JP6530167B2 - Carbon dioxide chemical absorption liquid and carbon dioxide separation and recovery method - Google Patents

Description

The present invention relates to a carbon dioxide chemical absorbing solution that chemically absorbs carbon dioxide and a carbon dioxide separation and recovery method using the carbon dioxide chemical absorbing solution.

  The technology to separate and recover acid gas, especially carbon dioxide, is necessary for the production of hydrogen and methane from natural gas as raw materials, and for the maintenance of the living environment in a closed state such as space and ocean, etc. From the viewpoint of emission reduction, research has been actively conducted on large-scale emission sources such as thermal power plants and steel mills. In addition, removal of acid gases other than carbon dioxide such as nitrogen oxides, sulfur oxides, hydrogen sulfide, inorganic acids and organic acids is also an industrially and socially important technology. As an acid gas separation technique, a physical absorption method, a chemical absorption method, a membrane separation method, an adsorption method and the like are known.

  Among them, the chemical absorption method is an acid gas separation technology using an absorption liquid that chemically reacts with an acid gas. For example, a gas containing an acid gas is brought into contact with the absorbing solution at around room temperature, the acid gas is chemically absorbed by the absorbing solution, and a gas having a reduced acid gas concentration is separated from the absorbing solution having absorbed the acid gas. Then, the temperature of the separated absorbing solution is raised to dissipate the acid gas from the absorbing solution to recover the acid gas. Further, the absorbing solution which has released the acid gas is regenerated and is again used for separation and recovery of the acid gas.

  As this chemical absorption method, a method using an aqueous solution containing an amine compound and an alkali metal salt as a chemical absorption solution of carbon dioxide has been proposed. For example, Patent Document 1 describes a method of using a monoethanolamine aqueous solution as an absorbent. In addition, a separation and recovery method of acid gas using an ionic liquid as a chemical absorption liquid has also been reported. For example, Patent Document 2 describes a gas purification method using an absorbing liquid containing an ionic liquid, which is a liquid into which a primary amine group has been introduced, as a main component.

Unexamined-Japanese-Patent No. 5-184865 JP, 2006-36950, A

  However, the acid gas separation and recovery method using the aqueous solution of amine compound described in Patent Document 1 as the absorbing solution requires high temperature conditions of 100 ° C. or higher to dissipate the acidic gas from the absorbing solution and regenerate the absorbing solution. There is a problem of Also, in addition to the heat of reaction for breaking the chemical bond between the absorbing liquid and carbon dioxide, the thermal energy required for temperature increase of water with large specific heat capacity and evaporation of water takes a lot, and the thermal energy required for absorbing liquid regeneration is remarkable There is a problem of being large. In addition, since the absorbing solution volatilizes due to the temperature rise, it is necessary to install additional equipment such as an absorbing solution recovery device, which requires an excessive investment in facilities, and further, the loss due to the aging deterioration of the absorbing solution is also regarded as a problem. There is.

  On the other hand, the method of using the ionic liquid described in Patent Document 2 as an absorbing liquid is that the ionic liquid is non-volatile and can be reused without loss, and water as a solvent is unnecessary and energy loss due to the latent heat of vaporization of water is almost negligible. The specific heat capacity is small compared to water, and the energy required for raising the temperature of the absorbing liquid can be reduced, and so on, as compared with the conventional aqueous solution of amine compound, consumption during regeneration of the absorbing liquid It is believed that energy can be reduced significantly. However, the absorbing solution using the ionic liquid described in Patent Document 2 is heated at 100 ° C. or more in order to regenerate the absorbing solution.

  Here, the ionic liquid is generally a liquid salt composed of only a cation and an anion, and as its features, it has a very low vapor pressure, is flame retardant, is thermally and chemically stable. And liquid in a wide temperature range, having electrical conductivity, and the like. Therefore, various studies have been conducted on ionic liquids as electrolytes of electrochemical devices, solvents in various processes such as separation and purification and organic reactions, and functional materials such as actuators and lubricants. However, studies using an ionic liquid as an absorbing solution for an acid gas separation and recovery method are still not sufficient.

In the technical field of separating and recovering acid gases such as carbon dioxide, there has been a strong demand for higher efficiency of the process from the viewpoint of energy saving. To meet this requirement, for example, a large amount of absorbed acid gases in (a t ₁ in this case) around room temperature can be easily dissipated acid gases when heated to a predetermined temperature (to t ₂₎ The absorption liquid is required because the specific heat capacity is small and the latent heat of vaporization can be ignored. That is, development of a low specific heat and non-volatile absorption liquid that discharges a large amount of acid gas with temperature change (Δt = t ₂ −t ₁ ) at the time of absorption and release is desired. If this requirement is not satisfied, the acid gas remains in the absorbing solution, and the regeneration of the absorbing solution is insufficient, so that the amount of acid gas absorbed at the time of reuse is significantly reduced.

  The prior art of the absorption liquid using an ionic liquid takes advantage of the low specific heat and non-volatile characteristics of the ionic liquid, and is an excellent method compared to conventional aqueous solutions of amine compounds and alkali metal salts, but The amount of acid gas discharged due to temperature change is not always sufficient, and further technological development of highly efficient absorbent has been awaited.

  In order to further reduce the energy required for regeneration, the temperature dependency of the acid gas absorption amount is increased, and a large amount of acid gas is absorbed at room temperature, while most absorbed acid gas is dissipated at 100 ° C. or less. An ionic liquid that can be

That is, the subject of the present invention is that it does not require water as a solvent, the temperature dependency of carbon dioxide absorption is large, and a large amount of carbon dioxide can be absorbed at around room temperature, while most absorbed carbon dioxide at 100 ° C. or less It is an object of the present invention to provide a carbon dioxide chemical absorbing solution which can dissipate carbon dioxide , and to provide an energy saving and highly efficient carbon dioxide separation and recovery method using it.

  As a result of intensive research and development aimed at controlling the acid gas absorption amount of an ionic liquid and its temperature dependence, the present inventors used the ionic liquid consisting of a cation having a polyethyleneamine skeleton and an anion to obtain the above-mentioned. It has been found that the problems can be solved, and the present invention has been completed.

In order to solve the above problems, the carbon dioxide chemical absorbing solution of the present invention is
Ri cations and anions Tona, comprising an ionic liquid having a melting point Ru der below 50 ° C.,
The anion is at least one selected from the group consisting of an amide anion and CF ₃ SO ₃ ⁻ ,
The cation has one or more primary or secondary amino groups, and an ethylenediamine or propylenediamine skeleton,
In the ethylenediamine or propylenediamine skeleton, at least one nitrogen atom in the skeleton is a primary or secondary amino group, and at least one nitrogen atom in the skeleton is aminium to which a hydrogen cation is bound,
The hetero element in the cation is an element other than carbon, hydrogen and oxygen.

  The cation preferably has a tertiary amino group.

Wherein ethylenediamine or propylenediamine skeleton is preferably a polyethylene diamine or polypropylene diamine skeleton.

The polyethylene diamine or polypropylene diamine skeleton is preferably a diethylenetriamine skeleton or N-(2-aminoethyl) piperazine backbone.

Further, the carbon dioxide separation and recovery method of the present invention is
Comprising carbon dioxide chemical absorption liquid of the, carbon dioxide by contacting a mixed gas containing carbon dioxide is absorbed in the carbon dioxide chemical absorption liquid, for selectively separating the carbon dioxide from the mixed gas .

It is preferable that the carbon dioxide be absorbed by carbon dioxide , and the carbon dioxide be dissipated and recovered by raising the temperature to a temperature higher than the temperature at the time of absorption, and the carbon dioxide chemical absorbing solution be regenerated.

The carbon dioxide chemical absorption solution that has absorbed carbon dioxide is heated to a temperature higher than the temperature at absorption and 100 ° C. or less, and 80% or more of the absorbed carbon dioxide is released and recovered, and the carbon dioxide chemical absorption solution is It is preferable to include regeneration.

Carbon dioxide chemical absorption liquid containing absorbed carbon dioxide by vacuum, recovered by stripping the absorbed carbon dioxide and involves playing carbon dioxide chemical absorption liquid preferably.

The carbon dioxide chemical absorption liquid of the present invention does not require water as a solvent, has a large temperature dependency of carbon dioxide absorption, and absorbs a large amount of carbon dioxide at about room temperature, but absorbs most of it at 100 ° C. or less. It can dissipate carbon dioxide . In addition, the carbon dioxide separation and recovery method using the carbon dioxide chemical absorbing solution is energy saving and high efficiency.

The figure which shows a carbon dioxide absorption test device. NMR spectrum of [HexEDA] [Tf ₂ N]. NMR spectrum of [HexEDA] [Tf ₂ N] after CO ₂ absorption. NMR spectrum of [HexEDA] [Tf ₂ N] ([bmim] [Tf ₂ N] diluted). NMR spectrum of [HexEDA] [Tf ₂ N] ([bmim] [Tf ₂ N] diluted) after CO ₂ absorption. _{[EtHexDETA] [Tf 2 N]} ([bmim] [Tf 2 N] dilution) NMR spectra of. After CO ₂ absorption _{[EtHexDETA] [Tf 2 N]} ([bmim] [Tf 2 N] dilution) NMR spectra of. _{[EtHexDETA] [Tf 2 N]} NMR spectra (Tetra glyme dilution). NMR spectrum of [EtHexDETA] [Tf ₂ N] (Tetra Glyme diluted) after CO ₂ absorption. NMR spectrum of [EtHexEDA] [Tf ₂ N]. NMR spectrum (40 ° C.) of [EtHexEDA] [Tf ₂ N] after CO ₂ absorption. NMR spectrum (60 ° C.) of [EtHexEDA] [Tf ₂ N] after CO ₂ absorption. NMR spectrum of [EtHexEDA] [Tf ₂ N] ([bmim] [Tf ₂ N] diluted). NMR spectrum of [EtHexEDA] [Tf ₂ N] ([bmim] [Tf ₂ N] diluted) after CO ₂ absorption. NMR spectrum (40 ° C.) of [EtHexEDA] [CF ₃ SO ₃ ]. NMR spectrum (60 ° C.) of [EtHexEDA] [CF ₃ SO ₃ ] after CO ₂ absorption. NMR spectrum of [EtHexEDA] [CF ₃ SO ₃ ] ([bmim] [CF ₃ SO ₃ ] diluted). CO ₂ after absorption _{[EtHexEDA] [CF 3 SO 3} ] ([bmim] [CF 3 SO 3] dilution) NMR spectra of. NMR spectrum of a solution of [AmEtPipe] [Tf ₂ N] in polyethylene glycol. NMR spectrum of [AmEtPipe] [Tf ₂ N] in polyethylene glycol solution after CO ₂ absorption. NMR spectra of [bmim] [Tf ₂ N] solutions of [PDA] [Tf ₂ N]. NMR spectra of [bmim] [Tf ₂ N] solutions of [PDA] [Tf ₂ N] after CO ₂ absorption. NMR spectrum of [Pipe] [Tf ₂ N] in polyethylene glycol solution. NMR spectrum of [Pipe] [Tf ₂ N] in polyethylene glycol solution after CO ₂ absorption. NMR spectrum of a polyethylene glycol solution of [MePipe] [Tf ₂ N]. NMR spectrum of a polyethylene glycol solution of [MePipe] [Tf ₂ N] after CO ₂ absorption. The graph which shows the temperature dependence of the carbon dioxide absorption amount of an acidic gas chemical absorption liquid. The graph which shows the temperature dependence of the carbon dioxide absorption amount of an acidic gas chemical absorption liquid. The graph which shows the temperature dependence of the carbon dioxide absorption amount of an acidic gas chemical absorption liquid. The graph which shows the temperature dependence of the carbon dioxide absorption amount of an acidic gas chemical absorption liquid. The graph which shows the temperature dependence of the carbon dioxide absorption amount of an acidic gas chemical absorption liquid. The graph which shows the temperature dependence of the concentration of an acidic gas chemical absorption liquid. The graph which shows the temperature dependence of the viscosity of an acidic gas chemical absorption liquid.

  The acid gas chemical absorption liquid of the present invention contains an ionic liquid consisting of a cation and an anion.

  The ionic liquid according to the present invention is a salt of liquid at 100 ° C. The ionic liquid used in the present invention is preferably a liquid, particularly at room temperature (25 ° C.). That is, the melting point of the ionic liquid according to the present invention is not particularly limited as long as it is 100 ° C. or less, but is preferably less than 50 ° C., and more preferably less than 25 ° C. The lower limit of the melting point of the ionic liquid according to the present invention is not particularly limited, but is preferably -100 ° C. or higher.

(Cation)
The cation constituting the ionic liquid according to the present invention is aminium having one or more primary or secondary amino groups, and an ethylenediamine or propylenediamine skeleton.

  Aminium is a cation represented by the following general structural formula (Formula 1).

ここで、Ｒ^１、Ｒ^２、Ｒ^３、Ｒ^４は、同種又は異種であってもよく、水素、又は無置換若しくは置換基を有する、飽和又は不飽和の、アルキル基若しくはヘテロアルキル基を表し、アルキル基及びヘテロアルキル基は、直鎖状又は環状であり、分岐鎖を有していてもよく、２つの基が結合し環を形成していてもよい。ヘテロアルキル基のヘテロ元素は、炭素元素及び水素元素以外であれば特に限定されず、窒素、酸素、硫黄などが挙げられ、遷移金属を除く元素、酸素を除く元素が好ましい。また、Ｒ^１、Ｒ^２、Ｒ^３、Ｒ^４は、その少なくとも１つが、置換基として１級又は２級アミノ基を有する。中でもＲ^１、Ｒ^２、Ｒ^３、Ｒ^４は、その少なくとも１つが、置換基として、１級アミノ基を有すると好ましく、１級アミノ基と、２級又は３級アミノ基を有するとより好ましい。
アミニウムとしては、１つの窒素原子に１つの炭素原子と３つの水素が結合した１級アミニウム、１つの窒素原子に２つの炭素原子と２つの水素が結合した２級アミニウム、１つの窒素原子に３つの炭素原子と１つの水素が結合した３級アミニウム、１つの窒素原子に４つの炭素原子が結合した４級アミニウムが挙げられるが、中でも、酸性ガス化学吸収液の酸性ガス、特に二酸化炭素の化学吸収性の点で、１級アミニウム、２級アミニウム、及び３級アミニウムが好ましい。

Here, R ¹ , R ² , R ³ and R ⁴ may be the same or different and each represents hydrogen or a saturated or unsaturated alkyl or heteroalkyl group having an unsubstituted or substituted group. The alkyl group and the heteroalkyl group may be linear or cyclic, and may have a branched chain, and two groups may combine to form a ring. The hetero element of the heteroalkyl group is not particularly limited as long as it is other than a carbon element and a hydrogen element, and nitrogen, oxygen, sulfur and the like can be mentioned, and elements other than transition metals and elements other than oxygen are preferable. Further, at least one of R ¹ , R ² , R ³ and R ⁴ has a primary or secondary amino group as a substituent. Among them, at least one of R ¹ , R ² , R ³ and R ⁴ preferably has a primary amino group as a substituent, and more preferably has a primary amino group and a secondary or tertiary amino group. .
As aminium, a primary aminium in which one carbon atom and three hydrogens are bonded to one nitrogen atom, a secondary aminium in which two carbon atoms and two hydrogens are bonded to one nitrogen atom, three to one nitrogen atom Three aminiums in which two carbon atoms and one hydrogen are bonded, and quaternary aminiums in which four carbon atoms are bonded to one nitrogen atom are mentioned. Among them, acid gas of acid gas chemical absorption liquid, especially carbon dioxide chemistry From the point of absorbency, primary aminium, secondary aminium and tertiary aminium are preferred.

  The ethylenediamine skeleton is a skeleton represented by the following general structural formula (Formula 2).

ここで、Ｒ^５、Ｒ^６、Ｒ^７、Ｒ^８は、同種又は異種であってもよく、水素、又は無置換又は置換基を有する、飽和又は不飽和の、アルキル基若しくはヘテロアルキル基を表し、アルキル基及びヘテロアルキル基は、直鎖状又は環状であり、分岐鎖を有していてもよく、２つの基が結合し環を形成していてもよい。ヘテロアルキル基のヘテロ元素は、炭素元素及び水素元素以外であれば特に限定されず、窒素、酸素、硫黄などが挙げられ、遷移金属を除く元素、酸素を除く元素が好ましい。
また、エチレンジアミン骨格のエチレン基の炭素原子は、置換基を有していてもよく、その置換基は、例えば、下記の一般構造式（式３）で表されるように、他の置換基と結合して環を形成していてもよい。

Here, R ⁵ , R ⁶ , R ⁷ and R ⁸ may be the same or different and each represents hydrogen or a saturated or unsaturated alkyl or heteroalkyl group having an unsubstituted or substituted group. The alkyl group and the heteroalkyl group may be linear or cyclic, and may have a branched chain, and two groups may combine to form a ring. The hetero element of the heteroalkyl group is not particularly limited as long as it is other than a carbon element and a hydrogen element, and nitrogen, oxygen, sulfur and the like can be mentioned, and elements other than transition metals and elements other than oxygen are preferable.
In addition, the carbon atom of the ethylene group of the ethylenediamine skeleton may have a substituent, and the substituent is, for example, as represented by the following general structural formula (Formula 3), other substituents and It may combine to form a ring.

  The aminium according to the present invention includes, for example, an aminium represented by the following general structural formula (Formula 4) in which a hydrogen cation is coordinated to a nitrogen atom of an ethylenediamine skeleton represented by the general structural formula (Formula 2) Can be mentioned.

  Specific examples of such aminium according to the present invention include alkyl ethylene diaminium represented by the following general structural formula (Formula 5).

ここで、Ｒ^９は、無置換又は置換基を有する、飽和又は不飽和の、アルキル基又はヘテロアルキル基を表し、アルキル基及びヘテロアルキル基は、直鎖状又は環状であり、分岐鎖を有していてもよい。ヘテロアルキル基のヘテロ元素は、炭素元素及び水素元素以外であれば特に限定されず、窒素、酸素、硫黄などが挙げられ、遷移金属を除く元素、酸素を除く元素が好ましい。
Ｒ^９は、好ましくは炭素数１〜１２の、無置換又は置換基を有する直鎖状アルキル基であり、より好ましくは炭素数４〜１０の、無置換又は置換基を有する直鎖状アルキル基、特に好ましくはヘキシル基、２−エチル−ヘキシル基である。

Here, R ⁹ represents an unsubstituted or substituted, saturated or unsaturated, alkyl group or heteroalkyl group, and the alkyl group and heteroalkyl group are linear or cyclic, and have a branched chain. It may be done. The hetero element of the heteroalkyl group is not particularly limited as long as it is other than a carbon element and a hydrogen element, and nitrogen, oxygen, sulfur and the like can be mentioned, and elements other than transition metals and elements other than oxygen are preferable.
R ⁹ is preferably a linear or unsubstituted alkyl group having 1 to 12 carbon atoms, and more preferably a linear or linear alkyl group having 4 to 10 carbon atoms. Particularly preferred are hexyl and 2-ethyl-hexyl.

  The propylene diamine skeleton is obtained by replacing the ethylene group of the ethylene diamine skeleton described above with a propylene group. Specifically, the ethylene group of the above-mentioned formula 2 is replaced with a propylene group. In addition, a carbon atom of a propylene group of a propylene diamine skeleton may have a substituent, and the substituent forms, for example, a ring bound to another substituent as represented by the above-mentioned Formula 3 It may be done.

  Moreover, as aminium which has a propylene diamine skeleton which concerns on this invention, the aminium which substituted ethylene group of above-mentioned Formula 4 to the propylene group is mentioned, for example. More specifically, alkyl propylene diaminium etc. which replaced the ethylene group of above-mentioned Formula 5 to the propylene group are mentioned.

  The cation constituting the ionic liquid according to the present invention is preferably polyethyleneaminium having a polyethyleneamine skeleton. Polyethylene aminium is represented, for example, by the following general structural formula (Formula 6).

ここで、Ｒ^１０、Ｒ^１１、Ｒ^１２、Ｒ^１３は、同種又は異種であってもよく、水素、若しくは無置換又は置換基を有する、飽和又は不飽和の、アルキル基若しくはヘテロアルキル基を表し、アルキル基及びヘテロアルキル基は、直鎖状若しくは環状であり、分岐鎖を有していてもよく、２つの基が結合し環を形成していてもよい。ｎは、１以上の整数を表す。ヘテロアルキル基のヘテロ元素は、炭素元素及び水素元素以外であれば特に限定されず、窒素、酸素、硫黄などが挙げられ、遷移金属を除く元素、酸素を除く元素が好ましい。ｎは、１、２、３、４のいずれかであると好ましく、１であるとより好ましい。ポリエチレンアミン骨格のエチレン基の炭素原子は、置換基を有していてもよく、他の置換基と結合して環を形成していてもよい。

Here, R ¹⁰ , R ¹¹ , R ¹² and R ¹³ may be the same or different, and represent hydrogen or a saturated or unsaturated alkyl group or heteroalkyl group having unsubstituted or substituted group. The alkyl group and the heteroalkyl group may be linear or cyclic, and may have a branched chain, and two groups may combine to form a ring. n represents an integer of 1 or more. The hetero element of the heteroalkyl group is not particularly limited as long as it is other than a carbon element and a hydrogen element, and nitrogen, oxygen, sulfur and the like can be mentioned, and elements other than transition metals and elements other than oxygen are preferable. n is preferably any one of 1, 2, 3 and 4, and more preferably 1. The carbon atom of the ethylene group of the polyethyleneamine skeleton may have a substituent, or may be combined with another substituent to form a ring.

  Examples of aminium having a polyethyleneamine skeleton include aminium in which a hydrogen cation is coordinated to at least one nitrogen atom of polyethyleneaminium represented by the general structural formula (Formula 6).

  As such aminium having a polyethyleneamine skeleton, aminium having a diethylenetriamine skeleton is preferable, and more specifically, for example, the following general structural formula (Formula 7), (Formula 8), or (Formula 9) And alkylethylenediaminium. Among them, alkyl ethylene diaminium represented by the general structural formula (Formula 7) is preferable.

In Formulas 7 to 9, R ¹⁴ represents an unsubstituted or substituted, saturated or unsaturated, alkyl group or heteroalkyl group, and the alkyl group is linear or cyclic and has a branched chain. It may be done. The hetero element of the heteroalkyl group is not particularly limited as long as it is other than a carbon element and a hydrogen element, and nitrogen, oxygen, sulfur and the like can be mentioned, and elements other than transition metals and elements other than oxygen are preferable. R ¹⁴ is preferably a substituted or unsubstituted linear alkyl group having 1 to 12 carbon atoms, more preferably an unsubstituted or substituted linear alkyl group, and still more preferably hexyl And 2-methyl-hexyl, particularly preferably 2-methyl-hexyl.

  Further, the cation constituting the ionic liquid according to the present invention is preferably polypropylene aminium having a polypropylene diamine skeleton. The polypropylene aminium is obtained by replacing the ethylene group of the above-mentioned formula 6 with a propylene group.

  Examples of the aminium having a polypropylene amine skeleton include aminium in which a hydrogen cation is coordinated to at least one nitrogen atom of polypropylene aminium in which the ethylene group of the above-mentioned Formula 6 is replaced by a propylene group.

  As such aminium having a polypropyleneamine skeleton, aminium having a dipropylenetriamine skeleton is preferable. Specifically, for example, the ethylene group of the above-mentioned formula 7, formula 8, or formula 9 is replaced by a propylene group Alkyl propylene diaminium is mentioned. Among them, alkylpropylenediaminium in which the ethylene group of Formula 7 is replaced with a propylene group is preferable.

  Moreover, it is preferable that the cation which comprises the ionic liquid concerning this invention has N- (2-aminoethyl) piperazine frame | skeleton. Examples of aminium having an N- (2-aminoethyl) piperazine skeleton include N- (2-aminoethyl) piperazinium represented by the following structural formula (Formula 10) or (Formula 11). Among them, N- (2-aminoethyl) piperazinium represented by (Formula 10) is preferable.

  The molecular weight of the cation according to the present invention is not particularly limited, but is preferably in the range of 75 to 346, more preferably in the range of 145 to 346, and particularly preferably in the range of 188 to 217. When the molecular weight of the cation is in this range, it is preferable in terms of acid gas absorbability and emission of the acid gas chemical absorption solution.

  Specific examples of these aminiums of cations constituting the ionic liquid contained in the acidic gas chemical absorption liquid of the present invention include hexylethylenediaminium, 2-ethylhexylethylenediaminium, N- (2-ethylhexyl) diethylenetriaminium, Examples thereof include hexyldiethylene triaminium, 2-ethylhexyl diethylene triaminium, N- (2-aminoethyl) piperazinium, and propylene diaminium. Among these, hexyl diethylene triaminium and N- (2-ethylhexyl) diethylene triaminium are more preferable.

(Anion)
The anion according to the present invention is not particularly limited as long as it forms an ionic liquid with the above-mentioned cation aminium, and examples thereof include an amide anion, a sulfonic acid anion, a carboxylic acid anion, and a phosphate anion A boric acid type anion, a carbonic acid type anion, and a halogen type anion are mentioned. Among these, amide based anions, sulfonic acid based anions, and carboxylic acid based anions are preferable. These anions can be used alone or in combination of two or more.

Examples of the amide type anion include (FSO ₂ ) ₂ N ⁻ , (FSO ₂ ) (CF ₃ SO ₂ ) N ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ , (CF ₃ SO ₂ ) (C ₂ F ₅ ) SO ₂ ) N ⁻ , (C ₂ F ₅ SO ₂ ) ₂ N ⁻ , (C ₄ F ₉ SO ₂ ) ₂ N ⁻ , (NC) ₂ N ^{− and the} like. Among them, (FSO ₂ ) ₂ N ⁻ and (CF ₃ SO ₂ ) ₂ N ⁻ are preferable.

Examples of the sulfonic acid-based anion, ^{_{e.g., CF 3 SO 3 -, CH}} 3 SO 3 -, CH 3 OSO 3 -, C 2 H 5 OSO 3 -, C 6 H 13 OSO 3 -, HOSO 3 - , and the like.

Examples of carboxylic acid anions include HCOO ⁻ , CH ₃ COO ⁻ , C ₂ H ₅ COO ⁻ , C ₃ H ₇ COO ⁻ , C ₄ H ₉ COO ⁻ , C ₅ H ₁₁ COO ⁻ , and C ₆ H ₁₃ COO. ⁻ , C ₇ H ₁₅ COO ⁻ , C ₈ H ₁₇ COO ⁻ , C ₉ H ₁₉ COO ⁻ , C ₁₀ H ₂₁ COO ⁻ , C ₁₁ H ₂₃ COO ⁻ , (CH ₃ ) ₂ CHCOO −, (CH ₃ ) ₃ CCOO −, C ₆ H ₅ COO ⁻ , CF ₃ COO ⁻ , C ₂ F ₅ COO ⁻ , C ₃ F ₇ COO ⁻ , C ₄ F ₉ COO ⁻ , C ₅ F ₁₁ COO ⁻ , C ₆ F ₁₃ COO ⁻ , _{^{C 7 F 15 COO -, C}} 8 F 17 COO -, C 9 F 19 COO -, C 10 F 21 COO -, C 11 F 23 COO - and the like. Among them, CH ₃ COO ⁻ , C ₂ H ₅ COO ⁻ , C ₃ H ₇ COO ⁻ , C ₄ H ₉ COO ⁻ , C ₅ H ₁₁ COO ⁻ , C ₆ H ₁₃ COO ⁻ , C ₇ H ₁₅ COO ⁻ , CF ₃ COO ⁻ is preferred.

As a phosphate type anion, for example, PF ₆ ⁻ , PF ₃ (CF ₃ ) ₃ ⁻ , PF ₃ (C ₂ F ₅ ) ₃ ⁻ , PF ₃ (C ₃ F ₇ ) ₃ ⁻ , PF ₃ (C ₄ F) ^{_{9) 3 -, (CH 3}} O) HPOO -, (C 2 H 5 O) HPOO -, (CH 3 O) 2 POO - include ^{_{-, (C 2 H 5 O}} ) 2 POO.
Examples of boric acid-based anions include BF ₄ ⁻ , BF ₃ (CF ₃ ) ⁻ , BF ₃ (C ₂ F ₅ ) ⁻ , BF ₃ (C ₃ F ₇ ) ⁻ , and BF ₃ (C ₄ F ₉ ) ^{−. _{, BF 2 (CF 3) 2}} -, BF 2 (C 2 F 5) 2 -, BF 2 (C 3 F 7) 2 -, BF 2 (C 4 F 9) 2 -, B (CN) 4 - is It can be mentioned.
The carbon acid anions such ^{_{as, (CF 3 SO 2) 3}} C -, (C 2 F 5 SO 2) 3 C - and the like.
The halogen-based anion, for ^{example, F -, Cl -, Br} -, I - , and the like.

  Each of these specific anions can be used in any combination with the specific cation described above.

  The molecular weight of the anion according to the present invention is not particularly limited, but is preferably in the range of 149 to 280. When the anion of the ionic liquid is in this range, it is preferable in terms of acid gas absorbability and emission of the acid gas chemical absorption solution.

(Ionic liquid)
The ionic liquid according to the present invention has, for example, one or more primary or secondary amino groups described above, and one or more primary or secondary amino groups corresponding to aminium having an ethylene diamine skeleton, and an ethylene diamine skeleton. It can be prepared by neutralization of an amino compound (cation precursor) and an acid having the above-mentioned anion as a conjugate base.

Preferred specific preparation conditions are as follows.
The cation precursor and the acid are neutralized in a stoichiometric ratio (1: 1) at 0 to 60 ° C., preferably 10 to 40 ° C. in an organic solvent. After the neutralization reaction is completed, the organic solvent is distilled off at 0 to 60 ° C, preferably 20 to 40 ° C. Thereby, the ionic liquid concerning the present invention can be obtained.

  The molecular weight of the ionic liquid according to the present invention is not particularly limited, but is preferably in the range of 294 to 626, and more preferably in the range of 337 to 497. When the molecular weight of the ionic liquid is in this range, it is preferable in terms of acid gas absorbability and emission of the acid gas chemical absorption solution.

As the ionic liquid according to the present invention, for example, hexylethylenediaminium bis (trifluoromethylsulfonyl) amide (abbreviation: [HexEDA] [Tf ₂ N]), hexylethylenediaminium trifluoromethanesulfonate (abbreviation: [HexEDA]) [CF ₃ SO ₃ ]), 2-ethylhexylethylenediaminium bis (trifluoromethylsulfonyl) amide (abbreviated: [EthexEDA] [Tf ₂ N]), 2-ethylhexylethylenediaminium trifluoromethanesulfonate (abbreviated: [EthexEDA) _{] [CF 3 SO 3])} , hexyl diethylene thoria mini um bis (trifluoromethylsulfonyl) amide (abbreviated _{as: [HexDETA] [Tf 2 N} ]), hexyl diethylene thoria mini ium trifluoro Tan sulfonate (abbreviated _{as: [HexDETA] [CF 3 SO} 3]), N- (2- ethylhexyl) diethylene thoria mini um bis (trifluoromethylsulfonyl) amide (abbreviated _{as: [EtHexDETA] [Tf 2 N} ]), N- ( 2-Ethylhexyl) diethylenetriaminium trifluoromethanesulfonate (abbreviation: [EtHexDETA] [CF ₃ SO ₃ ]), N- (2-aminoethyl) piperazinium bis (trifluoromethylsulfonyl) amide (abbreviation: [AmEtPipe] [Tf ₂ N]), and N- (2-aminoethyl) piperazinium trifluoromethanesulfonate (abbreviated: [AmEtPipe] [CF ₃ SO ₃ ]), propylenediaminium bis (trifluoromethylsulfonyl) amide (abbreviated: [PD A] [Tf ₂ N]) is preferable, and [HexDETA] [Tf ₂ N] and [EtHexDETA] [Tf ₂ N] are more preferable.

(Acid gas absorption liquid)
The acid gas chemical absorption liquid of the present invention contains the above-mentioned ionic liquid consisting of a cation and an anion. The ionic liquid can be used singly or in plurality, and can be diluted, for example, when the melting point of the main ionic liquid is higher than normal temperature (25 ° C.). As the diluent, the ionic liquid according to the present invention can also be used, and other ionic liquids composed of a cation and an anion generally referred to as ionic liquid, diethylene glycols, alcohols, water and the like can be mentioned. The use of ionic liquids or diethylene glycols is preferred in order to reduce the vapor pressure of the acid gas chemical absorption solution to suppress the loss due to volatilization.

  In addition, the acidic gas chemical absorption liquid of the present invention can contain other components as long as the present invention is not inhibited.

  The acidic gas chemical absorption liquid of the present invention is preferably capable of absorbing 0.5 to 1.0 mol of carbon dioxide per mole of the ionic liquid at 25 ° C. The acid gas chemical absorption liquid of the present invention is preferably capable of absorbing and emitting 0.3 mol of carbon dioxide per mol of ionic liquid at a temperature difference of 90 ° C., and it is preferably 0 per mol of ionic liquid at a temperature difference of 90 ° C. It is more preferable that 6 moles of carbon dioxide can be absorbed and released, and it is particularly preferable that 0.8 moles of carbon dioxide can be absorbed and released per mole of ionic liquid at a temperature difference of 90 ° C. In addition, as the ionic liquid, it is preferable to use an ionic liquid that can dissipate 80% or more of carbon dioxide absorbed at 25 ° C. in a temperature range of 100 ° C. or less. Here, the carbon dioxide absorption amount is measured by the method described later. The amount of absorption and the amount of emission can also be controlled by factors such as the series number and number of amino groups, solvation energy and the like. Moreover, the said ionic liquid can also be diluted and utilized according to the target acidic gas separation process. Diluents include ionic liquids, diethylene glycols, alcohols, water. The use of ionic liquids or diethylene glycols is preferred in order to reduce the vapor pressure of the absorbing solution and to control the loss due to volatilization. Here, the ionic liquids as a diluent include an ionic liquid comprising one or more primary or secondary amino groups according to the present invention, and a cation and an anion which is aminium having an ethylenediamine skeleton, or other ionic liquids. It is preferable to use other ionic liquids.

Specific examples of the diluent include 1-butyl-3-methylimidazolium bis (trifluoromethylsulfonyl) amide (abbreviation: [bmim] [Tf ₂ N]), tetraethylene glycol dimethyl ether (abbreviation: Tetra Glyme), 1 -Ethyl-3-methylimidizolium tetracyanoborate (abbreviation: [emim] [TCB]), 1-butyl-3-methylimidazolium trifluoromethanesulfonate (abbreviation: [bmim] [CF ₃ SO ₃ ]) And polyethylene glycol (molecular weight 400) (abbreviation: PEG 400) and the like. When the diluent is an ionic liquid, it is preferable that the diluent is composed of the same anion as the anion of the ionic liquid according to the present invention.

The combination and dilution ratio of the ionic liquid and the diluent according to the present invention are not particularly limited, but when the ionic liquid according to the present invention is [HexEDA] [Tf ₂ N], the diluent is [bmim] [Tf ₂ N] And the proportion is more preferably 3 to 5 parts by weight with respect to 1 part by weight of [HexEDA] [Tf ₂ N].

When the ionic liquid according to the present invention is [EtHexEDA] [Tf ₂ N], the diluent is preferably [bmim] [Tf ₂ N], Tetra Glyme, or [emim] [TCB], and the ratio is [EtHexEDA]. It is more preferable that it is 0.5 to 4 parts by weight, 0.5 to 4 parts by weight, and 0.5 to 4 parts by weight with respect to 1 part by weight of [Tf ₂ N].

If the ionic liquid according to the present invention is _{[HexDETA] [Tf 2 N]} , preferably the diluent is _{[bmim] [Tf 2 N]} , with respect to the proportion _{[HexDETA] [Tf 2 N]} 1 part by weight The amount is more preferably 0.5 to 4 parts by weight.

When the ionic liquid according to the present invention is [EtHexEDA] [Tf ₂ N], the diluent is preferably [bmim] [Tf ₂ N], and the ratio is 1 part by weight of [EtHexEDA] [Tf ₂ N] The amount is more preferably 0.5 to 4 parts by weight.

When the ionic liquid according to the present invention is [EtHexEDA] [CF ₃ SO ₃ ], the diluent is preferably [bmim] [CF ₃ SO ₃ ], and the ratio is 1 [EtHexEDA] [CF ₃ SO ₃ ] 1 weight It is more preferable that it is 0.5 to 4 parts by weight with respect to parts.

When the ionic liquid according to the present invention is [AmEtPipe] [Tf ₂ N], the diluent is preferably polyethylene glycol, and the molecular weight of the polyethylene glycol is more preferably 200 to 800, for example 400 (abbreviated: PEG 400) And the ratio is more preferably 0.5 to 4 parts by weight with respect to 1 part by weight of [AmEtPipe] [Tf ₂ N].

When the ionic liquid according to the present invention is [PDA] [Tf ₂ N], the diluent is preferably [bmim] [Tf ₂ N], and the ratio is preferably 1 part by weight of [PDA] [Tf ₂ N]. More preferably, it is 4 to 5 parts by weight.

The viscosity of the acidic gas chemical absorption liquid according to the present invention is not particularly limited, but the upper limit is preferably less than 2700 mPa · s at 25 ° C., and more preferably less than 500 mPa · s at 25 ° C. When the viscosity of the acid gas chemical absorption liquid is in this range, it is preferable in terms of acid gas absorbability and emission of the acid gas chemical absorption liquid. Although the density of the acid gas chemical absorbent according to the present invention is not particularly limited, the upper limit is preferably is less than 1.40 g / cm ³ at 25 ° C., is less than 1.35 g / cm ³ at 25 ° C. More preferable. When the viscosity and density of the acid gas chemical absorption liquid are in this range, it is preferable in terms of acid gas absorbability and emission of the acid gas chemical absorption liquid. The viscosity, density, and temperature dependence of the acid gas chemical absorption solution of the present invention can be adjusted by the type of cation and anion of the ionic liquid used and a diluent.

(Acid gas separation and recovery method)
Next, an acidic gas separation and recovery method using the acidic gas chemical absorption liquid of the present invention will be described.
The acid gas is absorbed into the acid gas chemical absorption liquid by bringing the acid gas chemical absorption liquid into contact with a mixed gas of two or more components containing the acid gas, and the acid gas is selected from the mixed gas. Separate.

  Examples of the acid gas include carbon dioxide, hydrogen sulfide, sulfur oxides, nitrogen oxides, inorganic acids (hydrochloric acid, nitric acid, sulfuric acid, sulfonic acid etc.), organic acids (phosphoric acid, carboxylic acid, carbonic acid etc), etc. Although a gas can be mentioned, the method for separating and recovering acid gas using the acid gas chemical absorption liquid of the present invention is particularly excellent in separating carbon dioxide. The mixed gas is not particularly limited as long as it is a gaseous mixture containing these acid gases. Also, the type and composition of the acid gas contained in the mixed gas are not particularly limited.

  In the acid gas separation and recovery method of the present invention, the temperature at which the acid gas is chemically absorbed by the ionic liquid contained in the acid gas chemical absorption solution is not particularly limited, but usually around room temperature (25 ° C. ± 10 ° C.) or It is below room temperature (25 ° C.). The contact method of the mixed gas and the acid gas chemical absorption liquid is not particularly limited as long as the acid gas is chemically absorbed by the acid gas chemical absorption liquid. For example, a method of bubbling a mixed gas in an acid gas chemical absorption liquid, a method of spraying an acid gas chemical absorption liquid on a mixed gas, a method of contacting a mixed gas with a material impregnated or gelled with an acid gas chemical absorption liquid, etc. Can be mentioned.

  The acid gas chemical absorption liquid which has absorbed the acid gas separates the mixed gas from the acid gas which has absorbed the acid gas, for example, and dissipates the acid gas by heating or / and depressurizing the separated acid gas chemical absorption liquid It can be reused by letting it play.

  When heating the acid gas chemical absorption liquid, the acid gas can be dissipated by setting the temperature condition 5 to 100 ° C. higher than the temperature at which the acid gas is absorbed. More preferably, when the acid gas is dissipated under a temperature condition of 100 ° C. or less, the regenerated energy of the acid gas chemical absorption liquid can be reduced, which is energy saving as compared with the prior art.

  When the acid gas chemical absorption liquid is decompressed, the acid gas can be dissipated by setting the pressure lower than the pressure at which the acid gas is absorbed, and the pressure can be set according to the target acid gas removal process. . The temperature at which the acid gas chemical absorption liquid is decompressed is not particularly limited, but is preferably the temperature at which the acid gas is absorbed, that is, around room temperature (25 ° C. ± 10 ° C.) or room temperature (25 ° C.) or less.

  The apparatus for regenerating the acid gas chemical absorption liquid is not particularly limited as long as the absorbed acid gas is dissipated and the ionic liquid in the acid gas chemical absorption liquid is regenerated.

  According to the acidic gas separation and recovery method of the present invention, the acidic gas removal efficiency of the process can be enhanced by using the ionic liquid having a large amount of absorption. Moreover, compared with the process using the conventional acidic gas chemical absorption liquid, the thermal energy required for reproduction | regeneration of an acidic gas chemical absorption liquid can be reduced. In addition, it is possible to construct a process that effectively utilizes low-grade waste heat of 100 ° C. or less that has not been used until now. Furthermore, by controlling the molecular structure and concentration of the ionic liquid contained in the acidic gas chemical absorption liquid, it is possible to provide an optimum separation process for the target acidic gas.

(Example)
Hereinafter, the present invention will be described based on examples, but the present invention is not limited to these examples. The measurement used the following measurement methods.
(1) NMR spectrum The ¹ H-NMR spectrum and the ¹³ C-NMR spectrum of the ionic liquid, the acidic gas chemical absorption liquid containing the ionic liquid, or those absorbing carbon dioxide are shown in Examples 7-1 and 7-2. The measurement was performed using a Bruker Ascend 400, and in the other examples, using a Varian Inova 300. Unless otherwise specified, the measurement temperature is 40 ° C., the solvent is benzene-d6, and the internal standard is tetramethylsilane (TMS).
(2) Viscosity and Density The viscosity and density of the ionic liquid or the acid gas chemical absorption liquid containing the ionic liquid were measured using an Anton Paar viscometer Stabinger SVM 3000.

(3) Carbon Dioxide Absorption Amount Measurement was performed at normal pressure using a carbon dioxide absorption test apparatus shown in FIG. The carbon dioxide absorption test apparatus includes a nitrogen or carbon dioxide bomb 1, a pressure reducing valve 2, a flow meter 3, a valve 4, a coiled heat exchanger 5, for introducing nitrogen or carbon dioxide into a glass reaction container 12. And a bulb 6, a constant temperature bath 8 for containing a heat medium 7, a resistance indicator 10 to which a platinum temperature measuring body 9 for measuring the temperature of the heat medium 7 in the constant temperature bath 8 is connected, a heat medium 7 in a constant temperature bath 8 And a magnetic stirrer 14 for rotating the rotor 13 placed in the glass reaction vessel 12.
A stopper 15, a gas inlet pipe 16, and a valved discharge pipe 17 can be attached to the reaction container 12. The valve 6 can be connected to a gas introduction pipe 16 attached to the reaction vessel 12. The coiled heat exchanger 5 and the reaction vessel 12 are immersed in the heat medium 7 of the constant temperature bath 8 and kept at a constant temperature by the constant temperature circulation device 11. A rotor 13 is placed in the reaction vessel 12, and the acidic gas chemical absorption solution in the reaction vessel 12 can be stirred by the magnetic stirrer 14.
Below, the carbon dioxide absorption measurement flow using this carbon dioxide absorption test device is described.
1) In a nitrogen atmosphere, a predetermined amount (about 10 cc) of an acid gas chemical absorbing solution is dispensed into a glass reaction vessel 12, and the mouth of the reaction vessel 12 is sealed with a stopper 15. The mass of the entire reaction vessel is measured with an analytical balance, from which the mass of the tare (reaction vessel 12 and plug 15) is subtracted to obtain the mass W ₁ of the acid gas chemical absorption liquid.
2) Attach the gas introduction pipe 16 and the discharge pipe 17 to the reaction vessel 12 and measure the mass again to obtain the mass W ₂ of the entire reaction vessel.
3) Place the reaction vessel 12 in the thermostatic water tank 7. The gas inlet pipe 16 is connected to the valve 5.
4) The temperature of the thermostatic bath 8 is maintained at 40 ° C., only nitrogen is caused to flow through the reaction vessel 12, and the inside of the vessel is replaced with nitrogen. The mass of the entire reaction vessel is measured with an analytical balance at regular intervals (for example, 60 minutes). When the mass change of each measurement is equal to or less than 0.001 g, the mass of the entire reaction vessel and W _3.
5) Subsequently, carbon dioxide is caused to flow through the reaction vessel 12 to absorb the carbon dioxide in the acid gas chemical absorption liquid. The mass of the entire reaction vessel is measured with an analytical balance at regular intervals (for example, 120 minutes to overnight). The mass of the entire reaction vessel is W ₄ when the mass change for each measurement is 0.001 g or less.
6) The mass W _CO2 of carbon dioxide absorbed in the acid gas chemical absorption liquid is determined based on the following equation.
W _CO2 = W ₄ -W ₃
Further, the carbon dioxide absorption amount per 1 mol of ionic liquid in the acidic gas chemical absorption liquid X _CO2 is determined based on the following formula.
X _CO2 = (W _CO2 / M _CO2 ) / (W ₁ / M _IL )
Here, in the above formula, M _CO2 is the molecular weight of carbon dioxide, and M _IL is the molecular weight of the ionic liquid.
7) The temperature of the thermostatic bath is appropriately changed, and the operations and analysis of the above 1) to 6) are performed to determine the carbon dioxide absorption amount at each temperature. Thereafter, the mass of carbon dioxide absorbed at 40 ° C. is measured again to confirm reproducibility. In addition, diluents, such as ionic liquid itself other than the ionic liquid which concerns on this invention used in the Example, hardly absorb carbon dioxide under normal pressure.
(4) Melting point The melting point of the ionic liquid was measured using a Bruker differential scanning calorimeter DSC3200SA.

Example 1-1
1) Synthesis of hexyl ethylene diaminium bis (trifluoromethyl sulfonyl) amide 300 g of ethylene diamine and 230 g of ethanol were mixed to obtain an ethanol solution of ethylene diamine. To the resulting ethanol solution of ethylene diamine, 120 g of chlorohexane was dropped at a rate of 1 drop every 5 seconds at room temperature. After completion of the dropwise addition, the reaction mixture was stirred at room temperature for 1 week to obtain a reaction mixture containing hexyl ethylene diaminium chloride. To the resulting reaction mixture, 110 g of a 40 wt% aqueous sodium hydroxide solution was added to neutralize hexylethylenediaminium chloride. Only the organic phase was recovered, and 80 g of hexyl ethylenediamine was obtained by atmospheric pressure distillation and vacuum distillation. The obtained hexyl ethylenediamine 52g was mixed with 80 g of methanol to obtain a methanol solution. In a nitrogen-replaced glove box, 140 g of a methanol solution (70 wt%) of bis (trifluoromethylsulfonyl) amic acid was dropped to the obtained methanol solution. Thereafter, the solvent was distilled off by drying under reduced pressure to obtain 150 g of hexylethylenediaminium bis (trifluoromethylsulfonyl) amide (abbreviation: [HexEDA] [Tf ₂ N]). The structural formula of [HexEDA] [Tf ₂ N] is shown in Formula 12, and the NMR spectrum is shown in FIG.

2) Using 4.6 g of the ionic liquid [HexEDA] [Tf ₂ N] as the acidic gas chemical absorption solution E1-1, the carbon dioxide absorption amount at a partial pressure of carbon dioxide (P _{2 CO 2} ) of 0.10 MPa was measured. The results are shown in Table 1. The viscosity of the acidic gas chemical absorption solution E1-1 was 456 mPa · s at 25 ° C. The temperature change of the viscosity of the acidic gas chemical absorption solution E1-1 is shown in FIG. 33, and the measurement result of the density is shown in FIG. 32 (reference numeral: rhombus). The NMR spectrum of acid gas chemical absorption solution E1-1 after CO ₂ absorption is shown in FIG.

(Example 1-2)
An ionic liquid [HexEDA] [Tf ₂ N] 4.6 g obtained in the same manner as in Example 1-1 was treated with 1-butyl-3-methylimidazolium bis (trifluoromethylsulfonyl) amide (abbreviated: [bmim] [ It was dissolved in 18.4 g of Tf ₂ N] to make an acid gas chemical absorption solution E1-2, and the carbon dioxide absorption amount at a partial pressure of carbon dioxide (P _{2 CO 2} ) of 0.10 MPa was measured. The results are shown in Table 1. Acidic gas chemical absorption solution E1-2 absorbs 0.82 mol of carbon dioxide per mol of ionic liquid at 25 ° C. and 0.14 mol of carbon dioxide at 100 ° C., and absorbs carbon dioxide absorbed at around room temperature It dissipates 83% of it at 100 ° C. The NMR spectrum of the acid gas chemical absorption solution E1-2 before absorption of CO ₂ is shown in FIG. 4, and the NMR spectrum of the acid gas chemical absorption solution E1-2 after absorption of CO ₂ is shown in FIG. The spectrum shape of ¹ H-NMR changes, and a peak derived from CO ₂ is detected in the ¹³ C-NMR spectrum, which indicates that CO ₂ and [HexEDA] [Tf ₂ N] have chemically reacted.

(Example 2-1)
1) Synthesis of N- (2-ethylhexyl) diethylene triaminium bis (trifluoromethylsulfonyl) amide 360 g of diethylene triamine and 160 g of ethanol were mixed to obtain an ethanol solution of ethylene diamine. To the resulting ethylene diamine solution in ethanol, 135 g of 1-bromo-2-ethylhexane was dropped at a rate of 1 drop in 5 seconds at room temperature. After completion of the dropwise addition, the reaction mixture was stirred at room temperature for 1 week to obtain a reaction mixture containing N- (2-ethylhexyl) diethylene triaminium bromide. To the resulting reaction mixture, 110 g of a 40 wt% aqueous sodium hydroxide solution was added to neutralize N- (2-ethylhexyl) diethylene triaminium bromide. Only the organic phase was recovered, and 70 g of toluene, 65 g of butanol and 400 g of distilled water were added to the recovered organic phase, and the mixture was further separated to recover only the organic phase. Atmospheric distillation and vacuum distillation of the recovered organic phase were carried out to obtain 30 g of N- (2-ethylhexyl) diethylene triamine. 20 g of N- (2-ethylhexyl) diethylene triamine was mixed with 40 g of methanol to obtain a diethyl ether solution. In a nitrogen-substituted glove box, 45 g of a diethyl ether solution (60 wt%) of bis (trifluoromethylsulfonyl) amic acid was dropped to the obtained diethyl ether solution. Thereafter, the solvent was distilled off by drying under reduced pressure to obtain 40 g of N- (2-ethylhexyl) diethylene triaminium bis (trifluoromethylsulfonyl) amide (abbreviation: [EtHexDETA] [Tf ₂ N]). The structural formula of [EtHexDETA] [Tf ₂ N] is shown in Formula 13.

2) ionic liquids [EtHexDETA] a _[Tf 2 N] as an acid gas chemical absorption liquid _E2-1, was measured carbon dioxide absorption amount of P CO2 = 0.10 MPa. Table 1 shows the results of measuring the carbon dioxide absorption amount of the acidic gas chemical absorption solution E2-1. The viscosity of the acidic gas chemical absorption solution E2-1 was 2660 mPa · s at 25 ° C. The temperature change of the viscosity of the acidic gas chemical absorption liquid E2-1 is shown in FIG. 33, and the measurement result of the density is shown in FIG. 32 (symbol: square). Acidic gas chemical absorption solution E2-1 absorbs 0.65 moles of carbon dioxide per mole of ionic liquid at 61.2 ° C., and absorbs 0.15 moles of carbon dioxide at 100.7 ° C., at 60 ° C. 77% of absorbed carbon dioxide is emitted at 100 ° C. The NMR spectrum of acid gas chemical absorption solution E2-1 after CO ₂ absorption is shown in FIG. The same change as that of the acid gas chemical absorption solution E1-2 was observed, indicating that CO ₂ was chemically absorbed by [EtHexDETA] [Tf ₂ N].

(Example 2-2)
5 g of [EtHexDETA] [Tf ₂ N] obtained in the same manner as in Example 2-1 was dissolved in 4.2 g of [bmim] [Tf ₂ N] to obtain an acidic gas chemical absorption solution E2-2, and P _CO2 The carbon dioxide absorption at 0.10 MPa was measured. The measurement results are shown in Table 1. The NMR spectrum of the acid gas chemical absorption solution E2-2 before absorption of CO ₂ measured at 60 ° C. using acetonitrile-d3 as a solvent is shown in FIG. 6, and the NMR spectrum of the acid gas absorption liquid E2-2 after CO ₂ absorption is measured. It is shown in FIG.

There is almost no difference in the carbon dioxide absorption amount of the acid gas chemical absorption solution E2-2 and the acid gas chemical absorption solution E2-1, and the influence of the dilution by [bmim] [Tf ₂ N] on the carbon dioxide absorption amount is recognized It was not done. The acidic gas chemical absorption liquid of the present invention can be used without changing the acidic gas chemical absorption performance even under the dilution conditions of the ionic liquid according to the present invention.

(Example 2-3)
2.9 g of [EtHexDETA] [Tf ₂ N] obtained in the same manner as in Example 2-1 is dissolved in 5.1 g of tetraethylene glycol dimethyl ether (abbreviation: Tetra Glyme) to prepare an acidic gas chemical absorption solution E2-3. The carbon dioxide absorption amount at P _CO2 = 0.10 MPa was measured. The measurement results are shown in Table 1. The NMR spectrum of the acid gas chemical absorption solution E2-2 before CO ₂ absorption is shown in FIG. 8, and the NMR spectrum of the acid gas chemical absorption solution E2 ₂ after CO ₂ absorption is shown in FIG.

(Example 2-4)
3.1 g of [EtHexDETA] [Tf ₂ N] obtained in the same manner as in Example 2-1 was treated with 1-ethyl-3-methylimidazolyl tetracyanoborate (abbreviation: [emim] [TCB]). It was dissolved in 4g, and acid gas chemical absorption liquid _E2-4, was measured carbon dioxide absorption amount of P CO2 = 0.10 MPa. The measurement results are shown in Table 1.

Example 3-1
1) Synthesis of hexyldiethylenetriaminium bis (trifluoromethylsulfonyl) amide In the same manner as in Example 2 except that 85 g of chlorohexane was used instead of 135 g of 1-bromo-2-ethylhexane, Fluoromethylsulfonyl) amide (abbreviated: [HexDETA] [Tf ₂ N]) was obtained. The structural formula of [HexDETA] [Tf ₂ N] is shown in Formula 14.

2) The ionic liquid [HexDETA] _[Tf 2 N] and acid gas chemical absorption liquid _E3-1, was measured carbon dioxide absorption amount of P CO2 = 0.10 MPa. The results are shown in Table 1.

(Example 3-2)
7.6 g of an ionic liquid [HexDETA] [Tf ₂ N] obtained in the same manner as in Example 3-1 was dissolved in 6.8 g of [bmim] [Tf ₂ N] to obtain an acidic gas chemical absorption solution E3-2. The carbon dioxide absorption amount at P _CO2 = 0.10 MPa was measured. The results are shown in Table 1. It absorbs 0.62 moles of carbon dioxide per mole of ionic liquid at 61.3 ° C., 0.12 moles of carbon dioxide at 100.9 ° C., and approximately 80% of the carbon dioxide absorbed at 60 ° C. It dissipates at ° C. Since the amount of carbon dioxide absorption increases as the temperature decreases, the emission rate when compared at around room temperature is further increased.

Example 4-1
1) Synthesis of N- (2-ethylhexyl) ethylenediaminium bis (trifluoromethylsulfonyl) amide The same as Example 1-1 except that 193 g of 1-bromo-2-ethyl hexane was used instead of 120 g of chlorohexane. Te, N-(2-ethylhexyl) ethylene Zia mini ium bis (trifluoromethylsulfonyl) amide (abbreviated _{as: [EtHexEDA] [Tf 2 N} ]) was obtained 130 g. The structural formula of [HexEDA] [Tf ₂ N] is shown in Formula 15, and the NMR spectrum is shown in FIG.

2) The ionic liquid _{[EtHexEDA] [Tf 2 N]} 8.7g and acid gas chemical absorption liquid E4-1, was measured carbon dioxide absorption amount at a partial pressure _(P CO2) 0.10 MPa of carbon dioxide. The results are shown in Table 1. The NMR spectrum of acid gas chemical absorption solution E4-1 after CO ₂ absorption measured at 40 ° C. is shown in FIG. 11, and the NMR spectrum of acid gas chemical absorption solution E 4-1 after CO ₂ absorption measured at 60 ° C. is shown in FIG. Indicate.

(Example 4-2)
Example 4-1 ionic liquids _[EtHexEDA] obtained in the same manner as [Tf 2 N] 4.6g of 1-butyl-3-methylimidazolium bis (trifluoromethylsulfonyl) amide (abbreviated as: [bmim] [ It was dissolved in 18.4 g of Tf ₂ N] to make an acid gas chemical absorption solution E4-2, and the carbon dioxide absorption amount at a partial pressure of carbon dioxide (P _{2 CO 2} ) of 0.10 MPa was measured. The results are shown in Table 1. The NMR spectrum of the acid gas chemical absorption solution E4-2 before absorption of CO ₂ is shown in FIG. 13, and the NMR spectrum of the acid gas absorption solution E4-2 after absorption of CO ₂ is shown in FIG.

(Example 5-1)
1) Synthesis of N- (2-ethylhexyl) ethylenediaminium trifluoromethanesulfonate By using 193 g of 1-bromo-2-ethylhexane instead of 120 g of chlorohexane and trifluoromethane instead of bis (trifluoromethylsulfonyl) amic acid In the same manner as in Example 1-1 except that a sulfonic acid was used, 45 g of N- (2-ethylhexyl) ethylenediaminium trifluoromethanesulfonate (abbreviation: [EtHexEDA] [CF ₃ SO ₃ ]) was obtained. The structural formula of [EtHexEDA] [CF ₃ SO ₃ ] is shown in Formula 16 and the NMR spectrum is shown in FIG.

2) The ionic liquid _{[EtHexEDA] [CF 3 SO 3} ] 6g and acid gas chemical absorption liquid E5-1, was measured carbon dioxide absorption amount at a partial pressure _(P CO2) 0.10 MPa of carbon dioxide. The results are shown in Table 1. The NMR spectrum of the acid gas chemical absorption solution E5-1 after CO ₂ absorption measured at 60 ° C. is shown in FIG.

(Example 5-2)
4 g of an ionic liquid [EtHexEDA] [CF ₃ SO ₃ ] obtained in the same manner as in Example 5-1 was combined with 1-butyl-3-methylimidazolium trifluoromethanesulfonate (abbreviation: [bmim] [CF ₃ SO ₃ ] 2.) It was dissolved in 14.3 g to make an acid gas chemical absorption solution E5-2, and the carbon dioxide absorption amount at a partial pressure of carbon dioxide (P _CO2 ) of 0.10 MPa was measured. The results are shown in Table 1. The NMR spectrum of the acid gas chemical absorption solution E5-2 before CO ₂ absorption is shown in FIG. 17, and the NMR spectrum of the acid gas chemical absorption solution E 5-2 after CO ₂ absorption is shown in FIG.

(Example 6)
1) Synthesis of N- (2-aminoethyl) piperazinium bis (trifluoromethylsulfonyl) amide 25.84 g of N- (2-aminoethyl) piperazine is mixed with 51.68 g of methanol, to which bis (trifluoromethylsulfonyl) is added 1) 168.70 g of a solution of amic acid in methanol (33.0 wt%) was dropped at a rate of 1 drop in 5 seconds under an argon atmosphere with an ice bath. After completion of the dropwise addition, the mixture was stirred at room temperature for 12 hours to obtain a methanol solution containing N- (2-aminoethyl) piperazinium bis (trifluoromethylsulfonyl) amide. Then, methanol was distilled off by drying under reduced pressure, and 78.79 g of the obtained crude N- (2-aminoethyl) piperazinium bis (trifluoromethylsulfonyl) amide was dissolved in 157.57 g of ethanol. After purification by column chromatography (activated alumina), ethanol is removed by drying under reduced pressure, and 49.64 g of N- (2-aminoethyl) piperazinium bis (trifluoromethylsulfonyl) amide (abbreviation: [AmEtPipe] [Tf ₂ N]) is obtained. I got The structural formula of [AmEtPipe] [Tf ₂ N] is shown in Formula 17, and the NMR spectrum of a solution of [AmEtPipe] [Tf ₂ N] in polyethylene glycol (molecular weight 400) (abbreviated: PEG 400) is shown in FIG.

2) Since the ionic liquid [AmEtPipe] [Tf ₂ N] was solid at room temperature, 5.09 g of [AmEtPipe] [Tf ₂ N] was dissolved in 9.748 g of PEG 400 to form an acidic gas chemical absorption solution E6, and P _{CO 2} The carbon dioxide absorption at 0.10 MPa was measured. The results are shown in Table 1. It absorbs 0.50 moles of carbon dioxide per mole of ionic liquid at 25 ° C. and 0.29 moles of carbon dioxide at 59.9 ° C., and 42% of carbon dioxide absorbed near room temperature is 59.9 ° C. It was The NMR spectrum of acid gas chemical absorption solution E6 after CO ₂ absorption is shown in FIG. The shape of the NMR spectrum was changed before and after CO ₂ absorption.

(Example 7)
1) Synthesis of Propylenediaminium Bis (trifluoromethylsulfonyl) amide A mixture of 7.8 g of propylenediamine with 15 ml of methanol was mixed with 45.5 g of a solution of bis (trifluoromethylsulfonyl) amic acid in methanol (65 wt%), While dropping in an ice bath, the solution was dropped at a rate of 1 drop in 5 seconds. After completion of the dropwise addition, the mixture was stirred at room temperature for 12 hours to obtain a methanol solution containing propylenediaminium bis (trifluoromethylsulfonyl) amide. Thereafter, methanol was distilled off by vacuum drying to obtain propylene diaminium bis (trifluoromethylsulfonyl) amide (abbreviated: [PDA] [Tf ₂ N]). The structural formula of [PDA] [Tf ₂ N] is shown in Formula 18, and the NMR spectrum of the [bmim] [Tf ₂ N] solution of [PDA] [Tf ₂ N] is shown in FIG.

2) The ionic liquid [PDA] [Tf ₂ N] was solid at room temperature, so 2.0 g of [PDA] [Tf ₂ N] was dissolved in 9.5 g of [bmim] [Tf ₂ N] to obtain acid gas chemistry. The absorption liquid E7 was used, and the carbon dioxide absorption amount at P _CO2 = 0.10 MPa was measured. The results are shown in Table 1. It absorbs 0.64 moles of carbon dioxide per mole of ionic liquid at 25 ° C and 0.09 moles of carbon dioxide at 100 ° C, and dissipates 86% of the carbon dioxide absorbed at around room temperature at 100 ° C. The The NMR spectrum of the acid gas chemical absorption solution E7 after CO ₂ absorption is shown in FIG. The shape of the NMR spectrum was changed before and after CO ₂ absorption.

(Comparative example 1)
1) Synthesis of piperazinium bis (trifluoromethylsulfonyl) amide 17.23 g of piperazine is mixed with 34.46 g of methanol, to which 168.70 g of methanol solution (33.0 wt%) of bis (trifluoromethylsulfonyl) amic acid is added. With an ice bath, the solution was dropped at a rate of 1 drop in 5 seconds under an argon atmosphere. After completion of the dropwise addition, the mixture was stirred at room temperature for 12 hours to obtain a methanol solution containing piperazinium bis (trifluoromethylsulfonyl) amide. Thereafter, methanol was distilled off by vacuum drying, and 71.99 g of the obtained crude piperazinium bis (trifluoromethylsulfonyl) amide was dissolved in 144.00 g of ethanol. After purification by column chromatography (activated alumina), ethanol was removed by drying under reduced pressure to obtain 41.75 g of piperazinium bis (trifluoromethylsulfonyl) amide (abbreviated: [Pipe] [Tf ₂ N]). The structural formula of [Pipe] [Tf ₂ N] is shown in Formula 18, and the NMR spectrum of the polyethylene glycol solution of [Pipe] [Tf ₂ N] is shown in FIG.

2) The ionic liquid [Pipe] [Tf ₂ N] was solid at room temperature, so 2.295 g of [Pipe] [Tf ₂ N] was dissolved in 10.002 g of polyethylene glycol (molecular weight 400) to obtain acid gas chemical absorption. Liquid R1 was used, and the carbon dioxide absorption amount at P _CO2 = 0.10 MPa was measured. The results are shown in Table 1. The acid gas chemical absorption solution R1 absorbed 0.27 moles of carbon dioxide per mole of ionic liquid at 24.9 ° C. and 0.07 moles of carbon dioxide at 60.0 ° C. The NMR spectrum of acid gas chemical absorption solution R1 after CO ₂ absorption is shown in FIG.

(Comparative example 2)
1) Synthesis of 2-methylpiperazinium bis (trifluoromethylsulfonyl) amide 20.03 g of 2-methylpiperazine is mixed with 40.10 g of methanol, and a methanol solution of bis (trifluoromethylsulfonyl) amic acid (33) 0. 0 wt%) 168.70 g was added dropwise at a rate of 1 drop in 5 seconds under an argon atmosphere with an ice bath. After completion of the dropwise addition, the mixture was stirred at room temperature for 12 hours to obtain a methanol solution containing 2-methylpiperazinium bis (trifluoromethylsulfonyl) amide. Thereafter, methanol was distilled off by vacuum drying, and 73.97 g of the obtained crude 2-methylpiperazinium bis (trifluoromethylsulfonyl) amide was dissolved in 148.00 g of ethanol. After purification by column chromatography (activated alumina), ethanol was removed by drying under reduced pressure to obtain 40.68 g of 2-methylpiperazinium bis (trifluoromethylsulfonyl) amide (abbreviation: [MePipe] [Tf ₂ N]). . The structural formula of [MePipe] [Tf ₂ N] is shown in Formula 19, and the NMR spectrum of the polyethylene glycol solution of [MePipe] [Tf ₂ N] is shown in FIG.

2) [MePipe] [Tf ₂ N] was solid at room temperature, so 2.383 g of [MePipe] [Tf ₂ N] was dissolved in 9.999 g of polyethylene glycol (molecular weight 400) to obtain acid gas chemical absorption solution R2 The carbon dioxide absorption amount at P _CO2 = 0.10 MPa was measured. The results are shown in Table 1. The acidic gas chemical absorption solution R2 absorbed 0.13 mole of carbon dioxide per mole of ionic liquid at 25 ° C. and 0.06 mole of carbon dioxide at 60.0 ° C. The NMR spectrum of the acid gas chemical absorption solution R2 after CO ₂ absorption is shown in FIG.

(Comparative example 3)
A known chemical absorption ionic liquid 1-ethyl-3-methylimidazoyl acetate (abbreviation: [emim] [ace]) having acetic acid as an anion was used as an acid gas chemical absorption solution R3. The structural formula of [emim] [ace] is shown in Formula 20. The carbon dioxide absorption amount of _P CO2 = 0.10 MPa acid gas chemical absorption liquid R3 was measured. The results are shown in Table 1.

The viscosity of the acidic gas chemical absorption solution R1 was 106 mPa · s at 25 ° C. The temperature change of the viscosity of the acidic gas chemical absorption solution E1-2 is shown in FIG. 33, and the measurement result of the density is shown in FIG. 32 (symbol: triangle). Acid gas chemical absorption liquid R3 is, _{X CO2} at 25 ° C. is _{X CO2} is 0.11 at 0.31,100 ℃, were dissipate 64% of carbon dioxide absorbed in the vicinity of room temperature at 100 ° C..

In FIG. 27 to FIG. 31, the acid gas chemical absorption solutions E1-1 to E7 (Examples 1-1 to 7) and the acid gas chemical absorption solutions R1 to R3 (Comparative Examples 1 to 3) at P _CO2 = 0.10 MPa The temperature dependence of carbon dioxide absorption amount X _CO2 per mole of ionic liquid is shown. [HexEDA] [Tf ₂ N] having one primary amine, [EtHex DETA] [Tf ₂ N] having one primary amine and one secondary amine, having one primary amine and one tertiary amine [ All X _CO2 at 25 ° C. of AmEtPipe] [Tf ₂ N] is 0.5 or more. On the other hand, having one secondary amine [Pipe] _[Tf 2 N] and [MePipe] _[Tf 2 N] is _{X CO2} at 25 ° C. is 0.3 or less. Therefore, by using a primary amine and a polyethylene amine skeleton, it is possible to provide an acidic gas chemical absorption solution having an _XCO2 of 0.5 or more.
In particular, the carbon dioxide absorption amount and emission amount of the acid gas chemical absorption liquid (Examples 1-2, 2-2, 2-3, 4-2, 5-2) according to the present invention are compared with the existing ionic liquid. Are very good. The above results show that the efficiency of acid gas removal can be improved by improving the amount of acid gas absorption, and 80% or more of carbon dioxide can be dissipated with low temperature waste heat of 100 ° C or less, and energy consumption related to acid gas removal can be reduced. It shows.

(In Table 1, T / ° C. indicates the temperature of the thermostatic chamber at the time of carbon dioxide absorption measurement, and X _{CO 2} indicates the carbon dioxide absorption per mole of the ionic liquid according to the present invention.)

  The acid gas chemical absorption liquid of the present invention contains an ionic liquid which is excellent in acid gas absorption near room temperature, and which can dissipate most of the absorbed acid gas at 100 ° C. or less. In addition, the acid gas separation and recovery method using this acid gas chemical absorption liquid improves the acid gas removal efficiency of the process of selectively separating acid gas such as carbon dioxide, and further reduces the energy consumption of the whole process. Possible and solve the problems of the prior art. Therefore, the present invention is, for example, separation of acid gas contained in exhaust gas from chemical plants and steel mills, production of energy resources (natural gas, biogas, synthesis gas) by decarboxylation, dispersion-type emissions from automobiles, etc. Sources such as NOx removal and maintenance of living environment (management of carbon dioxide concentration) can be used from the industrial sector to the consumer sector, but are not limited to these exemplified fields.

Reference Signs List 1 nitrogen or carbon dioxide cylinder 2 pressure reducing valve 3 flow meter 4 valve 5 heat exchanger 6 valve 7 heat medium 8 constant temperature bath 9 platinum temperature measuring body 10 resistance display 11 constant temperature circulating device 12 reaction container 13 rotor 14 magnetic stirrer 15 plug 16 gas introduction pipe 17 discharge pipe

Claims (8)

Ri cations and anions Tona, comprising an ionic liquid having a melting point Ru der below 50 ° C.,
The anion is at least one selected from the group consisting of an amide anion and CF ₃ SO ₃ ⁻ ,
The cation has one or more primary or secondary amino groups, and an ethylenediamine or propylenediamine skeleton,
In the ethylenediamine or propylenediamine skeleton, at least one nitrogen atom in the skeleton is a primary or secondary amino group, and at least one nitrogen atom in the skeleton is aminium to which a hydrogen cation is bound,
The carbon dioxide chemical absorption liquid, wherein the hetero element in the cation is an element other than carbon, hydrogen and oxygen. The carbon dioxide chemical absorption liquid according to claim 1, wherein the cation has a tertiary amino group. Wherein ethylenediamine or propylenediamine backbone is polyethylene diamine or polypropylene diamine skeleton, carbon dioxide chemical absorption liquid according to claim 1 or 2. The polyethylene diamine or polypropylene diamine skeleton, diethylenetriamine skeleton or N-(2-aminoethyl) piperazine skeleton, carbon dioxide chemical absorption liquid as claimed in claim 3. Carbon dioxide chemical absorption liquid according to any one of claims 1 to 4 and the carbon dioxide is absorbed into the carbon dioxide chemical absorption liquid by contacting a mixed gas containing carbon dioxide, said from the mixed gas A carbon dioxide separation and recovery method comprising selectively separating carbon dioxide . Carbon dioxide chemical absorbent that has absorbed carbon dioxide, by dissipating the carbon dioxide by a high temperature from the temperature collected at the time of absorption, further comprising regenerating said carbon dioxide chemical absorption liquid, in claim 5 Carbon dioxide separation recovery method described. The carbon dioxide chemical absorption solution that has absorbed carbon dioxide is heated to a temperature higher than the temperature at absorption and 100 ° C. or less, and 80% or more of the absorbed carbon dioxide is released and recovered, and the carbon dioxide chemical absorption solution is The method for carbon dioxide separation and recovery according to claim 6 , comprising regenerating. Absorbing carbon dioxide by reducing the pressure of the carbon dioxide chemical absorption solution containing, absorbed by carbon dioxide dissipates recovered involves playing carbon dioxide chemical absorption liquid, the carbon dioxide separation according to claim 5 Recovery method.

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