Co2 separation membrane and co2 separation element

Abstract

A CO2 separation membrane 22 separates CO2 in air in an indoor environment. A hydrophilic polymer layer 102 includes an amino acid having an amino group and being a CO2 carrier, and an aggregation inhibitor for suppressing aggregation of amino acid. A first porous film 100 carries the hydrophilic polymer layer 102. The aggregation inhibitor contains an alkali metal element. In the hydrophilic polymer layer 102, the substance amount of the alkali metal element is greater than the substance amount of the amino group.

Description

CO2 separation membrane, CO2 separation element

[0001] The present disclosure provides a method for converting CO ２ CO ２ Separation membrane, CO ２ Regarding the separation element.

[0002] CO ２ CO separation materials ２ The separation element can be used to, for example, remove carbon dioxide from a gas containing hydrogen to increase the purity of hydrogen, or to remove CO from the atmosphere. ２ Remove CO ２ It is expected that this will contribute to reducing CO2 emissions (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2000-229219

[0004] CO ２ CO separation membrane ２ When performing the separation, CO ２ Due to the characteristics of the separation membrane, CO ２ Separation is performed in a low humidity environment. ２ This process has higher separation performance than conventional separation. This is a process mainly used in factories. For example, in the hydrogen process where carbon dioxide is removed from hydrogen-containing gas to increase the hydrogen purity, CO is removed in a high-temperature environment of 100°C or higher. ２ A sufficient amount of water vapor is supplied to the separation membrane.

[0005] On the other hand, the inventors have ２ Using a separation membrane, CO ２ Separation of indoor CO2 in homes and offices ２ Generally, indoor temperatures where people are active are below 40°C, and unless a humidifying means is used, the humidity is relatively lower than in the case of the hydrogen process. ２ When the separation element is operated, CO ２ When the water content in the separation membrane decreases, amino acids essential for the facilitated transport mechanism precipitate as aggregates, resulting in a decrease in separation performance.

[0006] The present disclosure has been made to solve the above problems, and２ The object of the present invention is to provide a technology for suppressing the precipitation of amino acids in a separation membrane.

[0007] In order to solve the above problems, a CO ２ The separation membrane can separate CO from the air in an indoor environment. ２ CO ２ In the separation membrane, a CO ２ The hydrophilic polymer layer includes an amino acid as a carrier and an aggregation inhibitor that inhibits aggregation of the amino acid, and a porous membrane that supports the hydrophilic polymer layer. The aggregation inhibitor contains an alkali metal element. The amount of the alkali metal element is greater than the amount of the amino group in the hydrophilic polymer layer.

[0008] According to the present disclosure, CO ２ The precipitation of amino acids in the separation membrane can be suppressed.

[0009] FIG. 1 shows a CO ２ 2(a)-(b) are schematic diagrams showing an example of the installation of a separation system. ２ 3 is a diagram showing an outline of a separation element. ２ 4 is a perspective view showing a laminated structure used as a separation element. ２ 5 is a cross-sectional view showing a schematic structure of a separation membrane. ２ 1 is a flowchart showing the procedure for producing a separation membrane. ２ Permeance, CO ２ / N ２ 7(a) and 7(b) are diagrams showing the surfaces of Example 1 and Comparative Example 1 in FIG. 6, comparing the presence or absence of aggregation.

[0010] Hereinafter, embodiments will be described with reference to the drawings. Note that the following embodiments are examples that embody the present disclosure and do not limit the technical scope of the present disclosure. Furthermore, each drawing described in the embodiments is a schematic drawing, and the ratios of the sizes and thicknesses of the components in each drawing do not necessarily reflect the actual dimensional ratios.

[0011] Embodiments of the present disclosure will be described with reference to the accompanying drawings. ２ 1 is a schematic diagram showing an example of installation of a separation system 1. In a building 2 such as a house, CO ２ Separation system 1 is installed. ２ The separation system 1 separates a target gas (e.g., CO ２ It is a device that removes CO ２ The separation system 1 includes a housing 10, a CO ２ It includes a separation element 20, an inside air fan 31, an inside air filter 37, an outside air fan 41, an outside air filter 47, a first temperature control unit 4a, a second temperature control unit 4b collectively referred to as the temperature control unit 4, a control unit 5, an outside air temperature detection unit 7, and an inside air temperature detection unit 8.

[0012] The housing 10 is ２ The housing 10 is an outer frame of the separation system 1. An internal air port 33, an air intake port 35, an external air port 43, and an exhaust port 45 are arranged on the outer periphery of the housing 10. The internal air port 33 is used to introduce air 39a into the CO ２ The indoor air inlet 33 is an intake port that draws air into the separation system 1. The indoor air inlet 33 is connected to an indoor air inlet 51 provided in the building 2 by an indoor air introduction duct 52. The indoor air inlet 51 is an opening provided in the target space of the building 2, and is used to collect air 39a (indoor air) in the target space as RA and CO ２ The inside air intake duct 52 is an opening through which air is introduced into the separation system 1. The inside air intake duct 52 is a duct that introduces inside air into the housing 10. One end of the inside air intake duct 52 is connected to the indoor air inlet 51, and RA from indoors flows into the inside air intake duct 52. The other end of the inside air intake duct 52 is connected to the inside air port 33, and RA is circulated inside the housing 10. In other words, air from a target space indoors is introduced into the inside air intake duct 52 as inside air and circulates therethrough.

[0013] The air inlet 35 is used to supply air 39b to CO ２ The air supply port 35 is an outlet for discharging air from the separation system 1. The air supply port 35 is connected to an indoor air outlet 53 provided in the building 2 by an indoor air outlet duct 54. The indoor air outlet 53 is an opening provided in the building 2, and ２ The separation element 20 ２The inside air outlet duct 54 is an opening that supplies the air 39b with reduced concentration to the target space as SA. The inside air outlet duct 54 is a duct that supplies the inside air from the housing 10 to the target space. One end of the inside air outlet duct 54 is connected to the air intake port 35, and the CO ２ The separation element 20 ２ The air 39b with reduced concentration flows into the duct. The other end of the inside air outlet duct 54 is connected to the indoor outlet 53, and the air 39b in the duct is supplied to the target space as SA. In other words, the inside air outlet duct 54 returns the air 39b to the target space.

[0014] The outside air port 43 is for introducing air 49a into the CO ２ The outdoor air inlet 43 is an intake port that draws in the air into the separation system 1. The outdoor air inlet 43 is connected to an outdoor air inlet 55 provided in the building 2 by an outdoor air introduction duct 56. The outdoor air inlet 55 is an opening provided in the building 2, and is used to introduce outdoor air 49a (outside air) as OA and CO ２ The outside air intake duct 56 is an opening through which outside air is introduced into the separation system 1. The outside air intake duct 56 is a duct that introduces outside air into the housing 10. One end of the outside air intake duct 56 is connected to the outdoor air inlet 55, and OA from outside flows into the outside air intake duct 56. The other end of the outside air intake duct 56 is connected to the outdoor air port 43, and OA is circulated inside the housing 10. In other words, outdoor air is introduced into the outside air intake duct 56 as outside air and circulates therethrough.

[0015] The exhaust port 45 exhausts the air 49b to the CO ２ The exhaust port 45 is an outlet that discharges CO 2 from the separation system 1 to the outdoors. The exhaust port 45 is connected to an outdoor outlet 57 provided in the building 2 by an outdoor air outlet duct 58. The outdoor outlet 57 is an opening provided in the building 2, and ２ The separation element 20 ２ The outside air outlet duct 58 is an opening for discharging the air 49b with increased concentration to the outside as EA. The outside air outlet duct 58 is a duct for supplying outside air from the housing 10 to the outside. One end of the outside air outlet duct 58 is connected to the exhaust port 45, and the CO ２ The separation element 20 ２The air 49b with increased concentration flows into the duct. The other end of the outside air outlet duct 58 is connected to the outdoor outlet 57, and the air 49b in the duct is discharged to the outdoors as EA. In other words, the outside air outlet duct 58 releases the air 49b to the outdoors.

[0016] Hereinafter, air 39a and air 39b may be collectively referred to as "indoor air," and air 49a and air 49b may be collectively referred to as "outdoor air." Furthermore, indoor air introduction duct 52 and indoor air outlet duct 54 may be collectively referred to as an "indoor air duct," and outdoor air introduction duct 56 and outdoor air outlet duct 58 may be collectively referred to as an "outdoor air duct."

[0017] Here, the diameter of each duct will be described. In this embodiment, the duct diameter of the outside air introduction duct 56 and the outside air outlet duct 58 through which the outside air is ventilated is smaller than the duct diameter of the inside air introduction duct 52 and the inside air outlet duct 54 through which the inside air is ventilated. This is because ２ This is because the flow rate of outside air circulating through the separation system 1 is made smaller than the flow rate of inside air, thereby suppressing pressure loss on the outside air side. Also, although heat exchange generally occurs due to the temperature difference between the outside air and the inside air, suppressing the flow rate of outside air makes it possible to suppress heat loss due to heat exchange.

[0018] Inside the housing 10, ２ A separation element 20, an inside air fan 31 (circulation fan), an inside air filter 37, an outside air fan 41, and an outside air filter 47 are attached. ２ The separation element 20 separates CO from the inside air that has flowed through the inside air inlet duct 52. ２ and CO ２ This is to introduce CO from the inside air to the outside air. ２ It can be said that the material is a member that selectively transmits CO ２ The separation element 20 will be described in detail later.

[0019] The inside air fan 31 is a blower that draws inside air from the target space through the inside air port 33 and discharges it into the target space through the air supply port 35. The inside air drawn from the target space through the inside air port 33 by driving the inside air fan 31 passes through the inside air filter 37, the CO ２The air passes through the separation element 20 and the internal air fan 31 and is discharged into the target space through the air intake port 9. The volume of air sent out by the internal air fan 31 is preferably greater than the volume of air sent out by the external air fan 41. The internal air filter 37 removes dirt, dust, etc. from the internal air that has flowed into the housing 10 and filters the purified air to remove CO ２ This is a filter that supplies air to the separation element 20, and is, for example, a HEPA (High Efficiency Particulate Air) filter.

[0020] The outdoor air fan 41 is a blower that draws in outdoor air from the outside through the outdoor air port 43 and discharges it to the outside through the exhaust port 45. The outdoor air drawn in through the outdoor air port 43 by driving the outdoor air fan 41 passes through the outdoor air filter 47, the CO ２ The air passes through the separation element 20 and the outside air fan 41, and is then discharged to the outdoors via the exhaust port 45. The volume of air sent out by the outside air fan 41 is preferably smaller than the volume of air sent out by the inside air fan 31. The outside air fan 41 is located downstream of the outside air filter 47 and is also located downstream of the CO ２ The outside air fan 41 is provided upstream of the separation element 20. By arranging the outside air fan 41 in this manner, the outside air can be heated by the heat generated by the operation of the outside air fan 41, and when the outside air is at a lower temperature than the inside air, heat loss due to heat exchange between the outside air and the inside air is reduced. ２ The outside air filter 47 may be provided downstream of the separation element 20. The outside air filter 47 removes dirt, dust, and the like from the outside air that has flowed into the housing 10, and passes the purified air through the CO ２ This is a filter supplied to the separation element 20, such as a HEPA filter.

[0021] where CO ２ CO by the separation element 20 ２ Figure 2(a)-(b) shows the outline of the separation of CO ２ 2(a) shows an outline of the separation element 20. ２1 is a cross-sectional view showing a simplified configuration of a separation element 20. A gas to be treated air passage 16 through which inside air (gas to be treated) flows from left to right and a sweep gas passage 17 through which outside air (sweep gas) flows from left to right are arranged one above the other in the vertical direction. In addition, a CO ２ The separation membrane 22 is disposed. The gas to be treated introduced into the gas to be treated air passage 16 contains CO ２ 18 and N ２ 19 is mixed in. In reality, the air contains O ２ etc. are also included, but for the sake of clarity, ２ The gas to be treated flows through the gas passage 16. ２ When flowing along the separation membrane 22, CO ２ The separation membrane 22 separates CO ２ 18 is selectively permeated, and CO ２ 18 is discharged into the sweep gas in the sweep gas duct 17. As a result, the CO ２ The concentration of 18 decreases, and the CO ２ The concentration of 18 increases.

[0022] Figure 2(b) shows a CO ２ CO for efficient separation of 18 ２ The structure of the separation element 20 is shown. ２ The separation element 20 includes a first treatment target gas passage 16a to a third treatment target gas passage 16c, which are collectively referred to as the treatment target gas passage 16; a first sweep gas passage 17a to a third sweep gas passage 17c, which are collectively referred to as the sweep gas passage 17; ２ The first CO separation membrane 22 ２ The fifth CO ２The number of the treatment target gas passages 16 and the sweep gas passages 17 is not limited to three. From top to bottom, the first sweep gas passage 17a, the first treatment target gas passage 16a, the second sweep gas passage 17b, the second treatment target gas passage 16b, the third sweep gas passage 17c, and the third treatment target gas passage 16c are arranged in this order. In addition, a first CO ２ A separation membrane 22a is disposed between the first treatment target gas passage 16a and the second sweep gas passage 17b. ２ A separation membrane 22b is disposed between the second sweep gas passage 17b and the second treatment target gas passage 16b. ２ A fourth CO 2 separation membrane 22c is disposed between the second treatment target gas passage 16b and the third sweep gas passage 17c. ２ A separation membrane 22d is disposed between the third sweep gas passage 17c and the third treatment target gas passage 16c. ２ 2(a), the CO 2 of the gas to be treated flowing through the gas to be treated air passage 16 is ２ 18 is CO ２ The gas is selectively permeated through the separation membrane 22 and discharged into the sweep gas in the sweep gas passage 17 .

[0023] FIG. 3 shows the CO ２ 1 is a perspective view showing a laminated structure 6 used as a separation element 20. In the following description, the laminated structure 6 is described as having a vertical stacking direction, but this does not necessarily indicate the direction in an actual use state. The laminated structure 6 is made up of a rectangular frame 14 and a CO ２ A rectangular CO ２ The stacked structure 6 is a structure in which the separation element pieces 21 are alternately stacked in the up-down direction, and the target gas passages 16 and the sweep gas passages 17 intersecting the target gas passages 16 are alternately formed one layer at a time. ２ While fitting the separation element piece 21 at the end of the frame 14 from both the top and bottom sides, ２ It is constructed by repeatedly stacking separation element pieces 21 and frames 14. ２When the separation element pieces 21 are fitted into the frames 14 from both the top and bottom, the frames 14 are stacked in a staggered manner, with the frames 14 orthogonal to one another. With this configuration, as shown in Fig. 2(b), gas to be treated air passages 16 through which the gas to be treated flows and sweep gas air passages 17 through which the sweep gas flows are alternately formed. By circulating the gas to be treated taken in from the target space through the gas to be treated air passages 16 and circulating the sweep gas through the sweep gas air passages 17, the gas to be treated and the sweep gas flow alternately and orthogonally through the respective air passages. In this way, the laminated structure 6 is configured such that the gas to be treated and the sweep gas flow in a staggered manner, with the CO ２ The CO flows alternately and perpendicularly in the stacking direction of the separation element pieces 21. ２ The separation element 20 is ２ CO of the separation element piece 21 ２ CO is transferred from the gas to be treated to the sweep gas side through the separation membrane 22. ２ is selectively transparent.

[0024] CO ２ The separation element piece 21 is ２ When the target gas and the sweep gas flow across the separation element piece 21, CO is introduced from the target gas to the sweep gas. ２ CO for permeating ２ It is a sheet-like member made of a separation membrane 22. ２ The separation element piece 21 is bent by being fitted by the frame 14, so it is preferable to use a material that has the flexibility and strength to withstand this bending. ２ The separation membrane 22 ２ The partial pressure difference is CO ２ The driving force for permeation is high concentration CO ２ Low concentration CO from gas ２ Gas and CO ２ In order to allow permeation of CO in the gas to be treated and the sweep gas, ２ The concentration relationship is as follows: target gas > sweep gas. Return to Figure 1.

[0025] The first temperature adjustment unit 4a ２The first temperature adjustment unit 4a is a device that adjusts the temperature of the outside air by heating or cooling the outside air that flows into the separation element 20. The first temperature adjustment unit 4a is also called an outside air temperature adjustment unit. The first temperature adjustment unit 4a is, for example, a heater / Peltier element attached to the outside air introduction duct 56. The first temperature adjustment unit 4a also adjusts the temperature of the outside air by heating or cooling the outside air that flows into the separation element 20. ２ Alternatively, an outside air fan 41 may be provided between the separation element 20 and the outside air duct. In this case, the outside air is heated using the exhaust heat of the outside air fan 41, so that the exhaust heat of the outside air fan 41 is effectively utilized. ２ The second temperature adjustment unit 4b is a device that adjusts the temperature of the inside air by heating or cooling the inside air that flows into the separation element 20. The second temperature adjustment unit 4b is also called an inside air temperature adjustment unit. The second temperature adjustment unit 4b is, for example, a heater / Peltier element attached to the inside air introduction duct 52.

[0026] The outside air temperature detection unit 7 is attached to the outside air introduction duct 56 and detects the temperature of the outside air flowing through the outside air introduction duct 56. Known technology may be used for temperature detection, and therefore a description thereof will be omitted here. Information relating to the outside air temperature detected by the outside air temperature detection unit 7 is transmitted to the control unit 5. The inside air temperature detection unit 8 detects the temperature of the inside air flowing through the inside air introduction duct 52. Information relating to the inside air temperature detected by the inside air temperature detection unit 8 is transmitted to the control unit 5.

[0027] The control unit 5 receives the temperature of the outside air detected by the outside air temperature detection unit 7 and the temperature of the inside air detected by the inside air temperature detection unit 8. The control unit 5 controls the temperature adjustment unit 4 based on the temperature of the outside air and the temperature of the inside air. Specifically, the control unit 5 ２ The temperature of the internal air introduced into the separation element 20 and the CO ２ The first temperature adjusting unit 4a is controlled so that the temperature difference between the temperature of the outside air introduced into the separation element 20 is smaller than the temperature difference between the temperature of the air in the target space and the temperature of the outdoor air. ２Heat loss due to heat exchange in the separation element 20 is reduced. For example, if the outside air temperature is 5°C and the inside air temperature is 25°C, and the temperature is not controlled, the air supplied to the target space by the inside air fan 31 will drop to about 15°C through heat exchange, requiring extra air conditioning energy to maintain the inside air at 25°C. On the other hand, if the temperature is controlled to keep the outside air at 25°C, no heat exchange occurs, and therefore no extra air conditioning energy is required. Furthermore, if temperature control is performed using the exhaust heat of the outside air fan 41, the energy required for temperature control will also be zero. The control unit 5 may control the second temperature adjustment unit 4b.

[0028] The subject of the device, system, or method disclosed herein includes a computer. The computer executes a program to realize the functions of the subject of the device, system, or method disclosed herein. The computer includes, as its main hardware configuration, a processor that operates according to the program. The type of processor is not important as long as it can realize the functions by executing the program. The processor is composed of one or more electronic circuits, including a semiconductor integrated circuit (IC) or an LSI (Large Scale Integration). The multiple electronic circuits may be integrated into a single chip or may be provided on multiple chips. The multiple chips may be integrated into a single device or may be provided on multiple devices. The program is recorded on a non-transitory recording medium, such as a computer-readable ROM, optical disk, or hard disk drive. The program may be pre-stored on the recording medium or may be supplied to the recording medium via a wide area communication network, including the Internet.

[0029] (CO ２ Separation membrane 22) Hereinafter, CO ２ The separation membrane 22 will now be described in more detail. ２ 1 is a cross-sectional view showing a schematic structure of a separation membrane 22. ２ The separation membrane 22 includes a first porous membrane 100, a hydrophilic polymer layer 102 provided on the first porous membrane 100, and a second porous membrane 104 provided on the hydrophilic polymer layer 102. ２The separation membrane 22 may include the first porous membrane 100 and the hydrophilic polymer layer 102 without including the second porous membrane 104 .

[0030] CO ２ The separation membrane 22 is, for example, ２ Since the separation system 1 is used in this case, it is assumed that the system will be used in an indoor environment with a temperature of 10 to 40°C and a relative humidity of 20 to 80%. ２ The separation membrane 22 separates CO from the air in an indoor environment. ２ Such indoor environments may include, for example, an indoor environment where the temperature is controlled within the above range by an air conditioner, an indoor environment where humidification is performed by a humidifier without using an air conditioner, an indoor environment where dehumidification is performed by a dehumidifier, and an indoor environment where neither temperature nor humidity control is performed.

[0031] The first porous membrane 100 supports a hydrophilic polymer layer 102. The first porous membrane 100 preferably has mechanical strength and adhesion to the hydrophilic polymer layer 102, and further preferably has a porosity (void ratio) of 55% or more and a pore diameter in the range of 0.1 to 1 μm. In this embodiment, a polytetrafluoroethylene (PTFE) porous membrane is used as the first porous membrane 100 satisfying these conditions. Hydrophilic PTFE may be used as the PTFE membrane. When the first porous membrane 100 is hydrophilic, the hydrophilic polymer layer 102 is also formed in the pores of the first porous membrane 100. The first porous membrane 100 is not limited to a PTFE membrane. Other than PTFE membrane, for example, resin materials such as polyethersulfone, polyvinyl fluoride, polyvinylidene fluoride, polyphenylene sulfide, polyethylene, polypropylene, polyimide, high molecular weight polyester, heat-resistant polyamide, aramid, polycarbonate, etc., inorganic materials such as metal, glass, ceramics, etc. can be used. The second porous membrane 104 may be made of the same material as the first porous membrane 100, or may be made of a different material.

[0032] The hydrophilic polymer layer 102 has an amino group in a gel film containing water, and ２The hydrophilic polymer layer 102 includes an amino acid as a carrier and an aggregation inhibitor that inhibits aggregation of the amino acid. The aggregation inhibitor contains an alkali metal element, and the amount of alkali metal element is greater than the amount of amino groups in the hydrophilic polymer layer 102. Examples of materials that can be used for the hydrophilic polymer layer 102 include, but are not limited to, polyvinyl alcohol (PVA), polyacrylic acid (PAA), polyvinyl alcohol-polyacrylate copolymer (PVA / PAA copolymer), chitosan, polyvinylamine, polyallylamine, and polyvinylpyrrolidone. The hydrophilic polymer layer 102 may also be a hydrogel layer, partially or entirely composed of a hydrogel in which hydrophilic polymers are crosslinked to form a three-dimensional network structure. Hydrogels often have the property of swelling upon absorbing water.

[0033] CO ２ Suitable amino acids that function as carriers include glycine, 2,3-diaminopropionic acid (DAPA), alanine, arginine, asparagine, serine, ornithine, creatine, threonine, 2-aminobutyric acid, sarcosine, and proline.

[0034] CO ２ When the carrier amino acid is dissolved in water, the amino group (NH ２ ) is protonated to NH ３ ＋ However, as shown in the following (chemical formula 1), carbon dioxide dissociates into a protonated amino group (NH ３ ＋ ) and does not react with the free amino group (NH ２ ) reacts with CO ２ When an amino acid is used as a carrier, a deprotonating agent is added to a solution in which the amino acid is dissolved, and NH ３ ＋ NH ２ The deprotonating agent is a protonated NH ３ ＋ It steals a proton from２ Any substance having strong basicity sufficient to convert CO into CO can be used, and hydroxides or carbonates of alkali metal elements can be suitably used. ２ During separation, the reaction shown in (Chemical Formula 1) is repeated reversibly, so the deprotonating agent is not consumed. Therefore, it is sufficient to add the deprotonating agent so that the amount of substance of the alkali metal element contained in the deprotonating agent is at most equivalent to the amount of substance of the amino group in the amino acid. For example, when glycine is used as the amino acid and a carbonate of an alkali metal element is used as the deprotonating agent, the ratio of the amount of substance of the carbonate to the amount of substance of glycine is 0.5, and when a hydroxide of an alkali metal element is used as the deprotonating agent, the ratio of the amount of substance of the hydroxide to the amount of substance of glycine is 1.0. (Chemical Formula 1) CO ２ +RNH ２ +H ２ O → HCO ３ － +RNH ３ ＋

[0035] In addition, amino acids dissociated in water undergo an equilibrium reaction. For example, glycine (NH ２ -CH ２ -COOH) dissolves in water to form [NH ３ ＋ -CH ２ -COO － ] and undergoes an equilibrium reaction as shown in the following (chemical formula 2). ３ ＋ -CH ２ -COO － ] into a zwitterionic form, [NH ２ -CH ２ -COO － ] is called the deprotonated form. (Chemical formula 2) NH ３ ＋ -CH ２ -COO － ⇔ NH ２ -CH ２ -COO －

[0036] The ratio of each state in water is determined by the pKa of the amino group and the pH of the water. The zwitterion type has a lower solubility than the deprotonated type, and the higher the ratio of the zwitterion type, the more water is required for the amino acid to dissolve. The amount of water in the gel film is determined by the ambient temperature and humidity. For example, under room temperature and low humidity conditions in an air-conditioned indoor environment, the amount of water in the gel film is low, and the concentration of the amino acid in the gel film exceeds the solubility and precipitates as aggregates. This causes defects in the gel film, and the raw material gas passes directly through the defective parts of the film, resulting in CO ２ / N ２ On the other hand, under the high temperature and humidity conditions of the hydrogen process, for example, the moisture content in the gel film is sufficiently high, so if the deprotonating agent is added so that the amount of alkali metal element contained in the deprotonating agent is equivalent to the amount of amino group in the amino acid, aggregation will not occur.

[0037] To dissolve a certain amount of amino acid, the higher the pH, i.e., the greater the amount of deprotonating agent, the less water is required. ２ In the separation membrane, CO ２ When an amino acid is used as a carrier, a protonated NH ３ ＋ It steals a proton from ２A deprotonating agent having strong basicity sufficient to convert the amino acid to glycine is added as an aggregation inhibitor. The action of the added deprotonating agent biases the equilibrium reaction toward the deprotonated form, thereby preventing the aggregation and precipitation of amino acids. A hydroxide or carbonate of an alkali metal element can be suitably used as the aggregation inhibitor. The aggregation inhibitor can be prevented in indoor environments by adding the agent so that the amount of alkali metal element contained in the agent is greater than the amount of amino group of the amino acid. For example, when glycine is used as the amino acid and a carbonate of an alkali metal element is used as the aggregation inhibitor, the ratio of the amount of carbonate to the amount of glycine is greater than 0.5. When a hydroxide of an alkali metal element is used as the aggregation inhibitor, the ratio of the amount of hydroxide to the amount of glycine is greater than 1.0. Furthermore, to further enhance the aggregation inhibition effect, it is preferable that the ratio of the amount of alkali metal element contained in the aggregation inhibitor to the amount of amino group of the amino acid is 1.5 or greater. The alkali metal element contained in the aggregation inhibitor is preferably any one of potassium, cesium, and rubidium, because they have high solubility.

[0038] (Manufacturing method) CO according to this embodiment ２ The method for manufacturing the separation membrane 22 will be described with reference to FIG. ２ 1 is a flowchart showing a procedure for producing the separation membrane 22. First, a coating solution is prepared as an aqueous solution containing a hydrophilic polymer and an amino acid (S10). More specifically, the amino acid and the aggregation inhibitor are added to water and stirred until dissolved. The hydrophilic polymer is further added to the resulting solution, and the solution is stirred at room temperature for at least three days, for example, to obtain a coating solution.

[0039] Next, the coating solution obtained in step 10 is applied to the surface of the PTFE porous membrane using an applicator and spread evenly (S12). The coating thickness in the sample of the example described below is 500 μm. Here, the PTFE porous membrane may be either hydrophilic PTFE, hydrophobic PTFE, or a laminate of hydrophilic PTFE and hydrophobic PTFE. When a hydrophilic PTFE porous membrane is used, the coating solution penetrates into the pores, but when a hydrophobic PTFE porous membrane is used, the coating solution does not penetrate into the pores.

[0040] Next, the PTFE porous membrane coated with the coating liquid is dried, for example, at 60° C. for about 30 minutes to gel the coating liquid and form a hydrophilic polymer layer 102 (S14). ２ When the separation membrane 22 is a flat plate, the exposed surface of the hydrophilic polymer layer 102 may be protected by covering it with a porous membrane such as a PTFE porous membrane, if necessary.

[0041] (Experimental Method) The experimental method for evaluating the membrane performance of each sample in the examples and comparative examples described below will be described. ２ After the separation membrane 22 was prepared, it was placed in an indoor environment (temperature: about 23°C, relative humidity: 50 to 60%) and subjected to CO ２ After the separation test was carried out for 10 consecutive days, ２ The state of the separation membrane was observed.

[0042] CO after the test ２ The separation membrane 22 was placed in a gas permeation cell (membrane area: 9.62 cm ２ The feed gas supply side chamber and the permeation side chamber of the reactor were fixed using two rubber gaskets as sealing materials. ２ 400 ppm CO in gas ２ The mixed feed gas is humidified by bubbling it through deionized water to a relative humidity of 70%. This feed gas is supplied to the feed side chamber at a flow rate of 2000 cc / min, and a sweep gas (He gas) is supplied to the permeation side chamber at a flow rate of 10 cc / min.

[0043] The composition of the gas recovered from the permeate side chamber was quantified by gas chromatography, and the CO ２ and N ２ Permeance (= permeability, one of the performance indicators of permeability) [mol / (m ２ s kPa)] and from the ratio, CO ２ / N ２ The selectivity is calculated. ２ The separation membrane ２ Permeance and CO ２ / N ２ The higher the selectivity, the higher the performance.２ To carry out the separation, for example, CO ２ Permeance is 2 x 10 －５ mol / (m ２ .s.kPa) or more, CO ２ / N ２ A selectivity of 5,000 or more is preferred.

[0044] Example 1 2.316 g of polyacrylic acid, 3.47 g of glycine, and 6.388 g of potassium carbonate were added to 86.6 g of water, and the mixture was stirred at room temperature for 3 days or more. ２ A separation solution is obtained (S10 in FIG. 5). Next, the CO obtained in step 10 ２ The separation solution is applied to a surface of a hydrophilic PTFE porous membrane (for example, a membrane thickness of 30 μm, a pore size of 0.1 μm, and a porosity of 65%) to a thickness of 500 μm using an applicator (step 12 in FIG. 5). ２ The hydrophilic PTFE porous membrane coated with the separation solution was dried at 60°C for about 30 minutes, and CO ２ The separating solution is allowed to gel to form a hydrophilic polymer layer 102 (step 14 in FIG. 5).

[0045] (Example 2) 2.316 g of polyacrylic acid, 3.47 g of glycine, and 15.06 g of cesium carbonate were added to 86.6 g of water, and the mixture was stirred at room temperature for 3 days or more. ２ A separation solution is obtained (S10 in FIG. 5). Steps 12 and 14 are the same as in Example 1.

[0046] (Example 3) 2.316 g of polyacrylic acid, 3.47 g of glycine, and 22.62 g of cesium carbonate were added to 86.6 g of water, and the mixture was stirred at room temperature for 3 days or more. ２ A separation solution is obtained (S10 in FIG. 5). Steps 12 and 14 are the same as in Example 1.

[0047] (Example 4) 2.316 g of polyacrylic acid, 3.47 g of glycine, and 5.196 g of potassium hydroxide were added to 86.6 g of water, and the mixture was stirred at room temperature for 3 days or more. ２ A separation solution is obtained (S10 in FIG. 5). Steps 12 and 14 are the same as in Example 1.

[0048] Comparative Example 1: 2.316 g of polyacrylic acid, 3.47 g of glycine, and 2.396 g of potassium carbonate were added to 86.6 g of water, and the mixture was stirred at room temperature for 3 days or more. ２ A separation solution is obtained (S10 in FIG. 5). Steps 12 and 14 are the same as in Example 1.

[0049] Comparative Example 2: 2.316 g of polyacrylic acid, 3.47 g of glycine, and 7.53 g of cesium carbonate were added to 86.6 g of water, and the mixture was stirred at room temperature for 3 days or more. ２ A separation solution is obtained (S10 in FIG. 5). Steps 12 and 14 are the same as in Example 1.

[0050] Comparative Example 3: 2.316 g of polyacrylic acid, 3.47 g of glycine, and 2.593 g of potassium hydroxide were added to 86.6 g of water, and the mixture was stirred at room temperature for 3 days or more. ２ A separation solution is obtained (S10 in FIG. 5). Steps 12 and 14 are the same as in Example 1.

[0051] (Performance Evaluation Results) FIG. 6 shows the relationship between the presence or absence of aggregation formation and membrane performance (CO ２ Permeance, CO ２ / N ２ 1 is a table showing the evaluation results of CO ２ Permeance is 1.1 x 10 －４ mol / (m ２ ・s・kPa), CO ２ / N ２ The selectivity was 12,000. ２ Permeance is 1.0 x 10 －４ mol / (m ２ ・s・kPa), CO ２ / N ２ The selectivity was 23,000. ２ Permeance is 9.2 x 10 －５ mol / (m ２ ・s・kPa), CO ２ / N ２ The selectivity was 20,000. ２ Permeance is 8.9 x 10 －５ mol / (m ２ ・s・kPa), CO２ / N ２ The selectivity was 14,000. In Examples 1 to 4, the CO ２ Permeance and CO ２ / N ２ This is because the material composition suppresses aggregation, and even after time has passed since film production in an indoor environment, aggregation does not form, making it possible to form a uniform film without defects.

[0052] On the other hand, in Comparative Example 1, CO ２ / N ２ The selectivity was 110. ２ / N ２ The selectivity was 430. ２ / N ２ The selectivity was 280. ２ / N ２ The selectivity is shown in Table 1 for Examples 1 to 4. ２ / N ２ This is because the material composition causes agglomeration over time after film production in an indoor environment, and the agglomeration occurs, causing defects in the film that allow the source gas to pass through directly.

[0053] Figures 7(a) and 7(b) show the surfaces of Example 1 and Comparative Example 1, comparing the presence or absence of agglomeration. As shown in Figure 7(a), no agglomerates are observed in Example 1, and the film is uniform. On the other hand, as shown in Figure 7(b), agglomerates are sparsely formed on the film surface in Comparative Example 1.

[0054] According to this embodiment, the amount of alkali metal element contained in the aggregation inhibitor is greater than the amount of amino group in the hydrophilic polymer layer 102, so that the equilibrium reaction can be biased toward the deprotonation type. In addition, since the equilibrium reaction is biased toward the deprotonation type, CO ２ It is possible to suppress the precipitation of amino acids in the separation membrane 22. Furthermore, since the ratio of the amount of substance of alkali metal elements to the amount of substance of amino groups in the hydrophilic polymer layer 102 is 1.5 or more, a necessary amount of deprotonating agent can be added.

[0055] Furthermore, since the amino acid is at least one selected from the group consisting of glycine, 2,3-diaminopropionic acid, alanine, arginine, asparagine, serine, ornithine, creatine, threonine, and 2-aminobutyric acid, CO ２ The agglomeration inhibitor can provide a carrier. In addition, since the agglomeration inhibitor contains a hydroxide or a carbonate of an alkali metal element, it can provide a deprotonating agent. In addition, since the alkali metal element contained in the agglomeration inhibitor is any one of potassium, cesium, and rubidium, it can provide a deprotonating agent.

[0056] The outline of one aspect of the present disclosure is as follows: (Item 1) CO in the air in an indoor environment ２ CO ２ In the separation membrane (22), ２ a hydrophilic polymer layer (102) containing an amino acid as a carrier and an aggregation inhibitor that inhibits aggregation of the amino acid; and a porous membrane (100) supporting the hydrophilic polymer layer (102), wherein the aggregation inhibitor contains an alkali metal element, and the amount of substance of the alkali metal element is greater than the amount of substance of the amino group in the hydrophilic polymer layer (102). ２ Item 2: The CO separation membrane according to Item 1, wherein the ratio of the amount of substance of the alkali metal element to the amount of substance of the amino group in the hydrophilic polymer layer is 1.5 or more. ２ Separation membrane (22). (Item 3) The CO2 separation membrane according to item 1 or 2, wherein the amino acid is at least one selected from the group consisting of glycine, 2,3-diaminopropionic acid, alanine, arginine, asparagine, serine, ornithine, creatine, threonine, and 2-aminobutyric acid. ２ Separation membrane (22). (Item 4) The CO 2 separation membrane according to any one of Items 1 to 3, wherein the aggregation inhibitor contains a hydroxide of an alkali metal element or a carbonate of an alkali metal element. ２ A CO separation membrane (22) according to any one of items 1 to 4, wherein the alkali metal element contained in the coagulation inhibitor is any one of potassium, cesium, and rubidium. ２Separation membrane (22). (Item 6) The CO 2 separation membrane according to any one of Items 1 to 5. ２ CO separation membrane (22) ２ A separation element (20).

[0057] The present disclosure has been described above based on the embodiments. These embodiments are merely examples, and it will be understood by those skilled in the art that various modifications are possible in the combination of each component or each treatment process, and that such modifications are also within the scope of the present disclosure.

[0058] According to the present disclosure, it is possible to suppress the precipitation of amino acids in a CO2 separation membrane.

[0059] 1 CO ２ Separation system, 2 Building, 4 Temperature control unit, 5 Control unit, 6 Laminated structure, 7 Outdoor air temperature detection unit, 8 Indoor air temperature detection unit, 10 Housing, 14 Frame, 16 Gas to be treated air passage, 17 Sweep gas air passage, 18 CO ２ , 19 N ２ , 20 CO ２ Separation element, 21 CO ２ Separation element piece, 22 CO ２ Separation membrane, 31 indoor air fan, 33 indoor air outlet, 35 air intake port, 37 indoor air filter, 41 outdoor air fan, 43 outdoor air outlet, 45 exhaust port, 47 outdoor air filter, 51 indoor air intake port, 52 indoor air introduction duct, 53 indoor air outlet, 54 indoor air outlet duct, 55 outdoor air intake port, 56 outdoor air introduction duct, 57 outdoor air outlet, 58 outdoor air outlet duct, 100 first porous membrane, 102 hydrophilic polymer layer, 104 second porous membrane.

Claims

1. CO in the air in an indoor environment ２ CO ２ In the separation membrane, ２ a hydrophilic polymer layer containing an amino acid as a carrier and an aggregation inhibitor that inhibits aggregation of the amino acid; and a porous membrane supporting the hydrophilic polymer layer, wherein the aggregation inhibitor contains an alkali metal element, and the amount of substance of the alkali metal element is greater than the amount of substance of the amino group in the hydrophilic polymer layer. ２ Separation membrane.

2. The CO 2 film according to claim 1, wherein the ratio of the amount of substance of the alkali metal element to the amount of substance of the amino group in the hydrophilic polymer layer is 1.5 or more. ２ Separation membrane.

3. The CO composition according to claim 1 or 2, wherein the amino acid is at least one selected from the group consisting of glycine, 2,3-diaminopropionic acid, alanine, arginine, asparagine, serine, ornithine, creatine, threonine, and 2-aminobutyric acid. ２ Separation membrane.

4. The CO2 solution according to any one of claims 1 to 3, wherein the aggregation inhibitor contains a hydroxide of an alkali metal element or a carbonate of an alkali metal element. ２ Separation membrane.

5. The CO2 inhibitor according to any one of claims 1 to 4, wherein the alkali metal element contained in the coagulation inhibitor is any one of potassium, cesium, and rubidium. ２ Separation membrane.

6. CO according to any one of claims 1 to 5 ２ CO separation membranes ２ Separation element.

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