JP5700668B2 - Polymer for absorbing carbon dioxide, and method for separating and recovering carbon dioxide using the polymer - Google Patents

Description

  The present invention relates to a carbon dioxide absorbent for absorbing and separating carbon dioxide contained in a gas, and more particularly to a carbon dioxide absorbent for separating stably with energy saving. It is about. The present invention also relates to a method for separating carbon dioxide from a gas containing carbon dioxide such as combustion exhaust gas.

  Conventionally, separation of carbon dioxide contained in a gas has been performed by various methods. For example, carbon dioxide is removed during the ammonia production process, and a method of absorbing and removing carbon dioxide by bringing it into contact with an alkali absorbing solution is generally performed. Such a method is classified as a chemical absorption method, and carbon dioxide chemically absorbed in the absorption tower is released from the absorption liquid and recovered by heating the absorption liquid in the regeneration tower. The chemical absorption process is characterized by high-efficiency carbon dioxide removal and high-purity carbon dioxide recovery. In recent years, carbon dioxide in the atmosphere has attracted attention as a causative agent of global warming, and carbon dioxide in exhaust gas emitted from thermal power plants or steelworks, cement factories, etc., which are large-scale emission sources, is separated and recovered. Consideration has been made. For the separation and recovery of carbon dioxide from such exhaust gas, when the conventional separation and recovery technology represented by the chemical absorption method is used, the specific gravity of the additional energy required for the separation is large, and the economic efficiency is very large. It becomes a problem. In the case of the chemical absorption method, the energy required for this separation is the largest in the process of heating the absorbing solution that has absorbed carbon dioxide and releasing carbon dioxide. As the conventional alkaline solution, an aqueous alkanolamine solution typified by an aqueous potassium carbonate solution or an aqueous monoethanolamine solution is used, and an absorption solution having a smaller separation energy has been studied using these as basic technologies. Patent Document 1, Patent Document 2, Patent Document 3 and Patent Document 4 propose a method for removing carbon dioxide from combustion exhaust gas using a specific low-molecular amine aqueous solution. Patent Document 5 proposes an acidic gas absorbing liquid containing a tertiary alkanolamine and an amine activator. Although these methods are improved over the monoethanolamine aqueous solution, further energy saving and higher efficiency are desired.

  In addition, low-molecular amines such as these absorbing solutions have a problem that a small amount of amine compound evaporates when contacting with exhaust gas in the process of absorbing carbon dioxide. For this reason, reducing the volatility of the amine compound is also considered as one of the problems.

  On the other hand, the use of polymeric amines as carbon dioxide absorbers has also been studied. Patent Document 6 proposes a carbon dioxide-adsorbing porous resin obtained by addition reaction of a polyvalent amine with porous polymer particles. Patent Document 7 proposes a gas adsorption method using a monodispersed spherical aminomethylated polymer obtained by aminomethylating a polymer of a polyvinyl aromatic compound. However, these techniques do not reduce separation energy, and cannot be applied to large-scale separation such as separation and recovery of carbon dioxide from exhaust gas.

  In the conventional chemical absorption method, the absorbed carbon dioxide is released by thermal energy, and in the process of regenerating the absorption liquid, steam heating is performed to a temperature of about 110 ° C. to 130 ° C., and the absorption liquid is boiled. It is done. For this reason, there is a concern that the amine compound is thermally decomposed in the regeneration process, and the stability of the absorbing liquid in the regeneration process is also considered as one of the problems.

  As a functional polymer having an amino group, a polymer obtained by alkyl-modifying an amino group of polyallylamine with an epoxy compound is proposed in Patent Document 8. In this technique, a polymer having an amino group that exhibits a hydrophilic-hydrophobic thermoreversible response has been proposed. However, there is no known example in which a functional polymer having an amino group having such a structure is used as a carbon dioxide absorbent.

Japanese Patent No. 2871334 Japanese Patent No. 2895325 Japanese Patent No. 3197183 US Patent Application Publication No. 2008-0050296 Japanese Patent No. 2925619 Japanese Examined Patent Publication No. 4-37735 JP 2002-52340 A Japanese Patent No. 3717021

  The present invention solves the above-mentioned problems, provides a carbon dioxide absorbent for separating and recovering carbon dioxide contained in gas with energy saving, and further has no amine compound volatility and can be used stably. It aims at providing a carbon dioxide absorber. Another object of the present invention is to provide a method for separating and recovering carbon dioxide from a carbon dioxide-containing gas such as combustion exhaust gas, using the carbon dioxide absorbent.

｛式中、Ｒ^１は、置換基を有していてもよい炭素数１〜８のアルキル基であり、Ｒ^２は、水素原子又は置換基を有していてもよい炭素数１〜８のアルキル基であり、そしてＲ^１及びＲ^２の置換基は、ヒドロキシル基、メトキシ基、エトキシ基、フェニル基又はメトキシカルボニル基である。｝
で表される構造を有する繰り返し単位を有する二酸化炭素吸収用ポリマー。 That is, the present invention is as follows.
[1] The following general structural formula (I):

{Wherein R ¹ is an optionally substituted alkyl group having 1 to 8 carbon atoms, and R ² is a hydrogen atom or optionally having 1 to 8 carbon atoms. It is an alkyl group, and the substituents of R ¹ and R ² are a hydroxyl group, a methoxy group, an ethoxy group, a phenyl group or a methoxycarbonyl group. }
A carbon dioxide-absorbing polymer having a repeating unit having a structure represented by:

｛式中、Ｒ^３、Ｒ^４及びＲ^５は、それぞれ独立に水素原子又は置換基を有していてもよい炭素数１〜３のアルキル基であり、Ｒ^６は、水素原子又は置換基を有していてもよい炭素数１〜８のアルキル基であり、そしてＲ^３、Ｒ^４、Ｒ^５及びＲ^６の置換基は、水酸基、メトキシ基、エトキシ基、フェニル基又はメトキシカルボニル基であることができる。｝
で表される構造を有する、［１］に記載の二酸化炭素吸収用ポリマー。 [2] The repeating unit is represented by the following general structural formula (II):

{Wherein R ³ , R ⁴ and R ⁵ are each independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms which may have a substituent, and R ⁶ represents a hydrogen atom or a substituent. An optionally substituted alkyl group having 1 to 8 carbon atoms, and the substituents of R ³ , R ⁴ , R ⁵ and R ⁶ are a hydroxyl group, a methoxy group, an ethoxy group, a phenyl group or a methoxycarbonyl group. be able to. }
The polymer for carbon dioxide absorption according to [1], which has a structure represented by:

｛式中、Ｘは、上記一般構造式（Ｉ）又は（ＩＩ）であり、ｎは、１〜１０，０００の整数である。｝
で表される、［１］又は［２］に記載の二酸化炭素吸収用ポリマー。 [3] The repeating unit is represented by the following general structural formula (III):

{In the formula, X is the general structural formula (I) or (II), and n is an integer of 1 to 10,000. }
The polymer for carbon dioxide absorption according to [1] or [2] represented by:

  [4] Any one of [1] to [3], which is a hydrophilic-hydrophobic reversible polymer having a hydrophilic-hydrophobic transition temperature in the range of 4.0 ° C. or higher and 96.0 ° C. or lower in the presence of water. The polymer for carbon dioxide absorption according to one item.

  [5] Hydrophilicity of the polymer in a state in which any amount of carbon dioxide of 2.0 mol% or more and 30.0 mol% or less is absorbed with respect to the amino group constituting the polymer in the presence of water- The carbon dioxide-absorbing polymer according to any one of [1] to [3], which is a hydrophilic-hydrophobic reversible polymer having a hydrophobic transition temperature in a range of 10.0 ° C or higher and 50.0 ° C or lower.

  [6] Hydrophilicity of the polymer in a state in which any amount of carbon dioxide of 40.0 mol% or more and 90.0 mol% or less is absorbed with respect to the amino group constituting the polymer in the presence of water- The carbon dioxide-absorbing polymer according to any one of [1] to [3], which is a hydrophilic-hydrophobic reversible polymer having a hydrophobic transition temperature in the range of 40.0 ° C to 95.0 ° C.

  [7] Any one of [1] to [6], wherein a weight average molecular weight Mw calculated by gel permeation chromatography (GPC) of a 0.5M acetic acid aqueous solution is 1,500 or more and 200,000 or less. The carbon dioxide-absorbing polymer described in the item.

  [8] The polymer for absorbing carbon dioxide according to any one of [1] to [7], which is 15.0% by mass to 90.0% by mass based on the total mass of the carbon dioxide absorbent, and 10 Carbon dioxide absorbent containing 0.0 mass% or more and 85.0 mass% or less of water.

  [9] A step of allowing carbon dioxide to be absorbed by contacting a carbon dioxide-absorbing material according to [8] with a gas containing carbon dioxide, and then heating and heating the absorbent to separate and recover the carbon dioxide. A method for separating and recovering carbon dioxide, comprising:

  [10] The method according to [9], wherein a temperature at which the absorbent material is heated is 60.0 ° C or higher and 100.0 ° C or lower.

  According to the carbon dioxide absorbent and the carbon dioxide separation and recovery method of the present invention, it is possible to save and separate carbon dioxide from a gas such as combustion exhaust gas with energy saving. Further, in the present invention, it is possible to provide an absorbent material in which the amine compound is not volatile and can be used stably, and a continuous and efficient method for separating and recovering carbon dioxide can be provided.

It is the schematic of the carbon dioxide separation-and-recovery apparatus in the conventional chemical absorption method. It is a schematic diagram of the evaluation apparatus of the absorption amount and discharge | release amount of a carbon dioxide absorber. It is a schematic diagram of the evaluation apparatus of the reaction heat of a carbon dioxide absorber.

  Hereinafter, embodiments of the present invention will be described in detail. The polymer for absorbing carbon dioxide of the present invention is characterized by having a repeating unit having a secondary amino group or a tertiary amino group having a specific structure.

[Structure of carbon dioxide absorbing polymer]
The polymer for absorbing carbon dioxide in the present invention is characterized by having a repeating unit having a structure represented by the general structural formula (I). The structure of this repeating unit indicates a polymer having a secondary amine or a tertiary amine in the side chain. As a result of intensive studies by the present inventors, it has been confirmed that such a polymer releases carbon dioxide at a relatively lower temperature than a low-molecular amine compound after absorbing carbon dioxide. Lowering the temperature at the time of releasing carbon dioxide leads to a decrease in thermal energy for raising the temperature of the liquid, and also prevents thermal decomposition of the amine compound and leads to an improvement in stability. The reason why the carbon dioxide releasing ability at a low temperature is improved may be that the thermal physical properties of the polymer chain may affect the polymer. As for the reaction of amine and carbon dioxide, two equilibrium reactions are known as follows: a reaction for forming a carbamate anion and a reaction for forming a bicarbonate.
<Carbamate anion formation reaction>
2RNH ₂ + CO ₂ → RNHCOO ⁻ · RNH ₃ ⁺
<Bicarbonate production reaction>
RNH ₂ + CO ₂ + H ₂ O → RNH ₃ ⁺ .HCO ₃ ⁻

Of the above reactions, the formation of carbamate anion requires another molecule of amine as a counter cation, but it is assumed that the state of molecular motion of the polymer chain affects the stability of this ionic bond. . In addition, it is presumed that the state of molecular motion of the polymer similarly affects the formation reaction of bicarbonate. In order to express such a high-release characteristic of carbon dioxide at a low temperature, in the general formula (1), R ¹ is preferably an alkyl group having 3 to 8 carbon atoms, and 3 or 4 carbon atoms. The alkyl group is more preferably. This is because the reactivity of secondary and tertiary amino groups generally varies greatly depending on the number of alkyl groups to be bonded, and the balance with the effects of substituents such as hydroxyl groups. This is because it also affects.

  Furthermore, it has been found that when the repeating unit has a structure represented by the general structural formula (II), the carbon dioxide release performance at a low temperature is remarkably improved. The reason for this is that, in a polymer having such a structure as a structural unit, the above-described thermal properties appear remarkably due to the presence of hydroxyl groups and amino groups due to the influence of hydrogen bonds between polymer chains or in the same molecular chain. It is guessed that. It was also found that the presence of a hydroxyl group makes the polymer highly hydrophilic and particularly excellent in the presence of water. In the reaction between amine and carbon dioxide, the presence of water molecules is greatly involved, and water molecules are indispensable particularly in reactions that produce bicarbonate. In general, for many amines, it is known that the reaction to generate bicarbonate has a lower heat of reaction than the reaction to generate carbamate anion, and to reduce the thermal energy when releasing carbon dioxide, bicarbonate is used. Generation is better. On the other hand, the reaction that produces bicarbonate is known to have a slow absorption rate, and the balance between the two reactions is considered important. For this reason, it is considered that the hydration of the polymer affects the reactivity. In the present invention, the structure represented by the general structural formula (II) is limited to a structure satisfying the structure represented by the general structural formula (I).

  According to the study by the present inventors, in particular, the effect of the polymer of the general structural formula (II) and the absorption / release performance are extremely remarkable in terms of achieving both the effect of such a polymer and the absorption / release performance of carbon dioxide. Therefore, it was found that the balance between the positional relationship between the amino group and the hydroxyl group and the hydrophilicity / hydrophobicity is important.

  Furthermore, it has also been found that the above-mentioned polymer characteristics have the effect of reducing the heat of reaction in addition to the release performance at low temperatures. Reduction of the heat of reaction directly leads to reduction of energy for regenerating the absorbent by desorbing carbon dioxide by heating. That is, the polymer for absorbing carbon dioxide of the present invention can be continuously and stably separated and recovered with very low energy consumption when used as an absorbent for separating and recovering carbon dioxide. .

  The repeating unit is preferably the general structural formula (III).

  Furthermore, the present inventors have found that the hydrophilic-hydrophobic reversible performance of the polymer is used in controlling the hydration of the polymer. As used herein, the term “hydrophilic-hydrophobic reversibility” refers to a property or performance in which hydrophilicity and hydrophobicity reversibly change. That is, it was found that the reactivity of amino groups and carbon dioxide can be controlled by the hydrophilic-hydrophobic reversible performance of the polymer. The hydrophilic-hydrophobic reversible performance means that the polymer exhibits a hydrophilic and hydrophobic reversible response due to a change in environmental conditions such as temperature or pH. It is possible to further improve the carbon dioxide absorption and release performance of the polymer by changing the reactivity of the amino group and carbon dioxide by using the hydrophilic and hydrophobic transition phenomenon according to the environmental change. It becomes. In applying the hydrophilic-hydrophobic reversible performance of the above-described polymer to the separation and recovery of carbon dioxide, a polymer in which hydrophilicity and hydrophobicity are reversibly transferred depending on the temperature environment is excellent. Specifically, a polymer having a hydrophilic-hydrophobic transition temperature at any temperature between 4.0 ° C. and 96.0 in water is preferable. The term “having a transition temperature” means, for example, that a polymer having a transition temperature of 30 ° C. shows hydrophilicity at less than 30 and hydrophobic at 30 ° C. or more, and these properties depend on the temperature environment. This refers to a reversible transition. This characteristic is superior because temperature is the most easily controlled factor in the environmental difference between carbon dioxide absorption and release, and separation and recovery by conventional chemical absorption methods are also subject to a large temperature difference. This is because the carbon dioxide is repeatedly absorbed and released. For this large temperature difference (for example, absorption at 40 ° C. and release at 120 ° C.), absorption and release can be repeated with a smaller temperature difference by utilizing the hydrophilic-hydrophobic transition depending on the temperature environment. It becomes possible. In order to reduce the temperature difference between absorption and release of carbon dioxide by actually utilizing this temperature difference for carbon dioxide separation and recovery, the hydrophilic-hydrophobic transition temperature is set to 10.0 ° C. or more and 80.0 ° C. or less. More preferably. If the transition temperature is too low, the characteristics cannot be used unless the absorption temperature is set low, and if the transition temperature is too high, the characteristics cannot be used unless the release temperature is set high. . The hydrophilic-hydrophobic transition temperature in the polymer can be arbitrarily expressed and controlled by controlling the structure and content of the repeating unit. Moreover, the transition temperature of the polymer in water and the transition temperature of the carbon dioxide absorbent composed of the polymer differ depending on the presence of components other than water, and the transition temperature of the polymer in the carbon dioxide absorbent depends on these components. It is also possible to adjust.

  By utilizing the above-described reversible transition phenomenon due to the hydrophilic-hydrophobic temperature environment, when carbon dioxide is absorbed and released continuously and repeatedly, the transition of each polymer after absorption and release of carbon dioxide. It is necessary to pay attention to temperature. This is because the heat-induced hydrophilic-hydrophobic transition phenomenon of the polymer of the present invention depends on the pH, and the alkalinity derived from the amino group becomes weak according to the absorption of carbon dioxide. Therefore, when carbon dioxide is absorbed and released continuously and repeatedly, the properties of the polymer at the time of absorption are affected by the amount of carbon dioxide absorbed that cannot be released after the release of carbon dioxide, and the polymer at the time of release The properties of are affected by the amount of carbon dioxide absorbed after absorption. First, regarding the polymer at the time of absorption, the carbon dioxide absorption after release is generally 2.0 mol% or more and 30.0 mol% or less with respect to the amino group. In order for the polymer in this state to be hydrophilic at the time of absorption, it only needs to have a transition temperature higher than the temperature at the time of absorption. Specifically, it is desirable that the transition temperature is 15.0 ° C. or higher in a state where any amount of carbon dioxide of 2.0 mol% or more and 30.0 mol% or less is absorbed with respect to the amino group, More preferably, it is 25 ° C. or more and 50.0 ° C. or less. On the other hand, regarding the polymer at the time of release, the carbon dioxide absorption after absorption is generally 40.0 mol% or more and 90.0 mol% or less with respect to the amino group. The polymer in this state develops a transition between hydrophilicity and hydrophobicity in the process of raising the temperature from the absorption process to the release process, so that the polymer can be hydrophobized at the time of release. Specifically, any of 40.0 ° C. or more and 95.0 ° C. or less in a state in which any amount of carbon dioxide of 40.0 mol% or more and 90.0 mol% or less is absorbed with respect to the amino group. It is desirable to have a transition temperature in the temperature, more preferably 50.0 ° C. or higher and 85.0 ° C. or lower.

[Molecular weight of carbon dioxide absorbing polymer]
The carbon dioxide-absorbing polymer of the present invention is characterized by utilizing the reactivity of the polymer itself with carbon dioxide. The “polymer” of the present invention means a polymer and has a degree of polymerization of a certain level or more. That is, it contains the repeating unit of a polymerizable monomer. An advantage of using such a polymer as a carbon dioxide-absorbing polymer is that it is not volatile. That is, when carbon dioxide is absorbed by contact with the gas, the amine compound (the polymer referred to in the present invention) does not evaporate, so that it is not necessary to take the absorbent out of the system of the separation and recovery process. As the degree of polymerization, a range generally called an oligomer can be included, and it is desirable to have 10 or more unit units. Accordingly, the molecular weight is not particularly limited, but can generally be selected from a range that is easy to produce. For example, the weight average molecular weight Mw converted from the measurement by gel permeation chromatography (GPC) is 1,500 or more and 200 2,000 or less is preferable, 2,000 or more and 20,000 or less is more preferable, and the molecular weight of the carbon dioxide-absorbing polymer may be arbitrarily selected according to the form of the carbon dioxide-absorbing material.

  In addition, what is necessary is just to perform the measurement of the molecular weight by GPC as follows.

A polymer is added to a 0.5 M aqueous acetic acid solution, and the solution which has been allowed to stand at room temperature for 24 hours is filtered through a water-resistant membrane filter having a pore diameter of 0.45 μm to obtain a sample solution, which is measured under the following conditions. The sample is adjusted so that the concentration of the polymer is 0.1 to 0.5% by mass.
Equipment: High-speed GPC HLC8220GPC (manufactured by Tosoh Corporation)
Column: Double of Shodex OHpak SB-806M HQ (Showa Denko)
Eluent: 0.5M acetic acid and 0.1M sodium nitrate aqueous solution Flow rate: 1.0ml / min Oven temperature: 40 ° C
Sample injection volume: 0.10 ml

  Moreover, in calculating the molecular weight of the sample, a molecular weight calibration curve prepared using molecular weight standards of standard polyethylene glycol and standard polyethylene oxide (manufactured by GL Science, PEG-10 and PEO-10) is used.

  The content of the repeating unit in the polymer of the present invention is not particularly limited. However, since the amount of the absorbent per unit carbon dioxide is affected, a larger amount is more preferable for energy saving separation. That is, it is preferable that the content of amine in the polymer is large, but the optimum amount is determined by the structure of the repeating unit and the polymer composition ratio. The content of the repeating unit in the polymer in the present invention is preferably 5.0 mol / kg or more and 15.0 mol / kg or less, more preferably 6.5 mol / kg or more and 10.0 mol / kg or less. It is.

  For the same reason, it is preferable that the polymer content in the carbon dioxide absorbent of the present invention is large. However, the polymer content is greatly related to the physical properties of the absorbent and must be controlled depending on the reactivity with carbon dioxide or the suitability for the process. As a preferable range, it is 15.0 mass% or more and 90.0 mass% or less, More preferably, it is 20.0 mass% or more and 75.0 mass% or less.

  As a method for producing the polymer having a repeating unit, a known method can be used, and there are roughly two types. One is a polymer in which a primary amine of a polymer having an amino group such as polyallylamine or polyvinylamine which is polymerized in advance (may be a copolymer with other vinyl polymerizable monomers) is alkyl-substituted. It is a modification method. In this method, a secondary amine or a tertiary amine can be alkyl-substituted by reacting an amino group-reactive compound with an amino group in the polymer at an arbitrary ratio. Moreover, it is possible to produce a polymer having an arbitrary plurality of structures by reacting two or more compounds having reactivity with amino groups. Examples of the compound reactive with an amino group include alkyl halides, epoxy compounds, aldehydes, and ketones. In particular, when the repeating unit has a structure represented by the general structural formula (II), it can be easily generated by selecting an epoxy compound. Examples of the epoxy compound that can be used for producing the polymer of the present invention include ethylene oxide, propylene oxide, 1,2-epoxybutane, 2,3-epoxybutane, isobutylene oxide, glycidyl methyl ether, glycidyl ethyl ether, glycidol, Examples thereof include styrene oxide, cyclohexene oxide, glycidyl carboxylate and the like. The reaction between the epoxy compound and the amine proceeds easily by heating. The heating temperature has an optimum range depending on the epoxy compound, but is generally in the range of 30 ° C. or more and 100 ° C. or less. In the case of an epoxy compound having a low boiling point such as ethylene oxide, it is preferable to react in an autoclave.

｛式中、Ｒ ^７ は、置換基を有していてもよい炭素数１〜８のアルキル基であり、Ｒ ^８ は、水素原子又は置換基を有していてもよい炭素数１〜８のアルキル基であり、そしてＲ^７ 及びＲ ^８ の置換基は、ヒドロキシル基、メトキシ基、エトキシ基、フェニル基又はメトキシカルボニル基であることができる｝
で示される任意のビニル重合性単量体を重合させる方法であり、必要に応じてその他のビニル重合性単量体と共重合することも可能である。
As another method, the following general structural formula:

{In the formula, R ⁷ is an optionally substituted alkyl group having 1 to 8 carbon atoms, and R ⁸ is a hydrogen atom or optionally having 1 to 8 carbon atoms. An alkyl group, and the substituent of R ⁷ and R ⁸ can be a hydroxyl group, a methoxy group, an ethoxy group, a phenyl group or a methoxycarbonyl group}
Is a method of polymerizing any vinyl polymerizable monomer represented by the formula (1), and can be copolymerized with other vinyl polymerizable monomers as required.

  As the polymerization method, known methods can be applied, and examples thereof include bulk polymerization, solution polymerization, dispersion polymerization, precipitation polymerization, and suspension polymerization. Further, in the case of a monomer having poor polymerizability, it is possible to neutralize the polymer with an alkali after polymerization in a state where the amino group is in the form of hydrochloride. A known radical initiator can be used as the initiator.

  Either method may be selected depending on the target structure and polymer composition ratio, or both of these two methods may be combined.

  The polymer may have another unit as a structural unit in addition to the repeating unit, or may have a primary amino group. Regarding other vinyl polymerizable monomer units, specific monomers include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-ethylstyrene, p-aminostyrene and derivatives thereof, Methyl methacrylate, ethyl methacrylate, propyl methacrylate, methacrylic acid-n-butyl, 2-ethylhexyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, 2-hydroxyethyl methacrylate, methacrylic acid 2-hydroxypropyl acid, 2-hydroxybutyl methacrylate, methyl acrylate, ethyl acrylate, -n-butyl acrylate, isobutyl acrylate, propyl acrylate, 2-ethylhexyl acrylate, phenyl acrylate, Methacrylic acid or esters of acrylic acid, such as 2-hydroxyethyl toluate, 2-hydroxypropyl acrylate, 2-hydroxybutyl acrylate, acrylic acid, methacrylic acid, acrylamide, methacrylamide, maleic acid, vinyl acetic acid, 4-vinyl pyridine etc. are mentioned.

  In addition, the polymer in the present invention can be further reacted with a crosslinking agent having a bifunctional or higher functional reactive group to form a crosslinkable insoluble gel. Examples of such reactive groups include halogenated alkyl groups that are reactive with amino groups, epoxy groups, aldehyde groups, ketone groups, isocyanate groups, acid chloride groups, and the like. Can be made.

  The carbon dioxide-absorbing polymer of the present invention may contain two or more kinds of the aforementioned polymers, and may further contain other components. In particular, it is preferable to include water that is greatly related to the reactivity between amine and carbon dioxide. The water content is preferably 1 equivalent or more with respect to the amount of the repeating unit (amine content) in the carbon dioxide absorbent, but if it is too much, the content of the repeating unit is relatively undesirably reduced. Specifically, the ratio is preferably 10.0% by mass or more and 85.0% by mass or less, and more preferably 25.0% by mass or more and 70.0% by mass or less.

  In the present invention, a combination of a carbon dioxide-absorbing polymer and other components is referred to as a “carbon dioxide absorbent”. Therefore, the above-mentioned thing by the combination of the carbon dioxide absorbing polymer and water also corresponds to the carbon dioxide absorbent in the present invention. Preferably, the carbon dioxide absorbent is 15.0% by mass or more and 90.0% by mass or less of carbon dioxide absorbing polymer and 10.0% by mass or more and 85.0% by mass or less of water based on the total mass of the carbon dioxide absorbent. Containing.

  The carbon dioxide absorbent may contain a solvent other than water as necessary as another component. Depending on the solubility or dispersibility of the polymer, the one to be applied is different, but those having a low vapor pressure or boiling point are not preferable because they are volatilized in the separation and recovery process. Also, those having high reactivity with amines are not preferred. From the viewpoint of energy saving, those having low specific heat and good thermal conductivity are preferred. Specific examples of the solvent that may be contained include polyhydric alcohols such as ethylene glycol, propylene glycol, glycerin, 1,3-butanediol, and 1,4-butanediol, and carbon such as butanol, pentanol, and cyclohexanol. Examples thereof include alcohols having a number of 4 or more, amides such as 2-pyrrolidone, N-methylpyrrolidone, and dimethylacetamide, carbonates such as ethylene carbonate, propylene carbonate, and diethyl carbonate, or silicon oil.

  As other components, a known amine compound may be contained as necessary. It can be contained for the purpose of supplementarily increasing the amount of carbon dioxide absorbed or released. Although there is no restriction | limiting in particular, The thing with a low vapor pressure or boiling point is preferable, and the thing with small heat of reaction with a carbon dioxide is more preferable. Specific examples of amine compounds that can be contained include monoethanolamine, 2-amino-2-methyl-1-propanol, 3-amino-1-propanol, 1-amino-2-butanol, and aniline. Primary amines such as cyclohexylamine, 2-methylaminoethanol, 2-ethylaminoethanol, 2-isopropylaminoethanol, 2-n-butylaminoethanol, piperazine, 2-methylpiperazine, 2,5-dimethylpiperazine, 2 Secondary amines such as piperidinoethanol, 2-dimethylaminoethanol, 2-diethylaminoethanol, 3-dimethylamino-1-propanol, 4-dimethylamino-1-butanol, 2-dimethylamino-2-methyl- 1-propanol, N-ethyl-N-methyl ester Noruamin, methyldiethanolamine, ethyl diethanolamine, triethanolamine, N, N-dimethylaniline, tertiary amines such as pyridine, ethylene diamine, diethylene triamine, tetraethylene pentamine, polyethyleneimine, polyvinylamine, polyallylamine, and the like.

  Moreover, you may add well-known polymers other than the polymer which has the said repeating unit as another structural component. Moreover, it is also possible to add an acid, an alkali, or a salt in order to adjust the physical properties of the polymer having the repeating unit. Further, depending on the form of the carbon dioxide absorbent, it is possible to add a known antifoaming agent or dispersion stabilizer, surfactant, viscosity modifier, corrosion inhibitor and the like.

  As a form of the carbon dioxide absorbent of the present invention, various forms such as a dispersion, an emulsion, a powder, a swollen gel and the like can be taken in addition to the solution state. When handled as a powder, fine powdery inorganic particles or resin particles can be added for the purpose of imparting fluidity. It is also possible to use it while supporting it on a porous support.

<Separation and recovery method>
The carbon dioxide separation and recovery method of the present invention will be described. The greatest feature of the method for separating and recovering carbon dioxide in the present invention is to use the carbon dioxide absorbent described above. Specifically, carbon dioxide is absorbed by bringing the carbon dioxide absorbent in the present invention into contact with a gas containing carbon dioxide at 10 ° C. to 50 ° C., and then the carbon dioxide absorbent is heated. A method of separating and recovering carbon dioxide is most preferable. In particular, when the carbon dioxide absorbent is handled in a solution state, it can be separated and recovered by the same apparatus and equipment as in the conventional chemical absorption method. An outline of an apparatus in a conventional chemical absorption method is shown in FIG. In FIG. 1, the mixed gas containing carbon dioxide is humidified and cooled as necessary, and then supplied to the absorption tower 11 through the gas supply port 14. The mixed gas pushed into the absorption tower 11 is brought into counter-current contact with the absorbing liquid supplied from the nozzle 12 at the lower filling section 13, carbon dioxide in the mixed gas is absorbed and removed by the absorbing liquid, and the decarbonized gas is in the upper part. It is discharged from the discharge port 19. In the absorption liquid regeneration tower 117, the absorption liquid is regenerated in the lower filling unit 111 by heating by the regeneration heater 110, cooled by the heat exchanger 18 and the cooler 16, and returned to the absorption tower. The carbon dioxide separated from the absorption liquid is cooled by the regeneration tower reflux cooler 116, the water vapor accompanying the carbon dioxide is condensed and separated by the gas-liquid separator 114, and discharged and recovered from the recovered carbon dioxide discharge line 115. .

  Furthermore, when the carbon dioxide absorbent of the present invention is used to separate and recover carbon dioxide, the temperature at which carbon dioxide is released by heating can be lowered. Lowering the temperature at the time of releasing carbon dioxide reduces the load on the regenerative heater, reduces the energy required for temperature rise, and enables energy-saving separation and recovery. It is also possible to use unused waste heat by heat exchange or a heat pump. However, since it must be higher than the temperature at the time of absorption, the preferable heating temperature of the carbon dioxide absorbent at the time of release is 60.0 ° C. or higher and 100.0 ° C. or lower. As a still more preferable range, it is 65.0 degreeC or more and 95.0 degreeC or less.

  The gas containing carbon dioxide is not particularly limited, and can be applied to gases having various concentrations, pressures, and temperature conditions. Particularly required for energy saving separation are thermal power plant exhaust gas, steel plant exhaust gas, cement factory exhaust gas, chemical plant exhaust gas, biofermentation gas, natural gas, and the like. Of these gases, those containing an acidic gas other than carbon dioxide as a component are preferably combined with known desulfurization and / or denitration processes.

  Hereinafter, the present invention will be described in detail with reference to examples. In addition, this invention is not restrict | limited by an Example.

<Polymer Production Example 1>
A reaction vessel equipped with a stirrer, a condenser and a thermometer was charged with 40.0 g of a 20% polyallylamine aqueous solution (PAA-05 manufactured by Nitto Boseki Co., Ltd.), and the temperature was raised to 35 ° C. in an oil bath. Next, 9.0 g of propylene oxide and 20.0 g of ethanol were mixed, added dropwise to the reaction vessel over 20 minutes with stirring, and reacted with stirring for 3 hours after the completion of the addition. Furthermore, it heated up at 50 degreeC and made it react, stirring for 3 hours. Thereafter, distillation was carried out to distill off water and ethanol, followed by drying at 50 ° C. under reduced pressure to obtain amine polymer 1. From the C / N value determined from the total organic carbon TOC and total nitrogen TN measurement of the obtained amine polymer 1, 100 mol% modification was confirmed with respect to 100 mol of amino groups of polyallylamine.

<Polymer Production Example 2>
A reaction vessel equipped with a stirrer, a condenser, and a thermometer was charged with 40.0 g of a 20% polyallylamine aqueous solution (PAA-05 manufactured by Nitto Boseki Co., Ltd.) and heated to 60 ° C. in an oil bath. Next, 8.1 g of 1,2-epoxybutane and 20.0 g of ethanol were mixed and added dropwise to the reaction vessel over 20 minutes while stirring. After the completion of the dropwise addition, the reaction was performed for 6 hours with stirring. Thereafter, distillation was performed to distill off water and ethanol, followed by drying at 50 ° C. under reduced pressure to obtain amine polymer 2. From the C / N value determined from the total organic carbon TOC and total nitrogen TN measurement of the amine polymer 2 obtained, 72 mol% modification was confirmed with respect to 100 mol of amino groups of polyallylamine.

<Polymer Production Example 3>
A reaction vessel equipped with a stirrer, a condenser, and a thermometer was charged with 40.0 g of a 20% polyallylamine aqueous solution (PAA-05 manufactured by Nitto Boseki Co., Ltd.) and heated to 60 ° C. in an oil bath. Next, 4.0 g of 1,2-epoxybutane and 10.0 g of ethanol were mixed, dropped into the reaction vessel over 20 minutes while stirring, and reacted with stirring for 6 hours after completion of dropping. At this time, a total portion of the organic carbon TOC and total nitrogen TN were measured using a portion extracted at 50 ° C. under reduced pressure. From the value of C / N, modification of 38 mol% with respect to 100 mol of amino group of polyallylamine was confirmed. Next, after making 35 degreeC with an oil bath, 4.9 g of propylene oxide and 10.0 g of ethanol are mixed, and it is dripped over 20 minutes, stirring to the said reaction container, stirring for 3 hours after completion | finish of dripping. Reacted. Furthermore, it heated up at 50 degreeC and made it react, stirring for 3 hours. Thereafter, distillation was performed to distill off water and ethanol, followed by drying at 50 ° C. under reduced pressure to obtain amine polymer 3. From the C / N value obtained from the total organic carbon TOC and total nitrogen TN measurement of the resulting amine polymer 3, 58 mol% (96 mol% in total) modification was confirmed with respect to 100 mol of the amino group of the polymer. .

<Polymer Production Example 4>
A reaction vessel equipped with a stirrer, a condenser, and a thermometer was charged with 40.0 g of a 20% polyallylamine aqueous solution (PAA-05 manufactured by Nitto Boseki Co., Ltd.) and heated to 60 ° C. in an oil bath. Next, 5.1 g of 1,2-epoxybutane and 10.0 g of ethanol were mixed, dropped into the reaction vessel over 20 minutes while stirring, and reacted with stirring for 6 hours after the completion of dropping. At this time, a total portion of the organic carbon TOC and total nitrogen TN were measured using a portion extracted at 50 ° C. under reduced pressure. From the value of C / N, 47 mol% of alkyl modification was confirmed with respect to 100 mol of amino groups of polyallylamine. Next, after making 35 degreeC with an oil bath, 6.1 g of propylene oxide and 10.0 g of ethanol are mixed, and it is dripped over 20 minutes, stirring to the said reaction container, stirring for 3 hours after completion | finish of dripping. Reacted. Furthermore, it heated up at 50 degreeC and made it react, stirring for 3 hours. Thereafter, distillation was performed to distill off water and ethanol, followed by drying at 50 ° C. under reduced pressure to obtain amine polymer 4. From the total organic carbon TOC of the obtained amine polymer 4 and the C / N value determined from the total nitrogen TN measurement, 69 mol% (116 mol% in total) of alkyl modification was confirmed with respect to 100 mol of the amino group of the polymer. did.

<Polymer Production Example 5>
A reaction vessel equipped with a stirrer, a condenser and a thermometer was charged with 40.0 g of a 20% polyallylamine aqueous solution (PAA-05 manufactured by Nitto Boseki Co., Ltd.), and the temperature was raised to 35 ° C. in an oil bath. Next, 16.3 g of propylene oxide and 20.0 g of ethanol were mixed, added dropwise to the reaction vessel over 20 minutes with stirring, and reacted with stirring for 3 hours after the completion of the addition. Furthermore, it heated up at 50 degreeC and made it react, stirring for 3 hours. Thereafter, distillation was performed to distill off water and ethanol, followed by drying at 50 ° C. under reduced pressure to obtain amine polymer 5. From the C / N value obtained from the total organic carbon TOC and total nitrogen TN measurement of the obtained amine polymer 5, 171 mol% modification was confirmed with respect to 100 mol of the amino group of polyallylamine.

<Polymer Production Example 6>
A reaction vessel equipped with a stirrer, a condenser, and a thermometer was charged with 40.0 g of a 20% polyallylamine aqueous solution (PAA-03, manufactured by Nitto Boseki Co., Ltd.) and heated to 60 ° C. in an oil bath. Next, 11.1 g of 1,2-epoxybutane and 20.0 g of ethanol were mixed, dropped into the reaction vessel over 20 minutes while stirring, and reacted with stirring for 6 hours after completion of dropping. Thereafter, distillation was carried out to distill off water and ethanol, followed by drying at 50 ° C. under reduced pressure to obtain amine polymer 6. From the C / N value determined from the total organic carbon TOC and total nitrogen TN measurement of the amine polymer 6 obtained, 100 mol% modification was confirmed with respect to 100 mol of the amino group of polyallylamine.

  Table 1 shows the structure of the repeating units of the obtained amine polymers 1 to 6, the amine content (mmol / g) calculated from the total nitrogen TN measurement, and the hydrophilic-hydrophobic transition temperature in water. .

The total organic carbon TOC and total nitrogen TN were measured with the following apparatus.
Total organic carbon: TOC-VCP and TN unit TNM-1 (manufactured by Shimadzu Corporation)
The measurement was performed by dissolving the polymer with water. Those not dissolved at room temperature were dissolved by adding a 1N hydrochloric acid aqueous solution. The modification rate was determined from the difference in C / N before and after the reaction, and the amine content was determined from the value of N.

  The hydrophilic-hydrophobic transition temperature was a temperature at which polymer precipitation occurred when the temperature of the aqueous solution or absorbent was increased from 4 ° C. to 96 ° C. at 1 ° C./min. At the same time, the pH was measured, and it was confirmed that the pH started to decrease simultaneously with the precipitation.

<Preparation of absorbent material>
The prepared amine polymers 1 to 6 and water or a solvent were mixed and dissolved with the composition shown in Table 2 to obtain carbon dioxide absorbents 1 to 7. Absorbents 8 to 11 were prepared as comparative absorbents. Table 2 also shows the amine content in the absorbent and the polymer transition temperature in the absorbent.

<Explanation of abbreviations>
BD: 1,4-butanediol MEA: monoethanolamine EAE: 2-ethylaminoethanol AMP: 2-amino-2-methyl-1-propanol PAA: polyallylamine (PAA-05 manufactured by Nittobo Co., Ltd.)

<Evaluation method of carbon dioxide absorber>
The apparatus shown in FIG. 2 was created. This device uses a pump to circulate a gas containing carbon dioxide in a closed system, absorbs carbon dioxide by ventilating a gas cleaning bottle containing an absorbent, and measures the amount of absorption from the concentration of carbon dioxide in the gas. Device. The evaluation method is for the gas supplied from the carbon dioxide cylinder 21 while the valves 25 and 26 are closed and the valve 27 is opened and the pump 211 circulates the gas at a flow rate of 1.5 L / min. The syringe 22 is charged with 500 ml of carbon dioxide, and further adjusted with air so that the carbon dioxide concentration is 17% by volume. A carbon dioxide absorbing material is charged into the gas cleaning bottle 214, and the temperature is kept constant by the oil bath 213 so that the internal temperature becomes an arbitrary temperature. Next, the valves 25 and 26 are opened, the valve 27 is closed, the gas containing carbon dioxide is circulated toward the gas washing bottle 214, and the amount of carbon dioxide absorbed by the absorbent is monitored by the carbon dioxide concentration meter 29. To do. After evaluating the absorption performance, the temperature of the oil bath is raised, the absorption amount is measured in the same manner, and the decrease in the absorption amount is evaluated as the release amount. The amount of carbon dioxide absorbed is calculated from the concentration of carbon dioxide and the amount of air 2.85 L calculated from the initial internal volume of the apparatus. The initial volume in the apparatus was calculated from the carbon dioxide concentration by performing the same operation without using an absorbent material. The room was at normal pressure and room temperature.

  Table 3 shows the amount of absorption and release at each absorption material, absorption temperature and release temperature. Carbon dioxide was absorbed for 30 minutes, and carbon dioxide was released for 20 minutes after the temperature was raised. Absorption and release are expressed as mole percent of carbon dioxide relative to 100 moles of amine.

  Comparing Examples 1 to 4 and Comparative Examples 1 to 3, it can be seen that the absorbent materials 1 to 4 of the present invention have a large amount of release at 70 ° C., although the amount of absorption at 30 ° C. is low. That is, it can be said that the absorbent material has high carbon dioxide release performance at a relatively low temperature of 70 ° C. In addition, in the unmodified polyallylamine of Comparative Example 4, although the absorption amount is high, the release amount is very low, and it can be seen that the difference in structure in the polymer greatly affects the release amount. In Example 5, although the absorption performance has fallen compared with Example 1, it is confirmed that the discharge | release performance of the carbon dioxide in low temperature is improving. In Example 6, the amount of absorption was comparable to that of the monoethanolamine aqueous solution of Comparative Example 5, and a significant difference was observed in the amount released at 78 ° C. In Example 7, the amine polymer 6 was precipitated insoluble in water at 30 ° C., but it was confirmed that it was dissolved along with the absorption of carbon dioxide and hydrated in the absorption process. In Examples 6 and 7, it was confirmed that precipitation occurred in the process of raising the temperature to the release temperature, and it was confirmed that phase transition (dehydration) occurred in a state where carbon dioxide was absorbed. In Example 8, no polymer was precipitated by the addition of 1,4-butanediol, but the carbon dioxide release performance at 70 ° C. was excellent. From the above results, it was confirmed that the absorbent material of the present invention has excellent release performance at a relatively low temperature and can be separated and recovered at less than 100 ° C. It is confirmed that the amine polymer used in the present invention is not volatile and does not thermally decompose at 150 ° C. or lower.

  About the absorbers 1 and 4 for an Example and the absorbers 8 and 11 for a comparative example, the heat of reaction with a carbon dioxide was measured with the following method.

<Evaluation method of reaction heat of carbon dioxide absorbent>
The reaction heat was measured using a reaction calorimeter C-80 (manufactured by SETARAM). As the cell, a gas circulation normal pressure type (stainless steel 31/1415) was used, and devices were connected to the gas inlet and outlet of the cell as shown in FIG. The measuring method put each absorbent material 4g in the cell, and set it to C-80. The temperature was adjusted to 30 ° C. and stabilized. The ball valve 34 was closed, carbon dioxide supplied from the carbon dioxide cylinder 31 was injected with 100 ml of carbon dioxide with the gas syringe 32, and the ball valve 34 was opened. While measuring the amount of heat generated by C-80, the amount of absorption was measured by the pressure gauge 35 by the decrease in internal pressure. The calorific value and absorption amount were calculated using a calibration curve of compression heat and internal pressure measured without putting a sample in advance. The reaction heat was calculated by converting the value at which the amount of carbon dioxide absorbed reached 25 mol% with respect to 100 mol of amine per 1 mol of absorbed carbon dioxide, and calculating the average amount of reaction heat.

Result of the heat of reaction measurement, absorber 1, 76.5KJ / mol CO ₂ were used in the examples and was absorbent 4, 72.0KJ / mol CO _2. On the other hand, the absorbent material 8 used in Comparative Example, a 89.1KJ / mol CO _2, was 91.4KJ / mol CO ₂ in the absorbent member 11. From this result, it was confirmed that the polymer for absorbing carbon dioxide and the absorbent of the present invention had low reaction heat.

  Table 4 shows the results of measuring the weight average molecular weights (Mw) of the amine polymers 1 to 6 used in Examples of the present invention and the polyallylamine PAA-03 and PAA-05 used as raw materials. In addition, a weight average molecular weight (Mw) is measured by GPC by the above-mentioned method, and is shown as a value in terms of polyethylene glycol.

<Examples of production of polymers for other reference examples>
A reaction vessel equipped with a stirrer, a condenser and a thermometer was charged with 25.0 g of a 20% polyallylamine aqueous solution (PAA-03 manufactured by Nitto Boseki Co., Ltd.), and the temperature was raised to 40 ° C. in an oil bath. Next, 1.6 g of paraformaldehyde and 20.0 g of water were mixed, dropped into the reaction vessel over 20 minutes while stirring, and reacted with stirring for 6 hours after the completion of dropping. Thereafter, distillation was performed to distill off water, followed by drying at 50 ° C. under reduced pressure to obtain amine polymer 7. From the C / N value determined from the total organic carbon TOC and total nitrogen TN measurement of the amine polymer 7 obtained, 60.5 mol% methylol modification was confirmed with respect to 100 mol of the amino group of polyallylamine. That is, an amine polymer composed of 60.5 mol% of a secondary amine to which CH ₂ OH was added and 39.5 mol% of a primary amine was obtained.

  When the obtained amine polymer 7 was mixed with water at a ratio of 30% by mass, it did not dissolve. The obtained mixture of the amine polymer 7 and water was evaluated for carbon dioxide absorption / release performance at an absorption temperature of 30 ° C. and a release temperature of 88 ° C. by the carbon dioxide absorbent evaluation method described above. As a result, the absorbed amount at 30 ° C. was 18.3 mol%. The amount released at 88 ° C. was 2.9 mol%.

  The present invention can provide a carbon dioxide absorbent for absorbing and separating carbon dioxide contained in gas, and more specifically, carbon dioxide for energy-saving and stable separation. An absorbent material can be provided. In addition, a method for separating carbon dioxide from a gas containing carbon dioxide such as combustion exhaust gas can be provided.

DESCRIPTION OF SYMBOLS 11 Absorption tower 12, 112 Nozzle 13, 111 Lower filling part 14 Exhaust gas supply port 15, 17 Absorption liquid circulation pump 16 Cooler 18 Heat exchanger 19 Decarbonized exhaust gas exhaust port 110 Regeneration heater 113 Reflux water pump 114 Gas-liquid separation 115 Recovery carbon dioxide discharge line 116 Regeneration tower reflux cooler 117 Absorption liquid regeneration tower 21 Cylinder 22 Gas syringe 23 Three-way valve 24 Check valve 25, 26, 27 Ball valve 28 Tedlar bag 29 Infrared carbon dioxide concentration meter 210 Stainless steel (SUS) piping 211 gas circulation pump 212 gas flow meter 213 warm bath 214 muenke-type gas cleaning bottle (made of glass, 250 ml)
215 Glass container 216 Condenser 31 Cylinder 32 Gas syringe 33 Three-way valve 34 Ball valve 35 Pressure gauge 36 Screw cap bottle (250 ml)
37 SUS piping (φ6mm)
38 C-80 cells

Claims (10)

The following general structural formula (IIIA):

{In formula, R < ³ >, R < ⁴ > and R < ⁵ > are the C1-C3 alkyl groups which may have a hydrogen atom or a substituent, and R < ⁶ > has a hydrogen atom or a substituent. Which may be an alkyl group having 1 to 8 carbon atoms, and the substituents of R ³ , R ⁴ , R ⁵ and R ⁶ may be a hydroxyl group, a methoxy group, an ethoxy group, a phenyl group or a methoxycarbonyl group, And n is an integer of 10 to 10,000. }
A carbon dioxide-absorbing polymer having a repeating unit represented by: In the general structural formula (IIIA), R ³ Is a methyl group or an ethyl group, and R ⁴ , R ⁵ And R ⁶ The carbon dioxide-absorbing polymer according to claim 1, which has a repeating unit in which is a hydrogen atom. The polymer for absorbing carbon dioxide according to claim 2, which is obtained by reacting polyallylamine with propylene oxide and / or 1,2-epoxybutane.   The hydrophilic-hydrophobic reversible polymer according to any one of claims 1 to 3, which is a hydrophilic-hydrophobic reversible polymer having a hydrophilic-hydrophobic transition temperature in the range of 4.0 ° C to 96.0 ° C in the presence of water. Carbon dioxide absorbing polymer.   The hydrophilic-hydrophobic property of the polymer in a state in which any amount of carbon dioxide of 2.0 mol% or more and 30.0 mol% or less is absorbed with respect to the amino group constituting the polymer in the presence of water. The polymer for absorbing carbon dioxide according to any one of claims 1 to 3, which is a hydrophilic-hydrophobic reversible polymer having a transition temperature in a range of 10.0 ° C or higher and 50.0 ° C or lower.   The hydrophilic-hydrophobic property of the polymer in a state in which any amount of carbon dioxide of 40.0 mol% or more and 90.0 mol% or less is absorbed with respect to the amino group constituting the polymer in the presence of water. The polymer for carbon dioxide absorption according to any one of claims 1 to 3, which is a hydrophilic-hydrophobic reversible polymer having a transition temperature in a range of 40.0 ° C or higher and 95.0 ° C or lower.   The weight average molecular weight Mw calculated by gel permeation chromatography (GPC) of a 0.5M acetic acid aqueous solution soluble component is 1,500 or more and 200,000 or less, The dioxide dioxide as described in any one of Claims 1-6. Carbon absorbing polymer.   The polymer for absorbing carbon dioxide according to any one of claims 1 to 7, which is 15.0 mass% to 90.0 mass% based on the total mass of the carbon dioxide absorbent, and 10.0 mass% or more. A carbon dioxide absorbent containing 85.0% by mass or less of water.   The carbon dioxide absorbing material according to claim 8 includes a step of absorbing carbon dioxide by contacting a gas containing carbon dioxide, and then separating and recovering carbon dioxide by heating the absorbing material. Carbon dioxide separation and recovery method.   The method of Claim 9 whose temperature which heats the said absorber is 60.0 degreeC or more and 100.0 degrees C or less.

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