Amine compound, amine composition, carbon dioxide absorbent, method for recovering carbon dioxide, and carbon dioxide separation and recovery device

Abstract

Provided are an amine compound represented by general formula (1), an amine composition containing the amine compound, a carbon dioxide absorbent containing the amine compound and the amine composition, a method for recovering carbon dioxide using the carbon dioxide absorbent, and a carbon dioxide separation and recovery device. In formula (1), R1 is a hydroxy group or an organic group having 1-10 carbon atoms. Symbols n1-n4 are each independently a number of 3-8, and m1 and m2 are each independently a number of 1 or 2.

Description

Amine compound, amine composition, carbon dioxide absorbent, carbon dioxide recovery method, and carbon dioxide separation and recovery device

[0001] The present invention relates to an amine compound, an amine composition, a carbon dioxide absorbent, a method for recovering carbon dioxide, and a carbon dioxide separation and recovery apparatus.

[0002] In light of the issue of global warming, there is a need to reduce carbon dioxide emissions. One method for reducing carbon dioxide emissions is to capture carbon dioxide using a carbon dioxide absorbent. A typical carbon dioxide absorbent is an aqueous solution of an amine compound, such as monoethanolamine. Aqueous solutions of amine compounds have the characteristic of not releasing the absorbed carbon dioxide unless the temperature is elevated, for example, to 120°C or higher. Raising the carbon dioxide release temperature above the boiling point of water requires a large amount of energy to capture the carbon dioxide due to the high latent heat and specific heat of water. As described above, one challenge with conventional carbon dioxide absorbents is further energy conservation during carbon dioxide separation and capture. Furthermore, conventional carbon dioxide absorbents suffer from the problem of volatilization loss of a small amount of the amine compound when contacted with gas during the carbon dioxide absorption process. Therefore, reducing the volatility of the amine compound contained in the carbon dioxide absorbent is also an issue. Furthermore, conventional chemical absorption methods involve steam heating to temperatures of approximately 110°C to 130°C to boil the carbon dioxide absorbent and regenerate it. Therefore, this method requires a significant amount of thermal energy. Furthermore, there is a concern that the amine compound contained in the carbon dioxide absorbent may be thermally decomposed during this regeneration process, and therefore the thermal stability of the carbon dioxide absorbent is also an issue.

[0003] In recent years, carbon dioxide absorbents in which an amine compound is supported on a porous material have been studied. By supporting an amine compound on a porous material and solidifying it, it becomes possible to recover carbon dioxide with less energy than with an aqueous solution, which has problems with high latent heat and specific heat. Examples of technologies related to such solidified carbon dioxide absorbents include those described in Patent Documents 1 to 3.

[0004] Patent Document 1 describes a solid absorbent for separating and capturing carbon dioxide, which contains a specific alkanolamine and is supported on a support. Patent Document 2 describes a carbon dioxide absorbent in which an amine compound is supported on porous particles in which hydrophilic fibers and porous powder are combined with a hydrophilic binder. Patent Document 3 describes a carbon dioxide absorption composition containing polyethylene polyamine, phosphoric acid and / or a phosphate salt, and silica.

[0005] JP 2012-139622 A JP 2018-187574 A JP 2020-58966 A

[0006] However, according to studies by the present inventors, there is room for improvement in terms of repeated usability of carbon dioxide absorbents containing an amine compound and a porous material as described in Patent Documents 1 to 3. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an amine compound that, when used as a carbon dioxide absorbent, has good carbon dioxide absorption properties and is particularly excellent in repeated usability, an amine composition containing the amine compound, a carbon dioxide absorbent containing these, a method for capturing carbon dioxide using the carbon dioxide absorbent, and a carbon dioxide separation and capture apparatus.

[0007] The present inventors have found that the above problems can be solved by a novel amine compound having a specific structure. That is, the present invention relates to the following: [1] An amine compound represented by the following general formula (1): In formula (1), R 1is a hydroxy group or an organic group having 1 to 10 carbon atoms. n1 to n4 each independently represent a number from 3 to 8, and m1 and m2 each independently represent a number of 1 or 2. [2] The amine compound according to [1], wherein n1 to n4 are all 3 in general formula (1). [3] An amine composition containing the amine compound according to [1] or [2]. [4] A carbon dioxide absorbent containing the amine compound according to [1] or [2], or the amine composition according to [3]. [5] The carbon dioxide absorbent according to [4], further comprising a porous material. [6] The carbon dioxide absorbent according to [5], wherein the porous material comprises at least one selected from the group consisting of porous silica and porous alumina. [7] The carbon dioxide absorbent according to [6], wherein the porous material is in a particulate form. [8] The volume median particle diameter (D ５０ [9] The carbon dioxide absorbent according to [7], wherein the specific surface area of ​​the porous material measured by the BET method is 2 m ２ / g or more 3000m ２

[10] The carbon dioxide absorbent according to any one of [5] to [8], wherein the pore volume of the porous material is 0.1 cm ３ / g or more 5.0cm ３ / g or less.

[11] The carbon dioxide absorbent according to any one of [5] to

[10] , wherein the content of the amine compound represented by general formula (1) in the carbon dioxide absorbent is 0.1 parts by mass or more and 1,000 parts by mass or less per 100 parts by mass of the porous material.

[12] A method for recovering carbon dioxide, using the carbon dioxide absorbent according to any one of [4] to

[11] .

[13] The method according to

[12] , wherein the method comprises an absorption step of bringing the carbon dioxide absorbent into contact with a gas containing carbon dioxide to absorb carbon dioxide into the carbon dioxide absorbent, and a desorption step of desorbing carbon dioxide from the carbon dioxide absorbent that has absorbed carbon dioxide in the absorption step, and the desorption step comprises at least one step selected from the group consisting of the following (I) to (III): (I) a step of subjecting the carbon dioxide absorbent that has absorbed carbon dioxide to reduced pressure conditions; (II) a step of bringing an inert gas that does not contain carbon dioxide into contact with the carbon dioxide absorbent that has absorbed carbon dioxide; and (III) a step of heating the carbon dioxide absorbent that has absorbed carbon dioxide.

[14] A carbon dioxide separation and capture system comprising: an absorption device equipped with a mechanism that brings the carbon dioxide absorbent according to any one of [4] to

[11] into contact with a gas containing carbon dioxide, thereby causing the carbon dioxide absorbent to absorb carbon dioxide; and a desorption device equipped with a mechanism that desorbs carbon dioxide from the carbon dioxide absorbent that has absorbed carbon dioxide.

[0008] According to the present invention, it is possible to provide an amine compound that, when used as a carbon dioxide absorbent, has good carbon dioxide absorbency and is particularly excellent in repeated use ability; an amine composition containing the amine compound; a carbon dioxide absorbent containing any of them; a method for recovering carbon dioxide using the carbon dioxide absorbent; and a carbon dioxide separation and recovery apparatus.

[0009] 1 is a schematic diagram showing one embodiment of a carbon dioxide separation and capture apparatus of the present invention.

[0010] [Definitions] In this specification, "good carbon dioxide absorbency" means that the amount of carbon dioxide absorbed when contacted with a gas containing carbon dioxide is large, and "good carbon dioxide absorbency from air" means that the amount of carbon dioxide absorbed is large for a low concentration (about 0.04% by volume) of carbon dioxide in the air. In this specification, "good reusability" of a carbon dioxide absorbent means that the retention rate of the carbon dioxide absorption rate is high when a cycle test of carbon dioxide absorption and desorption is conducted. The carbon dioxide absorption rate and its retention rate can be specifically evaluated by the method described in the Examples. A "primary amino group" is an amino group having two hydrogen atoms on a nitrogen atom, i.e., -NH ２ In this specification, the expression "XX to YY" means "XX or more and YY or less."

[0011] [Amine Compound] The amine compound of the present invention is a compound represented by the following general formula (1). In formula (1), R 1 is a hydroxy group or an organic group having 1 to 10 carbon atoms. n1 to n4 each independently represent a number from 3 to 8, and m1 and m2 each independently represent a number of 1 or 2. Because the amine compound of the present invention has the above structure, when used as a carbon dioxide absorbent, it has good carbon dioxide absorbency and is particularly excellent in terms of repeated use.

[0012] The reason why the amine compound of the present invention exhibits the above-mentioned effects is unclear, but is thought to be as follows. In the amine compound of the present invention, the number of methylene groups in the divalent group adjacent to the nitrogen atom (n1 to n4 in general formula (1)) is 3 or more. Amine compounds having two methylene groups (i.e., ethylene groups) are prone to undergo intramolecular cyclization reactions when oxidized, heated, or the like. Therefore, for example, if the amine compound is allowed to absorb carbon dioxide and then subjected to heat treatment to desorb the carbon dioxide, an intramolecular cyclization reaction occurs, converting the compound to a different compound, and reducing its reusability. In contrast, the amine compound of the present invention has a structure that makes the cyclization reaction less likely to occur, and therefore is thought to have good reusability. Furthermore, since the amine compound of the present invention has a relatively high molecular weight, it is unlikely to volatilize even when subjected to heat treatment to desorb carbon dioxide after absorbing carbon dioxide. Furthermore, the amine compound of the present invention has a tertiary amino group in its molecule, and the proportion of tertiary amino groups among all amino groups is high. It is believed that the tertiary amino group does not form a carbamate with strong bonding strength when absorbing carbon dioxide, and is therefore likely to act as a carbon dioxide mediator, thereby reducing the energy required to desorb carbon dioxide. For the above reasons, it is believed that the carbon dioxide absorbent containing the amine compound of the present invention will have good reusability. Furthermore, since the amine compound of the present invention has a primary amino group with a high carbon dioxide absorption rate, it exhibits high carbon dioxide absorbency, and is therefore believed to be able to achieve both carbon dioxide absorbency and reusability.

[0013] In formula (1), R 1 is a hydroxy group or an organic group having 1 to 10 carbon atoms, preferably a hydroxy group, or a hydrocarbon group having 1 to 10 carbon atoms which may have a hydroxy group, an amino group, a halogen atom, a thiol group, a nitro group, a cyano group, or a carboxy group. Preferred examples of the hydrocarbon group include an alkyl group, an aryl group, and an aralkyl group, and more preferably an alkyl group. From the viewpoint of improving carbon dioxide absorption by increasing the amino group concentration, R 1is preferably a hydroxy group, or a hydrocarbon group of 1 to 6 carbon atoms which may have a hydroxy group, an amino group, or a cyano group, more preferably a hydroxy group, or an alkyl group of 1 to 4 carbon atoms which may have a hydroxy group, an amino group, or a cyano group, even more preferably an alkyl group of 1 to 2 carbon atoms which may have a hydroxy group, an amino group, or a cyano group, and still more preferably a methyl group.

[0014] In formula (1), n1 to n4 each independently represent a number from 3 to 8, and from the viewpoint of increasing the amino group concentration and improving carbon dioxide absorbency, and from the viewpoint of improving repeated use when used as a carbon dioxide absorbent, n1 to n4 are preferably 3 to 6, more preferably 3 to 4, and even more preferably all 3. n1 to n4 may be the same or different, but are preferably all the same. Furthermore, from the viewpoint of ease of production, it is preferable that at least n1 and n4 are 3.

[0015] In formula (1), m1 and m2 each independently represent the number 1 or 2. From the viewpoint of ease of production of the amine compound, it is preferable that both m1 and m2 are 1, and from the viewpoint of improving the carbon dioxide absorption ability and repeated use when used as a carbon dioxide absorbent, it is preferable that both m1 and m2 are 2.

[0016] The total amine value of the amine compound of the present invention is preferably 600 mgKOH / g or more, more preferably 800 mgKOH / g or more, even more preferably 1,000 mgKOH / g or more, and preferably 1,200 mgKOH / g or less, from the viewpoint of improving carbon dioxide absorption. Furthermore, the tertiary amine value of the amine compound of the present invention is preferably 100 mgKOH / g or more, more preferably 200 mgKOH / g or more, and preferably 500 mgKOH / g or less, from the viewpoint of further improving carbon dioxide desorption and reusability. The total amine value indicates the amount of all amino groups in the compound, and refers to the amount (mg) of potassium hydroxide (KOH) equivalent to the amount of acid required to neutralize 1 g of the compound. The tertiary amine value indicates the amount of tertiary amino groups in the compound, and refers to the amount (mg) of potassium hydroxide (KOH) equivalent to the amount of acid required to neutralize the tertiary amino groups in 1 g of the compound. The total amine value and tertiary amine value can be specifically determined by the methods described in the Examples.

[0017] From the viewpoint of improving the reusability when used as a carbon dioxide absorbent, the amine compound of the present invention preferably has a proportion of tertiary amino groups in all amino groups of 20 mol% or more, and from the viewpoint of improving carbon dioxide absorbency, it is preferably 80 mol% or less, more preferably 70 mol% or less, even more preferably 60 mol% or less, still more preferably 50 mol% or less, and still more preferably 45 mol% or less. The proportion of tertiary amino groups in all amino groups is the value obtained by dividing the tertiary amine value of the amine compound by the total amine value (tertiary amine value / total amine value).

[0018] Furthermore, from the viewpoint of improving carbon dioxide absorption ability when used as a carbon dioxide absorbent, the amine compound of the present invention preferably has a proportion of primary amino groups among all amino groups of 10 mol% or more, more preferably 15 mol% or more, even more preferably 20 mol% or more, and still more preferably 30 mol% or more. Furthermore, from the viewpoint of repeated use and improving carbon dioxide desorption ability when used as a carbon dioxide absorbent, the proportion of primary amino groups among all amino groups is preferably 70 mol% or less, more preferably 60 mol% or less. The proportion of primary amino groups among all amino groups is the value obtained by dividing the primary amine value of the amine compound by the total amine value (primary amine value / total amine value).

[0019] Specific preferred examples of the amine compound of the present invention are shown below, but are not limited to these.

[0020] Among the above, from the viewpoints of improving carbon dioxide absorption and repeated use when used as a carbon dioxide absorbent, and of ease of production, the amine compound of the present invention is preferably at least one selected from the group consisting of compounds represented by the above structural formulas (1-1), (1-5) and (1-9), and more preferably at least one selected from the group consisting of compounds represented by the above structural formulas (1-1) and (1-9).

[0021] The molecular weight of the amine compound is preferably 250 or more from the viewpoint of suppressing weight loss due to heating when carbon dioxide is desorbed and further improving reusability, and is preferably 800 or less, more preferably 600 or less, and even more preferably 500 or less from the viewpoint of improving carbon dioxide absorbency.

[0022] <Method for Producing Amine Compound> The amine compound of the present invention can be obtained, for example, by performing an addition reaction between a starting amine represented by the following general formula (2) and an unsaturated nitrile compound represented by the following general formula (3), and then reducing the addition reaction product. In formula (2), R 1 , n2, and n3 are the same as above. CH ２ =CH-(CH ２ ) ｎ５-CN (3) In formula (3), n5 is a number from 0 to 5.

[0023] In the production of the amine compound represented by the structural formula (1-1), (1-5), or (1-9), methyliminobis(propylamine) [N,N-bis(3-aminopropyl)methylamine] can be used as the raw material amine represented by the general formula (2), and acrylonitrile can be used as the unsaturated nitrile compound represented by the general formula (3).

[0024] In the addition reaction between the starting amine represented by the general formula (2) and the unsaturated nitrile compound represented by the general formula (3), from the viewpoint of obtaining the amine compound represented by the general formula (1) in high yield, the unsaturated nitrile compound represented by the general formula (3) is preferably reacted in an amount of 2.0 to 30 moles, more preferably 2.0 to 20 moles, per 1.0 mole of the starting amine represented by the general formula (2). When producing a compound in which m1 = m2 = 1 in the general formula (1) (hereinafter, this compound may be referred to as a "2-adduct"), the unsaturated nitrile compound represented by the general formula (3) is preferably reacted in an amount of 2.0 to 10 moles, even more preferably 2.0 to 5.0 moles, and even more preferably 2.0 to 2.8 moles, per 1.0 mole of the starting amine represented by the general formula (2). When a compound in which m1 = m2 = 2 in the general formula (1) is produced (hereinafter, the compound may be referred to as a "tetraadduct"), the unsaturated nitrile compound represented by the general formula (3) is reacted in an amount of preferably 4.0 to 20 moles, and even more preferably 5.0 to 20 moles, with 1.0 mole of the starting material amine represented by the general formula (2).

[0025] The addition reaction is preferably carried out in a solvent from the viewpoint of adjusting the reaction rate. The solvent is preferably at least one selected from the group consisting of water, alcoholic solvents, etheric solvents, ketone solvents, and ester solvents, more preferably at least one selected from the group consisting of water and alcoholic solvents, and even more preferably at least one selected from the group consisting of water, ethanol, and isopropyl alcohol, from the viewpoint of dissolving the starting amine and the unsaturated nitrile compound and of easily removing the solvent after the reaction.

[0026] In the addition reaction, the unsaturated nitrile compound is preferably added dropwise to a mixture of the starting amine and a solvent, and the reaction is carried out under heated conditions. The unsaturated nitrile compound can also be added in multiple batches. In addition, the addition reaction is preferably carried out under a stream of an inert gas such as nitrogen or argon, from the viewpoint of suppressing side reactions.

[0027] The reaction temperature during the addition reaction is preferably 40 to 100° C., more preferably 45 to 90° C., from the viewpoint of improving the reaction efficiency and suppressing side reactions. The reaction time during the addition reaction is not particularly limited, but is preferably 1 to 36 hours, more preferably 2 to 30 hours, after the end of the dropwise addition of the unsaturated nitrile compound, from the viewpoint of improving the reaction conversion rate and production efficiency.

[0028] After the addition reaction is completed, the solvent is removed from the reaction mixture to obtain an addition reaction product. The addition reaction product is then reduced to reduce the nitrile group in the addition reaction product, thereby obtaining the amine compound or amine composition of the present invention. The reduction of the addition reaction product is preferably carried out by hydrogenation (hydrogenation) under heated and pressurized conditions in the presence of a catalyst. Examples of the catalyst include known hydrogenation catalysts, such as supported heterogeneous hydrogenation catalysts in which metals such as Ni, Pt, Pd, and Ru are supported on carbon, silica, alumina, diatomaceous earth, etc.; so-called Ziegler-type hydrogenation catalysts that use organic acid salts of Ni, Co, Fe, Cr, etc. or transition metal salts such as acetylacetonates with a reducing agent such as organoaluminum; and homogeneous hydrogenation catalysts such as so-called organometallic complexes of organometallic compounds such as Ti, Ru, Rh, and Zr.

[0029] The temperature during the hydrogenation reaction is preferably 0 to 200°C, more preferably 10 to 150°C, and even more preferably 20 to 100°C, from the viewpoint of improving the reaction efficiency and suppressing side reactions. The pressure during the hydrogenation reaction is preferably 0.1 MPaG or more, more preferably 0.5 MPaG or more, and even more preferably 1 MPaG or more, from the viewpoint of improving the reaction efficiency and suppressing side reactions, and is preferably 10 MPaG or less, and more preferably 5 MPaG or less. The hydrogenation reaction time is not particularly limited, but is preferably 3 minutes or more, more preferably 10 minutes or more, and even more preferably 30 minutes or more, and is preferably 24 hours or less, more preferably 12 hours or less, and even more preferably 8 hours or less.

[0030] The hydrogenation reaction may be carried out in a solvent, such as the solvents exemplified for the addition reaction, and preferably at least one selected from the group consisting of ethanol and isopropyl alcohol.

[0031] After the hydrogenation reaction, the catalyst is removed from the resulting reaction mixture, and if necessary, purification by distillation or the like is carried out to obtain the amine compound of the present invention.

[0032] [Amine Composition] The amine composition of the present invention contains an amine compound represented by the general formula (1) above. The amine composition of the present invention may take the form of, for example, [1] a composition containing two or more different types of amine compounds represented by the general formula (1) above, or [2] a composition containing the amine compound represented by the general formula (1) above, and unreacted raw materials for the amine compound (the raw material amine represented by the general formula (2) above and the unsaturated nitrile compound represented by the general formula (3) above), by-products, etc.

[0033] Examples of the amine composition of the form [1] include a composition containing at least two of a compound (di-adduct) in which m1 = m2 = 1 in the general formula (1), a compound (hereinafter, also referred to as a "tri-adduct") in which one of m1 and m2 is 1 and the other is 2, and a compound (tetra-adduct) in which m1 = m2 = 2. Examples of the amine composition of the form [2] include a composition containing one amine compound represented by the general formula (1) and unreacted raw materials, by-products, etc. of the amine compound; and a composition containing two or more amine compounds represented by the general formula (1) and unreacted raw materials, by-products, etc. of the amine compound. The amine composition of the form [1] can be obtained, for example, by mixing two or more amine compounds that have been individually produced. Furthermore, as the amine composition of the form [1] or [2], a crude product obtained in the production process of the amine compound represented by the general formula (1) can also be used as the amine composition as is.

[0034] From the viewpoint of improving the reusability when used as a carbon dioxide absorbent, the content of the amine compound represented by the general formula (1) in the amine composition is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, still more preferably 80% by mass or more, still more preferably 90% by mass or more, and still more preferably 95% by mass or more, but is 100% by mass or less.

[0035] From the viewpoint of improving carbon dioxide absorption, the total amine value of the amine composition of the present invention is preferably 600 mgKOH / g or more, more preferably 800 mgKOH / g or more, even more preferably 1,000 mgKOH / g or more, and preferably 1,200 mgKOH / g or less. From the viewpoint of further improving carbon dioxide desorption property and repeated use, the tertiary amine value of the amine composition of the present invention is preferably 100 mgKOH / g or more, more preferably 200 mgKOH / g or more, and preferably 500 mgKOH / g or less. The total amine value and tertiary amine value of the amine composition can be determined by the same method as above.

[0036] In the amine composition of the present invention, from the viewpoint of improving the reusability when used as a carbon dioxide absorbent, the proportion of tertiary amino groups in all amino groups is preferably 20 mol% or more, and from the viewpoint of improving carbon dioxide absorbency, it is preferably 80 mol% or less, more preferably 70 mol% or less, even more preferably 60 mol% or less, still more preferably 50 mol% or less, and still more preferably 45 mol% or less. The proportion of tertiary amino groups in all amino groups is the value obtained by dividing the tertiary amine value of the amine composition by the total amine value (tertiary amine value / total amine value).

[0037] Furthermore, from the viewpoint of improving carbon dioxide absorption ability when used as a carbon dioxide absorbent, the amine composition of the present invention preferably has a proportion of primary amino groups among all amino groups of 10 mol% or more, more preferably 15 mol% or more, even more preferably 20 mol% or more, and even more preferably 30 mol% or more. Furthermore, from the viewpoint of repeated use and improving carbon dioxide desorption ability when used as a carbon dioxide absorbent, the proportion of primary amino groups among all amino groups is preferably 70 mol% or less, more preferably 60 mol% or less. The proportion of primary amino groups among all amino groups is the value obtained by dividing the primary amine value of the amine composition by the total amine value (primary amine value / total amine value).

[0038] <Physical Properties of Amine Compound or Amine Composition> The maximum carbon dioxide dissociation temperature of the amine compound or amine composition, measured by the following method, is preferably 140°C or lower, more preferably 130°C or lower, even more preferably 120°C or lower, even more preferably 110°C or lower, and even more preferably 105°C or lower, from the viewpoint of further improving carbon dioxide desorption properties and reusability. The lower limit of the maximum carbon dioxide dissociation temperature is not particularly limited, but is, for example, 40°C or higher. (Method) The amine compound or amine composition having absorbed carbon dioxide is heated from 23°C to 250°C at a temperature increase rate of 10°C / min, and the temperature at which the amount of heat absorbed due to carbon dioxide desorption becomes maximum is measured, and this temperature is defined as the maximum carbon dioxide dissociation temperature. Here, the amine compound or amine composition having absorbed carbon dioxide can be prepared, for example, by leaving 5 mmol of the amine compound or amine composition in air at 23°C and 50% RH for 24 hours.

[0039] The maximum endothermic temperature of the amine compound or amine composition, measured by the following method, is preferably 150° C. or higher, more preferably 180° C. or higher, even more preferably 200° C. or higher, and still more preferably 250° C. or higher, from the viewpoints of suppressing weight loss due to heating when carbon dioxide is desorbed and further improving reusability. (Method) The amine compound or amine composition is heated from 23° C. to 350° C. at a temperature increase rate of 10° C. / min, and the temperature at which the amount of heat absorbed due to the volatilization of the amine compound or amine composition becomes maximum is measured, and this temperature is defined as the maximum endothermic temperature of the amine compound or amine composition.

[0040] [Carbon dioxide absorbent] The carbon dioxide absorbent of the present invention contains the amine compound represented by the general formula (1) or the amine composition. From the viewpoint of improving carbon dioxide absorbency and repeated usability, the content of the amine compound or the amine composition in the carbon dioxide absorbent is preferably 30% by mass or more, more preferably 40% by mass or more, and even more preferably 50% by mass or more, and 100% by mass or less.

[0041] The carbon dioxide absorbent of the present invention may be a carbon dioxide absorbent consisting solely of the amine compound represented by the general formula (1) or the amine composition. From the viewpoint of enabling separation and recovery of carbon dioxide with less energy, the carbon dioxide absorbent of the present invention preferably further contains a porous material in addition to the amine compound or the amine composition.

[0042] From the viewpoint of enabling separation and recovery of carbon dioxide with less energy, the carbon dioxide absorbent of the present invention preferably has at least a part of the amine compound or the amine composition supported on a porous material, and more preferably has the amine compound or the amine composition supported on a porous material and solidified. Hereinafter, a carbon dioxide absorbent in which the amine compound or the amine composition is supported on a porous material and solidified is also referred to as a "solid carbon dioxide absorbent."

[0043] The porous material is preferably one that can support the amine compound or the amine composition and can withstand the conditions for carbon dioxide recovery, and examples thereof include porous silica, porous alumina, porous silica-alumina, porous magnesia, porous zirconia, zeolite, zeolite-related compounds, clay minerals, natural minerals, activated carbon, carbon molecular sieves (porous carbon), porous resins (synthetic adsorbents), porous metal-organic frameworks, and porous solid waste, and one or more of these can be used. Among these, from the viewpoints of improving carbon dioxide absorption capacity and reusability, the porous material preferably contains at least one selected from the group consisting of porous silica and porous alumina, more preferably contains porous silica, and even more preferably contains mesoporous silica.

[0044] The shape of the porous material is not particularly limited, but is preferably particulate, more preferably spherical. When the porous material is particulate, the specific surface area of ​​the porous material is increased, and the amount of the amine compound or amine composition supported can be increased. This can further improve the carbon dioxide absorption amount.

[0045] When the porous material is particulate, the volume median particle diameter (D ５０ From the viewpoint of improving handleability, the thickness is preferably 1 μm or more, more preferably 5 μm or more, and even more preferably 10 μm or more. From the viewpoint of further increasing the amount of the amine compound or amine composition supported, the thickness is preferably 500 μm or less, more preferably 300 μm or less, even more preferably 200 μm or less, still more preferably 180 μm or less, and still more preferably 160 μm or less.

[0046] The specific surface area of ​​the porous material measured by the BET method is preferably 2 m or more from the viewpoint of further improving the amount of the amine compound or the amine composition supported. ２ / g or more, more preferably 10m ２ / g or more, more preferably 100m ２ / g or more, more preferably 200m ２ / g or more, and even more preferably 400m ２ / g or more, and even more preferably 600m ２ / g or more, and from the viewpoint of improving the handling property, it is preferably 3000m ２ / g or less, more preferably 1500m ２ / g or less, more preferably 1200m ２ / g or less, and even more preferably 1000m ２ / g or less.

[0047] The pore volume of the porous material is preferably 0.1 cm3 or less, from the viewpoint of further improving the amount of the amine compound or the amine composition supported. ３ / g or more, more preferably 0.3 cm ３ / g or more, more preferably 0.5 cm ３ / g or more, and from the viewpoint of improving repetitive use, it is preferably 5.0 cm ３ / g or less, more preferably 3.0 cm ３ / g or less, more preferably 2.5 cm ３ / g or less.

[0048] The specific surface area and pore volume of the porous material can be measured, for example, using a constant volume method with a specific surface area / pore size distribution measuring device (e.g., "ASAP2020" manufactured by Shimadzu Corporation). A more specific gas adsorption measurement method using a specific surface area / pore size distribution measuring device involves, for example, pretreating the sample by heating and evacuating, and then placing 0.1 g of the measurement sample in a sample tube. The sample is then heated to 40°C and evacuated for 6 hours, after which it is cooled to room temperature and the sample mass is measured. The liquid nitrogen temperature is set and the pressure range is specified for measurement, and the specific surface area, pore volume, and pore size can be analyzed and calculated from the resulting nitrogen adsorption isotherm.

[0049] The porous material may be a granulated product such as pellets or tablets obtained by granulating the particulate porous material by a known method. Examples of the granulation method include a dry granulation method using a compression molding machine and a wet granulation method using a binder. By granulating and using the particulate porous material, vibration resistance and abrasion resistance can be imparted, and physical stability can be improved.

[0050] When the carbon dioxide absorbent contains a porous material, from the viewpoint of further improving the carbon dioxide absorbency and the reusability, the content of the amine compound or amine composition in the carbon dioxide absorbent is preferably 0.1 part by mass or more, more preferably 1 part by mass or more, even more preferably 10 parts by mass or more, still more preferably 25 parts by mass or more, and still more preferably 50 parts by mass or more, relative to 100 parts by mass of the porous material. Also, it is preferably 1000 parts by mass or less, more preferably 500 parts by mass or less, still more preferably 250 parts by mass or less, still more preferably 200 parts by mass or less, and still more preferably 150 parts by mass or less.

[0051] When the carbon dioxide absorbent contains a porous material, the total content of the amine compound, the amine composition, and the porous material in the carbon dioxide absorbent is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, still more preferably 90% by mass or more, still more preferably 95% by mass or more, and still more preferably 98% by mass or more, but is 100% by mass or less, from the viewpoint of further improving the carbon dioxide absorbency and the reusability.

[0052] <Other Components> The carbon dioxide absorbent of the present invention can appropriately contain components other than the amine compound, amine composition, and porous material, within a range that does not impair the effects of the invention. Examples of such components include amine components other than the amine compound and amine composition, deterioration inhibitors, antifoaming agents, antioxidants, desiccants for removing moisture (magnesium sulfate, molecular sieves, etc.), etc.

[0053] From the viewpoint of further improving the carbon dioxide absorbency and the reusability, the content of the amine compound and amine composition of the present invention in all amine components contained in the carbon dioxide absorbent is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, still more preferably 80% by mass or more, still more preferably 90% by mass or more, still more preferably 95% by mass or more, and still more preferably 98% by mass or more, but is 100% by mass or less.

[0054] From the viewpoint of further improving carbon dioxide absorbency and reusability, the water content in the carbon dioxide absorbent is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 1% by mass or less, still more preferably 0.5% by mass or less, still more preferably 0.1% by mass or less, and even more preferably 0.01% by mass or less, and it is even more preferable that the carbon dioxide absorbent is substantially free of water. Here, "substantially free of water" means that water is not intentionally added, and does not exclude the presence of a small amount of water as an impurity.

[0055] The method for preparing a carbon dioxide absorbent containing a porous material is not particularly limited, and known methods can be used. For example, it can be prepared by blending the amine compound or amine composition and the porous material and mixing them using a known device. In an embodiment in which at least a portion of the amine compound or amine composition is supported on a porous material, the carbon dioxide absorbent can preferably be prepared by the following method. First, the amine compound or amine composition, the porous material, and an organic solvent are blended and stirred, preferably at a temperature of 5 to 60°C for 1 to 24 hours to prepare a mixture. Next, the organic solvent is removed from the resulting mixture by distillation or the like, and the remaining solids are dried under reduced pressure to obtain a carbon dioxide absorbent. From the viewpoints of dispersibility of the amine compound, amine composition, and porous material, and ease of removal from the carbon dioxide absorbent, the organic solvent is preferably a monohydric alcohol having 4 or less carbon atoms, more preferably at least one selected from the group consisting of methanol, ethanol, and isopropyl alcohol.

[0056] The carbon dioxide absorbent of the present invention has a good ability to absorb carbon dioxide from air, and therefore can be suitably used in a technology for directly absorbing carbon dioxide from air (DAC). Furthermore, the carbon dioxide absorbent of the present invention can be suitably used, for example, when recovering carbon dioxide at a low concentration of 0.01% by volume or more and 1% by volume or less.

[0057] The carbon dioxide absorbent of the present invention is particularly suitable for repeated use, and maintains a high rate of carbon dioxide absorption even after repeated cycles of carbon dioxide absorption and desorption. While it is preferable for a carbon dioxide absorbent to have a high initial carbon dioxide absorption rate, if the rate of carbon dioxide absorption is low after repeated use, the carbon dioxide absorbent will need to be replaced and discarded many times, which is industrially disadvantageous. Therefore, a carbon dioxide absorbent with good repeated use properties can be said to have high industrial applicability.

[0058] [Method for recovering carbon dioxide] The method for recovering carbon dioxide of the present invention (hereinafter also simply referred to as "the method of the present invention") is characterized by using the carbon dioxide absorbent. According to the method of the present invention, the amount of carbon dioxide absorbed from a gas containing carbon dioxide can be improved. Furthermore, carbon dioxide can be separated and recovered with less energy, and the carbon dioxide absorbent has good reusability.

[0059] The carbon dioxide recovery method of the present invention preferably includes a step (absorption step) of contacting the carbon dioxide absorbent with a gas containing carbon dioxide to allow the carbon dioxide absorbent to absorb carbon dioxide.

[0060] <Absorption Step> The absorption step is a step of bringing the carbon dioxide absorbent into contact with a gas containing carbon dioxide, thereby causing the carbon dioxide absorbent to absorb carbon dioxide. The method of bringing the carbon dioxide absorbent into contact with the gas can be selected appropriately depending on the form of the carbon dioxide absorbent, and is not particularly limited. For example, the carbon dioxide absorbent can be brought into contact with the gas containing carbon dioxide by passing the gas containing carbon dioxide through the carbon dioxide absorbent, spraying the carbon dioxide absorbent in the gas containing carbon dioxide, or placing the carbon dioxide absorbent in the gas containing carbon dioxide.

[0061] Examples of carbon dioxide-containing gases include, but are not limited to, air, thermal power plant exhaust gas, steel mill exhaust gas, cement factory exhaust gas, chemical plant exhaust gas, biofermentation gas, and natural gas. Energy-saving carbon dioxide recovery from these gases is particularly required, and the present invention is particularly effective for this purpose. The carbon dioxide concentration, gas pressure, and gas temperature in the gas are not particularly limited, and the method of the present invention can be applied to gases under a wide range of conditions. Furthermore, the carbon dioxide-containing gas may contain acidic gases other than carbon dioxide. Examples of such acidic gases include CO, NOx, and SOx in the exhaust gas, formaldehyde generated in methanol-fueled power generation, and hydrogen chloride and hydrogen sulfide. When the carbon dioxide-containing gas contains acidic gases other than carbon dioxide, it is preferable to combine the method with a known process for removing the other acidic gases. Specifically, the carbon dioxide recovery method of the present invention may be applied to a gas containing acidic gases other than carbon dioxide, or the method of the present invention may be applied after removing the other acidic gases from a gas containing acidic gases other than carbon dioxide by known means.

[0062] In the absorption step, the temperature at which the carbon dioxide absorbent is brought into contact with the gas containing carbon dioxide is, from the viewpoint of improving the amount of carbon dioxide absorbed, preferably 0°C or higher and lower than 60°C, more preferably 20°C or higher and lower than 60°C, and even more preferably 30°C or higher and lower than 60°C.

[0063] More preferably, the method of the present invention comprises an absorption step of contacting the carbon dioxide absorbent with a gas containing carbon dioxide to allow the carbon dioxide absorbent to absorb carbon dioxide, and a desorption step of desorbing carbon dioxide from the carbon dioxide absorbent that has absorbed carbon dioxide in the absorption step, the desorption step comprising at least one step selected from the group consisting of the following (I) to (III). This method makes it possible to separate and recover carbon dioxide from a gas containing carbon dioxide: (I) a step of subjecting the carbon dioxide absorbent that has absorbed carbon dioxide to reduced pressure conditions; (II) a step of contacting the carbon dioxide absorbent that has absorbed carbon dioxide with an inert gas that does not contain carbon dioxide; and (III) a step of heating the carbon dioxide absorbent that has absorbed carbon dioxide.

[0064] <Desorption Step> The desorption step is a step of desorbing carbon dioxide from the carbon dioxide absorbent that has absorbed carbon dioxide in the absorption step. A method for desorbing carbon dioxide from a carbon dioxide absorbent that has absorbed carbon dioxide is preferably a method including at least one step selected from the group consisting of the steps (I) to (III) above. Two or more of the steps (I) to (III) may be combined.

[0065] (I) In the step of subjecting the carbon dioxide absorbent that has absorbed carbon dioxide to reduced pressure conditions (hereinafter also referred to as "step (I)"), the reduced pressure conditions are preferably 10 kPa or less, more preferably 5 kPa or less, and even more preferably 1 kPa or less, from the viewpoint of improving the efficiency of separation and recovery of carbon dioxide. Furthermore, from the viewpoint of suppressing volatilization of the amine compound or amine composition in the carbon dioxide absorbent, the reduced pressure conditions are preferably 0.1 kPa or more. In step (I), the temperature when the carbon dioxide absorbent is subjected to reduced pressure conditions is not particularly limited, but from the viewpoint of suppressing volatilization of the amine compound or amine composition in the carbon dioxide absorbent, the temperature is preferably less than 50°C, more preferably 45°C or less. Furthermore, from the viewpoint of improving the efficiency of separation and recovery of carbon dioxide, the temperature is preferably 0°C or more, more preferably 10°C or more.

[0066] (II) In the step of contacting a carbon dioxide absorbent having absorbed carbon dioxide with an inert gas not containing carbon dioxide (hereinafter also referred to as "step (II)"), desorption of carbon dioxide can be promoted by lowering the partial pressure of carbon dioxide. Examples of the inert gas not containing carbon dioxide include nitrogen, helium, argon, etc., and one or more of these can be used. Among these, from the viewpoint of improving the efficiency of carbon dioxide separation and recovery, the inert gas not containing carbon dioxide is preferably at least one selected from the group consisting of nitrogen and argon. In step (II), examples of a method for contacting the carbon dioxide absorbent with an inert gas not containing carbon dioxide include the same contact method as described in the absorption step. In step (II), the temperature when contacting the carbon dioxide absorbent with an inert gas not containing carbon dioxide is not particularly limited. In step (II), the heating specified in step (III) may be performed simultaneously, or the temperature may be room temperature or lower. From the viewpoint of suppressing volatilization of the amine compound or amine composition in the carbon dioxide absorbent, the temperature is preferably less than 50°C, more preferably 45°C or lower. From the viewpoint of improving the efficiency of separating and recovering carbon dioxide, the temperature is preferably 0°C or higher, and more preferably 10°C or higher.

[0067] (III) The heating temperature in the step of heating the carbon dioxide absorbent that has absorbed carbon dioxide (hereinafter also referred to as "step (III)") is preferably 50°C or higher and 120°C or lower, more preferably 55°C or higher and 110°C or lower, and even more preferably 60°C or higher and 100°C or lower, from the viewpoint of improving the efficiency of separating and recovering carbon dioxide. The heating in step (III) can be carried out by a known method using an apparatus equipped with a heating means. Examples of the heating method include heating with steam or a heat medium, hot air heating, electromagnetic wave heating, ultrasonic heating, and induction heating.

[0068] The carbon dioxide absorbent and carbon dioxide separated in the desorption step can be recovered separately and reused.

[0069] [Carbon dioxide separation and capture apparatus] The carbon dioxide separation and capture apparatus of the present invention (hereinafter also referred to as "the apparatus of the present invention") has an absorption apparatus equipped with a mechanism for bringing the carbon dioxide absorbent into contact with a gas containing carbon dioxide, and causing the carbon dioxide absorbent to absorb carbon dioxide, and a desorption apparatus equipped with a mechanism for desorbing carbon dioxide from the carbon dioxide absorbent that has absorbed carbon dioxide.

[0070] The apparatus of the present invention will be described with reference to Fig. 1. Fig. 1 is a schematic diagram showing one embodiment of a carbon dioxide separation and capture apparatus 100 of the present invention, in which 1 is an absorption apparatus and 2 is a desorption apparatus.

[0071] <Absorption Device> The absorption device 1 in the carbon dioxide separation and capture system 100 is a mechanism that includes the carbon dioxide absorbent and brings the carbon dioxide absorbent into contact with a gas containing carbon dioxide, thereby causing the carbon dioxide absorbent to absorb carbon dioxide.

[0072] The absorption device 1 is not particularly limited as long as it has a configuration that brings the carbon dioxide absorbent into contact with a gas containing carbon dioxide, depending on the form of the carbon dioxide absorbent. For example, as shown in Fig. 1 , the absorption device 1 can be provided with an absorbent holding unit 12 that holds a carbon dioxide absorbent 12a inside a reaction tower 11, and further with a gas supply unit 13 that supplies a gas containing carbon dioxide to the absorbent holding unit 12. Furthermore, from the viewpoint of discharging the carbon dioxide absorbent that has absorbed carbon dioxide from the absorbent holding unit 12 and supplying new carbon dioxide absorbent, the absorption device 1 can also be provided with an absorbent discharge unit (not shown) that discharges the carbon dioxide absorbent 12a held in the absorbent holding unit 12, and an absorbent supply unit (not shown) that supplies new carbon dioxide absorbent to the absorbent holding unit 12.

[0073] The absorption device 1 may further include a heating / cooling mechanism to adjust the temperature when the carbon dioxide absorbent is brought into contact with the carbon dioxide-containing gas. The absorption device 1 may also include a carbon dioxide concentration measurement mechanism to measure the carbon dioxide concentration in the gas. Furthermore, the absorption device 1 may also include a pressurization / depressurization mechanism to adjust the pressure when the carbon dioxide absorbent is brought into contact with the carbon dioxide-containing gas.

[0074] The carbon dioxide separation and capture system 100 may have a connection part 3 for supplying the carbon dioxide absorbent that has absorbed carbon dioxide in the absorption device 1 to the desorption device 2. There are no particular limitations on the means for supplying the carbon dioxide absorbent that has absorbed carbon dioxide from the absorption device 1 to the desorption device 2, and the absorption device 1 may be stopped once after operating for a certain period of time, and the carbon dioxide absorbent in the reaction tower 11 provided in the absorption device 1 may be supplied all at once to the desorption device 2. Alternatively, the carbon dioxide absorbent may be supplied continuously or intermittently from the absorbent holding part 12 of the absorption device 1 to the desorption device 2 using the connection part 3.

[0075] <Desorption device> The desorption device 2 in the carbon dioxide separation and capture system 100 is a mechanism that desorbs carbon dioxide from the carbon dioxide absorbent that has absorbed carbon dioxide in the absorption device 1. The desorption device 2 is not particularly limited as long as it has a mechanism that desorbs carbon dioxide from the carbon dioxide absorbent that has absorbed carbon dioxide in the absorption device 1, but it is preferable that it is equipped with a mechanism for performing at least one of the steps (I) to (III) above. Examples of such a mechanism include a pressure reduction mechanism, an inert gas supply mechanism, and a heating mechanism.

[0076] 1 , the desorption apparatus 2 may include, inside the reaction tower 21, an absorbent holding section 22 that holds a carbon dioxide absorbent 22a that has absorbed carbon dioxide, and may further include a gas discharge section 23 that discharges carbon dioxide desorbed from the carbon dioxide absorbent. The desorption apparatus 2 also includes at least one mechanism (not shown) selected from the group consisting of a pressure reduction mechanism for creating a reduced pressure condition inside the reaction tower 21, an inert gas supply mechanism for supplying an inert gas to the absorbent holding section 22, and a heating mechanism for heating the absorbent holding section 22. In addition to the pressure reduction mechanism, inert gas supply mechanism, and heating mechanism, the desorption apparatus 2 may also include a carbon dioxide concentration measurement mechanism, etc., similar to the absorption apparatus 1.

[0077] The carbon dioxide absorbent after desorbing carbon dioxide in the desorption device 2 can be supplied again to the absorption device 1 from the absorbent discharge section 24, which is used to supply the carbon dioxide absorbent after desorbing carbon dioxide to the absorption device 1, and can be reused.

[0078] The carbon dioxide separation and capture system 100 may further include a capture device for capturing the desorbed carbon dioxide. The captured carbon dioxide can be used for agricultural purposes such as enhanced oil recovery and plant factories; industrial gas purposes such as beverages and welding; chemical synthesis; or carbon dioxide capture and storage (CCS). The captured carbon dioxide may also be concentrated before being used for these purposes.

[0079] The present invention will be described below with reference to examples, but the present invention is not limited to the scope of the examples. In the examples, various measurements and evaluations were carried out by the following methods.

[0080] (Total Amine Value of Amine Compound) The total amine value was measured in accordance with JIS K7237-1995 by the following method. (1) 0.1 g of an amine compound was dissolved in 20 mL of acetic acid. (2) The solution obtained in (1) above was titrated with a 0.1 N perchloric acid-acetic acid solution using an automatic potentiometric titrator ("AT-610" manufactured by Kyoto Electronics Manufacturing Co., Ltd.) to determine the total amine value.

[0081] (Tertiary amine value of amine compound) The tertiary amine value was measured in accordance with ASTM D-2073 by the following method. (1) 0.5 g of an amine compound was precisely weighed into 110 mL of a screw tube, and 25 mL of acetic anhydride and 2 mL of acetic acid were added, and the opening of the screw tube was covered with parafilm. (2) The screw tube of (1) was heated on a hot plate at 130°C for 45 minutes. (3) The solution obtained in (2) above was titrated with a 0.1 N perchloric acid-acetic acid solution using the automatic potentiometric titrator to determine the tertiary amine value.

[0082] (Maximum endothermic temperature of amine compound) DSC measurement was performed on the amine compound as follows to measure the maximum endothermic temperature of the amine compound. First, differential scanning calorimetry was performed on the amine compound using a differential thermogravimeter ("DTG-60" manufactured by Shimadzu Corporation) under conditions of a measurement temperature range of 23 to 350°C, a heating rate of 10°C / min, and a nitrogen atmosphere. From the DSC curve obtained, the temperature at which the amount of endothermic heat associated with the volatilization of the amine compound was maximized was identified, and this temperature was defined as the maximum endothermic temperature of the amine compound.

[0083] (Amine Compound Carbon Dioxide (CO ２ ) Maximum dissociation temperature) A carbon dioxide concentration meter and a petri dish were placed in a retractable desiccator (internal dimensions: 370 mm x 260 mm x 272 mm). An amine compound (5 mmol) was added to the petri dish in the desiccator, and the door was immediately closed. The amine compound was left in the desiccator for 24 hours in an air environment of 23°C and 50% RH. The initial carbon dioxide concentration was adjusted to approximately 400 ppm. Next, the amine compound was removed from the desiccator to obtain an amine compound that had absorbed carbon dioxide. The amine compound that had absorbed carbon dioxide was subjected to DSC measurement as follows to measure the maximum carbon dioxide dissociation temperature of the amine compound. First, differential scanning calorimetry was performed on the amine compound using a differential thermogravimetry analyzer ("DTG-60" manufactured by Shimadzu Corporation) under conditions of a measurement temperature range of 23 to 250°C, a heating rate of 10°C / min, and a nitrogen atmosphere. From the DSC curve thus obtained, the temperature at which the amount of endothermic heat accompanying the desorption of carbon dioxide becomes maximum was identified, and this temperature was taken as the maximum carbon dioxide dissociation temperature of the amine compound.

[0084] (Specific Surface Area and Pore Volume of Porous Material) The specific surface area and pore volume of the porous material were measured using a specific surface area / pore size distribution measuring device ("ASAP2020" manufactured by Shimadzu Corporation).

[0085] (Volume median particle diameter of porous material (D ５０ The particle distribution of the porous material was measured using a laser diffraction / scattering particle size distribution analyzer (Malvern Instruments, "LMS-200e"). The particle size corresponding to a cumulative volume frequency of 50%, calculated from the smallest particle size in the particle distribution, was defined as the volume median particle size (D ５０ )

[0086] (Evaluation 1 of Carbon Dioxide Absorption Capacity: Carbon Dioxide Absorption Capacity of Carbon Dioxide Absorbent Comprising Amine Compound) The carbon dioxide absorption capacity of a carbon dioxide absorbent comprising an amine compound was evaluated by the following method. An NDIR carbon dioxide sensor and a 10 cm diameter petri dish were placed in a 25 L desiccator placed in a constant temperature and humidity room (23°C, 40 to 50% RH). An amine compound (5 mmol) was added to the petri dish in the desiccator, and the desiccator was then sealed. The decrease in carbon dioxide concentration in the desiccator after 1 hour was taken as the carbon dioxide absorption capacity (ppm / h) of the amine compound, and is shown in Table 1.

[0087] (Evaluation 1 of Carbon Dioxide Absorption Capacity and Repeated Usability of Solid Carbon Dioxide Absorbent) The carbon dioxide absorption capacity and repeated usability of the carbon dioxide absorbent (solid carbon dioxide absorbent) containing an amine compound and a porous material listed in Table 2 were evaluated by the following method. 300 mg of the amine compound, 10 g of methanol, and 300 mg of the porous material were added to a nitrogen-purged glass container and stirred for 10 hours to homogenize. The resulting mixture was then placed in an environment of 40 ° C. and 100 hPa to distill off the methanol, and then vacuum-dried at room temperature (23 ° C.) for 24 hours to obtain a solid carbon dioxide absorbent. 15 mg of the resulting solid carbon dioxide absorbent was then placed in a differential thermogravimetry meter (Hitachi High-Tech Corporation, "EXSTER TGD6200") and left to stand for 6 hours at 45 ° C. in a dry air environment, and the increase in mass of the solid carbon dioxide absorbent was measured. Here, the gas used during measurement was air (flow rate: 200 mL / min) during carbon dioxide absorption, and nitrogen (flow rate: 200 mL / min) during carbon dioxide desorption. The carbon dioxide absorption amount of the solid carbon dioxide absorbent was calculated from the increase in mass of the solid carbon dioxide absorbent (first time). The unit of carbon dioxide absorption amount in Table 2 is the carbon dioxide absorption amount (mg) per 1 g of solid carbon dioxide absorbent.

[0088] After the first evaluation of carbon dioxide absorption capacity was completed, the solid carbon dioxide absorbent was removed from the apparatus, and the solid carbon dioxide absorbent that had absorbed carbon dioxide was heated at 120°C for 30 minutes to desorb the absorbed carbon dioxide, thereby regenerating the solid carbon dioxide absorbent. Next, the above-mentioned evaluation of carbon dioxide absorption capacity was performed again on the regenerated solid carbon dioxide absorbent, and the carbon dioxide absorption amount was measured (second time). Next, the solid carbon dioxide absorbent was removed from the apparatus, and the solid carbon dioxide absorbent that had absorbed carbon dioxide was heated at 120°C for 30 minutes to desorb the absorbed carbon dioxide, thereby regenerating the solid carbon dioxide absorbent again. Next, the above-mentioned evaluation of carbon dioxide absorption capacity was performed again on the regenerated solid carbon dioxide absorbent, and the carbon dioxide absorption amount was measured (third time). Here, the carbon dioxide absorption amount retention rate was also calculated based on the first carbon dioxide absorption amount.

[0089] (Evaluation 2 of Carbon Dioxide Absorption Capacity and Repeated Usability of Solid Carbon Dioxide Absorbent: Evaluation Under Practical Conditions) The carbon dioxide absorption capacity and repeated usability under practical conditions of a carbon dioxide absorbent containing an amine compound and a porous material (solid carbon dioxide absorbent) were evaluated by the following method. Carbon dioxide absorbents recover carbon dioxide from mixed gases that contain water vapor in addition to carbon dioxide, such as in air environments including outside air and indoor spaces, and combustion exhaust gases. Therefore, the amounts of carbon dioxide absorbed and desorbed under humidity-controlled conditions that take into account the influence of water vapor in the gas were measured by the following method using a catalyst analyzer ("BELCAT II" manufactured by MicrotrackBell Corporation), and the carbon dioxide absorption capacity and repeated usability of the solid carbon dioxide absorbent were evaluated.

[0090] (Evaluation 2-1: Heating Cycle Evaluation of Solid Carbon Dioxide Absorbent) (1) 300 mg of an amine compound, 10 g of methanol, and 300 mg of a porous material were added to a nitrogen-purged glass container and stirred for 10 hours to achieve homogenization. The resulting mixture was then placed in an environment of 40°C and 100 hPa to distill off the methanol, and then vacuum dried at room temperature (23°C) for 24 hours to obtain a solid carbon dioxide absorbent. (2) Next, 200 mg of the resulting solid carbon dioxide absorbent was filled into the reaction tube of the catalyst analyzer and heated at 100°C for 1 hour in a nitrogen stream (flow rate: 100 mL / min) for drying and degassing pretreatment, after which the reaction tube was kept at 40°C. Next, the inlet gas was switched to a 400 ppm carbon dioxide / nitrogen mixed gas (total flow rate: 1000 mL / min) conditioned at 40 ° C and 40% RH (absorption step), and simultaneously, the change in the outlet gas composition of the catalyst analyzer over time was measured using a gas mass spectrometer (BELMASS; manufactured by MicrotrackBell) to obtain a breakthrough curve. After the amount of carbon dioxide absorption reached saturation, the inlet gas was switched to nitrogen (flow rate: 500 mL / min) and heated to 80 ° C (desorption step), and subsequently, the change in the outlet gas composition of the catalyst analyzer over time was measured using a gas mass spectrometer. The amount of carbon dioxide absorbed by the solid carbon dioxide absorbent was calculated from the time from the start of absorption to saturation and the integrated change in the outlet concentration of carbon dioxide, and is shown in Table 3 (evaluation of the first carbon dioxide absorption capacity). In addition, the amount of carbon dioxide desorbed from the solid carbon dioxide absorbent was calculated from the time from the time the inlet gas was switched to nitrogen to the time when carbon dioxide was almost no longer detected from the outlet side and the integrated change in the outlet concentration of carbon dioxide. (3) After the first evaluation of the carbon dioxide absorption capacity was completed, the operation of (2) above was repeated nine more times for the solid carbon dioxide absorbent that had been regenerated by carrying out the desorption step, and the carbon dioxide absorption step and desorption step were carried out a total of 10 times. The carbon dioxide absorption amount maintenance rates in the fifth and tenth evaluations were calculated based on the carbon dioxide absorption amount in the first evaluation.

[0091] (Evaluation 2-2: Decompression Cycle Evaluation of Solid Carbon Dioxide Absorbent) (1) 100 mg of solid carbon dioxide absorbent produced in the same manner as above was weighed into the reaction tube of the catalyst analyzer, and then the absorbent temperature was maintained at 60 ° C. and pre-treated by decompression and evacuation for 1 hour. Next, the reaction tube was kept at 40 ° C., and the introduced gas was switched to a 400 ppm carbon dioxide / nitrogen mixed gas (total flow rate: 1000 mL / min) humidified to 40 ° C. and 40% RH (absorption step). At the same time, the change over time in the outlet gas composition of the catalyst analyzer was measured with a gas mass spectrometer ("BELMASS" manufactured by MicrotrackBell Corporation), and a breakthrough curve was obtained. The amount of carbon dioxide absorbed by the solid carbon dioxide absorbent was calculated from the time from the start of absorption to saturation and the integrated change in the outlet concentration of carbon dioxide, and is shown in Table 4 (evaluation of the first carbon dioxide absorption capacity). (2) The amount of carbon dioxide desorbed by the decompression of the solid carbon dioxide absorbent was determined as the amount of carbon dioxide absorbed when the solid carbon dioxide absorbent was used after carbon dioxide desorption, because the amount of carbon dioxide equivalent to the carbon dioxide desorbed by the decompression was subsequently absorbed. Specifically, the absorbent that had absorbed carbon dioxide in (1) above was kept at 40°C and manually evacuated using a vacuum pump for 30 minutes (desorption step). Then, 400 ppm carbon dioxide / nitrogen mixed gas was introduced again in the same manner as in (1) above, and the change in the outlet gas composition over time was measured using a gas mass spectrometer (MicrotrackBell's "BELMASS"). The ultimate vacuum after 30 minutes of decompression was 0.5 kPa. (3) After the first evaluation of carbon dioxide absorption capacity was completed, the solid carbon dioxide absorbent that had been regenerated by the desorption step described in (2) above was subjected to the steps (1) and desorption step nine more times, resulting in a total of 10 carbon dioxide absorption and desorption steps. The carbon dioxide absorption amount was calculated based on the carbon dioxide absorption amount at the first evaluation. The carbon dioxide absorption amount in Tables 3 and 4 is expressed in mg of carbon dioxide absorption per 1 g of the solid carbon dioxide absorbent.

[0092] Example 1: Production of hydrogenated acrylonitrile 2-adduct of methyliminobis(propylamine) (MIBPA-2AP) 20.0 g (0.1377 mol) of methyliminobis(propylamine) (Tokyo Chemical Industry Co., Ltd.) and 20.0 g of 2-propanol (Fujifilm Wako Pure Chemical Industries, Ltd.) as a solvent were charged into a 100 mL round-bottom flask equipped with a stirrer, thermometer, nitrogen inlet tube, dropping funnel, and condenser, and the mixture was thoroughly stirred under a nitrogen stream. 14.7 g (0.2770 mol) of acrylonitrile (Sigma-Aldrich) was added dropwise thereto over 10 minutes. After completion of the dropwise addition, the mixture was heated to 65°C and maintained at that temperature for 5 hours. The mixture was then cooled to room temperature, and the solvent was removed using an evaporator to obtain reaction solution (1). A tubular vertical hydrogenation reactor (made of glass, inner diameter 10 mmΦ) was filled with 7.0 g of a hydrogenation catalyst (three-leaf type, diameter 1.2 mmΦ, manufactured by Johnson Matthey Japan "HTCCo2000") containing 15% by mass of cobalt, and then held at 120 ° C. for 1 hour under a hydrogen stream. The temperature was then raised to 240 ° C. and held for 4 hours or more, and the mixture was reduced and activated. After cooling, 45.0 g of 2-propanol, the catalyst, and the reaction solution (1) were all charged into an autoclave (capacity 150 mL, material: SUS316L) equipped with a stirrer and heater, and the gas phase was replaced with hydrogen. After pressurizing to 3.5 MPaG with hydrogen, the temperature was increased while stirring, and the liquid temperature was raised to 80 ° C. in 20 minutes. The pressure was then adjusted to 3.0 MPaG. The reaction was continued for 3 hours under the condition of a liquid temperature of 80° C., while hydrogen was supplied as needed to maintain the pressure at 3.0 MPaG. The reaction liquid was completely concentrated under vacuum to obtain 37.5 g of a product.

[0093] The above product was obtained by distillation of chloroform-d １ H-NMR analysis revealed 1.3 to 1.4 ppm (-NH- and -NH ２ , 6H), 1.6ppm (-CH ２ -, 8H), 2.2ppm (-N-CH ３ , 3H), 2.4ppm (-CH ２ -NH ２ , 4H (NH ２ (excluding the -CH part), 2.6 ppm (-CH ２ -NH-CH ２ -, 8H (excluding NH moiety)), 2.8 ppm (-CH２ -NCH ３ -CH ２ -, 4H (NCH ３ The peaks of the 259.2 molecular ion peak were observed. Furthermore, FD-MS analysis (apparatus: "AccuTOF GCV 4G" manufactured by JASCO Corporation) confirmed that the compound was MIBPA-2AP having the following structure:

[0094] MIBPA-2AP has a total amine value of 1082 and a tertiary amine value of 214, and has five amino groups and one tertiary amino group in the molecule. That is, MIBPA-2AP has about 20 mol % of tertiary amino groups relative to the total amino groups.

[0095] Example 2: Production of hydrogenated acrylonitrile 4-adduct of methyliminobis(propylamine) (MIBPA-4AP) A 300 mL round-bottom flask equipped with a stirrer, thermometer, nitrogen inlet tube, dropping funnel, and condenser was charged with 10 g (0.0688 mol) of methyliminobis(propylamine) (Tokyo Chemical Industry Co., Ltd.), 50.0 g of 2-propanol (Fujifilm Wako Pure Chemical Industries, Ltd.) as a solvent, and 50.0 g of distilled water, and the mixture was thoroughly stirred under a nitrogen stream. To this mixture, 18.6 g (0.3505 mol) of acrylonitrile (Sigma-Aldrich) was added dropwise over 10 minutes. After completion of the dropwise addition, the mixture was heated to 50°C and maintained at that temperature for 6 hours, and then heated to 80°C. An additional 37.2 g (0.7011 mol) of acrylonitrile was added dropwise, and after 18 hours of holding, the mixture was cooled to room temperature. The solvent and unreacted acrylonitrile were distilled off to obtain 25 g of methyliminobis(propylamine)-acrylonitrile 4-adduct. 0.75 g of a hydrogenation catalyst (trefoil-shaped, 1.2 mm diameter, manufactured by Johnson Matthey Japan "HTCCo2000") containing 15% by mass of cobalt was charged into an autoclave (volume 150 mL, material: SUS316L) equipped with a stirrer and heater, 60.0 g of 2-propanol, and 1.5 g of methyliminobis(propylamine)-acrylonitrile 4-adduct, and the gas phase was replaced with hydrogen. The temperature was raised while stirring, and after the liquid temperature reached 80 ° C, the mixture was pressurized to 3.5 MPa with hydrogen. The reaction was continued for 5 hours under the condition of 80° C. while hydrogen was supplied as needed to maintain the pressure at 3.0 MPa. The solvent was distilled off from the reaction solution to obtain 1.5 g of a product.

[0096] The above product was obtained by distillation of chloroform-d １ H-NMR analysis revealed 1.4 ppm (-NH ２ , 8H), 1.6 to 1.8 ppm (-CH ２ -, 12H), 2.2ppm (-N-CH ３ , 3H), 2.4ppm (-CH ２ -NH ２ , 8H (NH ２ (excluding the -N-(CH ２ )-, 12H), 2.8ppm(-CH ２ -NCH ３-CH ２ -, 4H (NCH ３ The peaks of the 4-amino-2-methyl-1,2-dioxanediol (excluding the 4-amino-2-methyl-1,2-dioxanediol part) were observed. Furthermore, a molecular ion peak corresponding to a molecular weight of 373.3 was observed by FD-MS analysis (apparatus: AccuTOF GCV 4G manufactured by JASCO Corporation). From these findings, it was confirmed that the compound was MIBPA-4AP having the structure of the following formula:

[0097] MIBPA-4AP has a total amine value of 1050 and a tertiary amine value of 452, and has seven amino groups and three tertiary amino groups in the molecule. That is, MIBPA-4AP has approximately 43 mol % of tertiary amino groups relative to the total amino groups.

[0098] Example 3: Evaluation of carbon dioxide absorbent comprising amine compound For the carbon dioxide absorbent comprising the amine compound obtained in Example 1, the maximum carbon dioxide dissociation temperature, maximum endothermic temperature, and various amine values ​​were measured by the methods described above. In addition, the carbon dioxide absorption capacity was evaluated based on the above-mentioned "Evaluation 1 of carbon dioxide absorption capacity". The results are shown in Table 1.

[0099] Comparative Examples 1 and 2 Carbon dioxide absorbents composed of the amine compounds shown in Table 1 were evaluated for the same items as in Example 3. The results are shown in Table 1.

[0100]

[0101] The following amine compounds were used in Table 1: MIBPA-2AP: the amine compound obtained in Example 1 TEPA: tetraethylenepentamine (manufactured by Tokyo Chemical Industry Co., Ltd.) PEI: polyethyleneimine having the structure shown in Table 1 (average molecular weight 600; manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.)

[0102] Examples 4 to 5 and Comparative Examples 3 to 4: Preparation and evaluation 1 of solid carbon dioxide absorbents containing amine compounds and porous materials Solid carbon dioxide absorbents were prepared and evaluated using the amine compounds and porous materials shown in Table 2 by the method described in "Evaluation 1 of carbon dioxide absorption capacity and repeated usability of solid carbon dioxide absorbents." The results are shown in Table 2.

[0103]

[0104] Examples 6 to 10 and Comparative Examples 5 and 6: Preparation of solid carbon dioxide absorbents and evaluation under practical conditions Solid carbon dioxide absorbents were prepared and evaluated using the amine compounds and porous materials shown in Table 3 by the method described in "Evaluation 2-1" in the above "Evaluation 2 of carbon dioxide absorption capacity and repeated usability of solid carbon dioxide absorbents." The results are shown in Table 3.

[0105] Examples 11 to 15 and Comparative Examples 7 to 8: Preparation of solid carbon dioxide absorbents and evaluation under practical conditions Solid carbon dioxide absorbents were prepared and evaluated using the amine compounds and porous materials shown in Table 4 by the method described in "Evaluation 2-2" in the above "Evaluation 2 of carbon dioxide absorption capacity and repeated usability of solid carbon dioxide absorbents." The results are shown in Table 4.

[0106]

[0107]

[0108] In the examples and comparative examples shown in Tables 2 to 4, the following amine compounds and porous materials were used. (Amine compounds) MIBPA-2AP: Amine compound obtained in Example 1 MIBPA-4AP: Amine compound obtained in Example 2 TEPA: Tetraethylenepentamine (Tokyo Chemical Industry Co., Ltd.) PEI: Polyethyleneimine having the structure shown in Table 1 (average molecular weight 600; Fujifilm Wako Pure Chemical Industries, Ltd.) (Porous materials) Mesoporous silica SBA15 (Merck & Co., Ltd.) Specific surface area by BET method: 800 m ２ / g, volume median particle diameter (D ５０ ): 100 μm, pore volume: 0.8 cm ３ / g Mesoporous alumina PULAROX (manufactured by SAZOL) Specific surface area by BET method: 150 m ２ / g, volume median particle diameter (D ５０ ): 35 μm, pore volume: 0.9 cm ３ / g Porous carbon MJ(4)030 (manufactured by Toyo Tanso Co., Ltd.) Specific surface area by BET method: 670 m ２ / g, volume median particle diameter (D ５０ ): 5 μm, pore volume: 1.7 cm ３ / g Synthetic adsorbent Diaion HP-20 (manufactured by Mitsubishi Chemical Corporation) Specific surface area by BET method: 590 m ２ / g, volume median particle diameter (D50): 250 μm, pore volume: 1.3 cm ３ / g

[0109] Table 1 shows that the carbon dioxide absorbent comprising the amine compound of the present invention has a higher carbon dioxide absorption capacity than the conventional amine compounds of Comparative Examples 1 and 2 which have a similar structure. Table 2 shows that the solid carbon dioxide absorbent comprising the amine compound of the present invention and a porous material has a high retention rate of the carbon dioxide absorption amount and is therefore excellent in terms of reusability. Furthermore, Tables 3 and 4 show that the solid carbon dioxide absorbent comprising the amine compound of the present invention and a porous material has a high retention rate of carbon dioxide absorption capacity and is excellent in terms of reusability, even when used repeatedly using a mixed gas that contains water vapor in addition to carbon dioxide.

[0110] According to the present invention, it is possible to provide an amine compound that, when used as a carbon dioxide absorbent, has good carbon dioxide absorbency and is particularly excellent in repeated use ability; an amine composition containing the amine compound; a carbon dioxide absorbent containing any of them; a method for recovering carbon dioxide using the carbon dioxide absorbent; and a carbon dioxide separation and recovery apparatus.

[0111] REFERENCE SIGNS LIST 100 Carbon dioxide separation and capture apparatus 1 Absorption device 2 Desorption device 3 Connection section 11, 21 Reaction towers 12, 22 Absorbent holding section 12a Carbon dioxide absorbent 13 Gas supply section 21 Reaction tower 22a Carbon dioxide absorbent that has absorbed carbon dioxide 23 Gas discharge section 24 Absorbent discharge section

Claims

1. An amine compound represented by the following general formula (1): 【Chemistry 1】 In formula (1), R 1 is a hydroxy group or an organic group having 1 to 10 carbon atoms. n1 to n4 each independently represent a number from 3 to 8, and m1 and m2 each independently represent a number of 1 or 2.

2. 2. The amine compound according to claim 1, wherein n1 to n4 in the general formula (1) are all 3.

3. An amine composition containing the amine compound described in claim 1.

4. A carbon dioxide absorbent containing the amine compound described in claim 1 or the amine composition described in claim 3.

5. The carbon dioxide absorbent according to claim 4 , further comprising a porous material.

6. The carbon dioxide absorbent according to claim 5 , wherein the porous material comprises at least one selected from the group consisting of porous silica and porous alumina.

7. The carbon dioxide absorbent according to claim 6, wherein the porous material is in particulate form.

8. The volume median particle diameter (D ５０ 8. The carbon dioxide absorbent according to claim 7, wherein the particle size is 1 μm or more and 500 μm or less.

9. The specific surface area of ​​the porous material by the BET method is 2 m ２ / g or more 3000m ２ The carbon dioxide absorbent according to claim 5, wherein the carbon dioxide absorbent has a molecular weight of 1 / g or less.

10. The pore volume of the porous material is 0.1 cm ３ / g or more 5.0cm ３ The carbon dioxide absorbent according to claim 5, wherein the carbon dioxide absorbent has a molecular weight of 1 / g or less.

11. 6. The carbon dioxide absorbent according to claim 5, wherein a content of the amine compound represented by general formula (1) in the carbon dioxide absorbent is 0.1 parts by mass or more and 1000 parts by mass or less with respect to 100 parts by mass of the porous material.

12. A method for recovering carbon dioxide using the carbon dioxide absorbent described in claim 4.

13. The method according to claim 12, comprising: an absorption step of contacting the carbon dioxide absorbent with a gas containing carbon dioxide to cause the carbon dioxide absorbent to absorb carbon dioxide; and a desorption step of desorbing carbon dioxide from the carbon dioxide absorbent that has absorbed carbon dioxide in the absorption step, wherein the desorption step comprises at least one step selected from the group consisting of the following (I) to (III): (I) A step of subjecting the carbon dioxide absorbent having absorbed carbon dioxide to reduced pressure conditions (II) A step of contacting the carbon dioxide absorbent having absorbed carbon dioxide with an inert gas not containing carbon dioxide. (III) A step of heating the carbon dioxide absorbent having absorbed carbon dioxide.

14. A carbon dioxide separation and recovery system comprising: an absorption device equipped with a mechanism for bringing the carbon dioxide absorbent according to claim 4 into contact with a gas containing carbon dioxide, causing the carbon dioxide absorbent to absorb carbon dioxide; and a desorption device equipped with a mechanism for desorbing carbon dioxide from the carbon dioxide absorbent that has absorbed carbon dioxide.

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