Acidic gas-absorbing liquid and acidic gas reduction method

Abstract

An acidic gas-absorbing liquid that reversibly absorbs and desorbs carbon dioxide, wherein the acidic gas-absorbing liquid contains an organic solvent and an amine compound, and the organic solvent has a Log S value of 0 or less and a vapor pressure of 0.1 to 300.0 Pa at 25°C.

Description

Acid gas absorption solution and method for reducing acid gas

[0001] The present invention relates to an acidic gas absorbent and an acidic gas reduction method, and more particularly to an acidic gas absorbent capable of sufficiently suppressing volatility and hygroscopicity, and an acidic gas reduction method using the absorbent.

[0002] For example, in order to reduce greenhouse gases (carbon dioxide, etc.), a method is known for recovering acidic gases, such as carbon dioxide, from gases. This method involves using an acidic gas absorbent (hereinafter also simply called an absorbent) containing an amine compound and an organic solvent to absorb and separate the acidic gas, and then recovering the absorbed acidic gas by desorption from the absorbent by heating. Such an absorbent utilizes the reversible reaction of amine salt formation and regeneration by the amine compound, and is also called a chemical absorbent.

[0003] In the above-mentioned methods for recovering acidic gases, various methods have been proposed to reduce the energy required for heating when desorbing the acidic gas from the absorbent, from the viewpoint of energy conservation. For example, Patent Document 1 proposes an acidic gas absorbent by selecting a combination of an amine compound and an alcohol such as 1-butanol or 1-pentanol, or an ether such as diethylene glycol diethyl ether. Furthermore, Patent Document 2 proposes an acidic gas absorbent using a primary amine compound and an organic solvent.

[0004] Japanese Patent Publication No. 6460974, Japanese Unexamined Patent Publication No. 2024-8922

[0005] However, the absorbent liquid described in Patent Document 1 has the problem of being highly volatile, causing the solvent to evaporate (solvent loss problem), and the absorbent liquid described in Patent Document 2 does not have sufficient hydrophobicity, so it absorbs a certain amount of moisture, and the energy consumed due to the latent heat of evaporation of water during acid gas recovery is large.

[0006] This invention was made to solve these problems and aims to provide an acidic gas absorbent liquid capable of sufficiently suppressing volatility and hygroscopicity, and a method for reducing acidic gases using the absorbent liquid.

[0007] This invention is based on the discovery that an acidic gas absorption solution containing an organic solvent having a predetermined LogS value and vapor pressure, and an amine compound, sufficiently suppresses volatility and hygroscopicity.

[0008] The present invention provides the following means: [1] An acidic gas absorbent that reversibly absorbs and desorbs carbon dioxide, comprising an organic solvent and an amine compound, wherein the organic solvent has a LogS value of 0 or less and a vapor pressure of 0.1 to 300.0 Pa at 25°C. [2] The acidic gas absorbent according to [1], wherein the organic solvent is at least one selected from the group consisting of alcohols, alkanes, and phenol derivatives. [3] The acidic gas absorbent according to [1] or [2], wherein the organic solvent is at least one selected from the group consisting of alcohols and alkanes. [4] The acidic gas absorbent according to [2] or [3], wherein the alcohol has 6 to 14 carbon atoms. [5] The SP value of the organic solvent is 15.0 to 22.0 (MPa). １／２ The acidic gas absorbent described in any of [1] to [4] above. [6] The SP value of the amine compound is 15.0 to 20.0 (MPa) １／２ The acidic gas absorbent according to any of [1] to [5] above. [7] The Hansen distance Ra between the organic solvent and the amine compound is 10.0 (MPa) １／２The following are the acidic gas absorbent liquids according to any one of [1] to [6] above: [8] The acidic gas absorbent liquid according to any one of [1] to [7] above, wherein the amine compound has a LogS value of 2.00 or less. [9] The acidic gas absorbent liquid according to any one of [1] to [8] above, wherein the amine compound is a linear or branched chain amine compound.

[10] The acidic gas absorbent liquid according to any one of [1] to [9] above, wherein the content of the organic solvent is 40 to 97% by mass relative to 100% by mass of the total content of the organic solvent and the amine compound.

[11] The acidic gas absorbent liquid according to any one of [1] to

[10] above, wherein the content of the amine compound is 3 to 60% by mass relative to 100% by mass of the total content of the organic solvent and the amine compound.

[12] An acidic gas reduction method comprising contacting the acidic gas absorbent liquid according to any one of [1] to

[11] above with a gas containing carbon dioxide to reduce the carbon dioxide in the gas.

[0009] The present invention provides an acidic gas absorbent liquid capable of sufficiently suppressing volatility and hygroscopicity, and a method for reducing acidic gases using the absorbent liquid.

[0010] The definitions and meanings of terms and notations used herein are given below. In this specification, preferred forms of embodiments are shown, but combinations of two or more individual preferred forms are also preferred forms. When there are several numerical ranges for matters indicated by numerical ranges, a preferred form can be obtained by selectively combining their lower and upper limits. For example, from a statement "preferably 10 to 90, more preferably 30 to 60", the "preferred lower limit (10)" and the "more preferred upper limit (60)" can be combined to become "10 to 60". Also, in numerical ranges described herein, the upper or lower limit of the numerical range may be replaced with the values ​​shown in the examples. Numerical ranges expressed using "~" mean that the numbers before and after "~" are the lower and upper limits. For organic solvents and amine compounds, known structural formulas are applied to the structural formulas of chemical substances, and in cases where the structural formula is not known, １ H-NMR and １３Identified by 13C-NMR analysis. If there are two or more organic solvents in the acidic gas absorption solution, the physical properties of each organic solvent (LogS value, vapor pressure at 25°C, solubility parameter HSP (dispersion term (δD1), polarity term (δP1), hydrogen bonding term (δH1)), SP value) are expressed as volume averages. If there are two or more amine compounds in the acidic gas absorption solution, the physical properties of each amine compound (LogS value, solubility parameter HSP (dispersion term (δD2), polarity term (δP2), hydrogen bonding term (δH2)), SP value) are expressed as volume averages.

[0011] [Acidic Gas Absorbent Solution] The acidic gas absorbent solution of the present invention is an acidic gas absorbent solution that reversibly absorbs and desorbs carbon dioxide, and contains an organic solvent and an amine compound. The organic solvent has a LogS value of 0 or less and a vapor pressure of 0.1 to 300.0 Pa at 25°C. The acidic gas absorbent solution may contain water or may not contain water, but it is preferable that it does not contain water.

[0012] The acidic gas is a gas containing carbon dioxide, and may also contain other acidic gases such as hydrogen sulfide or sulfur dioxide. The acidic gas absorbent liquid of this embodiment (hereinafter referred to as "this embodiment") can reversibly absorb and desorb carbon dioxide from acidic gases, and can be regenerated and reused. The following explanation will use the case where the acidic gas absorbed by the acidic gas absorbent liquid is carbon dioxide as an example.

[0013] The acidic gas absorbent of this embodiment contains an organic solvent having a predetermined LogS value and a predetermined vapor pressure, and an amine compound, and may further contain other components as needed. Furthermore, since the organic solvent used in combination with the amine compound has a predetermined vapor pressure, it is less volatile and has little impact on solvent loss.

[0014] (Organic Solvent) There is no particular limitation on the organic solvent as long as its LogS value is 0 or less and its vapor pressure at 25°C is 0.1 to 300.0 Pa. However, from the viewpoint of high hydrophobicity and low water absorption, it is preferably at least one selected from the group consisting of alcohols, alkanes, and phenol derivatives, and more preferably at least one selected from the group consisting of alcohols and alkanes. These may be used alone or in combination of two or more. As the alcohol, an alcohol having 6 to 14 carbon atoms is preferable from the viewpoints of compatibility with amine compounds and maintaining a liquid state at low temperatures. 2-Ethylhexanol, 1-nonanol, 2-octanol, 1-decanol, 1-undecanol, 1-dodecanol, and tridecan-1-ol are more preferable, and alcohols having 8 to 11 carbon atoms such as 2-ethylhexanol, 1-nonanol, 2-octanol, and 1-decanol are particularly preferable. As the alkane, alkanes such as decane, dodecane, hexadecane, heptadecane, octadecane, and nonadecane are preferable from the viewpoint of high hydrophobicity and low water absorption. There is no particular limitation on the phenol derivative, and examples thereof include 4-propylphenol.

[0015] <LogS Value of Organic Solvent> There is no particular limitation on the LogS value of the organic solvent as long as it is 0 or less. Preferably, it is -10.00 to 0.00, more preferably -7.00 to -1.00, and particularly preferably -7.00 to -1.50. When it is not less than the lower limit value of the above range, it has excellent compatibility with amine compounds, and when it is not more than the upper limit value of the above range, it has excellent low hygroscopicity. The LogS value of the organic solvent can be calculated by the method described in the examples.

[0016] <Vapor pressure of organic solvent at 25°C>The vapor pressure of the organic solvent at 25°C is not particularly limited as long as it is 0.1 to 300.0 Pa, preferably 0.1 to 100.0 Pa, more preferably 1.0 to 50.0 Pa, and particularly preferably 1.0 to 20.0 Pa. When it is not less than the lower limit value of the above range, the airflow in solvent volatilization accompanies the acidic gas and the recovery efficiency of the acidic gas is improved. When it is not more than the upper limit value of the above range, solvent volatilization is suppressed, and an increase in energy consumption due to the latent heat of vaporization accompanying solvent volatilization can be suppressed. The vapor pressure of the organic solvent at 25°C can be calculated by the method described in the examples.

[0017] <Solubility parameter (HSP) of organic solvent>The solubility parameter (HSP) of the organic solvent is the sum of three-dimensional vectors and is represented by solubility parameter HSP = dispersion term (δD1) + polar term (δP1) + hydrogen bond term (δH1). The dispersion term (δD1), polar term (δP1), and hydrogen bond term (δH1) can be calculated by the method described in the examples.

[0018] <SP value of organic solvent>The SP value of the organic solvent is not particularly limited, but preferably 15.0 to 22.0 (MPa) １／２ , more preferably 15.2 to 21.5 (MPa) １／２ , particularly preferably 15.4 to 21.0 (MPa) １／２ . When it is not less than the lower limit value of the above range, it is excellent in the absorbability of carbon dioxide into the acidic gas absorbent. When it is not more than the upper limit value of the above range, it is excellent in low hygroscopicity. The SP value of the organic solvent can be calculated by the following formula. SP value of organic solvent = { (δD1) ２ + (δP1) ２ + (δH1) ２} １／２

[0019] (Amine compound) The amine compound is preferably high in boiling point from the viewpoint that it is hardly volatilized even by heating for the desorption of carbon dioxide from the acidic gas absorbent and the influence on solvent loss is suppressed. The boiling point of the amine compound is not particularly limited, but preferably 130°C or higher, more preferably 140°C or higher, and still more preferably 150°C or higher.

[0020] <LogS Value of Amine Compounds> There are no particular restrictions on the LogS value of amine compounds, but it is preferably 2.00 or less, more preferably -3.00 to 1.80, and particularly preferably -2.00 to 1.60. If it is above the lower limit of the above range, it exhibits excellent absorption of carbon dioxide into the acidic gas absorbent, and if it is below the upper limit of the above range, it exhibits excellent low hygroscopicity. The LogS value of amine compounds can be calculated by the method described in the examples.

[0021] <Solubility Parameter (HSP) of Amine Compounds> The solubility parameter (HSP) of an amine compound is the sum of three-dimensional vectors, and is expressed as: Solubility parameter HSP = Dispersion term (δD2) + Polarity term (δP2) + Hydrogen bonding term (δH2). The dispersion term (δD2), polarity term (δP2), and hydrogen bonding term (δH2) can be calculated by the method described in the examples.

[0022] <SP value of amine compounds> There are no particular restrictions on the SP value of amine compounds, but it is preferably 15.0 to 20.0 (MPa). １／２ More preferably 16.0 to 19.7 (MPa) １／２ Particularly preferred is 17.0 to 19.4 (MPa) １／２ The SP value of an amine compound is calculated using the following formula: SP value of amine compound = {(δD2)} ２ + (δP2) ２ + (δH2) ２} １／２

[0023] <Specific Examples of Amine Compounds> Specific examples of amine compounds include diethylamine, N-ethylpropylamine, dipropylamine, diallylamine, diisopropylamine, di(2-methoxyethyl)amine, dibutylamine (also called "di-n-butylamine"), di-sec-butylamine, diamylamine, dihexylamine, (2-ethylhexyl)amine (2EHA), 3,3-iminobis(N,N-dimethylpropylamine), 3-(dibutylamino)propylamine (DBAPA), 2-(ethylamino)ethanol, 2-(propylamino)ethanol, isopropylaminoethanol, 2-(butylamino)ethanol, methylpropylaminoethanol, 4-(ethylamino)butanol, 4-(butylamino)butanol, benzylmethylamine (BMA), benzylethylamine, benzylpropylamine, benzylbutylamine, methylaniline, ethylaniline, propylaniline, and butylaniline. These may be used individually or in combination of two or more. Among these, (2-ethylhexyl)amine (2EHA), benzylmethylamine (BMA), dibutylamine (DBA), and 3-(dibutylamino)propylamine (DBAPA) are preferred, and (2-ethylhexyl)amine (2EHA) and dibutylamine (DBA) are more preferred. There are no particular restrictions on the amine compound, but linear or branched chain-like amine compounds are preferred from the viewpoint of having an excellent balance between the absorption and desorption of carbon dioxide into the acidic gas absorption solution and the solubility of the amine carbonate in the solvent. A chain-like amine compound means an amine compound that does not have a ring structure containing an amine.

[0024] <Hansen distance Ra between organic solvent and amine compound> There are no particular restrictions on the Hansen distance Ra between the organic solvent and the amine compound, but it is preferably 10.0 (MPa). １／２ More preferably, 8.5 (MPa) １／２ The following is particularly preferred: 7.0 (MPa) １／２ The following applies: The smaller the Hansen distance Ra between the organic solvent and the amine compound, the better the compatibility. A Hansen distance Ra of 10.0 (MPa) between the organic solvent and the amine compound indicates good compatibility. １／２Under the following conditions, the two substances have good compatibility, and a uniform absorbent solution can be easily obtained before and after carbon dioxide absorption. The Hansen distance Ra between the organic solvent and the amine compound can be calculated using the following formula: Hansen distance Ra = {4(δD1 - δD2)} ２ + (δP1 - δP2) ２ + (δH1 - δH2) ２} １／２

[0025] From the viewpoint of fully exhibiting carbon dioxide absorption capacity, the acidic gas absorbent preferably contains 40 to 97% by mass of organic solvent and 3 to 60% by mass of amine compound. There are no particular restrictions on the content of the organic solvent in the acidic gas absorbent, but it is preferably 40 to 97% by mass, more preferably 43 to 92% by mass, and most preferably 46 to 70% by mass. There are no particular restrictions on the content of the amine compound in the acidic gas absorbent, but it is preferably 3 to 60% by mass, more preferably 12 to 57% by mass, and most preferably 20 to 54% by mass. There are no particular restrictions on the total content of the organic solvent and amine compound in the acidic gas absorbent, but it is preferably 80% by mass or more, more preferably 90% by mass or more, most preferably 95% by mass or more, and may be 100% by mass. There are no particular restrictions on the content of the amine compound per 100 parts by mass of organic solvent in the acidic gas absorbent, but it is preferably 1 to 300 parts by mass, more preferably 2 to 250 parts by mass.

[0026] (Other components (additives)) The acidic gas absorbent may optionally contain other components (additives), such as antioxidants, corrosion inhibitors, viscosity modifiers, and surfactants, to the extent that they do not interfere with the effects of the present invention. There are no particular restrictions on the total content of other components (additives) in the acidic gas absorbent, but it is preferably 20% by mass or less, more preferably 10% by mass or less, particularly preferably 5% by mass or less, and may be 0% by mass. There are no particular restrictions on the water content in the acidic gas absorbent, but it is preferably 5% by mass or less, more preferably 3% by mass or less, particularly preferably 2% by mass or less, and may be 0% by mass.

[0027] The acidic gas absorbent of this embodiment can be prepared by mixing the above-mentioned organic solvent and amine compound. Alternatively, the above-mentioned additives and water may be added and mixed as needed.

[0028] The acidic gas absorbent of this embodiment is suitable for acidic gas recovery and separation processes, and is particularly suitable for carbon dioxide recovery and separation processes when the acidic gas is carbon dioxide. Examples of carbon dioxide recovery and separation processes include contacting a gas containing carbon dioxide with an acidic gas absorbent to selectively absorb and separate the carbon dioxide, releasing and recovering the carbon dioxide by heating or depressurizing the liquid that has absorbed the carbon dioxide, and recovering the liquid after the carbon dioxide has been released to regenerate it as an acidic gas absorbent.

[0029] There are no particular restrictions on the temperature of the absorbent liquid when absorbing carbon dioxide with the acidic gas absorbent liquid, but from the viewpoint of suppressing the load of gas cooling energy, it is preferably -10 to 60°C, more preferably 0 to 50°C. If it is above the lower limit of the above range, the load of gas cooling energy can be suppressed, and if it is below the upper limit of the above range, carbon dioxide can be absorbed sufficiently. There are no particular restrictions on the gas pressure when absorbing carbon dioxide with the acidic gas absorbent liquid, but if it is assumed to be about the same as the partial pressure of carbon dioxide in the atmosphere, from the viewpoint of making it easier to separate and recover carbon dioxide using the pressure difference from the atmosphere, it is preferably 20 to 100 Pa, more preferably 30 to 80 Pa, and particularly preferably 32 to 65 Pa. If it is assumed to be about the same as the partial pressure of carbon dioxide in combustion exhaust gas, from the viewpoint of making it easier to reduce the amount of water absorbed and to separate and recover carbon dioxide, it is preferably 0.5 to 100 kPa, more preferably 1 to 50 kPa, and particularly preferably 3 to 30 kPa.

[0030] There are no particular restrictions on the temperature of the absorbent liquid when releasing carbon dioxide from the acidic gas absorbent liquid, but it is preferably 50 to 120°C, more preferably 70 to 100°C, and most preferably 70 to 90°C. If the temperature is above the lower limit of the above range, carbon dioxide can be sufficiently desorbed from the acidic gas absorbent liquid, and if it is below the upper limit of the above range, deterioration of the acidic gas absorbent liquid can be suppressed. There are no particular restrictions on the gas pressure when releasing carbon dioxide from the acidic gas absorbent liquid, but from the viewpoint of facilitating the separation and recovery of carbon dioxide using the pressure difference from the atmosphere, it is preferably 0.5 to 20 Pa, more preferably 2 to 20 Pa, and most preferably 2.5 to 15 Pa.

[0031] The temperature difference between the absorption of carbon dioxide into the acidic gas absorbent and its release from the acidic gas absorbent is set by comparing and balancing the thermal energy required for carbon dioxide release with the amount recovered, preferably 80°C or less, more preferably 60°C or less. By combining this with processes such as hydrogen stripping or a heat pump, the temperature difference can be reduced, thereby lowering the required energy (see Japanese Patent Publication No. 6906766).

[0032] [Method for Reducing Acidic Gases] In the acidic gas reduction method of this embodiment, the amount of carbon dioxide in the gas is reduced by bringing the acidic gas absorbent liquid of this embodiment into contact with a gas containing carbon dioxide. The acidic gas absorbent liquid of this embodiment is effective not only when recovering carbon dioxide from a gas that does not contain water, but also when recovering carbon dioxide from a gas containing both carbon dioxide and water, as it can separate and remove water without heating and evaporation, thus further reducing the energy required to recover acidic gases from the gas.

[0033] Contact between the acidic gas absorbent and the gas can be achieved, for example, by adding the acidic gas absorbent to the gas, by continuously circulating the gas through a container filled with the acidic gas absorbent, or by filling a container filled with the acidic gas absorbent with the gas. To improve the contact efficiency between the acidic gas absorbent and the gas, methods such as providing a packing material in the container, spraying the acidic gas absorbent onto the gas, or bubbling the gas into the acidic gas absorbent can also be used.

[0034] The present invention will be described in detail below based on examples, but the present invention is not limited to the following examples, and various modifications are possible without departing from the spirit of the invention. Examples 1 to 10 and 17 to 21 are examples, and examples 11 to 16 are comparative examples.

[0035] [Preparation of Acid Gas Absorbent Solution] (Examples 1-21) As shown in Table 1, acid gas absorbent solutions were prepared by mixing various organic solvents and various amine compounds in predetermined mass ratios.

[0036] Table 1 shows (1-1) the name of the organic solvent, and (1-2) the solubility parameter (HSP) of the organic solvent (dispersion term (δD1), polarity term (δP1), hydrogen bonding term (δH1)) (unit: (MPa)). １／２ ), (1-3) SP value of organic solvents (unit: (MPa) １／２ (1-4) Vapor pressure of organic solvent (25°C) (Unit: Pa), (1-5) LogS value of organic solvent (Unit: none), (2-1) Name of amine compound, (2-2) Solubility parameter of amine compound (HSP) (Dispersion term (δD2), Polarity term (δP2), Hydrogen bonding term (δH2)) (Unit: (MPa) １／２ ), (2-3) SP value of amine compounds (unit: (MPa) １／２ (2-4) LogS value of the amine compound (unit: none), (3-1) Mass ratio of organic solvent to amine compound (organic solvent / amine compound), (3-2) Hansen distance Ra between organic solvent and amine compound (unit: (MPa) １／２ ), (4-1) Acid gas absorbent liquid (CO ２ Table 1 shows the water absorption rate (unit: mass%) before absorption, (4-2) the water absorption evaluation results of the acidic gas absorbent, and (4-3) the volatility evaluation results of the acidic gas absorbent. The abbreviations for the amine compounds in Table 1 are as follows: ・2EHA: (2-ethylhexyl)amine ・BMA: benzylmethylamine ・DBA: dibutylamine ・MEA: monoethanolamine

[0037] [(1-2) Solubility parameters (HSP) of organic solvents (dispersion term (δD1), polarity term (δP1), hydrogen bonding term (δH1)) (Unit: (MPa) １／２) ] Solubility parameters (HSP) of each organic solvent (dispersion term (δD1), polarity term (δP1), hydrogen bonding term (δH1)) (Unit: (MPa) １／２ The values ​​used were calculated by inputting the structural formula of each organic solvent into the software Hansen Solubility Parameters in Practice (HSPiP) ver. 5.2.02 as SMILES (Simplified Molecular Input Line Entry System). However, the solubility parameters (HSP) of the organic solvent (dispersion term (δD1), polarity term (δP1), hydrogen bonding term (δH1)) (unit: (MPa)) １／２ If the above software could not calculate the value, the value calculated using the method described in the paper "Hansen Solubility Parameters 50th anniversary conference, preprint PP.1-13, (2017), Hiroshi Yamamoto, Steven Abbott, Charles M. Hansen," published in Yamamoto's abstract Part 1 (https: / / pirika.com / HSP / HSP-J / HSP50 / Preprint-Part1%20Yamamoto.pdf) on the homepage "https: / / pirika.com / index-j.html," was used.

[0038] [(1-3) SP values ​​of organic solvents (unit: (MPa)) １／２ )] Solvent SP value (unit: (MPa) １／２ The SP value of the organic solvent was calculated using the following formula based on the solubility parameters (HSP) of the organic solvent calculated above (dispersion term (δD1), polarity term (δP1), hydrogen bonding term (δH1)). SP value of organic solvent = {(δD1) ２ + (δP1) ２ + (δH1) ２} １／２

[0039] [(1-4) Vapor pressure of organic solvents (25°C) (Unit: Pa)] The vapor pressure of organic solvents (25°C) (Unit: Pa) was calculated by inputting the SMILES value of the structural formula of each solvent into the software Hansen Solubility Parameters in Practice (HSPiP) ver. 5.2.02. However, if the vapor pressure of organic solvents (25°C) (Unit: Pa) could not be calculated by the software, the value calculated by the static method under the measurement conditions and apparatus described below was used. (1-4-1) Apparatus: Pressure gauge... MKS Balatron high-precision pressure gauge (sensor 690A13TRA) and MKS high-precision differential pressure gauge (sensor 616A12TRC), constant temperature bath... ESPEC Corporation constant temperature bath PH-101 (1-4-2) Thermometer: Platinum resistance thermometer (1-4-3) Stirrer: Thermo Electron GmbH magnetic stirrer (1-4-4) Measurement temperature: 25℃, 50℃, 80℃ (1-4-5) Measurement container: Stainless steel pressure vessel manufactured by Pressure Glass Industry Co., Ltd. (internal volume approximately 20 mL) (1-4-6) Sample volume: 2-ethylhexanol, 1-nonanol, 2-octanol, 1-decanol, 1-undecanol, decane, dodecane, 4-propylphenol, hexadecane, triethylene glycol, hexane, water, 1-butanol: approximately 3-5 mL, 2EHA, BMA, DBA, MEA: approximately 5-10 mL (1-4-7) Number of measurements n: 1

[0040] [(1-5) LogS Values ​​of Organic Solubility (Unit: None)] The LogS value of an organic solvent is a parameter that indicates the limit of the amount of organic solvent that can dissolve in water. For each organic solvent, the LogS value used was calculated by inputting the SMILES value of the structural formula of each organic solvent into the software Hansen Solubility Parameters in Practice (HSPiP) ver. 5.2.02.

[0041] [(2-2) Solubility parameters (HSP) of amine compounds (dispersion term (δD2), polarity term (δP2), hydrogen bonding term (δH2)) (Unit: (MPa) １／２ ) ] Solubility parameters (HSP) for each amine compound (dispersion term (δD2), polarity term (δP2), hydrogen bonding term (δH2)) (Unit: (MPa)１／２ The values ​​used were those calculated by inputting the SMILES value of the structural formula of each amine compound into the software Hansen Solubility Parameters in Practice (HSPiP) ver. 5.2.02. However, the solubility parameters (HSP) of the amine compounds (dispersion term (δD2), polarity term (δP2), hydrogen bonding term (δH2)) (unit: (MPa) １／２ If the above software could not calculate the value, the value calculated using the method described in the paper "Hansen Solubility Parameters 50th anniversary conference, preprint PP.1-13, (2017), Hiroshi Yamamoto, Steven Abbott, Charles M. Hansen," published in Yamamoto's abstract Part 1 (https: / / pirika.com / HSP / HSP-J / HSP50 / Preprint-Part1%20Yamamoto.pdf) on the homepage "https: / / pirika.com / index-j.html," was used.

[0042] [(2-3) SP values ​​of amine compounds (unit: (MPa) １／２ )] SP value of amine compounds (unit: (MPa) １／２ The SP value of the amine compound was calculated using the following formula based on the solubility parameter (HSP) of the amine compound calculated above (dispersion term (δD2), polarity term (δP2), hydrogen bonding term (δH2)). SP value of the amine compound = {(δD2) ２ + (δP2) ２ + (δH2) ２} １／２

[0043] [(2-4) LogS Values ​​of Amine Compounds (Unit: None)] The LogS value of an amine compound is a parameter that indicates the limit of the amount of amine compound that can dissolve in water. For each amine compound, the LogS values ​​used were calculated by inputting the SMILES value of the structural formula of each amine compound into the software Hansen Solubility Parameters in Practice (HSPiP) ver. 5.2.02.

[0044] [(3-2) Hansen distance Ra between organic solvent and amine compound (unit: (MPa) １／２ The Hansen distance Ra between the organic solvent and the amine compound was calculated using the following formula based on the solubility parameters (HSP) of the organic solvent (dispersion term (δD1), polarity term (δP1), hydrogen bonding term (δH1)) and the solubility parameters (HSP) of the amine compound (dispersion term (δD2), polarity term (δP2), hydrogen bonding term (δH2)): Ra = {4(δD1 - δD2) ２ + (δP1 - δP2) ２ + (δH1 - δH2) ２} （１／２） A smaller Ra value suggests higher compatibility between the organic solvent and the amine compound. Compared to the SP value, it is an index that takes the polarity of the substance into account and is considered to be more accurate.

[0045] [(4-1) Acid gas absorbent liquid (CO ２ [Water absorption rate (unit: mass%) before absorption] Acid gas absorbent (CO) for each example ２ (Before absorption) 1.5 g of the substance and 1.5 g of pure water were mixed in a 6 cc vial with a stirrer tip and stirred at 500 rpm for 360 minutes in a fume hood. Afterwards, the acidic gas absorbent (CO2) was used. ２ The sample (before absorption) was extracted using a syringe with a needle, and the water absorption rate (unit: mass%) contained in the acidic gas absorption solution for each example was calculated using a Karl Fischer (manufactured by Mitsubishi Chemical Analytec, trace moisture analyzer: model number CA-200). A case where the water absorption rate (unit: mass%) was less than 15.0 mass% was designated as "A", a case where it was 15.0 mass% or more but less than 25.0 mass% was designated as "B", and a case where it was 25.0 mass% or more was designated as "C".

[0046] [(4-2) Acid gas absorbent liquid (CO ２[Volatility before absorption (unit: mass%)] 3 g of the absorption solution for each example was filled into a 6 cc vial with a stirring bar, and the initial mass was measured using an electronic balance. Then, with the lid open, it was stirred at 500 rpm for 3 hours on a hot plate heated to 90°C, and the mass after volatilization was measured. The mass loss rate (mass%) calculated using the following formula was classified as "A" if it was less than 1.50 mass%, "B" if it was 1.50 mass% or more and less than 2.50 mass%, and "C" if it was 2.50 mass% or more. Mass loss rate (mass%) = (initial mass - mass after volatilization) / initial mass × 100

[0047] As can be seen from Table 1, the acidic gas absorption solutions of Examples 1-10 and 17-21, which contain an organic solvent with a LogS value of 0 or less and a vapor pressure of 0.1 to 300.0 Pa at 25°C, and an amine compound, can sufficiently suppress volatility and hygroscopicity.

Claims

1. An acidic gas absorbent that reversibly absorbs and desorbs carbon dioxide, comprising an organic solvent and an amine compound, wherein the organic solvent has a LogS value of 0 or less and a vapor pressure of 0.1 to 300.0 Pa at 25°C.

2. The acidic gas absorbent according to claim 1, wherein the organic solvent is at least one selected from the group consisting of alcohols, alkanes, and phenol derivatives.

3. The acidic gas absorbent according to claim 1, wherein the organic solvent is at least one selected from the group consisting of alcohols and alkanes.

4. The acidic gas absorbent according to claim 2, wherein the alcohol has 6 to 14 carbon atoms.

5. The SP value of the organic solvent is 15.0 to 22.0 (MPa). １／２ The acidic gas absorbent according to claim 1.

6. The SP value of the amine compound is 15.0 to 20.0 (MPa). １／２ The acidic gas absorbent according to claim 1.

7. The Hansen distance Ra between the organic solvent and the amine compound is 10.0 (MPa). １／２ The acidic gas absorbent according to claim 1, which is as follows:

8. The acidic gas absorbent according to claim 1, wherein the amine compound has a LogS value of 2.00 or less.

9. The acidic gas absorbent according to claim 1, wherein the amine compound is a linear or branched chain amine compound.

10. The acidic gas absorbent according to claim 1, wherein the content of the organic solvent is 40 to 97% by mass, relative to 100% by mass of the total content of the organic solvent and the amine compound.

11. The acidic gas absorbent according to claim 1, wherein the content of the amine compound is 3 to 60% by mass, relative to 100% by mass of the total content of the organic solvent and the amine compound.

12. A method for reducing acidic gases, comprising contacting an acidic gas absorbent liquid according to any one of claims 1 to 11 with a gas containing carbon dioxide to reduce the amount of carbon dioxide in the gas.

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