Compound, compound for carbon dioxide absorbent, carbon dioxide absorbent, carbon dioxide separation method, carbon dioxide separation and recovery method, and apparatus using carbon dioxide absorbent

Abstract

To provide a novel phosphorus compound having an alkyl group, in which an amino group is bonded to the alkyl group.SOLUTION: A compound is represented by the following general formula (1) (where a, b, and c represent integers of 1 or more and 10 or less, X is selected from S and Se, and R1, R2, and R3 each independently represent a hydroxy group, a primary amino group, a secondary amino group, or a tertiary amino group, and at least one of R1, R2, and R3 is a primary amino group, a secondary amino group, or a tertiary amino group).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a compound, a compound for a carbon dioxide absorbent, a carbon dioxide absorbent, a carbon dioxide separation method, a carbon dioxide separation and capture method, and an apparatus using the carbon dioxide absorbent. [Background technology]

[0002] In recent years, the concentration of greenhouse gases such as carbon dioxide and methane in the atmosphere has continued to increase due to increased consumption of fossil fuels such as oil and coal in industrial activities, as well as deforestation, and global warming, which is causing temperatures to rise on a global scale, is progressing.If global warming continues at this rate, it is thought that serious impacts will appear in various areas, such as desertification of the earth's surface, rising sea levels, and changes in ecosystems.

[0003] Under these circumstances, in order to prevent global warming, attention is being paid to technologies that capture carbon dioxide as well as curbing carbon dioxide emissions with the aim of reducing greenhouse gases. Carbon dioxide capture technologies include chemical absorption, physical absorption, solid absorption, and membrane separation, but chemical absorption is the most widely used method as it can handle a wide range of concentrations. In this chemical absorption method, carbon dioxide is absorbed into a liquid through a chemical reaction, and the absorbent liquid is heated to release and capture the carbon dioxide.

[0004] As a liquid used for absorbing carbon dioxide, for example, Patent Document 1 discloses an ionic liquid having an aminium cation having one or more primary or secondary amino groups and an ethylenediamine or propylenediamine skeleton. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-10760 [Patent Document 2] Japanese Patent Application Publication No. 4-39324 Summary of the Invention [Problem to be solved by the invention]

[0006] However, although the carbon dioxide absorbent described in Patent Document 1 can absorb carbon dioxide at room temperature, there is room for further improvement in the carbon dioxide absorption performance. Moreover, since it is necessary to recover the absorbed carbon dioxide after absorption by the carbon dioxide absorbent, it is also required that the absorbed carbon dioxide be desorbed well.

[0007] Meanwhile, trialkylphosphine compounds having an alkyl group to which a primary amino group is bonded, such as trialkylphosphine oxides, are used as curing agents for epoxy resins, for example. Patent Document 2 discloses a curing agent for epoxy resins containing aminoalkylphosphine oxide as an active ingredient.

[0008] Such trialkylphosphine oxides have a phosphine oxide structure (αP=O, where α is an alkyl group which may have a substituent) and an amino group (-NH) in the molecule, and therefore are expected to have a variety of applications in addition to being used as curing agents for epoxy resins.

[0009] In trialkylphosphine oxides with amino groups, oxygen atoms are bonded to the phosphorus atoms, which allows the epoxy resins they are used with to have improved physical properties, particularly flame retardancy and adhesiveness. It is anticipated that compounds with different physical properties will be needed to expand their applications.

[0010] Therefore, an object of the present invention is to solve at least one of the following problems. That is, an object of the present invention is to provide a novel phosphorus compound having an alkyl group to which an amino group is bonded. Another object of the present invention is to provide a compound for a carbon dioxide absorbent and a carbon dioxide absorbent that have excellent carbon dioxide absorption performance. Another object of the present invention is to provide a carbon dioxide absorbent that, in addition to the above-mentioned carbon dioxide absorption performance, can easily desorb carbon dioxide when the absorbent is regenerated. Another object of the present invention is to provide a carbon dioxide separation method and a carbon dioxide separation and capture method using the carbon dioxide absorbent, and an apparatus using the carbon dioxide absorbent. [Means for solving the problem]

[0011] The present inventors have conducted extensive research in light of the above-mentioned circumstances, and as a result have found that a trialkylphosphine sulfide or trialkylphosphine selenide having an alkyl group to which a primary amino group, a secondary amino group, or a tertiary amino group is bonded as the alkyl group, i.e., a compound represented by the following general formula (1), (1) exhibits better carbon dioxide absorption performance than conventional compounds, or (2) exhibits good carbon dioxide desorption properties after carbon dioxide absorption, and have thus completed the present invention.

[0012] [ka]

[0013] (In the formula, a, b, and c represent integers of 1 or more and 10 or less, and R 1 , R 2 and R 3 each independently represents a hydroxy group, a primary amino group, a secondary amino group, or a tertiary amino group; R 1 , R 2 and R 3 At least one of is a primary amino group, a secondary amino group, or a tertiary amino group.

[0014] That is, the present invention (1) relates to a compound represented by the following general formula (1):

[0015] [ka]

[0016] (In the formula, a, b, and c represent integers of 1 or more and 10 or less, and R 1 , R 2 and R 3 each independently represents a hydroxy group, a primary amino group, a secondary amino group, or a tertiary amino group; R 1 , R 2 and R 3 At least one of is a primary amino group, a secondary amino group, or a tertiary amino group. The present invention provides a compound represented by the formula:

[0017] The present invention (2) also provides a compound for use as a carbon dioxide absorbent, which is the compound of the present invention (1).

[0018] The present invention (3) also provides a carbon dioxide absorbent characterized by containing the compound for a carbon dioxide absorbent of the present invention (2).

[0019] The present invention (4) also provides a carbon dioxide separation method, comprising a carbon dioxide separation step of contacting a mixed gas containing carbon dioxide with the carbon dioxide absorbent of the present invention (3) to cause the carbon dioxide absorbent to absorb the carbon dioxide in the mixed gas, thereby separating carbon dioxide from the mixed gas.

[0020] The present invention (5) also provides a method for separating and capturing carbon dioxide, comprising: a carbon dioxide separation step of bringing a mixed gas containing carbon dioxide into contact with the carbon dioxide absorbent of the present invention (3) to cause the carbon dioxide absorbent to absorb the carbon dioxide in the mixed gas, thereby separating carbon dioxide from the mixed gas; and a carbon dioxide recovery step of heating the carbon dioxide absorbent that has absorbed carbon dioxide in the carbon dioxide separation step at a temperature of 60°C or higher and 150°C or lower to desorb carbon dioxide from the carbon dioxide absorbent that has absorbed the carbon dioxide, thereby regenerating the carbon dioxide absorbent and recovering the desorbed carbon dioxide.

[0021] The present invention (6) also provides an apparatus characterized by using the carbon dioxide absorbent of the present invention (2). [Effects of the Invention]

[0022] According to the present invention, a novel phosphorus compound having an alkyl group to which an amino group is bonded can be provided. Moreover, according to the present invention, it is possible to provide a compound for a carbon dioxide absorbent and a carbon dioxide absorbent that have excellent carbon dioxide absorption performance. Furthermore, according to the present invention, it is possible to provide a carbon dioxide absorbent that, in addition to the above-mentioned carbon dioxide absorption performance, can easily desorb carbon dioxide when the absorbent is regenerated. Furthermore, according to the present invention, it is possible to provide a carbon dioxide separation method and a carbon dioxide separation and capture method using the carbon dioxide absorbent, and an apparatus using the carbon dioxide absorbent. DETAILED DESCRIPTION OF THE INVENTION

[0023] The present invention will be described below based on preferred embodiments. The compound of the present invention is represented by the following general formula (1):

[0024] [ka]

[0025] (In the formula, a, b, and c represent integers of 1 or more and 10 or less, and R 1 , R 2 and R 3 each independently represents a hydroxy group, a primary amino group, a secondary amino group, or a tertiary amino group; R 1 , R 2 and R 3 At least one of is a primary amino group, a secondary amino group, or a tertiary amino group. It is a compound represented by the formula:

[0026] In general formula (1), X is selected from S and Se. S represents a sulfur atom, and Se represents a selenium atom. In other words, the compound represented by general formula (1) is a trialkylphosphine sulfide compound or a trialkylphosphine selenide compound.

[0027] The compound represented by general formula (1) has a phosphine sulfide structure (P=S) or a phosphine selenide structure (P=Se), and therefore has high heat resistance. When used as a carbon dioxide absorbent, the compound has a low vapor pressure and is almost non-volatile within a heating temperature range during regeneration after carbon dioxide absorption, for example, a heating temperature range of 60°C or higher and 150°C or lower.

[0028] In general formula (1), a, b, and c represent integers of 1 or more and 10 or less, preferably 1 or more and 4 or less, and more preferably 3 or more and 4 or less. The numbers a, b, and c may be the same or different, but are preferably the same from the viewpoint of ease of synthesis. In the present invention, it is particularly preferred that a, b, and c are each 3 from the viewpoint of industrial availability.

[0029] R in general formula (1) 1 , R 2 and R 3 each independently represents a hydroxy group (-OH), a primary amino group (-NH2), a secondary amino group (-NH-β, where β represents an optionally substituted alkyl group), or a tertiary amino group (-Nβ2, where β represents an optionally substituted alkyl group). 1 , R 2 and R 3 At least one of R is a primary amino group, a secondary amino group, or a tertiary amino group. 1 , R 2 and R 3 may be the same or different, but from the viewpoint of ease of synthesis, R 1 , R 2 and R 3 At least one of the amino groups is a primary amino group, a secondary amino group, or a tertiary amino group, and it is preferable that all of the amino groups are primary amino groups, a secondary amino group, or a tertiary amino group.

[0030] R 1 , R 2 and R 3 When used as a carbon dioxide absorbent, the amount of carbon dioxide absorbed increases. In the general formula (1), when X is S, R 1 , R 2 , R 3 are each a primary amino group, i.e., a phosphine sulfide having three primary amino groups is particularly preferred. When X is Se, R 1 , R 2 , R 3 are each a primary amino group, that is, a phosphine selenide having three primary amino groups is particularly preferred.

[0031] R 1 , R 2 and R 3 In terms of excellent oxidation resistance and, when used in a carbon dioxide absorbent, excellent desorption properties of absorbed carbon dioxide, a secondary amino group or a tertiary amino group is preferred, and a secondary amino group is particularly preferred. In terms of excellent oxidation resistance and, when used in a carbon dioxide absorbent, excellent desorption properties of absorbed carbon dioxide, R 1 , R 2 and R 3 is preferably a secondary amino group or a tertiary amino group, and R 1 , R 2 and R 3 In general formula (1), it is particularly preferable that all of R 1 , R 2 and R 3 One or two of the groups may be primary amino groups, but the compound represented by general formula (1) preferably has fewer primary amino groups, and particularly preferably has no primary amino groups, in terms of excellent oxidation resistance and, when used as a carbon dioxide absorbent, excellent desorption property of absorbed carbon dioxide.

[0032] R 1 , R 2 and R3 The secondary amino group in the above formula is an amino group having one hydrogen atom and one substituent bonded thereto, and the tertiary amino group is an amino group having two substituents bonded thereto. Examples of the substituent bonded to the secondary amino group or the tertiary amino group include alkyl groups, alkyl groups having a functional group, cycloalkyl groups, halogenated alkyl groups, alkoxy groups, and halogen atoms. The tertiary amino group also includes cyclic amino groups. Examples of the functional group in the alkyl group having a functional group include hydroxyl groups, amino groups, carboxyl groups, mercapto groups, amide groups, carboxymethyl groups, carboxyethyl groups, and sulfonic acid groups. In the present invention, from the viewpoint of oxidation resistance, R 1 , R 2 and R 3 The secondary amino group or tertiary amino group in the above is preferably an amino group substituted with an alkyl group having from 1 to 10 carbon atoms, more preferably an amino group substituted with an alkyl group having from 1 to 4 carbon atoms. The alkyl group includes a linear alkyl group, a branched alkyl group, and a cyclic alkyl group.

[0033] Specific examples of the linear alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, an n-decyl group, etc. In the present invention, from the viewpoint of ease of synthesis, a methyl group, an ethyl group, an n-propyl group, and an n-butyl group are more preferred.

[0034] Specific examples of the branched alkyl group having 1 to 10 carbon atoms include an isopropyl group, an isobutyl group, a s-butyl group, a t-butyl group, an isopentyl group, a s-pentyl group, a t-pentyl group, an isohexyl group, a s-hexyl group, a t-hexyl group, an ethylhexyl group, etc. In the present invention, an isopropyl group is more preferred from the viewpoint of ease of synthesis.

[0035] Specific examples of the cyclic alkyl group having 1 to 10 carbon atoms include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a 2-methylcyclopentyl group, a 3-methylcyclopentyl group, a cycloheptyl group, a 2-methylcyclohexyl group, a 3-methylcyclohexyl group, a 4-methylcyclohexyl group, a cyclooctyl group, a 2-methylcycloheptyl group, a 3-methylcycloheptyl group, a 4-methylcycloheptyl group, a 5-methylcycloheptyl group, etc. In the present invention, a cyclohexyl group is more preferred from the viewpoint of ease of synthesis.

[0036] When the compound of the present invention is used as a carbon dioxide absorbent, it can exhibit excellent carbon dioxide absorption performance. Furthermore, even when the absorbed carbon dioxide is desorbed to regenerate the absorbent, the ability to absorb carbon dioxide is restored, and the compound can also serve as a regenerated carbon dioxide absorbent having excellent carbon dioxide absorption performance. 1 , R 2 and R 3 is particularly preferably a primary amino group or a secondary amino group substituted with a methyl group, an ethyl group or an n-propyl group.

[0037] Examples of the phosphine sulfide compound represented by general formula (1) include tris(3-aminopropyl)phosphine sulfide, tris(3-(N-ethylaminopropyl))phosphine sulfide, tris(3-(N-methylaminopropyl))phosphine sulfide, tris(3-(N-(n-propyl)aminopropyl))phosphine sulfide, bis(3-(N-ethylaminopropyl))(3-aminopropyl)phosphine sulfide, bis(3-aminopropyl)(3-(N-ethylaminopropyl))phosphine sulfide, bis(3-(N-methylaminopropyl))(3-aminopropyl)phosphine sulfide, and bis(3-aminopropyl)(3-(N-methylaminopropyl))phosphine sulfide. Examples of the phosphine selenide compound represented by the general formula (1) include tris(3-aminopropyl)phosphine selenide, tris(3-(N-ethylaminopropyl))phosphine selenide, tris(3-(N-methylaminopropyl))phosphine selenide, tris(3-(N-(n-propyl)aminopropyl))phosphine selenide, bis(3-(N-ethylaminopropyl))(3-aminopropyl)phosphine selenide, bis(3-aminopropyl)(3-(N-ethylaminopropyl))phosphine selenide, bis(3-(N-methylaminopropyl))(3-aminopropyl)phosphine selenide, and bis(3-aminopropyl)(3-(N-methylaminopropyl))phosphine selenide.

[0038] The compound for a carbon dioxide absorbent of the present invention has the following general formula (1):

[0039] [ka]

[0040] (In the formula, a, b, and c represent integers of 1 or more and 10 or less, and R 1 , R 2 and R 3 each independently represents a hydroxy group, a primary amino group, a secondary amino group, or a tertiary amino group; R 1 , R 2 and R 3At least one of is a primary amino group, a secondary amino group, or a tertiary amino group. The compound for use as a carbon dioxide absorbent is a compound represented by the formula:

[0041] The compound for a carbon dioxide absorbent of the present invention can absorb carbon dioxide by reacting the primary amino group, secondary amino group, or tertiary amino group of the compound represented by general formula (1) with carbon dioxide. In other words, the compound of the present invention is a compound for a carbon dioxide absorbent that is used as a substance for absorbing carbon dioxide in a carbon dioxide absorbent. The compound represented by general formula (1) related to the compound for a carbon dioxide absorbent of the present invention is the same as the compound represented by general formula (1) related to the compound of the present invention, except as described below.

[0042] The carbon dioxide absorbent of the present invention is a carbon dioxide absorbent characterized by containing the compound for a carbon dioxide absorbent of the present invention. That is, the carbon dioxide absorbent of the present invention is a carbon dioxide absorbent characterized by containing a compound represented by general formula (1). In the carbon dioxide absorbent of the present invention, the phosphine sulfide or phosphine selenide represented by general formula (1) absorbs carbon dioxide. The compound represented by general formula (1) related to the carbon dioxide absorbent of the present invention is the same as the compound represented by general formula (1) related to the compound of the present invention.

[0043] The phosphine sulfide compound represented by general formula (1) used in the carbon dioxide absorbent of the present invention includes tris(3-aminopropyl)phosphine sulfide, tris(3-(N-ethylaminopropyl))phosphine sulfide, tris(3-(N-methylaminopropyl))phosphine sulfide, tris(3-(N-(n-propyl)aminopropyl))phosphine sulfide, bis(3-(N-ethylaminopropyl))(3-aminopropyl)phosphine sulfide, bis(3-aminopropyl)(3-(N-ethylaminopropyl))phosphine sulfide, bis(3-(N-methylaminopropyl))(3-aminopropyl)phosphine sulfide, bis(3-aminopropyl)(3-(N-methylaminopropyl))phosphine sulfide, bis(3-aminopropyl)(3-(N-methylaminopropyl))phosphine sulfide, Examples of the phosphine selenide compound represented by general formula (1) used in the carbon dioxide absorbent of the present invention include tris(3-aminopropyl)phosphine selenide, tris(3-(N-ethylaminopropyl))phosphine selenide, tris(3-(N-methylaminopropyl))phosphine selenide, tris(3-(N-(n-propyl)aminopropyl))phosphine selenide, bis(3-(N-ethylaminopropyl))(3-aminopropyl)phosphine selenide, bis(3-aminopropyl)(3-(N-ethylaminopropyl))phosphine selenide, bis(3-(N-methylaminopropyl))(3-aminopropyl)phosphine selenide, and bis(3-aminopropyl)(3-(N-methylaminopropyl))phosphine selenide.

[0044] R 1 , R 2 and R 3 In the general formula (1), when X is S, R 1 , R 2 , R 3 are each a primary amino group, i.e., a phosphine sulfide having three primary amino groups is particularly preferred. When X is Se, R 1 , R 2 , R 3are each a primary amino group, that is, a phosphine selenide having three primary amino groups is particularly preferred. 1 , R 2 and R 3 In the case where all of the above are primary amino groups, examples include tris(3-aminopropyl)phosphine sulfide and tris(3-aminopropyl)phosphine selenide.

[0045] The compound represented by general formula (1) used in the carbon dioxide absorbent of the present invention includes R 1 , R 2 and R 3 In the compounds represented by general formula (1), those in which R are both secondary amino groups are preferred in that they have excellent oxidation resistance, are excellent in durability when subjected to repeated absorption and desorption of carbon dioxide, and are excellent in desorption of absorbed carbon dioxide. 1 , R 2 and R 3 and n-methylaminopropyl))phosphine sulfide, tris(3-(N-ethylaminopropyl))phosphine sulfide, tris(3-(N-methylaminopropyl))phosphine sulfide, tris(3-(N-(n-propyl)aminopropyl))phosphine sulfide, tris(3-(N-ethylaminopropyl))phosphine selenide, tris(3-(N-methylaminopropyl))phosphine selenide, and tris(3-(N-(n-propyl)aminopropyl))phosphine selenide.

[0046] The carbon dioxide absorbent of the present invention can contain two or more compounds for carbon dioxide absorbents of the present invention. That is, the carbon dioxide absorbent of the present invention can contain two or more compounds represented by general formula (1). For example, the carbon dioxide absorbent of the present invention can contain a compound represented by general formula (1) in which R 1 , R 2 and R 3 Both of these have primary amino groups, and R 1 , R 2 and R 3a mixture of R in which one is a primary amino group and two are hydroxyl groups, secondary amino groups, or tertiary amino groups; 1 , R 2 and R 3 Both of these have secondary amino groups, and R 1 , R 2 and R 3 and a mixture of compounds in which two of the groups are secondary amino groups and one is a hydroxy group, a primary amino group, or a tertiary amino group, and compounds represented by general formula (1), in which R 1 , R 2 and R 3 Both of these have secondary amino groups, and R 1 , R 2 and R 3 two of which are secondary amino groups and one of which is a hydroxy group, a primary amino group, or a tertiary amino group; and R 1 , R 2 and R 3 a mixture of R in which one is a secondary amino group and two are hydroxy groups, primary amino groups, or tertiary amino groups; 1 , R 2 and R 3and a mixture in which one or all of a, b, and c are different from the others. Examples of the mixture of two or more compounds represented by general formula (1) include tris(3-aminopropyl)phosphine sulfide, tris(3-(N-ethylaminopropyl))phosphine sulfide, tris(3-(N-methylaminopropyl))phosphine sulfide, tris(3-(N-(n-propyl)aminopropyl))phosphine sulfide, bis(3-(N-ethylaminopropyl))(3-aminopropyl)phosphine sulfide, bis(3-aminopropyl)(3-(N-ethylaminopropyl))phosphine sulfide, bis(3-(N-methylaminopropyl))(3-aminopropyl)phosphine sulfide, bis(3-aminopropyl)(3-(N-methylaminopropyl))phosphine sulfide, bis(3-aminopropyl)(3-(N-methylaminopropyl))phosphine sulfide, bis(3-aminopropyl)(3-(N-methylaminopropyl))phosphine sulfide. and mixtures of two or more selected from the group consisting of bis(3-aminopropyl)phosphine selenide, tris(3-(N-ethylaminopropyl))phosphine selenide, tris(3-(N-methylaminopropyl))phosphine selenide, tris(3-(N-(n-propyl)aminopropyl))phosphine selenide, bis(3-(N-ethylaminopropyl))(3-aminopropyl)phosphine selenide, bis(3-aminopropyl)(3-(N-ethylaminopropyl))phosphine selenide, bis(3-(N-methylaminopropyl))(3-aminopropyl)phosphine selenide, and bis(3-aminopropyl)(3-(N-methylaminopropyl))phosphine selenide.

[0047] The proportion of primary amino groups in all amino groups of all compounds represented by general formula (1) used in the carbon dioxide absorbent of the present invention is preferably 50.0 mol% or more, more preferably 80.0 mol% or more, and particularly preferably 100.0 mol%, in order to increase the amount of carbon dioxide absorbed. Furthermore, in terms of excellent oxidation resistance, the proportion of primary amino groups in all amino groups of all compounds represented by general formula (1) used in the carbon dioxide absorbent of the present invention is preferably 50.0 mol% or less, more preferably 30.0 mol% or less, still more preferably 20.0 mol% or less, and particularly preferably 0.0 mol%. In the present invention, the ratio of primary amino groups to all amino groups in the compound represented by the general formula (1) is 1 Determined by H-NMR.

[0048] In the carbon dioxide absorbent of the present invention, the form of the compound represented by general formula (1) is not particularly limited, and may be, for example, supported on a carrier, dissolved in an aqueous solvent, or present as a mixture with a soluble organic solvent or an amine compound.

[0049] A carbon dioxide absorbent of a first embodiment of the present invention is a carbon dioxide absorbent characterized by comprising a porous carrier and a compound for a carbon dioxide absorbent of the present invention supported on the porous carrier. That is, the carbon dioxide absorbent of the first embodiment of the present invention is a carbon dioxide absorbent characterized by comprising a porous carrier and a compound represented by general formula (1) supported on the porous carrier. In the carbon dioxide absorbent of the first embodiment of the present invention, the compound represented by general formula (1), which is a liquid, is taken into the pores of the porous carrier and physically adsorbed, so that the compound represented by general formula (1) is supported on the porous carrier and exists therein.

[0050] The porous carrier for the carbon dioxide absorbent of the first embodiment of the present invention is not particularly limited as long as it has a porous structure having a large number of pores therein and can incorporate a compound represented by general formula (1) into the internal pores and physically adsorb and retain the compound represented by general formula (1) within the pores. Examples of porous carriers include activated carbon, silica gel, layered silicate, mesoporous silica, zeolite, vermiculite, molecular sieve, porous silica, diatomaceous earth, porous resin, porous fiber, porous metal-organic framework, porous alumina, porous ceramic, porous concrete, activated clay, and clay minerals. Activated carbon, silica gel, zeolite, and molecular sieve are preferred because they can increase the amount of the compound represented by general formula (1) supported. Furthermore, when the porous carrier is a porous body capable of retaining water within its pores, such as activated carbon, silica gel, zeolite, or molecular sieve, if the gas to be treated containing carbon dioxide contains moisture, the moisture in the gas to be treated is adsorbed into the pores of the porous body, making it possible to prevent the compound for the carbon dioxide absorbent from eluting from the porous body, and this is preferable in that it enhances the carbon dioxide absorption performance of the carbon dioxide absorbent. There are no particular restrictions on the porous body capable of retaining water within its pores, as long as it can retain water within its pores, but examples include those that can retain water at a moisture content of 5 to 30% by mass, preferably 10 to 25% by mass.

[0051] The BET specific surface area of ​​the porous support is preferably 1.0×10 1 ~5.0×10 3 m 2 / g, preferably 1.0 × 10 2 ~2.0×10 3 m 2 The pore volume of the porous support measured by a gas adsorption method is preferably 0.1 to 2.0 mL / g, and more preferably 0.3 to 1.5 mL / g.

[0052] The shape of the porous carrier may be, for example, granular, powdery, fibrous, plate-like, cylindrical, honeycomb, etc. Among these, granular or powdery shapes are preferred from the viewpoint of contact with a mixed gas containing carbon dioxide and packing into packing equipment such as a column or tower. The porous carrier may also be in the form of a molded body.

[0053] Among the porous supports, activated carbon, silica gel, zeolite, and molecular sieves are preferred from the viewpoint of ease of handling and ability to easily support the liquid compound represented by general formula (1), and activated carbon and silica gel are particularly preferred.

[0054] Various types of activated carbon can be used in the present invention, including activated carbon made from raw materials such as wood, coconut shells, coal, petroleum pitch, coke, and coal tar. The activated carbon may be a molded product. In addition to the above-mentioned properties of the porous carrier, the activated carbon preferably has physical properties measured according to JIS K1474 (activated carbon testing method) of 0.1 to 5.0% loss on drying, 0.1 to 5.0% ignition residue, 0.25 to 0.85 g / ml packing density, 14.0 to 41.0% acetone adsorption capacity, 600 to 2600 mg / g iodine adsorption capacity, and 90.0 to 100.0% hardness.

[0055] The silica gel used in the present invention includes various silica gels, and preferably contains silicon oxide in an amount of 99% by mass or more, particularly 99.9% by mass or more. The silica gel may be in the form of a molded body. In addition to the above-mentioned properties of the porous carrier, the silica gel preferably has an average particle size of 0.01 to 10 mm as measured by a scanning electron microscope, and preferably has a loss on drying of 10% or less.

[0056] Various zeolites can be used in the present invention, including, for example, LTA zeolite, FER zeolite, MWW zeolite, MFI zeolite, MOR zeolite, LTL zeolite, FAU zeolite, and BEA zeolite. The zeolite may be in the form of a molded body. In addition to the above-described properties of the porous carrier, the zeolite preferably has an average particle size of 0.01 to 15 mm as measured by a scanning electron microscope.

[0057] In the carbon dioxide absorbent of the first embodiment of the present invention, when two or more compounds represented by general formula (1) are supported on the porous carrier, the compounds may be supported in the form of a mixed liquid in which the two or more compounds represented by general formula (1) are mixed, or each of the two or more compounds represented by general formula (1) may be supported on a different part of the porous carrier. That is, for example, when two compounds represented by general formula (1) are supported on the porous carrier, the two compounds represented by general formula (1) may be mixed first, and the resulting mixed liquid may be incorporated into the pores of the porous carrier to support the compound. Alternatively, one of the two compounds represented by general formula (1) may be incorporated into the pores of the porous carrier first, and then the other compound represented by general formula (1) may be incorporated into the pores of the porous carrier to support the compound represented by general formula (1). The same applies when three or more compounds represented by general formula (1) are supported on the porous carrier.

[0058] The impregnation rate (content) of the compound represented by general formula (1) in the carbon dioxide absorbent of the first embodiment of the present invention is not particularly limited, but is preferably 5 to 50 mass %, more preferably 10 to 40 mass %, based on the total mass of the carbon dioxide absorbent. When the impregnation amount of the compound represented by general formula (1) in the carbon dioxide absorbent is within the above range, the compound is uniformly present on the inner surfaces of the pores of the porous support, allowing efficient absorption of carbon dioxide.

[0059] In a first embodiment of the carbon dioxide absorbent of the present invention, a compound supported on a porous carrier is a compound capable of chemically adsorbing carbon dioxide and represented by general formula (1). This allows the carbon dioxide absorbent to more efficiently absorb carbon dioxide when the temperature is −20° C. or higher and 50° C. or lower, and also facilitates desorption of carbon dioxide, making it easy to regenerate the carbon dioxide absorbent.

[0060] The carbon dioxide absorbent of the first embodiment of the present invention is present over the surface of a porous carrier having a large surface area, and therefore can increase the contact area between the compound represented by general formula (1) and carbon dioxide, thereby increasing the carbon dioxide absorption efficiency of the carbon dioxide absorbent of the first embodiment of the present invention.

[0061] The carbon dioxide absorbent of the first embodiment of the present invention is supported on a solid carrier, and therefore can be packed into a column or a reaction tower for use. Furthermore, compared with a liquid carbon dioxide absorbent, the carbon dioxide absorbent of the first embodiment of the present invention forms appropriate gaps when packed into a column or a reaction tower, allowing it to come into contact with carbon dioxide or a carbon dioxide-containing gas more efficiently.

[0062] The carbon dioxide absorbent of the present invention can separate and recover carbon dioxide from a mixed gas containing carbon dioxide. The mixed gas is not particularly limited in terms of other components, so long as it contains carbon dioxide. Examples of other components include oxygen, nitrogen, carbon monoxide, nitric oxide, nitrogen dioxide, dinitrogen monoxide, dinitrogen trioxide, dinitrogen tetroxide, dinitrogen pentoxide, sulfur monoxide, sulfur dioxide, sulfur trioxide, phosphoric acid, sulfuric acid, nitric acid, hydrochloric acid, and water. The concentration of carbon dioxide in the mixed gas is not particularly limited, and may be a high concentration with a purity of approximately 100%, or a concentration similar to that present in the atmosphere.

[0063] The carbon dioxide absorbent of the present invention is useful as an absorbent for separating and recovering carbon dioxide from a mixed gas containing carbon dioxide emitted from, for example, power plants such as coal-fired power plants and natural gas-fired power plants, factories such as chemical plants, waste disposal sites and steelworks, transportation equipment such as automobiles, aircraft and ships, etc. It is also useful as an absorbent used in a DAC (Direct Air Capture) device that separates and recovers carbon dioxide directly from the atmosphere. That is, the carbon dioxide absorbent of the present invention is suitable as a carbon dioxide absorbent for use in various devices such as devices used in power plants, factories, and transportation equipment, and DAC devices.

[0064] Next, a carbon dioxide separation method and a carbon dioxide separation and recovery method using the carbon dioxide absorbent of the present invention will be described.

[0065] The carbon dioxide separation method of the present invention is a carbon dioxide separation method characterized by comprising a carbon dioxide separation step (A) of contacting a mixed gas containing carbon dioxide with the carbon dioxide absorbent of the present invention to cause the carbon dioxide absorbent to absorb the carbon dioxide in the mixed gas, thereby separating carbon dioxide from the mixed gas.

[0066] The carbon dioxide separation and capture method of the present invention is a method for separating and capturing carbon dioxide, characterized by comprising: a carbon dioxide separation step (A) of bringing a mixed gas containing carbon dioxide into contact with the carbon dioxide absorbent of the present invention to cause the carbon dioxide absorbent to absorb the carbon dioxide in the mixed gas, thereby separating carbon dioxide from the mixed gas; and a carbon dioxide capture step (B) of heating the carbon dioxide absorbent that has absorbed carbon dioxide in the carbon dioxide separation step at a temperature of 60°C or higher and 150°C or lower to desorb carbon dioxide from the carbon dioxide absorbent that has absorbed the carbon dioxide, thereby regenerating the carbon dioxide absorbent and capturing the desorbed carbon dioxide.

[0067] In the carbon dioxide separation method of the present invention and the carbon dioxide separation and capture method of the present invention, the step of separating carbon dioxide from a mixed gas containing carbon dioxide is the carbon dioxide separation step (A) in both cases, and they are the same.

[0068] The carbon dioxide separation step (A) is a step of bringing a mixed gas containing carbon dioxide into contact with the carbon dioxide absorbent of the present invention, thereby causing the carbon dioxide absorbent of the present invention to absorb carbon dioxide in the mixed gas.

[0069] The carbon dioxide separation step (A) may, for example, be a step in which a mixed gas containing carbon dioxide is supplied to an absorbent-packed column or absorbent-packed tower packed with the carbon dioxide absorbent of the present invention, and the mixed gas is brought into contact with the carbon dioxide absorbent to allow the carbon dioxide absorbent to absorb the carbon dioxide in the mixed gas, thereby separating carbon dioxide from the mixed gas. In this form of carbon dioxide separation step (A), the mixed gas is supplied to the absorbent-packed column or absorbent-packed tower to bring the mixed gas into contact with the carbon dioxide absorbent, and the mixed gas after contact with the carbon dioxide absorbent in the absorbent-packed column or absorbent-packed tower is discharged from the absorbent-packed column or absorbent-packed tower. The method for packing the absorbent of the present invention into the absorbent-packed column or absorbent-packed tower is not particularly limited, and may be carried out under atmospheric pressure or reduced pressure.

[0070] The temperature of the carbon dioxide absorbent in the carbon dioxide separation step (A) is not limited as long as the carbon dioxide absorbent can exhibit its function, but is preferably −20° C. or higher and 50° C. or lower, preferably 0° C. or higher and 50° C. or lower, and more preferably around room temperature of 25° C., from the viewpoint of more efficient absorption of carbon dioxide.

[0071] The pressure (absolute pressure) in the carbon dioxide separation step (A) is not particularly limited, and the step can be carried out under atmospheric pressure.

[0072] In the carbon dioxide separation step (A), a mixed gas containing carbon dioxide is brought into contact with the carbon dioxide absorbent, whereby the carbon dioxide in the mixed gas is absorbed by the carbon dioxide absorbent of the present invention, and the carbon dioxide can be separated from the mixed gas. In the carbon dioxide separation step (A), a carbon dioxide absorbent having absorbed carbon dioxide is obtained.

[0073] The carbon dioxide separation and capture method of the present invention includes a carbon dioxide capture step (B) of regenerating the carbon dioxide absorbent that has absorbed carbon dioxide in the carbon dioxide separation step and capturing carbon dioxide. The carbon dioxide recovery step (B) is a step of heating the carbon dioxide absorbent that has absorbed carbon dioxide in the carbon dioxide separation step (A) to desorb carbon dioxide from the carbon dioxide absorbent that has absorbed carbon dioxide.

[0074] The carbon dioxide recovery step (B) may, for example, be carried out after the carbon dioxide separation step (A), by heating the carbon dioxide absorbent packed in the absorbent-packed column or absorbent-packed tower to regenerate the carbon dioxide absorbent and recover the desorbed carbon dioxide.

[0075] In the carbon dioxide recovery step (B), the heating temperature of the carbon dioxide absorbent is 60°C or higher and 150°C or lower, preferably 80°C or higher and 140°C or lower. Generally, the higher the heating temperature, the easier it is for carbon dioxide to be desorbed from the carbon dioxide absorbent that has absorbed carbon dioxide. The carbon dioxide absorbent of the present invention can desorb carbon dioxide at a temperature of 60°C or higher and 150°C or lower, preferably 80°C or higher and 140°C or lower, and at a temperature equal to or higher than the temperature in the carbon dioxide separation step (A). For example, when the carbon dioxide absorbent is the carbon dioxide absorbent of the first embodiment of the present invention, the heating temperature is preferably 60°C or higher and 90°C or lower.

[0076] In the carbon dioxide recovery step (B), the pressure (absolute pressure) is not particularly limited, and the step may be performed under atmospheric pressure or under reduced pressure. When the step is performed under reduced pressure, the pressure (absolute pressure) is preferably 190 kPa or less, more preferably 160 kPa or less, from the viewpoint of preventing oxidation of the carbon dioxide absorbent, and further preferably 150 kPa or less, particularly preferably 110 kPa or less, from the viewpoint of efficiently desorbing carbon dioxide from the carbon dioxide absorbent.

[0077] In the carbon dioxide separation and capture method of the present invention, the carbon dioxide separation step (A) and the carbon dioxide capture step (B) can be repeated two or more times by using the regenerated carbon dioxide absorbent obtained by performing the carbon dioxide capture step (B) as the carbon dioxide absorbent with which the mixed gas containing carbon dioxide is contacted in the carbon dioxide separation step (A). For example, when the carbon dioxide separation step (A) and the carbon dioxide capture step (B) are repeated twice, they are performed in the following order: carbon dioxide separation step (A) → carbon dioxide capture step (B) → carbon dioxide separation step (A) → carbon dioxide capture step (B). Then, the carbon dioxide separation step (A) and the carbon dioxide capture step (B) can be repeated as long as the carbon dioxide absorption performance is maintained.

[0078] In the carbon dioxide separation method and carbon dioxide separation and capture method of the present invention, the carbon dioxide absorbent of the present invention containing the compound represented by general formula (1), which has excellent chemical absorption properties, is used for absorbing carbon dioxide, and therefore the efficiency of removing carbon dioxide from a mixed gas can be increased.

[0079] The carbon dioxide separation method and carbon dioxide separation and capture method of the present invention are suitably used when separating or separating and capturing carbon dioxide from a carbon dioxide-containing mixed gas emitted from, for example, power plants such as coal-fired power plants and natural gas-fired power plants, factories such as chemical plants, waste treatment facilities and steelworks, transportation equipment such as automobiles, aircraft and ships, etc. They are also suitably used when separating or separating and capturing carbon dioxide directly from the atmosphere, for example. [Example]

[0080] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0081] (Synthesis Example 1: Tributyl(3-aminopropyl)phosphonium·β-alanine) A glass column (inner diameter 65 mm, length 500 mm) was packed with 1500 ml of ion exchange resin (Amberlite IRA400J Cl, manufactured by Organo Corporation, exchange capacity 1.4 equivalents / resin volume L), and 1000 ml of an aqueous solution containing 80 g (2.0 mol) of sodium hydroxide was passed through it from above using a tube pump at a rate of SV = 1.0, followed by the addition of pure water until the effluent became neutral. Next, 140.0 g (0.41 mol) of tributyl(3-aminopropyl)phosphonium bromide dissolved in 500 mL of purified water was passed through the column at a flow rate of SV = 1.0. 1000 mL of purified water was then passed through the column, yielding 1550 g of an aqueous solution of tributyl(3-aminopropyl)phosphonium hydroxide. Neutralization titration with 1 / 10 N hydrochloric acid titrant revealed a concentration of 6.5% and a yield of 89.0%. 10.7 g (0.12 mol) of β-alanine was dissolved in 500 g (0.12 mol) of the resulting aqueous solution of tributyl(3-aminopropyl)phosphonium hydroxide at room temperature. The resulting mixed solution was concentrated under reduced pressure using an evaporator, and the concentrated solution was mixed with methanol. The resulting methanol solution was dehydrated overnight over anhydrous magnesium sulfate, and the dehydrated methanol solution was concentrated under reduced pressure using an evaporator to obtain 41.4 g (crude yield 99.0%) of a colorless, transparent, viscous liquid with a viscosity (25°C) of 288 cP. The NMR identification data for the resulting colorless, transparent, viscous liquid are as follows: (Identification data) 31 P-NMR: 34.34 ppm 1 H-NMR;0.80ppm(t,9H,-CH3),1.31~1.45ppm(m,12H,-CH2-),1.54~1.59ppm(m,2H,-CH2-)2.03~2.08pp m(m,8H,P-CH2-),2.19ppm(t,2H,-CH2-COO),2.58,2.69ppm(t,2H,-CH2-NH2),3.20,3.21ppm(s,-NH2) As a result, it was confirmed that the compound was tributyl(3-aminopropyl)phosphonium·β-alanine.

[0082] (Synthesis Example 2: Tris(3-aminopropyl)phosphine sulfide) A 1L four-neck flask equipped with a stirrer and thermometer was purged with nitrogen, and 51.3g (0.25mol) of tris(3-aminopropyl)phosphine and 300ml of toluene were charged. A toluene slurry of 8.0g (0.25mol) of sulfur was added in portions while maintaining the temperature at 40-45°C. The mixture was cooled to room temperature and concentrated under reduced pressure using an evaporator to remove the toluene, yielding 59.3g of a transparent orange liquid. The NMR identification data for the resulting transparent orange viscous liquid are as follows: (Identification data) 31 P-NMR(DO); 53.13 ppm 1 H-NMR(D2O); 1.54~1.62ppm(m, 6H, -CH2-), 1.85~1.90ppm(m, 6H, P-CH2-), 2.54~2.63ppm(t, 6H, -CH2-NH2), 4.68ppm(s, 6H, -NH2) As a result, it was confirmed that the compound was tris(3-aminopropyl)phosphine sulfide.

[0083] (Synthesis Example 3: Tris(3-aminopropyl)phorphine selenide) A 1 L four-neck flask equipped with a stirrer and thermometer was purged with nitrogen and charged with 34.9 g (0.17 mol) of tris(3-aminopropyl)phosphine and 300 ml of toluene. A toluene slurry of 13.4 g (0.17 mol) of selenium powder was added in portions at room temperature over 10 minutes. The liquid temperature rose from 22 °C to 35 °C, and with stirring, the temperature rose to 50 °C. The black color gradually faded, forming a two-layer structure with toluene, yielding a colorless, transparent product in the lower layer. The mixture was then aged at 60 °C for an additional hour. After cooling to room temperature, the toluene was removed using an evaporator, yielding 48.3 g of a colorless, transparent liquid (crude yield 99.3%). The NMR identification data for the resulting colorless, transparent, viscous liquid are as follows: (Identification data) 31 P-NMR (CD3OD); 39.24 ppm 1H-NMR (CD3OD); 1.72~1.74ppm (m, 6H, -CH2-), 1.98~2.10ppm (m, 6H, P-CH2-), 2.70~2.73ppm (t, 6H, -CH2-NH2), 4.67ppm (s, 6H, -NH2) As a result, it was confirmed to be tris(3-aminopropyl)phosphine selenide.

[0084] Example 1 35.6 g (0.15 mol) of tris(3-aminopropyl)phosphine sulfide obtained in Synthesis Example 2 was dissolved in 300 ml of pure water, and silica gel (CARiACT Q-30 manufactured by Fuji Silysia Chemical Ltd., particle size 1.70 to 4.00 mm, BET specific surface area 100 m 2 66.1 g of silica gel (3-aminopropyl)phosphine sulfide (30 nm / g, average pore diameter) was added and left to stand at room temperature until the silica gel became moisture permeable. The added water was completely distilled off by concentrating under reduced pressure using an evaporator, yielding 102.8 g of a carbon dioxide absorbent in which tris(3-aminopropyl)phosphine sulfide was impregnated into silica gel. The impregnation rate was 35.0 mass %. The obtained carbon dioxide absorbent was evaluated in Carbon Dioxide Absorption Test 1 and Carbon Dioxide Absorption Test 2, which will be described later.

[0085] Example 2 34.0 g (0.166 mol) of tris(3-aminopropyl)phosphine selenide obtained in Synthesis Example 3 was dissolved in 300 ml of pure water, and silica gel (CARiACT Q-30 manufactured by Fuji Silysia Chemical Ltd., particle size 1.70 to 4.00 mm, BET specific surface area 100 m 2 63.1 g of silica gel (3-aminopropyl) selenide (3.1 g / g, average pore diameter 30 nm) was added and left to stand at room temperature until the silica gel became moisture permeable. The added water was completely distilled off by concentrating under reduced pressure using an evaporator, thereby obtaining 97.3 g of a carbon dioxide absorbent in which tris(3-aminopropyl)phosphine selenide was impregnated onto silica gel. The impregnation rate was 35.0 mass %. The obtained carbon dioxide absorbent was evaluated in Carbon Dioxide Absorption Test 1 and Carbon Dioxide Absorption Test 2 described below.

[0086] (Reference example 1) 30.2 g (0.086 mol) of tributyl(3-aminopropyl)phosphonium β-alanine obtained in Synthesis Example 1 was dissolved in 300 ml of pure water and then added to silica gel (Fuji Silysia Chemical Ltd., CAriACT Q-30, particle size 1.70 to 4.00 mm, BET specific surface area 100 m 2 55.9 g of silica gel (30 nm / g, average pore size) was added and left to stand at room temperature until the silica gel became moisture permeable. The added water was completely removed by vacuum concentration using an evaporator, yielding 86.3 g of a carbon dioxide absorbent in which tributyl(3-aminopropyl)phosphonium β-alanine was impregnated onto the silica gel. The impregnation rate was 35.0 mass %. The obtained carbon dioxide absorbent was evaluated in Carbon Dioxide Absorption Test 1 and Carbon Dioxide Absorption Test 2, which will be described later.

[0087] (evaluation) (Carbon dioxide absorption test 1) 90 ml of the carbon dioxide absorbents obtained in Examples 1, 2, and Reference Example 1 were packed into a glass column with an inner diameter of 20 mm and a length of 300 mm, and atmospheric air (room temperature 25°C, average carbon dioxide concentration: 450 ppm) was passed through the column at a flow rate of 100 ml / min using an air pump. The carbon dioxide concentration at the outlet of the glass column was measured and recorded using a data logger carbon dioxide measuring device (TR-76Ui-S, manufactured by T&D Corporation), and the time until saturation was reached and the carbon dioxide concentration began to increase (breakthrough time) was determined. The number of moles of absorbed carbon dioxide was calculated by taking the difference between the average carbon dioxide concentration in the room and the average carbon dioxide concentration at the outlet as the amount of carbon dioxide absorbed. The absorption capacity was determined as the amount of carbon dioxide absorbed per gram of carbon dioxide absorbent. The results are shown in Table 1.

[0088] [Table 1]

[0089] The results shown in Table 1 show that the carbon dioxide absorbents of Examples 1 and 2 are superior to the carbon dioxide absorbent of Reference Example 1 in terms of carbon dioxide absorption performance.

[0090] (Carbon dioxide absorption test 2) The carbon dioxide absorbents obtained in Examples 1, 2, and Reference Example 1 were placed in 35-ml Erlenmeyer flasks, weighed accurately to the nearest 0.1 mg, and 99.995% pure carbon dioxide gas was blown into the flask at a flow rate of 200 mL / min at room temperature (25°C). The weight was measured accurately to the nearest 0.1 mg every 10 minutes, and gas blowing was terminated when the weight reached equilibrium. The increased weight was used as the amount of carbon dioxide absorbed, and the number of moles was calculated. The absorption capacity was calculated as the amount of carbon dioxide absorbed per gram of carbon dioxide absorbent. The results are shown in Table 2.

[0091] [Table 2]

[0092] The results shown in Table 2 show that the carbon dioxide absorbents of Examples 1 and 2 are superior to the carbon dioxide absorbent of Reference Example 1 in terms of carbon dioxide absorption performance.

[0093] (Regeneration test) The carbon dioxide absorbent obtained in Example 1 was placed in a 35 ml Erlenmeyer flask, weighed accurately to the nearest 0.1 mg, and 99.995% pure carbon dioxide gas was blown into it at a flow rate of 200 ml / min at room temperature (25°C). The weight was measured accurately to the nearest 0.1 mg every 10 minutes, and gas blowing was stopped when the weight reached equilibrium. The increased weight was taken as the amount of carbon dioxide absorbed, and the number of moles was calculated. The absorption capacity was determined as the amount of carbon dioxide absorbed per gram of carbon dioxide absorbent. The carbon dioxide absorbent of Example 1 that had absorbed carbon dioxide to saturation was transferred to a Petri dish with a diameter of 50 mmφ, and was left to stand and heat in a vacuum dryer maintained at 80°C and fully evacuated with a vacuum pump, to desorb carbon dioxide for 1 hour, thereby carrying out regeneration. The carbon dioxide absorbent was then regenerated by desorbing carbon dioxide, and the regeneration was repeated five times in a 35 ml Erlenmeyer flask. The regeneration rate was calculated using the following formula. The results are shown in Table 3. Regeneration rate (%) = (absorption capacity at regeneration / initial absorption capacity) x 100

[0094] [Table 3]

[0095] The results shown in Table 3 show that the carbon dioxide absorbent that had absorbed carbon dioxide to saturation was heated and the carbon dioxide was desorbed to form a regenerated carbon dioxide absorbent, which restored its ability to absorb carbon dioxide and showed excellent absorption performance and regeneration rate, even though it was a regenerated carbon dioxide absorbent.

Claims

1. The following general formula (1): 【Chemistry 1】 (wherein a, b, and c represent integers of 1 or more and 10 or less, X is selected from S and Se, and R １ , R ２ and R ３ each independently represents a hydroxy group, a primary amino group, a secondary amino group, or a tertiary amino group; R １ , R ２ and R ３ At least one of is a primary amino group, a secondary amino group, or a tertiary amino group. A compound represented by the formula:

2. In the general formula (1), R １ , R ２ and R ３ and each of the following is a primary amino group:

3. In the general formula (1), R １ , R ２ and R ３ and each of the groups is a secondary amino group substituted with an alkyl group having 1 to 10 carbon atoms.

4. The following general formula (1): 【Chemistry 1】 (wherein a, b, and c represent integers of 1 or more and 10 or less, X is selected from S and Se, and R １ , R ２ and R ３ each independently represents a hydroxy group, a primary amino group, a secondary amino group, or a tertiary amino group; R １ , R ２ and R ３ At least one of is a primary amino group, a secondary amino group, or a tertiary amino group. A compound for use as a carbon dioxide absorbent, characterized in that it is a compound represented by the formula:

5. A carbon dioxide absorbent comprising the compound for carbon dioxide absorbents according to claim 4.

6. 6. The carbon dioxide absorbent according to claim 5, comprising a porous carrier and the compound for a carbon dioxide absorbent according to claim 4 supported on the porous carrier.

7. 7. The carbon dioxide absorbent according to claim 6, wherein the porous carrier is activated carbon, silica gel, layered silicate, mesoporous silica, zeolite, vermiculite, molecular sieve, porous silica, diatomaceous earth, porous resin, porous fiber, porous metal-organic framework, porous alumina, porous ceramic, porous concrete, activated clay, or clay mineral.

8. A carbon dioxide separation method comprising: a carbon dioxide separation step of contacting a mixed gas containing carbon dioxide with the carbon dioxide absorbent according to claim 6 to cause the carbon dioxide absorbent to absorb the carbon dioxide in the mixed gas, thereby separating carbon dioxide from the mixed gas.

9. a carbon dioxide separation step of contacting a mixed gas containing carbon dioxide with the carbon dioxide absorbent according to claim 6 to cause the carbon dioxide absorbent to absorb the carbon dioxide in the mixed gas, thereby separating carbon dioxide from the mixed gas; a carbon dioxide recovery step of heating the carbon dioxide absorbent that has absorbed carbon dioxide in the carbon dioxide separation step at a temperature of 60°C or higher and 150°C or lower to desorb carbon dioxide from the carbon dioxide absorbent that has absorbed carbon dioxide, thereby regenerating the carbon dioxide absorbent and recovering the desorbed carbon dioxide; A carbon dioxide separation and capture method comprising the steps of:

10. 10. The method for separating and capturing carbon dioxide according to claim 9, wherein the carbon dioxide separation step and the carbon dioxide capture step are repeated two or more times by using a regenerated carbon dioxide absorbent obtained by performing the carbon dioxide capture step as the carbon dioxide absorbent with which the mixed gas containing carbon dioxide is brought into contact in the carbon dioxide separation step.

11. An apparatus characterized in that the carbon dioxide absorbent according to claim 5 is used.

12. 12. The apparatus of claim 11, wherein the apparatus is used in a power plant, a factory, or a transportation facility.

13. 12. The device of claim 11, wherein the device is a DAC device.

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