Carbon dioxide absorbent, carbon dioxide recovery method, and carbon dioxide separation and recovery device

Abstract

The present invention provides a carbon dioxide absorbent comprising a cyclic amine compound (A) and a porous material (B), wherein the aforementioned cyclic amine compound (A) has a primary amine group comprising 35 moles or more of all amine groups; and provides a method for recovering carbon dioxide using the carbon dioxide absorbent and a carbon dioxide separation and recovery apparatus.

Description

Technical Field

[0001] This invention relates to carbon dioxide absorbents, methods for recovering carbon dioxide, and carbon dioxide separation and recovery apparatus. Prior Technology

[0002] From the perspective of addressing global warming, it is necessary to reduce carbon dioxide emissions. One method for reducing carbon dioxide is the use of carbon dioxide absorbents to recover it. Commonly used absorbents are aqueous solutions of amine compounds such as monoethanolamine. Aqueous solutions of amine compounds have the following characteristics: they will not release absorbed carbon dioxide unless the temperature is above, for example, 120°C; and if the carbon dioxide release temperature is set above the boiling point of water, the high latent heat and specific heat of water necessitate a large amount of energy for carbon dioxide recovery. As mentioned above, one issue with conventional carbon dioxide absorbents is further energy conservation during the separation and recovery of carbon dioxide. Furthermore, conventional carbon dioxide absorbents have the following problem: during the carbon dioxide absorption process, a small amount of amine compounds evaporates and is lost upon contact with the gas; therefore, reducing the volatility of the amine compounds contained in the carbon dioxide absorbent is also an issue. Furthermore, in conventional chemical absorption methods, the carbon dioxide absorbent is regenerated by heating it to a temperature of approximately 110°C to 130°C with steam, causing it to boil. Therefore, this method requires a very large amount of thermal energy. In addition, the amine compounds contained in the carbon dioxide absorbent during this regeneration step may undergo thermal decomposition, thus the thermal stability of the carbon dioxide absorbent is also a concern.

[0003] In recent years, researchers have been studying carbon dioxide absorbents made by supporting amine compounds on porous materials. By supporting amine compounds on porous materials and solidifying them, carbon dioxide can be recovered with lower energy compared to aqueous solutions, which have high latent heat and specific heat issues. Regarding the technology of such solidified carbon dioxide absorbents, examples can be found in patent documents 1 to 3.

[0004] Patent document 1 describes a solid absorbent material for carbon dioxide separation and recovery containing a specific alkanolamine and the alkanolamine being supported on a support. Patent document 2 describes a carbon dioxide absorbent made by loading an amine compound onto porous particles obtained by combining hydrophilic fibers and porous powder with a hydrophilic binder. Patent document 3 describes a carbon dioxide absorption composition comprising polyethylene polyamine, phosphoric acid and / or phosphate, and silicon dioxide. [Previous Technical Documents] [Patent Literature]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2012-139622 [Patent Document 2] Japanese Patent Application Publication No. 2018-187574 [Patent Document 3] Japanese Patent Application Publication No. 2020-58966 Summary of the Invention

[0006] [The problem that the invention aims to solve]

[0007] According to the research of the inventors, the carbon dioxide absorbents containing amine compounds and porous materials as described in Patent Documents 1 to 3 have room for improvement in terms of reusability. The present invention is made in view of the above circumstances and provides: a carbon dioxide absorbent with improved reusability, a method for recovering carbon dioxide using the carbon dioxide absorbent, and a carbon dioxide separation and recovery apparatus. [Methods for solving problems]

[0008] The inventors conducted repeated and careful research to solve the aforementioned problems. As a result, they discovered that a carbon dioxide absorbent containing a specific cyclic amine compound (A) and a porous material can improve reusability, thus completing this invention.

[0009] That is, according to the present invention, the following carbon dioxide absorbent, carbon dioxide recovery method, and carbon dioxide separation and recovery apparatus can be provided.

[0010] [1] A carbon dioxide absorbent comprising a cyclic amine compound (A) and a porous material (B); The aforementioned cyclic amine compound (A) has a primary amine group that accounts for more than 35 mol% of all amine groups. [2] As described above [1], in the carbon dioxide absorbent, at least a portion of the aforementioned cyclic amine compound (A) is supported on the aforementioned porous material (B). [3] As described in [1] or [2] above, the aforementioned porous material (B) comprises at least one selected from the group consisting of silicon dioxide and alumina. [4] Carbon dioxide absorbents such as any of [1] to [3] above, wherein the aforementioned porous material (B) is in particle form. [5] As described above [4], the median particle size (D50) of the porous material (B) was determined by laser diffraction / scattering particle size distribution measurement to be above 1 μm and below 500 μm. [6] The carbon dioxide absorbents mentioned above [1] to [5] have a specific surface area of ​​more than 2 m² / g and less than 3000 m² / g as measured by the BET method. [7] The carbon dioxide absorbent of any of the above [1] to [6], wherein the pore volume of the aforementioned porous material (B) is 0.1 cm³ / g or more and 5.0 cm³ / g or less. [8] The carbon dioxide absorbent of any of [1] to [7] above, wherein the content of the aforementioned cyclic amine compound (A) is 0.1 parts by mass or more and 1000 parts by mass or less relative to 100 parts by mass of the aforementioned porous material (B). [9] The carbon dioxide absorbent of any of [1] to [8] above, wherein the aforementioned cyclic amine compound (A) comprises at least one of the group consisting of an amine compound (a1) represented by the following formula (1) and an amine compound (a2) having a heterocyclic structure selected from oxygen-containing heterocyclic structures and sulfur-containing heterocyclic structures; [Chemistry 1] In formula (1) above, R1 to R4 each independently represent a hydrogen atom, or may have a hydrocarbon group with 1 or more carbon atoms and less than 10 substituents selected from at least one of amino, cyano and phenyl; R5 to R10 each independently represent a hydrogen atom or a hydrocarbon group with 1 or more carbon atoms and less than 4 carbon atoms; x and y each independently represent an integer of 0 or more and less than 6; x+y is 1 or more and less than 6; p and q each independently represent an integer of 0 or more and less than 4; and at least one of p and q is 1 or more.

[10] The carbon dioxide absorbents mentioned in any of [1] to [9] above, wherein the maximum dissociation temperature of the carbon dioxide of the aforementioned cyclic amine compound (A) is determined to be below 140°C using the following method; method: The aforementioned cyclic amine compound (A) that has absorbed carbon dioxide was heated from 23°C to 250°C at a heating rate of 10°C / min. The temperature at which the heat of heat absorption accompanying the removal of the aforementioned carbon dioxide reached its maximum value was measured, and the aforementioned temperature was defined as the aforementioned maximum dissociation temperature of carbon dioxide.

[11] Carbon dioxide absorbents such as any of [1] to

[10] above, wherein the molecular weight of the aforementioned cyclic amine compound (A) is 90 or more and 1000 or less.

[12] The carbon dioxide absorbent of any of the above [1] to

[11] , wherein the amine value of the aforementioned cyclic amine compound (A) is above 400 mg KOH / g and below 1500 mg KOH / g.

[13] Carbon dioxide absorbents such as any of [1] to

[12] above, wherein the number of amine groups in the aforementioned cyclic amine compound (A) is 1 or more and 6 or less.

[14] Carbon dioxide absorbents such as any of [1] to

[13] above, wherein the cyclic structure of the aforementioned cyclic amine compound (A) comprises at least one selected from the group consisting of 5-membered rings and 6-membered rings.

[15] Carbon dioxide absorbents such as any of [1] to

[14] above, wherein the aforementioned cyclic amine compound (A) comprises at least one selected from the group consisting of bis(aminomethyl)cyclohexane and its derivatives, limonene diamine and its derivatives, isophorone diamine and its derivatives, 2,5-diaminomethylfuran and its derivatives, 2,5-bis(aminomethyl)tetrahydrofuran and its derivatives, furfural methylamine and its derivatives, tetrahydrofuran methylamine and its derivatives, 4-aminomethyltetrahydropiperanone and its derivatives, 4-(2-aminoethyl) α-line and its derivatives, and 2-thiophene methylamine and its derivatives.

[16] A method for recovering carbon dioxide uses a carbon dioxide absorbent as described in any of [1] to

[15] above.

[17] The carbon dioxide recovery method described above

[16] includes the following steps: an absorption step in which the carbon dioxide absorbent is brought into contact with a gas containing carbon dioxide, and the carbon dioxide absorbent absorbs the carbon dioxide; and a removal step in which the carbon dioxide is removed from the carbon dioxide absorbent that has absorbed carbon dioxide in the absorption step. The disengagement step includes at least one step selected from the group consisting of (I) to (III) below. (I) The step of placing the aforementioned carbon dioxide absorbent that has absorbed carbon dioxide under reduced pressure. (II) The step of contacting the aforementioned carbon dioxide absorbent, which has absorbed carbon dioxide, with an inert gas that does not contain carbon dioxide. (III) The step of heating the carbon dioxide absorbent that has absorbed carbon dioxide.

[18] As described in the carbon dioxide recovery method

[17] above, in the aforementioned absorption step, the temperature at which the aforementioned carbon dioxide absorbent comes into contact with the aforementioned carbon dioxide-containing gas is above 0°C and below 60°C.

[19] The carbon dioxide recovery method described in

[17] or

[18] above, wherein the heating temperature in step (III) above is 50°C and below 120°C.

[20] A carbon dioxide separation and recovery device, comprising: The absorption device includes a mechanism for contacting a carbon dioxide absorbent, such as any one of [1] to

[15] above, with a gas containing carbon dioxide, and for the carbon dioxide absorbent to absorb carbon dioxide; and The separation device is equipped with a mechanism for separating carbon dioxide from the aforementioned carbon dioxide absorbent that has absorbed carbon dioxide. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide: a carbon dioxide absorbent with improved reusability, a method for recovering carbon dioxide using the carbon dioxide absorbent, and a carbon dioxide separation and recovery apparatus. Simple Explanation of the Diagram

[0012] [Figure 1] shows a schematic diagram of one embodiment of the carbon dioxide separation and recovery device of the present invention. Implementation

[0013] The embodiments for implementing the present invention (hereinafter referred to as "the embodiments") will be described in detail below. The embodiments described below are illustrative of the present invention and do not limit the scope of the invention. The present invention can be appropriately modified within its scope. In the embodiments, any definition can be used that is preferred, and combinations of preferred elements are even better. In the embodiments, the phrase "XX~YY" means "XX or more and YY or less".

[0014] Carbon dioxide absorbent The carbon dioxide absorbent of the present invention comprises a cyclic amine compound (A) and a porous material (B), wherein the cyclic amine compound (A) has a primary amine group comprising more than 35 moles of all amine groups. The carbon dioxide absorbent of this invention comprises a cyclic amine compound (A) and a porous material (B), and its reusability has been improved. Furthermore, the carbon dioxide absorbent of this invention exhibits excellent performance in absorbing carbon dioxide from the air.

[0015] In this embodiment, "reusability" refers to the rate of maintenance of carbon dioxide absorption during cyclic tests of carbon dioxide absorption and removal. Furthermore, in this embodiment, "good absorption of carbon dioxide from the air" means a high absorption rate for low concentrations (approximately 0.04% by volume) of carbon dioxide in the air. "Primary amine group" refers to an amine group with two hydrogen atoms on a nitrogen atom, specifically the -NH₂ group.

[0016] The carbon dioxide absorbent of this invention comprises a cyclic amine compound (A) and a porous material (B). By containing the cyclic amine compound (A), reusability and the amount of carbon dioxide absorbed from the air can be improved. The reason for this is not yet clear, but it is believed to be as follows. Cyclic amine compound (A) has a cyclic structure that is not easily oxidized, so even when heated, it does not easily undergo oxidation or weight reduction when removing carbon dioxide. Furthermore, because cyclic amine compound (A) has a cyclic structure that does not easily absorb moisture, less energy is required to evaporate water when removing carbon dioxide, making it easier to remove. Considering these reasons, the carbon dioxide absorbent of the present invention is believed to improve reusability. Moreover, acyclic aliphatic amine compounds are considered to have poor reusability because they easily undergo cyclization, oxidation, and weight reduction upon heating. Furthermore, the cyclic amine compound (A) has a primary amine group comprising 35 mol% or more of the total amine groups. It is believed that such amine groups have low steric hindrance and readily absorb carbon dioxide. Therefore, it is believed that the carbon dioxide absorbent of the present invention can improve the absorption of carbon dioxide from the air.

[0017] In view of the view that carbon dioxide can be recovered with lower energy, it is preferable that at least a portion of the cyclic amine compound (A) is supported on the porous material (B) in the carbon dioxide absorbent of the present invention, and it is even more preferable that the cyclic amine compound (A) is supported on the porous material (B) and solidified.

[0018] The carbon dioxide absorbent of this invention has excellent performance in absorbing carbon dioxide from the air, and is therefore ideally suited for direct absorption of carbon dioxide from the air (DAC) technology. Furthermore, the carbon dioxide absorbent of the present invention is ideally suited for recovering low concentrations of carbon dioxide, such as 0.01% by volume or more and 1% by volume or less.

[0019] <Cyclic Amine Compound (A)> Cyclic amine compound (A) contains at least 35 mol% of primary amine groups relative to all amine groups. From the viewpoint of further improving reusability and carbon dioxide absorption from the air, it is preferable to have at least 40 mol% of primary amine groups, more preferably at least 45 mol%, more preferably at least 50 mol%, and preferably at least 100 mol%, more preferably at least 75 mol%, and even more preferably at least 70 mol%.

[0020] Cyclic amine compounds (A) are amine compounds with cyclic structures. Regarding the cyclic structure of the cyclic amine compound (A), for example, alicyclic hydrocarbon structures, aromatic hydrocarbon structures, and heterocyclic structures containing heteroatoms in the ring can be listed. Considering the viewpoint of improving reusability and the amount of carbon dioxide absorbed from the air, it is preferable to include at least one of the group consisting of alicyclic hydrocarbon structures and heterocyclic structures, it is even more preferable to include at least one of the group consisting of alicyclic hydrocarbon structures, oxygen-containing heterocyclic structures, and sulfur-containing heterocyclic structures, and it is even more preferable to include alicyclic hydrocarbon structures. In this embodiment, alicyclic hydrocarbon structure refers to a saturated or unsaturated ring structure composed of carbon and hydrogen that does not have aromaticity; heterocyclic structure refers to a heterocyclic structure containing heteroatoms in the ring; oxygen-containing heterocyclic structure or sulfur-containing heterocyclic structure refers to a heterocyclic structure in which oxygen atoms or sulfur atoms are heteroatoms in the ring structure.

[0021] Regarding the oxygen-containing heterocyclic structure of this embodiment, it is preferred to be a heterocyclic structure in which the ring structure contains both nitrogen and oxygen atoms as heteroatoms, or a heterocyclic structure in which the ring structure contains only oxygen atoms as heteroatoms; more preferably, a heterocyclic structure in which the ring structure contains only one oxygen atom as a heteroatom, or a heterocyclic structure in which the ring structure contains only one oxygen atom and one nitrogen atom as heteroatoms; and even more preferably, a heterocyclic structure in which the ring structure contains only one oxygen atom as a heteroatom. Furthermore, regarding the sulfur-containing heterocyclic structure of this embodiment, it is preferable to have a heterocyclic structure in which both nitrogen and sulfur atoms are heteroatoms, or a heterocyclic structure in which only sulfur atoms are heteroatoms; more preferably, a heterocyclic structure in which only one sulfur atom is a heteroatom, or a heterocyclic structure in which only one sulfur atom and one nitrogen atom are heteroatoms; and even more preferably, a heterocyclic structure in which only one sulfur atom is a heteroatom.

[0022] Furthermore, the cyclic amine compound (A) may take the structure of either the cis isomer or the trans isomer, or it may be any of the cis isomer, the trans isomer, or a mixture of the cis and trans isomers.

[0023] The cyclic structure of the cyclic amine compound (A) is preferably selected from at least one of the group consisting of 5-membered rings and 6-membered rings, with 6-membered rings being more preferred, considering the viewpoint of improving reusability and the amount of carbon dioxide absorbed from the air. Furthermore, considering the improved reusability and absorption of carbon dioxide from the air, cyclic amine compound (A) is preferably a single-ring structure. That is, cyclic amine compound (A) is preferably a monocyclic compound. Regarding the alicyclic hydrocarbon structure of the cyclic amine compound (A), examples include cyclopropane rings, cyclobutane rings, cyclopentane rings, cyclohexane rings, cycloheptane rings, and cyclooctane rings. Among the above ring structures, cyclopentane rings and cyclohexane rings are preferred, cyclohexane rings are even more preferred, and 1,3-substituted cyclohexane rings are even more preferred.

[0024] The number of amine groups in the cyclic amine compound (A) is preferably 1 or more, more preferably 2 or more, and preferably 6 or less, from the viewpoint of improving reusability and the amount of carbon dioxide absorbed from the air. Furthermore, regarding the amino group, from the perspective of further improving the absorption of carbon dioxide from the air, an amino group with a nitrogen-hydrogen bond is preferred, an amino group selected from at least one of the groups consisting of primary and secondary amino groups is preferred, and a primary amino group is even more preferred.

[0025] Cyclic amine compound (A), preferably selected from the group consisting of an amine compound (a1) represented by the following formula (1) and an amine compound (a2) having a heterocyclic structure selected from oxygen-containing heterocyclic structures and sulfur-containing heterocyclic structures, with regard to improving reusability and absorption of carbon dioxide from the air.

[0026] [Chemistry 2] In formula (1) above, R1 to R4 each independently represent a hydrogen atom, or may have a hydrocarbon group with 1 or more carbon atoms and less than 10 substituents selected from at least one of amino, cyano and phenyl; R5 to R10 each independently represent a hydrogen atom or a hydrocarbon group with 1 or more carbon atoms and less than 4 carbon atoms; x and y each independently represent an integer of 0 or more and less than 6; x+y is 1 or more and less than 6; p and q each independently represent an integer of 0 or more and less than 4; and at least one of p and q is 1 or more.

[0027] R1 to R4 are each independently a hydrogen atom, or may have a hydrocarbon group with 1 or more and 10 carbon atoms, selected from at least one of amino, cyano, and phenyl, preferably a hydrogen atom, or may have an alkyl group with 1 or more and 4 carbon atoms, selected from at least one of amino, cyano, and phenyl, more preferably a hydrogen atom, or may have an alkyl group with 1 or more and 4 carbon atoms, selected from at least one of amino and cyano, even more preferably a hydrogen atom, or may have an alkyl group with 2 or more and 4 carbon atoms, selected from at least one of amino and cyano. The number of carbon atoms in each of the hydrocarbon groups R1 to R4 is independently 1 or more, preferably 2 or more, and 10 or less, preferably 5 or less, more preferably 4 or less, and even more preferably 3 or less.

[0028] R5 to R10 are each independently a hydrogen atom or a hydrocarbon group having 1 or more but 4 or fewer carbon atoms, preferably a hydrogen atom or an alkyl group having 1 or more but 4 or fewer carbon atoms, more preferably a hydrogen atom or an alkyl group having 1 or more but 3 or fewer carbon atoms, even more preferably a hydrogen atom or a methyl group, and even more preferably a hydrogen atom. The number of carbon atoms in each of the hydrocarbon groups R5 to R10 is independently 1 or more and 4 or less, preferably 1 or 2, and more preferably 1.

[0029] p and q are each independently greater than or equal to 0, preferably greater than or equal to 1, and less than or equal to 4, preferably less than or equal to 2, and even more preferably 1. However, at least one of p and q is greater than or equal to 1.

[0030] x and y each independently represent an integer greater than 0 and less than 6, and x+y is greater than 1 and less than 6. Considering the need for greater steric hindrance to the molecule as a whole, improved reusability, and increased absorption of carbon dioxide from the air, x+y is preferably 2 or more, more preferably 3 or more, and even more preferably 4 or more. Considering the need for improved carbon dioxide absorption, it is preferably less than 5, and even more preferably 4. That is, alicyclic hydrocarbon structures with 5-membered or 6-membered rings are preferred, with 6-membered rings being more preferred. When x+y is 4, the preferred system is x = 1 and y = 3.

[0031] Regarding cyclic amine compound (A), considering the viewpoint of further improving reusability and the amount of carbon dioxide absorbed from the air, it is preferably selected from at least one of the group consisting of o-phenylenediamine and its derivatives, m-phenylenediamine and its derivatives, p-phenylenediamine and its derivatives, bis(aminomethyl)cyclohexane and its derivatives, limonenediamine and its derivatives, isophoronediamine and its derivatives, 2,5-diaminomethylfuran and its derivatives, 2,5-bis(aminomethyl)tetrahydrofuran and its derivatives, furfural methylamine and its derivatives, tetrahydrofuran methylamine and its derivatives, 4-aminomethyltetrahydropiperanan and its derivatives, 4-(2-aminoethyl)phospholine and its derivatives, and 2-thiophene methylamine and its derivatives; more preferably selected from bis(aminomethyl)cyclohexane and its derivatives, limonenediamine and its derivatives, isophoronediamine and its derivatives, 2,5-bis(aminomethyl)tetrahydrofuran and its derivatives. At least one of the group consisting of furfural methylamine and its derivatives, tetrahydrofuran methylamine and its derivatives, 4-aminomethyltetrahydropiperanol and its derivatives, 4-(2-aminoethyl)phospholine and its derivatives, and 2-thiophene methylamine and its derivatives; more preferably at least one selected from bis(aminomethyl)cyclohexane and its derivatives, limonene diamine and its derivatives, and isophorone diamine and its derivatives; more preferably bis(aminomethyl)cyclohexane and its derivatives, and even more preferably 1 ,3-bis(aminomethyl)cyclohexane and its derivatives, more preferably derivatives of 1,3-bis(aminomethyl)cyclohexane; more ideally derivatives of 1,3-bis(aminomethyl)cyclohexane represented by formula (2), formula (3), formula (4) or formula (5), more ideally derivatives of 1,3-bis(aminomethyl)cyclohexane represented by formula (3) or formula (5), and even more ideally derivatives of 1,3-bis(aminomethyl)cyclohexane represented by formula (5). Here, with regard to the various amine derivatives mentioned above, for example, compounds in which at least one of the hydrogen atoms of the amino group is substituted with the following groups: a hydrocarbon group having 1 or more and 10 or less carbon atoms of a substituent selected from at least one of the groups consisting of amino, cyano, and phenyl; preferably an alkyl group having 1 or more and 4 or less carbon atoms of a substituent selected from at least one of the groups consisting of amino, cyano, and phenyl; more preferably an alkyl group having 1 or more and 4 or less carbon atoms of a substituent selected from at least one of the groups consisting of amino and cyano; and even more preferably an alkyl group having 2 or more and 4 or less carbon atoms of a substituent selected from at least one of the groups consisting of amino and cyano. Furthermore, regarding the derivatives of the various amines mentioned above, for example, compounds in which at least some of the hydrogen atoms in the cyclic structure are replaced by the following groups: hydrocarbon groups having 1 or more and 4 or fewer carbon atoms, preferably alkyl groups having 1 or more and 3 or fewer carbon atoms, more preferably methyl or ethyl, and even more preferably methyl.

[0032] [Chemistry 3]

[0033] These cyclic amine compounds (A) can be used alone or in combination of two or more.

[0034] The content of the cyclic amine compound (A) in the carbon dioxide absorbent of the present invention, considering the viewpoint of improving reusability and the amount of carbon dioxide absorbed from the air, is preferably 0.1 parts by mass or more, more preferably 1 part by mass or more, even more preferably 10 parts by mass or more, even more preferably 25 parts by mass or more, even more preferably 50 parts by mass or more, and preferably less than 1000 parts by mass, even more preferably less than 500 parts by mass, even more preferably less than 250 parts by mass, even more preferably less than 200 parts by mass, and even more preferably less than 150 parts by mass. Furthermore, considering the viewpoint of improving reusability and the amount of carbon dioxide absorbed from the air, the content of cyclic amine compound (A) in the carbon dioxide absorbent of the present invention is preferably 50 parts by mass or more, more preferably 60 parts by mass or more, even more preferably 70 parts by mass or more, even more preferably 80 parts by mass or more, even more preferably 90 parts by mass or more, even more preferably 95 parts by mass or more, and preferably less than 100 parts by mass.

[0035] The maximum carbon dioxide dissociation temperature of the cyclic amine compound (A), determined using the following method, is preferably below 140°C, more preferably below 130°C, even more preferably below 120°C, and still more preferably below 110°C, and even more preferably below 105°C, considering the improvement of carbon dioxide dissociation and reusability. There are no particular limitations on the lower limit of the above-mentioned maximum carbon dioxide dissociation temperature, but it may be, for example, above 40°C. method: A cyclic amine compound (A) that has absorbed carbon dioxide is heated from 23°C to 250°C at a heating rate of 10°C / min. The temperature at which the endothermic heat accompanying the release of carbon dioxide reaches its maximum is measured and defined as the maximum dissociation temperature of carbon dioxide. Here, the cyclic amine compound (A) that has absorbed carbon dioxide can be prepared, for example, by placing 5 mmol of the cyclic amine compound (A) in air at 23°C and 50% RH for 24 hours.

[0036] The acid dissociation constant (pKa) of the cyclic amine compound (A) is preferably 8.0 or higher, more preferably 9.0 or higher, and even more preferably 9.3 or higher, considering the viewpoint of improving the absorption of carbon dioxide from the air. Furthermore, considering the viewpoint of improving the removal of carbon dioxide and improving reusability, it is preferably 12.0 or lower, and even more preferably 11.0 or lower. In this embodiment, the acid dissociation constant of the cyclic amine compound (A) is obtained by means of the following determination method based on acid-base titration. (1) Dissolve 0.2g of cyclic amine compound (A) in 30mL of purified water. (2) The acid dissociation constant (pKa) is calculated by titrating the solution obtained from (1) above with a 0.1 N perchloric acid-acetic acid solution using an automatic potentiometric titration device (e.g., Kyoto Electronics Co., Ltd., AT-610). Furthermore, the temperature during the measurement was set to 25±2℃.

[0037] The molecular weight of the cyclic amine compound (A) is preferably 90 or higher, more preferably 120 or higher, even more preferably 140 or higher, even more preferably 160 or higher, even more preferably 180 or higher, even more preferably 200 or higher, even more ideally 220 or higher, and even more suitable 240 or higher, considering the viewpoint of further improving the absorption of carbon dioxide from the air. It is preferably 1000 or lower, more preferably 800 or lower, even more preferably 600 or lower, even more preferably 500 or lower, and even more preferably 400 or lower.

[0038] The maximum endothermic temperature of the cyclic amine compound (A), determined by the following method, is preferably 120°C or higher, more preferably 130°C or higher, even more preferably 150°C or higher, even more preferably 160°C or higher, even more preferably 180°C or higher, even more preferably 200°C or higher, and even more ideally 220°C or higher, considering the viewpoint of further improving the absorption of carbon dioxide from the air, preferably 350°C or lower. method: Cyclic amine compound (A) was heated from 23°C to 350°C at a heating rate of 10°C / min. The temperature at which the heat endothermic with the volatilization of cyclic amine compound (A) reached its maximum value was measured and defined as the maximum endothermic temperature of cyclic amine compound (A).

[0039] The amine value of the cyclic amine compound (A), considering improvements in reusability and absorption of carbon dioxide from the air, is preferably 400 mg KOH / g or higher, more preferably 500 mg KOH / g or higher, even more preferably 550 mg KOH / g or higher, and preferably below 1500 mg KOH / g, even more preferably below 1200 mg KOH / g, even more preferably below 1000 mg KOH / g, and even more preferably below 900 mg KOH / g. The amine value indicates the amount of amine in the compound and refers to the number of mg of potassium hydroxide (KOH) equivalent to the amount of acid required to neutralize 1 g of the compound. The amine value can be determined according to JIS K7237-1995 using the following method. (1) Dissolve 0.1 g of cyclic amine compound (A) in 20 mL of acetic acid. (2) The amine value is calculated by titrating the solution obtained from (1) above with a 0.1 N perchloric acid-acetic acid solution using an automatic potentiometric titration device (e.g., Kyoto Electronics Co., Ltd., AT-610).

[0040] <Porous Materials (B)> Regarding the porous material (B), it is preferable to be capable of supporting cyclic amine compounds (A) and tolerating carbon dioxide recovery conditions. Examples include at least one selected from the group consisting of silicon dioxide, alumina, silica-alumina, magnesium oxide, zirconium oxide, zeolite, zeolite-like compounds, clay minerals, natural minerals, activated carbon, carbon molecular sieves (porous carbon), porous resins (synthetic adsorbents), metal-organic structures, and solid waste. Among these, regarding the porous material (B), it is preferable to be at least one selected from the group consisting of silicon dioxide and alumina, with silicon dioxide being more preferred, and mesoporous silicon dioxide being even more preferred.

[0041] The porous material (B) is preferably in particle form. This increases the specific surface area of ​​the porous material (B), which improves the loading of the cyclic amine compound (A), thereby further improving the carbon dioxide absorption capacity of the carbon dioxide absorbent of the present invention.

[0042] The volume median particle size (D50) of the porous material (B) measured by laser diffraction / scattering particle size distribution measurement is preferably 1 μm or more, more preferably 5 μm or more, and even more preferably 10 μm or more, considering the viewpoint of improving operability. Considering the viewpoint of further improving the loading of cyclic amine compound (A), it is preferably 500 μm or less, more preferably 300 μm or less, even more preferably 200 μm or less, even more preferably 180 μm or less, and even more preferably 160 μm or less.

[0043] Based on the specific surface area of ​​the porous material (B) measured by the BET method, and considering the viewpoint of further improving the loading of cyclic amine compound (A), it is preferably 2 m² / g or more, more preferably 10 m² / g or more, even more preferably 100 m² / g or more, even more preferably 200 m² / g or more, even more preferably 400 m² / g or more, and even more preferably 600 m² / g or more. Considering the viewpoint of improving operability, it is preferably 3000 m² / g or less, more preferably 1500 m² / g or less, even more preferably 1200 m² / g or less, and even more preferably 1000 m² / g or less. The pore volume of the porous material (B), considering the viewpoint of further improving the loading of cyclic amine compound (A), is preferably 0.1 cm³ / g or more, more preferably 0.3 cm³ / g or more, and even more preferably 0.5 cm³ / g or more. Considering the viewpoint of improving reusability, it is preferably 5.0 cm³ / g or less, more preferably 3.0 cm³ / g or less, even more preferably 2.5 cm³ / g or less, even more preferably 2.0 cm³ / g or less, even more preferably 1.5 cm³ / g or less, and even more preferably 1.0 cm³ / g or less. Specific surface area and pore volume can be measured, for example, using a constant volume method and a specific surface area and pore size distribution measuring device (e.g., product name: ASAP2020, manufactured by Shimadzu Corporation). More specifically, regarding the gas adsorption measurement method using a specific surface area and pore size distribution measuring device, for example, sample pretreatment is performed by heating and vacuum degassing, and 0.1 g of the sample is placed in a sample tube. Afterwards, the sample is heated to 40°C and vacuum degassed for 6 hours, then cooled to room temperature, and the sample mass is measured. During measurement, the liquid nitrogen temperature is set and a specified pressure range is defined. The specific surface area, pore volume, and pore size can be analyzed and calculated from the obtained nitrogen adsorption isotherm.

[0044] Porous materials (B) can also be granulated from the aforementioned particulate porous materials using known methods to produce pellets, flakes, or other granules. Examples of granulation methods include dry granulation using a compression molding machine and wet granulation using a binder. By granulating and using particulate porous materials, vibration resistance, wear resistance, and physical stability can be improved.

[0045] The total content of the cyclic amine compound (A) and porous material (B) in the carbon dioxide absorbent of the present invention is, in view of improving reusability and the amount of carbon dioxide absorbed from the air, preferably 60% by mass or more, more preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, even more preferably 95% by mass or more, even more preferably 98% by mass or more, and preferably less than 100% by mass.

[0046] <Other Ingredients> The carbon dioxide absorbent of the present invention may contain, to a degree that does not impair the effectiveness of the invention, components other than cyclic amine compounds (A) and porous materials (B). Examples of components other than cyclic amine compounds (A) and porous materials (B) include degradation inhibitors, defoamers, antioxidants, and desiccants for removing moisture (such as magnesium sulfate and molecular sieves).

[0047] The water content in the carbon dioxide absorbent of this invention, considering the viewpoint of improving reusability and the amount of carbon dioxide absorbed from the air, is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 1% by mass or less, even more preferably 0.5% by mass or less, even more preferably 0.1% by mass or less, and even more preferably 0.01% by mass or less. Ideally, the carbon dioxide absorbent of this invention is substantially water-free. Here, "substantially water-free" means intentionally not adding water, but does not exclude the possibility of a small amount of water as an impurity.

[0048] <Preparation Method of Carbon Dioxide Absorbent> There are no particular restrictions on the preparation method of carbon dioxide absorbent, and known methods can be used. For example, it can be prepared by blending a cyclic amine compound (A) with a porous material (B) and mixing them using a known apparatus. When at least a portion of a cyclic amine compound (A) is supported on a porous material (B) as a carbon dioxide absorbent, the carbon dioxide absorbent is preferably prepared by the following method. First, a mixture is prepared by blending a cyclic amine compound (A), a porous material (B), and an organic solvent, and preferably by stirring at a temperature of 5–60°C for 1–24 hours. Next, the organic solvent is removed from the obtained mixture by distillation or the like, and the remaining solid components are dried under reduced pressure to obtain a carbon dioxide absorbent. Regarding the aforementioned organic solvents, considering the dispersibility of cyclic amine compounds (A) and porous materials (B), and the ease of removal from carbon dioxide absorbents, a monohydric alcohol with four or fewer carbon atoms is preferred, and at least one selected from methanol, ethanol, and isopropanol is even more preferred.

[0049] Methods for recovering carbon dioxide The carbon dioxide recovery method of the present invention (hereinafter also referred to as "the method of the present invention") is characterized by the use of the aforementioned carbon dioxide absorbent, and according to the method of the present invention, the amount of carbon dioxide absorbed from a carbon dioxide-containing gas can be improved. Furthermore, carbon dioxide can be recovered with lower energy, and the reusability of the carbon dioxide absorbent is also good.

[0050] The carbon dioxide recovery method of the present invention preferably includes the step of contacting the aforementioned carbon dioxide absorbent with a gas containing carbon dioxide and allowing the carbon dioxide absorbent to absorb the carbon dioxide (absorption step).

[0051] <Absorption Steps> The absorption step involves contacting the aforementioned carbon dioxide absorbent with a carbon dioxide-containing gas, allowing the absorbent to absorb the carbon dioxide. The method of contacting the carbon dioxide absorbent with the gas can be chosen appropriately depending on the type of carbon dioxide absorbent and is not particularly limited. For example, the carbon dioxide absorbent and the carbon dioxide-containing gas can be contacted by passing the carbon dioxide-containing gas through the carbon dioxide absorbent, dispersing the carbon dioxide absorbent in the carbon dioxide-containing gas, or placing the carbon dioxide absorbent in the carbon dioxide-containing gas.

[0052] There are no particular limitations on the gases containing carbon dioxide, such as air, exhaust from thermal power plants, exhaust from steel mills, exhaust from cement plants, exhaust from chemical plants, biogas fermentation gases, and natural gas. This invention is particularly effective in recovering carbon dioxide from these gases in an energy-saving manner. Furthermore, there are no particular limitations on the concentration of carbon dioxide in the gas, the gas pressure, and the gas temperature, allowing the method of this invention to be applied to a wide range of gases under various conditions. Furthermore, gases containing carbon dioxide may also contain acidic gases other than carbon dioxide. Examples of such acidic gases include CO, NOx, SOx in exhaust gas, formaldehyde produced during methanol fuel power generation, hydrogen chloride, and hydrogen sulfide. When the aforementioned gases containing carbon dioxide contain acidic gases other than carbon dioxide, it is ideal to combine known steps for removing these other acidic gases. Specifically, examples include: applying the carbon dioxide recovery method of this invention to gases containing acidic gases other than carbon dioxide, or applying the carbon dioxide recovery method of this invention after removing other acidic gases from gases containing acidic gases other than carbon dioxide using known methods.

[0053] In the absorption step, the temperature at which the carbon dioxide absorbent comes into contact with the carbon dioxide-containing gas is preferably above 0°C and below 60°C, more preferably above 20°C and below 60°C, and even more preferably above 30°C and below 60°C, in view of improving the amount of carbon dioxide absorbed.

[0054] The method of the present invention preferably includes the following steps: an absorption step, in which the aforementioned carbon dioxide absorbent is brought into contact with a carbon dioxide-containing gas, and the carbon dioxide absorbent absorbs the carbon dioxide; and a separation step, in which the carbon dioxide is separated from the carbon dioxide absorbent that has absorbed carbon dioxide in the absorption step; the separation step includes at least one step selected from the group consisting of (I) to (III) below. By this method, carbon dioxide can be separated and recovered from a carbon dioxide-containing gas. (I) The step of placing the aforementioned carbon dioxide absorbent, which has absorbed carbon dioxide, under reduced pressure; (II) The step of contacting the aforementioned carbon dioxide absorbent, which has absorbed carbon dioxide, with an inert gas that does not contain carbon dioxide; (III) The step of heating the carbon dioxide absorbent that has absorbed carbon dioxide.

[0055] <Disengagement Steps> The removal step is the step of removing carbon dioxide from the carbon dioxide absorbent that has absorbed carbon dioxide in the absorption step. A preferred method for removing carbon dioxide from the carbon dioxide absorbent that has absorbed carbon dioxide is a method comprising at least one step selected from the group consisting of (I) to (III) described above. Two or more steps from (I) to (III) may also be combined.

[0056] In step (I), which involves placing the carbon dioxide absorbent under reduced pressure (hereinafter also referred to as "step (I)"), the reduced pressure is preferably 10 kPa or less, more preferably 5 kPa or less, and even more preferably 1 kPa or less, from the viewpoint of improving the separation and recovery efficiency of carbon dioxide. Furthermore, from the viewpoint of suppressing the volatilization of cyclic amine compounds (A) in the carbon dioxide absorbent, it is preferably 0.1 kPa or more. In step (I), there is no particular limitation on the temperature at which the carbon dioxide absorbent is placed under reduced pressure. However, considering the need to suppress the volatilization of cyclic amine compounds (A) in the carbon dioxide absorbent, it is preferable to keep the temperature below 50°C, and more preferably below 45°C. Furthermore, considering the need to improve the separation and recovery efficiency of carbon dioxide, it is preferable to keep the temperature above 0°C, and more preferably above 10°C.

[0057] In step (II), where the carbon dioxide absorbent that has absorbed carbon dioxide is contacted with an inert gas that does not contain carbon dioxide (hereinafter also referred to as "step (II)"), the removal of carbon dioxide can be promoted by reducing the partial pressure of carbon dioxide. Examples of inert gases that do not contain carbon dioxide include nitrogen, helium, and argon, and one or more of these can be used. From the viewpoint of improving the separation and recovery efficiency of carbon dioxide, the inert gas that does not contain carbon dioxide is preferably selected from at least one of nitrogen and argon. In step (II), the method of contacting the carbon dioxide absorbent with an inert gas that does not contain carbon dioxide can be the same as the contact method described in the aforementioned absorption step. In step (II), there is no particular limitation on the temperature at which the carbon dioxide absorbent comes into contact with an inert gas free of carbon dioxide. The heating defined in step (III) can be performed simultaneously in step (II), or the temperature can be below room temperature. From the viewpoint of suppressing the volatilization of cyclic amine compounds (A) in the carbon dioxide absorbent, this temperature is preferably below 50°C, and more preferably below 45°C. Furthermore, from the viewpoint of improving the separation and recovery efficiency of carbon dioxide, it is preferably above 0°C, and more preferably above 10°C.

[0058] (III) The heating temperature in the step of heating the carbon dioxide absorbent that has absorbed carbon dioxide (hereinafter also referred to as "step (III)") is preferably above 50°C and below 120°C, more preferably above 55°C and below 110°C, and even more preferably above 60°C and below 100°C, in view of improving the separation and recovery efficiency of carbon dioxide. The heating in step (III) can be performed using a device equipped with a heating element and by a known method. Examples of heating methods include heating using steam or a heat medium, hot air heating, electromagnetic wave heating, ultrasonic heating, and induction heating.

[0059] The carbon dioxide absorbent and carbon dioxide obtained in the separation step can be individually recovered and reused.

[0060] Carbon dioxide separation and recovery unit The carbon dioxide separation and recovery apparatus of the present invention (hereinafter also referred to as "the apparatus of the present invention") comprises: an absorption device having a mechanism for contacting the aforementioned carbon dioxide absorbent with a gas containing carbon dioxide and for the carbon dioxide absorbent to absorb carbon dioxide; and a separation device having a mechanism for separating carbon dioxide from the carbon dioxide absorbent that has absorbed carbon dioxide.

[0061] The apparatus of the present invention will be described with reference to FIG1. ​​FIG1 is a schematic diagram showing one embodiment of the carbon dioxide separation and recovery apparatus 100 of the present invention. In FIG1, 1 is the absorption device and 2 is the separation device.

[0062] <Absorption device> The absorption device 1 in the carbon dioxide separation and recovery device 100 is a mechanism that includes the aforementioned carbon dioxide absorbent, brings the carbon dioxide absorbent into contact with a gas containing carbon dioxide, and allows the carbon dioxide absorbent to absorb carbon dioxide.

[0063] There are no particular limitations on the absorber 1 if it is configured to contact the carbon dioxide absorbent with the carbon dioxide-containing gas, depending on the type of carbon dioxide absorbent. For example, as shown in FIG1, the absorber 1 can have an absorbent holding section 12 for holding the carbon dioxide absorbent 12a inside the reaction tower 11, and further have a gas supply section 13 for supplying the absorbent holding section 12 with the carbon dioxide-containing gas. Furthermore, considering the viewpoint of discharging the carbon dioxide absorbent that has absorbed carbon dioxide from the absorbent holding section 12 and supplying new carbon dioxide absorbent, the absorber 1 can also have an absorbent discharge section (not shown) for discharging the carbon dioxide absorbent 12a held in the absorbent holding section 12, and an absorbent supply section (not shown) for supplying new carbon dioxide absorbent to the absorbent holding section 12.

[0064] The absorption device 1 may also be equipped with a heating and cooling mechanism to adjust the temperature at which the carbon dioxide absorbent comes into contact with the carbon dioxide-containing gas. Furthermore, a carbon dioxide concentration measuring mechanism may be provided to measure the concentration of carbon dioxide in the gas. In addition, the absorption device 1 may also be equipped with a pressure-regulating mechanism to adjust the pressure at which the carbon dioxide absorbent comes into contact with the carbon dioxide-containing gas.

[0065] The carbon dioxide separation and recovery device 100 may also have a connection part 3 for supplying the carbon dioxide absorbent that has absorbed carbon dioxide in the absorption device 1 to the separation device 2. There are no particular restrictions on the method of supplying carbon dioxide absorbent that has absorbed carbon dioxide from absorption device 1 to desorption device 2. Alternatively, absorption device 1, which has been operating for a certain period of time, can be temporarily stopped, and carbon dioxide absorbent in the reaction tower 11 of absorption device 1 can be supplied to desorption device 2 in a concentrated manner. Or, carbon dioxide absorbent can be supplied to desorption device 2 continuously or intermittently from absorbent holding part 12 of absorption device 1 via connecting part 3.

[0066] <Disengagement Device> The separation device 2 in the carbon dioxide separation and recovery device 100 is a mechanism that removes carbon dioxide from the carbon dioxide absorbent by heating the carbon dioxide absorbent that has absorbed carbon dioxide in the absorption device 1. There are no particular limitations on whether the separation device 2 has a mechanism for removing carbon dioxide from the carbon dioxide absorbent that has absorbed carbon dioxide in the absorption device 1, but it is preferable that it has a mechanism for performing at least one of the aforementioned steps (I) to (III). Examples of such mechanisms include a pressure reduction mechanism, an inert gas supply mechanism, and a heating mechanism.

[0067] For example, the separation device 2, as shown in FIG1, can have an absorbent holding section 22 inside the reaction tower 21 to hold the carbon dioxide absorbent 22a that has absorbed carbon dioxide, and further has a gas discharge section 23 to discharge the carbon dioxide that has been separated from the carbon dioxide absorbent. In addition, the separation device 2 has at least one mechanism (not shown) selected from the following: a pressure reducing mechanism for making the reaction tower 21 a pressure reducing condition, an inert gas supply mechanism for supplying inert gas to the absorbent holding section 22, and a heating mechanism for heating the absorbent holding section 22. In addition to the aforementioned pressure reduction mechanism, inert gas supply mechanism, and heating mechanism, the separation device 2 may also have a carbon dioxide concentration measuring mechanism, just like the absorption device 1.

[0068] The carbon dioxide absorbent after carbon dioxide is removed in the separation device 2 can also be supplied to the absorption device 1 again from the absorbent discharge section 24, which is used to supply the carbon dioxide absorbent after carbon dioxide removal to the absorption device 1, and reused.

[0069] The carbon dioxide separation and recovery unit 100 can also be further used as a recovery unit to recover the carbon dioxide obtained after separation. Furthermore, the recovered carbon dioxide can be used for agricultural applications such as enhanced oil recovery or plant factories; industrial gas applications such as beverages and welding; chemical synthesis applications; and carbon dioxide capture and storage (CCS) applications. Additionally, the recovered carbon dioxide can be concentrated before use in these applications. [Example]

[0070] The present invention will now be described by way of examples, but the present invention is not limited to the scope of the examples. Furthermore, in this embodiment, various measurements and evaluations are performed using the following methods.

[0071] (Acid dissociation constant (pKa) of amine compounds) The acid dissociation constant of amine compounds is determined using the following method. (1) Dissolve 0.2g of the amine compound in 30mL of purified water. (2) The acid dissociation constant (pKa) is calculated by titrating the solution obtained from (1) above with a 0.1 N perchloric acid-acetic acid solution using an automatic potentiometric titration apparatus (manufactured by Kyoto Electronics Co., Ltd., AT-610). Furthermore, the temperature during the measurement was set to 25±2℃.

[0072] (Amine value of amine compounds) The amine value was determined in accordance with JIS K7237-1995 using the following determination method. (1) Dissolve 0.1g of the amine compound in 20mL of acetic acid. (2) The amine value is calculated by titrating the solution obtained from (1) above with a 0.1 N perchloric acid-acetic acid solution using an automatic potentiometric titration apparatus (manufactured by Kyoto Electronics Co., Ltd., AT-610).

[0073] (Maximum endothermic temperature of amine compounds) For amine compounds, the following DSC measurement was performed to determine the maximum endothermic temperature of the amine compound. First, for the amine compound, differential scanning calorimetry (DSC) was performed using a DTG-60 (manufactured by Shimadzu Corporation) under conditions of a measurement temperature range of 23–350 °C, a heating rate of 10 °C / min, and a nitrogen atmosphere. The temperature at which the endothermic heat accompanying the volatilization of the amine compound reaches its maximum value was calculated from the resulting DSC curve, and this temperature was defined as the maximum endothermic temperature of the amine compound.

[0074] (Maximum dissociation temperature of carbon dioxide (CO2) in amine compounds) A carbon dioxide concentration meter and petri dishes were placed inside a desiccator (internal dimensions: 370mm × 260mm × 272mm) that could be opened and closed. Then, an amine compound (5 mmol) was added to the petri dish inside the desiccator, the door was immediately closed, and the amine compound was left to stand in the desiccator at 23°C and 50% RH for 24 hours. Furthermore, the initial concentration of carbon dioxide was adjusted to approximately 400 ppm. Next, the amine compound was removed from the desiccator, yielding an amine compound that had absorbed carbon dioxide. For the amine compound that had absorbed carbon dioxide, DSC measurement was performed as follows to determine the maximum carbon dioxide dissociation temperature of the amine compound. First, for the amine compound, differential scanning calorimetry (DSC) was performed using a differential calorimeter (product name: DTG-60, manufactured by Shimadzu Corporation) under the conditions of a measurement temperature range of 23–250 °C, a heating rate of 10 °C / min, and a nitrogen atmosphere. The temperature at which the heat absorbed during the release of carbon dioxide reached its maximum value was calculated from the resulting DSC curve, and this temperature was defined as the maximum carbon dioxide dissociation temperature of the amine compound.

[0075] (Specific surface area and pore volume of porous materials) The specific surface area and pore volume of porous materials are measured using a specific surface area and pore size distribution measuring device (product name: ASAP2020, manufactured by Shimadzu Corporation).

[0076] (Volume median particle size (D50) of porous materials) The particle distribution of porous materials was determined using a laser diffraction / scattering particle size distribution analyzer (manufactured by Malvern, product name "LMS-200e"). Furthermore, the particle size at which the cumulative volume frequency, calculated from the smallest particle size in the particle distribution, corresponds to 50% is defined as the volume median particle size (D50) of the porous material.

[0077] (Evaluation of carbon dioxide absorption capacity 1) In a nitrogen-purged glass container, 300 mg of an amine compound, 10 g of methanol, and 300 mg of porous material were added and stirred for 10 hours to homogenize the mixture. The resulting mixture was then placed at 40°C and 100 hPa to distill off the methanol. Next, it was vacuum dried at room temperature (23°C) for 24 hours to obtain a carbon dioxide absorbent. Next, 15 mg of the obtained carbon dioxide absorbent was placed in a differential calorimeter (product name: EXSTER TGD6200, manufactured by Hitachi High-Tech Corporation) and allowed to stand for 6 hours at 45°C in dry air. The increase in mass of the carbon dioxide absorbent was measured. For the gas used in the measurement, air (flow rate: 200 ml / min) was used for carbon dioxide absorption, and nitrogen (flow rate: 200 ml / min) was used for carbon dioxide removal. The amount of carbon dioxide absorbed by the carbon dioxide absorbent (first test) was calculated from the increase in mass of the carbon dioxide absorbent. The unit of carbon dioxide absorption in Table 1 is the amount of carbon dioxide absorbed per 1 g of carbon dioxide absorbent (mg).

[0078] After the first evaluation of carbon dioxide absorption capacity, the carbon dioxide absorbent was removed from the device and heated at 125°C for 30 minutes to remove the absorbed carbon dioxide and regenerate the carbon dioxide absorbent. Next, the carbon dioxide absorption capacity of the regenerated carbon dioxide absorbent was evaluated again, and the carbon dioxide absorption amount was measured (second time). Next, the carbon dioxide absorbent is removed from the device and heated at 125°C for 30 minutes to remove the absorbed carbon dioxide and regenerate the carbon dioxide absorbent. Next, the carbon dioxide absorption capacity of the regenerated carbon dioxide absorbent was evaluated again, and the carbon dioxide absorption amount was measured (3rd time). Here, the maintenance rate of carbon dioxide absorption is calculated based on the first carbon dioxide absorption.

[0079] In the examples and comparative examples, the following are used with respect to amine compounds and porous materials.

[0080] (amine compounds) 1,3-BAC-BisAP: hydride of the reactive adduct of 1,3-bis(aminomethyl)cyclohexane and acrylonitrile in a 1:2 (molar ratio) ratio (prepared according to Synthesis Example 1 below). 1,3-BAC-TetraAP: hydride of the reactive adduct of 1,3-bis(aminomethyl)cyclohexane and acrylonitrile in a 1:4 (molar ratio) ratio (prepared according to Synthesis Example 2 below). TETA: Triethylenetetramine (manufactured by Tokyo Chemical Industry Co., Ltd.), is a noncyclic amine compound containing one-tenth of a primary amine group, which accounts for 50 moles of the total amine group. AEP: 2-Aminoethylpiperazine (manufactured by Tokyo Chemical Industry Co., Ltd.) is a cyclic amine compound having a primary amino group comprising 33 mol% of the total amino groups.

[0081] (Synthetic Example 1: Manufacturing of 1,3-BAC-BisAP) (1) In a 100 mL round-bottom flask equipped with a stirrer, thermometer, argon inlet tube, dropping funnel, and cooling tube, 10.0 g of 1,3-bis(aminomethyl)cyclohexane (manufactured by Mitsubishi Gas Chemical Co., Ltd.) and 20.0 g of 2-propanol (manufactured by Fujifilm and Hikari Pure Chemical Co., Ltd.) were added. After stirring thoroughly under an argon gas flow, 7.5 g of acrylonitrile (manufactured by Sigma-Aldrich) was added dropwise over 10 minutes. After the addition was completed, the temperature was raised to 65 °C and maintained for 1 hour. Then, it was cooled to room temperature to obtain reaction solution (1). (2) In a tubular vertical hydrogenation reactor (glass, inner diameter 10 mm Φ), 7.0 g of a hydrogenation catalyst (trilobite type, diameter 1.2 mm Φ, Johnson Matthey Japan; HTCCo2000) with a cobalt content of 15% by mass was filled and kept at 120°C for 1 hour under a hydrogen gas flow. Then, the temperature was raised to 240°C and kept for more than 4 hours to reduce and activate the catalyst. After cooling, 14.8 g of 2-propanol, all of the above catalyst, and reaction liquid (1) were added to an autoclave (capacity 150 mL, material: SUS316L) equipped with a stirrer and heater. The gas phase was replaced with hydrogen. After pressurizing the autoclave to 3.5 MPaG, the temperature was raised while stirring and the liquid temperature was raised to 80°C after 20 minutes. Then, the pressure was adjusted to 8.0 MPaG. The reaction was then continued for 3 hours with hydrogen supplied continuously at a liquid temperature of 80°C and a pressure maintained at 8.0 MPaG. The reaction solution was then completely concentrated under vacuum to obtain 17.5 g of 1,3-BAC-BisAP. 1,3-BAC-BisAP has four amino groups in its molecule, including two primary amino groups. That is, 1,3-BAC-BisAP has 50 mol% of primary amino groups relative to all amino groups.

[0082] (Synthetic Example 2: Manufacturing of 1,3-BAC-TetraAP) (1) In a 300 mL round-bottom flask equipped with a stirrer, thermometer, argon inlet tube, dropping funnel, and cooling tube, 10 g of 1,3-bis(aminomethyl)cyclohexane (manufactured by Mitsubishi Gas Chemical Co., Ltd.), 100.0 g of 2-propanol (manufactured by Fujifilm and Koko Pure Chemical Co., Ltd.), and 100.0 g of distilled water were added. After stirring thoroughly under an argon gas flow, 18.6 g of acrylonitrile (manufactured by Sigma-Aldrich) was added dropwise over 10 minutes. After the addition was completed, the temperature was raised to 50 °C and maintained for 6 hours. Then, the temperature was raised to 80 °C, and an additional 37.2 g of acrylonitrile was added dropwise and maintained for 18 hours. After cooling to room temperature, the solvent was distilled off, thereby obtaining 25 g of the acrylonitrile 4-adduct of 1,3-bis(aminomethyl)cyclohexane. (2) In a high-pressure reactor (capacity 150 mL, material: SUS316L) equipped with a stirrer and heater, 0.75 g of a 15% by mass cobalt hydrogenation catalyst (trilobite type, diameter 1.2 mmΦ, manufactured by Johnson Matthey Japan; HTCCo2000), 60.0 g of 2-propanol, and 1.5 g of the acrylonitrile 4-adduct of 1,3-bis(aminomethyl)cyclohexane were added, and the gas phase was replaced with hydrogen. The temperature was increased while stirring, and after reaching 80°C, the pressure was increased to 6.0 MPa with hydrogen. Then, at 80°C, hydrogen was continuously supplied while maintaining the pressure at 6.0 MPa, and the reaction continued for 5 hours. The solvent was removed by distillation from the reaction liquid to obtain 1.5 g of 1,3-BAC-TetraAP. 1,3-BAC-TetraAP has 6 amino groups in its molecule, including 4 primary amino groups. That is, 1,3-BAC-TetraAP has 66.7 mol% of primary amino groups relative to all amino groups.

[0083] (Porous materials) Mesoporous silicon dioxide SBA15 (manufactured by Merck) Specific surface area (BET) measured by the BET method: 800 m² / g; median volumetric size (D₅₀): 100 μm; pore volume: 0.8 cm³ / g. Fumed silica QS-40 (manufactured by Tokuyama Corporation) Hydrophilic fumed silica, with a specific surface area of ​​370 m² / g and a median volumetric particle size (D50) of 10 μm, as measured by the BET method. Fumed silica RX-300 (manufactured by NIPPON AEROSIL) The specific surface area of ​​hydrophobically treated fumed silica, measured by the BET method, is 300 m² / g, and the median volumetric particle size (D50) is 20 μm. Mesoporous alumina PULAROX (manufactured by SAZOL) Specific surface area (BET method): 150 m² / g; median volumetric size (D₅₀): 35 μm; pore volume: 0.9 cm³ / g Porous carbon MJ(4)030 (manufactured by TOYO TANSO) Specific surface area measured by BET method: 670 m² / g; median volumetric particle size (D50): 5 μm; pore volume: 1.7 cm³ / g Synthetic adsorbent DIAION HP-20 (manufactured by Mitsubishi Chemical Corporation) Specific surface area (BET method): 590 m² / g; median volumetric size (D₅₀): 250 μm; pore volume: 1.3 cm³ / g

[0084] (Examples 1-2 and Comparative Examples 1-2) In Examples 1-2 and Comparative Examples 1-2, the amine compounds and porous materials shown in Table 1 were used, and the above evaluations were performed respectively. The results are shown in Table 1.

[0085] [Table 1] amine compounds Porous materials (B) Evaluation of CO2 absorption capacity 1 name structural Molecular weight [-] Maximum dissociation temperature of CO2 [°C] Maximum heat absorption temperature [°C] Amine value [mgKOH / g] pKa name CO2 absorption [mg CO2 / g] CO2 uptake retention rate [%) 1st time 2nd time 3rd time 1st time 2nd time 3rd time Example 1 1,3-BAC-BisAP 256.4 97.8 246.7 844 9.5 Mesoporous silicon dioxide SBA15 31.4 31.4 30.9 100.0 100.0 98.2 Example 2 1,3-BAC-tetraAP 370.6 102.3 298.2 890 9.8 Mesoporous silicon dioxide SBA15 35.5 35.5 35.1 100.0 100.0 98.8 Comparative Example 1 TETA 146.2 69.5 184.1 1535 10.3 Mesoporous silicon dioxide SBA15 47.6 37.0 24.6 100.0 77.6 51.7 Comparative Example 2 AEP 129.2 81.9 118.4 1154 10.1 Mesoporous silicon dioxide SBA15 16.5 1.6 1.5 100.0 9.7 9.1

[0086] As shown in Table 1, the carbon dioxide absorbents of Examples 1-2, which contain a cyclic amine compound (A) having at least 35 mol% of primary amine groups relative to all amine groups and a porous material (B), exhibit minimal reduction in carbon dioxide absorption even after repeated use. That is, the carbon dioxide absorbent of the present invention demonstrates improved reusability. In contrast, the carbon dioxide absorbents of Comparative Examples 1-2 show significant reduction in carbon dioxide absorption upon repeated use, indicating poor reusability.

[0087] (Examples 3-9, Comparative Examples 3-4: Evaluation of carbon dioxide absorption capacity under practical application conditions) The carbon dioxide absorbent is used under practical conditions to recover carbon dioxide from a mixture of gases containing water vapor in addition to carbon dioxide, such as outdoor air and indoor air, and combustion exhaust. Here, in Examples 3-9 and Comparative Examples 3-4, the amount of carbon dioxide absorbed and removed under humidification conditions that take into account the influence of water vapor in the gas was measured using a catalytic analysis apparatus (BELCATII; manufactured by MicrotracBEL) and the method described later to evaluate the carbon dioxide absorption capacity of the carbon dioxide absorbent.

[0088] (Evaluation of Carbon Dioxide Absorption Capacity 2: Evaluation of Heating Cycle of Carbon Dioxide Absorbent) (1) In a glass container purged with nitrogen, add 300 mg of amine compound, 10 g of methanol, and 300 mg of porous material and stir for 10 hours to homogenize. Then, place the resulting mixture at 40 °C and 100 hPa to distill off the methanol. Then, vacuum dry it at room temperature (23 °C) for 24 hours to obtain a carbon dioxide absorbent. (2) Next, 200 mg of the obtained carbon dioxide absorbent was filled into the reaction tube of the above-mentioned catalyst analyzer. After drying and degassing pretreatment by heating at 100°C for 1 hour in a nitrogen gas flow (flow rate: 100 ml / min), the reaction tube was kept at 40°C. Then, the introduced gas was switched to a 400 ppm carbon dioxide / nitrogen mixture (total flow rate: 1000 ml / min) humidified to 40°C and 40%RH (absorption step). At the same time, the change in the composition of the outlet gas of the catalyst analyzer over time was measured using a gas quality analyzer (BELMASS; MicrotracBEL). The breakthrough curve was obtained by measuring this change. After the carbon dioxide absorption reached saturation, the introduced gas was switched to nitrogen (flow rate: 500 ml / min) and heated to 80°C (detachment step). Then, the change in the composition of the outlet gas of the catalyst analyzer over time was measured using a gas quality analyzer. The amount of carbon dioxide absorbed by the carbon dioxide absorbent is calculated cumulatively from the start of absorption to saturation and the change in carbon dioxide outlet concentration, and is shown in Table 2 (evaluation of carbon dioxide absorption capacity for the first time). Furthermore, the amount of carbon dioxide removed from the carbon dioxide absorbent is calculated cumulatively from the time the introduced gas is switched to nitrogen until carbon dioxide becomes almost undetectable at the outlet and the change in carbon dioxide outlet concentration. (3) After the first evaluation of carbon dioxide absorption capacity, the carbon dioxide absorbent obtained by the above-mentioned separation step is regenerated and the above-mentioned (2) operation is repeated 9 times, for a total of 10 carbon dioxide absorption and separation steps. Based on the carbon dioxide absorption amount at the time of the first evaluation, the maintenance rate of carbon dioxide absorption amount at the time of the 5th and 10th evaluations is calculated.

[0089] (Evaluation of Carbon Dioxide Absorption Capacity 3: Evaluation of Carbon Dioxide Absorbent under Reduced Pressure Cycle) (1) In the reaction tube of the above-mentioned catalyst analysis device, 100 mg of carbon dioxide absorbent prepared in the same manner as described above was measured, and the absorbent temperature was maintained at 60°C. The pressure was reduced and the gas was vented for 1 hour for pretreatment. Next, the reaction tube was kept at 40°C, and the introduced gas was switched to a 400 ppm carbon dioxide / nitrogen mixture humidified to 40°C and 40%RH (total flow rate: 1000 ml / min) (absorption step). Simultaneously, a gas quality analyzer (BELMASS; MicrotracBEL) was used to measure the change in the composition of the outlet gas of the catalyst analysis device over time, thereby obtaining the flow curve. The amount of carbon dioxide absorbed by the carbon dioxide absorbent was calculated cumulatively from the start of absorption to saturation and the change in the outlet concentration of carbon dioxide, and is shown in Table 3 (evaluation of the first carbon dioxide absorption capacity). (2) The amount of carbon dioxide removed due to the decompression of the carbon dioxide absorbent is equivalent to the amount of carbon dioxide removed due to decompression, which will be absorbed later. Therefore, it is set as the amount of carbon dioxide absorbed when the carbon dioxide absorbent after carbon dioxide removal is used. Specifically, the absorbent that has absorbed carbon dioxide in (1) is kept at 40°C, and the vacuum pump is manually operated to decompress and exhaust the gas for 30 minutes (removal step). Then, 400 ppm of carbon dioxide / nitrogen mixed gas is introduced again using the same method as in (1). The change in the composition of the outlet gas over time is measured using a gas quality analyzer (BELMASS; MicrotracBEL). The result is obtained by measuring the change in the composition of the outlet gas over time. Furthermore, the ultimate vacuum at 30 minutes of decompression is 0.5 kPa. (3) After the first evaluation of carbon dioxide absorption capacity, the carbon dioxide absorbent obtained by regeneration through the separation step described in (2) above is subjected to the same steps (1) and separation step nine times, for a total of ten carbon dioxide absorption and separation steps. Based on the carbon dioxide absorption amount at the time of the first evaluation, the maintenance rate of carbon dioxide absorption amount at the time of the fifth and tenth evaluations is calculated. Furthermore, the units for carbon dioxide absorption in Tables 2 and 3 are the amount of carbon dioxide absorbed per 1g of carbon dioxide absorbent (mg).

[0090] [Table 2] amine compounds Porous materials (B) Absorption steps Detachment Steps Evaluation of CO2 absorption capacity 2 CO2 absorption [mg-CO2 / g] CO2 uptake retention rate [%) name name CO2 absorption conditions CO2 removal conditions 1st time 5th 10th 1st time 5th 10th Example 3 1,3-BAC-BisAP Mesoporous silicon dioxide SBA15 400ppm CO2 / N2 mixed gas at 40℃ and 40%RH for 2 hours 80℃ / normal pressure for 30 minutes 74.1 72.7 71.5 100 98.1 96.5 Example 4 1,3-BAC-tetraAP Mesoporous silicon dioxide SBA15 80.5 79.8 78.9 100 99.1 98.0 Example 5 1,3-BAC-BisAP Fumed silica QS-40 58.7 57.3 56.5 100 97.6 96.3 Example 6 1,3-BAC-BisAP Fumed silicon dioxide RX-300 57.2 56.1 55.0 100 98.1 96.2 Example 7 1,3-BAC-BisAP mesoporous alumina PULAROX 48.8 47.6 46.2 100 97.5 94.7 Example 8 1,3-BAC-BisAP Porous carbon MJ(4)030 48.2 45.8 44.9 100 95.0 93.2 Example 9 1,3-BAC-BisAP Synthetic adsorbent DIAION HP-20 51.3 50.3 49.5 100 98.1 96.5 Comparative Example 3 TETA Mesoporous silicon dioxide SBA15 76.3 54.3 35.7 100 71.2 46.8 Comparative Example 4 AEP Mesoporous silicon dioxide SBA15 31.2 1.5 1.4 100 4.8 4.5

[0091] [Table 3] amine compounds Porous materials (B) Absorption steps Detachment Steps Evaluation of CO2 absorption capacity 3 CO2 absorption [mg-CO2 / g] CO2 uptake retention rate [%) name name CO2 absorption conditions CO2 removal conditions 1st time 5th 10th 1st time 5th 10th Example 3 1,3-BAC-BisAP Mesoporous silicon dioxide SBA15 400ppm CO2 / N2 mixed gas at 40℃ and 40%RH for 2 hours 40℃ / 0.5kPa for 30 minutes 74.1 73.5 72.5 100 99.2 97.8 Example 4 1,3-BAC-tetraAP Mesoporous silicon dioxide SBA15 80.5 80.1 79.5 100 99.5 98.8 Example 5 1,3-BAC-BisAP Fumed silica QS-40 58.7 57.3 56.3 100 97.6 95.9 Example 6 1,3-BAC-BisAP Fumed silicon dioxide RX-300 57.2 56.1 55.9 100 98.1 97.7 Example 7 1,3-BAC-BisAP mesoporous alumina PULAROX 48.8 47.9 46.9 100 98.2 96.1 Example 8 1,3-BAC-BisAP Porous carbon MJ(4)030 48.2 45.6 44.1 100 94.6 91.5 Example 9 1,3-BAC-BisAP Synthetic adsorbent DIAION HP-20 51.3 50.6 49.8 100 98.6 97.1 Comparative Example 3 TETA Mesoporous silicon dioxide SBA15 76.2 56.9 43.7 100 74.7 57.3 Comparative Example 4 AEP Mesoporous silicon dioxide SBA15 31.2 16.5 16.1 100 52.9 51.6

[0092] As shown in Tables 2 and 3, the carbon dioxide absorbents of Examples 3-9, which contain a cyclic amine compound (A) having at least 35 moles of primary amine groups relative to all amine groups and a porous material (B), exhibit minimal reduction in carbon dioxide absorption and good reusability even when reused with a mixed gas containing water vapor in addition to carbon dioxide. In contrast, the carbon dioxide absorbents of Comparative Examples 3-4 show significant reduction in carbon dioxide absorption and poor reusability when reused. [Industrial applicability]

[0093] According to the present invention, it is possible to provide: a carbon dioxide absorbent with improved reusability, a method for recovering carbon dioxide using the carbon dioxide absorbent, and a carbon dioxide separation and recovery apparatus.

[0094] 100: Carbon dioxide separation and recovery unit 1: Absorption device 2: Disengagement device 3: Connecting parts 11,21: Reaction Tower 12,22: Absorbent holding section 12a: Carbon dioxide absorbent 13: Gas Supply Department 21: Reaction Tower 22a: Carbon dioxide absorbent that has absorbed carbon dioxide 23: Gas Exhaust Section 24: Absorbent Discharge Section

Claims

1. A carbon dioxide absorbent comprising a cyclic amine compound (A) and a porous material (B); the cyclic amine compound (A) having at least 35 moles of primary amines relative to all amines; the cyclic amine compound (A) comprising at least one of the group consisting of an amine compound (a1) represented by the following formula (1) and an amine compound (a2) having a heterocyclic structure selected from oxygen-containing heterocyclic structures and sulfur-containing heterocyclic structures; in the above formula (1), R1 to R4 each independently represent a hydrogen atom, or may have a hydrocarbon group having 1 or more and 10 or less carbon atoms with a substituent selected from at least one of amine, cyano, and phenyl; R5 to R10 each independently represent a hydrogen atom or a hydrocarbon group having 1 or more and 4 or less carbon atoms; x and y each independently represent an integer of 0 or more and 6 or less; x+y is 1 or more and 6 or less; p and q each independently represent an integer of 0 or more and 4 or less; and at least one of p and q is 1 or more.

2. The carbon dioxide absorbent as requested in item 1, wherein, At least a portion of the cyclic amine compound (A) is supported on the porous material (B).

3. The carbon dioxide absorbent as requested in item 1 or 2, wherein, The porous material (B) comprises at least one selected from the group consisting of silicon dioxide and aluminum oxide.

4. The carbon dioxide absorbent as requested in item 1 or 2, wherein, The porous material (B) is in particle form.

5. The carbon dioxide absorbent as requested in item 4, wherein, The volume median particle size (D50) of the porous material (B), as measured by laser diffraction / scattering particle size distribution determination, is greater than 1 μm and less than 500 μm.

6. The carbon dioxide absorbent as requested in item 1 or 2, wherein, The specific surface area of ​​the porous material (B), as measured by the BET method, is above 2 m² / g and below 3000 m² / g.

7. The carbon dioxide absorbent as requested in item 1 or 2, wherein, The pore volume of the porous material (B) is above 0.1 cm3 / g and below 5.0 cm3 / g.

8. The carbon dioxide absorbent as requested in item 1 or 2, wherein, The content of the cyclic amine compound (A) is more than 0.1 parts by mass and less than 1000 parts by mass relative to 100 parts by mass of the porous material (B).

9. The carbon dioxide absorbent as requested in item 1 or 2, wherein, The maximum dissociation temperature of carbon dioxide of the cyclic amine compound (A) was determined to be below 140°C using the following method: The cyclic amine compound (A) that had absorbed carbon dioxide was heated from 23°C to 250°C at a heating rate of 10°C / min. The temperature at which the heat absorbed by the carbon dioxide was released reached its maximum value was measured and defined as the maximum dissociation temperature of the carbon dioxide.

10. The carbon dioxide absorbent as requested in item 1 or 2, wherein, The molecular weight of the cyclic amine compound (A) is above 90 and below 1000.

11. The carbon dioxide absorbent as requested in item 1 or 2, wherein, The amine value of the cyclic amine compound (A) is above 400 mg KOH / g and below 1500 mg KOH / g.

12. The carbon dioxide absorbent as requested in item 1 or 2, wherein, The cyclic amine compound (A) has an amine group number of 1 or more and 6 or less.

13. The carbon dioxide absorbent as requested in item 1 or 2, wherein, The cyclic structure of the cyclic amine compound (A) includes at least one selected from the group consisting of 5-membered rings and 6-membered rings.

14. The carbon dioxide absorbent as requested in item 1 or 2, wherein, The cyclic amine compound (A) comprises at least one selected from the group consisting of bis(aminomethyl)cyclohexane and its derivatives, limonene diamine and its derivatives, isophorone diamine and its derivatives, 2,5-diaminomethylfuran and its derivatives, 2,5-bis(aminomethyl)tetrahydrofuran and its derivatives, furfural methylamine and its derivatives, tetrahydrofuran methylamine and its derivatives, 4-aminomethyltetrahydropiperanan and its derivatives, 4-(2-aminoethyl) thioline and its derivatives, and 2-thiophene methylamine and its derivatives.

15. A method for recovering carbon dioxide, comprising using a carbon dioxide absorbent as described in any one of claims 1 to 14.

16. The carbon dioxide recovery method as described in claim 15, wherein, The carbon dioxide recovery method comprises the following steps: an absorption step, in which the carbon dioxide absorbent is brought into contact with a gas containing carbon dioxide and the carbon dioxide absorbent is brought into contact with the carbon dioxide absorbent; and a separation step, in which carbon dioxide is separated from the carbon dioxide absorbent that has absorbed carbon dioxide in the absorption step; the separation step comprises at least one step selected from the group consisting of (I) to (III) below, (I) a step of placing the carbon dioxide absorbent that has absorbed carbon dioxide under reduced pressure, (II) a step of bringing the carbon dioxide absorbent that has absorbed carbon dioxide into contact with an inert gas that does not contain carbon dioxide, and (III) a step of heating the carbon dioxide absorbent that has absorbed carbon dioxide.

17. The carbon dioxide recovery method as described in claim 16, wherein, In this absorption step, the temperature at which the carbon dioxide absorbent comes into contact with the carbon dioxide-containing gas is above 0°C and below 60°C.

18. The carbon dioxide recovery method as described in claim 17, wherein, The heating temperature in step (III) is above 50°C and below 120°C.

19. A carbon dioxide separation and recovery apparatus, comprising: an absorption device having a mechanism for contacting a carbon dioxide absorbent as claimed in any one of claims 1 to 14 with a gas containing carbon dioxide and for the carbon dioxide absorbent to absorb carbon dioxide; and a separation device having a mechanism for separating carbon dioxide from the carbon dioxide absorbent that has absorbed carbon dioxide.

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