JP6687075B2 - Carbon dioxide separation method - Google Patents

Description

  The present invention relates to a zeolite membrane composite for gas separation, more specifically, a zeolite membrane composite for gas separation that separates a specific gas component from a gas mixture composed of a plurality of gas components, wherein the zeolite membrane is The present invention relates to a zeolite membrane composite for gas separation, which is formed on a ceramic support and contains the zeolite crystal phase, and a gas separation method using the zeolite membrane composite as a gas separation means.

  The gas separation / purification method includes a membrane separation method, an adsorption separation method, an absorption separation method, a distillation separation method, and a cryogenic separation method, but the membrane separation method hardly involves a phase change during the gas separation, In this method, the pressure difference is used as the driving energy, and the gas is separated by the speed difference of the gas passing through the membrane. The membrane separation method is easier to handle than other gas separation / purification methods and has a relatively small facility scale, so that the target gas separation or concentration can be performed at low cost and energy saving.

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 a feature of being excellent in processability, it has been a problem that performance is deteriorated due to deterioration due to heat, chemical substances and pressure.
In recent years, various inorganic films having good chemical resistance, oxidation resistance, heat resistance stability, and pressure resistance have been proposed to solve these problems. Among them, since zeolite has regular sub-nanometer pores, it has a function as a molecular sieve, so that it can selectively permeate specific molecules and is expected to exhibit high separation performance.

  Examples of concrete membrane separation of mixed gas include carbon dioxide and nitrogen, carbon dioxide and methane, hydrogen and hydrocarbon, hydrogen and oxygen, and hydrogen and hydrogen in the separation of gases discharged from thermal power plants and petrochemical industries. Separation of carbon dioxide, nitrogen and oxygen, paraffin and olefin, etc. Zeolite membranes such as A-type membranes, FAU membranes, MFI membranes, SAPO-34 membranes and DDR membranes are known as usable zeolite membranes for gas separation.

  The A-type zeolite membrane is easily affected by moisture, it is difficult to form a membrane having no crystal gap, and the separation performance is not high. The FAU membrane has zeolite pores of 0.6 to 0.8 nm, and has a size such that two gas molecules can enter the zeolite pores. This membrane is suitable for the separation of molecules having adsorption properties to zeolite pores and those not having them, for example, separation of carbon dioxide and nitrogen. However, molecules that have no adsorptivity are difficult to separate, and the application range is narrow. The pore size of the MFI membrane is 0.55 nm, and the pores are rather large for separating gas molecules, and the separation performance is not high.

  Further, in a natural gas refining plant and a plant for biogas generation by methane fermentation of food waste, etc., separation of carbon dioxide and methane is desired, but as a zeolite membrane for separating these well, zeolite of DDR (Patent Document 1), SAPO-34 (Non-Patent Document 1), and SSZ-13 (Non-Patent Document 2) that utilize the molecular sieving function are known as high-performance membranes.

JP 2004-105942 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

  However, DDR (Patent Document 1) has a good separation performance, but has a low carbon dioxide permeance (also referred to as “permeability”) because the structure of the zeolite is two-dimensional. Further, SAPO-34 (Non-Patent Document 1), which is a CHA-type aluminophosphate having a three-dimensional structure, has good separation performance and permeance, but its performance in the presence of water deteriorates.

  Further, in a chemical plant, the mixed gas often contains water, and the performance deteriorates in the coexistence of water, and it may not be practical. Similarly, the CHA-type aluminosilicate SSZ-13 (Non-Patent Document 2), which is also a SUS support membrane, has insufficient separation ability due to the presence of non-zeolite pores (defects) in the zeolite membrane, and thus carbon dioxide. The permeance of was not enough. Thus, a separation membrane for a gas mixture that can withstand practical use has not been known.

  It is an object of the present invention to provide a zeolite membrane composite for gas separation, which is excellent in water resistance and has excellent characteristics in separating a gas mixture, in which the problems of the prior art are solved.

  As a result of intensive studies to solve the above problems, the present inventors have found that a zeolite membrane composite having certain physical properties becomes a zeolite membrane composite that has both a practically sufficient treatment amount and separation treatment performance. And proposed it (Japanese Patent Application No. 2010-043366). As a result of further studies, the present inventors have found that these zeolite membrane composites have excellent properties for separating a gas mixture, and arrived at the present invention.

That is, the gist of the present invention lies in the following (1) to (7).
(1) A gas separation method in which a gas mixture composed of a plurality of gas components is brought into contact with a zeolite membrane composite having a zeolite membrane on a ceramic support, and a highly permeable gas component is permeated and separated from the gas mixture. The zeolite constituting the zeolite membrane is a CHA-type aluminosilicate, and the CH ₂ Aluminosilicate has a SiO ₂ / Al ₂ O ₃ molar ratio of 12 or more and 100,000 or less. A method for gas separation, characterized in that the separation is carried out after a pretreatment of drying the above under a gas component having a high permeability at a temperature equal to or higher than the gas separation temperature.
(2) The zeolite membrane composite has a permeance of 1 × 10 ⁻⁹ mol · (m ² · s · Pa) ⁻¹ or more when carbon dioxide gas is permeated at a temperature of 50 ° C. and a differential pressure of 0.098 MPa. The gas separation method according to (1).
(3) The zeolite membrane composite has a permeance of 1 × 10 ⁻⁷ mol · (m ² · s · Pa) ⁻¹ or less when methane gas is transmitted at a temperature of 50 ° C. and a differential pressure of 0.098 MPa. The gas separation method according to (1) or (2).
(4) Any one of (1) to (3), in which the zeolite membrane composite has a separation coefficient of 2 or more when a mixed gas of carbon dioxide and methane is permeated at a temperature of 50 ° C. and a differential pressure of 0.098 MPa. The gas separation method described in 1.
(5) The gas separation method according to any one of (1) to (4), wherein as the pretreatment, the drying and the purge treatment with the supply gas used are performed.
(6) The gas separation method according to any one of (1) to (5), wherein the permeation side of the zeolite membrane composite is at atmospheric pressure during the drying.
(7) The gas separation method according to any one of (1) to (6), wherein in the separation, the pressure difference between the gas on the supply side and the gas on the permeation side is 0.02 to 20 MPa.

  According to the present invention, it has excellent chemical resistance, heat resistance stability, oxidation resistance, pressure resistance, a large amount of gas permeation, a high separation coefficient, high wet heat stability, and excellent gas separation characteristics. A zeolite membrane composite can be provided. Moreover, by using the zeolite membrane composite of the present invention as a gas separation means, it is possible to perform high-performance gas separation with small-scale equipment, energy saving, and low cost.

  Further, according to the present invention, a gas with a high permeability is permeated from a mixture of gases, and a gas with a low permeability is concentrated, so that the gas with a high permeability is separated out of the system, and a gas with a low permeability is obtained. The target gas can be separated from the gas mixture with high purity by concentrating and recovering.

It is a schematic diagram of the apparatus used for the permeation | transmission test of a single component gas. It is a schematic diagram of the apparatus used for the mixed gas permeation test. 2 is an XRD pattern [a in the figure] of the CHA-type zeolite membrane produced in Example 1 and an XRD pattern [b) in the figure] of a powdered CHA-type zeolite.

Hereinafter, the embodiments of the present invention will be described in more detail, but the description of the constituents described below is an example of the embodiment of the present invention, and the present invention is not limited to these contents. Various modifications can be implemented within the scope of the gist.
The gas separation zeolite membrane composite of the present invention is a gas separation zeolite membrane composite for separating a gas component having high permeability from a gas mixture composed of a plurality of gas components, wherein the zeolite membrane is , CHA-type aluminosilicate zeolite, and is formed on a ceramic support. In the present specification, the “ceramic support” may be simply referred to as “support”.

(Zeolite membrane composite for gas separation)
In the present invention, the zeolite membrane composite is used as a membrane separation means for permeating and separating a highly permeable gas component from a gas mixture composed of a plurality of gas components as described above. The gas components, separation method, separation performance, etc. will be described in the section of gas separation and separation performance after the details of the zeolite membrane composite are described.

(Zeolite membrane)
In the present invention, the components constituting the zeolite membrane may optionally contain, in addition to zeolite, an inorganic binder such as silica or alumina, an organic substance such as a polymer, or a silylating agent that modifies the surface of the zeolite.
The zeolite membrane may partially contain an amorphous component, but is preferably a zeolite membrane composed substantially of only zeolite.

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. Further, it is usually 100 μm or less, preferably 60 μm or less, and more preferably 20 μm or less. If the film thickness is too large, the permeation amount tends to decrease, and if it is too small, the selectivity or the film strength tends to decrease.
The particle size of the zeolite forming the zeolite membrane is not particularly limited, but if it is too small, the grain boundaries become large and the permeation selectivity tends to be lowered. 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. Further, it is more preferable that the particle size of zeolite is the same as the thickness of the membrane. When the particle size of the zeolite is the same as the thickness of the membrane, the grain boundary of the zeolite is the smallest. The zeolite membrane obtained by hydrothermal synthesis described later is preferable because the particle diameter of the zeolite and the membrane thickness may be the same.

  The shape of the zeolite membrane is not particularly limited, and any shape such as tubular shape, hollow fiber shape, monolith type, and honeycomb type can be adopted. The size is not particularly limited, and for example, in the case of a tubular shape, a length of 2 cm or more and 200 cm or less, an inner diameter of 0.5 cm or more and 2 cm or less, and a thickness of 0.5 mm or more and 4 mm or less are practical and preferable.

(Zeolite)
In the present invention, the zeolite constituting the zeolite membrane is CHA-type aluminosilicate.
The aluminosilicate used in the present invention mainly contains oxides of Si and Al, and may contain other elements as long as the effects of the present invention are not impaired.
The SiO ₂ / Al ₂ O ₃ molar ratio of the aluminosilicate used in the present invention is not particularly limited, but is usually 5 or more, preferably 8 or more, more preferably 10 or more, still more preferably 12 or more. is there. The upper limit is usually Al in the amount of impurities, and the SiO ₂ / Al ₂ O ₃ molar ratio is 100,000 or less. When the SiO ₂ / Al ₂ O ₃ molar ratio is less than the lower limit, the denseness of the zeolite membrane may decrease, and the durability tends to decrease. The SiO ₂ / Al ₂ O ₃ molar ratio can be adjusted by the reaction conditions of hydrothermal synthesis described later.
_{Incidentally,} SiO 2 / _Al 2 _{O 3} molar ratio, a scanning electron microscope - is a value obtained by energy dispersive X-ray spectroscopy (SEM-EDX). The X-ray accelerating voltage is usually measured at 10 kV in order to obtain information on only a few micron film.

(CHA type zeolite)
In the present invention, the CHA-type zeolite is a code that defines the structure of zeolite defined by International Zeolite Association (IZA) and has a CHA structure. It is a zeolite having a crystal structure similar 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 0.38 × 0.38 nm, and the structure is characterized by X-ray diffraction data.

The framework density (T / nm ³ ) of CHA-type zeolite is 14.5. The SiO ₂ / Al ₂ O ₃ molar ratio is the same as above.
Here, the framework density (T / nm ³ ) means the number of elements (T element) other than oxygen constituting the skeleton per nm ³ (1000 Å ³ ) of the zeolite, and this value is the structure of the zeolite. It is decided by. The relationship between framework density and zeolite structure is shown in ATLAS OF ZEOLITE FRAMEWORK TYPES Fifth Revised Edition 2001 ELSEVIER.

(Ceramic support)
The ceramic support may be any porous inorganic substance having chemical stability such that zeolite can be crystallized into a film on the surface thereof. Specific examples thereof include ceramics sintered bodies such as silica, α-alumina, γ-alumina, mullite, zirconia, titania, yttria, silicon nitride, and silicon carbide.

A part of the ceramic support has the effect of increasing the adhesiveness of the interface by forming a zeolite during the synthesis of the zeolite membrane.
Further, a ceramic support containing at least one of alumina, silica, and mullite is a membrane that is dense and has high separation performance because the support and zeolite are strongly bonded to each other because the support can be partially made into zeolite. Are more likely to be formed, which is more preferable.

The shape of the support is not particularly limited as long as it can effectively separate a gas mixture or a liquid mixture, and specifically, for example, flat plate, tubular, or cylindrical, columnar or prismatic holes. There are many honeycomb-shaped ones and monoliths.
In the present invention, a zeolite film is formed on the surface of the ceramic support or the like, and preferably zeolite is crystallized into a film.

  The average pore size of the support is not particularly limited, but those having a controlled pore size are preferable, usually 0.02 μm or more, preferably 0.05 μm or more, more preferably 0.1 μm or more, usually 20 μm or less. , Preferably 10 μm or less, more preferably 5 μm or less. If the pore size is too small, the permeation amount tends to be small, and if it is too large, the strength of the support itself tends to be insufficient, or a dense zeolite membrane tends to be difficult to form.

The surface of the support is preferably smooth, and the surface may be polished with a file or the like, if necessary. The surface of the support means the surface portion of the support on which the zeolite film is formed, and any surface of each shape may be used as long as it is a surface, and a plurality of surfaces may be used. For example, in the case of a cylindrical tube support, it may be an outer surface or an inner surface, and in some cases both outer and inner surfaces.
The pore size of the support is not particularly limited and it is not necessary to control it, but the porosity is usually preferably 20% or more and 60% or less. The porosity influences the permeation flow rate when separating gas or liquid, and when it is less than the lower limit, it tends to hinder the diffusion of permeate, and when it exceeds the upper limit, the strength of the support tends to decrease.

(Zeolite membrane composite)
Zeolite membrane composite is one in which zeolite is adhered in a film form on the surface of the support, and in some cases, a part of the zeolite is adhered to the inside of the support. preferable.
As the zeolite membrane composite, one obtained by crystallizing zeolite on the surface of a support or the like into a film by hydrothermal synthesis is preferable.

  The position of the zeolite membrane on the support is not particularly limited, and when a tubular support is used, it may be attached to the outer surface of the zeolite membrane, may be attached to the inner surface, or may be attached to both sides depending on the system to be applied. Good. Further, it may be laminated on the surface of the support, or may be crystallized so as to fill the pores of the surface layer of the support. In this case, it is important that there are no cracks or continuous fine pores inside the crystallized film layer, and formation of a so-called dense film improves the separability.

In the present invention, the zeolite membrane composite has an intensity of a peak near 2θ = 17.9 ° of 0.5 times or more of an intensity of a peak near 2θ = 20.8 ° in an X-ray diffraction pattern. Preferably there is.
Here, the peak intensity means the value obtained by subtracting the background value from the measured value. A peak intensity ratio represented by (intensity of peak near 2θ = 17.9 °) / (peak intensity near 2θ = 20.8 °) (hereinafter, this may be referred to as “peak intensity ratio A”). Therefore, it is usually 0.5 or more, preferably 0.8 or more. The upper limit is not particularly limited, but is usually 1000 or less.

In the X-ray diffraction pattern of the present invention, the intensity of the peak around 2θ = 9.6 ° is 4 times or more the intensity of the peak around 2θ = 20.8 ° in the X-ray diffraction pattern. It is preferable.
A peak intensity ratio represented by (intensity of peak near 2θ = 9.6 °) / (peak intensity near 2θ = 20.8 °) (hereinafter, this may be referred to as “peak intensity ratio B”). Therefore, it is usually 4 or more, preferably 6 or more, more preferably 8 or more, and particularly preferably 10 or more. The upper limit is not particularly limited, but is usually 1000 or less.

  Here, the X-ray diffraction pattern is obtained by irradiating the surface on the side where zeolite is mainly attached with X-rays using CuKα as a radiation source, and obtaining the scanning axis as θ / 2θ. The shape of the sample to be measured may be any shape as long as the surface of the membrane composite on which zeolite is mainly attached can be irradiated with X-rays. The body itself or a piece cut into an appropriate size restricted by the device is preferable.

The X-ray diffraction pattern referred to herein 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. The X-ray diffraction pattern when the automatic variable slit is used refers to a pattern in which the variable → fixed slit correction is performed.
Here, the peak around 2θ = 17.9 ° refers to the maximum of the peaks that do not originate from the base material and exist in the range of 17.9 ° ± 0.6 °.

The peak around 2θ = 20.8 ° refers to the maximum peak existing in the range of 20.8 ° ± 0.6 ° among the peaks not derived from the base material.
The peak near 2θ = 9.6 ° refers to the maximum of the peaks not in the base material and existing in the range of 9.6 ° ± 0.6 °.
In the X-ray diffraction pattern, the peak near 2θ = 9.6 ° is the rhombohedral setting according to the COLLECTION OF SIMULATED XRD POWDER PATTERNS FOR ZEOLITE Third Revised Edition 1996 ELSEVIER.

(No. 166) is a peak derived from the plane with the index of (1,0,0) in the CHA structure.
In addition, the peak near 2θ = 17.9 ° in the X-ray diffraction pattern shows the space group in the rhombohedral setting according to COLLECTION OF SIMULATED XRD POWDER PATTERNS FOR ZEOLITE Third Revised Edition 1996 ELSEVIER.

(No. 166) is a peak derived from the plane of which the index is (1,1,1) in the CHA structure.
In the X-ray diffraction pattern, the peak around 2θ = 20.8 ° is a rhombohedral setting according to the COLLECTION OF SIMULATED XRD POWDER PATTERNS FOR ZEOLITE Third Revised Edition 1996 ELSEVIER.

When the number is (No. 166), it is a peak derived from the plane of which the index is (2,0, -1) in the CHA structure.
A typical ratio (peak intensity ratio B) of the peak intensity derived from the (1,0,0) plane and the peak intensity derived from the (2,0, -1) plane is the COLLECTION OF SIMULATED XRD POWDER PATTERNS FOR ZEOLITE. Third Revised Edition 1996 ELSEVIER says 2.5.

Therefore, when this ratio is 4 or more, for example, when the CHA structure is set to the rhombohedral setting, the zeolite crystal is oriented so that the (1,0,0) plane is parallel to the surface of the membrane complex. It is considered to mean that they are oriented and growing. Oriented 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) between the peak intensity derived from the (1,1,1) plane and the peak intensity derived from the (2,0, -1) plane is the peak intensity ratio A, which is the COLLECTION OF SIMULATED XRD POWDER PATTERNS FOR ZEOLITE. According to Third Revised Edition 1996 ELSEVIER, it is 0.3.
Therefore, this ratio of 0.5 or more means that, for example, when the CHA structure is rhombohedral setting, the (1,1,1) plane is oriented so as to be parallel to the surface of the membrane complex. It is considered that the crystals are oriented and grown. Oriented 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, that either 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 grown, and a dense membrane having high separation performance is formed. Is shown.
A dense zeolite film in which CHA-type zeolite crystals are oriented and grown is, for example, when a zeolite film is formed by a hydrothermal synthesis method using a specific organic template in an aqueous reaction mixture as described below. Can be achieved by coexisting K ⁺ ions.

(Method for manufacturing zeolite membrane)
In the present invention, the method for producing a zeolite membrane is not particularly limited as long as it is a method capable of forming a membrane containing zeolite. For example, (1) a method of crystallizing zeolite in a membrane form on a support, (2) Method of fixing zeolite to the support with an inorganic binder or organic binder, (3) method of fixing a polymer in which zeolite is dispersed, (4) impregnating the support with a slurry of zeolite, and in some cases suctioning Any method such as a method of fixing zeolite to a support by means of can be used.

Among these, the method of crystallizing zeolite on the ceramic support in a film form is particularly preferable. The crystallization method is not particularly limited, but the support is put in a reaction mixture for hydrothermal synthesis used for zeolite production (hereinafter, this may be referred to as an “aqueous reaction mixture”), and direct hydrothermal synthesis is performed. By doing so, a method of crystallizing the zeolite on the surface of the support or the like is preferable.
Specifically, for example, the aqueous reaction mixture whose composition has been adjusted and homogenized may be placed in a heat-resistant pressure-resistant container such as an autoclave in which a support is gently fixed inside, hermetically sealed, and heated for a certain period of time.

The aqueous reaction mixture preferably contains a Si element source, an Al element source, an organic template (if necessary), and water, and further contains an alkali source if necessary.
As the Si element source used in the aqueous reaction mixture, for example, amorphous silica, colloidal silica, silica gel, sodium silicate, amorphous aluminum silicate gel, tetraethoxysilane (TEOS), trimethylethoxysilane, etc. can be used.

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

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

Specific examples include cations derived from 1-adamantanamine, cations derived from 3-quinacridinal, cations derived from alicyclic amines such as cations derived from 3-exo-aminonorbornene. Be done. Among these, the cation derived from 1-adamantanamine is more preferable.
When a cation derived from 1-adamantanamine is used as an organic template, a CHA-type zeolite capable of forming a dense film is crystallized.

  Among the cations derived from 1-adamantanamine, the N, N, N-trialkyl-1-adamantanammonium cation is more preferable. The three alkyl groups of the N, N, N-trialkyl-1-adamantanammonium cation are usually independent alkyl groups, preferably lower alkyl groups, and more preferably methyl groups. 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 zeolites. Representatives of such anions include halogen ions such as Cl ⁻ , Br ⁻ , and I ⁻ , hydroxide ions, acetates, sulfates, and carboxylates. Of these, hydroxide ion is particularly preferably used.
Further, as another organic template, N, N, N-trialkylbenzylammonium cation can also be used. Also in this case, the alkyl groups are each independently an alkyl group, preferably a lower alkyl group, and 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 above.
As the alkali source used in the aqueous reaction mixture, hydroxide ion of counter anion of organic template, alkali metal hydroxide such as NaOH and KOH, alkaline earth metal hydroxide such as Ca (OH) ₂ should be used. You can
The type of alkali is not particularly limited, and is usually Na, K, Li, Rb, Cs, Ca, Mg, Sr, Ba, preferably Na, K, and more preferably K. Further, two or more kinds of alkali may be used in combination, and specifically, it is preferable to use Na and K or Li and K in combination.

The ratio of the Si element source and the Al element source in the aqueous reaction mixture is usually expressed as the molar ratio of oxides of the respective elements, that is, the SiO ₂ / Al ₂ O ₃ molar ratio.
The SiO ₂ / Al ₂ O ₃ ratio is not particularly limited, but is usually 5 or more, preferably 8 or more, more preferably 10 or more, still more preferably 15 or more. It is usually 100,000 or less.
When the SiO ₂ / Al ₂ O ₃ ratio is in this range, the CHA-type aluminosilicate zeolite capable of forming a dense film can be crystallized.

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 ratio) is usually 0.005 or higher, preferably at least 0.01, more preferably 0. It is 02 or more, usually 1 or less, preferably 0.4 or less, and more preferably 0.2 or less. Within this range, in addition to the possibility that a dense zeolite film can be formed, the formed zeolite has strong acid resistance and Al is difficult to desorb. Under these conditions, a particularly dense and acid-resistant CHA-type aluminosilicate zeolite can be formed.

The ratio of the Si element source to the alkali source is M _{(2 / n)} O / SiO ₂ (where M represents an alkali metal or an alkaline earth metal, and n represents the valence of 1 or 2). It is usually 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.
When forming a CHA-type aluminosilicate zeolite membrane, it is preferable that potassium (K) is contained in the alkali metal from the viewpoint of producing a denser and highly crystalline membrane. In that case, the molar ratio of K to all the alkali metals and / or alkaline earth metals containing K is usually 0.01 or more, preferably 0.1 or more, more preferably 0.3 or more, and the upper limit. Is usually 1 or less.

  Addition of K to the aqueous reaction mixture was carried out in the rhombohedral setting with space groups as described above.

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

The ratio of the Si element source to water is a molar ratio of water to SiO ₂ (H ₂ O / SiO ₂ molar ratio) of usually 10 or more, preferably 30 or more, more preferably 40 or more, and particularly preferably 50 or more. It is usually 1000 or less, preferably 500 or less, more preferably 200 or less, and particularly preferably 150 or less.
When the molar ratio of the substances in the aqueous reaction mixture is in these ranges, a dense zeolite membrane can be formed. The amount of water is particularly important for the formation of a dense zeolite membrane, and finer crystals tend to be formed more easily under conditions where the amount of water is greater than that of silica, as compared to the general conditions for powder synthesis, and a dense membrane is more likely to be formed. is there.

Generally, the amount of water when synthesizing powdery CHA-type aluminosilicate zeolite is about 15 to 50 in terms of H ₂ O / SiO ₂ molar ratio. Separation of CHA-type aluminosilicate zeolite crystallized into a dense film on the surface of a support by setting a high H ₂ O / SiO ₂ molar ratio (50 or more and 1000 or less), that is, a condition in which there is a large amount of water. A highly efficient zeolite membrane composite can be obtained.

  Furthermore, during hydrothermal synthesis, seed crystals do not necessarily have to be present in the reaction system, but by adding seed crystals, crystallization of zeolite on the support can be promoted. The method of adding the seed crystal is not particularly limited, and a method of adding the seed crystal to the aqueous reaction mixture, a method of depositing the seed crystal on the support, or the like, as in the synthesis of powdered zeolite, is used. You can In the case of producing a zeolite membrane composite, it is preferable to attach seed crystals on the support. By pre-attaching the seed crystal on the support, a dense zeolite membrane having good separation performance can be easily produced.

The seed crystal to be used may be of any kind 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 aluminosilicate zeolite membrane, it is preferable to use a CHA-type zeolite seed crystal.
The seed crystal preferably has a small particle size, and may be crushed and used as necessary. The particle size is usually 0.5 nm or more, preferably 1 nm or more, more preferably 2 nm or more, and usually 5 μm or less, preferably 3 μm or less, more preferably 2 μm or less.

  The method for attaching the seed crystal to the support is not particularly limited, and for example, a dipping 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 to the surface, or a seed It is possible to use a method in which crystals are mixed with a solvent such as water to form a slurry, and the slurry is applied onto a support. The dip method is desirable in order to control the amount of seed crystals attached and to produce 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 seed crystals to be dispersed is not particularly limited, and is usually 0.01% by weight or more, preferably 0.1% by weight or more, more preferably 0.5% by weight or more, based on the total weight of the dispersion liquid. Further, it is usually 20% by weight or less, preferably 10% by weight or less, more preferably 5% by weight or less, still more preferably 3% by weight 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 there will be spots where zeolite is not partially formed on the support surface during hydrothermal synthesis, resulting in a defective film. there is a possibility. If the amount of seed crystals in the dispersion is too large, the amount of seed crystals attached to the support becomes almost constant by the dipping method, and the seed crystals are wasted, which is disadvantageous in terms of cost.

It is desirable that a seed crystal be attached to the support by a dipping method or slurry coating and then dried to form a zeolite membrane.
The weight of the seed crystal to be attached in advance 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, per 1 m ^{2 of the} substrate. It is usually 100 g or less, preferably 50 g or less, more preferably 10 g or less, and further preferably 8 g or less.

  If the amount of seed crystals is less than the lower limit, it becomes difficult to form crystals, and the film growth tends to be insufficient or the film growth tends to be non-uniform. Also, when the amount of seed crystals exceeds the upper limit, surface irregularities are increased by the seed crystals, and spontaneous crystals easily grow due to seed crystals falling from the support surface, which hinders film growth on the support. There is a case to be. In any case, it tends to be difficult to form a dense zeolite membrane.

When the zeolite membrane is formed on the support by hydrothermal synthesis, the method of immobilizing the support is not particularly limited, and any form such as vertical installation or horizontal installation can be used. In this case, the zeolite membrane may be formed by a static method, or the aqueous reaction mixture may be stirred to form the zeolite membrane.
The temperature for forming the zeolite membrane 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 the following. 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 that of the zeolite of the present invention may be easily produced.

  The heating time is not particularly limited, but is usually 1 hour or longer, preferably 5 hours or longer, more preferably 10 hours or longer, usually 10 days or shorter, preferably 5 days or shorter, more preferably 3 days or shorter, further preferably 2 hours. It is 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 that of the zeolite of the present invention may be easily produced.

The pressure for forming the zeolite membrane is not particularly limited, and the autogenous pressure generated when the aqueous reaction mixture placed in the closed container is heated to this temperature range is sufficient. Further, if necessary, an inert gas such as nitrogen may be added.
The zeolite membrane composite obtained by hydrothermal synthesis is washed with water, then heat-treated and dried. Here, the heat treatment means to apply heat to dry the zeolite membrane composite or to calcine the template when the template is used.

  For the purpose of drying, the temperature of the heat treatment is usually 50 ° C. or higher, preferably 80 ° C. or higher, more preferably 100 ° C. or higher, usually 200 ° C. or lower, preferably 150 ° C. or lower. The temperature of the heat treatment is usually 350 ° C. or higher, preferably 400 ° C. or higher, more preferably 430 ° C. or higher, still more preferably 450 ° C. or higher, and usually 900 ° C. or lower, preferably 850 ° C. or lower when the template is to be baked. The temperature is more preferably 800 ° C or lower, particularly preferably 750 ° C or lower.

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 hour or longer, more preferably 1 hour or longer. The upper limit is not particularly limited and is usually within 200 hours, preferably within 150 hours, more preferably within 100 hours.
When the hydrothermal synthesis is carried out in the presence of an organic template, the obtained zeolite membrane composite is washed with water, for example, by heat treatment or extraction, preferably heat treatment, that is, the organic template can be removed by firing. Appropriate.

  If the calcination temperature is too low, the proportion of the organic template remaining tends to increase, and the zeolite has few pores, which may reduce the amount of gas permeation during separation and concentration. If the calcination temperature is too high, the difference in the coefficient of thermal expansion between the support and the zeolite becomes large, so that the zeolite membrane may be easily cracked, the denseness of the zeolite membrane may be lost, and the separation performance may be deteriorated.

  The firing time varies depending on the temperature raising rate and the temperature lowering rate, but is not particularly limited as long as the organic template is sufficiently removed, and is preferably 1 hour or more, more preferably 5 hours or more. The upper limit is not particularly limited and is, for example, usually 200 hours or less, preferably 150 hours or less, more preferably 100 hours or less, and particularly preferably 24 hours or less. The firing may be performed in an air atmosphere, but may be performed in an atmosphere to which oxygen is added.

It is desirable that the rate of temperature rise during firing be as slow as possible in order to reduce the occurrence of cracks in the zeolite membrane due to the difference in coefficient of thermal expansion between the support and the zeolite. The rate of temperature rise is usually 5 ° C./min or less, preferably 2 ° C./min or less, more preferably 1 ° C./min or less, particularly preferably 0.5 ° C./min or less. Usually, it is 0.1 ° C./min or more in consideration of workability.
Further, it is necessary to control the temperature lowering rate after firing to prevent the zeolite membrane from cracking. As with the heating rate, the slower the more desirable. The rate of temperature decrease is usually 5 ° C./min or less, preferably 2 ° C./min or less, more preferably 1 ° C./min or less, 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 if necessary. When the ion exchange is performed using a template, the ion exchange is usually performed after removing the template. Ions to be ion-exchanged include protons, alkali metal ions such as Na ⁺ , K ⁺ and Li ⁺ , alkaline earth metal ions such as Ca ²⁺ , Mg ²⁺ , Sr ²⁺ and Ba ²⁺ , Fe, Cu, Zn and Ag. And transition metal ions of the above. Among these, alkali metal ions such as protons, Na ⁺ , K ⁺ and Li ⁺ are preferable.

The ion exchange is carried out by heating the zeolite membrane after firing (when using a template, etc.) with an ammonium salt such as NH ₄ NO ₃ , NaNO ₃ or an aqueous solution containing ions to be exchanged, and in some cases an acid such as hydrochloric acid, from room temperature. The treatment may be carried out at a temperature of 100 ° C. and then washed with water. Furthermore, you may bake at 200 degreeC-500 degreeC as needed.
The air permeation amount of the zeolite membrane composite after the heat treatment is usually 1400 L / (m ² · h) or less, preferably 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, further preferably 500 L / (m ² · h) or less, particularly preferably 300 L / (m ² · h) or less, most preferably 200 L / (m ² · h). Is. 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 when the zeolite membrane composite is placed under atmospheric pressure and the inside of the zeolite membrane composite is connected to a vacuum line of 5 kPa, as described in detail in the section of Examples. [L / (m ² · h)].
The zeolite membrane composite thus produced has excellent properties and can be suitably used as the membrane separation means for gas separation in the present invention.

(Gas separation)
The gas separation method of the present invention is characterized in that the zeolite membrane composite is brought into contact with a gas mixture composed of a plurality of gas components, and a gas component having high permeability is separated from the gas mixture. Is.
One of the separation functions of the zeolite membrane in the present invention is separation as a molecular sieve, which can preferably separate gas molecules having a size larger than the effective pore diameter of the zeolite used and gas molecules smaller than that. .

Therefore, the highly permeable gas component in the present invention is a gas component composed of gas molecules that easily pass through the pores of the zeolite crystal phase of the CHA-type aluminosilicate, and has a molecular diameter smaller than about 0.38 nm. A gaseous component consisting of molecules is preferred.
The effective pore size of zeolite can be controlled by the kind of metal to be introduced, ion exchange, acid treatment, silylation and the like. It is also possible to improve the separation performance by controlling the effective pore size.

The pore size is slightly affected by the atomic size of the metal species introduced into the zeolite framework. When a metal having an atomic diameter smaller than silicon, specifically, boron (B) or the like is introduced, the pore diameter becomes small, and a metal having an atomic diameter larger than silicon, specifically tin (Sn) or the like is used. When introducing, the pore diameter becomes large.
In addition, the pore size may be affected by desorbing the introduced metal from the skeleton by the acid treatment.

  By the ion exchange, when exchanged with monovalent ions having a large ionic radius, the effective pore size tends to decrease, whereas when exchanged with monovalent ions having a small ionic radius, the effective pore size becomes CHA structure. The value is close to the pore size of. Also in the case of divalent ions such as calcium, the effective pore diameter becomes a value close to the pore diameter of the CHA structure depending on the position of the exchange site.

The effective pore size of zeolite can also be reduced by silylation. By silencing the terminal silanols on the outer surface and further stacking a silylated layer, the effective pore size of the pores facing the outer surface of the zeolite is reduced.
Another separating function of the zeolite composite membrane of the present invention is to control the adsorptivity of gas molecules to the zeolite membrane by controlling the surface properties of the zeolite. That is, by controlling the polarity of the zeolite, it is possible to facilitate the permeation of molecules having large adsorptivity to the zeolite.

It is possible to increase the polarity by substituting Al for Si in the zeolite skeleton, and thereby, gas molecules with large polarity can be positively adsorbed and permeated into the zeolite pores. Further, when the substitution amount of Al decreases, a zeolite film having a small polarity is formed, which is advantageous for allowing gas molecules having a small polarity to permeate.
Further, Ga, Fe, B, Ti, Zr, Sn, and Zn may be added to an element source other than the Al element source to control the polarity.

In addition, the permeation performance can be controlled by controlling the adsorption performance of molecules and the zeolite pore size by ion exchange.
In the present invention, preferred gas mixtures include carbon dioxide, hydrogen, oxygen, nitrogen, methane, ethane, ethylene, propane, propylene, normal butane, isobutane, 1-butene, 2-butene, isobutene, sulfur hexafluoride, and helium. , Those containing at least one component selected from carbon monoxide, nitric oxide, water and the like. Among the components of the gas mixture containing the gas, the gas component having a high permeance passes through the zeolite membrane composite and is separated, and the gas component having a low permeance is concentrated on the supply gas side.

Further, the gas mixture more preferably contains at least two kinds of the above components. In this case, a combination of a component having high permeance and a component having low permeance is preferable as the two kinds of components.
The conditions for gas separation vary depending on the target gas species and composition, and the performance of the membrane, but the temperature is usually 0 to 300 ° C, preferably room temperature to 200 ° C, and more preferably room temperature to 150 ° C.

The pressure of the supply gas may be the same pressure as long as the gas to be separated is high pressure, or may be adjusted to a desired pressure by appropriately reducing the pressure. When the gas to be separated is lower than the pressure used for the separation, it can be used after being pressurized by a compressor or the like.
The pressure of the supply gas is not particularly limited, but is usually atmospheric pressure or higher than atmospheric pressure, preferably 0.1 MPa or more, and more preferably 0.11 MPa or more. The upper limit is usually 20 MPa or less, preferably 10 MPa or less, more preferably 1 MPa or less.

The pressure difference between the gas on the supply side and the gas on the permeation side is not particularly limited, but is usually 20 MPa or less, preferably 10 MPa or less, more preferably 5 MPa or less, further preferably 1 MPa or less. Further, it is usually 0.001 MPa or more, preferably 0.01 MPa or more, more preferably 0.02 MPa or more.
Here, the differential pressure means the difference between the partial pressure on the supply side and the partial pressure on the permeation side of the gas. The pressure [Pa] in the present invention refers to absolute pressure unless otherwise specified.

  The flow rate of the feed gas should be such that it can compensate for the decrease in the gas that permeates, and that the concentration of the gas having low permeability in the feed gas in the immediate vicinity of the membrane matches the concentration of the gas as a whole. The flow rate is such that it can be mixed, and it depends on the tube diameter of the separation unit and the separation performance of the membrane, but is usually 0.5 mm / sec or more, preferably 1 mm / sec or more, and the upper limit is not particularly limited. It is 1 m / sec or less, preferably 0.5 m / sec or less.

A sweep gas may be used in the separation method of the present invention. The method using a sweep gas is a method in which a gas of a type different from the supply gas is caused to flow on the permeate side and the gas that has permeated the membrane is recovered.
The pressure of the sweep gas is usually atmospheric pressure but is not particularly limited, preferably 20 MPa or less, more preferably 10 MPa or less, further preferably 1 MPa or less, and the lower limit is preferably 0.09 MPa or more, more preferably, It is 0.1 MPa or more. In some cases, the pressure may be reduced.

The flow rate of the sweep gas is not particularly limited, but is usually 10 ⁻⁷ mol / (m ² · s) or more and 10 ⁴ mol / (m ² · s) or less.
The device used for gas separation is not particularly limited, but is usually used as a module. The membrane module may be, for example, the apparatus shown in FIGS. 1 and 2, or may be the membrane module illustrated in “Gas Separation / Purification Technology” Toray Research Center Co., Ltd., 2007, page 22. Good.

(Separation performance)
The zeolite membrane composite of the present invention has excellent chemical resistance, oxidation resistance, heat stability, and pressure resistance, exhibits high permeation performance and separation performance, and has excellent durability. In particular, it shows excellent separation performance for separating inorganic gas and lower hydrocarbons.
The high permeation performance referred to here indicates a sufficient amount of treatment, and for example, permeance (mol · (m ² · s · Pa) ⁻¹ ] of a gas component that permeates the membrane is, for example, carbon dioxide, When permeated at a temperature of 50 ° C. and a differential pressure of 0.098 MPa, it is usually 1 × 10 ⁻⁹ or more, preferably 5 × 10 ⁻⁸ or more, more preferably 1 × 10 ⁻⁷ or more, and the upper limit is not particularly limited. , Usually 1 × 10 ⁻⁴ or less.

Further, permeance [mol · (m ² · s · Pa) ⁻¹ ] is usually 1 × 10 ⁻⁷ or less, preferably 1 × 10 ⁻⁸ or less, more preferably when methane is permeated under the same conditions. Is 5 × 10 ⁻⁹ or less, and the permeance is ideally 0, but it may be on the order of 10 ⁻¹⁰ to 10 ⁻¹⁴ or more in practical use.
Here, the permeance is obtained by dividing the amount of permeating substance by the product of the membrane area and time and the partial pressure difference between the supplying side and the permeating side of the permeating substance, and the unit is [mol · (m ² · s · Pa) ⁻¹ ], which is a value calculated by the method described in the example section. Sometimes referred to as "transparency".

Further, the selectivity of the zeolite membrane is represented by the separation coefficient. The separation coefficient is an index generally used in membrane separation and represents the selectivity, and is a value calculated by the method described in the section of Examples.
The separation coefficient is, for example, usually 2 or more, preferably 10 or more, more preferably 30 or more when a mixed gas of carbon dioxide and methane in a volume ratio of 1: 1 is permeated at a temperature of 50 ° C. and a differential pressure of 0.098 MPa. , Particularly preferably 50 or more. The upper limit of the separation coefficient is that when only carbon dioxide is completely permeated and in that case it is infinite, but in practice, the separation coefficient may be about 100,000 or less.

Zeolite membrane composite for gas separation of the present invention is, as described above, excellent in chemical resistance, oxidation resistance, heat stability, pressure resistance, high permeation performance, separation performance, and excellent durability. , And can be used particularly preferably as the following gas separation technology.
Carbon dioxide separation technology includes the removal of carbon dioxide from natural gas and landfill gas (approximately 60% methane, 40% carbon dioxide, traces of nitrogen and water vapor) generated by landfilling organic substances such as domestic waste. Carbon dioxide removal and the like.

Hydrogen separation technology includes hydrogen recovery in the petroleum refining industry, hydrogen recovery and refining in various reaction processes in the chemical industry (mixture of hydrogen, carbon monoxide, carbon dioxide, hydrocarbons, etc.), and production of high-purity hydrogen for fuel cells. and so on. Hydrogen production for fuel cells is obtained by a steam reforming reaction of methane, and it is necessary to separate hydrogen from a mixed gas of H ₂ , CO, CH ₄ , and H ₂ O.

  In addition, as oxygen separation technology, production of oxygen-enriched gas from air (medical use, combustion-enriched oxygen, etc.), nitrogen separation technology production of nitrogen-rich gas from air (explosion-proof, oxidation prevention, etc.) ), Water vapor separation (dehumidification of precision machinery, etc.), dissolved gas separation (degassing from water and organic liquids), organic gas separation (organic gas separation in petroleum refining industry, petrochemical industry, separation of olefins and paraffins), etc. Is mentioned.

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. In the following examples, the physical properties and separation performance of the zeolite membrane were measured by the following methods. Hereinafter, the "CHA type silicate zeolite" is simply referred to as "CHA type zeolite".
(1) X-ray diffraction (XRD)
The XRD measurement was performed under the following conditions.
・ Device name: X'PertPro MPD manufactured by PANalytical in the Netherlands
・ Optical system input side: Enclosed X-ray tube (CuKα)
Soller Slit (0.04 rad)
Diversity Slit (Variable Slit)
Sample stand: XYZ stage
Light receiving side: Semiconductor array detector (X'Celerator)
Ni-filter
Soller Slit (0.04 rad)
Goniometer radius: 240 mm
・ Measurement conditions X-ray output (CuKα): 45 kV, 40 mA
Scanning axis: θ / 2θ
Scanning range (2θ): 5.0-70.0 °
Measurement mode: Continueous
Read width: 0.05 °
Counting time: 99.7 sec
Automatic variable slit (Automatic-DS): 1 mm (irradiation width)
Lateral divergence mask: 10 mm (irradiation width)
The X-rays were applied in a direction perpendicular to the axial direction of the cylindrical tube. In order to reduce noise as much as possible, the X-ray is not the line that touches the surface of the sample stand, out of the two lines where the cylindrical tubular membrane composite on the sample stand and the plane parallel to the surface of the sample stand touch. , So that it mainly hits the other line above the surface of the sample table.

In addition, the irradiation width was fixed to 1 mm by an automatic variable slit and measured, and then measured by Materials Data, Inc. The XRD pattern was obtained by performing variable slit → fixed slit conversion using the XRD analysis software JADE 7.5.2 (Japanese version).
(2) SEM-EDX
・ 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.

(3) SEM
The SEM measurement was performed based on the following conditions.
-Device name: SEM: FE-SEM Hitachi: S-4100
・ Acceleration voltage: 10 kV
(4) Air permeation amount Under atmospheric pressure, one end of the zeolite membrane composite is sealed, and the other end is connected to a vacuum line of 5 kPa while maintaining airtightness, and the vacuum line and the zeolite membrane composite are connected. The flow rate of the air that passed through the zeolite membrane composite was measured with a mass flow meter installed between them, and the result was taken as the air permeation rate [L / (m ² · h)]. As the mass flow meter, 8300 manufactured by KOFLOC, for N ₂ gas, maximum flow rate 500 ml / min (20 ° C., 1 atmospheric pressure conversion) was used. When the mass flow meter displayed on the KOFLOC 8300 is less than 10 ml / min (20 ° C., 1 atm), Lintec MM-2100M for Air gas, maximum flow rate 20 ml / min (0 ° C., 1 atm) Was measured using.

(5) Single component gas permeation test The single component gas permeation test was performed as follows using the apparatus schematically shown in FIG. 1 or FIG. The sample gas used was carbon dioxide (purity 99.9%, manufactured by High Pressure Gas Industry Co., Ltd.), methane (purity 99.999%, manufactured by Japan Fine Products), hydrogen (purity 99.99% or more, HORIBA STEC hydrogen generation). Generated from OPGU-2200), nitrogen (purity 99.99%, manufactured by Toho Oxygen Industry Co., Ltd.), and 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) while being stored in a pressure resistant container 2 made of stainless steel. A temperature controller is attached to the constant 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 cylindrical end pin 3. The other end is connected by the connecting portion 4, and the other end of the connecting portion 4 is connected to the pressure resistant container 2. A pipe 11 for discharging the permeated gas 8 is connected to the inside of the cylindrical zeolite membrane composite through the connecting portion 4, and the pipe 11 extends to the outside of the pressure vessel 2. A pressure gauge 5 for measuring the pressure on the sample gas supply side is connected to the pressure-resistant container 2. Each connection part is connected airtightly.
In FIG. 2, a cylindrical zeolite membrane composite 1 is installed in a thermostatic chamber (not shown) in a state of being stored in a pressure resistant container 2 made of stainless steel. A temperature controller is attached to the constant 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 the connecting portion 4, and the other end of the connecting portion 4 is connected to the pressure resistant container 2. A pipe 11 for discharging the permeated gas 8 is connected to the inside of the cylindrical zeolite membrane composite through the connecting portion 4, and the pipe 11 extends outside the pressure vessel 2. Further, 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 resistant container 2. Each connection part is connected airtightly.

When performing a single component gas permeation test in the apparatus of FIG. 1, a sample gas (supply gas 7) is supplied between the pressure resistant container 2 and the zeolite membrane composite 1 at a constant pressure to permeate the zeolite membrane composite. The permeated gas 8 is measured with a flow meter (not shown) connected to the pipe 11.
When performing a single component gas permeation test in the apparatus of FIG. 2, 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 a back pressure valve 6 is used to supply the gas. Keep the pressure constant. The flow rate of the exhaust gas discharged from the pipe 11 is measured.
More specifically, in order to remove components such as water and air, the sample temperature and the supply gas of the zeolite membrane composite 1 are subjected to drying at a measurement temperature or higher and exhaust or purging with a supply gas to be used. After the pressure difference between the 7 side and the permeation gas 8 side was kept constant and the permeation gas flow rate became stable, the flow rate of the sample gas (permeation gas 8) that permeated the zeolite membrane composite 1 was measured, and the gas permeance [mol. (M ² · s · Pa) ⁻¹ ] is calculated. As the pressure for calculating the permeance, the pressure difference (differential pressure) between the supply side and the permeation side of the supply gas is used.

Based on the above measurement results, the ideal separation coefficient α is calculated by the following formula (1).
α = (Q ₁ / Q ₂ ) / (P ₁ / P ₂ ) (1)
[In the formula (1), Q ₁ and Q ₂ represent the permeation amounts [mol · (m ² · s) ⁻¹ ] of the gas with high permeability and the gas with low permeability, respectively, and P ₁ and P ₂ Indicate the pressures [Pa] of the gas having high permeability and the gas having low permeability, which are supply gases, respectively. ]
(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 was carbon dioxide (purity 99.9%, manufactured by High Pressure Gas Industry Co., Ltd.), methane (purity 99.999%, manufactured by Japan Fine Products), hydrogen (purity 99.99% or more, HORIBA STEC hydrogen generation). Generated from OPGU-2200), nitrogen (99.99%, manufactured by Toho Oxygen Industrial Co., Ltd.). A mixed gas was supplied at a predetermined ratio using a flow rate control device.

The specific configuration of the apparatus of FIG. 2 used for the mixed gas permeation test is as described above.
In the apparatus of FIG. 2, the sample gas (supply gas 7) is supplied at a constant flow rate between the pressure resistant container 2 and the zeolite membrane composite 1, and the back pressure valve 6 keeps the supply side pressure constant. The flow rate of the exhaust gas discharged from the pipe 11 is measured, and the exhaust gas is sampled to perform a component analysis by a gas chromatograph. When a sweep gas is used, the sweep gas 9 is made to flow from the pipe 12 to the inside of the zeolite membrane composite 1, and the flow rate of the exhaust gas (the exhaust gas of the sweep gas 9 and the accompanying permeate gas 8) discharged from the pipe 11 In addition to measuring, the exhaust gas is sampled and the components are analyzed by a gas chromatograph.

The flow velocity of each component gas that has permeated the zeolite membrane composite 1 at this time is measured as described above, and the gas permeation amount [mol · (m ² · s) ⁻¹ ] is calculated.
Based on the above measurement result, the separation coefficient α ′ is calculated by the following formula (2).
α '= (Q' ₁ / Q ' ₂ ) / (P' ₁ / P ' ₂ ) (2)
[In the formula (2), Q ′ ₁ and Q ′ ₂ represent the permeation amounts [mol · (m ² · s) ⁻¹ ] of the gas having high permeability and the gas having low permeability, respectively, and P ′ ₁ And P ′ ₂ represent the partial pressures [Pa] of the highly permeable gas and the less permeable gas in the feed gas, respectively. ]
Further, the permeance ratio may be used as an index indicating the separation performance. The permeance ratio is the ratio of the permeance of the gas with high permeability to the permeance of the gas with low permeability, and is calculated by the following formula (3).
Permeance ratio = Permeance ₁ / Permeance ₂ (3)
[In the formula (3), permeance ₁ and permeance ₂ represent permeance [mol · (m ² · s · Pa) ⁻¹ ] of a gas having high permeability and a gas having low permeability, respectively. ]
The permeance in the mixed gas permeation test is the difference between the partial pressure of each component of the gas on the supply side and the partial pressure of each component of the gas on the permeation side as the pressure difference. It is calculated by dividing by the pressure difference. Specifically, it can be calculated by the following formula (4). Permeance = Q / (P (supply) -P (transmission))
[In the formula (4), Q represents the permeation amount [mol · (m ² · s) ⁻¹ ] of the gas component to be calculated, and P (supply) and P (permeation) are calculated in the supply gas, respectively. The partial pressure [Pa] of the gas to be obtained and the partial pressure [Pa] of the gas to be calculated in the permeated gas are shown. ]
The permeation amount of each gas component in the mixed gas permeation test was calculated from the total permeation amount and composition by measuring the total permeation amount with a flow meter and the gas composition of the permeation gas by gas chromatography.

(Example 1)
(1) Preparation of CHA-Type Aluminosilicate Zeolite Membrane Composite A ceramic support-CHA-type zeolite membrane composite was prepared by directly hydrothermally synthesizing CHA-type aluminosilicate zeolite on the ceramic support.
The reaction mixture for hydrothermal synthesis was prepared as follows.

1 mol / L-NaOH aqueous solution 10.5g, 1mol / L-KOH aqueous solution 7.0 g, aluminum hydroxide to a mixture of water 100.6g _{(Al 2} O 3 53.5 mass% containing, Aldrich) 0. 88 g was added and stirred to dissolve to obtain a transparent solution. To this, as an organic template, 2.36 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 Sechem) was added, and further colloidal. 10.5 g of silica (Snowtec-40 manufactured by Nissan Chemical Co., Ltd.) was added and stirred for 2 hours to obtain an aqueous reaction mixture.

The composition (molar ratio) of this reaction mixture was SiO ₂ / Al ₂ O ₃ / NaOH / KOH / H ₂ O / TMADAOH = 1 / 0.066 / 0.15 / 0.1 / 100 / 0.04, SiO 2. ₂ / Al ₂ O ₃ = 15.
As the ceramic support, a mullite tube PM (outer diameter 12 mm, inner diameter 9 mm) manufactured by Nikkato was cut into a length of 80 mm, washed with an ultrasonic cleaner and then dried.

As a seed crystal, a 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, A CHA-type zeolite obtained by filtering, washing with water and drying a crystallized product obtained by hydrothermal synthesis at 160 ° C. for 2 days was used. The grain size of the seed crystal was about 0.3 to 3 μm.
The support was immersed in a dispersion of this seed crystal in water of about 1% by mass for a predetermined time, and then dried at 100 ° C. for 5 hours or more to attach the seed crystal. The mass of the attached seed crystal was about 0.9 g / m ² .

The support to which the seed crystal was adhered was vertically dipped in a Teflon (registered trademark) inner cylinder (200 ml) containing the above-mentioned aqueous reaction mixture, and the autoclave was sealed and left standing at 160 ° C for 48 hours. And heated under autogenous pressure. After a lapse of a predetermined time, the support-zeolite membrane composite was taken out from the reaction mixture after being left to cool, washed and dried at 100 ° C. for 5 hours or more.
This membrane composite was fired in air in an electric furnace at 550 ° C. for 10 hours. The rate of temperature rise and the rate of temperature decrease at this time were both 0.5 ° C./min. The mass of the CHA-type zeolite crystallized on the support was 154 g / m ² , which was determined from the difference between the mass of the membrane composite after firing and the mass of the support.

The film thickness obtained from SEM measurement was about 15 μm. The air permeation amount after firing was 50 L / (m ² · h).
The XRD pattern of the produced zeolite membrane is shown in FIG. * In the figure is a peak derived from the support. It was found from the XRD measurement that CHA-type zeolite was produced.
An XRD pattern of powdered CHA-type zeolite (a zeolite generally referred to as SSZ-13 in US Pat. No. 4,544,538, hereinafter referred to as "SSZ-13") is shown in FIG. 3b).

From FIG. 3, it can be seen that the XRD pattern of the produced zeolite membrane has a significantly higher peak intensity near 2θ = 17.9 ° than the XRD pattern of SSZ-13, which is a powdered CHA-type zeolite.
While the powder CHA-type zeolite SSZ-13 (peak intensity around 2θ = 17.9 °) / (peak intensity around 2θ = 20.8 °) = 0.2, (Peak intensity near 2θ = 17.9 °) / (Peak intensity near 2θ = 20.8 °) = 3.5, and the orientation to the (1,1,1) plane in rhombohedral setting is estimated. Was done.

As a result of SEM observation of the zeolite membrane composite cut into strips, crystals were densely formed on the surface.
Was also measured by _{SEM-EDX, SiO 2 / Al} 2 O 3 molar ratio of the zeolite membrane was 17.
(2) Single Component Gas Permeation Test The single component gas permeability of the CHA-type zeolite membrane composite prepared above was examined using the apparatus shown in FIG. The evaluated gases are carbon dioxide and methane.

  The zeolite membrane composite 1 was pretreated by vacuum drying at 140 ° C. and 200 Pa in advance, and then the temperature was adjusted to 50 ° C. Then, the supply gas 7 is introduced between the pressure vessel 2 and the zeolite membrane composite 1 cylinder to keep the pressure at 0.1994 MPa, and the inside of the zeolite membrane composite 1 cylinder is filled with 0.1013 MPa (atmospheric pressure). ), The temperature, the pressure on the supply gas side, and the permeation gas velocity were set to a steady state.

At this time, the differential pressure between the supply gas 7 side and the permeation gas 8 side of the zeolite membrane composite 1 was 0.098 MPa.
As a result, the permeance when carbon dioxide was used as the supply gas was 3.47 × 10 ⁻⁷ mol · (m ² · s · Pa) ⁻¹ , and the permeance when methane was used was 3.9 × 10 ^{−. It was 9} mol · (m ² · s · Pa) ⁻¹ . The ideal separation coefficient α between carbon dioxide and methane was 89.

(3) Mixed Gas Permeation Test The mixed gas permeability of the CHA-type zeolite membrane composite prepared above was examined using the apparatus shown in FIG.
As the supply gas, a mixed gas adjusted to 49% by volume of carbon dioxide and 51% by volume of methane with a flow rate adjusting device was used. The mixed gas is introduced as a supply gas 7 between the pressure vessel 2 and the zeolite membrane composite 1 at a flow rate of 12 mmol / min, the supply gas pressure is kept at 0.1994 MPa, and the sweep gas (nitrogen gas) is supplied. Flowed at 4.5 mmol / min (0.05 mol / (m ² · s). In this state, the zeolite membrane composite 1 was dried (pretreatment) at 140 ° C., then heated to 50 ° C. and left for 40 minutes or more. The temperature, the pressure on the supply gas side, and the permeated gas velocity were set to the steady state.

The inside of the cylinder of the zeolite membrane composite 1 is 0.107 MPa, and the partial pressures of carbon dioxide and methane on the side of the supply gas 7 are 0.0977 MPa and 0.102 MPa, respectively.
The permeation amount of carbon dioxide was 14.4 mmol · (m ² · s) ⁻¹ , and the permeation amount of methane was 0.205 mmol · (m ² · s) ⁻¹ . The separation coefficient α'of carbon dioxide and methane was 73.

(Example 2)
(1) Preparation of CHA-type Zeolite Membrane Composite A ceramic support-CHA-type zeolite membrane composite was prepared by directly hydrothermally synthesizing CHA-type zeolite on the ceramic support.
The reaction mixture for hydrothermal synthesis was prepared as follows.

To a mixture of 3.5 g of 1 mol / L-NaOH aqueous solution, 7 g of 1 mol / L-KOH aqueous solution, and 107.4 g of water, 0.44 g of aluminum hydroxide (containing 53.5% by mass of Al ₂ O ₃ ; manufactured by Aldrich). The solution was stirred and dissolved to give a transparent solution. As an organic template, 2.37 g of an aqueous TMADAOH solution (containing 25% by mass of TMADAOH, manufactured by Seichem Co.) was added, and further 10.5 g of colloidal silica (Snowtec-40 manufactured by Nissan Chemical Co., Ltd.) was added and stirred for 2 hours to carry out an aqueous reaction. It was a mixture.

The composition (molar ratio) of this reaction mixture is SiO ₂ / Al ₂ O ₃ / NaOH / KOH / H ₂ O / TMADAOH = 1 / 0.033 / 0.05 / 0.1 / 100 / 0.04, SiO ₂ / Al ₂ O ₃ = 30.
A CHA-type zeolite membrane composite was prepared in the same manner as in Example 1 except that the reaction mixture was used and the firing temperature was 450 ° C.

The mass of the CHA-type zeolite crystallized on the support was 154 g / m ² . The air permeation amount after firing was 50 L / (m ² · h).
It was found from the XRD measurement that CHA-type zeolite was produced. Further, (peak intensity near 2θ = 17.9 °) / (peak intensity near 2θ = 20.8 °) = 1.2, and orientation to the (1,1,1) plane in rhombohedral setting. Was inferred.

In addition, as a result of observing the CHA-type zeolite membrane composite cut into strips with an SEM, crystals were densely formed on the surface.
Was also measured by _{SEM-EDX, SiO 2 / Al} 2 O 3 molar ratio of the zeolite membrane was 22.

(2) Single component gas permeation test A single component gas permeation test was conducted in the same manner as in Example 1 except that the CHA-type zeolite membrane composite prepared above was used. The evaluated gases are carbon dioxide and methane.
The permeance of carbon dioxide is 3.50 × 10 ⁻⁷ mol · (m ² · s · Pa) ⁻¹ , the permeance of methane is 2.46 × 10 ⁻⁹ mol · (m ² · s · Pa) ⁻¹ , dioxide. The ideal separation coefficient α between carbon and methane was 142.

(3) Mixed gas permeation test A mixed gas permeation test was performed in the same manner as in Example 1 except that the CHA-type zeolite membrane composite prepared above was used.
The permeation amount of carbon dioxide was 16.5 mmol · (m ² · s) ⁻¹ , the permeation amount of methane was 0.132 mmol · (m ² · s) ⁻¹ , and the separation coefficient α ′ of carbon dioxide and methane was 130. It was

(Example 3)
Using a CHA-type zeolite membrane composite produced in the same manner as in Example 2 except that the firing temperature was 500 ° C., and except that the pressure of the supply gas was 0.2975 MPa, A mixed gas permeation test was conducted. The evaluated gases are carbon dioxide and methane.
The permeation amount of carbon dioxide was 25.0 mmol · (m ² · s) ⁻¹ , the permeation amount of methane was 0.191 mmol · (m ² · s) ⁻¹ , and the separation coefficient α ′ between carbon dioxide and methane was 136. It was

(Example 4)
(1) Single-component gas permeation test The single-gas component permeability of the CHA-type zeolite membrane composite prepared in the same manner as in Example 2 except that the firing temperature was 500 ° C was evaluated using the apparatus shown in Fig. 2. . The gases evaluated are carbon dioxide, methane, hydrogen, nitrogen and helium.

The zeolite membrane composite was introduced at 140 ° C. with He as a feed gas 7 between the pressure vessel 2 and the zeolite membrane composite 1 to keep the pressure at 0.400 MPa. The inside of the cylinder was set to 0.100 MPa (atmospheric pressure), dried for 120 minutes, and pretreated.
After that, the pressure on the supply side was set to 0.200 MPa, and the supply gas was changed to each evaluation gas. At this time, the differential pressure between the supply gas 7 side and the permeation gas 8 side of the zeolite membrane composite 1 was 0.100 MPa.

After that, the temperature was set to 50 ° C., and after the temperature became stable, the supply gas was changed to each evaluation gas. At this time, the differential pressure between the supply gas 7 side and the permeation gas 8 side of the zeolite membrane composite 1 was 0.100 MPa.
The permeance of each gas thus obtained is shown in Table 1. The ideal separation coefficient α of carbon dioxide and methane at 50 ° C is 783, the ideal separation coefficient α of hydrogen and methane is 264, the ideal separation coefficient α of nitrogen and methane is 48, and the ideal separation coefficient α of carbon dioxide and methane at 140 ° C is The ideal separation coefficient α was 171, the ideal separation coefficient α of hydrogen and methane was 94, and the ideal separation coefficient α of nitrogen and methane was 12.

The mixed gas permeability of the CHA-type zeolite membrane composite prepared above was examined using the apparatus of FIG. Specifically, the following mixed gas permeation tests 1 to 4 were performed. Drying (pretreatment) was performed in the same manner as the single gas permeation test.
(2) Mixed gas permeation test 1
As the supply gas, a mixed gas adjusted to 75% by volume of carbon dioxide and 25% by volume of methane by a flow rate adjusting device was used. It was introduced at a flow rate of 40, 24, 8 mmol / min between the pressure vessel and the cylinder of the zeolite membrane composite 1 of FIG. 2, and the supply gas pressure was 0.300 MPa. The partial pressures of carbon dioxide and methane are 0.225 MPa and 0.0750 MPa, respectively. The inside of the cylinder of the zeolite membrane composite 1 is 0.100 MPa.

  Table 2 shows the permeation amount of carbon dioxide and methane, and the separation coefficient of carbon dioxide and methane. The separation factor was small under the condition that the total flow rate was small. It is considered that when the flow rate is small, the mixing of the feed gas is not sufficient and the methane concentration in the immediate vicinity of the outside of the membrane is high.

(3) Mixed gas permeation test 2
As the supply gas, a mixed gas adjusted to 28% by volume of hydrogen and 72% by volume of methane by a flow rate adjusting device was used. The constant temperature bath was set to 50 ° C., and the gas was introduced between the pressure vessel of FIG. 2 and the cylinder of the zeolite membrane composite 1 at the flow rates of 45, 27 and 9 mmol / min, and the supply gas pressure was set to 0.300 MPa. The partial pressures of hydrogen and methane on the supply gas 7 side are 0.112 MPa and 0.288 MPa, respectively. The inside of the cylinder of the zeolite membrane composite 1 is 0.100 MPa.

  Table 3 shows the permeation amount of hydrogen and methane, and the separation coefficient of hydrogen and methane. The separation factor was small under the condition that the total flow rate was small. It is considered that when the flow rate is small, the mixing of the feed gas is not sufficient and the methane concentration in the immediate vicinity of the outside of the membrane is high.

(4) Mixed gas permeation test 3
A standard gas containing 55% nitrogen, 30% carbon monoxide, and 15% hydrogen was used as the supply gas. The temperature of the constant temperature bath was 50 ° C., and the gas was introduced between the pressure vessel of FIG. 2 and the cylinder of the zeolite membrane composite 1 at a flow rate of 27 mmol / min, and the supply gas pressure was 0.300 MPa.
The partial pressures of nitrogen, carbon monoxide, and methane on the supply gas 7 side are 0.166 MPa, 0.0900 MPa, and 0.0440 MPa, respectively. The inside of the cylinder of the zeolite membrane composite 1 is 0.100 MPa.

Nitrogen, carbon monoxide, permeation amount of hydrogen is respectively ^{2.1mmol · (m 2 · s)} -1, 3.8mmol · (m 2 · s) -1, 2.9mmol · (m 2 · s) -1 The separation factors α'of carbon monoxide and nitrogen, hydrogen and nitrogen were 1.4 and 2.1, respectively, and the permeance ratio was 1.6 and 3.4.

(5) Mixed gas permeation test 4
Air was used as the supply gas. The temperature of the constant temperature bath was 50 ° C., and the gas was introduced between the pressure vessel of FIG. 2 and the cylinder of the zeolite membrane composite 1 at a flow rate of 27 mmol / min, and the supply gas pressure was 0.300 MPa.
The permeation amounts of nitrogen and oxygen are 5.2 mmol · (m ² · s) ⁻¹ and 1.9 mmol · (m ² · s) ⁻¹ , respectively, and the separation coefficient α ′ of oxygen and nitrogen is 1.4, The permeance ratio was 1.6. The results are shown in Table 5.

(Example 5)
(1) Preparation of CHA-type Zeolite Membrane Composite Inorganic porous support-CHA-type as in Example 1 except that the following reaction mixture was prepared for hydrothermal synthesis and the firing temperature was 500 ° C. A zeolite membrane composite was prepared.
The reaction mixture for hydrothermal synthesis was a mixture of 14.0 g of a 1 mol / L-KOH aqueous solution and 104.0 g of water, 0.29 g of lithium hydroxide monohydrate and 53.5 wt% of aluminum hydroxide (Al ₂ O _{3 5} ). %, 1.33 g (manufactured by Aldrich Co.) was added and stirred to dissolve to obtain a transparent solution. To this, 2.37 g of an aqueous TMADAOH solution (containing 25% by weight of TMADAOH, manufactured by Seichem Co.) was added, and further 10.5 g of colloidal silica (Snowtec-40 manufactured by Nissan Chemical Co., Ltd.) was added and stirred for 2 hours to prepare.

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. ₂ / Al ₂ O ₃ = 10.
The weight of the CHA-type zeolite crystallized on the support was 120 g / m ² , which was determined from the difference between the weight of the zeolite membrane composite after firing and the weight of the support.

The air permeation amount of the zeolite membrane composite after firing was 147 L / (m ² · h).
When the XRD of the produced film was measured, it was found that CHA-type zeolite was produced. From the XRD pattern, (the intensity of the peak near 2θ = 17.9 °) / (the intensity of the peak near 2θ = 20.8 °) = 0.8, and the XRD of the powdered CHA-type zeolite used as the seed crystal. The intensity of the peak around 2θ = 17.9 ° was remarkably larger than that of the above, and the orientation to the (1,1,1) plane in the rhombohedral setting was estimated.

As a result of observing the inorganic porous support-CHA type zeolite membrane composite cut into strips with an SEM, crystals were densely formed on the surface.
Was also measured by _{SEM-EDX, SiO 2 / Al} 2 O 3 molar ratio of the zeolite membrane was 19.
(2) Single component gas permeation test A single component gas permeation test was conducted in the same manner as in Example 1 except that the CHA-type zeolite membrane composite prepared above was used. The evaluated gases are carbon dioxide and methane.

The permeance of carbon dioxide is 7.13 × 10 ⁻⁷ mol · (m ² · s · Pa) ⁻¹ , the permeance of methane is 6.07 × 10 ⁻⁹ mol · (m ² · s · Pa) ⁻¹ , dioxide. The ideal separation coefficient α between carbon and methane was 117.
(Example 6)
(1) Preparation of CHA-type zeolite membrane composite As a reaction mixture for hydrothermal synthesis, the following were prepared, and the heating temperature was kept at 160 ° C. under autogenous pressure for 5 days, and the firing temperature was 500 ° C. An inorganic porous support-CHA type zeolite membrane composite was prepared in the same manner as in Example 1 except for the above.

The reaction mixture for hydrothermal synthesis was a mixture of 15.0 g of a 1 mol / L-NaOH aqueous solution and 75.0 g of water, and 0.71 g of aluminum hydroxide (containing 53.5% by weight of Al ₂ O ₃ manufactured by Aldrich). The solution was stirred and dissolved to give a transparent solution. To this, 25.3 g of an aqueous solution of TMADAOH (containing 25% by weight of TMADAOH, manufactured by Seichem Co.) was added, and further, a mixture of 9.0 g of fumed silica (Aerosil 200 manufactured by Nippon Aerosil Co., Ltd.) and 10.0 g of water was added and stirred for 2 hours. Was prepared.

The composition of the reaction mixture (molar _{ratio), SiO 2 / Al 2 O 3} / NaOH / H 2 O / TMADAOH = 1 / 0.025 / 0.1 / 44 / 0.2, SiO 2 / Al 2 O 3 = 40.
The weight of the CHA-type zeolite crystallized on the support, which was determined from the difference between the weight of the zeolite membrane composite after firing and the weight of the support, was 330 g / m ² .

The air permeation rate of the zeolite membrane composite after firing was 67 L / (m ² · h).
When the XRD of the produced film was measured, it was found that CHA-type zeolite was produced. In the XRD pattern, (intensity of peak near 2θ = 9.6 °) / (intensity of peak near 2θ = 20.8 °) = 1.5, intensity of peak near 2θ = 17.9 °) / ( The intensity of the peak near 2θ = 20.8 °) was 0.3. Thus, none of the produced films showed a specific intensity for the XRD peak. From this, it can be inferred that, for example, the formed film is not oriented on either the (1,0,0) plane or the (1,1,1) plane in the rhombohedral setting.

(2) Single component gas permeation test A single component gas permeation test was conducted in the same manner as in Example 1 except that the CHA-type zeolite membrane composite prepared above was used.
The permeance of carbon dioxide is 9.29 × 10 ⁻⁷ mol · (m ² · s · Pa) ⁻¹ , the permeance of methane is 1.27 × 10 ⁻⁹ mol · (m ² · s · Pa) ⁻¹ , dioxide. The ideal separation coefficient α between carbon and methane was 7.3.

(Example 7)
As the ceramic support, an inorganic porous support-CHA type zeolite was used in the same manner as in Example 2 except that a porous alumina tube having a length of 80 mm (outer diameter 12 mm, inner diameter 9 mm) was used and the firing temperature was 500 ° C. A membrane complex was prepared.
The weight of the CHA-type zeolite crystallized on the support, which was determined from the difference between the weight of the zeolite membrane composite after firing and the weight of the support, was 157 g / m ² .

The air permeation amount of the zeolite membrane composite after firing was 81.7 L / (m ² · min).
When the XRD of the produced film was measured, it was found that CHA-type zeolite was produced. In the XRD pattern, from the XRD pattern, (peak intensity near 2θ = 17.9 °) / (peak intensity near 2θ = 20.8 °) = 2.0, and CHA of the powder used for the seed crystal was obtained. The intensity of the peak around 2θ = 17.9 ° was remarkably large as compared with the XRD of the type zeolite, and the orientation to the (1,1,1) plane in the rhombohedral setting was estimated.

(2) Single-component gas permeation test A single-component gas permeation test was performed using the CHA-type zeolite membrane composite prepared above. As a pretreatment, the zeolite membrane composite was introduced at 140 ° C. into the cylinder between the pressure vessel 2 and the zeolite membrane composite 1 by introducing CO 2 as a supply gas 7 to keep the pressure at 0.200 MPa. The inside of the cylinder of the composite 1 was set to 0.098 MPa (atmospheric pressure) and dried for 70 minutes. A single component gas permeation test was performed in the same manner as in Example 4 except for the above. The gases evaluated are carbon dioxide, methane, hydrogen, nitrogen and helium.

  Table 6 shows the permeance of each gas thus obtained. The ideal separation coefficient α of carbon dioxide and methane at 50 ° C is 368, the ideal separation coefficient α of hydrogen and methane is 130, the ideal separation coefficient α of nitrogen and methane is 21, and the ideal separation coefficient α of carbon dioxide and methane at 140 ° C is The ideal separation coefficient α was 54, the ideal separation coefficient α of hydrogen and methane was 41, and the ideal separation coefficient α of nitrogen and methane was 5.

(Comparative Example 1)
A ceramic support-MFI type zeolite membrane composite was prepared by directly hydrothermally synthesizing MFI type zeolite on the ceramic support.
The reaction mixture for hydrothermal synthesis was prepared as follows.
To 118 g of water, 4.1 g of an aqueous solution of tetrapropylammonium hydroxide (hereinafter referred to as "TPAOH") (containing 40% by mass of TPAOH, manufactured by Sechem) was added as an organic template, and tetraethoxysilane (hereinafter referred to as " TEOS ".) 9.9 g was added and stirred for 2 hours to give an aqueous reaction mixture.

The composition (molar ratio) of this reaction mixture is TEOS / TPAOH / H ₂ O = 1 / 0.17 / 140.
As the ceramics support, a porous alumina tube (outer diameter 12 mm, inner diameter 9 mm) cut into a length of 80 mm, washed with an ultrasonic cleaner and then dried was used. As a seed crystal, a gel composition (molar ratio) of SiO ₂ / NaOH / TPAOH / H ₂ O = 1 / 0.1 / 0.1 / 40, which was crystallized by hydrothermal synthesis at 160 ° C. for 1 day The MFI zeolite obtained by filtering, washing with water and drying was used.

The support was immersed in a dispersion of this seed crystal in water of about 1% by mass for a predetermined time, and then dried at 100 ° C. for 5 hours or more to attach the seed crystal. The mass of the attached seed crystal was about 1.6 g / m ² .
The support to which the seed crystal was adhered was vertically dipped in a Teflon (registered trademark) inner cylinder (200 ml) containing the above-mentioned aqueous reaction mixture, and the autoclave was sealed and left standing at 160 ° C for 48 hours. And heated under autogenous pressure. After a lapse of a predetermined time, the support-zeolite membrane composite was taken out from the reaction mixture after being left to cool, washed and dried at 100 ° C. for 5 hours or more.

The membrane composite was fired in air in an electric furnace at 450 ° C. for 32 hours. The rate of temperature rise and the rate of temperature decrease at this time were both 0.5 ° C./min. The mass of the MFI-type zeolite crystallized on the support was 85 g / m ² , which was determined from the difference between the mass of the membrane composite after calcination and the mass of the support.
From the XRD measurement, it was found that MFI type zeolite was produced.
(2) Single-component gas permeation test A single-component gas permeation test was conducted in the same manner as in Example 7 except that the MFI-type zeolite membrane composite prepared above was used. The gases evaluated are carbon dioxide, methane, hydrogen, nitrogen and helium.

  The permeance of each gas thus obtained is shown in Table 7. The ideal separation factor α for carbon dioxide and methane at 50 ° C is 1.2, the ideal separation factor α for hydrogen and methane is 1.0, the ideal separation factor α for nitrogen and methane is 0.5, and at 140 ° C The ideal separation coefficient α between carbon dioxide and methane was 0.7, the ideal separation coefficient α between hydrogen and methane was 1.2, and the ideal separation coefficient α between nitrogen and methane was 0.5.

  As in Examples 1 to 7, when a gas permeability evaluation is performed using a zeolite membrane containing a CHA-type aluminosilicate zeolite and formed on a ceramic support, the gas permeability may differ depending on the gas. Recognize. When mixed gas is used, gas with high permeability permeates the membrane, gas with low permeability concentrates without passing through the membrane, gas with high permeability is separated from the system, and gas with low permeability is used. It was possible to separate the target gas with high purity from the gas mixture by concentrating and recovering.

  On the other hand, when the gas permeability is evaluated using a zeolite membrane containing MFI-type aluminosilicate zeolite and formed on a ceramic support, the gas permeability is almost uniform regardless of the gas. became. It is considered that the MFI membrane cannot be subjected to shape-selective separation because the evaluated gas molecular diameters are all smaller than the pore diameter.

  INDUSTRIAL APPLICABILITY The present invention can be used in any industrial fields, for example, separation of a gas mixture in a chemical industry plant that requires gas separation, a natural gas refining plant, a plant that generates biogas from garbage, etc. Can be used particularly preferably.

1 Zeolite Membrane Complex 2 Pressure Resistant Container 3 End Pin 4 Connection 5 Pressure Gauge 6 Back Pressure Valve 7 Supply Gas 8 Permeate Gas 9 Sweep Gas 10 Exhaust Gas 11 Permeate Gas Discharge Pipe 12 Sweep Gas Introduce Pipe

Claims (7)

A method for separating carbon dioxide in which a gas mixture containing carbon dioxide and methane is brought into contact with a zeolite membrane composite having a zeolite membrane on a ceramic support, and carbon dioxide is permeated and separated from the gas mixture,
The zeolite constituting the zeolite membrane is CHA-type aluminosilicate ,
A method for separating carbon dioxide, which comprises subjecting the zeolite membrane composite to a treatment with carbon dioxide and then performing the separation. The zeolite membrane composite has a permeance of 1 × 10 ⁻⁹ mol · (m ² · s · Pa) ⁻¹ or more when carbon dioxide gas is permeated at a temperature of 50 ° C. and a differential pressure of 0.098 MPa. Item 2. The method for separating carbon dioxide according to Item 1. The zeolite membrane composite has a permeance of 1 × 10 ⁻⁷ mol · (m ² · s · Pa) ⁻¹ or less when methane gas is permeated at a temperature of 50 ° C. and a differential pressure of 0.098 MPa. Or the method for separating carbon dioxide according to 2. 4. The separation coefficient when the zeolite membrane composite permeates a mixed gas of carbon dioxide and methane at a temperature of 50 ° C. and a differential pressure of 0.098 MPa, is 2 or more. Carbon dioxide separation method. The method for separating carbon dioxide according to claim 1, wherein the zeolite membrane has a thickness of 20 μm or less. The method for separating carbon dioxide according to any one of claims 1 to 5, wherein the permeation side of the zeolite membrane composite is set to atmospheric pressure during the treatment with the carbon dioxide . The carbon dioxide separation method according to any one of claims 1 to 6, wherein in the separation, the pressure difference between the gas on the supply side and the gas on the permeation side is 0.02 to 20 MPa.

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