 20 .
The intensity of the peak in the vicinity of 8 °) = 0.32.

Compared with the powdered CHA-type zeolite, the zeolite membrane obtained in Example 3 was (peak intensity around 2θ = 9.6 °) / (peak intensity around 2θ = 20.8 °), (2θ = 17.
The intensity of the peak near 9 ° / (the intensity of the peak near 2θ = 20.8 °) is high, and the orientation to the (1, 0, 0) plane and (1, 1, 1) plane in the rhombohedral setting is estimated. The membrane composite thus obtained was subjected to a surface treatment in the same manner as in Example 1 except that the concentration of methyl silicate oligomer was changed to 10% by mass.

This zeolite membrane composite was found to have a high SiO ₂ / Al ₂ O ₃ molar ratio of 190 on the surface of the zeolite membrane measured by XPS and a high proportion of Si on the surface.
Using the obtained inorganic porous support-CHA type zeolite membrane composite, single component gas permeation evaluation was performed at 50 ° C. in the same manner as in Comparative Example 1. The obtained CO ₂ / N ₂ , He / CH ₄ permeance ratio, and He permeance are shown in Table 1. The CO ₂ / N ₂ permeance ratio was 26, and the He / CH ₄ permeance ratio was 26, indicating that the membrane had high separation performance.

  Using the obtained inorganic porous support-CHA type zeolite membrane composite, air separation was evaluated at 50 ° C. using the apparatus shown in FIG. The obtained separation results are shown in Table 1. The oxygen concentration after separation was 33%, and it was found that a higher concentration of oxygen was obtained than in Comparative Examples 1, 2, and 3.

Example 4
An inorganic porous support-CHA type zeolite membrane composite was prepared in the same manner as in Example 3 except that the autoclave was sealed and the conditions for heating under autogenous pressure were 180 ° C. and 18 h. The mass of the attached seed crystal is 0.5 g / m ² , and the mass of the CHA-type zeolite crystallized on the support obtained from the difference between the mass of the membrane composite after firing and the mass of the support is 123 g / m ^2. It was m ^2.
Surface treatment was carried out in the same manner as in Example 1 except that the concentration of methyl silicate oligomer was 25% by mass and the liquid temperature was 40 ° C.

With respect to this zeolite membrane composite, the SiO ₂ / Al ₂ O ₃ molar ratio on the zeolite membrane surface measured by XPS was 168, and it was found that the ratio of Si on the surface was high.
Using the obtained inorganic porous support-CHA type zeolite membrane composite, 5 as in Comparative Example 1
Single component gas permeation evaluation was performed at 0 ° C. The obtained CO ₂ / N ₂ , He / CH ₄ permeance ratio, and He permeance are shown in Table 1. The CO ₂ / N ₂ permeance ratio was 42 and the He / CH ₄ permeance ratio was 180, indicating that the membrane had high separation performance.

  Using the obtained inorganic porous support-CHA type zeolite membrane composite, air separation was evaluated at 50 ° C. using the apparatus shown in FIG. The obtained separation results are shown in Table 1. The oxygen concentration after the separation was 43%, and it was found that a higher concentration of oxygen was obtained than in Comparative Examples 1, 2, and 3.

(Example 5)
The following was prepared as a reaction mixture for hydrothermal synthesis.
Aluminum hydroxide to a mixture of lithium monohydrate 0.23g and 1 mol / L-KOH aqueous solution 11.0g water 110g hydroxide _{(Al 2} O 3 53.5 mass% containing, Aldrich) 0.89 g Was added and stirred to dissolve to obtain a transparent solution. As an organic template, 2.38 g of TMADAOH aqueous solution (containing 25% by mass of TMADAOH, manufactured by Sechem Co.) is added, and 7.05 g of colloidal silica (Snowtech-40 manufactured by Nissan Chemical Co., Ltd.) is added and stirred for 2 hours. A mixture was obtained.

The composition (molar ratio) of this reaction mixture was SiO ₂ / Al ₂ O ₃ / LiOH / KOH / H ₂ O / TMADAOH = 1 / 0.1 / 0.12 / 0.23 / 150 / 0.06, SiO ₂ / Al ₂ O ₃ = 10.
Thereafter, an inorganic porous support-CHA type zeolite membrane composite was prepared in the same manner as in Example 1 except that the heating time was 18 hours. The mass of the attached seed crystal is 0.3 g / m ² , and the mass of the CHA-type zeolite crystallized on the support obtained from the difference between the mass of the membrane composite after firing and the mass of the support is 96 g / m ^2. It was m ^2.

Surface treatment was carried out in the same manner as in Example 1 except that the concentration of the methyl silicate oligomer was 5% by mass and the diluent was acetone.
This zeolite membrane composite, _SiO 2 / _Al 2 _{O 3} molar ratio of _SiO 2 / _Al 2 _{O 3} molar ratio of the zeolite membrane itself was measured by SEM-EDX 17.6, zeolite membrane surface as measured by XPS is 76 2 and the surface Si ratio is high.

Using the obtained inorganic porous support-CHA type zeolite membrane composite, single component gas permeation evaluation was performed at 50 ° C. in the same manner as in Comparative Example 1. The obtained CO ₂ / N ₂ , He / CH ₄ permeance ratio, and He permeance are shown in Table 1. The CO ₂ / N ₂ permeance ratio was 23, and the He / CH ₄ permeance ratio was 88, indicating that the membrane had high separation performance.

Using the obtained inorganic porous support-CHA type zeolite membrane composite, air separation was evaluated at 50 ° C. using the apparatus shown in FIG. The obtained separation results are shown in Table 1. The oxygen concentration after separation was 34%, and it was found that a higher concentration of oxygen was obtained than in Comparative Examples 1, 2, and 3.
The results of Comparative Examples 1 to 3 and Examples 1 to 5 are shown in Table 1.

The present invention can be used in any industrial field, for example, air, natural gas, combustion gas, coke oven gas, biogas such as land file gas generated from a landfill, generated in the petrochemical industry, It can be used for separation or concentration of the steam reformed gas of methane discharged. Also, for example, it can be suitably used in fields where oxygen-rich gas with a high oxygen concentration is required, such as chemical plants, garbage disposal plants, and automobiles.

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. Plumbing

Claims (10)

The mixed gas containing a plurality of gas components is brought into contact with the separation membrane, and the highly permeable component of the mixed gas is permeated to separate the highly permeable component from the mixed gas, or the A gas separation or concentration method for condensing a low-permeability component by permeating a high-permeability component from a mixed gas,
The separation membrane is a zeolite membrane formed on an inorganic porous support, and the zeolite membrane contains a zeolite having a pore structure of an oxygen 8-membered ring or less,
A method for separating or concentrating a gas, wherein the zeolite membrane surface has a SiO ₂ / Al ₂ O ₃ molar ratio of 50 or more, which is a numerical value obtained by X-ray photoelectron analysis (XPS) .   The method for separating or concentrating a gas according to claim 1, wherein the mixed gas is a mixed gas containing oxygen, and oxygen is separated from the mixed gas or oxygen is permeated from the mixed gas.   The method for separating or concentrating a gas according to claim 1, wherein the mixed gas is a mixed gas containing methane and helium, and helium is separated from the mixed gas or helium is permeated from the mixed gas.   The gas separation according to claim 1, wherein the gas mixture is a gas mixture containing carbon dioxide and nitrogen, and carbon dioxide is separated from the gas mixture or carbon dioxide is permeated from the gas mixture. Concentration method.   The gas separation according to any one of claims 1 to 4, wherein the zeolite membrane is obtained by forming a zeolite by hydrothermal synthesis and then treating it in a solution containing an Si compound. Method. The natural gas is brought into contact with the separation membrane, and the highly permeable component of the natural gas is permeated to separate the highly permeable component from the natural gas, or the highly permeable component is permeated from the natural gas. A natural gas separation or concentration method for concentrating components with low permeability,
The separation membrane is a zeolite membrane formed on an inorganic porous support, and the zeolite membrane contains zeolite having a pore structure of an oxygen 8-membered ring or less, and is obtained by X-ray photoelectron analysis (XPS). A method for separating or concentrating natural gas, wherein the zeolite membrane surface SiO ₂ / Al ₂ O ₃ molar ratio, which is a numerical value obtained, is 50 or more.   The method for separating or concentrating natural gas according to claim 6, wherein the highly permeable component is helium. By separating the highly permeable component from the combustion gas by bringing the combustion gas into contact with the separation membrane, the highly permeable component is separated from the combustion gas, or the highly permeable component is transmitted from the combustion gas. A method for separating or concentrating a combustion gas that concentrates a low-permeability component,
The separation membrane is a zeolite membrane formed on an inorganic porous support, and the zeolite membrane contains zeolite having a pore structure of an oxygen 8-membered ring or less, and is obtained by X-ray photoelectron analysis (XPS). A method for separating or concentrating combustion gas, wherein the zeolite membrane surface SiO ₂ / Al ₂ O ₃ molar ratio, which is a numerical value obtained, is 50 or more.   The method for separating or concentrating combustion gas according to claim 8, wherein the highly permeable component is carbon dioxide. A method for producing a mixed gas having a high oxygen concentration by bringing a mixed gas containing oxygen into contact with a separation membrane,
The separation membrane is a zeolite membrane formed on an inorganic porous support;
The zeolite membrane includes a zeolite having a pore structure having an oxygen 8-membered ring or less,
A method for producing a high oxygen concentration mixed gas, wherein the zeolite membrane surface has a SiO ₂ / Al ₂ O ₃ molar ratio of 50 or more, which is a numerical value obtained by X-ray photoelectron analysis (XPS) .

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