Phosphine oxide compound, compound for carbon dioxide absorbent, carbon dioxide absorbent, carbon dioxide separation method, carbon dioxide separation and recovery method, and device using carbon dioxide absorbent

Abstract

Provided is a novel trialkylphosphine oxide having an alkyl group in which an amino group is bonded to an alkyl group. The present invention relates to a phosphine oxide compound characterized by being represented by general formula (1) (in the formula, a, b and c each represent an integer of 1 to 10, R1, R2, and R3 each independently represent a primary amino group, a secondary amino group, or a tertiary amino group, and at least one among R1, R2, and R3 is a secondary amino group or a tertiary amino group.)

Description

Phosphine oxide compound, compound for carbon dioxide absorbent, carbon dioxide absorbent, carbon dioxide separation method, carbon dioxide separation and capture method, and device using carbon dioxide absorbent

[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.

[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 curb 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 to be used when 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.

[0005] JP 2016-10760 A JP 4-39324 A

[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 (α ３ P=O, α is an alkyl group (which may have a substituent), and an amino group (—NH ２ ) and, therefore, various applications other than as a curing agent for epoxy resins are expected.

[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] Depending on the application of trialkylphosphine oxide, oxidation stability may be required. ２ ) is easily oxidized, it is presumed that in such applications, a trialkylphosphine oxide with improved oxidation resistance is required.

[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 in which an amino group is bonded to the alkyl group. 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 that use the carbon dioxide absorbent, and an apparatus that uses the carbon dioxide absorbent.

[0012]

[0006] In view of the above circumstances, the present inventors have conducted extensive research and 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 thereby completed the present invention.

[0013]

[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]

[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 and at least one of the amino groups is a secondary amino group or a tertiary amino group.

[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 carbon dioxide separation and capture method, 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 capture 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 capturing the desorbed carbon dioxide.

[0022] The present invention (6) also provides an apparatus characterized in that the carbon dioxide absorbent of the present invention (3) is used.

[0023] 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. 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, which has excellent oxidation resistance. 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 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, in addition to the above-mentioned carbon dioxide absorption performance, have excellent oxidation resistance 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 that use the above-mentioned carbon dioxide absorbent, and an apparatus that uses the carbon dioxide absorbent.

[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]

[0026] (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 wherein at least one of the amino groups is a secondary amino group or a tertiary amino group.

[0027] The phosphine oxide compound represented by general formula (1) has three alkyl groups bonded to P in the phosphine oxide structure (P═O), with at least one of the three alkyl groups bonded to an amino group being 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 an 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, the alkyl group bonded to a secondary amino group or a tertiary amino group has better desorption properties for absorbed carbon dioxide than an alkyl group bonded to a primary amino group, enabling desorption of 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, it has a low vapor pressure and almost no volatility within a heating temperature range during regeneration after carbon dioxide absorption, for example, a 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 preferable 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 are each independently a primary amino group (—NH ２ ), a secondary amino group (—NH-β, where β represents an alkyl group which may be substituted), or a tertiary amino group (—Nβ ２ β represents an alkyl group which may be substituted. 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 ３In 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 a primary amino group, 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 ３ 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 an alkyl group, an alkyl group having a functional group, a cycloalkyl group, a halogenated alkyl group, an alkoxy group, and a halogen atom. The tertiary amino group also includes a cyclic amino group. Examples of the functional group in the alkyl group having a functional group include a hydroxyl group, an amino group, a carboxyl group, a mercapto group, an amide group, a carboxymethyl group, a carboxyethyl group, and a sulfonic acid group. In the present invention, from the viewpoint of oxidation resistance, R １ , R２ 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 ３is 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,

[0039] 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 is represented by the following general formula (1):

[0036]

[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 wherein at least one of the amino groups is a secondary amino group or a tertiary amino group.

[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 such phosphine oxides include bis(3-(N-ethylaminopropyl))(3-aminopropyl)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.

[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 and n-methylaminopropyl)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 and R １ , R ２ and R ３ a mixture of two of which are secondary amino groups and one of which is a primary amino group, or a phosphine oxide compound represented by general formula (1) in which R １ , R ２ and R ３ and R １ , R ２ and R ３ two of which are secondary amino groups and one of which is a 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 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 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 the phosphine oxide compounds represented by all 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 the phosphine oxide compounds represented by all general formula (1) is １ It is 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 and exists therein.

[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 pores therein, and can incorporate the 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. In addition, the porous carrier is a porous body capable of retaining water in its pores, such as activated carbon, silica gel, mesoporous silica, zeolite, molecular sieve, alumina and silica gel composite, alumina and mesoporous silica composite, etc., so that when 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 carbon dioxide absorbent compound from eluting from the porous carrier, and improving the carbon dioxide absorption performance of the carbon dioxide absorbent. The porous body capable of retaining water in its pores is not particularly limited as long as it can retain water in its pores, but examples include those that can contain 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 carrier is preferably 1.0 × 10 １ ~5.0 x 10 ３ m ２ / g, preferably 1.0×10 ２ ~2.0 x 10 ３ m ２ The pore volume of the porous carrier measured by gas adsorption 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, from the viewpoints of ease of handling and ability to easily support the liquid phosphine oxide compound represented by general formula (1), 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, and activated carbon and silica gel are particularly preferred.

[0050] Various activated carbons can be used in the present invention, including activated carbons 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-described porous carrier characteristics, 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-described 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 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 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 be supported, or 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 %, and 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, allowing carbon dioxide to be efficiently absorbed.

[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 can increase the contact area between the phosphine oxide compound represented by general formula (1) and carbon dioxide, 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, as 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 capturing 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, and transportation equipment such as automobiles, aircraft and ships. It is also useful as an absorbent used in DAC (Direct Air Capture) devices that separate and capture carbon dioxide directly from the atmosphere. In other words, the carbon dioxide absorbent of the present invention is suitable as a carbon dioxide absorbent used 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 carbon dioxide separation and capture method 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 of supplying a mixed gas containing carbon dioxide to an absorbent-packed column or absorbent-packed tower packed with the carbon dioxide absorbent of the present invention, bringing the mixed gas into contact with the carbon dioxide absorbent, and allowing 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, bringing 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 carbon dioxide separation 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 capture 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 a step in which, after the carbon dioxide separation step (A), the carbon dioxide absorbent packed in the absorbent-packed column or absorbent-packed tower is heated 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. In the carbon dioxide absorbent of the present invention, carbon dioxide can be desorbed 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, the steps 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 cost required for carbon dioxide capture. Furthermore, since carbon dioxide can be desorbed in air, a degassing device is not required, and since carbon dioxide can be desorbed at a relatively low temperature, exhaust heat from factories such as chemical plants, waste treatment facilities, and steel mills can be used.

[0075] In the carbon dioxide separation method and the 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.

[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 mmφ × 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 the column from above at a rate of SV = 1.0 using a tube pump. Pure water was then passed through the column until the effluent became neutral. Next, an aqueous solution containing 140.0 g (0.41 mol) of tributyl(3-aminopropyl)phosphonium bromide in 500 ml of pure water was passed through the column from above at a rate of SV = 1.0, followed by 1000 ml of pure water, to obtain 1550 g of an aqueous solution of tributyl(3-aminopropyl)phosphonium hydroxide. Neutralization titration with 1 / 10N 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 at room temperature in 500 g (0.12 mol) of the obtained aqueous solution of tributyl(3-aminopropyl)phosphonium hydroxide. The obtained mixed aqueous solution was concentrated under reduced pressure using an evaporator, and the concentrated solution was mixed with methanol to form a methanol solution, which was dehydrated overnight over anhydrous magnesium sulfate. The dehydrated methanol solution was then 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 of the obtained colorless, transparent viscous liquid is as follows: (Identification Data) ３１ P-NMR; 34.34ppm １ H-NMR; 0.80 ppm (t,9H,-CH３ ), 1.31 to 1.45 ppm (m, 12H, -CH ２ -), 1.54 to 1.59 ppm (m, 2H, -CH ２ -), 2.03 to 2.08 ppm (m, 8H, P-CH ２ -), 2.19 ppm (t, 2H, -CH ２ -COO), 2.58, 2.69ppm (t, 2H, -CH ２ -NH ２ ), 3.20, 3.21 ppm (s, -NH ２ As a result, it was confirmed to be tributyl(3-aminopropyl)phosphonium.beta.-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. At this time, the temperature was raised to 80°C using a hot water bath, and the gauge pressure indicated 0.93 MPa (absolute pressure 1.03 MPa). Next, 1.06 g (0.006 mol) of azobisisobutyronitrile was dissolved in 150 ml of toluene, and the mixture was injected in portions over 6 hours and aged overnight at 80°C. At this time, the gauge pressure indicated 0.01 MPa (absolute pressure 0.11 MPa). After overnight aging, 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 liquid was then extracted into a vacuum-evacuated eggplant-shaped flask, yielding 585 g of a colorless, transparent liquid. The resulting colorless, transparent liquid was then heated under reduced pressure (gauge pressure 4 kPa (absolute pressure 105.3 kPa), 80°C) to distill off excess allylamine and toluene. The vacuum and temperature were then further increased and the mixture was heated (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, yielding 120 g of a colorless, transparent liquid. The NMR identification data for the resulting colorless, transparent liquid is as follows: (Identification Data) ３１ P-NMR (D ２O); -29.73ppm １ H-NMR (D ２ O); 1.40 to 1.46 ppm (m, 6H, -CH ２ -), 1.52 to 1.61 ppm (m, 6H, P-CH ２ -), 2.63 to 2.71 ppm (m, 6H, -CH ２ -NH ２ ), 4.67ppm (s, 6H, -NH ２ ) As a result, it was confirmed to be tris(3-aminopropyl)phosphine. Next, a 1 L four-neck flask equipped with a stirrer and a thermometer was purged with nitrogen gas, and 92.4 g (0.45 mol) of the obtained tris(3-aminopropyl)phosphine and 500 ml of pure water were charged, and 56.1 g (0.495 mol) of 30% hydrogen peroxide diluted with 100 ml of pure water was added dropwise over one hour while maintaining the temperature at 70 to 75°C. After the dropwise addition, the mixture was aged for one hour, cooled to room temperature, and concentrated under reduced pressure using an evaporator to remove water, yielding 100.8 g of a colorless, transparent liquid. The NMR identification data of the obtained colorless, transparent liquid is as follows. (Identification Data) ３１ P-NMR (D ２ O); 60.77ppm １ H-NMR (D ２ O); 1.50 to 1.58 ppm (m, 6H, -CH ２ -), 1.71 to 1.77 ppm (m, 6H, P-CH ２ -), 2.57 to 2.60 ppm (t, 6H, -CH ２ -NH ２ ), 4.70ppm (s, 6H, -NH ２ As a result, it was confirmed to be tris(3-aminopropyl)phosphine oxide.

[0080] Example 1 Synthesis of tris(3-(N-ethylaminopropyl))phosphine oxide Into a 1 L four-neck flask equipped with a stirrer, a thermometer, and a dropping funnel, 44.3 g (0.2 mol) of tris(3-aminopropyl)phosphine oxide obtained in Synthesis Example 2 and 200 ml of pure water were charged and heated to 60 to 65°C. Furthermore, 98.1 g (0.9 mol) of ethyl bromide was gradually added dropwise so as not to cause intensive reflux. After the addition, the mixture was aged for 1 hour, cooled to room temperature, and a pH test paper was used to confirm that the pH was neutral. Water was removed by concentration under reduced pressure using an evaporator, yielding 108.0 g of a pale yellow, transparent liquid (crude yield 98.5%). The NMR identification data of the resulting pale yellow, transparent liquid is as follows: (Identification Data) ３１ P-NMR (D ２ O); 57.06ppm １ H-NMR (D ２ O); 1.12 to 1.14 ppm (t, 9H, -CH ３ ), 1.75-1.85ppm (m, 6H, -CH ２ -), 1.85 to 1.93 ppm (m, 6H, P-CH ２ -), 2.94 to 3.12 ppm (m, 12H, -CH ２ -N ＋ H ２ -CH ２ -), 4.65ppm (s, 6H, -N ＋ H ２-) As a result, the product was confirmed to be 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 charged into 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, and the mixture became cloudy. After stirring for 1 hour, the product was filtered using a Buchner funnel lined with an ethanol slurry of filter aid Celite (Hyflo Super Cel, Fujifilm Wako Pure Chemical Industries, Ltd.), and 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 is as follows: (Identification Data) ３１ P-NMR (D ２ O); 60.61ppm １ H-NMR (D ２ O); 0.89 to 0.93 ppm (m, 9H, -CH ３ ), 1.50 to 1.60 ppm (m, 6H, -CH ２ -), 1.65 to 1.68 ppm (m, 6H, P-CH ２ -), 2.40 to 2.58 ppm (m, 12H, -CH ２ -NH-CH ２ -), 4.68 ppm (s, 6H, -NH-). As a result, it was confirmed to be tris(3-(N-ethylaminopropyl))phosphine oxide.

[0081] Example 2 Synthesis of a mixture containing tris(3-(N-ethylaminopropyl))phosphine oxide as the main component Into a 1 L four-neck flask equipped with a stirrer, a thermometer, and a dropping funnel, 44.3 g (0.2 mol) of tris(3-aminopropyl)phosphine oxide obtained in Synthesis Example 2 and 200 ml of ethanol were charged and heated to 60 to 65°C. Furthermore, 98.1 g (0.9 mol) of ethyl bromide was gradually added dropwise so as not to cause intensive reflux. After the dropwise addition, the mixture was aged for 1 hour and then cooled to room temperature, and the pH was confirmed to be weakly basic using pH test paper. The ethanol was removed by concentration under reduced pressure 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 (Organo Corporation, Amberlite IRA400J Cl, exchange capacity 1.4 equivalents / resin volume L) was packed into a glass column (internal diameter 65 mmφ x 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 at a rate of SV = 1.0 using a tube pump. Pure water was then passed through the column 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 pure water and passed through the column from above at a rate of SV = 1.0. 1000 ml of pure water was then passed through the column to obtain 1450 ml of a basic aqueous solution. The solution was concentrated using an evaporator to remove the water, yielding 28.7 g of a pale yellow liquid (crude yield 94.0%). The NMR identification data for the resulting pale yellow liquid is as follows: (Identification data) ３１ P-NMR (CD ３ OD); 55.34ppm １ H-NMR (CD ３ OD); 1.03 to 1.10 ppm (m, 6.3H, -CH ３ ), 1.65 to 1.84 ppm (m, 12H, P-CH ２ -CH ２ -), 2.52 to 2.73 ppm (m, 10.2H, -CH ２ -NH-CH ２-), 4.76 ppm (s, 5.7H, -NH-). As a result, it was determined 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 44.3 g (0.2 mol) of tris(3-aminopropyl)phosphine oxide obtained in Synthesis Example 2 and 200 ml of methanol were charged into a 1 L four-neck flask equipped with a stirrer, a thermometer, and a dropping funnel, and 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 dropwise addition, the liquid was aged at room temperature for 1 hour, and it was confirmed with pH test paper that the pH had become neutral. The methanol was removed by vacuum concentration using an evaporator, yielding 129.4 g of slightly yellow, scaly crystals (melting point 62.5 to 64.5°C, crude yield 100.0%). The NMR identification data of the obtained slightly yellow, scaly crystals is as follows. (Identification Data) ３１ P-NMR (D ２ O); 57.06ppm １ H-NMR (D ２ O); 1.81 to 1.93 ppm (m, 6H, -CH ２ -), 1.86 to 2.01 ppm (m, 6H, P-CH ２ -), 3.03 to 3.10 ppm (m, 15H, -CH ２ -N ＋ H ２ -CH ３ ), 4.66ppm (s, 6H, -N ＋ H ２As a result, the product was confirmed to be tris(3-(N-methylaminopropyl))phosphine oxide trihydroiodide. A glass column (inner diameter 65 mmφ x length 500 mm) was packed with 1500 ml of ion exchange resin (Organo Corporation, Amberlite IRA400J Cl, 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 pure water until the effluent became neutral. 64.7 g (0.1 mol) of the resulting tris(3-(N-methylaminopropyl))phosphine oxide trihydroiodide was dissolved in 500 ml of pure water, and the resulting solution was passed through the column from above at a rate of SV = 1.0, followed by 1000 ml of pure water, yielding 1450 ml of a basic aqueous solution. The mixture was concentrated using an evaporator to remove water, yielding 25.8 g of a pale yellow liquid (crude yield: 98.0%). The NMR identification data of the pale yellow liquid obtained is as follows: (Identification Data) ３１ P-NMR (D ２ O); 59.38ppm １ H-NMR (D ２ O); 1.49 to 1.58 ppm (m, 6H, -CH ２ -), 1.68 to 1.78 ppm (m, 6H, P-CH ２ -), 2.50 to 2.54 ppm (m, 6H, -CH ２ -NH-), 3.00ppm (s, 9H, -NH-CH ３ ), 4.69 ppm (s, 3H, —NH—). As a result, it was confirmed to be tris(3-(N-methylaminopropyl))phosphine oxide.

[0083] Example 4 Synthesis of tris(3-(N-isopropylaminopropyl))phosphine oxide Into a 1 L four-neck flask equipped with a stirrer, thermometer, and dropping funnel, 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 were charged and heated with stirring at reflux temperature for 12 hours. After cooling, it was confirmed with pH test paper that the pH of the reaction solution was neutral. 50 ml of an aqueous solution of 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 off using a Buchner funnel lined 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 of the obtained pale yellow liquid is as follows: (Identification Data) ３１ P-NMR (D ２ O); 60.78ppm １ H-NMR (D ２ O); 0.91 ppm (d, 18H, -CH ３ ), 1.50 to 1.61 ppm (m, 6H, -CH ２ -), 1.72 to 1.78 ppm (m, 6H, P-CH ２ -), 2.52 to 2.58 ppm (m, 6H, -CH ２ -NH-), 2.68 to 2.73 ppm (m, 3H, -CH-), 4.68 ppm (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 Into a 100 ml two-neck flask equipped with a stirrer and a thermometer, 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 were charged, 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 obtained colorless, transparent liquid is as follows. (Identification Data) ３１ P-NMR (D ２ O); 60.39ppm １ H-NMR (D ２ O); 0.98 to 1.01 ppm (m, 9H, -CH ３ ), 1.46-1.73ppm (m, 12H, P-CH ２ -CH ２ -), 2.26 to 2.54 ppm (m, 12H, -CH ２ -NH-), 3.71 to 3.79 ppm (m, 3H, -CH-), 4.68 ppm (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 the solution was mixed with 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 ２55.9 g of silica gel (3-aminopropyl-1,3-dihydroxybenzoate, 2- ...

[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 the solution was mixed with 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 / g, average pore size 30 nm) was added, and the mixture was left to stand at room temperature until the silica gel became moisture permeable. The added water was completely distilled off by concentration under reduced pressure using an evaporator, yielding 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 the solution was mixed with 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 (3-(N-ethylaminopropyl))phosphine oxide (3-(N-ethylaminopropyl) / g, average pore diameter 30 nm) was added, and the mixture was left to stand at room temperature until the silica gel became moisture permeable. The added water was completely distilled off by concentration 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 the solution was mixed with 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 (tris(3-(N-ethylaminopropyl))phosphine oxide as a main component) was added to the silica gel, and the mixture was left to stand at room temperature until it became moisture permeable. The mixture was concentrated under reduced pressure using an evaporator to completely remove the added water, 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, which will be described later.

[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 the solution was mixed with 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 tris(3-(N-methylaminopropyl))phosphine oxide (3-(N-methylaminopropyl) / g, average pore diameter 30 nm) was added, and the mixture was left to stand at room temperature until the silica gel became moisture permeable. The added water was completely distilled off by concentration 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 the solution was mixed with 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 (3-(N-isopropylaminopropyl))phosphine oxide (3-(N-isopropylaminopropyl) / g, average pore diameter 30 nm) was added, and the mixture was left to stand at room temperature until the silica gel became moisture permeable. The added water was completely distilled off by concentration 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, which will be described later.

[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 tris(3-(N-isopropanolaminopropyl))phosphine oxide (12.2 g of 1-methyl-2-propanol-2-one, ...

[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 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 indoors 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]

[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, accurately measured to the nearest 0.1 mg, and carbon dioxide gas with a purity of 99.995% was blown into them at a flow rate of 200 ml / min at room temperature of 25°C. The weight was accurately measured to the nearest 0.1 mg every 10 minutes, and the 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 results are shown in Table 2.

[0096]

[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 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 determined as the amount of carbon dioxide absorbed per gram of carbon dioxide absorbent. The carbon dioxide absorbent of Example 6, which had absorbed carbon dioxide to saturation, was transferred to a 50 mm diameter Petri dish and heated statically in a vacuum dryer maintained at 50°C and fully evacuated with a vacuum pump, to desorb carbon dioxide and perform regeneration. Next, the carbon dioxide absorbent regenerated by desorbing carbon dioxide was again loaded into a 35 ml Erlenmeyer flask, and carbon dioxide absorption and regeneration were repeated twice. The regeneration rate was calculated based on the following formula. The results are shown in Table 3. Regeneration rate (%) = (absorption capacity at regeneration / initial absorption capacity) x 100

[0099]

[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 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 determined as the amount of carbon dioxide absorbed per gram of carbon dioxide absorbent. The carbon dioxide absorbent of Example 6, which had absorbed carbon dioxide to saturation, was transferred to a 50 mm diameter Petri dish and heated statically in a vacuum dryer maintained at 30°C and fully evacuated with a vacuum pump, to desorb carbon dioxide and perform regeneration. Next, the carbon dioxide absorbent regenerated by desorbing carbon dioxide was again loaded into a 35 ml Erlenmeyer flask, and carbon dioxide absorption and regeneration were repeated twice. The regeneration rate was calculated based on the following formula. The results are shown in Table 4. Regeneration rate (%) = (absorption capacity at regeneration / initial absorption capacity) x 100

[0101]

[0102] From the results shown in Tables 3 and 4, it is understood that the 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 the carbon dioxide, and the regenerated carbon dioxide absorbent regains its ability to absorb carbon dioxide, and that even 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, accurately measured to the nearest 0.1 mg, and carbon dioxide gas with a purity of 99.995% was blown into the flask at a flow rate of 100 / min at room temperature (25°C). The 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 determined as the amount of carbon dioxide absorbed per gram of carbon dioxide absorbent. The carbon dioxide absorbent of Example 10, which had absorbed carbon dioxide to saturation, was transferred to a 30 mm diameter Petri dish and heated statically in a thermostatic oven maintained at 70°C to desorb carbon dioxide and perform regeneration. Next, the carbon dioxide absorbent regenerated by desorbing carbon dioxide was filled again into a 35 ml Erlenmeyer flask, and carbon dioxide absorption and regeneration were repeated five times. The regeneration rate was calculated based on the following formula. The results are shown in Table 5. Regeneration rate (%) = (absorption capacity upon regeneration / initial absorption capacity) × 100

[0104]

[0105] The results shown in Table 5 show that the regenerated carbon dioxide absorbent, which has been desorbed by heating at a predetermined heating temperature in air (atmospheric pressure) rather than in a vacuum (reduced pressure), regains its ability to absorb carbon dioxide, and is excellent in both absorption performance and regeneration rate, even though it is a regenerated carbon dioxide absorbent. 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 increased weight was used as the amount of carbon dioxide absorbed to calculate the number of moles. The absorption capacity was determined as the amount of carbon dioxide absorbed per gram of carbon dioxide absorbent. The entire 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 again into the stainless steel clean pipe, and carbon dioxide absorption and regeneration were performed. 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) × 100 Furthermore, the carbon dioxide absorbent obtained in Reference Example 2 was subjected to carbon dioxide absorption and regeneration twice in the same manner. The results are shown in Table 7.

[0107]

[0108]

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

Claims

1. The following general formula (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 wherein at least one of the groups is a secondary amino group or a tertiary amino group.

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): (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 wherein at least one of the groups is a secondary amino group or a tertiary amino group.

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

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

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, thereby causing the carbon dioxide absorbent to absorb the carbon dioxide in the mixed gas, thereby separating carbon dioxide from the mixed gas.

8. A method for separating and recovering carbon dioxide, comprising: a carbon dioxide separation step of contacting a mixed gas containing carbon dioxide with the carbon dioxide absorbent according to claim 5, causing 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, thereby desorbing carbon dioxide from the carbon dioxide absorbent that has absorbed carbon dioxide, thereby regenerating the carbon dioxide absorbent and recovering the desorbed carbon dioxide.

9. The carbon dioxide separation and capture method described in claim 8, characterized in that the carbon dioxide separation step and the carbon dioxide capture step are repeated two or more times by using the regenerated carbon dioxide absorbent obtained by carrying out the carbon dioxide capture step as the carbon dioxide absorbent with which the mixed gas containing the carbon dioxide is contacted in the carbon dioxide separation step.

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

11. The device according to claim 10, characterized in that the device is used in a power plant, a factory or a transportation equipment.

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

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