Method for producing dehydrated steam gas, method for recovering co2, method for producing chemical reaction product of co2 and co2 absorbent, co2 gas recovery system, and ionic liquid membrane

Abstract

The present invention provides: a method for producing dehydrated steam gas, said method including selectively removing water vapor in atmospheric air by passing the atmospheric air through an ionic liquid membrane; a method for recovering CO2 using the same; a method for producing a chemical reaction product of CO2 and a CO2 absorbent; a CO2 gas recovery system; and an ionic liquid membrane to be used with the above.

Description

Method for producing dehydrated steam gas, method for recovering CO2, method for producing chemical reaction product of CO2 and CO2 absorbent, CO2 gas recovery system, and ionic liquid membrane

[0001] The present invention relates to a method for producing dehydrated steam gas, ２ recovery method, CO ２ and CO ２ Method for producing a chemical reaction product with an absorbent, CO ２ This invention relates to a gas recovery system and an ionic liquid membrane.

[0002] By 2050, carbon dioxide (CO ２ In order to reduce greenhouse gas emissions, including CO2 emissions, to zero overall (achieving carbon neutrality in 2050), renewable energy technologies and energy-saving technologies are being developed and popularized. However, as described in Non-Patent Document 1, ２ Negative emission technologies are considered essential as a means of offsetting emissions (residual emissions) from sectors where CO emissions are unavoidable, and ２ There is an increasing need for direct air capture (DAC) technology to directly recover this.

[0003] High concentration (approximately 10,000 ppm or more) of CO ２ CO from exhaust gases containing CO ２ Regarding the recovery method, CO ２ absorption method in which CO is absorbed in an absorption solution, ２ Adsorption (absorption) separation method, in which CO is adsorbed or absorbed onto a solid and then separated; ２ Membrane separation, liquefaction, distillation, and CO separation by difference in boiling point ２ Research and development of cryogenic separation methods for separating CO from other gases such as nitrogen gas is currently underway. ２ There is a demand for improved gas selectivity. ２ In DAC technology, the target of CO capture is the atmosphere. ２ The concentration is extremely low at about 400 ppm, so nitrogen (N ２) gas and / or oxygen (O ２ ) CO relative to gas ２ Development is being carried out with an emphasis on highly selective gas recovery. For example, Patent Document 1 describes a method for recovering CO from the atmosphere. ２ CO obtained by gas separation membrane ２ O mixed in concentrated gas ２ For the purpose of removing gases, etc., the CO ２ CO in concentrated gas ２ is absorbed onto a solid catalyst, and O ２ CO etc. ２ Components other than CO are removed and then converted to methane. ２ Recover CO ２ As a membrane separation method, for example, Patent Document 2 describes a CO separation / conversion device that holds an ionic liquid composition containing two specific types of ionic liquids. ２ The separation membrane ２ permeability and N ２ CO ２ Improved selectivity of CO ２ Patent Document 3 describes an apparatus for selectively separating and recovering CO. The apparatus is composed of a hydrophilic polymer layer containing a specific deprotonating agent and a porous membrane. ２ / O ２ Selectivity and CO ２ / N ２ Selective CO ２ Using a facilitated transport membrane, CO ２ , N ２ , and O ２ from the gas to be treated containing CO ２ Patent Document 4 also describes a method for selectively removing CO by using an ionic liquid-containing laminate including a porous layer with affinity for an ionic liquid, in which an ionic liquid-containing liquid is held in the pores, and a porous layer with no affinity for an ionic liquid, and reducing the pressure on the permeation side relative to the air supply side and supplying a sweep gas. ２ Furthermore, Non-Patent Document 3 describes the latest CO ２ Simulations have been carried out on DACs that take membrane separation performance into account, and CO ２ / N ２ In addition to selectivity, high CO ２ / O２ Furthermore, for example, Patent Document 5 describes a temperature vacuum swing adsorption-desorption cycle using an adsorbent, and a method for extracting CO from the atmosphere by performing a temperature swing and steam purging in the desorption step. ２ Patent Document 6 describes a method for separating and recovering CO from the atmosphere. ２ is absorbed and released from the regeneration tower, ２ CO is recovered by solidifying (sublimating) ２ Patent Document 7 describes a CO recovery device. ２ Gas and CO ２ CO2 is absorbed by chemical absorption in contact with a capture solution. ２ A gas liquid contactor is described for recovering

[0004] Ministry of Economy, Trade and Industry, "Summary of the Study Group for Creating a Negative Emission Market (Reference Material)," June 28, 2023. Waqad Ul Mulk, et al., Journal of CO2 Utilization. 2023, No. 75, No. 102555. Shigenori Fujikawa, Roman Selyanchyn, Toyoki Kunitake, Polymer Journal. 2021, No. 53, pp. 111-119.

[0005] JP 2023-141360 A JP 2023-30786 A International Publication No. 2019 / 130470 International Publication No. 2018 / 211944 International Publication No. 2016 / 005226 International Publication No. 2021 / 221007 International Publication No. 2022 / 140489

[0006] DAC technology extracts extremely low concentrations of CO from the atmosphere. ２ In order to recover a large amount of CO, it is necessary to process a large amount (large flow rate) of air. ２ To capture 1 ton of CO ２ Even if we assume a recovery process with a 100% recovery rate, the recovery rate is 1.33 million m3 of air at 20°C and 1 atmosphere. ３ (At least the volume of the Tokyo Dome (approximately 1.24 million m ３In addition to the above, it will be necessary to treat atmospheric CO ２ is an extremely low concentration, so CO ２ In Japan, to achieve carbon neutrality in 2050, it is necessary to use DAC to remove CO2 at the level of 100 billion tons per year. ２ However, from a chemical engineering perspective, it is not feasible to build a plant that would also need to treat the enormous amount of water that would be recovered.

[0007] As a result of the investigations by the present inventors, it has been found that in all of the absorption method, adsorption method, membrane separation method and cryogenic separation method, the mixing of water vapor from the atmosphere is unavoidable, and that discussions have been based on the premise that condensation operations can be applied to water vapor, and that the impact of water vapor mixing has been neglected in previous studies. Previous technologies have lacked the perspective of large-scale balance calculations for the DAC process, and it has been found that the conventional DAC technologies described in the above Patent Documents 1 to 7 also have problems related to the mixing of water vapor from the atmosphere, and that these technologies require enormous amounts of energy to remove water vapor. In other words, the separation membrane described in Patent Document 1 permeates water in addition to oxygen, so that CO after membrane separation ２ It is also described that a moisture removal section using a cooled water trap and a molecular sieve may be provided to remove moisture from the concentrated gas. ２ / N ２ Mixed gas (CO ２ The test was only conducted for a composition of 0.04 mol%, and there is no mention of the inclusion of water vapor in the atmosphere. ２ CO that has permeated the facilitated transport membrane ２ However, the CO permeation gases described in Patent Document 3 can be immobilized by chemical absorption, chemical adsorption, physical adsorption, etc. ２ Since the facilitated transport membrane is composed of a hydrophilic polymer layer, water vapor will permeate the membrane when it is applied to the atmosphere. ２ Furthermore, the CO ２ The facilitated transport membrane contains CO２ In addition, Patent Document 4 does not mention the problem of water vapor permeating through the ionic liquid-containing laminate. In the method described in Patent Document 5, water is contained in both the adsorption and desorption steps, and high-purity CO ２ In order to obtain CO , it is essential to separate water by a condensation operation after desorption. In the cryogenic separation method described in Patent Document 6, water vapor is mixed in both the absorption and regeneration (sublimation) processes, so CO ２ Prior to the sublimation of CO, the water vapor must be removed by condensation. ２ Since this is a gas-liquid contactor that uses a capture solution (aqueous solution) as the working fluid, water vapor from the atmosphere is directly mixed in. In addition, in the summary of separation membranes described in Non-Patent Document 2 and the simulation described in Non-Patent Document 3, ２ High CO permeability and ２ It only mentions that selectivity is required, but does not mention the removal of water that gets mixed into the process, which is a problem in DAC.

[0008] Therefore, the present invention solves the problems of the DAC technology described above, removes water vapor from the atmosphere without requiring a huge amount of energy, and removes extremely low concentrations of CO contained in the atmosphere. ２ The goal is to develop new technologies that will serve as the foundation for realizing a commercial DAC process for gas recovery.

[0009] That is, the present invention aims to provide a method for producing a dehydrated vapor gas that removes water vapor from the atmosphere without requiring a huge amount of energy. The present invention also aims to provide a method for removing water vapor from the atmosphere without requiring a huge amount of energy and for removing extremely low concentrations of CO contained in the atmosphere. ２ Selectively recovering gases, CO ２ Recovery method and CO ２ The present invention also aims to provide a gas recovery system. ２ CO recovery method, ２ and CO ２The present invention aims to provide a method for producing a chemical reaction product with an absorbent. Another objective of the present invention is to provide an ionic liquid membrane that can remove water vapor from the atmosphere without requiring a huge amount of energy.

[0010] As a result of extensive and intensive research by the present inventors, including conventional knowledge, it was found that membrane separation using an ionic liquid membrane and CO ２ CO by absorption solution ２ By combining this with selective absorption of CO2 gases, it is possible to selectively remove water vapor from the atmosphere without requiring a huge amount of energy, and also to remove extremely low concentrations of CO2 contained in the atmosphere. ２ It has become clear that selective recovery of gas is possible. The present invention was completed through further investigation based on these findings.

[0011] The above-mentioned problems of the present invention have been solved by the following means: [1] A method for producing a dehydrated vapor gas, comprising passing atmospheric air through an ionic liquid membrane to selectively remove water vapor from the atmospheric air. [2] The method for producing a dehydrated vapor gas according to [1], wherein the total gas pressure on the side of the ionic liquid membrane that comes into contact with the atmospheric air is the same as the total gas pressure on the side opposite to the side that comes into contact with the atmospheric air. [3] The dehydrated vapor gas is a dehydrated vapor gas containing CO ２[4] The method for producing a dehydrated vapor gas according to any one of [1] to [3], wherein the ionic liquid membrane is a composite membrane formed by impregnating a porous support membrane with an ionic liquid. [5] The method for producing a dehydrated vapor gas according to any one of [1] to [4], wherein the ionic liquid constituting the ionic liquid membrane comprises at least one ionic liquid selected from the group consisting of a tetraalkylphosphonium salt having an alkyl group of 5 or more carbon atoms and an imidazolium salt having an alkyl group of 5 or more carbon atoms. [6] The method for producing a dehydrated steam gas according to [5], wherein the ionic liquid constituting the ionic liquid membrane comprises at least one selected from the group consisting of 1-ethyl-3-methylimidazolium aminoacetate, 1-butyl-3-methylimidazolium dicyanamide, 1-ethyl-3-methylimidazolium dicyanamide, 1-butyl-3-methylimidazolium hexafluorophosphate, trihexyl(tetradecyl)phosphonium bis(trifluoromethylsulfonyl)amide, trihexyl(tetradecyl)phosphonium bromide, trihexyl(tetradecyl)phosphonium chloride, trihexyl(tetradecyl)phosphonium dicyanamide, and 1-methyl-3-n-octylimidazolium hexafluorophosphate. [7] A method for producing a dehydrated steam gas according to any one of [1] to [6], wherein the dehydrated steam gas obtained by the method for producing a dehydrated steam gas according to any one of [1] to [6] and the CO in the dehydrated steam gas are mixed together to produce a dehydrated steam gas. ２ CO selectively absorbs gas ２ By contacting with the absorption liquid, ２ CO ２ [8] A method for recovering CO ２ [7] The CO absorbing solution according to [7], wherein the absorbing solution contains at least one of an aqueous solution of a metal hydroxide and a liquid amine. ２ [9] A method for recovering CO ２ [8] The CO absorbing solution according to [8], wherein the absorbing solution contains at least one of an aqueous calcium hydroxide solution, an aqueous potassium hydroxide solution, and liquid ethylenediamine. ２

[10] A method for recovering CO according to any one of [7] to [9]. ２ By passing through the recovery method of the CO ２ CO in the absorption solution２ The absorbent and the CO ２ obtaining a chemical reaction product with CO ２ and CO ２

[11] A method for producing a chemical reaction product with an absorbent. ２ and CO ２ The CO absorbent according to

[10] , wherein the chemical reactant with the absorbent is calcium carbonate or carbamic acid. ２ and CO ２

[12] A method for producing a chemical reaction product with an absorbent. ２ A gas recovery system, comprising: ２ The gas recovery system consists of an atmospheric supply side where atmospheric air flows and a CO ２ CO with absorbent ２ The air supply side is separated from the absorption side by an ionic liquid membrane, and the air flowing through the air supply side has water vapor removed by the action of the ionic liquid membrane to become dehydrated vapor gas, which is then converted into CO ２ The CO ２ The absorption liquid absorbs the CO in the dehydrated vapor gas. ２ Selectively absorbs gases, CO ２

[13] The CO gas recovery system according to

[12] , wherein the ionic liquid membrane is disposed on a gas-permeable support. ２

[14] A gas recovery system.

[15] An ionic liquid membrane for passing atmospheric air through the membrane and selectively blocking the permeation of water vapor in the atmosphere. ２ The ionic liquid membrane according to

[14] , which is for gas permeation.

[0012] In the present invention, when describing physical properties, etc., by showing a numerical range, if the upper and lower limits of the numerical range are described separately, any of the upper and lower limits can be appropriately combined to form a specific numerical range. On the other hand, when describing multiple numerical ranges expressed using "to", the upper and lower limits forming the numerical range are not limited to the combination of the specific upper and lower limits written before and after "to" as a specific numerical range, but can be a numerical range obtained by appropriately combining the upper and lower limits of each numerical range. Note that in the present invention, a numerical range expressed using "to" means a range that includes the numerical values ​​written before and after "to" as the upper and lower limits.

[0013] According to the method for producing a dehydrated vapor gas of the present invention, water vapor can be removed from the atmosphere without requiring a huge amount of energy, and a dehydrated vapor gas can be obtained. ２ and the CO recovery method of the present invention ２ The gas recovery system removes water vapor from the atmosphere without requiring a huge amount of energy, and also removes extremely low concentrations of CO contained in the atmosphere. ２ The CO gas can be selectively recovered. ２ and CO ２ According to the method for producing the chemical reaction product with the absorbent, ２ By using this method, water vapor can be removed from the atmosphere without requiring a huge amount of energy, and the extremely low concentration of CO contained in the atmosphere can be removed. ２ gas, CO ２ The ionic liquid membrane of the present invention can selectively recover water vapor as a chemical reaction product with the absorbent. Furthermore, the ionic liquid membrane of the present invention can remove water vapor from the atmosphere without requiring a huge amount of energy.

[0014] CO2 combined with membrane separation and absorption ２ This is an explanatory diagram showing a schematic overview of a CO recovery system (semi-batch type). ２

[0023] FIG. 1 is an explanatory diagram showing a schematic overview of a recovery system (flow type).

[0024] FIG. 1 is a photograph used in the examples, showing the state of the membrane separation absorption apparatus body from an obliquely upward direction.

[0025] The ionic liquid membrane is fixed to the membrane separation absorption apparatus body by a packing and a flange, and the upper part of the apparatus body has two supply gas inlets and two supply gas outlets connected to hoses for connecting to an air compressor.

[0026] FIG. 1 is a graph showing the relationship between the absolute value of the mass change of the apparatus (the mass before the start of the experiment minus the mass after the end of the experiment) and the amount of calcium carbonate recovered, obtained in Example 4.

[0027] FIG. 1 is a graph showing the amount of water mixed into the TEG sample recovered under "bare conditions" and the TEG sample recovered under "SILMs conditions" after an air exposure experiment (exposure time: 24 hours, average temperature: 23.6°C, average relative humidity: 65%).

[0015] Preferred embodiments of the present invention will be described below, but the present invention is not limited to the following embodiments except as defined in the present invention.

[0016] [Method for Producing Dehydrated Vapor Gas] The method for producing dehydrated vapor gas of the present invention involves passing atmospheric air through an ionic liquid membrane to selectively remove water vapor from the air. In the method for producing dehydrated vapor gas of the present invention, water vapor can be selectively removed from the air by passing the air through an ionic liquid membrane. This is because the ionic liquid membrane has high gas permeability to atmospheric gases in general but low permeability to water vapor. Therefore, passing the air through an ionic liquid membrane not only selectively removes water vapor but also selectively removes gases of components readily soluble in water (referred to as "gases of readily water-soluble components") together with the water vapor. In other words, in the present invention, "selectively removing water vapor" encompasses not only the selective removal of water vapor itself but also the removal of gases of readily water-soluble components together with the water vapor. In the present invention, "dehydrated vapor gas" refers to a "gas" obtained by selectively removing "water vapor" from the air, and refers to a gas in which the water vapor concentration is reduced compared to the air before passing through the ionic liquid membrane. In other words, the method for producing dehydrated steam gas of the present invention can be regarded as a method for reducing the concentration of water vapor gas in the atmosphere. In the present invention, examples of "gases of components readily soluble in water" include gases of amine compounds such as ethylenediamine and ammonia. In the present invention, "atmosphere" means the air on Earth, and usually includes CO ２ The CO concentration in the air is 2000 ppm or less. There are no restrictions on the location of the air, and it can be outdoor air or indoor air. ２ The concentration is usually below 500 ppm and the CO ２ The concentration is usually below 2000 ppm. ２ The lower limit of the concentration is usually 350 ppm or more, and preferably 400 ppm or more. ２ The concentration range is, for example, 350 to 2000 ppm, preferably 400 to 2000 ppm, and more preferably 400 to 500 ppm. ２ The concentration is as high as 10,000 ppm or more, and is not included in the "air" in the present invention.

[0017] The method for producing a dehydrated vapor gas of the present invention can be carried out without temperature adjustment, such as heating or cooling, or pressure adjustment, such as pressurization or depressurization, when the air passes through the ionic liquid membrane, and therefore can be carried out without consuming energy for adjusting these temperatures and pressures. In the method for producing a dehydrated vapor gas of the present invention, the temperature of the air passed through the ionic liquid membrane is, for example, 10°C to 40°C, and preferably 20°C to 30°C. In the method for producing a dehydrated vapor gas of the present invention, it is preferable that the total gas pressure on the side of the ionic liquid membrane that comes into contact with the air (hereinafter referred to as the "feed side") (feed-side total gas pressure) is the same as the total gas pressure on the side opposite to the side that comes into contact with the air (hereinafter referred to as the "permeation side") (permeation-side total gas pressure). Here, "the feed-side total gas pressure and the permeation-side total gas pressure are the same" means that the feed-side total gas pressure and the permeation-side total gas pressure are substantially the same. An example of a configuration in which the feed-side total gas pressure and the permeation-side total gas pressure are substantially the same is a configuration in which the differential pressure between the feed-side total gas pressure and the permeation-side total gas pressure is 0 kPa or more and 101 kPa or less. This differential pressure is preferably 0 kPa or more and 90 kPa or less, more preferably 0 kPa or more and 70 kPa or less, and even more preferably 0 kPa or more and 50 kPa or less. Note that when this differential pressure is not 0 Pa, the feed-side total gas pressure is usually higher than the permeation-side total gas pressure. In the method for producing a dehydrated steam gas of the present invention, atmospheric air can be supplied by the movement of the atmospheric air itself, such as wind. Alternatively, it may be supplied by an energy-saving means that does not require pressurization energy, such as a fan.

[0018] In the method for producing a dehydrated steam gas of the present invention, the dehydrated steam gas is a gas obtained by removing water vapor gas from the atmosphere, while CO ２ The dehydrated vapor gas typically contains nitrogen gas, oxygen gas, and other gases. Although the permeability varies somewhat depending on the gas species, the ionic liquid membrane also allows nitrogen gas and oxygen gas to permeate.

[0019] [Ionic Liquid Membrane] The ionic liquid membrane is not particularly limited as long as it is a membrane in which an ionic liquid exists as a liquid membrane and has the function of selectively removing water vapor from the atmosphere as a whole. The ionic liquid membrane can selectively remove at least CO as a gas component other than water vapor (and gases of water-soluble components) from the atmosphere. ２ It is permeable to gases. ２ In addition to the above gases, gases such as nitrogen gas and oxygen gas usually also permeate the membrane.

[0020] (Ionic Liquid) As the ionic liquid, any compound known as an ionic liquid (a compound composed of a cation and an anion and existing as a liquid at room temperature and normal pressure (for example, 25°C, 0.1 MPa)) can be used without any particular limitation. The ionic liquid may be used alone or in combination of two or more. Among these, the CO ２ In the recovery method of CO ２ CO due to volatilization of evaporative components from the absorption liquid ２From the viewpoint of suppressing loss of the absorption liquid, the ionic liquid preferably contains at least one selected from tetraalkylphosphonium salts having an alkyl group with 5 or more carbon atoms and imidazolium salts having an alkyl group with 5 or more carbon atoms. It is more preferable that the hydrophobic ionic liquid contains at least one selected from tetraalkylphosphonium salts having an alkyl group with 5 or more carbon atoms and imidazolium salts having an alkyl group with 8 or more carbon atoms. The tetraalkylphosphonium salt having an alkyl group with 5 or more carbon atoms refers to a tetraalkylphosphonium salt in which all four alkyl groups in the tetraalkylphosphonium ion constituting the salt have 5 or more carbon atoms (preferably 5 to 20). The four alkyl groups may be the same or different, provided they each have 5 or more carbon atoms. Examples of tetraalkylphosphonium salts having alkyl groups with 5 or more carbon atoms include trihexyl(tetradecyl)phosphonium salt, trihexyl(octadecyl)phosphonium salt, triheptyl(tetradecyl)phosphonium salt, and trioctyl(tetradecyl)phosphonium salt. Furthermore, the imidazolium salt having an alkyl group and 5 or more carbon atoms refers to an imidazolium salt in which the total carbon number of the imidazolium ions constituting the salt is 5 or more (preferably 5 to 20, more preferably 8 to 20, and even more preferably 8 to 15), and in which the imidazolium ion has an alkyl group. It is preferable that both of the two nitrogen atoms constituting the imidazolium ring in the imidazolium ion are substituted with alkyl groups. Examples of imidazolium salts having an alkyl group and 5 or more carbon atoms include ethylimidazolium salt, butylimidazolium salt, octylimidazolium salt, and decylimidazolium salt. The atoms constituting the imidazolium ring in these imidazolium salts may be further substituted with an alkyl group, such as a methyl group or an ethyl group.Of the ionic liquids, the hydrophilic ionic liquid preferably contains at least one selected from the group consisting of 1-ethyl-3-methylimidazolium aminoacetate ([Emim][Gly]), 1-butyl-3-methylimidazolium dicyanamide ([Bmim][DCA]), and 1-ethyl-3-methylimidazolium dicyanamide ([Emim][DCA]). Among the ionic liquids, examples of hydrophobic ionic liquids include 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim][PF6]), trihexyl(tetradecyl)phosphonium bis(trifluoromethylsulfonyl)amide ([ThtdP][NTf2], available, for example, as Cyphos IL109 (trade name) manufactured by Syensqo), trihexyl(tetradecyl)phosphonium bromide ([ThtdP][Br], available, for example, as Cyphos IL102 (trade name) manufactured by Syensqo), trihexyl(tetradecyl)phosphonium chloride ([ThtdP][Cl], available, for example, as Cyphos IL101 (trade name) manufactured by Syensqo), and trihexyl(tetradecyl)phosphonium dicyanamide ([ThtdP][DCA], available, for example, as Cyphos IL109 (trade name) manufactured by Syensqo). Preferably, the ionic liquid contains at least one selected from the group consisting of IL105 (trade name) and 1-methyl-3-n-octylimidazolium hexafluorophosphate ([Omim][PF6]). More preferably, the ionic liquid contains at least one selected from the preferred hydrophilic ionic liquids described above and the preferred hydrophobic ionic liquids described above.

[0021] The ionic liquid membrane is preferably, for example, in the form of a composite membrane obtained by impregnating a porous support membrane with an ionic liquid. (Porous support membrane) The porous support membrane is a support (support membrane) capable of retaining (supporting) an ionic liquid as a liquid membrane, and refers to a porous membrane having a large number of through-holes with a pore diameter of 0.00030 μm or more and 100 μm or less. The distribution of the pores in the porous support membrane may be uniform or non-uniform both in the plane of the membrane and in the cross section of the membrane. The porous support membrane itself (portions other than the pores) does not allow water vapor to pass through, and allows CO ２ It is preferable that the porous support membrane is not reactive to gases. It is also preferable that the porous support membrane has an affinity with the ionic liquid that allows it to retain the ionic liquid. The type of porous support membrane is not particularly limited, and examples thereof include membrane filters, filter paper, and mesh filters made of inorganic materials such as resins or metals. The material constituting the porous support membrane is not particularly limited, and examples thereof include polytetrafluoroethylene (PTFE), polyvinylidene fluoride, polyethylene terephthalate (PET), nylon, cellulose, stainless steel, glass, and quartz. For example, a porous support membrane may be formed from these fibers. Examples of porous support membranes include membrane filters made of polytetrafluoroethylene fibers that have been subjected to a surface hydrophilic treatment. The pore size of the porous support membrane is preferably 0.00030 μm or more and 10.0 μm or less, more preferably 0.010 μm or more and 1.0 μm or less, and even more preferably 0.010 μm or more and 0.20 μm or less. The pore size of the porous support membrane is a value measured by microscopic observation. The thickness of the porous support membrane is preferably 1.0 μm or more and 200 μm or less, more preferably 1.0 μm or more and 100 μm or less, even more preferably 10 μm or more and 80 μm or less, and particularly preferably 20 μm or more and 70 μm or less. The porosity of the porous support membrane is preferably 40% or more and 95% or less, more preferably 50% or more and 90% or less, and even more preferably 60% or more and 80% or less. The porosity of the porous support membrane is a value measured and calculated by measuring the true density and bulk density.

[0022] The composite membrane obtained by impregnating the porous support membrane with an ionic liquid can be produced by a conventional method, for example, by impregnating the porous support membrane with the ionic liquid and then removing excess ionic liquid present on both sides of the porous support membrane.

[0023] The ionic liquid membrane is a composite membrane formed by impregnating a porous support membrane with an ionic liquid, and is preferably in the form of a flat membrane, a hollow fiber membrane, or a spiral membrane, which allows for an increased throughput of air passing through.

[0024] (Ionic Liquid Membrane) The ionic liquid membrane is preferably a membrane for selectively blocking the permeation of water vapor in the atmosphere. In other words, the ionic liquid membrane is a membrane for selectively blocking the permeation of at least CO as a gas component other than water vapor (and gases of water-soluble components) in the atmosphere. ２ The ionic liquid membrane may be a membrane that is permeable to gases and, although it has some selective permeability, also allows the permeation of gases such as nitrogen gas and oxygen gas. The ionic liquid membrane selectively blocks the permeation of water vapor and CO ２ It is sufficient that the carbon nanotube has the property of permeating gases, and the selective permeability to nitrogen gas, oxygen gas, etc. is not an issue. ２ In the recovery method of CO on the permeation side ２ Selective capture of CO ２ This is achieved by contact with the absorbing solution, so there is no CO in the atmosphere, such as nitrogen gas and oxygen gas. ２ Even if gases other than CO ２ can be selectively recovered.

[0025] As described in Non-Patent Documents 2 and 3, CO separation using conventional separation membranes ２ In the capture technology, CO in the exhaust gas ２ Gas species other than gas (N ２ Gas, O ２ CO relative to gas, etc. ２ Selective gas permeability is CO ２The inventors have been researching and developing separation membranes as an important factor in gas recovery. They discovered that ionic liquids have the property of blocking the permeation of water vapor, and have given the ionic liquid membrane the function of selectively removing water vapor, and have succeeded in recovering CO from the permeated gas with reduced and removed water vapor. ２ CO by absorption liquid ２ The new idea of ​​selectively recovering gases has ２ CO2 can be extracted from the atmosphere at extremely low concentrations with low energy consumption. ２ Increase the feasibility of social implementation of CO2 capture technology (DAC) ２ That is, the method for producing dehydrated steam gas of the present invention is ２ The present invention can be suitably applied to the recovery method of the above.

[0026] [CO ２ CO Recovery Method of the Present Invention ２ The method for recovering the dehydrated steam gas of the present invention comprises recovering the dehydrated steam gas obtained by the method for producing the dehydrated steam gas of the present invention and recovering the CO ２ CO selectively absorbs gas ２ By contacting with the absorption liquid, ２ CO ２ The recovery of CO from the dehydrated steam gas ２ It is sufficient to selectively recover the gas, and CO ２ There are no particular limitations on the form of recovery of CO. ２ may be recovered as CO ２ and CO ２ It may be recovered as a chemical reaction product with the absorbent, ２ and CO ２ CO containing chemical reactants with the absorbent ２ The chemical reaction product may be further subjected to chemical treatment to recover CO ２ It is also possible to convert the CO of the present invention back into CO and recover it. ２ The capture method involves the use of an ionic liquid membrane to remove water from the feed gas (atmospheric air) and a CO ２ Selectively absorbs CO ２ By combining with an absorption liquid, extremely low concentration CO ２The separation of water from the atmosphere containing CO is achieved with reduced energy consumption. ２ In addition to being able to selectively block the permeation of water vapor, the ionic liquid membrane also blocks the permeation of liquid and / or solid water that may be present in the atmosphere, such as rain, snow, and snow water, and can selectively recover CO ２ Furthermore, the ionic liquid membrane can suppress the permeation of vaporized matter from the permeation side, and can also prevent CO ２ The absorption liquid is separated from the supply side atmosphere by an ionic liquid membrane and CO ２ By saturating the space between the absorbent and the CO ２ It is possible to suppress evaporation of volatile components in the absorption liquid (for example, solvents such as water, liquid amine). ２ The loss of the absorption liquid can be effectively reduced. ２ Contact with the absorbing solution can usually be carried out under atmospheric pressure conditions, and pressure adjustment is not required. Therefore, physical absorption of highly concentrated gas species such as nitrogen gas and oxygen gas can be suppressed. In the present invention, "atmospheric pressure" means 87 kPa or more and 108 kPa or less.

[0027] (CO ２ Absorbing solution) CO of the present invention ２ The recovery method is to extract CO from the dehydrated steam gas. ２ The function of selectively recovering gas is CO ２ The absorbent takes care of this. ２ The absorbent absorbs CO from the dehydrated vapor gas. ２ Any liquid that can selectively absorb gases is sufficient. ２ The absorption liquid itself is already widely known and has been put to practical use. ２ The absorption liquid is CO ２ It is preferable that the liquid be a liquid that chemically absorbs the gas through a chemical reaction (chemical absorption liquid). ２ In contact with the absorbent, the chemical absorbent absorbs the CO in the dehydrated steam gas. ２The chemical absorption liquid preferably contains at least one of an aqueous solution of a metal hydroxide and a liquid amine, and more preferably at least one of an aqueous solution of a metal hydroxide and a liquid amine. In this case, the CO ２ The absorbent is a metal hydroxide and / or a liquid amine. Examples of metal hydroxides used in the metal hydroxide aqueous solution include hydroxides of alkali metals and hydroxides of alkaline earth metals, and preferred examples include sodium hydroxide, magnesium hydroxide, potassium hydroxide, and calcium hydroxide, with potassium hydroxide and calcium hydroxide being more preferred. The concentration of the metal hydroxide in the metal hydroxide aqueous solution may be, for example, 0.010 mol / L or more and 10 mol / L or less, preferably 0.10 mol / L or more and 5.0 mol / L or less, and more preferably 0.50 mol / L or more and 2.0 mol / L or less. Examples of the liquid amine include CO ２ The amine may be in a liquid state itself under the conditions for recovering the amine, and may be in a liquid state as a glycol solution of the amine. Specifically, the amine or glycol solution of the amine is preferably in a liquid state under conditions of 10°C to 40°C and 87 kPa to 108 kPa. Examples of the liquid amine include diamines such as ethylenediamine, 1,3-diaminopropane, and 1,2-diaminopropane. Other examples include glycol solutions of alkanolamines such as monoethanolamine, 2-amino-2-methyl-1-propanol, diethanolamine, N-methyldiethanolamine, 1-diethylamino-2-propanol, and diisopropanolamine. Examples of glycol solvents (dihydric alcohol solvents) used in the glycol solution of the amine include ethylene glycol, triethylene glycol, propylene glycol, and 1,4-butylene glycol. The content of the amine in the glycol solution of the amine may be, for example, 1% by mass or more and less than 100% by mass, preferably 5% by mass or more and 80% by mass or less, and more preferably 10% by mass or more and 50% by mass or less. ２The absorption liquid preferably contains at least one of an aqueous calcium hydroxide solution, an aqueous potassium hydroxide solution, liquid ethylenediamine, and a glycol solution of monoethanolamine, and more preferably contains at least one of an aqueous calcium hydroxide solution, an aqueous potassium hydroxide solution, and liquid ethylenediamine. ２ The absorption liquid is CO ２ To suppress evaporation of volatile components in the absorption liquid (for example, solvents such as water, liquid amine), the temperature is preferably somewhat low. For example, the temperature is preferably −20° C. or higher and 25° C. or lower, more preferably −10° C. or higher and 10° C. or lower, and even more preferably 0° C. or higher and 10° C. or lower.

[0028] CO in the dehydrated steam gas ２ gas and the CO ２ Regarding the contact method with the absorption liquid, ２ There are no particular limitations as long as the CO ２ Like the gas recovery system, ２ The absorption liquid may be in a stirred state (semi-batch type). ２ The CO in the dehydrated vapor gas is removed while the absorption liquid is flowing. ２ It may also be in a form of contact with a gas (flow type).

[0029] The CO of the present invention ２ As mentioned above, the method for capturing CO differs from conventional DAC technology in that it captures CO at extremely low concentrations in the atmosphere. ２ Since the gas can be recovered without temperature and / or pressure adjustment, energy consumption can be reduced compared to conventional recovery methods. In addition, since the ionic liquid is not volatile, a huge amount of air can be brought into contact with the ionic liquid membrane. ２ Facilitated transport of CO ２ The CO separation and recovery process requires the replenishment of water to eliminate water evaporation within the membrane. ２ It is not necessary for the capture method. ２The partial pressure of CO is 0.04 kPa, whereas the partial pressure of water vapor in the atmosphere at 20°C is 0.7 kPa at a relative humidity of 30% and 1.2 kPa at a relative humidity of 50%. ２ is one to two orders of magnitude larger than the partial pressure of atmospheric CO ２ Water vapor is more effective than CO ２ The CO of the present invention is easily recovered in the absorption liquid. ２ In the recovery method, the ionic liquid membrane can selectively block water vapor from the atmosphere, so CO ２ Furthermore, the use of an ionic liquid membrane can selectively block water vapor from the atmosphere, thereby overcoming the disadvantage of CO ２ Suppresses water contamination in the absorption liquid and reduces CO ２ In the present invention, since almost no pressure is applied to the permeation side (no high pressure), CO ２ Gases such as nitrogen gas, oxygen gas, and argon gas, which have a higher partial pressure than CO ２ Physical absorption into the absorbing solution can be suppressed.

[0030] The CO of the present invention ２ According to the recovery method, approximately 0.40% to 4.5% CO ２ The CO recovery rate of the present invention can be achieved. ２ Apparent CO by recovery method ２ The permeance is approximately 1.0 x 10 －４ mol / (m ２ s kPa) or more 9.9 x 10 －３ mol / (m ２ .s.kPa) or less can be achieved.

[0031] [CO ２ and CO ２ Method for producing a chemical reaction product with an absorbent] ２ and CO ２ The method for producing the chemical reaction product with the absorbent is the CO ２ By using the recovery method, CO２ CO in the absorption solution ２ an absorbent and CO ２ In the present invention, "CO ２ and CO ２ The "chemical reactant with the absorbent" is CO ２ and CO ２ This term includes not only the product itself obtained by direct chemical reaction with the absorbent, but also the product obtained by further chemical reaction of this product. ２ and CO ２ The chemical reactant with the absorbent is preferably, for example, calcium carbonate or carbamic acid. ２ When the absorption liquid contains an aqueous calcium hydroxide solution (lime water) (see Example 1), ２ The absorption liquid is an aqueous potassium hydroxide solution, and ２ When the recovery method is followed by further reaction with an aqueous calcium hydroxide solution (see Examples 2, 4, 5 and 7), the CO ２ and CO ２ Calcium carbonate is obtained as a chemical reaction product with the absorbent. ２ When the absorption liquid contains ethylenediamine, ２ and CO ２ Ethylenediaminecarbamic acid is obtained as a chemical reaction product with the absorbent (see Examples 3 and 6). Ethylenediaminecarbamic acid can be converted into ethyleneurea and further developed into synthetic resins. ２ and CO ２ According to the manufacturing method of the chemical reaction with the absorbent, the extremely low concentration of CO in the atmosphere ２ CO ２ and CO ２ The chemical reaction product with the absorbent can be obtained with reduced energy consumption.

[0032] [CO ２ Gas Recovery System] ２ The gas recovery system ２ The CO gas recovery system of the present invention. ２ The gas recovery system is２ This system is suitable for carrying out the gas recovery method. ２ The gas recovery system consists of an atmospheric supply side where atmospheric air flows and a CO ２ CO with absorbent ２ The air supply side is separated from the absorption side by an ionic liquid membrane, and the air flowing through the air supply side has water vapor removed by the action of the ionic liquid membrane to become dehydrated vapor gas, which is then converted into CO ２ The CO ２ The absorption liquid absorbs the CO in the dehydrated vapor gas. ２ Selectively absorbs gases.

[0033] The CO of the present invention ２ The gas recovery system may utilize the movement of the air itself, such as wind, as a means for supplying air, or may be equipped with an air supply means such as a fan that does not require pressurization energy (energy-saving air supply means). The ionic liquid membrane is preferably disposed on a gas-permeable support. The gas-permeable support is not particularly limited as long as it has the function of supporting the ionic liquid membrane, and examples thereof include porous supports such as meshes made of metals such as stainless steel, copper, silver, gold, or platinum, or alloys thereof, or ceramics. ２ The gas recovery system ２ In order to suppress evaporation of volatile components in the absorption liquid (for example, solvents such as water, liquid amine), ２ A mechanism for cooling the absorption liquid may be provided. ２ The absorption liquid and the ionic liquid membrane are respectively ２ It is synonymous with absorption liquid and ionic liquid membrane. In addition, the action of the ionic liquid membrane removes water vapor from the atmosphere to form dehydrated vapor gas, and CO ２ The absorbent absorbs the CO in the dehydrated steam gas. ２ The selective absorption of the gas can also be achieved by the above-mentioned method for producing a dehydrated steam gas and CO ２ This is as explained in the recovery method.

[0034] The CO of the present invention ２The recovery system may be a semi-batch type (see FIG. 1) as shown in Examples 1 to 6 below, or a flow type (see FIG. 2, for example, see Example 7). ２ An example of a recovery system is the semi-batch system shown in Figure 1. ２ In the recovery system, the membrane separation absorber supply side 1 is located at the top, and the membrane separation absorber permeation side 2 is located at the bottom. The membrane separation absorber supply side 1 is the side through which the atmosphere (feed gas) flows, and the membrane separation absorber permeation side 2 is the side through which the CO ２ The permeation side 2 of the membrane separation absorber is a closed space where the absorption liquid 7 is placed. ２ An absorbing liquid 7 is disposed in the membrane separation absorber. Between the membrane separation absorber supply side 1 and the membrane separation absorber permeation side 2 (at the boundary between the membrane separation absorber permeation side 2 and the membrane separation absorber supply side 1), an ionic liquid membrane 3 and a gas-permeable support 4 are disposed in this order from the membrane separation absorber supply side 1. ２ The absorption liquid 7 is preferably arranged to be stirrable in order to increase the reaction efficiency. ２ The CO ２ The absorption liquid 7 can be stirred. In this case, a stirring device 6 can be placed below the permeation side 2 of the membrane separation absorber to power the stirring bar 5. The supply side 1 of the membrane separation absorber forms a flow path, through which the supply gas (air) flows in the directions of arrows 9 and 10 while coming into contact with the ionic liquid membrane 3. ２ An example of a recovery system is the flow-through system shown in Figure 2. ２ In the recovery system, the membrane separation absorber supply side 1 is located at the top and the membrane separation absorber permeation side 2 is located at the bottom, similar to Figure 1. The membrane separation absorber supply side 1 is the side through which the atmosphere (feed gas) flows, and the membrane separation absorber permeation side 2 is the side through which the CO ２ This is the side through which the absorption liquid 7 flows. ２ An absorbing liquid 7 is placed in the membrane separation absorber, and an ionic liquid membrane 3 and a gas-permeable support 4 are placed between the membrane separation absorber supply side 1 and the membrane separation absorber permeation side 2 in this order from the membrane separation absorber supply side 1. Between the ionic liquid membrane 3 and the gas-permeable support 4, CO ２A hydrophobic porous membrane (not shown) may be installed to protect against the flow of the absorbing solution 7. The supply side 1 of the membrane separation absorption device forms a flow path through which the supply gas (air) flows in the directions of arrows 9 and 10 while coming into contact with the ionic liquid membrane 3. ２ The absorption liquid 7 may be passed through in a countercurrent, parallel current, or cross current manner relative to the flow of the feed gas. ２ In the capture of atmospheric CO ２ Since the concentration of CO is extremely low, a recycle stream can be added to the feed gas as needed. ２ By combining this with absorption by the absorbing solution 7 (absorption by chemical reaction), ２ This is the CO recovery device of the present invention. ２ The gas recovery system ２ CO absorbed in the absorption solution ２ From the viewpoint of increasing the amount, a flow-through system is preferred.

[0035] The present invention will be described in more detail below based on examples. The materials, amounts used, ratios, processing details, processing procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the present invention should not be construed as being limited by the following examples except as defined in the present invention. In the following examples, min means minute, and s means second.

[0036] [1] CO ２ CO in the atmosphere by a capture device (semi-batch type) ２ Recovery of CO ２ Using the absorption liquid and feed gas, membrane separation (selective removal of water vapor using an ionic liquid membrane) and absorption (CO ２ CO by absorption solution ２ selective absorption of CO ２ Build a capture system to reduce atmospheric CO ２(1) Ionic Liquid Membrane In Examples 1 to 4 and 6, an ionic liquid membrane (composite membrane) was used, which was prepared by impregnating a porous support membrane (Omnipore JGWP (trade name), manufactured by Merck Millipore, made of polytetrafluoroethylene fiber with a hydrophilic surface treatment, diameter 142 mm, pore size 0.2 μm, thickness 65 μm, porosity 80%) with a commercially available ionic liquid and wiping both sides with Kimwipes. In Example 5, in the preparation of the above ionic liquid membrane (composite membrane), instead of the Omnipore JGWP (trade name), Poreflon HPW-010-30 (trade name, manufactured by Sumitomo Electric Fine Polymer, Inc., made of polytetrafluoroethylene fiber with a hydrophilic surface treatment, pore size 0.1 μm, thickness 26 μm, porosity 59%) processed to a diameter of 142 mm, or quantitative filter paper No. An ionic liquid membrane (composite membrane) was used, prepared in the same manner as above, except that a membrane made of cellulose fiber (manufactured by Advantec Co., Ltd., with a retention diameter (pore size) of 4 μm, a thickness of 0.18 mm, and a porosity of 69%) was used, which had been processed to a diameter of 142 mm. The ionic liquids used were as follows:(Hydrophilic ionic liquids) [Emim][Gly]: 1-ethyl-3-methylimidazolium aminoacetate (manufactured by BLD pharm, 96%) [Bmim][DCA]: 1-butyl-3-methylimidazolium dicyanamide (manufactured by Tokyo Chemical Industry Co., Ltd., 96%) [Emim][DCA]: 1-ethyl-3-methylimidazolium dicyanamide (manufactured by Tokyo Chemical Industry Co., Ltd., 97%) (Hydrophobic ionic liquids) [Bmim][PF6]: 1-butyl-3-methylimidazolium hexafluorophosphate (manufactured by Sigma-Aldrich, 98.5%) [Omim][PF6]: 1-methyl-3-n-octylimidazolium hexafluorophosphate (manufactured by Tokyo Chemical Industry Co., Ltd., 98%) [ThtdP][DCA]: trihexyl(tetradecyl)phosphonium dicyanamide (Tokyo Chemical Industry Co., Ltd., 93%) [ThtdP][Cl]: trihexyl(tetradecyl)phosphonium chloride (Tokyo Chemical Industry Co., Ltd., 97%) [ThtdP][NTf2]: trihexyl(tetradecyl)phosphonium bis(trifluoromethylsulfonyl)amide (Sigma-Aldrich, 95%) [ThtdP][Br]: trihexyl(tetradecyl)phosphonium bromide (Ström Chemicals, 95%) (2) CO. ２ Absorbing Solution: Limewater (a saturated aqueous solution of calcium hydroxide, NARICA), 0.1 mol / L or 1 mol / L potassium hydroxide aqueous solution (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and ethylenediamine (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., 99%) were used in appropriate combination. (3) Supply Gas: Laboratory air was supplied as the supply gas using an air compressor (Toshiba Industrial Equipment Systems Corporation, TOSCON FLP type oil-free silent series, model number: FLP85-37TAD5). The gas flow rate of the supply gas was measured using a mass flow meter (Kofloc Corporation, standard mass flow meter, model 3760 series, model: 3765, fitting (body diameter): 1 / 2 SW, target gas: air, flow rate range: 300 SLM, temperature: 20°C). The gas flow rate in this example was 120 L / min. (4) CO ２ CO recovery system shown in Figure 1 ２A CO recovery system (semi-batch type) was constructed. ２ The recovery system has a membrane separation absorber supply side 1 located at the top, where the atmosphere (feed gas) flows, and a membrane separation absorber permeation side 2 located at the bottom, where CO ２ This is the side where the absorption liquid 7 is placed. ２ The membrane separation absorber was filled with an absorption liquid 7, and an ionic liquid membrane 3 and a gas-permeable support 4 were installed in this order from the membrane separation absorber supply side 1 between the membrane separation absorber supply side 1 and the membrane separation absorber permeation side 2 (at the boundary between the membrane separation absorber permeation side 2 and the membrane separation absorber supply side 1). ２ The absorbent 7 is CO ２ The absorption liquid 7 is stirred by a stirrer 5 placed in it, and a stirrer 6 is placed below the permeation side 2 of the membrane separation absorber to power the stirrer 5. Air flows through the flow path on the supply side 1 of the membrane separation absorber in the directions of arrows 9 and 10 while coming into contact with the ionic liquid membrane 3.

[0037] Example 1: CO ２ Example using lime water as an absorption liquid> The main body of the membrane separation absorption system was made of glass (manufactured by Sato Manufacturing Co., Ltd., outer diameter: about 140 mm (outer diameter of flange: about 180 mm), inner diameter: about 130 mm, volume of the membrane separation absorption device supply side 1 (space through which the supply gas flows): about 360 mL, volume of the membrane separation absorption device permeation side 2 (ionic liquid membrane 3, gas permeable support 4 and CO ２ The volume of the space in which the absorption liquid 7 is placed (volume: approximately 380 mL) used was approximately 380 mL. A photograph of the main body of this apparatus is shown in Figure 3. Air from an air compressor installed in the laboratory was supplied through two inlets 29 on the main body of the apparatus, and discharged through two outlets 30 into a draft (local exhaust system) in the laboratory. The ionic liquid membrane 3 was supported by a gas-permeable support 4 (stainless steel mesh). The ionic liquid membrane 3 was fixed with a flange 21 so that the central circular portion with a diameter of 100 mm was in contact with the atmosphere, and the surrounding portion was covered with a packing 20. CO ２ Lime water was used as the absorption liquid 7. About 200 g of lime water was filled in the permeate side 2 of the membrane separation absorber at the bottom of the device. ２During the recovery experiment, the mixture was stirred by a stirrer 6. In Example 1, among the gases contained in the atmosphere that came into contact with the ionic liquid membrane 3, the permeation of water vapor 11 was selectively blocked by the ionic liquid membrane 3, and the permeation of CO ２ 12 passes through the ionic liquid membrane 3 and CO ２ It is absorbed in the absorbing solution 7. Absorbed CO ２ The calcium hydroxide reacts with the limewater to produce calcium carbonate, which solidifies and precipitates in the limewater. The experiment lasted for two hours. The mass of the apparatus was measured before air was supplied (before the experiment began) and after the experiment, and the mass change of the apparatus (the mass before the experiment minus the mass after the experiment) was calculated. The mass of the apparatus was measured with the hoses connected to the two inlets 29 and two outlets 30 of the apparatus removed. After the experiment, calcium carbonate was recovered from the mixture of limewater and calcium carbonate by filtration using Omnipore JGWP (trade name, diameter 47 mm, pore size 0.2 μm) manufactured by Merck Millipore. The mass of the recovered calcium carbonate after drying was measured. The results are shown in Table 1 below.

[0038]

[0039] (Notes for the table) Amount of IL in the membrane: This refers to the amount of ionic liquid impregnated in the ionic liquid membrane 3. Amount of calcium carbonate: The solid content obtained in the experiment was calcium carbonate (CaCO ３ ) Therefore, the mass of the solid obtained in the experiment is listed. This also applies to the following tables.

[0040] Regardless of which ionic liquid is used, the ionic liquid membrane 3 can remove water vapor 11 from the atmosphere with little energy while reducing CO2 at an extremely low concentration of about 400 ppm in the atmosphere. ２ The gas was selectively collected and recovered as calcium carbonate. ２is an acidic gas and easily dissolves in hydrophilic ionic liquids. Therefore, it is thought that the amount of calcium carbonate was greatest when the ionic liquid membrane 3 of 1-ethyl-3-methylimidazolium aminoacetate [Emim][Gly] was used. On the other hand, although hydrophilic ionic liquids selectively block the permeation of water molecules (water vapor 11) in membrane separation, they are relatively permeable to water molecules compared to hydrophobic ionic liquids. Therefore, CO ２ The greatest decrease in device mass is believed to be due to the evaporation of the solvent in the absorption liquid 7. When the hydrophobic ionic liquids 1-butyl-3-methylimidazolium hexafluorophosphate [Bmim][PF6], 1-methyl-3-n-octylimidazolium hexafluorophosphate [Omim][PF6], or trihexyl(tetradecyl)phosphonium dicyanamide [ThtdP][DCA] were used in the membrane, the amount of calcium carbonate obtained was less than when a hydrophilic ionic liquid was used, but the decrease in device mass in the experiment was small. In particular, trihexyl(tetradecyl)phosphonium dicyanamide [ThtdP][DCA] is a hydrophobic ionic liquid that barely dissolves water, and therefore the decrease in device mass in the experiment was the smallest. Furthermore, it was possible to recover an amount of calcium carbonate comparable to that recovered when 1-butyl-3-methylimidazolium hexafluorophosphate [Bmim][PF6] or 1-methyl-3-n-octylimidazolium hexafluorophosphate [Omim][PF6] was used.

[0041] Example 2: CO ２ Example in which a 0.1 mol / L potassium hydroxide aqueous solution was used as an absorption liquid> In Example 1 above, the ionic liquid used, CO ２ The same procedure as in Example 1 was carried out to absorb CO from the atmosphere, except that the absorbent 7 was changed as follows: ２ The ionic liquid impregnated into the ionic liquid membrane 3 was either 1-ethyl-3-methylimidazolium aminoacetate [Emim][Gly], a hydrophilic ionic liquid, or trihexyl(tetradecyl)phosphonium dicyanamide [ThtdP][DCA], a hydrophobic ionic liquid. ２A 0.1 mol / L aqueous potassium hydroxide solution was used as the absorption solution 7. The amount of the solution was about 200 g or about 250 g. ２ During the CO recovery experiment, ２ The absorption liquid 7 was stirred with a stirrer. In Example 2, among the gases contained in the air that came into contact with the ionic liquid membrane 3, the permeation of water vapor 11 was selectively blocked by the ionic liquid membrane 3, and CO ２ 12 passes through the ionic liquid membrane 3 and CO ２ It is absorbed in the absorbing solution 7. Absorbed CO ２ reacts with potassium hydroxide to form potassium carbonate, CO ２ It is present in the absorption liquid 7. ２ CO in absorption solution 7 ２ In order to determine the amount of calcium carbonate, lime water was mixed with a portion of the recovered potassium hydroxide aqueous solution, and potassium carbonate was precipitated as calcium carbonate. The experiment lasted for 2 hours. The change in mass of the apparatus (the mass before the experiment minus the mass after the experiment) was determined in the same manner as in Example 1. Furthermore, calcium carbonate was recovered from the mixture of lime water, potassium hydroxide aqueous solution, and calcium carbonate after the experiment by filtration using Omnipore JGWP (trade name, diameter 47 mm, pore size 0.2 μm) manufactured by Merck Millipore. The mass of the recovered calcium carbonate after drying was measured. The results are shown in Table 2 below.

[0042]

[0043] CO ２ It was found that the mass change (loss of mass) of the device in the experiment was smaller when trihexyl(tetradecyl)phosphonium dicyanamide [ThtdP][DCA] was used than when 1-ethyl-3-methylimidazolium aminoacetate [Emim][Gly] was used, regardless of whether the amount of absorbent solution 7 was about 200 g or about 250 g. In other words, the use of an ionic liquid membrane 3 containing a hydrophobic ionic liquid resulted in a smaller mass change (loss of mass) of the device in the experiment. ２It was shown that it is possible to suppress the evaporation of water from the potassium hydroxide aqueous solution, which is the absorption solution 7. In addition, regardless of whether 1-ethyl-3-methylimidazolium aminoacetate [Emim][Gly] or trihexyl(tetradecyl)phosphonium dicyanamide [ThtdP][DCA] is used, the amount of calcium carbonate obtained is about the same, which indicates that CO from the atmosphere can be effectively prevented. ２ The usefulness of hydrophobic ionic liquids in recovery was demonstrated.

[0044] (CO in the atmosphere ２ Recovery rate and apparent CO ２ Rough calculation of permeance) CO listed in Table 2 above ２ The recovery rate was calculated as follows: ２ Recovery rate = (CaCO obtained in the experiment) ３ (amount of CO) / X) × 100% In the above formula, X is CO ２ CaCO corresponding to the cumulative flow rate of ３ The amount of CO is calculated as follows: ２ Total flow rate = CO in the supply gas (atmosphere) ２ Concentration × supply gas flow rate × gas supply time = 0.0004 × 120 L / min × 120 min = 5.8 L CO ２ CaCO corresponding to the cumulative flow rate of ３ Amount of CO ２ Accumulated flow rate / molar volume × CaCO ３ Molar mass = 5.8 L / (24.0 L mol －１ )×100.1g・mol －１ = 24.2 g Also, the apparent CO ２ The approximate value of the permeance was calculated as follows: ２ Permeance = CO ２ Time average value of movement amount / CO ２ Partial pressure of CO ２ The time average value of the movement amount is (CO ２ (number of moles transferred) = (CaCO ３ (number of moles recovered) so CO ２ Time average value of the amount of movement = CaCO obtained in the experiment ３ Amount of CaCO３ For example, in an example using [Emim][Gly] and a 0.1 mol / L KOH aqueous solution of about 200 g, the CaCO ３ The amount of 0.13 g, the membrane area (opening diameter 100 mm) = π × (5 cm) ２ = 78.5 cm ２ , CO ２ The partial pressure of CO is 0.04 kPa. ２ Recovery rate = (0.13 / 24.2) x 100% = 0.537%, which is the CO in the atmosphere. ２ It was found that 0.5% of the CO ２ The time average value of the amount of movement was 0.13 g / 100.1 g mol －１ / 7200s / (78.5 x 10 －４ m ２ ) = 2.3 x 10 －５ mol / (m ２ s), and apparent CO ２ Permeance is 2.3 x 10 －５ mol / (m ２ ・s) / 0.04kPa=5.7×10 －４ mol / (m ２ .s.kPa).

[0045] Example 3: CO ２ Example of using liquid ethylenediamine as an absorption liquid> In Example 1, the ionic liquid used, CO ２ The same procedure as in Example 1 was carried out to absorb CO from the atmosphere, except that the absorbent 7 was changed as follows: ２ However, CO ２ In order to suppress the evaporation of the solvent in the absorbing solution 7, the membrane separation absorption device main body (permeation side) 2 is ２ External cooling was performed by immersing the absorption liquid 7 up to the liquid surface in cooling water (approximately 7°C). The ionic liquid impregnated into the ionic liquid membrane 3 was trihexyl(tetradecyl)phosphonium dicyanamide [ThtdP][DCA], a hydrophobic ionic liquid, in the experiment. ２Ethylenediamine was used as the absorption liquid 7. The amount of the liquid absorbed was about 200 g. ２ During the CO recovery experiment, ２ The absorbing solution 7 was stirred with a stirrer. In Example 3, among the gases contained in the supply gas that came into contact with the ionic liquid membrane 3, the passage of water vapor 11 was selectively blocked by the ionic liquid membrane 3, and CO ２ 12 passes through the ionic liquid membrane 3 and CO ２ It is absorbed in the absorbing solution 7. Absorbed CO ２ As shown in the following scheme, reacts with ethylenediamine (EDA) to form ethylenediaminecarbamic acid (EDA-CA) and CO ２ It is present in the absorption liquid 7.

[0046]

[0047] The experiment time was 2 hours. The mass change of the device (the mass before the experiment minus the mass after the experiment) was calculated in the same manner as in Example 1. ２ CO in absorption solution 7 ２ In order to determine the amount of EDA, a portion of the recovered absorption liquid was sampled and the EDA was removed using an evaporator. The solid remaining in the eggplant-shaped flask was considered to be EDA-CA, and its mass was measured. The results are shown in Table 3 below.

[0048]

[0049] Although EDA has a lower vapor pressure than water, a mass loss was observed after the experiment. On the other hand, the appearance of the ionic liquid membrane 3 after the experiment was almost the same as at the start of the experiment. In Example 3 above, the ionic liquid was changed to hydrophilic 1-ethyl-3-methylimidazolium aminoacetate [Emim][Gly], and an ionic liquid membrane 3 was used. The membrane separation absorption device main body (permeation side) 2 was not externally cooled (not immersed in cooling water), and CO ２ In the same manner as in Example 3, CO 2 was extracted from the atmosphere, except that EDA cooled to 12°C was used as the absorption solution 7. ２ A recovery experiment was conducted to capture CO from the atmosphere. ２In the recovery experiment, a spotted pattern appeared on the ionic liquid membrane 3 during the experiment, and it was confirmed that EDA vapor was mixed into the ionic liquid membrane 3. In other words, by using the ionic liquid membrane 3 of a hydrophobic ionic liquid, CO ２ It was confirmed that the permeation of the solvent vapor 13 of the absorption liquid through the membrane could be suppressed. In addition, even with a hydrophobic ionic liquid, the generation of droplets that are thought to be derived from EDA was confirmed in the ionic liquid membrane 3 during the experiment when 1-butyl-3-methylimidazolium hexafluorophosphate [Bmim][PF6] was used. ２ From the viewpoint of suppressing the permeation of the solvent vapor 13 of the absorption liquid through the membrane, it was found that it is necessary to use an ionic liquid membrane 3 of a hydrophobic ionic liquid (specifically, 1-methyl-3-n-octylimidazolium hexafluorophosphate [Omim][PF6] or trihexyl(tetradecyl)phosphonium bis(trifluoromethylsulfonyl)amide [ThtdP][NTf2]) that exhibits hydrophobicity comparable to or higher than that of trihexyl(tetradecyl)phosphonium dicyanamide [ThtdP][DCA].

[0050] (CO in the atmosphere ２ Recovery rate and apparent CO ２ Rough calculation of permeance) CO listed in Table 3 above ２ Recovery rate and apparent CO ２ Regarding permeance, the CO ２ Recovery rate and apparent CO ２ In the same manner as for the permeance, the approximate values ​​were calculated as follows: ２ Recovery rate and apparent CO ２ The permeance is calculated in the same manner. The amount of solid obtained in the experiment is 1.0 g, and the membrane area (the opening has a diameter of 100 mm) = π × (5 cm). ２ = 78.5 cm ２ , CO ２ The partial pressure of CO is 0.04 kPa. ２ Accumulated flow rate = 0.0004 x 120 L / min x 120 min = 5.8 L CO ２ The amount of EDA-CA corresponding to the cumulative flow rate = 5.8 L / (24.0 L mol－１ )×104.1g・mol －１ = 25.2 g Assuming that all the solids obtained in the experiment are EDA-CA, CO ２ Recovery rate = (1.0 / 25.2) x 100% = 3.9%, which is the CO in the atmosphere. ２ It was found that 4% of the CO ２ The time average value of the movement amount is (CO ２ (Number of moles transferred) = (Number of moles recovered of EDA-CA), so 1.0 g / 104.1 g mol －１ / 7200s / (78.5 x 10 －４ m ２ ) = 1.7 x 10 －４ mol / (m ２ s), and apparent CO ２ Permeance is 1.7 x 10 －４ mol / (m ２ ・s) / 0.04kPa=4.2×10 －３ mol / (m ２ .s.kPa).

[0051] Example 4: CO ２ Example in which a 1 mol / L potassium hydroxide aqueous solution was used as an absorption liquid In the above Example 2, the ionic liquid to be used, the fixing of the ionic liquid membrane 3 by the flange 21, and the CO ２ The same procedure as in Example 2 was carried out to absorb CO from the atmosphere, except that the absorbent 7 was changed as follows: ２ A CO recovery experiment was conducted. Hydrophilic ionic liquids, [Emim][Gly], [Bmim][DCA], or [Emim][DCA], or hydrophobic ionic liquids, [ThtdP][DCA], [ThtdP][Cl], [ThtdP][NTf2], [ThtdP][Br], [Bmim][PF6], or [Omim][PF6], were used as the ionic liquids impregnated into the ionic liquid membrane 3. The 70 mm diameter circular central portion of the ionic liquid membrane 3 was exposed to the atmosphere, and the surrounding area was covered with packing 20 and secured by a flange 21. ２A 1 mol / L potassium hydroxide aqueous solution was used as the absorption solution 7. The amount of the solution was set to about 250 g. ２ During the CO recovery experiment, ２ The absorption solution 7 was stirred with a stirrer. The experiment time was 2 hours. ２ Lime water was mixed with a part of the absorption solution 7, the change in mass of the apparatus (the mass before the experiment minus the mass after the experiment) was calculated, and the mass of the calcium carbonate recovered by filtration after drying was measured. The results are shown in Tables 4-1 and 4-2 below and in FIG. 4.

[0052]

[0053]

[0054] Tables 4-1 and 4-2 and FIG. 4 reveal the following. When hydrophilic ionic liquids 1-ethyl-3-methylimidazolium aminoacetate [Emim][Gly], 1-butyl-3-methylimidazolium dicyanamide [Bmim][DCA], or 1-ethyl-3-methylimidazolium dicyanamide [Emim][DCA] were used, the mass change (mass loss) of the device in the experiment was -0.6 g or -1.0 g. In contrast, when hydrophobic ionic liquids were used, the mass change (mass loss) of the device in the experiment was small, ranging from -0.1 to -0.4 g. By using hydrophobic ionic liquids, ２It was found that the permeation of water vapor 11 evaporated from the potassium hydroxide aqueous solution, which is the absorption liquid 7, through the ionic liquid membrane 3 was more effectively suppressed. The following further becomes clear from a comparison with the case where a hydrophobic ionic liquid is used. Comparing the results for the ionic liquid with trihexyl(tetradecyl)phosphonium cation [ThtdP], when trihexyl(tetradecyl)phosphonium bis(trifluoromethylsulfonyl)amide [ThtdP][NTf2] or trihexyl(tetradecyl)phosphonium dicyanamide [ThtdP][DCA] was used, the mass loss of the experimental apparatus was smaller (0.1 g compared to 0.3 g) than when trihexyl(tetradecyl)phosphonium chloride [ThtdP][Cl] or trihexyl(tetradecyl)phosphonium bromide [ThtdP][Br] was used. In particular, when trihexyl(tetradecyl)phosphonium bis(trifluoromethylsulfonyl)amide [ThtdP][NTf2] was used, the mass loss of CaCO ３ The recovery amount of trihexyl(tetradecyl)phosphonium bis(trifluoromethylsulfonyl)amide [ThtdP][NTf2] was also the largest at 1.06 g. ２ Suppression of evaporation amount of absorbent 7 and CO ２ From the viewpoint of being the best at achieving both high yield and high recovery, it is judged to be a desirable ionic liquid. On the other hand, considering the price (reagent) of ionic liquids, the price of trihexyl(tetradecyl)phosphonium bis(trifluoromethylsulfonyl)amide [ThtdP][NTf2] is 11,500 yen / 5g. Therefore, the cheaper trihexyl(tetradecyl)phosphonium chloride [ThtdP][Cl] (2,400 yen / 5g), trihexyl(tetradecyl)phosphonium bromide [ThtdP][Br] (13,300 yen / 10g), and trihexyl(tetradecyl)phosphonium dicyanamide [ThtdP][DCA] (3,500 yen / 5g) are ２ Considering the cost of the entire recovery system, ionic liquids are a viable option. Similarly, 1-methyl-3-n-octylimidazolium hexafluorophosphate [Omim][PF6] (6,500 yen / 5g) is also a viable option for CO ２Suppression of evaporation amount of absorbent 7 and CO ２ Considering both the compatibility with recovery and the price (reagent) of ionic liquids, this is considered to be a desirable ionic liquid.

[0055] Example 5: When Poreflon (trade name) or quantitative filter paper No. 7 was used as the porous support membrane constituting the ionic liquid membrane. CO from the atmosphere was removed in the same manner as in Example 4, except that the ionic liquid membrane 3 used was changed as follows. ２ As described above, Poreflon HPW-010-30 (trade name) or quantitative filter paper No. 7 was used as the ionic liquid membrane 3, and trihexyl(tetradecyl)phosphonium dicyanamide [ThtdP][DCA] was used as the ionic liquid. ２ Lime water was mixed with a portion of the absorption liquid 7, the change in mass of the apparatus (the mass before the experiment minus the mass after the experiment) was calculated, and the dried mass of calcium carbonate recovered by filtration was measured. The results are shown in Table 5 below. As shown in Table 5, when Poreflon HPW-010-30 (trade name, manufactured by Sumitomo Electric Fine Polymers, Inc., thickness 26 μm) was used as the porous support membrane constituting the ionic liquid membrane 3, the mass of CaCO ３ The recovered amount was 0.64 g, and when quantitative filter paper No. 7 (manufactured by Advantec Co., Ltd., thickness 0.18 mm) was used as the porous support membrane constituting the ionic liquid membrane 3, the amount of CaCO ３ The recovered amount was 0.29 g. When the ionic liquid membrane 3 using any of the porous support membranes was used, the CO ２ was able to be recovered.

[0056]

[0057] Example 6: Room temperature ethylenediamine used as an absorption liquid In Example 3, the ionic liquid used, the fixing of the ionic liquid membrane 3 by the flange 21, and the CO ２ The same procedure as in Example 3 was carried out to absorb CO from the atmosphere, except that the absorbent 7 was changed as follows: ２A recovery experiment was conducted. Experiments were conducted using 1-methyl-3-n-octylimidazolium hexafluorophosphate [Omim][PF6], trihexyl(tetradecyl)phosphonium dicyanamide [ThtdP][DCA], or trihexyl(tetradecyl)phosphonium bis(trifluoromethylsulfonyl)amide [ThtdP][NTf2] as the hydrophobic ionic liquid to be impregnated into the ionic liquid membrane 3. The ionic liquid membrane 3 was fixed in place by a flange 21, with a 70 mm diameter circular portion at the center of the membrane exposed to the air, and the surrounding area covered with a packing 20, in the same manner as in Example 4. ２ The experiment was carried out using ethylenediamine (EDA) at room temperature (20 to 21°C) as the absorption liquid 7, without external cooling of the membrane separation absorption device main body (permeation side) 2 (without immersion in cooling water). The amount of EDA soaked was about 225g. ２ During the CO recovery experiment, ２ The absorbing solution 7 was stirred with a stirrer. The experiment time was 2 hours. In the same manner as in Example 3, the mass change of the apparatus (the mass before the experiment minus the mass after the experiment) was calculated, and the CO ２ The mass of the solid content (ethylenediaminecarbamic acid) obtained by evaporating a portion of the absorption solution 7 was measured. The results are shown in Table 6 below. ２ When room temperature EDA was used as the absorption liquid 7, the part of the ionic liquid membrane 3 that was in contact with the atmosphere (the circular part with a diameter of 70 mm at the center) maintained its appearance almost the same as when the experiment started, but the surrounding area (the part covered by the packing 20) showed a change in appearance due to the inclusion of EDA after the experiment. Comparing the results for the three types of ionic liquids, when 1-methyl-3-n-octylimidazolium hexafluorophosphate [Omim][PF6] was used, the appearance of CaCO ３ The recovery amount was 0.33 g, whereas the recovery amount of CaCO3 when trihexyl(tetradecyl)phosphonium dicyanamide [ThtdP][DCA] or trihexyl(tetradecyl)phosphonium bis(trifluoromethylsulfonyl)amide [ThtdP][NTf2] was 0.33 g. ３The recovery amount is large, 0.52 g or 0.66 g, and the amount of CO in the atmosphere ２ We were able to recover more (1.6 to 2 times the amount).

[0058]

[0059] [2] CO ２ CO in the atmosphere by a recovery device (flow type) ２ Recovery of CO ２ Using the absorption liquid and feed gas, membrane separation (selective removal of water vapor using an ionic liquid membrane) and absorption (CO ２ CO by absorption solution ２ selective absorption of CO ２ Build a capture system to reduce atmospheric CO ２ (1) Ionic liquid membrane Poreflon HPW-010-30 (trade name, manufactured by Sumitomo Electric Fine Polymers, Inc., hydrophilic membrane, width 315 mm × length 220 mm, hydrophilic membrane, pore size 0.1 μm, thickness 24 μm) was impregnated with trihexyl(tetradecyl)phosphonium dicyanamide [ThtdP][DCA] (manufactured by Tokyo Chemical Industry Co., Ltd., 93%) and wiped both sides with Kimwipes to prepare an ionic liquid membrane (composite membrane). (2) CO ２ Absorbing solution: 0.1 mol / L potassium hydroxide aqueous solution (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.). (3) Supply gas: CO ２ CO in the atmosphere by a capture device (semi-batch type) ２ (3) The recovery of CO was the same except that the gas flow rate of the supply gas was changed to 30 L / min. ２ Absorbent supply CO ２ The supply pump for the absorption liquid was a constant-rate pump (manufactured by Eyela, model: MP-2000, peristaltic tube pump). ２ The absorbent is discharged, and a recycle section is provided in addition to the outlet valve. A constant rate liquid pump (manufactured by Eyela, RP-2000, model: roller pump) was used as the recycle pump. (5) CO ２ CO recovery system shown in Figure 2 ２ A CO recovery system (circulating type) was constructed.２ The recovery system has a membrane separation absorber supply side 1 located at the top, where the atmosphere (feed gas) flows, and a membrane separation absorber permeation side 2 located at the bottom, where CO ２ This is the side through which the absorption liquid 7 flows. ２ An absorbing liquid 7 was placed, and an ionic liquid membrane 3 and a gas-permeable support 4 were placed in this order from the membrane separation absorber supply side 1 between the membrane separation absorber supply side 1 and the membrane separation absorber permeation side 2 (the boundary between the membrane separation absorber permeation side 2 and the membrane separation absorber supply side 1). ２ An absorbing liquid 7 flows through the flow path on the supply side 1 of the membrane separation absorption device. Air flows through the flow path in the directions of arrows 9 and 10 while coming into contact with the ionic liquid membrane 3.

[0060] Example 7: CO ２ CO in the atmosphere by semi-batch operation using a recovery device (flow-through type) ２ Recovery of CO > The membrane separation absorption system was of a type that used a flat membrane ionic liquid membrane 3. The main body of the membrane separation absorption system has a membrane separation absorber supply side 1 and a membrane separation absorber permeation side 2 in a flat plate structure, the membrane separation absorber supply side 1 being made of acrylic and the membrane separation absorber permeation side 2 being made of stainless steel, both with external dimensions of 360 mm width x 240 mm length, atmosphere inside the flat plate of the membrane separation absorber supply side 1, and CO ２ The membrane separation absorber was provided with a flow path through which the absorbing solution 7 flows. The atmospheric air was supplied from one end of the upper surface of the supply side 1 of the membrane separation absorber and discharged from the other end. ２ The absorbent 7 was supplied from one end of the bottom of the permeation side 2 of the membrane separation absorber and discharged from the other end. The gas-permeable support 4 was made of stainless steel mesh and was installed at the upper end of the permeation side 2 of the membrane separation absorber. The ionic liquid membrane 3 was sandwiched between the supply side 1 of the membrane separation absorber and the permeation side 2 of the membrane separation absorber via a packing (as shown in FIG. 3). ２ (See the packing 20 in the membrane separation absorption device body of the recovery device (semi-batch type).) Also, a CO ２A porous membrane (hydrophobic) was installed for the purpose of protection against the flow (distribution) of the absorption liquid 7. The ionic liquid membrane 3 was fixed together with the gas-permeable support 4 and the porous membrane (hydrophobic) for protection, with packing covering the membrane edges. Therefore, the gas-liquid contact area was an area of ​​260 mm wide x 180 mm long in the center of the ionic liquid membrane 3. The porous membrane (hydrophobic) for protection was Poreflon HP-010-30 (trade name, manufactured by Sumitomo Electric Fine Polymers, Inc., 330 mm wide x 270 mm long, hydrophobic membrane, pore size 0.1 μm, thickness 32.2 μm). The experiment time was 2 hours. In Example 7, atmospheric CO was measured by semi-batch operation. ２ Specifically, the CO was collected from the supply pump while the outlet valve of the permeation side 2 of the membrane separation absorption device was closed. ２ The absorption liquid 7 is supplied to the flow path. ２ After filling with the absorption liquid 7, the experiment was started. ２ The absorption solution 7 is recycled to remove CO from the atmosphere. ２ After the experiment was completed, the outlet valve of the permeation side 2 of the membrane separation absorption device was opened to measure the CO ２ The absorbent 7 was recovered. ２ Lime water was mixed with a part of the absorption solution 7, and the mass of calcium carbonate recovered by filtration after drying was measured. The results are shown in Table 7 below.

[0061]

[0062] As shown in Table 7, CO ２ The amount of CO recovered relative to the amount of potassium hydroxide aqueous solution supplied (approximately 150 g) as the absorption solution 7 ２ Although the amount of the absorbing liquid 7 is small, ２ Even when a recovery device (flow type) is used, CaCO ３ It was confirmed that 0.23 g of the compound could be recovered.

[0063] [3] Evaluation of the selective removal performance of ionic liquid membranes against atmospheric water vapor [Experimental method] In Example 8, to evaluate the blocking performance (selective removal performance) of ionic liquid membranes against atmospheric water vapor, a test was conducted using the ionic liquid membrane, experimental apparatus, absorption liquid, and measurement conditions set as follows. (Ionic liquid membrane) First, to prepare an ionic liquid membrane, trihexyl(tetradecyl)phosphonium bis(trifluoromethylsulfonyl)amide ([ThtdP][NTf2], manufactured by Sigma-Aldrich, purity 95%) was used as the ionic liquid, and Omnipore JGWP (trade name, made by Merck Millipore, made of PTFE (polytetrafluoroethylene) fiber with a hydrophilic surface treatment, with a diameter of 142 mm, a pore size of 0.2 μm, a thickness of 65 μm, and a porosity of approximately 80%) was used as the porous support membrane. After uniformly impregnating the porous support membrane with the ionic liquid, both sides were gently wiped with Kimwipes to remove excess ionic liquid, producing a uniform ionic liquid membrane. (Experimental Apparatus) A glass reactor manufactured by Sato Seisakusho Co., Ltd. was used as the vessel for placing the ionic liquid membrane. This vessel was a flanged cylindrical vessel with an outer diameter of approximately 140 mm (flange outer diameter: approximately 180 mm) and an inner diameter of approximately 130 mm. The volume of the permeate side space (the volume of the vessel, excluding the space occupied by the absorption liquid, and the gas space) was approximately 360 mL. In the experiment, the bottom of this vessel was filled with 200 g of absorption liquid, and the ionic liquid membrane was placed in close contact with the opening of the vessel and left stationary. This vessel was used as an apparatus for "SILMs conditions." Note that the central circular portion of the ionic liquid membrane, 130 mm in diameter, was in contact with the atmosphere, and the surrounding area was covered with packing. To ensure the tightness of the container, 50 mm wide fluororesin adhesive tape manufactured by TRUSCO Corporation was used on the contact surface between the flange of the container and the packing to prevent leakage or intrusion of outside air. A 300 mL beaker (model number: 2-5091-05, manufactured by AS ONE Corporation, outer diameter of the body: 75 mm) was filled with 200 g of the absorbing solution and allowed to stand. An ionic liquid membrane was not installed, and the absorbing solution was directly exposed to the atmosphere. This was used as an apparatus under "bare conditions." (Absorbing Solution) Triethylene glycol (TEG) for analysis manufactured by Tokyo Chemical Industry Co., Ltd. was used as the absorbing solution.The initial moisture content of the absorption solution was measured by coulometric titration using a Karl Fischer moisture meter (model number: MKC-710M, manufactured by Kyoto Electronics Manufacturing Co., Ltd.) and confirmed to be 0.55% by mass. (Measurement conditions) The glass reaction vessel and the 300 mL beaker were each left stationary in the same space in a laboratory for 24 hours, and a comparative experiment was conducted. The temperature and relative humidity of the indoor environment during the experiment were measured and recorded every hour using a K-type thermocouple (model number: EA742HD-11, manufactured by AS ONE Corporation) and a humidity sensor (model number: HC2A-S, manufactured by TGK Corporation). As a result, the average temperature and average relative humidity during the experiment (during the period of exposure to the atmosphere) were approximately 23.6°C and 65%, respectively.

[0064] After the exposure, the moisture content of the absorption liquid (TEG sample) in each device was measured using the Karl Fischer moisture meter described above. Regarding the moisture content of the TEG sample collected under "bare conditions," approximately 0.2 mL was sampled and titrated using a 0.5 mL microsyringe (MS-GAN050, manufactured by Ito Seisakusho Co., Ltd.). Regarding the moisture content of the TEG sample collected under "SILMs conditions" and the moisture content of the TEG sample before the experiment (the initial moisture content described above), approximately 2 mL was sampled and titrated using a 5 mL microsyringe (MS-GAN500, manufactured by Ito Seisakusho Co., Ltd.).

[0065] [Experimental Results] The results are shown in Table 8 and FIG.

[0066]

[0067] The initial moisture content of the TEG sample before the experiment was 0.55% by mass. In the TEG sample recovered under "SILMs conditions" after 24 hours of exposure, the moisture content was only 0.92% by mass, and the amount of water contamination was 0.74 g. In contrast, in the TEG sample recovered under "bare conditions" without an ionic liquid membrane after 24 hours of exposure, the moisture content was as high as 8.33% by mass, and the amount of water contamination reached 15.56 g. These results demonstrate that the presence of an ionic liquid membrane can suppress moisture contamination by approximately 95% (= (15.56 g - 0.74 g) / 15.56 g x 100%) compared to the case without an ionic liquid membrane, confirming that the ionic liquid membrane achieves a high level of blocking the permeation of atmospheric water vapor. This demonstrates that the ionic liquid membrane of the present invention can block the permeation of water vapor in a high-humidity environment, and that the CO2 membrane of the present invention equipped with an ionic liquid membrane can suppress water vapor permeation. ２ In the gas recovery system, CO ２ It was shown that the incorporation of water into the absorption liquid can be suppressed.

[0068] While the present invention has been described in connection with embodiments thereof, we do not intend to limit our invention to any of the details of the description unless otherwise specified, and believe that the claims should be construed broadly without departing from the spirit and scope of the invention as set forth in the appended claims.

[0069] This application claims priority based on Japanese Patent Application No. 2024-085177, filed on May 24, 2024, the contents of which are incorporated herein by reference as part of the present specification.

[0070] 1: Feed side of membrane separation absorber 2: Permeate side of membrane separation absorber 3: Ionic liquid membrane 4: Gas-permeable support 5: Stirrer 6: Stirrer (power source for stirrer 5) 7: CO ２ Absorbent (liquid phase) 8: Gas on the permeation side of the device (gas phase) 9: Supply gas (device inlet side) 10: Supply gas (device outlet side) 11: Water vapor, rain, snow 12: CO ２ 13:CO ２ Absorption liquid solvent vapor 20: Packing 21: Flange 29: Inlet 30: Outlet

Claims

1. A method for producing dehydrated steam gas, comprising passing air through an ionic liquid membrane to selectively remove water vapor from the air.

2. The method for producing dehydrated vapor gas according to claim 1, wherein the total gas pressure on the side of the ionic liquid membrane that is in contact with the atmosphere is the same as the total gas pressure on the side opposite to the side that is in contact with the atmosphere.

3. The aforementioned dehydrated steam gas is CO ２ A method for producing dehydrated steam gas according to claim 2, comprising at least a gas.

4. The method for producing dehydrated steam gas according to claim 3, wherein the ionic liquid membrane is a composite membrane formed by impregnating a porous support membrane with an ionic liquid.

5. The method for producing dehydrated steam gas according to claim 4, wherein the ionic liquid constituting the ionic liquid membrane includes at least one selected from tetraalkylphosphonium salts having an alkyl group with 5 or more carbon atoms, and imidazolium salts having an alkyl group with 5 or more carbon atoms.

6. The method for producing dehydrated steam gas according to claim 5, wherein the ionic liquid constituting the ionic liquid membrane includes at least one selected from 1-ethyl-3-methylimidazolium aminoacetate, 1-butyl-3-methylimidazolium dicyanamide, 1-ethyl-3-methylimidazolium dicyanamide, 1-butyl-3-methylimidazolium hexafluorophosphate, trihexyl(tetradecyl)phosphonium bis(trifluoromethylsulfonyl)amide, trihexyl(tetradecyl)phosphonium bromide, trihexyl(tetradecyl)phosphonium chloride, trihexyl(tetradecyl)phosphonium dicyanamide, and 1-methyl-3-n-octylimidazolium hexafluorophosphate.

7. Dehydrated steam gas obtained by the method for producing dehydrated steam gas according to any one of claims 1 to 6, and CO in the dehydrated steam gas ２ CO selectively absorbs gas ２ By bringing it into contact with the absorbent liquid, CO ２ CO2 ２ How to recover it.

8. The aforementioned CO ２ The CO2 according to claim 7, wherein the absorbent solution comprises an aqueous solution of a metal hydroxide and at least one of a liquid amine. ２ How to recover it.

9. The above CO ２ The absorption liquid contains at least one of an aqueous calcium hydroxide solution, an aqueous potassium hydroxide solution, and liquid ethylenediamine. The method for recovering CO according to claim 8 ２ .

10. CO as described in claim 7 ２ By going through the recovery method, the CO ２ CO in the absorbent solution ２ absorbent and the CO ２ This includes obtaining a chemical reaction product with CO ２ and CO ２ A method for producing chemical reaction products with an absorbent.

11. The aforementioned CO ２ and CO ２ The CO2 according to claim 10, wherein the chemical reaction product with the absorbent is calcium carbonate or carbamic acid. ２ and CO ２ A method for producing chemical reaction products with an absorbent.

12. CO in the atmosphere ２ It is a gas recovery system, The aforementioned CO ２ The gas recovery system consists of an air supply side through which air flows, and CO2. ２ CO2 ２ The absorption side is separated by an ionic liquid film, The air flowing through the aforementioned air supply side has water vapor removed by the action of the ionic liquid film, becoming dehydrated steam gas, which is then CO2. ２ It moves to the absorption side, and the CO ２ The absorbent liquid is CO in the dehydrated vapor gas. ２ CO selectively absorbs gas. ２ Gas recovery system.

13. The CO2 film described in claim 12 is disposed on a gas-permeable support. ２ Gas recovery system.

14. An ionic liquid membrane for allowing air to pass through and selectively blocking the permeation of water vapor in the air.

15. CO in the atmosphere ２ An ionic liquid membrane according to claim 14 for permeating gas.