Phosphine oxide compound, compound for carbon dioxide absorbent, carbon dioxide absorbent, method for separating carbon dioxide, method for separating and recovering carbon dioxide, and device using carbon dioxide absorbent

Abstract

The purpose of the present invention is to provide: a novel phosphine oxide compound; a compound for a carbon dioxide absorbent, the compound being composed of the phosphine oxide compound; and a carbon dioxide absorbent. The present invention provides: a phosphine oxide compound which is characterized by being represented by general formula (1) (in the formula, a, b, and c independently represent an integer of 1 to 10 inclusive, and R1 represents a primary amino group, a secondary amino group, or a tertiary amino group); a compound for a carbon dioxide absorbent, the compound being composed of the phosphine oxide compound; and a carbon dioxide absorbent.

Description

Phosphine oxide compounds, carbon dioxide absorbent compounds, carbon dioxide absorbents, carbon dioxide separation methods, carbon dioxide separation and recovery methods, and apparatus using carbon dioxide absorbents.

[0001] The present invention relates to phosphine oxide compounds, compounds for carbon dioxide absorbents, carbon dioxide absorbents, carbon dioxide separation methods, carbon dioxide separation and recovery methods, and apparatus using carbon dioxide absorbents.

[0002] In recent years, increased consumption of fossil fuels such as oil and coal due to industrial activities, as well as deforestation, has led to a continuous increase in the concentration of greenhouse gases such as carbon dioxide and methane in the atmosphere, resulting in global warming. If this warming continues at this rate, it is believed that serious consequences will appear in various aspects of life, including desertification of the Earth's surface, rising sea levels, and changes in ecosystems.

[0003] In this context, technologies for reducing carbon dioxide emissions and capturing carbon dioxide are attracting attention as a way to prevent global warming and reduce greenhouse gas emissions. Technologies for capturing carbon dioxide include chemical absorption, physical absorption, solid absorption, and membrane separation, but chemical absorption is mainly used because it can handle a wide range of concentrations. This chemical absorption method involves absorbing carbon dioxide into a liquid through a chemical reaction, and then releasing and capturing the carbon dioxide by heating the absorbent liquid.

[0004] Many reports concern amine-based solutions and ionic liquids used for absorbing carbon dioxide. For example, Patent Document 1 discloses an alkyl polyamine-based non-aqueous solvent absorbent that does not form precipitates when absorbing carbon dioxide and has high carbon dioxide absorption capacity. Patent Document 2 describes how a carbon dioxide absorbent with higher carbon dioxide absorption capacity than conventional ones was obtained by supporting a phosphonium-based ionic liquid having an amino group at some of the ends of the alkyl chain on a porous material.

[0005] Japanese Patent Publication No. 2018-187574, International Publication No. 2024 / 085086, Brochure

[0006] Of the aforementioned patent documents, the carbon dioxide absorbent using an amine-based solution described in Patent Document 1 has excellent carbon dioxide absorption capacity, but when heated to desorb the absorbed carbon dioxide, the amine is released into the atmosphere, raising concerns about its impact on the environment. Furthermore, the carbon dioxide absorbent using an ionic liquid described in Patent Document 2 has virtually no vapor pressure, thus reducing the energy required to desorb the absorbed carbon dioxide, but there is still room for improvement in its carbon dioxide absorption performance.

[0007] Therefore, the object of the present invention is to solve at least one of the following problems. That is, the object of the present invention is to provide a novel phosphine oxide compound. Furthermore, the object of the present invention is to provide a carbon dioxide absorbent compound and carbon dioxide absorbent that have excellent carbon dioxide absorption performance, and furthermore, a carbon dioxide absorbent that, in addition to the above carbon dioxide absorption performance, allows carbon dioxide to be easily desorbed when the absorbent is regenerated. Furthermore, the object of the present invention is to provide a carbon dioxide separation method using the above carbon dioxide absorbent, a carbon dioxide separation and recovery method, and an apparatus using the carbon dioxide absorbent.

[0008] In view of the above circumstances, the present inventors conducted extensive research and, as a result, discovered that a polymeric phosphine oxide compound represented by the following general formula (1), which has the structure of a secondary amine as a repeating unit, has excellent oxidation resistance and durability, as well as excellent carbon dioxide absorption capacity, and can desorb absorbed carbon dioxide with low energy, thus completing the present invention.

[0009] In other words, the present invention (1) is the following general formula (1):

[0010]

[0011] (In the formula, a, b, and c represent integers between 1 and 10, and R １ The present invention provides a phosphine oxide compound characterized by being represented as (where represents a primary amino group, a secondary amino group, or a tertiary amino group).

[0012] Furthermore, the present invention (2) provides a compound for carbon dioxide absorbent, characterized in that it is a phosphine oxide compound of the present invention (1).

[0013] Furthermore, the present invention (3) provides a carbon dioxide absorbent characterized by containing the carbon dioxide absorbent compound of the present invention (2).

[0014] Furthermore, the present invention (4) provides a carbon dioxide separation method characterized by having a carbon dioxide separation step of separating carbon dioxide from a mixed gas by contacting the carbon dioxide absorbent of the present invention (3) with a mixed gas containing carbon dioxide, thereby causing the carbon dioxide absorbent to absorb the carbon dioxide in the mixed gas.

[0015] Furthermore, the present invention (5) provides a carbon dioxide separation and recovery method characterized by comprising: a carbon dioxide separation step of contacting the carbon dioxide absorbent of the present invention (3) with a mixed gas containing carbon dioxide, thereby separating carbon dioxide from the mixed gas by causing the carbon dioxide absorbent to absorb the carbon dioxide in 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 to 150°C, 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.

[0016] Furthermore, the present invention (6) provides an apparatus characterized in that the carbon dioxide absorbent of the present invention (3) is used.

[0017] The present invention provides novel phosphine oxide compounds. Furthermore, the present invention provides carbon dioxide absorbent compounds and carbon dioxide absorbents with excellent carbon dioxide absorption performance, and further, carbon dioxide absorbents that, in addition to the above carbon dioxide absorption performance, allow for easy desorption of carbon dioxide when the absorbent is regenerated. Moreover, the present invention provides a carbon dioxide separation method using the above carbon dioxide absorbent, a carbon dioxide separation and recovery method, and an apparatus using the carbon dioxide absorbent.

[0018] The present invention will be described below based on preferred embodiments. The phosphine oxide compound of the present invention is given by the following general formula (1):

[0019]

[0020] (In the formula, a, b, and c represent integers between 1 and 10, and R １ (where represents a primary amino group, a secondary amino group, or a tertiary amino group.) This is a phosphine oxide compound represented by .

[0021] The phosphine oxide compound represented by general formula (1) has three polymer chains, each containing a repeating unit of a secondary amine structure, bonded to the phosphorus (P) in the phosphine oxide structure (P=O). Because the phosphine oxide compound represented by general formula (1) contains polymer chains with repeating units of a secondary amine structure, it can increase the chemical carbon dioxide absorption capacity of the amine. Furthermore, because the phosphine oxide compound represented by general formula (1) contains polymer chains with repeating units of a secondary amine structure, it is less susceptible to air oxidation and exhibits excellent oxidation resistance and durability.

[0022] In general formula (1), a, b, and c represent integers between 1 and 10. Furthermore, a preferably represents an integer between 1 and 4, more preferably between 2 and 4. Also, b preferably represents an integer between 1 and 4, more preferably between 2 and 4. Also, c preferably represents an integer between 1 and 4, more preferably between 2 and 4. The numbers a, b, and c may be the same or different. Having a, b, and c within this range makes synthesis easy, thus facilitating industrial production or availability.

[0023] The phosphine oxide compound represented by general formula (1) has three polymer chains, each having a primary, secondary, or tertiary amino group at its terminus, attached to the P of the phosphine oxide structure (P=O). That is, R in general formula (1) １ is a primary amino group (-NH ２ ), secondary amino group (-NH-β, where β indicates an optionally substituted alkyl group), tertiary amino group (-Nβ ２, β represents an optionally substituted alkyl group.). R １ is preferably a secondary amino group or a tertiary amino group, and particularly preferably a secondary amino group, in that it is superior in oxidation resistance compared to the case where it is a primary amino group. R １ is preferably a secondary amino group or a tertiary amino group, and particularly preferably a secondary amino group, in that it is superior in the desorbability of carbon dioxide compared to the case where it is a primary amino group when used as a carbon dioxide absorbent. Also, R １ is preferably a primary amino group in that it is superior in the absorption performance of carbon dioxide when used as a carbon dioxide absorbent.

[0024] The secondary amino group related to R １ is an amino group to which one hydrogen and one substituent are bonded, and the tertiary amino group is an amino group to which two substituents are bonded. Examples of the substituent bonded to the secondary amino group or the tertiary amino group include substituents such as 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. In the case of an alkyl group having a functional group, examples of the 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, the secondary amino group or the tertiary amino group related to R １ is preferably an amino group in which the substituent is an alkyl group having 1 to 10 carbon atoms, and more preferably an amino group in which the substituent is an alkyl group having 1 to 4 carbon atoms. The alkyl group includes a linear alkyl group, a branched alkyl group, and a cyclic alkyl group.

[0025] Specific examples of the branched alkyl group having 1 to 10 carbon atoms include an isopropyl group, an isobutyl group, an s-butyl group, a t-butyl group, an isopentyl group, an s-pentyl group, a t-pentyl group, an isohexyl group, an s-hexyl group, a t-hexyl group, and an ethylhexyl group. In the present invention, an isopropyl group is more preferable from the viewpoint of ease of synthesis.

[0026] Examples of the cyclic alkyl group having 1 to 10 carbon atoms include cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, 2-methylcyclopentyl group, 3-methylcyclopentyl group, cycloheptyl group, 2-methylcyclohexyl group, 3-methylcyclohexyl group, 4-methylcyclohexyl group, cyclooctyl group, 2-methylcycloheptyl group, 3-methylcycloheptyl group, 4-methylcycloheptyl group, and 5-methylcycloheptyl group. In the present invention, the cyclohexyl group is more preferred from the viewpoint of ease of synthesis.

[0027] When the phosphine oxide compound of the present invention is used as a carbon dioxide absorbent, it can exhibit excellent carbon dioxide absorption performance, in that respect, R １ It is particularly preferable that R is a primary amino group. Furthermore, even when the absorbent is regenerated by desorbing the absorbed carbon dioxide, the ability to absorb carbon dioxide is restored, resulting in a regenerated carbon dioxide absorbent with excellent carbon dioxide absorption performance. In general formula (1), R １ It is particularly preferable that the substituent is an amino group with a methyl group, an ethyl group, or an n-propyl group.

[0028] Examples of phosphine oxide compounds represented by general formula (1) include tris(3-(3-aminopropyl)aminopropyl)phosphine oxide, tris(3-(2-aminoethyl)aminopropyl)phosphine oxide, tris(3-(3-(3-aminopropyl)aminopropyl)aminopropyl)phosphine oxide, tris(3-(3-(2-aminoethyl)aminopropyl)aminopropyl)phosphine oxide, and tris(3-(3-(3-(2-aminoethyl)aminopropyl)aminopropyl)aminopropyl)phosphine oxide.

[0029] The carbon dioxide absorbent compound of the present invention is given by the following general formula (1):

[0030]

[0031] (In the formula, a, b, and c represent integers between 1 and 10, and R １ This compound for carbon dioxide absorbers is characterized by being a phosphine oxide compound represented by (where represents a primary amino group, a secondary amino group, or a tertiary amino group).

[0032] The carbon dioxide absorbent compound of the present invention can absorb carbon dioxide through the reaction of the secondary amine structure of the polymer chain of the phosphine oxide compound represented by general formula (1), optionally, the terminal primary amino group, secondary amino group, or tertiary amino group with carbon dioxide. In other words, the phosphine oxide compound of the present invention is a carbon dioxide absorbent compound 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 carbon dioxide absorbent compound 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.

[0033] The carbon dioxide absorbent of the present invention is characterized by containing the carbon dioxide absorbent compound of the present invention. In other words, the carbon dioxide absorbent of the present invention is 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) in the carbon dioxide absorbent of the present invention is the same as the phosphine oxide compound represented by general formula (1) in the phosphine oxide compound of the present invention.

[0034] Examples of phosphine oxide compounds represented by general formula (1) used in the carbon dioxide absorbent of the present invention include tris(3-(3-aminopropyl)aminopropyl)phosphine oxide, tris(3-(2-aminoethyl)aminopropyl)phosphine oxide, tris(3-(3-(3-aminopropyl)aminopropyl)aminopropyl)phosphine oxide, tris(3-(3-(2-aminoethyl)aminopropyl)aminopropyl)phosphine oxide, and tris(3-(3-(3-(2-aminoethyl)aminopropyl)aminopropyl)aminopropyl)phosphine oxide.

[0035] The phosphine oxide compound represented by general formula (1) used in the carbon dioxide absorbent of the present invention is R １ If it is a primary amino group, it has excellent carbon dioxide absorption performance. Also, R １ If the group is a secondary or tertiary amino group, it exhibits excellent oxidation resistance, resulting in superior durability against repeated absorption and desorption of carbon dioxide, as well as excellent desorption of absorbed carbon dioxide. Furthermore, phosphine oxide compounds represented by general formula (1) exhibit excellent oxidation resistance and durability due to having a secondary or tertiary amino group in the polymer chain.

[0036] The carbon dioxide absorbent of the present invention may contain two or more compounds for carbon dioxide absorbent of the present invention. That is, the carbon dioxide absorbent of the present invention may contain two or more phosphine oxide compounds represented by general formula (1). For example, the carbon dioxide absorbent of the present invention may contain, among the phosphine oxide compounds represented by general formula (1), R １ Those with primary amino groups, and R １ A mixture of a secondary amino group, or a phosphine oxide compound represented by general formula (1), R １ Those with primary amino groups, and R １ Those with a tertiary amino group, and R １ Those with a secondary amino group, and R １ A mixture of a tertiary amino group is an example.

[0037] In the carbon dioxide absorbent of the present invention, the form in which the phosphine oxide compound represented by general formula (1) exists is not particularly limited. For example, it may exist supported on a carrier, dissolved in an aqueous solvent, or as a mixture with a soluble organic solvent or amine compound.

[0038] The carbon dioxide absorbent of the present invention is characterized by comprising a porous carrier and a carbon dioxide absorbent compound of the present invention supported on the porous carrier. In other words, 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 in liquid form, is physically adsorbed onto the surface or into the pores inside the porous carrier, thereby allowing the phosphine oxide compound represented by general formula (1) to be supported on the porous carrier.

[0039] 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 many pores inside and is capable of physically adsorbing and retaining a phosphine oxide compound represented by general formula (1) on the surface or inside the porous carrier. Examples of porous carriers include activated carbon, silica gel, layered silicates, mesoporous silica, zeolites, vermiculite, molecular sieves, porous silica, diatomaceous earth, porous resins, porous fibers, porous metal-organic structures, porous alumina, porous ceramics, porous concrete, activated clay, or clay minerals. Activated carbon, silica gel, zeolites, and molecular sieves are preferred because they can support a large amount of the phosphine oxide compound represented by general formula (1). Furthermore, if the porous carrier is a porous material capable of retaining water within its pores, such as activated carbon, silica gel, zeolite, or molecular sieve, then when the gas to be treated containing carbon dioxide contains moisture, the moisture in the gas is adsorbed into the pores of the porous material. This prevents the carbon dioxide absorbent compound from leaching out of the porous carrier, thus improving the carbon dioxide absorption performance of the carbon dioxide absorbent. The porous material capable of retaining water within its pores is not particularly limited as long as it can retain water within its pores, but examples include materials that can contain water at a water content of 5 to 30% by mass, preferably 10 to 25% by mass.

[0040] The BET specific surface area of ​​the porous carrier is preferably 1.0 × 10⁻⁶. １ ~5.0 x 10 ３ I understand ２ / g, preferably 1.0 × 10 ２ ~2.0 x 10 ３ I understand ２ The value is / g. Furthermore, the pore volume of the porous carrier obtained by the gas adsorption method is preferably 0.1 to 2.0 mL / g, and more preferably 0.3 to 1.5 mL / g.

[0041] The porous carrier can take the form of, for example, granular, powdery, fibrous, plate-like, cylindrical, or honeycomb-like structures. Of these, granular or powdery forms are preferred from the viewpoint of contact with mixed gases containing carbon dioxide and packing into packing equipment such as columns and towers. The porous carrier may also be a molded body.

[0042] Among porous carriers, activated carbon, silica gel, zeolite, and molecular sieves are preferred from the viewpoint of ease of handling and the ability to easily support liquid phosphine oxide compounds represented by general formula (1), with activated carbon and silica gel being particularly preferred.

[0043] Various types of activated carbon can be used as the activated carbon in the present invention, for example, activated carbon made from wood, coconut shells, coal, petroleum pitch, coke, coal tar, etc. The activated carbon may also be a molded body. In addition to the characteristics of the porous carrier described above, the activated carbon preferably has physical properties measured according to JIS K1474 (Activated Carbon Test Method) such as a loss on drying of 0.1 to 5.0%, a residue on ignition of 0.1 to 5.0%, a packing density of 0.25 to 0.85 g / ml, an acetone adsorption performance of 14.0 to 41.0%, an iodine adsorption performance of 600 to 2600 mg / g, and a hardness of 90.0 to 100.0%.

[0044] Various types of silica gel can be used in the present invention, and for example, those containing 99% by mass or more, and particularly 99.9% by mass or more, of silicon dioxide are preferred. The silica gel may be a molded body. In addition to the porous carrier properties described above, 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 drying loss of 10% or less.

[0045] Various types of zeolites can be used in the present invention, including LTA-type zeolite, FER-type zeolite, MWW-type zeolite, MFI-type zeolite, MOR-type zeolite, LTL-type zeolite, FAU-type zeolite, BEA-type zeolite, and the like. The zeolite may also be a molded body. In addition to the porous carrier properties described above, it is preferable that the zeolite has an average particle size of 0.01 to 15 mm as measured by a scanning electron microscope.

[0046] In the carbon dioxide absorbent of the present invention, when two or more phosphine oxide compounds represented by general formula (1) are supported on a porous carrier, the two or more phosphine oxide compounds represented by general formula (1) may be supported in the form of a mixed solution, or each of the two or more phosphine oxide compounds represented by general formula (1) may be supported on a different part of the porous carrier. That is, for example, when supporting two phosphine oxide compounds represented by general formula (1) on a porous carrier, the two phosphine oxide compounds represented by general formula (1) may be mixed first, and the resulting mixed solution may be incorporated into the surface or pores of the porous carrier for support, or one of the two phosphine oxide compounds represented by general formula (1) may be incorporated into the surface or pores of the porous carrier first, and then the other phosphine oxide compound represented by general formula (1) may be incorporated into the surface or pores of the porous carrier to support the two phosphine oxide compounds represented by general formula (1). The same applies when three or more phosphine oxide compounds represented by general formula (1) are supported on a porous carrier.

[0047] 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% by mass, more preferably 20 to 40% by mass, relative to the total carbon dioxide absorbent. By having the amount of phosphine oxide compound represented by general formula (1) impregnated in the carbon dioxide absorbent within the above range, it can be uniformly present on the inner surface of the pores of the porous carrier, thereby enabling efficient absorption of carbon dioxide.

[0048] The carbon dioxide absorbent of the present invention is a phosphine oxide compound represented by general formula (1) that is supported on a porous carrier and is capable of chemically absorbing carbon dioxide. As a result, carbon dioxide can be absorbed more efficiently when the temperature of the carbon dioxide absorbent is between -20°C and 50°C, and the carbon dioxide is easily removed, making it easy to regenerate the carbon dioxide absorbent.

[0049] Because the carbon dioxide absorbent of the present invention is spread out on the surface of a porous carrier with a large surface area, the contact area between the phosphine oxide compound represented by general formula (1) and carbon dioxide can be increased. Therefore, the carbon dioxide absorbent of the present invention can achieve high carbon dioxide absorption efficiency.

[0050] In the carbon dioxide absorbent of the present invention, the carbon dioxide absorbent compound, which is a phosphine oxide compound represented by general formula (1), has a high molecular weight. Therefore, the carbon dioxide absorbent compound does not easily penetrate the pores inside the porous carrier, and the carbon dioxide absorbent compound is easily selectively supported on the surface of the porous carrier. In the case of low molecular weight carbon dioxide absorbent compounds, the carbon dioxide absorbent compound that penetrates the pores inside the porous carrier does not easily come into contact with carbon dioxide and may not function sufficiently as a carbon dioxide absorbent. However, in the carbon dioxide absorbent of the present invention, the carbon dioxide absorbent compound supported on the surface of the porous carrier reliably comes into contact with carbon dioxide and functions sufficiently as a carbon dioxide absorbent, thus eliminating waste and increasing the carbon dioxide absorption efficiency. The carbon dioxide absorbent of the present invention can effectively utilize the carbon dioxide absorption capacity of the carbon dioxide absorbent compound.

[0051] In the carbon dioxide absorbent of the present invention, the carbon dioxide absorbent compound, which is a phosphine oxide compound represented by general formula (1), has both a hydrophilic portion, which is a secondary amine structure, and a lipophilic portion, which is a hydrocarbon chain. Because it possesses both hydrophilic and lipophilic properties, the carbon dioxide absorbent compound of the present invention is easily supported on both hydrophilic porous carriers and lipophilic porous carriers.

[0052] Since the carbon dioxide absorbent of the present invention is supported on a solid carrier, it can be used by filling columns or reaction towers. Furthermore, compared to liquid carbon dioxide absorbents, the carbon dioxide absorbent of the present invention forms appropriate gaps when filled into columns or reaction towers, allowing for more efficient contact with carbon dioxide or carbon dioxide-containing gases.

[0053] The carbon dioxide absorbent of the present invention can separate and recover carbon dioxide from a mixed gas containing carbon dioxide. The other components of the mixed gas are not particularly limited, as long as the gas contains carbon dioxide. Examples of the 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, water, etc. The concentration of carbon dioxide in the mixed gas is not particularly limited and may be a high concentration with a purity of about 100%, or it may be a concentration similar to that found in the atmosphere.

[0054] The carbon dioxide absorbent of the present invention is useful as an absorbent for separating and recovering carbon dioxide from mixed gases containing carbon dioxide emitted from sources such as power plants (coal-fired and natural gas-fired), factories (chemical plants, waste treatment plants, steel mills, etc.), and transportation equipment (automobiles, aircraft, ships, etc.). It is also useful as an absorbent used in DAC (Direct Air Capture) devices that directly separate and recover carbon dioxide 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 equipment used in power plants, factories, and transportation equipment, as well as DAC devices.

[0055] Next, a method for separating carbon dioxide and a method for separating and recovering carbon dioxide using the carbon dioxide absorbent of the present invention will be described.

[0056] The present invention provides a carbon dioxide separation method characterized by having a carbon dioxide separation step (A) in which carbon dioxide is separated from a mixed gas by contacting a carbon dioxide absorbent of the present invention with a mixed gas containing carbon dioxide, thereby allowing the carbon dioxide absorbent to absorb the carbon dioxide in the mixed gas.

[0057] The present invention provides a carbon dioxide separation and recovery method comprising: a carbon dioxide separation step (A) in which a carbon dioxide absorbent of the present invention is brought into contact with a mixed gas containing carbon dioxide, thereby allowing the carbon dioxide absorbent to absorb the carbon dioxide in the mixed gas and separating the carbon dioxide from the mixed gas; and a carbon dioxide recovery step (B) in which the carbon dioxide absorbent that has absorbed carbon dioxide in the carbon dioxide separation step is heated at a temperature of 30°C to 150°C to desorb the carbon dioxide from the carbon dioxide absorbent, thereby regenerating the carbon dioxide absorbent and recovering the desorbed carbon dioxide.

[0058] In the carbon dioxide separation method and the carbon dioxide separation and recovery 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 is the same.

[0059] The carbon dioxide separation step (A) is a step in which the carbon dioxide absorbent of the present invention is brought into contact with a mixed gas containing carbon dioxide, thereby causing the carbon dioxide absorbent of the present invention to absorb the carbon dioxide in the mixed gas.

[0060] One example of the carbon dioxide separation process (A) is to supply a mixed gas containing carbon dioxide to an absorbent-packed column or absorbent-packed tower filled with the carbon dioxide absorbent of the present invention, bring the mixed gas into contact with the carbon dioxide absorbent, and separate the carbon dioxide from the mixed gas by allowing the carbon dioxide absorbent to absorb the carbon dioxide in the mixed gas. In this form of carbon dioxide separation process (A), the mixed gas is brought into contact with the carbon dioxide absorbent by supplying the mixed gas to the absorbent-packed column or absorbent-packed tower, and the mixed gas that has been in contact with the carbon dioxide absorbent within the absorbent-packed column or absorbent-packed tower is discharged from the absorbent-packed column or absorbent-packed tower. Furthermore, the method of packing the carbon dioxide absorbent of the present invention into the absorbent-packed column or absorbent-packed tower is not particularly limited and can be carried out under atmospheric pressure or reduced pressure.

[0061] 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 perform its function, but from the viewpoint of more efficiently absorbing carbon dioxide, it is preferable that the temperature be between -20°C and 50°C, preferably between -10°C and 30°C, and more preferably around room temperature of 25°C.

[0062] The pressure (absolute pressure) in the carbon dioxide separation process (A) is not particularly limited and can be carried out under atmospheric pressure.

[0063] In the carbon dioxide separation step (A), the carbon dioxide absorbent comes into contact with a mixed gas containing carbon dioxide, causing the carbon dioxide in the mixed gas to be absorbed by the carbon dioxide absorbent of the present invention, thereby separating the carbon dioxide from the mixed gas. In addition, the carbon dioxide separation step (A) yields a carbon dioxide absorbent that has absorbed carbon dioxide.

[0064] The carbon dioxide separation and recovery method of the present invention includes a carbon dioxide recovery step (B) in which a carbon dioxide absorbent that has absorbed carbon dioxide in a carbon dioxide separation step is regenerated and carbon dioxide is recovered. The carbon dioxide recovery step (B) is a step in which carbon dioxide is removed from the carbon dioxide absorbent that has absorbed carbon dioxide in a carbon dioxide separation step (A) by heating the carbon dioxide absorbent that has absorbed carbon dioxide in a carbon dioxide separation step (A).

[0065] The carbon dioxide recovery process (B) may include, for example, a method in which, after performing the carbon dioxide separation process (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.

[0066] In the carbon dioxide recovery process (B), the heating temperature of the carbon dioxide absorbent is 30°C to 150°C, preferably 30°C to 120°C. Generally, the higher the heating temperature, the easier it is for carbon dioxide to be released from the carbon dioxide absorbent that has absorbed it. In the carbon dioxide absorbent of the present invention, carbon dioxide can be released at a temperature of 30°C to 150°C, preferably 30°C to 120°C, and at a temperature equivalent to or higher than the temperature of the carbon dioxide separation process (A). For example, if the carbon dioxide absorbent is the carbon dioxide absorbent of the present invention, carbon dioxide can be released even if the heating temperature is 30°C to 80°C, preferably 30°C to 60°C.

[0067] In the carbon dioxide recovery process (B), the pressure (absolute pressure) is not particularly limited and may be carried out under atmospheric pressure or under reduced pressure. When 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 making it easier to prevent oxidation of the carbon dioxide absorbent, and further preferably 50 kPa or less, particularly 30 kPa or less, from the viewpoint of efficiently desorbing carbon dioxide from the carbon dioxide absorbent.

[0068] In the carbon dioxide separation and recovery method of the present invention, by using the recycled carbon dioxide absorbent obtained in the carbon dioxide recovery step (B) as a carbon dioxide absorbent to which a mixed gas containing carbon dioxide is contacted in the carbon dioxide separation step (A), the carbon dioxide separation step (A) and the carbon dioxide recovery step (B) can be repeated two or more times. For example, when repeating the carbon dioxide separation step (A) and the carbon dioxide recovery step (B) twice, the process is carried out as follows: "carbon dioxide separation step (A) → carbon dioxide recovery step (B) → carbon dioxide separation step (A) → carbon dioxide recovery step (B)". The carbon dioxide separation step (A) and the carbon dioxide recovery step (B) can be repeated as long as the carbon dioxide absorption performance is sustained.

[0069] In the carbon dioxide separation method and carbon dioxide separation and recovery method of the present invention, the carbon dioxide absorbent of the present invention, which contains a phosphine oxide compound represented by general formula (1) that has excellent chemical absorption properties, is used for carbon dioxide absorption, thereby increasing the efficiency of carbon dioxide removal from the mixed gas.

[0070] The carbon dioxide separation method and carbon dioxide separation and recovery method of the present invention are suitably used when separating or recovering carbon dioxide from mixed gases 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 treatment facilities and steel mills, and transportation equipment such as automobiles, aircraft and ships. They are also suitably used when separating or recovering carbon dioxide directly from the atmosphere.

[0071] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[0072] (Example 1-1) Synthesis of Tris(3-(3-aminopropyl)aminopropyl)phosphine oxide In a 1 L four-necked flask equipped with a stirrer and thermometer, 66.4 g (0.3 mol) of Tris(3-aminopropyl)phosphine oxide, 300 ml of pure water, and 197.0 g (0.9 mol) of 3-bromopropylamine hydrobromide were added and heated and stirred at 80-85°C for 6 hours. After cooling, １ ¹H-NMR measurement confirmed that no unreacted tris(3-aminopropyl)phosphine oxide remained. After cooling, 263 g of a slightly yellowish viscous liquid was obtained by concentrating the water under reduced pressure using an evaporator. (Identification data) ３１ P-NMR (D ２ O); 60.28ppm １ H-NMR (D ２ O); 1.75 to 2.10 ppm (m, 18H, -CH ２ -, O=P-CH ２ -), 2.94 to 3.10 ppm (m, 18H, -CH ２ -NH-CH ２ -ien-CH ２ -NH ２ ), 4.61ppm (s, 15H, -NH-, -NH ２(HBr) As a result, it was confirmed to be tris(3-(3-aminopropyl)aminopropyl)phosphine oxide hexahydrobromide. Next, 219.5 g (0.25 mol) of tris(3-(3-aminopropyl)aminopropyl)phosphine oxide hexahydrobromide and 300 ml of pure water were added to a 1 L four-necked flask equipped with a stirrer and thermometer, and 100 ml of 60 g (1.5 mol) aqueous solution of sodium hydroxide was added at room temperature. The water was removed under reduced pressure using an evaporator, 300 ml of isopropyl alcohol was added to the slurry, dehydrated with anhydrous sodium sulfate, and the precipitated sodium bromide was filtered using a Celite filtration aid. By concentrating the isopropyl alcohol solution under reduced pressure, 96.3 g of a slightly yellowish liquid (crude yield 98.1%) was obtained. (Identification data) ３１ P-NMR (D ２ O); 60.83ppm １ H-NMR (D ２ O); 1.50 to 1.63 ppm (m, 12H, -CH ２ -), 1.74 to 1.80 ppm (m, 6H, O=P-CH ２ -), 2.46 to 2.60 ppm (m, 18H, -CH ２ -NH-CH ２ -ien-CH ２ -NH ２ ), 4.70ppm (s, 9H, -NH-, -NH ２ As a result, it was confirmed to be tris(3-(3-aminopropyl)aminopropyl)phosphine oxide.

[0073] (Example 2-1) Synthesis of Tris(3-(3-(3-aminopropyl)aminopropyl)aminopropyl)phosphine oxide: 78.5 g (0.2 mol) of Tris(3-(3-aminopropyl)aminopropyl)phosphine oxide obtained in Example 1, 300 ml of pure water, and 131.4 g (0.6 mol) of 3-bromopropylamine hydrobromide were added to a 1 L four-necked flask equipped with a stirrer and thermometer, and heated and stirred at 80-85°C for 6 hours. After cooling, the water was concentrated under reduced pressure using an evaporator to obtain 209 g of a slightly yellowish viscous liquid. (Identification data) ３１ P-NMR (D ２ O); 60.72ppm １H-NMR (D ２ O); 1.75 to 2.10 ppm (m, 18H, -CH ２ -, O=P-CH ２ -), 2.94 to 3.10 ppm (m, 18H, -CH ２ -NH-CH ２ -ien-CH ２ -NH ２ ), 4.61ppm (s, 15H, -NH-, -NH ２ (HBr) As a result, it was confirmed to be tris(3-(3-(3-aminopropyl)aminopropyl)aminopropyl)phosphine oxide hexahydrobromide. Next, 209 g (0.2 mol) of tris(3-(3-(3-aminopropyl)aminopropyl)aminopropyl)phosphine oxide hexahydrobromide and 300 ml of pure water were added to a 1 L four-necked flask equipped with a stirrer and thermometer, and 100 ml of 48 g (1.2 mol) aqueous solution of sodium hydroxide was added at room temperature. The water was removed under reduced pressure using an evaporator, 300 ml of isopropyl alcohol was added to the slurry, dehydrated with anhydrous sodium sulfate, and the precipitated sodium bromide was filtered using a Celite filtration aid. By concentrating the isopropyl alcohol solution under reduced pressure, 97.0 g of a slightly yellowish liquid (crude yield 96.0%) was obtained. (Identification data) ３１ P-NMR (D ２ O); 60.72ppm １ H-NMR (D ２ O); 1.46 to 1.59 ppm (m, 18H, -CH ２ -), 1.70 to 1.76 ppm (m, 6H, O=P-CH ２ -), 2.33 to 2.60 ppm (m, 30H, -CH ２ -NH-CH ２ -ien-CH ２ -NH ２ ), 4.66ppm (s, 9H, -NH-, -NH ２ As a result, it was confirmed to be tris(3-(3-(3-aminopropyl)aminopropyl)aminopropyl)phosphine oxide.

[0074] (Example 3-1) Synthesis of Tris(3-(3-(3-(3-aminopropyl)aminopropyl)aminopropyl)phosphine oxide: 112.8 g (0.2 mol) of Tris(3-(3-(3-aminopropyl)aminopropyl)aminopropyl)phosphine oxide obtained in Example 2, 300 ml of pure water, and 131.4 g (0.6 mol) of 3-bromopropylamine hydrobromide were added to a 1 L four-necked flask equipped with a stirrer and thermometer, and heated and stirred at 80-85°C for 6 hours. After cooling, the water was concentrated under reduced pressure using an evaporator to obtain 245 g of a slightly yellowish viscous liquid. (Identification data) ３１ P-NMR (D ２ O); 60.76ppm １ H-NMR (D ２ O); 1.77 to 2.11 ppm (m, 18H, -CH ２ -, O=P-CH ２ -), 2.98 to 3.15 ppm (m, 18H, -CH ２ -NH-CH ２ -ien-CH ２ -NH ２ ), 4.60ppm (s, 15H, -NH-, -NH ２ (HBr) As a result, it was confirmed to be tris(3-(3-(3-(3-aminopropyl)aminopropyl)aminopropyl)aminopropyl)phosphine oxide hexahydrobromide. Next, 244 g (0.2 mol) of tris(3-(3-(3-(3-aminopropyl)aminopropyl)aminopropyl)aminopropyl)phosphine oxide hexahydrobromide and 300 ml of pure water were added to a 1 L four-necked flask equipped with a stirrer and thermometer, and 100 ml of 48 g (1.2 mol) aqueous solution of sodium hydroxide was added at room temperature. The water was removed under reduced pressure using an evaporator, 300 ml of isopropyl alcohol was added to the slurry, dehydrated with anhydrous sodium sulfate, and the precipitated sodium bromide was filtered using a Celite filtration aid. By concentrating the isopropyl alcohol solution under reduced pressure, 136.7 g of a slightly yellowish liquid (crude yield 93.0%) was obtained. (Identification data) ３１ P-NMR (D ２ O); 60.75ppm １ H-NMR (D ２O); 1.45 to 1.57 ppm (m, 18H, -CH ２ -), 1.70 to 1.77 ppm (m, 6H, O=P-CH ２ -), 2.31 to 2.62 ppm (m, 30H, -CH ２ -NH-CH ２ -, -CH ２ -NH ２ ), 4.65 ppm (s, 9H, -NH-, -NH ２ ) As a result, it was confirmed that it was tris(3-(3-(3-(3-aminopropyl)aminopropyl)aminopropyl)aminopropyl)phosphine oxide.

[0075] (Example 4-1) Synthesis of tris(3-(2-aminoethyl)aminopropyl)phosphine oxide In a 1 L four-necked flask equipped with a stirrer and a thermometer, 66.4 g (0.3 mol) of tris(3-aminopropyl)phosphine oxide, 300 ml of pure water, and 184.4 g (0.9 mol) of 2-bromoethylamine hydrobromide were added, and the mixture was heated and stirred at 80 to ˚C for 6 hours. After cooling, it was confirmed by H-NMR measurement that no unreacted tris(3-aminopropyl)phosphine oxide remained. After cooling, water was concentrated under reduced pressure using an evaporator to obtain 252 g of a slightly yellow viscous liquid. (Identification data) ３１ P-NMR (D ２ O); 57.33 ppm １ H-NMR (D ２ O); 1.82 to 2.00 ppm (m, 12H, -CH ２ -, O=P-CH ２ -), 3.05 to 3.26 ppm (m, 18H, -CH ２ -NH-CH ２ -, -CH ２ -NH ２ ), 4.66 ppm (s, 15H, -NH-, -NH ２(HBr) As a result, it was confirmed to be tris(3-(2-aminoethyl)aminopropyl)phosphine oxide hexahydrobromide. Next, 209.0 g (0.25 mol) of tris(3-(2-aminoethyl)aminopropyl)phosphine oxide hexahydrobromide and 300 ml of pure water were added to a 1 L four-necked flask equipped with a stirrer and thermometer, and 100 ml of 60 g (1.5 mol) aqueous solution of sodium hydroxide was added at room temperature. The water was removed under reduced pressure using an evaporator, 300 ml of isopropyl alcohol was added to the slurry, dehydrated with anhydrous sodium sulfate, and the precipitated sodium bromide was filtered using a Celite filtration aid. By concentrating the isopropyl alcohol solution under reduced pressure, 84.7 g of a slightly yellowish liquid (crude yield 98.1%) was obtained. (Identification data) ３１ P-NMR (D ２ O); 60.88ppm １ H-NMR (D ２ O); 1.52 to 1.59 ppm (m, 6H, -CH ２ -), 1.73 to 1.79 ppm (m, 6H, O=P-CH ２ -), 2.45 to 2.68 ppm (m, 18H, -CH ２ -NH-CH ２ -ien-CH ２ -NH ２ ), 4.67ppm (s, 9H, -NH-, -NH ２ As a result, it was confirmed to be tris(3-(2-aminoethyl)aminopropyl)phosphine oxide.

[0076] (Reference Example 1-1) A synthetic ion exchange resin of tributyl(3-aminopropyl)phosphonium β-alanine (Organo, Amberlite IRA400J Cl, exchange capacity 1.4 equivalents / resin volume L) was packed into a glass column (inner diameter 65 mmφ × length 500 mm) with 1500 ml of resin. 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, and then pure water was passed through until the effluent became neutral. Next, an aqueous solution of 140.0 g (0.41 mol) of tributyl(3-aminopropyl)phosphonium bromide dissolved in 500 ml of pure water was passed through the column from above at a rate of SV = 1.0, and then 1000 ml of pure water was passed through to obtain 1550 g of an aqueous solution of tributyl(3-aminopropyl)phosphonium hydroxide. The solution was titrated with 1 / 10 N hydrochloric acid titrator, resulting in a concentration of 6.5% and a yield of 89.0%. 500 g (0.12 mol) of the obtained aqueous solution of tributyl(3-aminopropyl)phosphonium hydroxide was dissolved in 10.7 g (0.12 mol) of β-alanine at room temperature. The resulting mixed aqueous solution was concentrated under reduced pressure using an evaporator. The methanol solution, obtained by mixing the concentrate with methanol, was dehydrated overnight with anhydrous magnesium sulfate. The dehydrated methanol solution was then concentrated under reduced pressure using an evaporator to obtain 41.4 g (99.0% crude yield) of a colorless, transparent viscous liquid with a viscosity (25°C) of 288 cP. The NMR identification data for the obtained colorless, transparent viscous liquid is as follows: (Identification Data) ３１ P-NMR; 34.34ppm １ H-NMR; 0.80 ppm (t,9H,-CH ３ ), 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 -), 2.19ppm (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 β-alanine.

[0077] (Reference Example 2-1) Synthesis of Tris(3-aminopropyl)phosphine oxide: In a 1L stainless steel autoclave equipped with a stirrer, thermometer, injection pump, safety valve, and gas inlet pipe, 150ml of toluene and 133g (2.33 mol) of allylamine were charged. The autoclave was purged three times with nitrogen gas and vacuum, and 22g (0.65 mol) of phosphine gas manufactured by Nippon Chemical Industrial Co., Ltd. with a purity of 99.9% was charged. At this time, when the temperature was raised to 80°C using a water bath, the gauge pressure was 0.93 MPa (absolute pressure 1.03 MPa). Next, 1.06g (0.006 mol) of azobisisobutyronitrile was dissolved in 150ml of toluene and injected in stages 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 overnight maturation, the mixture was cooled to room temperature, the remaining gas was evacuated into a removal system, and the system was further purged with nitrogen gas and vacuum. The mixture was then extracted into a reduced-pressure round-bottom flask to obtain 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 remove excess allylamine and toluene. The vacuum and temperature were then increased and the mixture heated further (gauge pressure 0.2 kPa (absolute pressure 101.5 kPa), 160°C). Heating was stopped when the initial distillate began to appear, and the residue was used as the product. After cooling the obtained product to room temperature, it was purged with nitrogen gas to obtain 120 g of a colorless, transparent liquid. The NMR identification data for the obtained colorless, transparent liquid is as follows: (Identification Data) ３１ P-NMR (D ２ O); -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-necked flask equipped with a stirrer and 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 in. 56.1 g (0.495 mol) of 30% hydrogen peroxide diluted with 100 ml of pure water was added dropwise over 1 hour while maintaining the temperature at 70-75°C. After aging for 1 hour, the mixture was 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.

[0078] (Example 1-2) 39.3 g (0.1 mol) of tris(3-(3-aminopropyl)aminopropyl)phosphine oxide obtained in Example 1-1 was dissolved in 300 ml of pure water, and silica gel (CARiACT Q-30 manufactured by Fuji Silicia Chemical Co., Ltd., particle size 1.70-4.00 mm, BET specific surface area 100 m²) was dissolved. ２ 73.0 g of (average pore size 30 nm) was added and allowed to stand at room temperature until moisture permeated the silica gel. By concentrating under reduced pressure in an evaporator and completely removing the added water, 112.9 g of a carbon dioxide absorbent with tris(3-(3-aminopropyl)aminopropyl)phosphine oxide impregnated onto the silica gel was obtained. The impregnation rate of tris(3-(3-aminopropyl)aminopropyl)phosphine oxide relative to the total mass of the carbon dioxide absorbent was 35.0% by mass. The obtained carbon dioxide absorbent was evaluated in carbon dioxide absorption test 1, carbon dioxide absorption test 2, and regeneration test described later.

[0079] (Example 2-2) 57.9 g (0.1 mol) of tris(3-(3-(3-aminopropyl)aminopropyl)aminopropyl)phosphine oxide obtained in Example 2-1 was dissolved in 300 ml of pure water, and silica gel (CARiACT Q-30 manufactured by Fuji Silicia Chemical Co., Ltd., particle size 1.70-4.00 mm, BET specific surface area 100 m²) was added. ２ 107.5 g of (3-(3-(3-aminopropyl)aminopropyl)aminopropyl) phosphine oxide was added and left to stand at room temperature until moisture permeated the silica gel. The mixture was concentrated under reduced pressure using an evaporator, and the added water was completely removed by distillation to obtain 165.9 g of carbon dioxide absorbent with tris(3-(3-(3-aminopropyl)aminopropyl)aminopropyl)phosphine oxide impregnated onto the silica gel. The impregnation rate of tris(3-(3-(3-aminopropyl)aminopropyl)aminopropyl)phosphine oxide relative to the total mass of the carbon dioxide absorbent was 35.0% by 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.

[0080] (Example 3-2) Dissolve 73.5 g (0.1 mol) of tris(3-(3-(3-(3-aminopropyl)aminopropyl)aminopropyl)phosphine oxide obtained in Example 3-1 in 300 ml of pure water, and add silica gel (CARiACT Q-30 manufactured by Fuji Silicia Chemical Co., Ltd., particle size 1.70-4.00 mm, BET specific surface area 100 m²). ２ 136.6 g of (3-(3-(3-aminopropyl)aminopropyl)aminopropyl) was added and left to stand at room temperature until moisture permeated the silica gel. The mixture was concentrated under reduced pressure using an evaporator, and the added water was completely removed by distillation to obtain 212.2 g of carbon dioxide absorbent with tris(3-(3-(3-aminopropyl)aminopropyl)aminopropyl)phosphine oxide impregnated onto the silica gel. The impregnation rate of tris(3-(3-(3-aminopropyl)aminopropyl)aminopropyl)phosphine oxide relative to the total mass of the carbon dioxide absorbent was 35.0% by 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.

[0081] (Example 4-2) 35.0 g (0.1 mol) of tris(3-(2-aminoethyl)aminopropyl)phosphine oxide obtained in Example 4-1 was dissolved in 300 ml of pure water, and silica gel (CARiACT Q-30 manufactured by Fuji Silicia Chemical Co., Ltd., particle size 1.70-4.00 mm, BET specific surface area 100 m²) was dissolved. ２ 65.0 g of (1 / g, average pore size 30 nm) was added and allowed to stand at room temperature until moisture permeated the silica gel. By concentrating under reduced pressure in an evaporator and completely removing the added water, 101.2 g of a carbon dioxide absorbent with tris(3-(2-aminoethyl)aminopropyl)phosphine oxide impregnated onto the silica gel was obtained. The impregnation rate of tris(3-(2-aminoethyl)aminopropyl)phosphine oxide relative to the total mass of the carbon dioxide absorbent was 35.0% by 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.

[0082] (Reference Example 1-2) Dissolve 30.2 g (0.086 mol) of tributyl(3-aminopropyl)phosphonium / β-alanine obtained in Reference Example 1-1 in 300 ml of pure water, and add silica gel (CARiACT Q-30 manufactured by Fuji Silicia Chemical Co., Ltd., particle size 1.70-4.00 mm, BET specific surface area 100 m²). ２ 55.9 g of (1 / g, average pore size 30 nm) was added and allowed to stand at room temperature until moisture permeated the silica gel. By concentrating under reduced pressure in an evaporator and completely removing the added water, 86.3 g of a carbon dioxide absorbent with tributyl(3-aminopropyl)phosphonium-β-alanine impregnated onto silica gel was obtained. The impregnation rate of tributyl(3-aminopropyl)phosphonium-β-alanine relative to the total mass of the carbon dioxide absorbent was 35.0% by 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.

[0083] (Reference Example 2-2) Dissolve 33.2 g (0.15 mol) of tris(3-aminopropyl)phosphine oxide obtained in Reference Example 2-1 in 300 ml of pure water, and add silica gel (CARiACT Q-50 manufactured by Fuji Silicia Chemical Co., Ltd., particle size 1.70-4.00 mm, BET specific surface area 80 m²). ２61.7 g of (1 / g, average pore size 50 nm) was added and left to stand at room temperature until moisture permeated the silica gel. By concentrating under reduced pressure in an evaporator and completely removing the added water, 95.0 g of a carbon dioxide absorbent with tris(3-aminopropyl)phosphine oxide impregnated onto the silica gel was obtained. The impregnation rate of tris(3-aminopropyl)phosphine oxide relative to the total mass of the carbon dioxide absorbent was 35.0% by mass. The obtained carbon dioxide absorbent was evaluated in carbon dioxide absorption test 2 described later.

[0084] (Evaluation) (Carbon Dioxide Absorption Test 1) 90 ml (packing weight shown in Table 1) of the carbon dioxide absorbent obtained in Examples 1-2 to 4-2 and Reference Example 1-2 was packed into a glass column with an inner diameter of 20 mm and a length of 300 mm, and air (room temperature 25°C, average carbon dioxide concentration: 450 ppm) was passed through it 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 meter (TR-76Ui-S, T&D Corporation), and the time until saturation occurred and the carbon dioxide concentration began to rise (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.

[0085]

[0086] The results shown in Table 1 indicate that the carbon dioxide absorbents of Examples 1-2 to 4-2 exhibit superior carbon dioxide absorption performance in an atmospheric environment compared to the carbon dioxide absorbent of Reference Example 1-2.

[0087] (Carbon Dioxide Absorption Test 2) The carbon dioxide absorbents obtained in Examples 1-2 to 4-2 and Reference Example 1-2 were placed in 35 ml Erlenmeyer flasks in the filling weights shown in Table 2. Carbon dioxide gas with a purity of 99.995% was blown in at a flow rate of 200 ml / min at room temperature (25°C). The weight was accurately measured every 10 minutes to a sensitivity of 0.1 mg, and gas blowing was stopped when the weight became constant. 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 carbon dioxide absorbent. The results are shown in Table 2.

[0088]

[0089] The results shown in Table 2 indicate that the carbon dioxide absorbents of Examples 1-2 to 4-2 exhibit superior carbon dioxide absorption performance even at high concentrations compared to the carbon dioxide absorbent of Reference Example 1-2.

[0090] (Regeneration Test 1) The carbon dioxide absorbent obtained in Example 1-2 was placed in a 35 ml Erlenmeyer flask in the filling weight shown in Table 3. Carbon dioxide gas with a purity of 99.995% was blown in at a flow rate of 200 ml / min at room temperature (25°C). The weight was accurately measured to a sensitivity of 0.1 mg every 10 minutes, and the gas blowing was stopped when the weight became constant. 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 from Example 1-2, which had absorbed carbon dioxide to saturation, was transferred to a 50 mm diameter Petri dish, fully vacuumed with a vacuum pump, and heated in a vacuum dryer maintained at 80°C for 1 hour to expel the carbon dioxide and regenerate it. Next, the regenerated carbon dioxide absorbent was placed again in a 35 ml Erlenmeyer flask in the filling weight shown in Table 3, and the amount of carbon dioxide absorbed was determined in the same way as above. This carbon dioxide absorption and regeneration process was repeated 5 times. 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) × 100

[0091]

[0092] The results shown in Table 3 indicate that when carbon dioxide absorbent is heated after the initial carbon dioxide absorption test to remove carbon dioxide, the recycled carbon dioxide absorbent regains its carbon dioxide absorption capacity. This means that even recycled carbon dioxide absorbent exhibits excellent absorption performance and a high regeneration rate, resulting in superior durability.

[0093] (Regeneration Test 2) The carbon dioxide absorbent obtained in Example 1-2 and Reference Example 2-2 was placed in a 35 ml Erlenmeyer flask in the filling weight shown in Table 4. Carbon dioxide gas with a purity of 99.995% was blown in at a flow rate of 200 ml / min at room temperature (25°C), and the weight was accurately measured to a sensitivity of 0.1 mg every 10 minutes. Gas blowing was stopped when the weight became constant. 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 from Example 1-2 and Reference Example 2-2, which had absorbed carbon dioxide to saturation, was transferred to a 50 mm diameter Petri dish, and regeneration was performed by heating it statically in a drying oven maintained at 60°C or 80°C under full vacuum using a vacuum pump or in air for 1 hour to expel the carbon dioxide. The regenerated carbon dioxide absorbent was again placed in a 35 ml Erlenmeyer flask in the filling weight shown in Table 4, and the amount of carbon dioxide absorbed was determined in the same manner as above. 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) × 100

[0094]

[0095] The results shown in Table 4 indicate that the carbon dioxide absorbent of Example 1-2 has a higher regeneration rate even at lower regeneration temperatures compared to the carbon dioxide absorbent of Reference Example 2-2, meaning that it can easily desorb carbon dioxide even at low temperatures. Similarly, it is clear that it has excellent oxidation resistance as there is no change in appearance.

Claims

1. The following general formula (1): (In the formula, a, b, and c represent integers between 1 and 10, and R １ A phosphine oxide compound characterized by being represented by (where represents a primary amino group, a secondary amino group, or a tertiary amino group).

2. In the general formula (1), R １ The phosphine oxide compound according to claim 1, characterized in that the group is a primary amino group.

3. The following general formula (1): (In the formula, a, b, and c represent integers between 1 and 10, and R １ A compound for carbon dioxide absorbers characterized by being a phosphine oxide compound represented by (where represents a primary amino group, a secondary amino group, or a tertiary amino group).

4. A carbon dioxide absorbent characterized by containing the carbon dioxide absorbent compound described in claim 3.

5. A carbon dioxide absorbent characterized in that the carbon dioxide absorbent compound described in claim 3 is supported on a porous carrier.

6. The carbon dioxide absorbent according to claim 5, characterized in that 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 structure, porous alumina, porous ceramic, porous concrete, activated clay, or clay mineral.

7. A method for separating carbon dioxide, characterized by comprising a carbon dioxide separation step of contacting a carbon dioxide absorbent described in claim 5 with a mixed gas containing carbon dioxide, thereby allowing the carbon dioxide absorbent to absorb the carbon dioxide in the mixed gas and separating the carbon dioxide from the mixed gas.

8. A carbon dioxide separation and recovery method characterized by comprising: a carbon dioxide separation step of contacting a carbon dioxide absorbent described in claim 5 with a mixed gas containing carbon dioxide, thereby separating carbon dioxide from the mixed gas by allowing the carbon dioxide absorbent to absorb the carbon dioxide in 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 to 150°C, 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 recovery method according to claim 8, characterized in that the recycled carbon dioxide absorbent obtained by the carbon dioxide recovery step is used as the carbon dioxide absorbent to which the mixed gas containing carbon dioxide is brought into contact in the carbon dioxide separation step, thereby repeating the carbon dioxide separation step and the carbon dioxide recovery step two or more times.

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

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

12. The apparatus according to claim 10, characterized in that it is a DAC device.

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