Carbon dioxide absorbent, carbon dioxide separation method, carbon dioxide separation and recovery method, and apparatus using carbon dioxide absorbent

Abstract

To provide a novel trialkylphosphine oxide having an alkyl group to which an amino group is bonded.SOLUTION: The phosphine oxide compound is represented by the general formula (1) in the figure. (In the formula, a, b and c each represent an integer of 1 or more and 10 or less, and R1, R2 and R3 each independently represent a primary amino group, a secondary amino group, or a tertiary amino group, where at least one of R1, R2 and R3 is a secondary amino group or a tertiary amino group.)SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a phosphine oxide 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 oxides having an alkyl group to which a primary amino group is bonded are used, for example, as curing agents for epoxy resins. Patent Document 2 discloses a curing agent for epoxy resins containing an aminoalkylphosphine oxide as an active ingredient.

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

[0009] When trialkylphosphine oxides having an alkyl group bonded to a primary amino group are applied to various applications, specific effects derived from the amino group can be expected, but on the other hand, problems due to the amino group are expected to arise depending on the application. Therefore, the development of new trialkylphosphine oxides suited to the application is desired along with the development of applications of trialkylphosphine oxides.

[0010] In addition, some applications of trialkylphosphine oxides require oxidation stability. In general, amino groups (-NH2) are easily oxidized, so it is assumed that such applications require trialkylphosphine oxides with improved oxidation resistance.

[0011] 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 trialkylphosphine oxide 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 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]

[0012] The present inventors have conducted extensive research in light of the above-mentioned circumstances, and as a result have found that by using an alkyl group of a trialkylphosphine oxide to which a secondary amino group or a tertiary amino group is bonded, that is, a phosphine oxide compound represented by the following general formula (1), (1) exhibits better carbon dioxide absorption performance than conventional compounds, (2) improves the ability to desorb carbon dioxide after carbon dioxide absorption, and (3) has excellent heat resistance, and have completed the present invention.

[0013] [ka]

[0014] (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 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 secondary amino group or a tertiary amino group.

[0015] That is, the present invention (1) relates to a compound represented by the following general formula (1):

[0016] [ka]

[0017] (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 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 secondary amino group or a tertiary amino group. The present invention provides a phosphine oxide compound represented by the following formula:

[0018] The present invention (2) also provides a compound for use as a carbon dioxide absorbent, which is the phosphine oxide compound of the present invention (1).

[0019] 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).

[0020] 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.

[0021] 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 30°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.

[0022] The present invention (6) also provides an apparatus characterized by using the carbon dioxide absorbent of the present invention (3). [Effects of the Invention]

[0023] According to the present invention, a novel trialkylphosphine oxide can be provided which has an alkyl group to which an amino group is bonded. Furthermore, according to the present invention, it is possible to provide a novel trialkylphosphine oxide having an alkyl group in which an amino group is bonded to the alkyl group, and having excellent oxidation resistance. 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 compound for a carbon dioxide absorbent and a carbon dioxide absorbent that have excellent oxidation resistance in addition to the above-mentioned carbon dioxide absorption performance and therefore excellent durability against repeated absorption and regeneration. 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

[0024] The present invention will be described below based on preferred embodiments. The phosphine oxide compound of the present invention is represented by the following general formula (1):

[0025] [ka]

[0026] (In the formula, a, b, and c represent integers of 1 or more and 10 or less, and R 1 , R 2and R 3 each independently represents 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 secondary amino group or a tertiary amino group. It is a phosphine oxide compound represented by the formula:

[0027] The phosphine oxide compound represented by general formula (1) has three alkyl groups bonded to an amino group at P in the phosphine oxide structure (P=O), and at least one of the three alkyl groups bonded to an amino group is an alkyl group bonded to a secondary amino group or a tertiary amino group. The alkyl group bonded to a secondary amino group or a tertiary amino group has better oxidation resistance than the alkyl group bonded to a primary amino group. Furthermore, when the phosphine oxide compound represented by general formula (1) is used for absorbing carbon dioxide, an alkyl group having a secondary amino group or a tertiary amino group bonded thereto is superior in desorbing absorbed carbon dioxide compared to an alkyl group having a primary amino group bonded thereto, and is capable of desorbing carbon dioxide at low temperatures. Furthermore, the phosphine oxide compound represented by general formula (1) has a phosphine oxide structure (P=O), and therefore has high heat resistance. When used as a carbon dioxide absorbent, the phosphine oxide compound has a low vapor pressure and almost no volatility in the heating temperature range during regeneration after carbon dioxide absorption, for example, in the heating temperature range of 30°C to 150°C.

[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 3each independently represents 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 secondary amino group or a tertiary amino group. 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 R may be primary amino groups, but the phosphine oxide 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. 1 , R 2 and R 3 may be the same or different, but are preferably the same from the viewpoint of ease of synthesis.

[0030] R 1 , R 2 and R 3The 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 whose substituent is an alkyl group having from 1 to 10 carbon atoms or an alkyl group having from 1 to 10 carbon atoms and a hydroxyl group, and more preferably an amino group whose substituent is an alkyl group having from 1 to 4 carbon atoms or an alkyl group having from 1 to 4 carbon atoms and a hydroxyl group. The alkyl group includes a linear alkyl group, a branched alkyl group, and a cyclic alkyl group.

[0031] 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.

[0032] 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.

[0033] When the phosphine oxide compound of the present invention is used as a carbon dioxide absorbent, it can exhibit excellent carbon dioxide absorption performance, and further, even when the absorbed carbon dioxide is desorbed to regenerate the absorbent, the carbon dioxide absorption ability is restored, and a regenerated carbon dioxide absorbent having excellent carbon dioxide absorption performance is obtained. 1 , R 2 and R 3 is preferably an amino group substituted with a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an ethanol group, an n-propanol group, or an isopropanol group, and particularly preferably an amino group substituted with a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an ethanol group, or an isopropanol group.

[0034] Examples of the phosphine oxide compound represented by general formula (1) include tris(3-(N-ethylaminopropyl))phosphine oxide, tris(3-(N-methylaminopropyl))phosphine oxide, tris(3-(N-(n-propyl)aminopropyl))phosphine oxide, tris(3-(N-isopropylaminopropyl))phosphine oxide, tris(3-(N-ethanolaminopropyl))phosphine oxide, tris(3-(N-(n-propanol)aminopropyl))phosphine oxide, Examples of such phosphine oxides include bis(3-(N-ethylaminopropyl))phosphine oxide, tris(3-(N-isopropanolaminopropyl))phosphine oxide, bis(3-(N-ethylaminopropyl))(3-aminopropyl)phosphine oxide, bis(3-(N-methylaminopropyl))(3-aminopropyl)phosphine oxide, and bis(3-aminopropyl)(3-(N-methylaminopropyl))phosphine oxide.

[0035] The compound for a carbon dioxide absorbent of the present invention has the following general formula (1):

[0036] [ka]

[0037] (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 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 secondary amino group or a tertiary amino group. The compound for use as a carbon dioxide absorbent is a phosphine oxide compound represented by the formula:

[0038] 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 phosphine oxide compound represented by general formula (1) with carbon dioxide. In other words, the phosphine oxide 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 phosphine oxide compound represented by general formula (1) related to the compound for a carbon dioxide absorbent of the present invention is the same as the phosphine oxide compound represented by general formula (1) related to the phosphine oxide compound of the present invention, except as described below.

[0039] 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 phosphine oxide compound represented by general formula (1). In the carbon dioxide absorbent of the present invention, the phosphine oxide represented by general formula (1) absorbs carbon dioxide. The phosphine oxide compound represented by general formula (1) related to the carbon dioxide absorbent of the present invention is the same as the phosphine oxide compound represented by general formula (1) related to the phosphine oxide compound of the present invention.

[0040] The phosphine oxide compound represented by general formula (1) used in the carbon dioxide absorbent of the present invention includes tris(3-(N-ethylaminopropyl))phosphine oxide, tris(3-(N-methylaminopropyl))phosphine oxide, tris(3-(N-(n-propyl)aminopropyl))phosphine oxide, tris(3-(N-isopropylaminopropyl))phosphine oxide, tris(3-(N-ethanolaminopropyl))phosphine oxide, tris(3-(N-(n-propanopropyl))phosphine oxide, Examples of suitable phosphine oxides include bis(3-(N-isopropanolaminopropyl))phosphine oxide, tris(3-(N-isopropanolaminopropyl))phosphine oxide, bis(3-(N-ethylaminopropyl))(3-aminopropyl)phosphine oxide, bis(3-aminopropyl)(3-(N-ethylaminopropyl))phosphine oxide, bis(3-(N-methylaminopropyl))(3-aminopropyl)phosphine oxide, and bis(3-aminopropyl)(3-(N-methylaminopropyl))phosphine oxide.

[0041] The phosphine oxide compound represented by the general formula (1) used in the carbon dioxide absorbent of the present invention is 1 , R 2 and R 3 Among the phosphine oxide compounds represented by general formula (1), those in which R is a secondary amino group are preferred in that they have excellent oxidation resistance, and therefore excellent durability against repeated absorption and desorption of carbon dioxide, and excellent desorption ability of absorbed carbon dioxide. 1 , R 2 and R 3 Examples of compounds in which all of the above are secondary amino groups include tris(3-(N-ethylaminopropyl))phosphine oxide, tris(3-(N-methylaminopropyl))phosphine oxide, tris(3-(N-(n-propyl)aminopropyl))phosphine oxide, tris(3-(N-isopropylaminopropyl))phosphine oxide, tris(3-(N-ethanolaminopropyl))phosphine oxide, tris(3-(N-(n-propanol)aminopropyl))phosphine oxide, and tris(3-(N-isopropanolaminopropyl))phosphine oxide.

[0042] 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 phosphine oxide compounds represented by general formula (1). For example, the carbon dioxide absorbent of the present invention can contain two or more phosphine oxide compounds represented by general formula (1) that are R 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 two of which are secondary amino groups and one of which is a primary amino group, and a phosphine oxide compound 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 primary 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 primary amino groups; 1 , R 2 and R 3a mixture in which one or all of a, b and c are different from the others, or 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 phosphine oxide compounds represented by general formula (1) include tris(3-(N-ethylaminopropyl))phosphine oxide, tris(3-(N-methylaminopropyl))phosphine oxide, tris(3-(N-(n-propyl)aminopropyl))phosphine oxide, tris(3-(N-isopropylaminopropyl))phosphine oxide, tris(3-(N-ethanolaminopropyl))phosphine oxide, tris(3-(N-(n-propanol)aminopropyl))phosphine oxide, and mixtures of two or more selected from the group consisting of sphingosine oxide, tris(3-(N-isopropanolaminopropyl))phosphine oxide, bis(3-(N-ethylaminopropyl))(3-aminopropyl)phosphine oxide, bis(3-aminopropyl)(3-(N-ethylaminopropyl))phosphine oxide, bis(3-(N-methylaminopropyl))(3-aminopropyl)phosphine oxide, and bis(3-aminopropyl)(3-(N-methylaminopropyl))phosphine oxide.

[0043] The proportion of primary amino groups in all amino groups of all phosphine oxide compounds represented by general formula (1) used in the carbon dioxide absorbent of the present invention is preferably 50 mol % or less, more preferably 30 mol % or less, and particularly preferably 0.0 mol %, in terms of excellent oxidation resistance. In the present invention, the proportion of primary amino groups in all amino groups of all phosphine oxide compounds represented by general formula (1) is 1 Determined by H-NMR.

[0044] In the carbon dioxide absorbent of the present invention, the form of the phosphine oxide 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.

[0045] The carbon dioxide absorbent of the present invention is 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 present invention is characterized by comprising a porous carrier and a phosphine oxide compound represented by general formula (1) supported on the porous carrier. In the carbon dioxide absorbent of the present invention, the phosphine oxide 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 phosphine oxide compound represented by general formula (1) is supported on the porous carrier.

[0046] The porous carrier for the carbon dioxide absorbent of the present invention is not particularly limited as long as it has a porous structure having a large number of internal pores, and can incorporate a phosphine oxide compound represented by general formula (1) into the internal pores and physically adsorb and retain the phosphine oxide compound represented by general formula (1) within the pores. Examples of the porous carrier 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, clay mineral, and composites thereof. In terms of being able to increase the amount of the phosphine oxide compound represented by general formula (1) supported, activated carbon, silica gel, mesoporous silica, zeolite, molecular sieve, a composite of alumina and silica gel, and a composite of alumina and mesoporous silica are preferred. Furthermore, when the porous support is a porous body capable of retaining water within its pores, such as activated carbon, silica gel, mesoporous silica, zeolite, molecular sieve, a composite of alumina and silica gel, or a composite of alumina and mesoporous silica, when the carbon dioxide-containing gas to be treated 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 carbon dioxide absorbent compound from eluting from the porous support, and thus improving the carbon dioxide absorption performance of the carbon dioxide absorbent. The porous body capable of retaining water within its pores is not particularly limited 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.

[0047] 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.

[0048] Examples of the shape of the porous carrier include granular, powdery, fibrous, plate-like, cylindrical, honeycomb, dice-like, and rectangular parallelepiped shapes. Among these, granular or powdery shapes are preferred from the viewpoints 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.

[0049] Among the porous supports, activated carbon, silica gel, mesoporous silica, zeolite, molecular sieve, alumina-silica gel composite, and alumina-mesoporous silica composite are preferred from the viewpoints of ease of handling and ability to easily support the liquid phosphine oxide compound represented by general formula (1), and activated carbon and silica gel are particularly preferred.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] In the carbon dioxide absorbent of the present invention, when two or more phosphine oxide compounds represented by the general formula (1) are supported on the porous carrier, the two or more phosphine oxide compounds may be supported in the form of a mixed liquid in which the two or more phosphine oxide compounds represented by the general formula (1) are mixed, or each of the two or more phosphine oxide compounds represented by the general formula (1) may be supported on a different part of the porous carrier. That is, for example, when two phosphine oxide compounds represented by the general formula (1) are supported on the porous carrier, the two phosphine oxide compounds represented by the 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 two phosphine oxide compounds represented by the general formula (1). Alternatively, one of the two phosphine oxide compounds represented by the general formula (1) may be incorporated into the pores of the porous carrier first, and then the other phosphine oxide compound represented by the general formula (1) may be incorporated into the pores of the porous carrier to support the two phosphine oxide compounds represented by the general formula (1). The same applies to the case where three or more phosphine oxide compounds represented by the general formula (1) are supported on a porous carrier.

[0054] The impregnation rate (content) of the phosphine oxide compound represented by general formula (1) in the carbon dioxide absorbent of the present invention is not particularly limited, but is preferably 5 to 50 mass %, more preferably 20 to 40 mass %, based on the total mass of the carbon dioxide absorbent. When the impregnation amount of the phosphine oxide compound represented by general formula (1) in the carbon dioxide absorbent is within the above range, the phosphine oxide compound is uniformly present on the inner surfaces of the pores of the porous support, thereby enabling efficient absorption of carbon dioxide.

[0055] The carbon dioxide absorbent of the present invention is supported on a porous carrier and is a phosphine oxide compound capable of chemically adsorbing carbon dioxide and represented by general formula (1). This enables 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.

[0056] The carbon dioxide absorbent of the present invention is present over the surface of a porous carrier having a large surface area, and therefore the contact area between the phosphine oxide compound represented by general formula (1) and carbon dioxide can be increased, thereby increasing the carbon dioxide absorption efficiency of the carbon dioxide absorbent of the present invention.

[0057] The carbon dioxide absorbent of the present invention is in a form supported on a solid carrier, and therefore can be packed into a column or a reaction tower for use. When packed into a column or a reaction tower, the carbon dioxide absorbent of the present invention forms appropriate gaps, compared with a liquid carbon dioxide absorbent, and can therefore come into contact with carbon dioxide or a carbon dioxide-containing gas more efficiently.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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 30°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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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 −10° C. or higher and 30° C. or lower, and more preferably around room temperature of 25° C., from the viewpoint of more efficient absorption of carbon dioxide.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] In the carbon dioxide recovery step (B), the heating temperature of the carbon dioxide absorbent is 30°C or higher and 150°C or lower, preferably 30°C or higher and 120°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 30°C or higher and 150°C or lower, preferably 30°C or higher and 120°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 present invention, carbon dioxide can be desorbed even at a heating temperature of 30°C or higher and 80°C or lower, preferably 30°C or higher and 70°C or lower, more preferably 30°C or higher and 60°C or lower. Therefore, the required thermal energy can be reduced. In addition, exhaust heat from factories such as chemical plants, waste treatment facilities, and steel mills can be utilized.

[0072] In the carbon dioxide recovery step (B), the pressure (absolute pressure) is not particularly limited, and the step may be carried out in air (atmospheric pressure) or under reduced pressure. By carrying out the step in air (atmospheric pressure), a degassing device is not required. When the step is carried out under reduced pressure, the pressure (absolute pressure) is preferably 150 kPa or less, more preferably 110 kPa or less, from the viewpoint of more easily preventing oxidation of the carbon dioxide absorbent, and further preferably 50 kPa or less, particularly preferably 30 kPa or less, from the viewpoint of efficiently desorbing carbon dioxide from the carbon dioxide absorbent.

[0073] 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.

[0074] In the carbon dioxide separation and capture method of the present invention, by using a carbon dioxide absorbent in a form in which the carbon dioxide absorbent compound of the present invention is supported on a porous carrier, the carbon dioxide capture step (B) can be carried out in air (under atmospheric pressure) at a heating temperature of 30°C or higher and 80°C or lower, preferably 30°C or higher and 70°C or lower, and more preferably 30°C or higher and 60°C or lower. This is therefore very useful in that it can reduce the energy costs required for carbon dioxide capture. In addition, because carbon dioxide can be desorbed in air, a degassing device is not required, and because carbon dioxide can be desorbed at relatively low temperatures, it is possible to utilize waste heat from factories such as chemical plants, waste treatment facilities, and steel mills.

[0075] 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 phosphine oxide 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.

[0076] 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]

[0077] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0078] (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-),2.03~2.08p pm(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.

[0079] (Synthesis Example 2: Tris(3-aminopropyl)phosphine oxide) A 1 L stainless steel autoclave equipped with a stirrer, thermometer, pressure pump, safety valve, and gas inlet tube was charged with 150 ml of toluene and 133 g (2.33 mol) of allylamine, and the autoclave was purged with nitrogen gas and vacuum three times. 22 g (0.65 mol) of 99.9% pure phosphine gas manufactured by Nippon Chemical Industry Co., Ltd. was then charged. When the temperature was raised to 80°C in a hot water bath, the gauge pressure was 0.93 MPa (absolute pressure 1.03 MPa). Next, 1.06 g (0.006 mol) of azobisisobutyronitrile was dissolved in 150 ml of toluene, injected in portions over 6 hours, and aged overnight at 80 °C. At this time, the gauge pressure was 0.01 MPa (absolute pressure 0.11 MPa). After aging overnight, the mixture was cooled to room temperature, and the remaining gas was vented to an exhaust system. The system was then purged with nitrogen gas and vacuum. The mixture was then extracted into a reduced-pressure eggplant-shaped flask, yielding 585 g of a colorless, transparent liquid. Next, the obtained colorless transparent liquid was heated under reduced pressure (gauge pressure 4 kPa (absolute pressure 105.3 kPa), 80°C) to distill off excess allylamine and toluene, and the degree of vacuum and temperature were further increased to heat (gauge pressure 0.2 kPa (absolute pressure 101.5 kPa), 160°C). When the initial distillate began to appear, heating was stopped and the residue was used as the product. The resulting product was cooled to room temperature and then purged with nitrogen gas to yield 120 g of a colorless, transparent liquid. The NMR identification data for the resulting colorless, transparent liquid are as follows: (Identification data) 31 P-NMR(DO); -29.73 ppm 1 H-NMR(D2O); 1.40~1.46ppm(m, 6H, -CH2-), 1.52~1.61ppm(m, 6H, P-CH2-), 2.63~2.71ppm(m, 6H, -CH2-NH2), 4.67ppm(s, 6H, -NH2) As a result, it was confirmed that the compound was tris(3-aminopropyl)phosphine. Next, a 1L four-neck flask equipped with a stirrer and thermometer was purged with nitrogen gas, and 92.4g (0.45 mol) of the obtained tris(3-aminopropyl)phosphine and 500ml of pure water were charged. 56.1g (0.495 mol) of 30% hydrogen peroxide diluted with 100ml of pure water was added dropwise over 1 hour while maintaining the temperature at 70-75°C. After the dropwise addition, the mixture was aged for 1 hour, cooled to room temperature, and concentrated under reduced pressure in an evaporator to remove water, yielding 100.8g of a colorless, transparent liquid. The NMR identification data of the obtained colorless, transparent liquid is as follows: (Identification data) 31 P-NMR(DO); 60.77 ppm 1 H-NMR(D2O); 1.50~1.58ppm(m, 6H, -CH2-), 1.71~1.77ppm(m, 6H, P-CH2-), 2.57~2.60ppm(t, 6H, -CH2-NH2), 4.70ppm(s, 6H, -NH2) As a result, it was confirmed that the compound was tris(3-aminopropyl)phosphine oxide.

[0080] (Example 1) Synthesis of tris(3-(N-ethylaminopropyl))phosphine oxide A 1 L four-neck flask equipped with a stirrer, thermometer, and dropping funnel was charged with 44.3 g (0.2 mol) of tris(3-aminopropyl)phosphine oxide obtained in Synthesis Example 2 and 200 ml of purified water, and heated to 60-65°C. Furthermore, 98.1 g (0.9 mol) of ethyl bromide was gradually added dropwise, taking care not to cause excessive reflux. After the addition, the mixture was aged for 1 hour, cooled to room temperature, and pH was confirmed to be neutral using pH test paper. Water was removed by vacuum concentration using an evaporator, yielding 108.0 g of a pale yellow, transparent liquid (crude yield 98.5%). The NMR identification data for the resulting pale yellow, transparent liquid are as follows: (Identification data) 31 P-NMR(DO); 57.06 ppm 1 H-NMR(D2O); 1.12~1.14ppm(t, 9H, -CH3), 1.75~1.85ppm(m, 6H, -CH2-), 1.85~1.93ppm(m, 6H, P-CH2-), 2.94~3.12ppm(m, 12H, -CH2-N + H2-CH2-), 4.65ppm(s, 6H, -N + H2-) As a result, it was confirmed that the compound was tris(3-(N-ethylaminopropyl))phosphine oxide trihydrobromide. Next, 82.2 g (0.15 mol) of tris(3-(N-ethylaminopropyl))phosphine oxide trihydrobromide and 200 ml of ethanol were placed in a 1 L four-neck flask equipped with a stirrer and thermometer, and 153.1 g (0.45 mol) of sodium ethylate (20% ethanol solution) was added at room temperature and stirred. A white precipitate gradually formed, causing the mixture to become cloudy. After stirring for 1 hour, the mixture was filtered through a Buchner funnel lined with an ethanol slurry of Celite (Hyflo Super Cel, Fujifilm Wako Pure Chemical Industries, Ltd.). The ethanol was concentrated using an evaporator to obtain 43.5 g of a pale yellow liquid (crude yield 95.0%). The NMR identification data for the resulting pale yellow, transparent liquid are as follows: (Identification data) 31 P-NMR(DO); 60.61 ppm 1 H-NMR(D2O); 0.89~0.93ppm(m, 9H, -CH3), 1.50~1.60ppm(m, 6H, -CH2-), 1.65~1.6 8ppm(m, 6H, P-CH2-), 2.40~2.58ppm(m, 12H, -CH2-NH-CH2-), 4.68ppm(s, 6H, -NH-) As a result, it was confirmed that the compound was tris(3-(N-ethylaminopropyl))phosphine oxide.

[0081] (Example 2) Synthesis of a mixture containing tris(3-(N-ethylaminopropyl))phosphine oxide as the main component A 1 L four-neck flask equipped with a stirrer, thermometer, and dropping funnel was charged with 44.3 g (0.2 mol) of tris(3-aminopropyl)phosphine oxide obtained in Synthesis Example 2 and 200 ml of ethanol, and heated to 60-65°C. Next, 98.1 g (0.9 mol) of ethyl bromide was gradually added dropwise, taking care not to cause vigorous reflux. After the addition, the mixture was aged for 1 hour, cooled to room temperature, and pH was confirmed to be weakly basic using pH test paper. The ethanol was removed by vacuum concentration using an evaporator, yielding 97.6 g (crude yield 89.0%) of tris(3-(N-ethylaminopropyl))phosphine oxide trihydrobromide as a pale yellow, transparent liquid. Next, 1500 ml of ion exchange resin (Amberlite IRA400J Cl, manufactured by Organo Corporation, exchange capacity 1.4 equivalents / resin volume L) was packed into a glass column (inner diameter 65 mmφ × length 500 mm), and 1000 ml of an aqueous solution containing 80 g (2.0 mol) of sodium hydroxide was passed through the column from above using a tube pump at a rate of SV = 1.0, followed by the passage of pure water until the effluent became neutral. 54.8 g (0.1 mol) of the obtained tris(3-(N-ethylaminopropyl))phosphine oxide trihydrobromide was dissolved in 500 ml of purified water and passed through the column from the top at a flow rate of SV=1.0. 1000 ml of purified water was then passed through to obtain 1450 ml of basic aqueous solution. The water was removed by concentration using an evaporator to obtain 28.7 g of a pale yellow liquid (crude yield 94.0%). The NMR identification data for the obtained pale yellow liquid are as follows: (Identification data) 31 P-NMR (CD3OD); 55.34 ppm 1 H-NMR(CD3OD); 1.03~1.10ppm(m, 6.3H, -CH3), 1.65~1.84ppm(m, 12H, P-CH2-CH2-), 2.52~2.73ppm(m, 10.2H, -CH2-NH-CH2-), 4.76ppm(s, 5.7H, -NH-) As a result, it was found that the mixture contained tris(3-(N-ethylaminopropyl))phosphine oxide as the main component, and further 1 The results of H-NMR analysis confirmed that 70% of all amino groups in the mixture were N-ethylated, with the remaining 30% remaining as amino groups.

[0082] (Example 3) Synthesis of tris(3-(N-methylaminopropyl))phosphine oxide A 1 L four-neck flask equipped with a stirrer, thermometer, and dropping funnel was charged with 44.3 g (0.2 mol) of tris(3-aminopropyl)phosphine oxide obtained in Synthesis Example 2 and 200 ml of methanol. 85.2 g (0.6 mol) of methyl iodide was slowly added dropwise at room temperature, causing the liquid temperature to rise to 36.1°C. After the addition, the mixture was aged at room temperature for 1 hour, and pH testing paper confirmed that the pH had become neutral. The mixture was concentrated under reduced pressure using an evaporator to remove the methanol, yielding 129.4 g of slightly yellow, scaly crystals (melting point 62.5-64.5°C, crude yield 100.0%). The NMR identification data for the resulting slightly yellow, scaly crystals are as follows: (Identification data) 31 P-NMR(DO); 57.06 ppm 1 H-NMR(D2O); 1.81~1.93ppm(m, 6H, -CH2-), 1.86~2.01ppm(m, 6H, P-CH2-), 3.03~3.10ppm(m, 15H, -CH2-N + H2-CH3), 4.66 ppm (s, 6H, -N + H2-) As a result, it was confirmed that the compound was tris(3-(N-methylaminopropyl))phosphine oxide trihydroiodide. 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. 64.7 g (0.1 mol) of the obtained tris(3-(N-methylaminopropyl))phosphine oxide trihydroiodide was dissolved in 500 ml of purified water and passed through the column from the top at a flow rate of SV = 1.0. 1000 ml of purified water was then passed through to obtain 1450 ml of basic aqueous solution. The water was removed by concentration using an evaporator to obtain 25.8 g of a pale yellow liquid (crude yield 98.0%). The NMR identification data for the obtained pale yellow liquid are as follows: (Identification data) 31 P-NMR(DO); 59.38 ppm 1 H-NMR(D2O); 1.49~1.58ppm(m, 6H, -CH2-), 1.68~1.78ppm(m, 6H, P-CH2-), 2.50~2.54ppm(m, 6H, -CH2-NH-), 3.00ppm(s, 9H, -NH-CH3), 4.69ppm(s, 3H, -NH-) As a result, it was confirmed that the compound was tris(3-(N-methylaminopropyl))phosphine oxide.

[0083] (Example 4) Synthesis of tris(3-(N-isopropylaminopropyl))phosphine oxide A 1 L four-neck flask equipped with a stirrer, thermometer, and dropping funnel was charged with 44.3 g (0.2 mol) of tris(3-aminopropyl)phosphine oxide obtained in Synthesis Example 2, 200 ml of isopropyl alcohol, and 86.1 g (0.7 mol) of isopropyl bromide, and the mixture was heated and stirred at reflux temperature for 12 hours. After cooling, the pH of the reaction solution was confirmed to be neutral using pH test paper. 50 ml of an aqueous solution containing 24.0 g (0.6 mol) of sodium hydroxide was added, and the mixture was concentrated under reduced pressure using an evaporator. 150 ml of isopropyl alcohol and anhydrous sodium sulfate were added, and the mixture was allowed to stand for 12 hours. The precipitate was filtered using a Buchner funnel equipped with Celite filter aid and filter paper, and the solvent was concentrated under reduced pressure using an evaporator, yielding 61.2 g of a pale yellow liquid (crude yield 88.1%). The NMR identification data for the resulting pale yellow liquid are as follows: (Identification data) 31 P-NMR(DO); 60.78 ppm 1 H-NMR(D2O); 0.91ppm(d, 18H, -CH3), 1.50~1.61ppm(m, 6H, -CH2-), 1.72~1.78ppm(m, 6H, P- CH2-), 2.52~2.58ppm(m, 6H, -CH2-NH-), 2.68~2.73ppm(m, 3H, -CH-), 4.68ppm(s, 3H, -NH-) As a result, it was confirmed that the compound was tris(3-(N-isopropylaminopropyl))phosphine oxide.

[0084] (Example 5) Synthesis of tris(3-(N-isopropanolaminopropyl))phosphine oxide A 100 ml two-neck flask equipped with a stirrer and a thermometer was charged with 10.0 g of the 40% aqueous solution of tris(3-aminopropyl)phosphine oxide obtained in Synthesis Example 2 (4.03 g, 0.018 mol as tris(3-aminopropyl)phosphine oxide) and 3.17 g (0.055 mol) of propylene oxide, and the mixture was stirred at room temperature for 1 hour and then heated at 60°C for 2 hours. After cooling, the reaction solution was concentrated under reduced pressure using an evaporator to obtain 6.57 g of a colorless, transparent liquid (yield 92.3%). The NMR identification data of the resulting colorless, transparent liquid is as follows: (Identification data) 31 P-NMR(DO); 60.39 ppm 1 H-NMR(D2O); 0.98~1.01ppm(m, 9H, -CH3), 1.46~1.73ppm(m, 12H, P-CH2-CH2-), 2. 26~2.54ppm(m, 12H, -CH2-NH-), 3.71~3.79ppm(m, 3H, -CH-), 4.68ppm(s, 3H, -NH-) As a result, it was confirmed that the compound was tris(3-(N-isopropanolaminopropyl))phosphine oxide.

[0085] (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 255.9 g of silica gel (wt. / g, average pore size 30 nm) 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 of tributyl(3-aminopropyl)phosphonium·β-alanine relative to the total mass of the carbon dioxide absorbent 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.

[0086] (Reference example 2) 38.0 g (0.172 mol) of tris(3-aminopropyl)phosphine oxide 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 70.0 g of silica gel (3-aminopropyl)phosphine oxide (70.0 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 108.9 g of a carbon dioxide absorbent in which tris(3-aminopropyl)phosphine oxide was impregnated onto silica gel. The impregnation rate of tris(3-aminopropyl)phosphine oxide relative to the total mass of the carbon dioxide absorbent was 35.0 mass%. The obtained carbon dioxide absorbent was evaluated in Carbon Dioxide Absorption Test 2 and a Heat Stability Test, which will be described later.

[0087] Example 6 30.5 g (0.1 mol) of tris(3-(N-ethylaminopropyl))phosphine oxide obtained in Example 1 was dissolved in 200 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 256.6 g of silica gel (wt. / g, average pore size 30 nm) was added and allowed 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 87.9 g of a carbon dioxide absorbent in which tris(3-(N-ethylaminopropyl))phosphine oxide was impregnated onto silica gel. The impregnation rate of tris(3-(N-ethylaminopropyl))phosphine oxide relative to the total mass of the carbon dioxide absorbent was 35.0 mass %. The obtained carbon dioxide absorbent was evaluated in Carbon Dioxide Absorption Test 1, Carbon Dioxide Absorption Test 2, Regeneration Test 1, Regeneration Test 2, and a heat stability test, which will be described later.

[0088] Example 7 30.5 g (0.1 mol) of the mixture containing tris(3-(N-ethylaminopropyl))phosphine oxide as the main component obtained in Example 2 was dissolved in 200 ml of pure water, and silica gel (CARiACT Q-30 manufactured by Fuji Silysia Chemical Ltd., particle size 1.70 to 64.00 mm, BET specific surface area 100 m 2 56.6 g of silica gel (wt. / g, average pore size 30 nm) was added and allowed 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 87.4 g of a carbon dioxide absorbent in which a mixture containing tris(3-(N-ethylaminopropyl))phosphine oxide as a main component was impregnated into silica gel. The impregnation rate of tris(3-(N-ethylaminopropyl))phosphine oxide relative to the total mass of the carbon dioxide absorbent 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.

[0089] Example 8 13.2 g (0.05 mol) of tris(3-(N-methylaminopropyl))phosphine oxide obtained in Example 3 was dissolved in 200 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 224.5 g of silica gel (3-(N-methylaminopropyl)) phosphine oxide (3.5 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, yielding 38.2 g of a carbon dioxide absorbent in which tris(3-(N-methylaminopropyl))phosphine oxide was impregnated onto silica gel. The impregnation rate of tris(3-(N-methylaminopropyl))phosphine oxide relative to the total mass of the carbon dioxide absorbent was 35.0 mass %. The obtained carbon dioxide absorbent was evaluated in Carbon Dioxide Absorption Test 2, which will be described later.

[0090] Example 9 34.8 g (0.1 mol) of tris(3-(N-isopropylaminopropyl))phosphine oxide obtained in Example 4 was dissolved in 200 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 64.6 g of silica gel (wt. / 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 100.1 g of a carbon dioxide absorbent in which tris(3-(N-isopropylaminopropyl))phosphine oxide was impregnated onto silica gel. The impregnation rate of tris(3-(N-isopropylaminopropyl))phosphine oxide relative to the total mass of the carbon dioxide absorbent 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.

[0091] Example 10 6.57 g (0.016 mol) of tris(3-(N-isopropanolaminopropyl))phosphine oxide obtained in Example 5 was dissolved in isopropanol to prepare a 20% solution. 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) was added thereto. 212.2 g of silica gel (3-(N-isopropanolaminopropyl)) phosphine oxide) was added and allowed to stand at room temperature until the silica gel became moisture permeable. The isopropanol added was completely removed by vacuum concentration using an evaporator, yielding 18.65 g of a carbon dioxide absorbent in which tris(3-(N-isopropanolaminopropyl))phosphine oxide was impregnated onto the silica gel. The impregnation rate of tris(3-(N-isopropanolaminopropyl))phosphine oxide relative to the total mass of the carbon dioxide absorbent was 35.0 mass %. The obtained carbon dioxide absorbent was evaluated in Regeneration Test 3, which will be described later.

[0092] (evaluation) (Carbon dioxide absorption test 1) 90 ml of the carbon dioxide absorbents obtained in Examples 6, 7, 9, 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 the carbon dioxide concentration reached saturation and 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.

[0093] [Table 1]

[0094] The results shown in Table 1 show that the carbon dioxide absorbents of Examples 6, 7 and 9 are superior to the carbon dioxide absorbent of Reference Example 1 in carbon dioxide absorption performance.

[0095] (Carbon dioxide absorption test 2) The carbon dioxide absorbents obtained in Examples 6 to 9 and Reference Examples 1 and 2 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.

[0096] [Table 2]

[0097] The results shown in Table 2 show that the carbon dioxide absorbents of Examples 6 to 9 are superior to the carbon dioxide absorbent of Reference Example 1 in terms of carbon dioxide absorption performance.

[0098] (Regeneration test 1) The carbon dioxide absorbent obtained in Example 6 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 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 carbon dioxide absorbent of Example 6 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 50°C and fully evacuated with a vacuum pump, thereby causing carbon dioxide to be desorbed and regenerated. The carbon dioxide absorbent was then regenerated by desorbing carbon dioxide, and the regeneration was repeated twice. 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

[0099] [Table 3]

[0100] (Regeneration test 2) The carbon dioxide absorbent obtained in Example 6 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 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 carbon dioxide absorbent of Example 6 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 30°C and fully evacuated with a vacuum pump, to desorb carbon dioxide and perform regeneration. The carbon dioxide absorbent was then regenerated by desorbing carbon dioxide, and the regeneration was repeated twice. The regeneration rate was calculated using the following formula. The results are shown in Table 4. Regeneration rate (%) = (absorption capacity at regeneration / initial absorption capacity) x 100

[0101] [Table 4]

[0102] The results shown in Tables 3 and 4 show that when a carbon dioxide absorbent that has absorbed carbon dioxide to saturation is heated in a vacuum (under reduced pressure) at a predetermined heating temperature to desorb carbon dioxide, the regenerated carbon dioxide absorbent regains its ability to absorb carbon dioxide, and the regenerated carbon dioxide absorbent has excellent absorption performance and regeneration rate.

[0103] (Regeneration test 3) The carbon dioxide absorbent obtained in Example 10 was placed in a 35 ml Erlenmeyer flask, weighed accurately to the nearest 0.1 mg, and carbon dioxide gas with a purity of 99.995% was blown into it at a flow rate of 100 / min at room temperature (25°C). The gas blowing was stopped when the weight was balanced. 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 10 that had absorbed carbon dioxide to saturation was transferred to a petri dish with a diameter of 30 mm and heated statically in a thermostatic oven maintained at 70°C to desorb carbon dioxide and perform 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 5. Regeneration rate (%) = (absorption capacity at regeneration / initial absorption capacity) x 100

[0104] [Table 5]

[0105] The results shown in Table 5 show that the regenerated carbon dioxide absorbent, which desorbs carbon dioxide by heating at a specified heating temperature in air (atmospheric pressure) rather than in a vacuum (reduced pressure), regains its ability to absorb carbon dioxide, and even though it is a regenerated carbon dioxide absorbent, it has excellent absorption performance and regeneration rate. This is extremely useful in that it can reduce energy costs during carbon dioxide capture.

[0106] (Heat stability test) The carbon dioxide absorbent obtained in Example 6 was packed into a 190 ml stainless steel clean pipe, and carbon dioxide gas with a purity of 99.995% was passed through it at a flow rate of 500 ml / min for 10 minutes to absorb the carbon dioxide. The weight was measured before and after the passage of air, and the increase in weight was used 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 the carbon dioxide absorbent. The entire amount of the carbon dioxide absorbent that had absorbed carbon dioxide was placed in a 200 mm diameter petri dish and heated statically in air at 120°C for 90 minutes to desorb carbon dioxide and perform regeneration. Next, the carbon dioxide absorbent regenerated by desorbing carbon dioxide was packed back into the stainless steel clean pipe to absorb carbon dioxide and regenerate it. The regeneration rate was calculated based on the following formula. The results are shown in Table 6. Regeneration rate (%) = (absorption capacity at regeneration / initial absorption capacity) x 100 The carbon dioxide absorbent obtained in Reference Example 2 was also subjected to carbon dioxide absorption and regeneration twice in the same manner. The results are shown in Table 7.

[0107] [Table 6]

[0108] [Table 7]

[0109] The results shown in Table 6 show that the regenerated carbon dioxide absorbent obtained by heating the carbon dioxide absorbent of Example 6, which had absorbed carbon dioxide, in air (atmospheric pressure) at a predetermined heating temperature to desorb carbon dioxide remained white in appearance and recovered its ability to absorb carbon dioxide, and that even the regenerated carbon dioxide absorbent had excellent absorption performance and regeneration rate. On the other hand, from the results shown in Table 7, it can be seen that the regenerated carbon dioxide absorbent obtained by heating the carbon dioxide absorbent of Reference Example 2, which had absorbed carbon dioxide, at a predetermined heating temperature in air (atmospheric pressure) to desorb carbon dioxide had a brown appearance and further deteriorated absorption performance.

Claims

1. The following general formula (1): 【Chemical 1】 (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 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 secondary amino group or a tertiary amino group. A phosphine oxide compound represented by the formula:

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

3. The following general formula (1): 【Chemical 1】 (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 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 secondary amino group or a tertiary amino group. A compound for use as a carbon dioxide absorbent, which is a phosphine oxide compound represented by the formula:

4. A carbon dioxide absorbent comprising the compound for carbon dioxide absorbents according to claim 3.

5. 5. The carbon dioxide absorbent according to claim 4, comprising a porous carrier and the compound for a carbon dioxide absorbent according to claim 3 supported on the porous carrier.

6. 6. The carbon dioxide absorbent according to claim 5, 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, clay mineral, or a composite thereof.

7. 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 5 to cause the carbon dioxide absorbent to absorb the carbon dioxide in the mixed gas, thereby separating carbon dioxide from the mixed gas.

8. a carbon dioxide separation step of contacting a mixed gas containing carbon dioxide with the carbon dioxide absorbent according to claim 5 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 30°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:

9. 9. The method for separating and capturing carbon dioxide according to claim 8, wherein the carbon dioxide separation step and the carbon dioxide capture step are repeatedly performed 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.

10. An apparatus characterized in that the carbon dioxide absorbent according to claim 4 is used.

11. 11. The apparatus of claim 10, wherein the apparatus is used in a power plant, a factory, or a transportation facility.

12. 11. The device of claim 10, wherein the device is a DAC device.

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