KR102233697B1 - Gas Separation Membrane and Method for Perparation thereof - Google Patents

Abstract

The present invention is a gas separation membrane comprising a substrate, and a hollow structure layer in which a plurality of hollow structures are stacked on the substrate, each of the hollow structures having a central hollow portion and a zeolite imidazolate skeleton layer surrounding the hollow portion, and the The present invention relates to a gas separation membrane with improved gas permeability and selectivity at the same time by including a polymer membrane coated on a zeolite imidazolate skeleton layer, and a method of manufacturing the same.

Description

Gas Separation Membrane and Method for Perparation thereof

The present invention relates to a gas separation membrane and a method for manufacturing the same, and more particularly, a zeolite imidazolate skeleton is formed in the form of a hollow structure, and a polymer having excellent gas separation properties is coated on the hollow structure to form a thin film to separate multiple layers. The present invention relates to a gas separation membrane and a method of manufacturing the same, which has the effect of improving gas permeability and selectivity at the same time.

In general, a desirable gas separation membrane material has properties that satisfy both gas permeability and selectivity. However, a typical high permeability polymer tends to have poor selectivity, and in the case of a high selectivity polymer, the transmittance decreases, so that there is a typical trade-off relationship between transmittance and selectivity. In addition, rigid glassy polymers such as polysulfone, polycarbonate, polyimide, and polypyrrole, which are widely used as gas separation membranes, have a narrow free volume distribution due to the dense chains. In the case of having a skeletal structure in the form of dense between the polymer chains, there is a disadvantage in that the permeability is limited while the selective separation of the gaseous molecule mixture is performed well (Non-Patent Document 1).

In order to increase the permeation selectivity of the polymer membrane, a mixed matrix membrane (MMM) is also prepared by introducing a porous filler. At this time, the filler uses a porous inorganic nanostructure to increase the permeability, and a general inorganic nanostructure has a high density and has a different surface characteristic from an organic material, so that the dispersion degree is low, resulting in a problem that gas permeability and selectivity are reduced.

The most commonly used porous filler is a metal-organic framework (MOF), which has small pores of several Å, so it is easy to separate a specific gas, and the permeability can be increased due to the pores of the MOF. However, for example, in Yichao Lin et al.'s Amine-functionalized metal.organic frameworks: structure, synthesis and applications, RSC Adv., 2016, 32598-32614, there is a technique for separating carbon dioxide using a metal organic framework having an amine group. Although described, there is a problem that satisfactory selectivity or transmittance results have not been obtained so far.

In the case of a ceramic separator, it is manufactured as a thin film on a support, and when it is manufactured as a thick film, the permeation is greatly reduced, and defects in the separator are easily generated due to the characteristics of a ceramic that is brittle, and thus there is a problem that performance decreases.

In addition, in addition to the separation membrane using MOF, U.S. Patent No. 4,762,543 discloses a variety of polymer composite membranes, and as an example, a technology using a polymer membrane is known, but in order to use it, a low temperature must always be maintained, and selectivity for carbon dioxide It is low and there is a problem in commercialization.

U.S. Patent No. 5,049,167 discloses a method of increasing the selectivity of carbon dioxide/hydrogen by interfacial polymerization of polyamide on a polymer composite membrane again, but this also has a disadvantage in that the transmittance and selectivity are not sufficient for commercialization.

[Patent Document 1] International Publication Patent WO 2015/133848 A1 [Patent Document 2] US Patent No. 4,762,543 [Patent Document 3] US Patent No. 5,049,167

[Non-Patent Document 1] L. M. Robeson et al., J. Membr. Sci. 62, 165-185 (1991) [Non-Patent Document 2] Liang Chen et al., Amine-functionalized metal.organic frameworks: structure, synthesis and applications, RSC Adv., 2016, 32598-32614

The present invention was conceived to solve the problems of the prior art as described above, and an object of the present invention is to prepare a porous film including a multilayered hollow structure layer using a zeolite imidazolate skeleton, It is to provide a method of manufacturing a gas separation membrane that simultaneously improves gas permeability and selectivity by coating a polymer membrane.

In addition, it is an object of the present invention in a gas separation membrane comprising a hollow structure layer in which a plurality of hollow structures are stacked on a substrate, each of the hollow structures has a central hollow portion and a zeolite imidazolate skeleton layer surrounding the hollow portion, and the It is to provide a gas separation membrane with improved gas permeability and selectivity at the same time by including a polymer membrane coated on a zeolite imidazolate skeleton layer.

The method of manufacturing a gas separation membrane according to the present invention for achieving the above object may include the following steps:

1) laminating polystyrene beads on a substrate to prepare a polystyrene multilayer film in which a multilayer polystyrene bead layer is laminated on the substrate;

2) forming a zinc oxide layer on each of the polystyrene beads included in the polystyrene beads layer of the polystyrene multilayer film obtained in step 1);

3) sintering the polystyrene multilayer film on which the zinc oxide layer obtained in step 2) is formed to remove polystyrene beads to obtain a porous metal oxide film;

4) reacting the porous metal oxide film obtained in step 3) with an imidazole solution to obtain a porous film in which each zinc oxide layer is converted into a zeolite imidazolate skeleton layer; And

5) coating a polymer film on each zeolite imidazolate skeleton by immersing the porous film obtained in step 4) in a polymer solution.

In step 1), the substrate may be a porous alumina substrate or a porous zirconium substrate.

In the step 1), the polystyrene beads may be surface-treated with a carboxyl group.

In the step 1), the lamination of the polystyrene beads on the substrate may be performed by drying after supporting the substrate in a dispersion of polystyrene beads.

In the step 2), the zinc oxide layer may be formed by coating a zinc nitride solution on a polystyrene multilayer film and drying it.

The zinc nitride compound contained in the zinc nitride solution may be zinc nitride hexahydrate.

In step 3), the sintering may be performed at 400 to 700° C. for 30 minutes to 3 hours.

The process of reacting with the imidazole solution in step 4) may be performed by immersing the imidazole solution at 50 to 100° C. for 10 to 30 hours.

In step 4), the imidazole compound contained in the imidazole solution may be 2-methylimidazole.

In step 5), the polymer contained in the polymer solution may be one or more selected from the group consisting of polyimide (PI), polydimethylsiloxane (PDMS), polyethylene oxide, and polyether blockamide.

In addition, the present invention is a gas separation membrane manufactured by the method of manufacturing a gas separation membrane according to the present invention, and comprising a substrate and a hollow structure layer in which a plurality of hollow structures are stacked on the substrate,

Each of the hollow structures may provide a gas separation membrane including a central hollow portion, a zeolite imidazolate skeleton layer surrounding the hollow portion, and a polymer membrane coated on the zeolite imidazolate skeleton layer.

According to the method of manufacturing a gas separation membrane according to the present invention, a zeolite imidazolate skeleton is formed in the form of a hollow structure using polystyrene beads and a zeolite imidazolate skeleton, which is a macro-porous nanofiller, and pores in the separation membrane. By forming a porous filler in the form of a hollow sphere, it is possible to solve the problem of being easily broken during the mixing process and increase the permeability, and to form a thin film by coating a polymer having excellent gas separation characteristics on the hollow structure. It has the effect of separating and improves gas permeability and selectivity at the same time.

In addition, according to the manufacturing method of the gas separation membrane according to the present invention, the zeolite imidazolate skeleton layer can be easily manufactured in a larger area, and the polystyrene beads are dissolved and removed by removing the polystyrene beads through high-temperature firing. It has an effect that can be removed more easily.

1 is a schematic diagram showing the manufacturing process of the gas separation membrane of the present invention.
2 is a scanning electron microscope (SEM) photograph of the polystyrene multilayer film of Example 1. FIG.
3 is a graph showing the results of X-ray diffraction analysis (XRD) of the crystal structure of the zeolite imidazolate skeleton of Example 1. FIG.
4 is a scanning electron microscope (SEM) photograph of the gas separation membrane of Example 1. FIG.

Advantages and features of the present invention, and a method of achieving them will become apparent with reference to specific examples described below in detail together with the accompanying drawings. However, the present invention is not limited to the specific examples disclosed below, but may be implemented in a variety of different forms, and only the specific examples of the present invention make the disclosure of the present invention complete, and are generally used in the technical field to which the present invention pertains. It is provided to completely inform the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims.

Unless otherwise defined, all terms (including technical and scientific terms) used in the present specification may be used with meanings that can be commonly understood by those of ordinary skill in the art to which the present invention belongs. In addition, terms defined in a commonly used dictionary are not interpreted ideally or excessively unless explicitly defined specifically.

Hereinafter, a gas separation membrane and a method of manufacturing the same according to the present invention will be described in detail.

The method of manufacturing a gas separation membrane according to the present invention may include the following steps:

1) laminating polystyrene beads on a substrate to prepare a polystyrene multilayer film in which a multilayer polystyrene bead layer is laminated on the substrate;

2) forming a zinc oxide layer on each polystyrene beads by immersing the polystyrene multilayer film obtained in step 1) in a zinc nitride solution;

3) sintering the polystyrene multilayer film on which the zinc oxide layer obtained in step 2) is formed to remove polystyrene beads to obtain a porous film;

4) reacting the porous film obtained in step 3) with an imidazole solution to obtain a porous film in which each zinc oxide layer is converted to a zeolite imidazolate skeleton layer; And

5) coating a polymer film on each zeolite imidazolate skeleton of the porous film obtained in step 4).

In the step 1), the polystyrene beads may be surface-treated with a carboxyl group. Typically, the primary growth of the zeolite imidazolate skeleton on the surface of the polystyrene beads, as well as the secondary and tertiary growth of the zeolite imidazolate skeleton on the already existing zeolite imidazolate skeleton are present on the polystyrene bead particle surface. It is initiated by a coordination interaction between a carboxylate group and a metal ion. The metal-ligand coordination interaction over the entire surface of the polystyrene beads particles leads to uniform growth of the zeolite imidazolate skeleton, and results in the formation of an even zeolite imidazolate skeleton layer on the polystyrene beads particle surface.

In step 1), the lamination of the polystyrene beads on the substrate is not particularly limited, but may be carried out by drying after supporting the substrate in a dispersion of polystyrene beads. For example, after supporting the substrate at an angle in a polystyrene bead dispersion of 0.05 to 0.5% by weight, preferably about 0.1% by weight, the polystyrene beads dispersion is added in an oven at 50 to 80°C, preferably about 60 to 70°C. By drying, it is possible to prepare a polystyrene multilayer film in which a polystyrene bead layer is laminated.

The substrate is not particularly limited as long as it is a substrate used for a gas separation membrane, and may be, for example, a porous alumina substrate or a porous zirconium substrate.

In the step 2), the zinc oxide layer may be formed by coating a zinc nitride solution on a polystyrene multilayer film and drying it. For example, 1 to 10% by weight, preferably 3 to 7% by weight, most preferably 5% by weight of zinc nitride solution is coated so as to completely cover the top of the polystyrene multilayer film, followed by drying 3 to 7 times. , Preferably, it can be carried out by repeating 5 times. In the case of coating a zinc nitride solution, the number of times to be performed may vary depending on the amount of the solution to be dropped, and it is necessary to repeatedly coat until the zinc oxide layer is completely formed. When coating less than 3 times, the zinc oxide layer is not completely formed, and when coating more than 7 times, the film surface is densely coated and the transmittance is rapidly decreased, which is not preferable.

The zinc nitride compound contained in the zinc nitride solution may be zinc nitride hexahydrate.

The zinc nitride compound solution may be a solution containing 3 to 7% by weight, preferably 5% by weight of zinc nitride in a solvent, and if the concentration of zinc nitride is less than the above range, the number of coatings must be increased, which is inefficient. When the concentration range is exceeded, a coating layer is formed on the polystyrene multilayer film, and the pores of the film are not completely coated, which is not preferable.

In the step 3), the sintering may be carried out at 400 to 700°C, preferably at 500 to 600°C, for 30 minutes to 3 hours, preferably 1 to 2 hours, and if it is less than the range of the firing conditions, polystyrene The beads are not completely removed, and when the above firing conditions are exceeded, energy consumption increases, which is not efficient, and a phenomenon in which the zinc metal melts may occur, which is not preferable.

The process of reacting with the imidazole solution in step 4) may be performed by immersing the imidazole solution at 50 to 100°C, preferably 60 to 80°C, for 10 to 30 hours, preferably 15 to 24 hours, Outside of the above condition range, the crystal structure is not sufficiently formed or too long time is consumed, which is not preferable.

By the reaction in step 4) above, when zinc oxide reacts with the imidazole solution at high temperature, the structure of zinc oxide changes to ZIF on the zinc oxide surface.At this time, this reaction is a surface reaction that occurs on the surface and does not occur to the inside of the particles. Will not be. Therefore, in the case of a particle having a size of several hundred nanometers, only the surface is changed to ZIF having a porous structure, and the inside forms a dense oxide structure. Since the dense structure reduces gas permeability, a zinc oxide film layer having a thin porous frame is formed by the above reaction, and when it is converted to ZIF, a ZIF film having a structure having a very high conversion rate can be manufactured.

In step 4), the imidazole compound contained in the imidazole solution may be an alkylimidazole compound, particularly 2-methylimidazole.

The imidazole solution may be a solution containing 2 to 8% by weight, preferably 4 to 6% by weight, most preferably 5% by weight of an imidazole compound in a solvent, and if it is less than the concentration range, the crystal structure is It is not formed well, and an overconcentration higher than the above concentration range is unnecessary in terms of process and economy.

The solvent used for the zinc nitride solution and the imidazole solution is not particularly limited, and for example, may be at least one selected from the group consisting of alcohol-based solvents such as ethanol, methanol, and isopropyl alcohol (IPA). It may be methanol.

In step 5), the polymer contained in the polymer solution is used to improve selectivity by filling defects in the zeolite imidazolate skeleton layer, and to improve gas permeability by not completely filling the macropores when filling the defects. As a polymer, the polymer is not particularly limited, and for example, may be one or more selected from the group consisting of polyimide, polydimethylsiloxane (PDMS), polyethylene oxide, and polyether blockamide, preferably polyether blockamide. Can be

The coating in step 5) is not particularly limited, and may be performed through, for example, spin coating or dip coating, and the thickness of the coated polymer film is in terms of enabling coating without defects, for example It is desirable to control the coating to be 1 μm or less, preferably about 200 nm to 1 μm.

For example, in the coating in step 5), a polymer solution of 0.5 to 1% by weight is applied 2 to 3 times of spin coating under the conditions of 1000 to 3000 rpm, preferably 2000 rpm for 10 to 30 seconds, preferably about 20 seconds. It can be done through.

In addition, the present invention is a gas separation membrane manufactured by the method of manufacturing a gas separation membrane according to the present invention, and comprising a substrate and a hollow structure layer in which a plurality of hollow structures are stacked on the substrate,

Each of the hollow structures may provide a gas separation membrane including a central hollow portion, a zeolite imidazolate skeleton layer surrounding the hollow portion, and a polymer membrane coated on the zeolite imidazolate skeleton layer.

The thickness of the gas separation film may be 500nm to 2㎛. If the thickness of the gas separation membrane is less than 500 nm, it is not effective in improving the gas separation performance, and defects are easily generated during manufacturing. Also, defects in the membrane due to external impact are likely to occur. If the thickness of the gas separation membrane exceeds 2 μm, the permeability can be rapidly reduced. Not desirable.

The gas separation membrane according to the present invention can increase the permeability by forming pores in the separation membrane by using the zeolite imidazolate skeleton, which is a macro-porous nanofiller, and the zeolite imidazolate skeleton is formed in the form of a hollow structure. In addition, a polymer having excellent gas separation properties is coated on the hollow structure to form a thin film to form a multi-layer separation, thereby improving gas permeability and selectivity at the same time.

Hereinafter, specific contents of the present invention will be described in detail through the following examples, but this is for illustrative purposes of the present invention and is not intended to limit the scope of protection defined by the appended claims.

Example 1 and Comparative example One

[material]

Styrene monomer, methacrylic acid, sodium hydroxide, sodium carbonate, potassium persulfate, zinc nitrate hexahydrate, 2-methylimidazole used in Example 1 below , Methanol, ethanol, and tetrahydrofuran were purchased from Sigma-Aldrich, and polyether blockamide (PEBAX-1657) was purchased from Arkema Inc. All reagents were used without purification.

Example One

Polystyrene beads surface-treated with a carboxyl group were synthesized as follows.

In 80 ml of distilled water, 7.6 ml of styrene monomer and 0.35 ml of methacrylic acid were mixed, followed by purging with nitrogen for 30 minutes to remove oxygen from the inside. Thereafter, 0.024 g of sodium hydroxide and 0.024 g of sodium carbonate were added, followed by purging with nitrogen for another 10 minutes. 0.03 g of potassium persulfide was added to the solution and reacted at 75° C. for 12 hours while purging with nitrogen to prepare a dispersion of polystyrene beads surface-treated with a carboxyl group. The prepared polystyrene beads had a particle diameter of about 300 to 500 nm.

Then, the polystyrene beads dispersion prepared above was diluted 0.1% by weight with distilled water, and then the porous alumina substrate was obliquely supported in the polystyrene beads dispersion, and the dispersion was dried in an oven at 60° C., and a multilayer of polystyrene well laminated on the alumina substrate. A film was prepared, and a scanning electron microscope (SEM) photograph of the polystyrene multilayer film is shown in FIG. 2.

Then, according to the process of FIG. 1, the polystyrene multilayer film was immersed in a 1 wt% zinc nitride hexahydrate solution in methanol at 70° C. for 10 minutes to form a zinc oxide layer on each polystyrene beads. Then, it was baked at 500° C. for 1 hour to remove polystyrene beads to obtain a porous film. Subsequently, the porous film was immersed in a 5% by weight solution of 2-methylimidazole in methanol at 70° C. for 24 hours to convert each zinc oxide layer into a zeolite imidazolate skeleton layer, and the zeolite imidazolate skeleton The results of X-ray diffraction analysis showing the crystal structure of the sieve are shown in FIG. 3.

Then, 0.5% by weight of PEBAX-1657 was coated on the obtained porous film several times to prepare a gas separation membrane coated with a polymer membrane on each zeolite imidazolate skeleton, and a scanning electron microscope (SEM) of the gas separation membrane A photograph is shown in FIG. 4, and the permeability and selectivity of the gas separation membrane were measured, and the results are shown in Table 1 below.

Comparative example One

A gas separation membrane was prepared using pure PEBAX-1657 resin, and the permeability and selectivity of the gas separation membrane were measured, and the results are shown in Table 1 below.

Comparative example 2

A solution of 3% by weight zinc nitride hexahydrate in methanol and a solution of 6% by weight 2-methylimidazole in methanol were mixed, reacted at room temperature for 24 hours, and then centrifuged to obtain ZIF-8 powder. The prepared ZIF-8 was washed several times with an excess of methanol and dried at 150° C. for 12 hours. A PEBAX-1657/ZIF-8 solution was prepared by dispersing the prepared ZIF-8 in a 5% by weight PEBAX-1657 solution in an amount of 20% by weight based on the solid content. The prepared solution was cast on a substrate and dried to prepare a PEBAX-1657/ZIF-8 separator.

Transmittance (barrier ⁾ ) Selectivity (CO ₂ /N ₂ ) Example 1 140 28 Comparative Example 1 90 25 Comparative Example 2 100 28

Note) Carbon dioxide permeability and carbon dioxide permeation selectivity are measured for a mixture of pure carbon dioxide and nitrogen under the conditions of 800mmHg and 35℃ using the time-rack method.

As shown in Table 1 above, the gas separation membrane of Example 1 exhibited a carbon dioxide permeability of 140 barrier and a carbon dioxide permeation selectivity of 28, which was significantly improved compared to the carbon dioxide permeability and carbon dioxide permeation selectivity of the gas separation membranes of Comparative Examples 1 and 2. You can see that it is.

In general, as the permeability increases, the selectivity decreases. It can be seen that the gas separation membrane according to the present invention also increases the selectivity as well as the permeability.

Claims (11)

A method of manufacturing a gas separation membrane comprising the following steps:
1) laminating polystyrene beads on a substrate to prepare a polystyrene multilayer film in which a multilayer polystyrene bead layer is laminated on the substrate;
2) forming a zinc oxide layer on each of the polystyrene beads included in the polystyrene beads layer of the polystyrene multilayer film obtained in step 1);
3) sintering the polystyrene multilayer film on which the zinc oxide layer obtained in step 2) is formed to remove polystyrene beads to obtain a porous metal oxide film;
4) reacting the porous metal oxide film obtained in step 3) with an imidazole solution to obtain a porous film in which each zinc oxide layer is converted into a zeolite imidazolate skeleton layer; And
5) coating a polymer film on each zeolite imidazolate skeleton by immersing the porous film obtained in step 4) in a polymer solution. The method of claim 1,
In step 1), the substrate is a porous alumina substrate or a porous zirconium substrate. The method of claim 1,
In the step 1), the polystyrene beads are surface-treated with a carboxyl group. The method of claim 1,
In the step 1), the lamination of the polystyrene beads on the substrate is performed by supporting the substrate in a dispersion of polystyrene beads and then drying it. The method of claim 1,
In the step 2), the zinc oxide layer is formed by coating a zinc nitride solution on a polystyrene multilayer film, followed by drying. The method of claim 5,
The zinc nitride compound contained in the zinc nitride solution is zinc nitride hexahydrate. The method of claim 1,
In step 3), the sintering is performed at 400 to 700° C. for 30 minutes to 3 hours. The method of claim 1,
The process of reacting with the imidazole solution in step 4) is performed by immersing the imidazole solution at 50 to 100° C. for 10 to 30 hours. The method of claim 1,
In step 4), the imidazole compound contained in the imidazole solution is 2-methylimidazole. The method of claim 1,
In step 5), the polymer contained in the polymer solution is at least one selected from the group consisting of polyimide, polydimethylsiloxane, and polyether blockamide. A gas separation membrane manufactured by the method for manufacturing a gas separation membrane according to any one of claims 1 to 10 and comprising a substrate and a hollow structure layer in which a plurality of hollow structures are stacked on the substrate,
Each of the hollow structures includes a central hollow portion, a zeolite imidazolate skeleton layer surrounding the hollow portion, and a polymer membrane coated on the zeolite imidazolate skeleton layer.

Images