KR102062865B1 - A gas separator and a method for manufacturing the same - Google Patents

Abstract

As one aspect of the present invention, provided are a manufacturing method of a gas separation membrane and a gas separation membrane manufactured thereby. The manufacturing method comprises the following steps: (a) mixing a first metal precursor, imidazole or imidazole derivatives, and a solvent to prepare solid particles; (b) mixing the solid particles, a second metal precursor, imidazole or imidazole derivative, and a solvent, heat-treating the same to grow crystals on a surface of the solid particles, and removing the solid particles to produce hollow particles; and (c) mixing the hollow particles and the polymer and molding the mixture. According to the present invention, the permeability and selectivity of the gas separation membrane can be realized in a balanced manner.

Description

GAS SEPARATOR AND A METHOD FOR MANUFACTURING THE SAME

The present invention relates to a gas separation membrane and a method for manufacturing the same, and more particularly, to an organic-inorganic composite gas separation membrane and a method for producing the same.

The accelerated use of fossil fuels and the development of natural gas are increasing the emissions of carbon dioxide, the culprit of the greenhouse effect. Accordingly, interest in carbon dioxide separation technology is also increasing.

Separation of carbon dioxide from carbon dioxide / methane mixtures in natural gas development is considered a very important process because acidic carbon dioxide can corrode the pipelines. Recently, the membrane technology has been spotlighted with high energy efficiency and low cost compared to the conventional separation technology of adsorption, absorption, and distillation. However, since the polymer membrane technology still has a problem in that the permeability and the selectivity are conflicted, many studies are being conducted to overcome this problem.

Among them, a mixed medium separator composed of an inorganic additive and an organic polymer matrix, that is, an organic-inorganic composite separator has emerged as a new type of gas separator. It is thought that the combination of a material having a high permeability with an appropriate polymer matrix can overcome the limitations of the polymer membrane. Various types of inorganic materials such as carbon nanotubes, zeolites, porous metal oxides, and metal organic structures (MOFs) may be used as additives. In particular, the metal organic structure is composed of organic ligands coordinated with metal ions and is highly applicable due to high surface area and intimacy with a specific gas.

However, when the interaction between the polymer matrix and the inorganic material is not sufficiently considered, there is a problem in that the pores of the separation membrane is uneven and structural stability is lowered, and the workability is reduced due to the inorganic material added during the manufacture of the separation membrane.

The present invention is to solve the above-mentioned problems of the prior art, an object of the present invention is to mitigate the trade-off characteristics between the permeability and selectivity of the gas separation membrane (gas separation membrane) which can implement them in a mutually balanced manner And to provide a method for producing the same.

One aspect of the invention, (a) mixing the first metal precursor, imidazole or imidazole derivatives, and a solvent to prepare a solid particle; (b) mixing the solid particles, the second metal precursor, the imidazole or the imidazole derivatives, and the solvent to grow crystals on the surface of the solid particles, and then removing the solid particles to prepare hollow particles; And (c) mixing and molding the hollow particles and the polymer.

In one embodiment, the first metal precursor is cobalt nitrate, cobalt acetate, cobalt chloride, cobalt sulfate, cobalt sulfate, cobalt bromide, cobalt iodide (cobalt iodine). cobalt iodide) and a combination of two or more thereof.

In one embodiment, the imidazole or imidazole derivatives are benzimidazole, 2-methylimidazole, 4-methylimidazole, 2-methylbenzimida 2-methylbenzimidazole, 2-nitroimidazole, 5-nitrobenzimidazole, 5-chlorobenzimidazole and combinations of two or more thereof It may be one selected from.

In one embodiment, the solid particles may be ZIF-67.

In one embodiment, the average particle size of the solid particles may be 100 ~ 500nm.

In one embodiment, the second metal precursor is zinc nitrate, zinc acetate, zinc chloride, zinc sulfate, zinc bromide, zinc iodide, and zinc iodide. zinc iodide) and a combination of two or more thereof.

In one embodiment, the hollow particles may be ZIF-8.

In one embodiment, the solvent is methanol, ethanol, propanol, iso-propanol, tert-butanol, n-butanol, methoxyethanol, ethoxyethanol, dimethylacetamide, dimethylformamide, n-methyl-2-pi It may be one selected from the group consisting of rolidone (NMP), formic acid, nitromethane, acetic acid, distilled water and a combination of two or more thereof.

In one embodiment, in the step (a), the first metal precursor and the imidazole or imidazole derivatives may be mixed in a weight ratio of 1: 1 to 5, respectively.

In one embodiment, in the step (b), the solid particles, the second metal precursor, and the imidazole or imidazole derivatives may be mixed in a weight ratio of 1: 1 to 5: 0.5 to 2, respectively.

In one embodiment, the heat treatment in the step (b) may be performed for 5 to 20 hours at 80 ~ 150 ℃.

In one embodiment, the step (c) may be wet mixing (wet mixing) the solution containing the hollow particles and the solution containing the polymer.

In one embodiment, the polymer may be an amphiphilic copolymer.

In one embodiment, the amphiphilic copolymer may be a graft copolymer of a hydrophobic polymer and a hydrophilic polymer.

In one embodiment, the amphiphilic copolymer may be synthesized by atomic transfer radical polymerization.

In one embodiment, the hydrophobic polymer is polyvinylchloride, polychlorotrifluoroethylene, polydichlorodifluoromethane, polyvinylidenechloride, polyvinylidene fluoride-co-chlorotrifluoroethylene and two of them It may be one selected from the group consisting of the above combination.

In one embodiment, the hydrophilic polymer is polyoxyethylene methacrylate, polyhydroxyethyl methacrylate, polyt-butyl methacrylate, polyacrylamide, polyN-vinylpyrrolidone, polyaminostyrene, polystyrene It may be one selected from the group consisting of sulfonic acid, polymethylpropenesulfonic acid, polysulfopropyl methacrylate, polysulfoethyl methacrylate, polysulfobutyl methacrylate, and a combination of two or more thereof.

Another aspect of the present invention provides a gas separation membrane prepared by the above method.

In one embodiment, the content of the hollow particles in the gas separation membrane may be 1 to 30% by weight.

In one embodiment, the gas separation membrane is measured using a differential method at 35 ℃ and 1bar, (i) the permeability of carbon dioxide is 50 Barrer or more, (ii) the permeability of carbon dioxide per methane may be 10 or more. .

Gas separation membrane according to an aspect of the present invention, by including a certain amount of polyhedral hollow particles to induce the necessary interaction between the polymer matrix and the hollow particles, thereby reducing the trade-off characteristics between the permeability and selectivity have.

In addition, the method of manufacturing a gas separation membrane according to an aspect of the present invention, through the solvent thermal synthesis method using a polyhedral solid particles as a template, it is possible to simply and easily produce a polyhedral hollow particles, it is used as a filler for the gas separation membrane As a result, the permeability and selectivity of the gas separation membrane may be balanced.

It is to be understood that the effects of the present invention are not limited to the above effects, and include all effects deduced from the configuration of the invention described in the detailed description or claims of the present invention.

1 is a diagram illustrating a manufacturing process and a gas separation membrane of H-ZIF according to an embodiment of the present invention;
2 is a photograph of a gas separation membrane according to Examples and Comparative Examples of the present invention;
Figure 3 is a SEM image (a), TEM image (b, c), H-ZIF particles and template (ZIF-67) of the XRD analysis results of the H-ZIF particles according to an embodiment of the present invention (d) and N ₂ physisorption isotherm (e);
4 is chemical structural formula (a) of PVC-g-POEM according to an embodiment of the present invention, and FT-IR analysis results of gas separation membranes according to Examples and Comparative Examples;
5 is a differential scanning calorimeter (DSC) analysis result of a gas separation membrane according to Examples and Comparative Examples of the present invention;
6 is an XRD analysis result of a gas separation membrane according to Examples and Comparative Examples of the present invention;
7 is a thermogravimetric analysis (TGA) analysis result of a gas separation membrane according to Examples and Comparative Examples of the present invention;
8 is an SEM image of the cross section of the gas separation membrane according to the Examples and Comparative Examples of the present invention;
9 shows gas permeability and carbon dioxide / methane permeability measurement results of gas separation membranes according to Examples and Comparative Examples of the present invention;
10 shows the relationship between the carbon dioxide permeability and the carbon dioxide / methane permeability of the gas separation membrane according to the examples and comparative examples of the present invention.

Hereinafter, with reference to the accompanying drawings will be described the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

Throughout the specification, when a part is "connected" to another part, it includes not only "directly connected" but also "indirectly connected" with another member in between. . In addition, when a part is said to "include" a certain component, this means that it may further include other components, without excluding the other components unless otherwise stated.

Manufacturing method of gas separation membrane

1 is a diagram illustrating a manufacturing process and a gas separation membrane of H-ZIF according to an embodiment of the present invention.

Referring to FIG. 1, an aspect of the present invention includes the steps of: (a) preparing a solid particle by mixing a first metal precursor, an imidazole or imidazole derivative, and a solvent; (b) mixing the solid particles, the second metal precursor, the imidazole or the imidazole derivatives, and the solvent to grow crystals on the surface of the solid particles, and then removing the solid particles to prepare hollow particles; And (c) mixing and molding the hollow particles and the polymer.

In step (a), the solid particles may be prepared by mixing the first metal precursor, imidazole or imidazole derivative, and a solvent.

The first metal precursor may be cobalt salt, for example, cobalt nitrate, cobalt acetate, cobalt chloride, cobalt chloride, cobalt sulfate, cobalt bromide, Cobalt iodide (cobalt iodide) and one selected from the group consisting of two or more thereof, preferably cobalt nitrate, more preferably cobalt nitrate hydrate, but is not limited thereto.

In addition, the imidazole or imidazole derivatives are benzimidazole, 2-methylimidazole, 4-methylimidazole, 2-methylbenzimidazole (2- methylbenzimidazole), 2-nitroimidazole, 5-nitrobenzimidazole, 5-chlorobenzimidazole and combinations of two or more thereof, Preferably, it may be 2-methylimidazole, but is not limited thereto.

In the step (a), the first metal precursor and the imidazole or imidazole derivatives may be mixed in a weight ratio of 1: 1 to 5, preferably, 1: 1.5 to 2.5, respectively. When the first metal precursor and the imidazole or imidazole derivative are cobalt nitrate hydrate and 2-methylimidazole, respectively, the solid particles synthesized in the step (a) may be ZIF-67. As used herein, the term "solid particles" means particles in which the interior of the particles is not empty and filled with solids and / or liquids. The average particle size of the solid particles may be 100 ~ 500nm, preferably, 200 ~ 300nm. When the average particle size of the solid particles is less than 100 nm, unnecessary aggregation may occur between the particles, and when the average particle size is more than 500 nm, the hollow particles may not be able to impart the required level of permeability to the gas separation membrane because it is difficult to structurally properly interact with the polymer matrix. .

The solvent is methanol, ethanol, propanol, iso-propanol, tert-butanol, n-butanol, methoxyethanol, ethoxyethanol, dimethylacetamide, dimethylformamide, n-methyl-2-pyrrolidone (NMP), Formic acid, nitromethane, acetic acid, distilled water, and one selected from the group consisting of two or more thereof, preferably, in consideration of the ease of commercial acquisition and affinity with the solute alcohol solvents methanol, ethanol, iso- Propanol, tert-butanol, or n-butanol may be used, and if necessary, a mixed solvent in which two or more of them are mixed may be used. In particular, methanol is advantageous because both zinc salts and imidazoles can be dissolved, and the boiling point is about 65 ° C., which allows vaporization without excessive heating of the reactor.

In step (b), the solid particles, the second metal precursor, imidazole or imidazole derivatives, and a solvent are mixed and heat treated to grow crystals on the surface of the solid particles, and then the solid particles are removed to obtain hollow particles. It can manufacture. That is, the solid particles synthesized in the step (a) are used as a mold for forming voids in the core portion of the hollow particles, and after the crystals are grown to the required level on the surface of the mold, Can be removed in a suitable way.

The second metal precursor is zinc nitrate, zinc acetate, zinc chloride, zinc sulfate, zinc sulfate, zinc bromide, zinc iodide, and zinc iodide. It may be one selected from the group consisting of two or more combinations, preferably zinc nitrate, more preferably zinc nitrate hydrate, but is not limited thereto.

In addition, the imidazole or imidazole derivatives are benzimidazole, 2-methylimidazole, 4-methylimidazole, 2-methylbenzimidazole (2- methylbenzimidazole), 2-nitroimidazole, 5-nitrobenzimidazole, 5-chlorobenzimidazole and combinations of two or more thereof, Preferably, it may be 2-methylimidazole, but is not limited thereto.

In step (b), the solid particles, the second metal precursor, and the imidazole or imidazole derivatives are respectively 1: 1 to 5: 0.5 to 2, preferably, 1: 2 to 4: 0.8 to 1.2. It can mix by weight ratio. When the solid particles, the second metal precursor, and the imidazole or imidazole derivatives are ZIF-67, zinc nitrate hydrate and 2-methylimidazole, respectively, the crystal grown on the surface of the solid particles may be ZIF-8. After the solid particles are removed, the ZIF-8 may exist as hollow particles having an empty space therein.

Zeolite imidazolate frameworks (ZIFs) have high thermal, chemical stability and unique structures and can be used as additives in gas separation membranes. The zeolite imidazolate structure generally consists of an imidazolate linker coordinated with transition metal ions and has a tetrahedral structure. The crystalline bonding angle between the metal ion of the zeolite imidazoleate structure and the imidazole linker is similar to that of 145 °, which is the Si-O-Si bonding angle of the zeolite, thus forming an isoform of zeolite. In particular, ZIF-8 particles, which are a type of zeolite imidazoleate structure, consist of zinc ions and 2-methylimidazole linkers, and are effective in gas separation membranes with a wide cage size (about 11ÅA) and pore sizes suitable for molecular sieve effect. Can be.

The heat treatment may be performed for 5 to 20 hours at 80 ~ 150 ℃. If the heat treatment condition is out of the above range, crystals may grow excessively, or conversely, the shell thickness of the hollow particles may be insufficient and the hollow particles may be easily destroyed.

In the step (c), a gas separation membrane may be obtained by mixing and molding the hollow particles and the polymer.

The polymer may be an amphiphilic copolymer. As used herein, the term "amphiphilic copolymer" refers to a copolymer having both a hydrophobic portion and a hydrophilic portion by using two or more units as structural units.

Since the hollow particles are hydrophilic, they may selectively and specifically interact with a hydrophilic portion of the amphiphilic copolymer to form an amphiphilic copolymer-hollow particle composite. Specifically, the hollow particles may increase the nanostructure unit size of the hydrophilic polymer and consequently increase the pore size and thus the gas permeability.

The amphiphilic copolymer may be a graft copolymer of a hydrophobic polymer and a hydrophilic polymer. In addition, the amphiphilic copolymer may be synthesized by an atomic transfer radical polymerization reaction.

The hydrophobic polymer is selected from the group consisting of polyvinyl chloride, polychlorotrifluoroethylene, polydichlorodifluoromethane, polyvinylidene chloride, polyvinylidene fluoride-co-chlorotrifluoroethylene, and combinations of two or more thereof. The selected one, preferably, may be polyvinyl chloride, but is not limited thereto.

The hydrophilic polymer is polyoxyethylene methacrylate, polyhydroxyethyl methacrylate, polyt-butyl methacrylate, polyacrylamide, polyN-vinylpyrrolidone, polyamino styrene, polystyrene sulfonic acid, polymethylpropene It may be one selected from the group consisting of sulfonic acid, polysulfopropyl methacrylate, polysulfoethyl methacrylate, polysulfobutyl methacrylate, and a combination of two or more thereof, preferably polyoxyethylene methacrylate, but It is not limited.

When the hydrophobic polymer and the hydrophilic polymer are polyvinyl chloride and polyoxyethylene methacrylate, respectively, the amphiphilic copolymer may be represented by the following Chemical Formula 1.

<Formula 1>

The weight ratio of the hydrophilic polymer and the hydrophobic polymer may be 1: 0.1-1, preferably 1: 0.2-0.5. When the proportion of the hydrophilic polymer is increased, the mechanical strength of the separator may be lowered due to expansion of the separator by water.

In addition, in the step (c), the solution containing the hollow particles and the solution containing the polymer may be wet mixed. Tetrahydrofuran may be used as the solvent in the solution, but is not limited thereto. In addition, the solution may be stirred or sonicated to improve the dispersibility of the hollow particles and the polymer in the solution. In addition, it is possible to secure the mechanical properties, uniformity of the gas separation membrane prepared by removing the bubbles remaining in the mixture by ultrasonic treatment of the mixture produced by the wet mixing.

Gas separation membrane

Another aspect of the present invention provides a gas separation membrane prepared by the above method.

The gas separation membrane may include a polymer matrix and polyhedral hollow particles including a plurality of pores. The hollow particles have good dispersibility in the polymer matrix due to the imidazole functional group and the hollow structure having good carbon dioxide affinity, and at the same time improve carbon dioxide separation performance.

The polymer matrix may be made of an amphiphilic copolymer, and the hollow particles may interact with a side chain made of a hydrophilic polymer in the amphiphilic copolymer. Specifically, the hollow particles may be fixed between side chains adjacent to each other to reduce the mobility and the degree of freedom of the side chains, thereby providing a space, that is, a pore or channel, through which carbon dioxide may selectively pass.

The content of the hollow particles in the gas separation membrane may be 1 to 30% by weight, preferably, 5 to 20% by weight, more preferably 10 to 20% by weight. If the content of the hollow particles is less than 1% by weight, the carbon dioxide permeability of the gas separation membrane may be lowered, and if it is more than 30% by weight, the mechanical properties of the gas separation membrane may be reduced.

The gas separation membrane may be measured using a differential method at 35 ° C. and 1 bar, and (i) the permeability of carbon dioxide is 50 Barrer or more, and (ii) the permeation selectivity of carbon dioxide to methane may be 10 or more. Preferably, the permeability of (i) carbon dioxide measured at the same conditions may be 200 Barrer or more, and (ii) the permeability of carbon dioxide to methane may be 11 or more. More preferably, the permeability of (i) carbon dioxide measured at the same conditions may be 210 Barrer or more, and (ii) the permeability of carbon dioxide to methane may be 14 or more.

Hereinafter, embodiments of the present invention will be described in detail.

The following experimental results were obtained from polyvinyl chloride (PVC) and polyoxyethylene methacrylate (POEM) as an amphiphilic copolymer polyvinylchloride-graft-polyoxyethylene methacrylate (polyvinylchloride-graft- polyoxyethylene methacrylate, PVC-g-POEM) and the amphiphilic copolymer and H-ZIF, a polyhedral hollow particle, are mixed to form a PVC-g-POEM / H-ZIF composite to make a gas separation membrane.

Example 1

1. Preparation of H-ZIF

ZIF-67 nanocrystals having a size of 200-300 nm to be used as a template were synthesized. Ligand and metal solutions were prepared by dissolving 9.75 g of 2-methylimidazole and 4.32 g of cobalt nitrate hexahydrate (Co (NO ₃ ) ₂ 6H ₂ O) in 300 mL of methanol. The two solutions were then stirred vigorously for 3 minutes, then vigorously aged at room temperature for 24 hours without stirring. The synthesized ZIF-67 nanocrystals were centrifuged three times at 7,000 rpm, sonicated in fresh methanol for 5 minutes, washed in vacuum at 12O &lt; 0 &gt; C for 12 hours and then used as a template for the synthesis of H-ZIF nanocrystals Used.

To synthesize H-ZIF nanocrystals, 0.1 g of the synthesized ZIF-67 nanocrystals were sonicated for 5 minutes and dispersed in 60 mL of methanol. Next, 0.372 g of zinc nitrate hexahydrate (Zn (NO ₃ ) ₂ 6H ₂ O) and 0.103 g of 2-methylimidazole were sequentially added to the ZIF-67 nanocrystal dispersion and stirred for 10 minutes. The mixture was subjected to solvent heat treatment at 100 ° C. for 12 hours in 100 ml autoclave lined with Teflon at 100 ° C., followed by washing and drying in the same protocol as for synthesizing ZIF-67 nanocrystals to prepare H-ZIF nanocrystals It was.

2. Manufacture of PVC-g-POEM

6 g of PVC was completely dissolved in 50 mL of NMP by stirring at 90 ° C. for 3 hours. After cooling the solution to room temperature, 24 mL of POEM (Mn = 475 g / mol), 0.1 g of copper (I) (CuCl) and 0.23 mL of HMTETA (1,1,4,7,10,10-hexamethyltriethylenetetramine) were added. . After purging with nitrogen gas for 1 hour, the mixture was placed in an oil bath. The polymerization reaction was carried out at 90 ° C. for 20 hours. After polymerization, the resulting mixture was diluted with tetrahydrofuran (THF) and passed through a column packed with activated Al ₂ O ₃ to remove the catalyst. The polymer was precipitated in methanol. To purify the final product, the precipitation was repeated three times and then the PVC-g-POEM copolymer was dried in vacuo at 50 ° C. to remove residual solvent.

3. Preparation of gas separation membrane

H-ZIF polyhedron nanocrystals were sonicated for 1 hour and dispersed in THF. Separately, the PVC-g-POEM copolymer was stirred vigorously at room temperature and dissolved in THF. Finally, the mixed solution was dispersed by sonication for 30 minutes so that the H-ZIF content was 5% by weight in the gas separation membrane to be prepared, and bubbles were removed. The PVC-g-POEM / H-ZIF solution was poured into a round Teflon dish and covered with perforated aluminum foil to control the evaporation rate. Membranes were prepared for 1 day at room temperature. The separator was separated from a Teflon dish and dried overnight in a vacuum oven to remove residual solvent to prepare a separator. Referring to FIG. 2, as the ratio of H-ZIF in the separator increases, the color of the separator changes from yellow to brown.

Example 2

A gas separation membrane was manufactured in the same manner as in Example 1, except that the H-ZIF content was adjusted to 10 wt% in the gas separation membrane.

Example 3

A gas separation membrane was manufactured in the same manner as in Example 1, except that the H-ZIF content was adjusted to 20 wt% in the gas separation membrane.

Comparative example

A gas separation membrane was prepared in the same manner as in Example 1 using only PVC-g-POEM without mixing H-ZIF and PVC-g-POEM.

Experimental Example 1

In order to analyze the surface area and porosity of H-ZIF particles, N ₂ adsorption-desorption was measured using a BELSORP-max device manufactured by MicrotracBEL.

Fourier-transform infrared spectroscopy (FT-IR) was used as the Excalibur series of DIGLAS Co., Hannover to evaluate the interaction between the polymer matrix and the H-ZIF additive.

Scanning electron microscope (SEM) used Carl Zeiss's Model MERLIN for nano-structure analysis of H-ZIF and gas separation membranes.

Differential scanning calorimetry (DSC) was used to evaluate the thermal characteristics of the gas separation membrane using a Perkin Elmer DSC8000 instrument, and the measurement was performed by raising the temperature to 10 ° C. per minute in a nitrogen environment.

XRD (X-ray diffraction) for analyzing the crystallinity of the gas separation membrane was used RINT2000 instrument of RIGAKU.

In order to measure the thermal stability of the gas separation membrane was used TA instruments DTA / TGA analyzer.

H-ZIF was synthesized by growing ZIF-8 in a heteroepitaxial structure on the surface of the ZIF-67 core. Referring to Figure 3, the structure and size of H-ZIF shows a rhombic dodecahedron structure similar to ZIF-67 used as a template, the size was observed 200 ~ 300nm. In addition, in the TEM photograph of FIG. 3, a hollow structure and a very thin outer wall (˜30 nm) were clearly observed. The crystal structure of H-ZIF in the XRD pattern of FIG. 3 is the same as that of ZIF-8, and the plate-shaped cobalt structure in the empty space of H-ZIF is the result of core etching of ZIF-67. Was formed.

In FIG. 4, FT-IR was used to examine the interaction between the PVC-g-POEM matrix and H-ZIF. In the H-ZIF particles C = N, CN and 1,584cm ^-1, 1,145cm ^-1, 421cm ^-1 band representing the Zn-N bond was observed, respectively. After mixing with PVC-g-POEM, the band position of H-ZIF did not change, but the intensity of the band increased as the amount added. ^-1 band and 1,097cm ^-1 band 1,725cm represents a carbonyl group (C = O) and ether (COC) present in the side chain POEM was observed strongly in the PVC-g-POEM. Each band shifted to a higher wavenumber following the introduction of H-ZIF. The band representing C = O shifted from 1,725 cm ⁻¹ to 1,728 cm ⁻¹ and the band representing COC moved from 1,096 cm ⁻¹ to 1,101 cm ⁻¹ . The shift to higher frequencies means that the length of the bonds is reduced, due to the interaction between H-ZIF and the polymer chain. The imidazole organic linker, which is coordinated to zinc metal ions, is believed to provide active sites for interacting with the carbonyl and ether groups of the POEM.

5 shows the thermal characteristics of the gas separation membrane. Referring to FIG. 5, the PVC-g-POEM branched polymer showed two glass transition temperatures (T _g ) at −61.2 ° C. and 95.8 ° C., respectively. Two glass transition temperatures were derived from the POEM side chain and the PVC main chain, respectively. These two glass transition temperatures indicate that PVC-g-POEM has a fine phase separation structure. This microphase separation structure is derived from the amphiphilic properties resulting from the difference in solubility between the hydrophilic POEM side chain and the hydrophobic PVC main chain. Such a fine phase separation structure is preferred for the gas separation membrane by forming a gas permeation passage in the polymer. As confirmed by FT-IR, hydrophilic POEM side chains can selectively interact with H-ZIF particles to form POEM / H-ZIF complexes. Fine composites composed of POEM side chains and H-ZIF, which have good affinity with carbon dioxide, can reduce carbon dioxide permeation resistance and contribute to higher carbon dioxide permeability and carbon dioxide / methane permeability. After the introduction of H-ZIF, the glass transition temperature of POEM side chain increased from -61.2 ℃ to -57.2 ℃. This is the result of the mobility and freedom of the POEM chain being hampered by the interaction of the POEM side chain with H-ZIF. On the other hand, the glass transition temperature of PVC main chain was constant regardless of the introduction of H-ZIF, and this result confirms the selective interaction between H-ZIF and PVC-g-POEM.

Referring to FIG. 6, the PVC-g-POEM branched polymer showed two broad amorphous peaks located at 18.9 ^o and 24.0 ^o due to fine phase separation. The d-spacing calculated using Bragg's law was calculated to be 4.7 Å of the POEM side chain and 3.7 PVC of the PVC main chain, respectively. In PVC-g-POEM / H-ZIF membranes, crystalline peaks of sharp H-ZIF are still observed, and the peaks gradually increase as the amount of H-ZIF added increases. This is because of the fact that it partially penetrates into the crystal structure. In the gas separation membrane of Comparative Example 1 to which 20 wt% of H-ZIF was added, it was observed that the relative intensity of the crystalline peak was changed (011). The intensity of the crystalline peaks decreased, whereas the intensity of the (002) and (013) crystalline peaks increased. This indicates that the structure of H-ZIF has been recrystallized due to the interaction of H-ZIF particles with rubbery POEM chains. In addition, as the amount of H-ZIF added increased, the intensity of the amorphous peak of PVC-g-POEM also decreased. This phenomenon can effectively prevent the formation of micro holes without selectivity between the polymer matrix and the filler, which is a disadvantage of the conventional composite separator. In other words, high gas separation performance can be expected by improving the physicochemical contact between the organic matrix and the inorganic filler in the process of the polymer chain penetrating into the H-ZIF recrystallization.

In addition, TGA equipment was used to confirm the thermal stability of the PVC-g-POEM branched polymer and gas separation membrane. Referring to FIG. 7, the gas separation membrane (comparative example) composed of pure PVC-g-POEM branched polymer did not show a significant mass reduction up to 250 ° C. due to high thermal stability. In the case of the gas separation membrane containing a certain amount of H-ZIF showed the same thermal stability, it was indirectly confirmed that the solvent was completely removed during the vacuum drying process in the manufacturing process of the membrane.

8 is an SEM image of a cross section of a gas separation membrane prepared according to Examples and Comparative Examples. Referring to FIG. 8, the pure PVC-g-POEM separator (comparative example) showed a uniform form without micro cracks. Gas separator containing a certain amount of H-ZIF In addition, H-ZIF particles were uniformly dispersed throughout the membrane, and the thickness of the membrane increased with increasing H-ZIF particle content. In preparing the gas separation membrane, clusters containing H-ZIF were not observed due to sufficient stirring and sonication. In addition, the microphase separation structure and the selective interaction between H-ZIF and the polymer also prevented aggregation of particles and improved interfacial contact. If the compatibility between the inorganic additives and the polymer matrix is low, an interface cavity without selectivity may be formed, and the selectivity of the separator may be greatly reduced.

Experimental Example 2

9 and Table 1 summarize the carbon dioxide permeability and the carbon dioxide / methane permeation selectivity of the mixed medium separation membranes prepared in Table 1 below.

division CH ₄ transmittance (barrer) CO ₂ permeability (barrer) Selectivity (CO ₂ / CH ₄ ) Comparative example 2.4 43.5 18.1 Example 1 3.0 51.7 17.2 Example 2 14.7 210.6 14.3 Example 3 18.9 224.7 11.9

The permeability of carbon dioxide in all gas separation membranes is much higher than that of methane. This is the result of the small kinetic diameter and high condensation of the carbon dioxide molecules. Pure PVC-g-POEM membrane showed CO2 permeability of about 43.5 Barrer and CO2 / methane permeability was calculated to be 18.1. The polar ether functional groups in the POEM side chain formed a dipole-quadrupole bond with the carbon dioxide molecule, indicating a relatively high carbon dioxide permeability. The carbon dioxide permeability of the gas separation membrane (Example 2) containing 10% by weight of H-ZIF particles was increased by about 484% from 43.5 Barrer to 210.6 Barrer.

Three factors contributed to this increase.

First, H-ZIF particles provide additional free volume in the membrane and also impede the packing between polymer chains, reducing gas permeation resistance, thereby increasing the permeability of carbon dioxide. In addition, the pore size of H-ZIF particles is about 3.4Å, which is larger than the size of CO2 (about 3.3Å), which helps in permeation of carbon dioxide, but larger gases may impede the flow, resulting in high permeability and selectivity. It was predicted.

Second, the imidazole linker of H-ZIF particles can quadrupole interact with carbon dioxide, and the amine functionality of the imidazole linker interacts with both carbon dioxide and the polymer matrix, which is highly effective in improving physical contact with the matrix as well as high carbon dioxide permeability. Helped.

Third, the internal structure of the hollow H-ZIF is dominated by the principle known as Knudsen diffusion, and this Knudsen diffusion is known to have a much higher value than diffusion in a polymer. Therefore, the more hollow pores, the more gas can pass through with less resistance.

In the case of methane, as the amount of H-ZIF increased, the permeability increased. This shows that although the size of methane (approximately 3.8 kPa is larger than the pore size of H-ZIF particles, some of the permeation is permeated by the relatively flexible structure of H-ZIF. The weight of the methane molecule is much lighter than that of the carbon dioxide molecule, which is inversely proportional to the molecular weight of the gas molecules, which is expected to diffuse methane faster than the carbon dioxide in the hollow space in the H-ZIF particles. Although the permeability of both carbon dioxide and methane increases, the advantages of H-ZIF and PVC-g-POEM mentioned above result in high CO2 permeability while maintaining a certain level of selectivity.

10 is a graph showing the relationship between carbon dioxide permeability and carbon dioxide / methane permeability. Due to the trade-off characteristics of the gas separation membrane, it is limited to simultaneously obtain high permeability and high selectivity. In general, the closer to the Robeson upper bound released in 2008, the better the performance than other separators. In the case of the separator prepared in Example, the selectivity was partially reduced, but the carbon dioxide permeability was greatly increased. It can be seen that the gas separation membrane of Example 2 is closer to the upper bound than the PVC-g-POEM separation membrane of the comparative example.

The foregoing description of the present invention is intended for illustration, and it will be understood by those skilled in the art that the present invention may be easily modified in other specific forms without changing the technical spirit or essential features of the present invention. will be. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive. For example, each component described as a single type may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined form.

The scope of the invention is indicated by the following claims, and it should be construed that all changes or modifications derived from the meaning and scope of the claims and their equivalents are included in the scope of the invention.

Claims (20)

In the manufacturing method of the gas separation membrane,
(a) mixing the first metal precursor, imidazole or imidazole derivative, and solvent to produce solid particles;
(b) mixing the solid particles, the second metal precursor, imidazole or imidazole derivatives, and a solvent to grow crystals on the surface of the solid particles, and then removing the solid particles to prepare hollow particles; And
(c) mixing and molding the hollow particles and the polymer;
The outer wall thickness of the hollow particles is 30nm or less,
The content of the hollow particles in the gas separation membrane is 10 to 30% by weight,
The gas separation membrane was measured using a differential method at 35 ° C. and 1 bar, and (i) the permeability of carbon dioxide was 200 Barrer or more, and (ii) the permeation selectivity of carbon dioxide to methane was 14 or more. The method of claim 1,
The first metal precursor is cobalt nitrate, cobalt acetate, cobalt chloride, cobalt chloride, cobalt sulfate, cobalt bromide, cobalt iodide and cobalt iodide Method for producing a gas separation membrane which is one selected from the group consisting of two or more combinations. The method of claim 1,
The imidazole or imidazole derivatives may be benzimidazole, 2-methylimidazole, 4-methylimidazole, 2-methylbenzimidazole, or 2-methylbenzimidazole. , A gas separation membrane selected from the group consisting of 2-nitroimidazole, 5-nitrobenzimidazole, 5-chlorobenzimidazole, and a combination of two or more thereof. Manufacturing method. The method of claim 1,
The solid particles are ZIF-67 manufacturing method of a gas separation membrane. The method of claim 4, wherein
The average particle size of the solid particles is a method of producing a gas separation membrane 100 ~ 500nm. The method of claim 1,
The second metal precursor is zinc nitrate, zinc acetate, zinc chloride, zinc sulfate, zinc sulfate, zinc bromide, zinc iodide, and zinc iodide. Method for producing a gas separation membrane which is one selected from the group consisting of two or more combinations. The method of claim 1,
The hollow particle is a method of producing a gas separation membrane of ZIF-8. The method of claim 1,
The solvent is methanol, ethanol, propanol, iso-propanol, tert-butanol, n-butanol, methoxyethanol, ethoxyethanol, dimethylacetamide, dimethylformamide, n-methyl-2-pyrrolidone (NMP), A method for producing a gas separation membrane, which is one selected from the group consisting of formic acid, nitromethane, acetic acid, distilled water and a combination of two or more thereof. The method of claim 1,
The method of claim 1, wherein the first metal precursor and the imidazole or imidazole derivative are mixed in a weight ratio of 1: 1 to 5, respectively. The method of claim 1,
In the step (b), the solid particles, the second metal precursor, and the imidazole or imidazole derivatives are mixed in a weight ratio of 1: 1 to 5: 0.5 to 2, respectively. The method of claim 1,
In the step (b), the heat treatment is a method of producing a gas separation membrane made for 5 to 20 hours at 80 ~ 150 ℃. The method of claim 1,
The method of manufacturing a gas separation membrane (wet mixing) of the solution containing the hollow particles and the solution containing the polymer in the step (c). The method of claim 1,
The polymer is a method of producing a gas separation membrane is an amphiphilic copolymer. The method of claim 13,
The amphiphilic copolymer is a graft copolymer of a hydrophobic polymer and a hydrophilic polymer. The method of claim 13,
The amphiphilic copolymer is a method of producing a gas separation membrane synthesized by an atomic transfer radical polymerization. The method of claim 14,
The hydrophobic polymer is selected from the group consisting of polyvinyl chloride, polychlorotrifluoroethylene, polydichlorodifluoromethane, polyvinylidene chloride, polyvinylidene fluoride-co-chlorotrifluoroethylene, and combinations of two or more thereof. Method for producing a gas separation membrane is one selected. The method of claim 14,
The hydrophilic polymer is polyoxyethylene methacrylate, polyhydroxyethyl methacrylate, polyt-butyl methacrylate, polyacrylamide, polyN-vinylpyrrolidone, polyamino styrene, polystyrene sulfonic acid, polymethylpropene A method for producing a gas separation membrane, which is selected from the group consisting of sulfonic acid, polysulfopropyl methacrylate, polysulfoethyl methacrylate, polysulfobutyl methacrylate, and a combination of two or more thereof. Made by the method according to any one of claims 1 to 17,
The outer wall thickness of the hollow particles is 30nm or less,
The content of the hollow particles in the gas separation membrane is 10 to 30% by weight,
The gas separation membrane was measured using a differential method at 35 ° C. and 1 bar, (i) the permeability of carbon dioxide is 200 Barrer or more, and (ii) the permeation selectivity of carbon dioxide to methane is 14 or more. delete delete

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