Manufacturing method of graphene-encapsulated porous particle material and manufacturing method of separation membrane

Abstract

To provide a manufacturing method capable of stably coating the surface of a porous particle material such as zeolite microcrystals with graphene oxide.SOLUTION: The inventors found a manufacturing method that can exhibit stable molecular sieving properties when forming a separation membrane by applying high shear force when mixing zeolite microcrystals and graphene oxide in water, and completed the present invention. The manufacturing method of graphene-encapsulated porous particle material of the present invention that solves the above problem comprises a dispersion step of preparing a dispersion liquid in which a porous particle material and graphene oxide are dispersed in water to form a composite, and a reduction step of reducing the composite to obtain a graphene-encapsulated porous particle material, wherein the dispersion step has a stirring step of stirring a mixture of the porous particle material, the graphene oxide, and the water using stirring blades under conditions that apply a stirring energy amount of 200 to 6,000 (kW s / m3) to form the composite.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for producing a graphene-inclusion porous particle material and a method for producing a separation membrane.

Background Art

[0002] Zeolite has pores inherent to the crystal and is a substance that can be expected to have ideal molecular sieve properties. Zeolite is generally obtained as a powder crystal, but in order to fully exhibit its properties as a molecular sieve, it is desirable to create a macro zeolite membrane.

[0003] However, if there are defects such as cracks in the zeolite membrane, the separation function does not work at the defective part. Therefore, in order to fully exhibit the separation function by the zeolite membrane, a macro zeolite membrane without any defects must be prepared. Considerable know-how is required to fabricate such a zeolite membrane.

[0004] As a method for producing a macro zeolite membrane using zeolite microcrystals, there is a method of depositing a zeolite membrane on a support of a porous body such as alumina by a hydrothermal synthesis method or a vapor phase method using silica and alumina as starting materials (Patent Document 1). In addition, a method of forming a zeolite membrane on a support using zeolite microcrystals as seed crystals has also been reported (Patent Document 3). The pore diameter of the zeolite crystal is about 1.0 nm, and it can be suitably used as a separation membrane for selectively separating a specific component from a mixture of multiple components.

[0005] In order to solve the problem, an invention has been made to obtain a zeolite separation membrane formed by binding zeolite microcrystals to each other, wherein the surface of each zeolite microcrystal is coated with graphene, and the zeolite microcrystals are bound without gaps through the graphene (Patent Document 5).

Prior Art Documents

Patent Documents

[0006] Patent Document 1 Japanese Unexamined Patent Application Publication No. 2003-210950 Patent Document 2 Japanese Unexamined Patent Application Publication No. 2013-59714 Patent Document 3 Japanese Unexamined Patent Application Publication No. 2016-174996 Patent Document 4 Japanese Unexamined Patent Application Publication No. 2016-179417 Patent Document 5 Japanese Unexamined Patent Application Publication No. 2018-192378 Summary of the Invention Problems to be Solved by the Invention

[0007] In Patent Document 5, in order to coat graphene on the surface of zeolite microcrystals, zeolite microcrystals and graphene oxide are mixed in water and included / coated by pH adjustment. However, due to the mixing state at that time, the coating state of graphene changes, and a problem has been found that the molecular sieve property of the obtained separation membrane is difficult to be stable.

[0008] The present invention has been completed in view of the above circumstances, and an object to be solved is to provide a manufacturing method capable of stably coating graphene oxide on the surface of porous particle materials such as zeolite microcrystals. Furthermore, another object to be solved is to provide a method for manufacturing a zeolite separation membrane using the graphene-included porous particle material manufactured by the method. Means for Solving the Problems

[0009] As a result of intensive studies, the present inventors have found a manufacturing method capable of expressing stable molecular sieve property when forming a separation membrane by applying a controlled shear force when mixing zeolite microcrystals and graphene oxide in water, and have completed the present invention.

[0010] The manufacturing method of the graphene-included porous particle material of the present invention for solving the above problems includes a dispersion step of dispersing a porous particle material and graphene oxide in water to prepare a dispersion liquid as a composite, and a reduction step of reducing the composite to obtain a graphene-included porous particle material. In the dispersion step, for a mixture of the porous particle material, the graphene oxide, and the water, stirring is performed using a stirring blade under the condition of applying a stirring energy amount of 200 to 6,000 (kW·s / m 3 ) to form the composite.

Advantages of the Invention

[0011] By having the above configuration, the manufacturing method of the graphene-included porous particle material of the present invention can obtain a porous particle material (graphene-included porous particle material) whose surface is coated with graphene and / or graphene oxide.

Embodiments for Carrying out the Invention

[0012] The manufacturing method of the graphene-included porous particle material of the present invention and the manufacturing method of the separation membrane will be described in detail based on the following embodiments. The manufacturing method of the graphene-included porous particle material of the present embodiment is a method for manufacturing a graphene-included porous particle material, which is a porous particle material whose surface is coated with graphene and / or graphene oxide. The manufactured graphene-included porous particle material can be expected to function as a high-performance separation membrane by forming a film.

[0013] In addition, although numerical ranges may be defined in this specification, unless otherwise specifically limited, both the upper and lower limit values are included in the numerical range. Further, using the numerical values described in this specification, numerical ranges with those numerical values as the upper or lower limit values can be added by correction. Also, a numerical range with two described numerical values as the upper and lower limit values can be added by correction. Here, regardless of how the numerical values are described, they can be adopted as the upper and lower limit values of the numerical range. Furthermore, the numerical ranges added by these corrections can include the upper limit value or not. The same applies to the lower limit value, which can be included in the numerical range or not. The upper limit value and the lower limit value can be independently included in the numerical range or not included.

[0014] (Method for Producing Graphene-Inclusion Porous Particle Material) The method for producing the graphene-inclusion porous particle material of this embodiment has a dispersion step, a reduction step, and other steps that are adopted as necessary. The porous particle material is a particle material having pores communicating with the outside. Since the graphene can enclose and bond the porous particle materials without gaps, when passing through the formed film, it will pass through the inside of the porous particle material. Examples of the porous particle material include zeolite microcrystals, metal-organic frameworks (MOFs), and mesoporous silica.

[0015] ·Dispersion step The dispersion process is a process of preparing a dispersion in which a porous particle material and graphene oxide are dispersed in water to form a composite, and particularly includes a step of applying a shearing force to a mixture of the porous particle material, graphene oxide, and water. The mixing ratio of the porous particle material and graphene oxide is not limited, but the lower limit of adding graphene oxide to 100 parts by mass of the porous particle material can be 2 parts by mass, 5 parts by mass, or 10 parts by mass, and the upper limit can be 40 parts by mass, 30 parts by mass, or 20 parts by mass. The addition amounts of the porous particle material and graphene oxide in the mixture are not particularly limited, but based on the mass of the entire mixture, the lower limit can be 0.01%, 0.1%, or 1%, and the upper limit can be 10%, 5%, or 3%. These upper and lower limits can be arbitrarily combined. Further, it is preferable that the viscosity of the mixture is 0.1 to 10,000 (mPa·s), and more preferably 0.5 to 500 (mPa·s).

[0016] The size of the porous particle material is not particularly limited, but as the upper and lower limits, about 50 nm, 100 nm, 500 nm, 750 nm, 1 μm, 2.5 μm, 4 μm, 5 μm, 7.5 μm, 10 μm, 15 μm, 20 μm, 30 μm, 50 μm, 75 μm, 100 μm can be adopted. These values can be arbitrarily combined. The shape of the particles can be spherical, crushed, amorphous, or any other shape.

[0017] The shape of graphene oxide is not particularly limited, but it is preferably a general thin film shape. The size of graphene oxide is also not particularly limited, but examples include those with a major axis diameter and minor axis diameter of about 10 nm to 100 nm and a thickness of about 1 nm to 10 nm.

[0018] The water used is not particularly limited, but it is preferable to use pure water with an extremely low impurity content or no impurities.

[0019] The method for preparing a mixture of a porous particle material, graphene oxide, and water is not particularly limited. For example, the porous particle material and graphene oxide may be simultaneously added to water and stirred, or water may be added to the porous particle material and graphene oxide and stirred. It can also be added while stirring. The porous particle material and graphene oxide can also be added to water step by step. Furthermore, the porous particle material and graphene oxide may be added simultaneously or separately. For example, the porous particle material can be first added to water and dispersed, and then graphene oxide can be added and dispersed. When adding separately, it can be mixed every time it is added, and the pH can be adjusted. Among the porous particle materials, the surface state of zeolite microcrystals varies greatly due to fluctuations in pH. Therefore, it is preferable to disperse the zeolite microcrystals in water first, then adjust the pH to 2 - 6, and then add and mix graphene oxide.

[0020] In the dispersion step, it is carried out by stirring using a stirring blade. Stirring is carried out under the condition of imparting a stirring energy amount of 200 - 6,000 (kW·s / m 3 ) to the mixture. By carrying out stirring, the porous particle material and graphene oxide are well mixed to form a composite.

[0021] The lower limit of the stirring energy amount is preferably 250 (kW·s / m 3 ), 300 (kW·s / m 3 ), 350 (kW·s / m 3 ), 400 (kW·s / m 3 ), and the upper limit is preferably 5000 (kW·s / m 3 ), 4000 (kW·s / m 3 ), 3000 (kW·s / m 3 ), 2500 (kW·s / m 3 ). These upper and lower limit values can be arbitrarily combined.

[0022] · Reduction step The reduction step is a step of reducing the composite contained in the dispersion obtained by the dispersion step to obtain a graphene-included porous particle material. The reduction is preferably performed on the composite in a state separated from the dispersion. For example, the composite can be separated by drying by heating or reducing the pressure, or the composite can be separated by filtering the composite from the dispersion.

[0023] In the reduction step, a part or all of the graphene oxide contained in the composite is reduced to graphene. In particular, it is preferable to reduce all of the graphene oxide to graphene. The reduction step may be any operation as long as it can reduce graphene oxide. For example, it can be reduced by holding the composite in a reducing atmosphere. Examples of the reducing atmosphere include an atmosphere of heating in an inert gas such as nitrogen (thermal reduction), a reducing gas, and the like. As an example of the conditions for thermal reduction, there is a condition of heating in nitrogen gas at 300 °C or higher (for example, 350 °C) for 1 hour or longer (for example, 1.5 hours).

[0024] · Film formation step A zeolite separation membrane can be formed by forming a film of the obtained graphene-included porous particle material. The film formation method is not particularly limited. The film formation step may be performed at any time before or after the reduction step as long as it is after the dispersion step. That is, the above-mentioned reduction step may be performed in a film-formed state.

[0025] As a specific film formation method, particles composed of the graphene-included porous particle material can be pressed by pressing or the like to form a film, or a mixture in a state where the composite is dispersed in water can be passed through a filter or the like and laminated on the filter to form a film.

Example

[0026] The method for producing the graphene-included porous particle material of the present invention and the method for producing the zeolite separation membrane will be described in detail below based on examples.

[0027] · Test example 1 Zeolite microcrystals as a porous particle material (manufactured by Tosoh Corporation, HSZ822-HOA: ZSM-5, pore diameter 5.8 Å, cation (hydrogen), SiO2 / Al2O3 ratio = 24, specific surface area 330 m 2 / g, crystal size 0.1 μm × 0.5 μm, particle size 5 μm, NH3-TPD 1.8 mmol / g) 10 parts by mass of a 1% by mass aqueous dispersion, 6.2 parts by mass of a 0.1% by mass aqueous dispersion of graphene oxide, and 97 parts by mass of ion-exchanged water were mixed to form a mixture. Then, using a stirrer, shear force was applied by stirring the mixture under the conditions shown in Table 1 to obtain a test sample for this test example. The amount of stirring energy input was 0.5 kW·s / m 3 .

[0028] Observation of the obtained test sample revealed that the zeolite microcrystals and graphene oxide were separated and no zeolite separation membrane was formed (inclusion state evaluation: ×). The test conditions are shown in Table 1.

[0029] · Test Examples 2 to 4 Test Example 2 (stirring energy amount: 5.3 kW·s / m 3 ), Test Example 3 (stirring energy amount: 4.3 kW·s / m 3 ), and Test Example 4 (stirring energy amount: 43 kW·s / m 3 ) were used, and the same operations as in Test Example 1 were performed to obtain test samples for each test example. All the test samples of Test Examples 2 to 4 were separated and no zeolite separation membrane was formed. The test conditions are shown in Table 1.

[0030] · Test Example 5 The mixture prepared in Test Example 1 was stirred using a stirrer to complex zeolite and graphene oxide. The obtained complex was used as the test sample for this test example. The obtained test sample was uniform (dispersion state evaluation: good). The amount of stirring energy input was 422 kW·s / m 3 .

[0031] The obtained test sample was dried by blowing air at an ambient temperature of 100 °C for 4 hours to obtain a composite. Using a muffle furnace, the obtained composite was heat-reduced by holding it at 350 °C for 90 minutes under a nitrogen atmosphere to obtain a particulate material composed of a graphene inclusion porous particulate material.

[0032] Using a tableting machine, 10 mg of the obtained particulate material was pressed into a disk shape with a diameter of 5 mm and a thickness of 400 μm to form a zeolite separation membrane. The permeabilities of nitrogen and oxygen for the obtained zeolite separation membrane were measured.

[0033] The measurement of the permeability was as follows. The zeolite separation membrane formed on an acrylic pedestal with air holes was sealed by adhering it with a two-component curing epoxy resin. Then, the measurement gas (nitrogen gas or oxygen gas) was passed through and purged. Pressure was applied so that the gauge pressure on one side of the zeolite separation membrane became 20 kPa. Note that the gauge pressure on the other side was 0 kPa.

[0034] The time for the measurement gas to pass through 500 μL was measured with a soap film flowmeter, and the gas permeability was calculated from the membrane area, air temperature, and atmospheric pressure. The measurement was performed three times, and the average value was taken as the permeability of the measurement gas. The permeability of nitrogen gas was 3.6×10 -7 mol / m 2 Pa·s, and the permeability of oxygen gas was 2.7×10 -7 mol / m 2 Pa·s. Also, the separation factor calculated by (nitrogen gas permeability) / (oxygen gas permeability) was 1.3. The test conditions and evaluation results are shown in Table 1.

[0035] · Test Examples 6 to 9 Test Example 6 (stirring energy amount: 844 kW·s / m 3 ), Test Example 7 (stirring energy amount: 1688 kW·s / m 3 ), Test Example 8 (stirring energy amount: 2531 kW·s / m 3 ), Test Example 9 (stirring energy amount: 10125 kW·s / m 3 ). Except for these, the same operations as in Test Example 5 were performed to obtain test samples for each test example, and the same evaluation as in Test Example 5 was carried out. The results are shown in Table 1.

[0036]

Table 1

[0037] As is clear from the table, it was found that by changing the amount of stirring energy, the inclusion state of the complex of zeolite microcrystals and graphene oxide changes, and its properties also change. When the amount of stirring energy is 43 kW·s / m 3 In Test Examples 1 to 4 below, the inclusion state of zeolite microcrystals and graphene oxide was not sufficient.

[0038] When the amount of stirring energy is 43 kW·s / m 3 In Test Examples 5 to 9 exceeding this value, it was found that the zeolite microcrystals were included by graphene oxide and could be uniformly dispersed. From the results of Test Examples 5 to 9, as the amount of stirring energy increases, the permeabilities of nitrogen and oxygen decrease, but in Test Example 6 with the amount of stirring energy of 844 kW·s / m 3 has a maximum value in the separation factor, and it was found that the dispersion condition of 844 kW·s / m 3 of the stirring energy in Test Example 6 is preferable. Also, from the results of Test Example 9 with the amount of stirring energy increased to 10125 kW·s / m 3 it was suggested that there is an appropriate range for the amount of stirring energy.

Claims

1. A dispersion step of preparing a dispersion liquid as a composite by dispersing a porous particle material and graphene oxide in water; A reduction step of reducing the composite to obtain a graphene-encapsulated porous particle material; which has; The dispersion step is a method for producing a graphene-inclusion porous particle material having a stirring step of stirring a mixture of the porous particle material, the graphene oxide, and the water with a stirring blade under conditions of imparting a stirring energy amount of 200 to 6,000 (kW·s / m ３ ), to form the composite body.

2. The method for producing a graphene-encapsulated porous particle material according to Claim 1, wherein the porous particle material is selected from zeolite microcrystals, metal-organic frameworks, and mesoporous silica, and the volume average particle diameter thereof is 0.1 to 100 μm.

3. The method for producing a graphene-encapsulated porous particle material according to Claim 1, wherein the sum of the masses of the porous particle material and the graphene oxide is 0.01 to 10% based on the mass of the entire mixture.

4. The method for producing a graphene-encapsulated porous particle material according to Claim 1, wherein the reduction step is a step of reducing the dispersion liquid in which the composite obtained in the dispersion step is dispersed after vacuum drying or heat drying.

5. A method for producing a zeolite separation membrane having a graphene-encapsulated porous particle material generation step of obtaining a graphene-encapsulated porous particle material by the method for producing a graphene-encapsulated porous particle material according to any one of Claims 1 to 4.

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