JP2017104776A - Carbon dioxide absorption liquid and separation and recovery method of carbon dioxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carbon dioxide absorption liquid where an absorption amount in the vicinity of room temperature is large in comparison with a conventional amine aqueous solution, easy-desorption property at a high temperature is excellent, the evaporation loss of an absorption liquid is small, specific heat is low, reaction heat is small, and energy required for the regeneration of the carbon dioxide absorption liquid per recovered carbon dioxide can be reduced.SOLUTION: Carbon dioxide absorption liquid includes a carbon dioxide chemical absorption amine being non-aqueous and recoverable at a high temperature and having a nitrogen-hydrogen bond and a tertiary amine solvent not having the nitrogen-hydrogen bond. The tertiary amine solvent not having the nitrogen-hydrogen bond is a polydentate amine being rich in hydrogen bond acceptability, being conformationally stable, having an oxygen atom and/or a nitrogen atom through a hydrocarbon group having a carbon number of a main chain of 2 or more so that a reaction between the amine having the nitrogen-hydrogen bond and carbon dioxide is accelerated and the total of the oxygen atom and the nitrogen atom is 2 or more.SELECTED DRAWING: None

Description

  The present invention relates to a carbon dioxide absorbing solution and a carbon dioxide separation and recovery method.

  In the separation and recovery of acidic gases such as carbon dioxide and hydrogen sulfide, a chemical absorption method using an aqueous solution of an amine compound as an absorbing solution has been put into practical use. In this chemical absorption process, a gas containing an acid gas is brought into contact with an absorption liquid at room temperature in an absorption tower, and the acid gas is selectively absorbed into the absorption liquid to cause a gas with a reduced acid gas concentration. The absorption liquid that has absorbed the acid gas is separated into gas and liquid, and the absorption liquid that has absorbed the acid gas is heated in the regeneration tower to dissipate and collect the acid gas. At the same time, the absorption liquid is regenerated and circulated. Use.

  However, in such a carbon dioxide separation and recovery method using an amine aqueous solution, it is necessary to increase the temperature of the absorption liquid in order to recover the carbon dioxide in the regeneration tower and regenerate the absorption liquid, resulting in a significant increase in energy consumption. Various studies have been conducted to solve such problems.

For example, Patent Document 1 describes a method of circulating CO ₂ from a gas stream, which includes contacting the gas stream with an absorbent containing an alkanolamine CO ₂ absorbent and a non-nucleophilic base. Has been. In the examples of Patent Document 1, alkanolamine and those using tetramethylguanidine as a non-nucleophilic base are described. Patent Document 2 describes a method for reducing an impurity gas, which includes a step of bringing a fluid containing an impurity gas such as CO ₂ into contact with an impurity removal mixture containing an ionic liquid and an amine compound. Is described.

Special table 2013-542060 gazette Special table 2011-521778 gazette

  The problems with conventional carbon dioxide separation and recovery methods using aqueous amine solutions are that high temperatures are required for the carbon dioxide desorption (reaction heat) process, and the solvent water has a large specific heat, and excessive energy for heating and cooling. This is because the latent heat of vaporization of water is excessive during heating. In the method described in Patent Document 1, an aqueous solvent is used or the boiling point of tetramethylguanidine to be used is as low as about 160 ° C., so there is a risk that the solvent loss will increase in the carbon dioxide desorption process. The method described in Patent Document 2 uses water or the like as a solvent, and in the Examples, only the result of a low temperature of carbon dioxide release of 100 ° C. is shown, and the temperature of the amine solution is increased.・ Excessive energy may be required for cooling.

  Therefore, the problems of the present invention are that the amount of absorption near room temperature is higher than that of the conventional aqueous amine solution, and easy desorption at a high temperature is excellent, the evaporation loss of the absorbing solution is small, the specific heat is low, and the reaction heat is small. An object of the present invention is to provide a carbon dioxide absorbing solution capable of reducing energy required for regeneration of the carbon dioxide absorbing solution per recovered carbon dioxide.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that when a specific tertiary polydentate amine is used as a solvent in a non-aqueous system, it has a high hydrogen bond acceptability near the room temperature, and has a three-dimensional structure. It also stabilizes and promotes the reaction between carbon dioxide and amine. At high temperatures, the release of carbon dioxide becomes easy. When a specific secondary amine is used as a carbon dioxide absorbent, the heat of reaction with carbon dioxide is reduced. In addition, the use of polydentate amines having a plurality of specific oxygen atoms and nitrogen atoms increases the amount of carbon dioxide absorbed, and such an absorbent is near room temperature compared to conventional amine aqueous solutions. The absorption amount of carbon dioxide is large and the absorption liquid can be handled at high temperature, the carbon dioxide is easy to desorb at the high temperature, the evaporation liquid has little evaporation loss, and the regeneration energy of the carbon dioxide absorption liquid It has been found that can be reduced. The present inventors have further studied and completed the present invention.

In order to solve the above problems, the present invention includes the following aspects.
(1) comprising a carbon dioxide chemically absorbing amine having a nitrogen-hydrogen bond and a tertiary amine solvent having no nitrogen-hydrogen bond,
The tertiary amine solvent having no nitrogen-hydrogen bond is rich in hydrogen bond acceptability, is also sterically stabilized, and promotes the reaction between the amine having the nitrogen-hydrogen bond and carbon dioxide. A tertiary polydentate amine having a main chain containing an oxygen atom and / or a nitrogen atom via a hydrocarbon group having 2 or more carbon atoms, and a total of 2 or more oxygen atoms and nitrogen atoms, and capable of high-temperature recovery Water-based carbon dioxide absorption solution.

(2) The tertiary polydentate amine is
A tertiary amine in which one hydrocarbon group having 2 or more carbon atoms in the main chain having a hydroxyl group and two unsubstituted hydrocarbon groups having 2 or more carbon atoms are bonded to one nitrogen atom;
A tertiary amine in which one hydrocarbon group having 3 or more carbon atoms in the main chain having a hydroxyl group and two unsubstituted hydrocarbon groups are bonded to one nitrogen atom;
A tertiary amine in which two hydrocarbon groups having 2 or more carbon atoms in the main chain having a hydroxyl group and one unsubstituted hydrocarbon group having 3 or more carbon atoms are bonded to one nitrogen atom, or an acyclic skeleton A tertiary amine having a diamine skeleton via an ethylene group, a propylene group, or a butylene group;
The carbon dioxide absorbing solution according to (1), wherein

(3) The tertiary polydentate amine is N-butyldiethanolamine, N, N, N ′, N′-tetrakis (2-hydroxyethyl) ethylenediamine, or N, N, N ′, N′-tetrakis (2- The carbon dioxide-absorbing solution according to (1) or (2), which is hydroxypropyl) ethylenediamine.

(4) The carbon dioxide absorbing solution according to (3), wherein the tertiary polydentate amine is N, N, N ′, N′-tetrakis (2-hydroxyethyl) ethylenediamine.

(5) The carbon dioxide absorbing liquid according to (1), wherein the tertiary polydentate amine is N-methyldiethanolamine, N-ethyldiethanolamine, or triethanolamine.

(6) The carbon dioxide absorbing liquid according to any one of (1) to (5), wherein the carbon dioxide chemically absorbing amine having a nitrogen-hydrogen bond further has a hydrocarbon group having a hydroxyl group.

(7) The carbon dioxide chemically absorbing amine having the nitrogen-hydrogen bond is 4-amino-1-butanol, N-methylethanolamine, 3-methylamino-1-propanol, 2- (ethylamino) ethanol, The carbon dioxide absorbing solution according to (6), which is 2- (butylamino) ethanol, monoethanolamine, or diethanolamine.

(8) The carbon dioxide absorbing liquid according to (7), wherein the carbon dioxide chemically absorbing amine having a nitrogen-hydrogen bond is diethanolamine.

(9) The carbon dioxide chemical-absorbing amine having a nitrogen-hydrogen bond has the oxygen atom and / or the nitrogen atom via a hydrocarbon group having 2 or more carbon atoms in the main chain. The carbon dioxide absorbing solution according to any one of 5).

(10) The carbon dioxide chemisorbable amine having a nitrogen-hydrogen bond has the diamine skeleton having a nitrogen atom via a hydrocarbon group having 2 or more carbon atoms in the main chain. ) And the carbon dioxide absorbing liquid according to any one of (9).

(11) The carbon dioxide chemically absorbing amine having a nitrogen-hydrogen bond is a polyamine having two or more diamine skeletons having a nitrogen atom via a hydrocarbon group having 2 or more carbon atoms in the main chain. The carbon dioxide absorption liquid as described in 10).

(12) The carbon dioxide chemically absorbing amine having a nitrogen-hydrogen bond is ethylenediamine, piperazine, N-hexylethylenediamine, N- (2-hydroxyethyl) ethylenediamine, N- (2-hydroxyisopropyl) ethylenediamine, N, N′-bis (2-hydroxyethyl) ethylenediamine, diethylenetriamine, tris (2-aminoethyl) amine, 1- (2-aminoethyl) piperazine, triethylenetetramine, or 1,2-bis (3-aminopropylamino) ) The carbon dioxide absorbing solution according to any one of (9) to (11), which is ethane.

(13) The carbon dioxide absorbent according to any one of (1) to (12), wherein the water content is less than 5% by mass.

(14) Carbon dioxide is absorbed into the carbon dioxide absorbing liquid by bringing the carbon dioxide absorbing liquid according to any one of (1) to (13) into contact with a mixed gas containing carbon dioxide at 50 ° C. or less. An absorption step of selectively separating carbon dioxide from the mixed gas; and heating the carbon dioxide absorption liquid that has absorbed the carbon dioxide to 120 ° C. or more to dissipate 90% or more of the absorbed carbon dioxide. A carbon dioxide separation and recovery method, comprising: a heating regeneration step of recovering the carbon dioxide absorbing liquid.

  The carbon dioxide absorbing liquid of the present invention has a large amount of absorption near room temperature compared to conventional amine aqueous solutions, and is excellent in easy desorption at high temperatures, has little evaporation loss of the absorbing liquid, has a low specific heat, and has a heat of reaction. It is small and can reduce the energy required to regenerate the carbon dioxide absorbing liquid per carbon dioxide to be recovered.

The figure which shows a carbon dioxide absorption test apparatus (atmospheric pressure gas blowing type). The figure which shows a carbon dioxide absorption test apparatus (high pressure and gas absorption amount measurement). The figure which shows a carbon dioxide reaction heat measuring apparatus. The figure which shows a carbon dioxide absorption-and-release test apparatus (temperature swing type). The graph which shows the carbon dioxide absorption amount of the carbon dioxide absorption liquid (MEA / various solvents) of Examples 1-1 to 1-6. The graph which shows the carbon dioxide absorption amount of the carbon dioxide absorption liquid (MEA / various solvent) of Examples 1-7 to 1-13. The graph which shows the carbon dioxide absorption amount of the carbon dioxide absorption liquid (various amine / MDEA solvent) of Examples 2-1 to 2-5. The graph which shows the carbon dioxide absorption amount of the carbon dioxide absorption liquid (various amine / MDEA solvent) of Examples 2-6 to 2-12. The graph which shows the carbon dioxide absorption amount of the carbon dioxide absorption liquid (various amine / MDEA solvent) of Examples 2-13 to 2-17. Reaction heat of each carbon dioxide absorption liquid. The graph which shows the carbon dioxide absorption amount of Examples 3-1 to 3-3 and the carbon dioxide absorption liquid of Examples 4-1 to 4-3. The graph which shows the carbon dioxide absorption amount of Examples 5-1 to 5-3 and the carbon dioxide absorption liquid of Examples 6-1 to 6-3. The graph which shows the carbon dioxide absorption amount of Examples 5-1 to 5-3 and the carbon dioxide absorption liquid of Examples 6-1 to 6-3. The graph which shows the result of the carbon dioxide absorption (50 degreeC) in an impurity test (water vapor | steam component accompanying). The graph which shows the result of the carbon dioxide emission (120 degreeC) in an impurity test (water vapor | steam component accompanying).

  The carbon dioxide absorbing liquid of the present invention is a non-aqueous carbon dioxide absorbing liquid that can be recovered at a high temperature, a carbon dioxide chemically absorbing amine having a nitrogen-hydrogen bond, and a tertiary amine solvent having no nitrogen-hydrogen bond. including. This tertiary amine solvent not having a nitrogen-hydrogen bond is rich in hydrogen bond acceptability, stabilized in three-dimensional structure, and promotes the reaction between an amine having a nitrogen-hydrogen bond and carbon dioxide. It is a tertiary polydentate amine having an oxygen atom and / or a nitrogen atom via a hydrocarbon group having 2 or more carbon atoms in the chain, and a total of 2 or more oxygen atoms and nitrogen atoms.

  “Non-aqueous” means that the carbon dioxide absorbing liquid of the present invention does not substantially contain water, preferably the water content is less than 10% by mass, more preferably less than 5% by mass, and particularly preferably. It is less than 3% by mass.

  “Recoverable at high temperature” means that the carbon dioxide-absorbing solution of the present invention that has absorbed carbon dioxide at around room temperature, preferably 10 ° C., has a high temperature, specifically 80 ° C. or higher, preferably 100 ° C. or higher. Can be heated to 120 ° C. or higher, more preferably 140 ° C. or higher, particularly preferably 150 ° C. or higher to release carbon dioxide as a gas from the carbon dioxide absorbing liquid, and preferably 50 carbon dioxide absorbed at 10 ° C. Mol% or more, more preferably 70 mol% or more, particularly preferably 90 mol% or more can be separated, and it is necessary that the absorption liquid is stable at these temperatures. It is preferable that the temperature is higher. “Recoverable at high temperature” is not intended to limit the carbon dioxide release temperature in the carbon dioxide absorbent of the present invention. The carbon dioxide absorbing liquid of the present invention can release carbon dioxide at a temperature higher than the temperature at which carbon dioxide is absorbed.

(Tertiary amine solvent)
The tertiary amine solvent used in the present invention does not have a nitrogen-hydrogen bond, is rich in hydrogen bond acceptability, is also stabilized in three-dimensional structure, and promotes the reaction between a carbon dioxide chemically absorbing amine and carbon dioxide. And a tertiary polydentate amine having an oxygen atom and / or a nitrogen atom via a hydrocarbon group having 2 or more carbon atoms in the main chain, and a total of 2 or more oxygen atoms and nitrogen atoms. Here, “rich in hydrogen bond acceptability, stabilized in three-dimensional structure, and promotes the reaction between carbon dioxide chemisorbable amine and carbon dioxide” means, for example, as shown in Formula 1, a tertiary multidentate The nitrogen and oxygen atoms of the amine interact in a multidentate manner with the hydrogen of the carbon dioxide chemically absorbing amine to stabilize the reaction product with carbon dioxide.

In Formula 1, a compound represented by H—N (R ¹ ) R ² represents a carbon dioxide chemically absorbing amine having a nitrogen-hydrogen bond according to the present invention, and R ¹ is unsubstituted or has a substituent. An optionally substituted hydrocarbon group or hydrogen, R ² is an unsubstituted or optionally substituted hydrocarbon group.

In Formula 1, a compound represented by X ¹ R ⁵ N (R ³ ) R ⁴ represents a tertiary polydentate amine according to the present invention, and R ³ and R ⁴ are unsubstituted or have a substituent. And optionally substituted hydrocarbon group, R ⁵ is a hydrocarbon group having 2 or more carbon atoms in the main chain, which may be unsubstituted or substituted, and X ¹ is a nitrogen atom or an oxygen atom and those Or a hydrocarbon group which may be unsubstituted or substituted. In this specification, the hydrocarbon group having 2 or more carbon atoms in the main chain means that the shortest basic skeleton between the nitrogen atom of the tertiary amine and the nitrogen atom or oxygen atom is an ethylene group or a propylene group. , And having 2 or more carbon atoms such as a butylene group. Therefore, for example, an amine whose main chain hydrocarbon is 1, such as HO—C (H) (CH ₃ ) N (R ³ ) R ⁴ , is not included in the tertiary polydentate amine according to the present invention. The hydrocarbon group having 2 or more carbon atoms in the main chain is preferably an ethylene group, propylene group or butylene group constituting an acyclic skeleton having a high degree of freedom, and more preferably an ethylene group.

Electron-donating oxygen and nitrogen atoms have a high hydrogen bond accepting property, and can interact with hydrogen of the carbon dioxide chemically absorbing amine to stabilize the reaction product with carbon dioxide. And since the hydrocarbon group having 2 or more carbon atoms in the main chain represented by R ⁵ and the curve in Formula 1 has a high degree of freedom, a nitrogen atom and / or a nitrogen atom bonded to both ends thereof is carbon dioxide. It can include the hydrogen of a chemically absorbing amine. Such tertiary polydentate amines promote the reaction with carbon dioxide by including and stabilizing hydrogen of the carbon dioxide chemically absorbing amine on the relatively low temperature side, such as near room temperature, which absorbs carbon dioxide. . Further, hydrogen bonded to X ¹ may form carbon dioxide and hydrogen bonds reacted with carbon dioxide chemical absorption amine, the reaction product was further stabilized, it is possible to accelerate the reaction with carbon dioxide. On the other hand, on the high temperature side where carbon dioxide is released, the degree of inclusion decreases, so that the release of carbon dioxide can be promoted.

  In this specification, when there are a plurality of nitrogen atoms in one molecule and these nitrogen atoms are different series, the series of amine is the higher series. For example, a tertiary nitrogen atom (three hydrocarbon groups are bonded to the nitrogen atom) and a secondary nitrogen atom (two hydrocarbon groups are bonded to the nitrogen atom and one hydrogen atom is bonded to one molecule) The amine is a tertiary amine. Therefore, in this example, it is a tertiary amine having a hydrogen-nitrogen bond and is classified as a carbon dioxide chemically absorbing amine, not a tertiary amine solvent. A nitrogen-carbon double bond defines a series as two hydrocarbon groups bonded to a nitrogen atom.

The tertiary polydentate amine used as the tertiary amine solvent in the present invention is rich in hydrogen bond acceptability, stabilized in three-dimensional structure, and promotes the reaction between the carbon dioxide chemically absorbing amine and carbon dioxide. Although it is not particularly limited as long as it has a tertiary amine having an oxygen atom and / or a nitrogen atom via a hydrocarbon group having 2 or more carbon atoms in the main chain, and the total of the oxygen atom and the nitrogen atom is 2 or more, A tertiary polydentate amine represented by formula 2 in which one hydrocarbon group having one hydroxyl group and two hydrocarbon groups having no hydroxyl group are bonded to one nitrogen atom;
(In Formula 2, R ³ and R ⁴ are unsubstituted or a hydrocarbon group which may have a substituent (excluding a hydroxyl group), n1 is an integer of 2 or more, and a carbon atom in parentheses is substituted. (It may have a group, and a part of carbon atoms may be substituted with a hetero atom.)
A tertiary polydentate amine represented by formula 3 in which two hydrocarbon groups having a hydroxyl group and one hydrocarbon group having no hydroxyl group are bonded to one nitrogen atom;
(In Formula 3, R ³ is a hydrocarbon group which may be unsubstituted or have a substituent (excluding a hydroxyl group), n1 and n2 are integers of 2 or more, and the carbon atom in parentheses is a substituent. And a part of the carbon atom may be substituted with a hetero atom.)
A tertiary polydentate amine represented by formula 4 in which three hydrocarbon groups having a hydroxyl group are bonded to one nitrogen atom;
(In Formula 4, n1, n2, and n3 are integers of 2 or more, and the carbon atom in parentheses may have a substituent, or a part of the carbon atom may be substituted with a heteroatom. Good.)

A tertiary amine having a diamine skeleton having two nitrogen atoms via a hydrocarbon group having 2 or more carbon atoms, represented by Formula 5, can be given.
(In formula 5, R ³ , R ⁴ , R ⁵ , and R ⁶ are unsubstituted or optionally substituted hydrocarbon groups, n4 is an integer of 2 or more, and a carbon atom in parentheses May have a substituent, and a part of carbon atoms may be substituted with a hetero atom.)

  In this specification, unless otherwise specified, the hydrocarbon group includes, for example, an unsubstituted alkyl group having a substituent such as a halogen group or a hydroxyl group, an alkenyl group, and an alkynyl group. May be non-cyclic and may have a hetero atom in the skeleton. Among these, the hydrocarbon group having a hydroxyl group is preferably an alkyl group having a hydroxyl group. The hydrocarbon group having no hydroxyl group is preferably an alkyl group.

As the tertiary polydentate amine represented by formula 2 in which one hydrocarbon group having one hydroxyl group and two hydrocarbon groups having no hydroxyl group are bonded to one nitrogen atom, for example, 2-dimethylaminoethanol ((Me) ₂ N (EtOH)), 2- (diethylamino) ethanol ((Et) ₂ N (EtOH)), 2- (diisopropylamino) ethanol ((i-Pr) ₂ N (EtOH)), 2- (Dibutylamino) ethanol ((n-Bu) ₂ N (EtOH)), 3-dimethylamino-1-propanol ((Me) ₂ N (n-PrOH)), and 4- (dimethylamino) -1-butanol ((Me) ₂ N (n-BuOH)) and the like.

Among them, in Formula 2, R ³ and R ⁴ are tertiary amines which are hydrocarbon groups having 2 or more carbon atoms, that is, hydrocarbons having 2 or more carbon atoms in the main chain having a hydroxyl group in one nitrogen atom. A tertiary amine in which one group and two hydrocarbon groups having 2 or more carbon atoms are bonded, or a tertiary amine in which n1 is an integer of 3 or more in Formula 2, that is, one nitrogen atom has a hydroxyl group A tertiary amine in which one hydrocarbon group having 3 or more carbon atoms in the main chain and two unsubstituted hydrocarbon groups are bonded is preferable. Specifically, 2- (diethylamino) ethanol, 2- (diisopropylamino) ethanol, 2- (dibutylamino) ethanol, 3-dimethylamino-1-propanol, 4- (dimethylamino) -1-butanol, etc. Is mentioned.

As a tertiary polydentate amine represented by formula 3 in which two hydrocarbon groups having a hydroxyl group and one hydrocarbon group having no hydroxyl group are bonded to one nitrogen atom, for example, N-methyldiethanolamine ( MDEA), N-ethyldiethanolamine ((Et) N (EtOH) ₂ ), N-butyldiethanolamine ((n-Bu) N (EtOH) ₂ ).

Among them, in Formula 3, a tertiary amine in which R ³ is a hydrocarbon group having 3 or more carbon atoms, that is, two hydrocarbon groups having 2 or more carbon atoms in a main chain having a hydroxyl group in one nitrogen atom, A tertiary amine to which one unsubstituted hydrocarbon group having 3 or more carbon atoms is bonded is preferred, and specific examples include N-butyldiethanolamine.

As the tertiary polydentate amine represented by the formula 4 in which three hydrocarbon groups having a hydroxyl group are bonded to one nitrogen atom, for example, triethanolamine (N (EtOH) ₃ ), tripropanolamine (N ( n-PrOH) ₃ ) and tributanolamine (N (n-BuOH) ₃ ). Of these, triethanolamine is preferable.

As the tertiary amine having a diamine skeleton having two nitrogen atoms via a hydrocarbon group having 2 or more carbon atoms represented by Formula 5, for example, N, N, N ′, N′-tetramethylethylenediamine (( Me) ₂ N (C ₂ H ₄ ) N (Me) ₂ ), and further, a nitrogen atom is bonded to a substituent having an oxygen atom via a hydrocarbon group having 2 or more carbon atoms in the main chain, N, N, N ′, N′-tetrakis (2-hydroxyethyl) ethylenediamine ((EtOH) ₂ N (C ₂ H 4) N (EtOH) ₂ ), N, N, N ′, N′-tetrakis (2- hydroxypropyl) ethylenediamine _{((i-PrOH) 2 N} (C 2 H 4) N (i-PrOH) 2) ethylene group constituting a non-cyclic backbone, such as, having diamine skeleton via a propylene group, or butylene group Tertiary amine It is below. Among these, N, N, N ′, N′-tetrakis (2-hydroxyethyl) ethylenediamine is preferable.

(Carbon dioxide chemically absorbing amine)
The carbon dioxide chemically absorbing amine used in the present invention has a nitrogen-hydrogen bond. An amine having a nitrogen-hydrogen bond can react with carbon dioxide to form a carbamate salt (Formula 6-1). In addition, proton transfer occurs between the produced carbamate salt and the unreacted amine (Formula 6-2), and the reaction between the carbon dioxide chemically absorbing amine and carbon dioxide is stoichiometrically 2: 1. (Formula 6-3).

(Here, R ¹ and R ² are each a hydrogen atom or a hydrocarbon group.)

  In this way, the carbon dioxide chemically absorbing amine can absorb carbon dioxide at a relatively low temperature of about 20 ° C. Carbon dioxide chemically absorbing amine that has absorbed carbon dioxide releases carbon dioxide at a temperature higher than at least the temperature at which carbon dioxide is absorbed, preferably 100 ° C or 150 ° C, and carbon dioxide chemically absorbing amine is regenerated. Is done.

The carbon dioxide chemically absorbing amine used in the present invention is not particularly limited as long as it is an amine having a nitrogen-hydrogen bond, and one or two hydrogen atoms of ammonia represented by formula 7 are substituted with a hydrocarbon group. Or an amine having a primary or secondary nitrogen atom.
(In Formula 7, R ¹ is a hydrocarbon group or hydrogen which may be unsubstituted or substituted, and R ² is a hydrocarbon group which may be unsubstituted or substituted. Some of the carbon atoms in the hydrogen group may be substituted with heteroatoms.)

More specifically, as shown in Formula 8, an amine having an oxygen atom and / or a nitrogen atom via a hydrocarbon group having 2 or more carbon atoms in the main chain can be mentioned.
(In Formula 8, R ¹ is an unsubstituted or optionally substituted hydrocarbon group or hydrogen, and n5 is an integer of 2 or more. The carbon atom in parentheses has a substituent. X may be a nitrogen atom or an oxygen atom such as —OR ⁵ , —N (R ⁶ ) R ⁷ , and a hydrogen atom bonded to them. It is a hydrocarbon group which may be substituted or substituted (R ⁵ , R ⁶ and R ⁷ are a hydrocarbon group which may be unsubstituted or substituted or hydrogen). is there.

More specifically, an amine in which two hydrogen atoms and one hydrocarbon group having a hydroxyl group are bonded to one nitrogen atom represented by formula 9;
(In Formula 9, n6 is an integer of 2 or more. The carbon atom in parentheses may have a substituent, and a part of the carbon atom may be substituted with a hetero atom.)

An amine in which one hydrogen atom, one hydrocarbon group having a hydroxyl group and one hydrocarbon group having no hydroxyl group are bonded to one nitrogen atom represented by Formula 10;
(In formula 10, R ⁷ is a hydrocarbon group which may be unsubstituted or have a substituent (excluding a hydroxyl group), n7 is an integer of 2 or more. The carbon atom in parentheses has a substituent. And some of the carbon atoms may be substituted with heteroatoms.)

An amine represented by formula 11 wherein one hydrogen atom and two hydrocarbon groups having a hydroxyl group are bonded to one nitrogen atom;
(In Formula 11, n8 and n9 are integers of 2 or more. The carbon atom in parentheses may have a substituent, and a part of the carbon atom may be substituted with a hetero atom.)

One nitrogen atom represented by Formula 12 includes an amine having a diamine skeleton having a hydrogen atom and a nitrogen atom via a hydrocarbon group having 2 or more carbon atoms in the main chain.
(In Formula 12, R ⁸ , R ⁹ and R ¹⁰ are unsubstituted or optionally substituted hydrocarbon groups, and n10 is an integer of 2 or more. The carbon atoms in parentheses are substituents. And a part of the carbon atom may be substituted with a hetero atom.)

Examples of amines represented by formula 9 in which one hydrogen atom and one hydrocarbon group having a hydroxyl group are bonded to one nitrogen atom include monoethanolamine (MEA), 3-amino-1-propanol (NH _{2 (} N-PrOH)), 4-amino-1-butanol (NH ₂ (n-BuOH)) and the like. Among them, an amine in which two hydrogen atoms such as 4-amino-1-butanol and one hydrocarbon group having 3 or more carbon atoms having a hydroxyl group is bonded is preferable.

  An amine in which one hydrogen atom, one hydrocarbon group having a hydroxyl group and one hydrocarbon group having no hydroxyl group are bonded to one nitrogen atom represented by Formula 10 is N-methylethanolamine ( MMEA), 3-methylamino-1-propanol (MeNH (n-PrOH)), 2- (ethylamino) ethanol (EtNH (EtOH)), 2- (propylamino) ethanol (PrNH (EtOH)), 2- (Butylamino) ethanol (BuNH (EtOH)) and the like.

  Examples of the amine represented by formula 11 in which one hydrogen atom and two hydrocarbon groups having a hydroxyl group are bonded to each other include diethanolamine (DEA), dipropanolamine, and dibutanolamine.

Examples of the amine having a diamine skeleton having a hydrogen atom and a nitrogen atom via a hydrocarbon group having 2 or more carbon atoms in the main chain represented by Formula 12 include alkylenes such as ethylenediamine (EDA) and piperazine (PZ). diamine; N- alkyl alkylenediamine hexyl ethylenediamine (HexEDA); N- (2- hydroxyethyl) ethylenediamine _{(H 2 N (C 2 H} 4) NHEtOH), N- (2- hydroxyisopropyl) ethylenediamine _(H 2 N (C ₂ H ₄ ) NH _iso- PrOH), N, N′-bis (2-hydroxyethyl) ethylenediamine (EtOHNH (C ₂ H ₄ ) NHEtOH) and other alkylene diamines having a hydroxyalkyl group; diethylenetriamine (H ₂ N _{(C 2 H 4) HN (} C 2 H 4) NH 2), Tris (2-aminoethyl) amine (N (C ₂ H ₄ NH ₂ ) ₃ ), 1- (2-aminoethyl) piperazine ((PZ- (C ₂ H ₄ ) NH ₂ )), triethylenetetramine (H _{2 N (C 2 H 4)} HN (C 2 H 4) HN (C 2 H 4) NH 2), 1,2- bis (3-aminopropionic pull amino) ethane _{(H 2 N (C 3 H} 6) Examples thereof include polyamines having two or more diamine skeletons having a nitrogen atom via a hydrocarbon group having 2 or more carbon atoms in the main chain, such as HN (C ₂ H ₄ ) HN (C ₃ H ₆ ) NH ₂ ). In the present specification, “having two or more diamine skeletons” includes a case where nitrogen atoms of the diamine skeleton are common, such as diethylenetriamine.

  The carbon dioxide chemically absorbing amine used in the present invention preferably has a nitrogen-hydrogen bond and a hydrocarbon group having a hydroxyl group. The hydrocarbon group having a hydroxyl group is not particularly limited, and examples thereof include a hydroxyalkyl group, a hydroxyalkenyl group, and a hydroxyalkynyl group, and can further have a substituent such as a halogen group. As the hydrocarbon group having a hydroxyl group, a hydroxyalkyl group is preferred. Amines having a hydroxyalkyl group are also called alkanolamines. Examples of the hydroxyalkyl group include a hydroxymethyl group, a hydroxyethyl group, a hydroxypropyl group, a hydroxy-i-propyl group, and a hydroxybutyl group. Especially, it is preferable in it being C2 or 3 or more, and a hydroxyethyl group is especially preferable.

  Specific examples of the carbon dioxide chemically absorbing amine having a nitrogen-hydrogen bond and a hydrocarbon group having a hydroxyl group include MEA, MMEA, 2- (ethylamino) ethanol, 2- (propylamino) ethanol, 2- (Butylamino) ethanol, 3-methylamino-1-propanol, N- (2-hydroxyethyl) ethylenediamine, N- (2-hydroxyisopropyl) ethylenediamine, N, N′-bis (2-hydroxyethyl) ethylenediamine, DEA And dipropanolamine. Among them, a secondary amine or a primary amine in which a hydrocarbon group having 2 or more carbon atoms having a hydroxyl group is bonded to a nitrogen atom is preferable because it has a high efficiency of carbon dioxide separation and recovery as a carbon dioxide absorbing solution, and has a hydroxyl group. A secondary amine in which a hydrocarbon group having 2 or more carbon atoms is bonded to a nitrogen atom is more preferable. More specifically, MEA, DEA, and MMEA are preferable, and DEA is more preferable.

(Carbon dioxide absorbent)
The carbon dioxide absorbing liquid of the present invention contains the above-described carbon dioxide chemically absorbing amine having a nitrogen-hydrogen bond and the above-mentioned tertiary amine solvent not having a nitrogen-hydrogen bond. The carbon dioxide chemically absorbing amine and tertiary amine solvent used in the present invention are usually liquid at room temperature, and the carbon dioxide absorbing liquid of the present invention is a mixture of a carbon dioxide chemically absorbing amine and a tertiary amine solvent. Obtained by.

  The combination of the carbon dioxide chemically absorbing amine and the tertiary amine solvent is not particularly limited, but when the carbon dioxide chemically absorbing amine is monoethanolamine, the tertiary amine solvent has a main chain having a hydroxyl group on one nitrogen atom. A tertiary amine in which one hydrocarbon group having 2 or more carbon atoms and two unsubstituted hydrocarbon groups having 2 or more carbon atoms are bonded; the main chain having a hydroxyl group on one nitrogen atom has 3 or more carbon atoms A tertiary amine in which one hydrocarbon group is bonded to two unsubstituted hydrocarbon groups; two hydrocarbon groups having 2 or more carbon atoms in the main chain having a hydroxyl group on one nitrogen atom, and unsubstituted A tertiary amine in which one hydrocarbon group having 3 or more carbon atoms is bonded; or a tertiary amine having a diamine skeleton via an ethylene group, propylene group, or butylene group constituting an acyclic skeleton; Zodiac amine is preferred There.

  Specifically, MEA, 2-dimethylaminoethanol, 2- (diethylamino) ethanol, 2- (diisopropylamino) ethanol, 2- (dibutylamino) ethanol, 3-dimethylamino-1-propanol, 4- (dimethyl Amino) -1-butanol, N-methyldiethanolamine, N-ethyldiethanolamine, N-butyldiethanolamine, triethanolamine, N, N, N ′, N′-tetramethylethylenediamine, N, N, N ′, N′— A combination of tetrakis (2-hydroxyethyl) ethylenediamine or N, N, N ′, N′-tetrakis (2-hydroxypropyl) ethylenediamine is preferred.

  When the tertiary amine solvent is MDEA, the carbon dioxide chemisorbable amine has a nitrogen-hydrogen bond and the main chain has 2 or more oxygen atoms and / or nitrogen via a hydrocarbon group. An amine having an atom is preferable. Specifically, MDEA, MEA, 3-amino-1-propanol, 4-amino-1-butanol, MMEA, 3-methylamino-1-propanol, 2- (ethylamino) ethanol, 2- (propylamino) ) Ethanol, 2- (butylamino) ethanol, DEA, dipropanolamine, dibutanolamine, EDA, PZ, N-hexylethylenediamine, N- (2-hydroxyethyl) ethylenediamine, N- (2-hydroxyisopropyl) ethylenediamine, N, N′-bis (2-hydroxyethyl) ethylenediamine, diethylenetriamine, tris (2-aminoethyl) amine, 1- (2-aminoethyl) piperazine, triethylenetetramine, or 1,2-bis (3-aminopro A combination of (pullamino) ethane is preferred.

  The ratio of the carbon dioxide chemically absorbing amine and the tertiary amine solvent in the carbon dioxide absorbing liquid is not particularly limited, and is appropriately selected depending on these types. Carbon dioxide chemically absorbing amine / (carbon dioxide chemically absorbing amine + 3 Secondary amine solvent) (mass ratio), preferably 1/100 to 50/100, more preferably 10/100 to 40/100. When the ratio of the carbon dioxide chemically absorbing amine is within this range, the amount of carbon dioxide absorbed near room temperature can be increased, and the carbon dioxide easy desorption at a high temperature can be improved.

  The carbon dioxide absorbing liquid of the present invention is a non-aqueous carbon dioxide absorbing liquid and does not substantially contain water. Specifically, the water content of the carbon dioxide absorbing liquid of the present invention is preferably less than 10% by mass, more preferably less than 5% by mass, and particularly preferably less than 3% by mass.

(CO2 separation and recovery method)
The carbon dioxide absorbing liquid of the present invention can separate and recover carbon dioxide gas from a mixed gas containing carbon dioxide. The mixed gas is not particularly limited as long as it is a gaseous mixture containing carbon dioxide, and may contain other components. Examples of other components include acid gases other than carbon dioxide, nitrogen gas, oxygen gas, water, and dust. Examples of acidic gases other than carbon dioxide include hydrogen sulfide; sulfur monoxide, sulfur dioxide (sulfurous acid gas), sulfur oxides such as sulfur trioxide; nitrogen monoxide, nitrogen dioxide, nitrous oxide (dinitrogen monoxide). And nitrogen oxides such as dinitrogen trioxide, dinitrogen tetroxide, and dinitrogen pentoxide; inorganic acids such as hydrochloric acid, nitric acid, phosphoric acid, and sulfuric acid; and organic acids such as carboxylic acid, sulfonic acid, and carbonic acid. The carbon dioxide absorbing liquid of the present invention has little influence on the recoverability of carbon dioxide even if the mixed gas contains a saturated amount of water as another component. Further, the carbon dioxide absorbing liquid of the present invention has little influence on the recoverability of carbon dioxide even if the mixed gas contains dust as another component.

Next, a carbon dioxide separation and recovery method using the carbon dioxide absorbing liquid of the present invention will be described.
In the carbon dioxide separation and recovery method of the present invention, the carbon dioxide absorbing liquid is brought into contact with a mixed gas containing carbon dioxide, so that carbon dioxide is absorbed by the carbon dioxide absorbing liquid and carbon dioxide is selected from the mixed gas. An absorption step for separating the carbon dioxide, and heating and regeneration for recovering the carbon dioxide absorption liquid by dissipating and recovering the absorbed carbon dioxide by heating the carbon dioxide absorption liquid absorbing the carbon dioxide to a temperature higher than that of the absorption process. Process. The carbon dioxide absorbing liquid of the present invention has a large amount of absorption near room temperature, excellent detachability at high temperatures, low evaporation loss, low specific heat, and low reaction heat. Energy required for regeneration of the carbon dioxide absorbing liquid can be reduced.

  The temperature of the carbon dioxide absorbing liquid in the absorption step is not particularly limited as long as the carbon dioxide absorbing liquid does not solidify, but is preferably 60 ° C. or lower, preferably 40 ° C. or lower, and more preferably near room temperature (20 ° C. ± 20 ° C.). 10 degrees C or less is especially preferable. As the temperature of the carbon dioxide absorbing solution in the absorption process is lower, the amount of carbon dioxide absorbed tends to increase. Since the carbon dioxide separation and recovery method of the present invention chemically absorbs carbon dioxide in the carbon dioxide absorbing liquid, the pressure in the absorption step is not particularly limited, but solubility of carbon dioxide in the carbon dioxide absorbing liquid, In terms of preventing loss due to the accompanying carbon absorption liquid, the pressure is usually preferably equal to or higher than atmospheric pressure, and can be used even under high pressure conditions such as 1 MPa to 6 MPa.

  The temperature of the carbon dioxide absorbing liquid in the heating regeneration step is not particularly limited as long as it is higher than the temperature in the absorption step, but is preferably 40 ° C. or higher, more preferably 80 ° C. or higher, further preferably 100 ° C. or higher, particularly preferably 140 ° C. or higher. Can be high. The larger the temperature difference, the higher the percentage of carbon dioxide absorbed in the absorption process. The temperature of the carbon dioxide absorbing liquid in the more specific heating regeneration step is preferably 50 ° C. or higher, more preferably 80 ° C. or higher, still more preferably 120 ° C. or higher, and particularly preferably 150 ° C. or higher. Since the carbon dioxide absorbing liquid of the present invention is stable at high temperatures and has a low vapor pressure, it can be heated to a higher temperature than an aqueous amine solution. The upper limit of the temperature of the carbon dioxide absorbing liquid in the heating regeneration step is not particularly limited, but is preferably 200 ° C. or lower, more preferably 180 ° C. or lower, and further preferably 160 ° C. or lower. Since the carbon dioxide separation and recovery method of the present invention recovers carbon dioxide by chemically dissipating it from the carbon dioxide absorbing solution, the pressure in the heating regeneration step is not particularly limited, but the carbon dioxide is released from the carbon dioxide absorbing solution. It is preferable that the pressure in the absorption process is equal to or lower than the pressure in the absorption process, and the pressure in the absorption process can be higher.

  In the carbon dioxide separation and recovery method of the present invention, the ratio of recovering the carbon dioxide absorbed in the absorption step is not particularly limited, but it is preferable to recover 50% or more, preferably 80% or more, 90 % Or more is preferably recovered, more preferably 95% or more. Since the carbon dioxide absorption liquid of the present invention can increase the temperature difference between the carbon dioxide absorption liquid in the absorption process and the heating regeneration process, carbon dioxide can be recovered with a high yield.

  In the carbon dioxide separation and recovery method of the present invention, the method for contacting the mixed gas and the carbon dioxide absorbing liquid is not particularly limited as long as carbon dioxide is chemically absorbed by the carbon dioxide absorbing liquid. For example, a method of bubbling a mixed gas in a carbon dioxide absorbing solution, a method of spraying a carbon dioxide absorbing solution on the mixed gas, a method of bringing a mixed gas into contact with a material impregnated or gelled with a carbon dioxide absorbing solution, etc. .

  In the carbon dioxide separation and recovery method of the present invention, the method for regenerating the carbon dioxide absorbing liquid is not particularly limited as long as the absorbed carbon dioxide is diffused and the carbon dioxide absorbing liquid is regenerated.

  The carbon dioxide absorbing liquid and the carbon dioxide separation and recovery method using the same according to the present invention are excellent in the separation and recovery of carbon dioxide, but can also be used for the separation and recovery of acid gases other than carbon dioxide.

(Example)
EXAMPLES Hereinafter, although this invention is demonstrated based on an Example, this invention is not limited to these Examples. The following measurement methods were used for the measurement. The pressure is an absolute pressure unless otherwise specified.
(Measuring method)

(1) Carbon dioxide absorption (normal pressure blowing type)
Measurement was performed at normal pressure using a carbon dioxide absorption test apparatus shown in FIG. The carbon dioxide absorption test apparatus comprises a carbon dioxide cylinder 101 for introducing carbon dioxide into a glass reaction vessel 112, a pressure reducing valve 102, a flow meter 103, a valve 104, a coiled heat exchanger 105, and a valve 106. In addition, a constant temperature bath 108 in which the heating medium 107 is placed, a resistance indicator 110 connected to a platinum temperature measuring element 109 for measuring the temperature of the heating medium 107 in the constant temperature bath 108, and a constant temperature of the heating medium 107 in the constant temperature bath 108. A cooling water circulation device 111 that adjusts to the above, and a magnetic stirrer 114 that rotates the rotor 113 placed in the reaction vessel 112.
A plug 115, a gas introduction pipe 116, and a discharge pipe 117 with a valve can be attached to the reaction vessel 112. The valve 106 can be connected to a gas introduction pipe 116 attached to the reaction vessel 112. The heat exchanger 105 and the reaction vessel 112 are immersed in the heat medium 107 of the thermostatic bath 108 and maintained at a constant temperature by the cooling water circulation device 111. A rotor 113 is placed in the reaction vessel 112, and the carbon dioxide absorbing liquid in the reaction vessel 112 can be stirred by the magnetic stirrer 114. The heat medium 107 uses water when measuring at 10 to 80 ° C., and uses oil when measuring at 80 to 150 ° C.
Below, the carbon dioxide absorption amount measurement procedure using this carbon dioxide absorption test apparatus is described.
1) In a nitrogen atmosphere, a predetermined amount (about 10 cc) of carbon dioxide absorbing liquid is separated into a glass reaction vessel 112, and the mouth of the reaction vessel 112 is sealed with a stopper 115. The mass of the entire reaction vessel is measured with an analytical balance, and the mass of the tare (reaction vessel 112, rotor 113, and stopper 115) is subtracted _therefrom to obtain the mass W _total of the carbon dioxide absorbing liquid.
2) To the reaction vessel 112 fitted with a gas inlet tube 116 and discharge pipe 117, again, to obtain a mass _{W 2} of the entire reaction vessel by measuring the mass.
3) Place the reaction vessel 112 in the thermostat 108. The gas introduction pipe 116 is connected to the valve 106.
4) Keep the temperature of the thermostatic chamber 108 at 40 ° C., circulate carbon dioxide through the reaction vessel 112, and absorb the carbon dioxide in the carbon dioxide absorbing solution. The mass of the entire reaction vessel is measured with an analytical balance every certain time (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) The mass W _CO2 of carbon dioxide absorbed in the carbon dioxide absorbing liquid is determined based on the following formula.
W _CO2 = W ₃ -W ₂
Further, the carbon dioxide absorption amount α _CO2 per mole of the carbon dioxide chemically absorbing amine in the carbon dioxide absorbing liquid is determined based on the following formula.
α _CO2 = (W _CO2 / M _CO2 ) / (W ₁ / M _chem )
Here, in the above formula, M _CO2 is the molar mass of carbon dioxide, M _chem is the molar mass of the carbon dioxide chemically absorbing amine, and the mass W ₁ of the carbon dioxide chemically absorbing amine is the mass W of the carbon dioxide absorbing liquid. It was determined by multiplying the mass fraction _{x 1} in _total.
6) The temperature of the thermostatic chamber 108 is changed as appropriate, and the operations and analyzes of 4) to 5) are performed to determine the carbon dioxide absorption amount at each temperature. Then, the mass of the carbon dioxide absorbed at 40 degreeC is measured again, and reproducibility is confirmed.

(2) Carbon dioxide absorption (high pressure sealed cell)
In the atmospheric pressure blowing type measurement method of (1) above, particularly when the vapor pressure of the solvent is high, the solvent is released from the reaction vessel together with the carbon dioxide gas, and the amount of carbon dioxide absorbed cannot be measured accurately. Sometimes. Since the carbon dioxide absorption liquid composed of MEA / water of Comparative Example 1 has a high vapor pressure of water, the reaction vessel 112 is replaced with a high pressure cell (pressure cell) 215 which is a pressure vessel as shown in FIG. In place of the gas introduction pipe 116 and the discharge pipe 117, measurement is performed using a gas introduction pipe with a valve and a pressure stopper having a length such that the end of the pipe does not contact the liquid surface. The carbon dioxide absorption measurement procedure using this carbon dioxide absorption test apparatus (high-pressure sealed cell) is to open the valve 210 connected to the pressure cell before measuring the mass change and leave it at normal pressure for a suitable time. Except for this, the procedure is the same as that of the carbon dioxide absorption device (normal pressure blowing type) described above.

(3) Measurement of reaction heat of absorbing liquid The calorific value when the carbon dioxide absorbing liquid absorbs carbon dioxide was measured under the conditions of 25 ° C. and carbon dioxide pressure of about 0.1 MPa using the reaction heat measuring apparatus shown in FIG. And the heat of reaction per mole of carbon dioxide was measured.
3 includes a carbon dioxide cylinder 301, a nitrogen cylinder 302, a cooling water circulation device 303, syringe pumps 304 and 305, a constant temperature water tank 306, a thermometer 307, a calorimeter 308, a control personal computer 309, and a pressure gauge 310. And a temperature control jacket 311. The procedure for measuring the heat of reaction is described below.
1) In a glove box with a sufficiently low dew point, a predetermined amount (about 0.1 cc) of carbon dioxide absorption liquid sufficiently dried in advance is charged into a stainless steel container, and the amount charged (W _total ) is measured with an electronic balance. . Thereafter, the stainless steel container is set on a calorimeter 308 maintained at 25 ° C. In addition, the constant temperature water tank 306 is maintained at 40 ° C. The syringe pump 305 is used to flow nitrogen at 0.01 mL / min, and waits until the change in the amount of heat becomes 0.01 mW / h or less.
2) When the change in the amount of heat becomes 0.01 mW / h or less, the syringe pump 305 is stopped. Thereafter, the syringe pump 304 is immediately started, carbon dioxide is caused to flow into a stainless steel container set in the calorimeter 308, and carbon dioxide is absorbed by the carbon dioxide absorbent. When the exothermic peak accompanying the absorption of carbon dioxide is detected and a certain time elapses, the change in calorie again becomes 0.01 mW / h or less. Considering that the amount of carbon dioxide absorbed has reached saturation, the syringe pump 304 is stopped and the measurement is terminated.
3) Using the control personal computer 309, the peak is integrated to obtain the calorific value (Q). The heat of reaction (ΔH) is determined using the following equation:
ΔH = Q / (W _total × (x ₁ / M _chem ) × α _CO2 )
In the above formula, x ₁ is the mass fraction of the carbon dioxide chemically absorbing amine in the carbon dioxide absorbing liquid, M _chem is the molar mass of the carbon dioxide chemically absorbing amine, and α _CO2 is the amount of carbon dioxide absorbed per mole of amine ( Molar ratio).

(4) Impurity test (with water vapor component)
The effect of impurities in the mixed gas on carbon dioxide separation and recovery was investigated in the case where the impurities were water vapor. Absorption of carbon dioxide at 50 ° C. when the mixed gas (12 mol% CO ₂ —N ₂ ) is dry and contains a water vapor component using the carbon dioxide absorption / emission test apparatus (temperature swing type) shown in FIG. After the test, the temperature was raised to 120 ° C. and a carbon dioxide emission test was conducted. A carbon dioxide absorption / dissipation test apparatus (temperature swing type) includes a carbon dioxide cylinder 401, a nitrogen cylinder 402, mass flow controllers 403 and 404, a constant temperature humidifier 405, an absorption liquid injector 406, a reactor 407, a constant temperature bath 408, a controller 409, A stirrer 410, a stirring blade 411, a thermometer 412, a cooling water circulation device 413, a cooler 414, a pressure gauge 415, a carbon dioxide concentration meter 416, a data logger 417, a gas flow meter 418, a recording PC 409, and A to I valves. Is done.
The operation procedure of the carbon dioxide absorption / emission test is described below.
1) Set the reactor in an empty state, flow only nitrogen gas from the nitrogen cylinder 402 at a predetermined flow rate with the mass flow controller 404, replace the system with nitrogen gas, and the reading of the carbon dioxide concentration meter 416 is 0.00 Check to show%.
2) Turn on the cooling water circulation device 413 and cool the cooler 414 to around 0 ° C.
3) In a state where nitrogen gas is allowed to flow slowly, 100 mL of the carbon dioxide absorbing solution is put into the reactor 407 from the absorbing solution injector 406.
4) Operate valve E to switch the flow path of nitrogen gas to the bypass side.
5) Turn on the power of the stirrer 410 and rotate the stirring blade 411 at 800 rpm.
6) The value of the thermometer 412 set in the reactor 407 is read, and the temperature of the thermostat 408 is controlled by the controller 409 so that the carbon dioxide absorption liquid becomes 50.0 ° C.
7) The carbon dioxide cylinder 401 is opened, and a predetermined flow rate of carbon dioxide is caused to flow by the mass flow controller 403.
8) Using the mass flow controller 403 for carbon dioxide and the mass flow controller 404 for nitrogen, the carbon dioxide concentration is adjusted to 12.0% and the total flow rate of the mixed gas is adjusted to about 400 mL / min.
9) In the state of the bypass side, the values of the carbon dioxide concentration meter 416 and the gas flow meter 418 are measured at intervals of 2 seconds using the data logger 417 and the recording PC 418 and confirmed to be stable for 30 minutes or more.
10) Operate the valve E to switch the flow path to the reactor 407 side. The time when the valve E is switched is set to time 0 minutes, and the values of the carbon dioxide concentration meter 416 and the gas flow meter 418 are continuously recorded for 5 hours at intervals of 2 seconds.
11) After 5 hours, the temperature of the thermostatic chamber 408 is controlled by the controller 409 so that the temperature of the absorbing solution becomes 120 ° C.
12) Record the values of the carbon dioxide concentration meter 416 and the gas flow meter 418 continuously for 3 hours at intervals of 2 seconds, assuming that the time set at 120 ° C. is 0 minute.
13) After 3 hours, the gas flow path is switched from the reaction vessel side to the bypass side, recording of the values of the carbon dioxide concentration meter 416 and the gas flow meter 418 is stopped, and the experiment is terminated.
14) The carbon dioxide concentration and gas flow rate obtained at 50 ° C. were converted into standard states (0 ° C., 1 atm), respectively, and the amount of carbon dioxide at the outlet of the absorbing solution was determined. The carbon dioxide concentration and gas flow rate obtained in the flow path on the bypass side were each converted to the standard state (0 ° C., 1 atm), and the amount of carbon dioxide at the absorption liquid inlet was determined. The amount of carbon dioxide absorption is obtained from the difference in the amount of carbon dioxide between the absorption liquid inlet and the absorption liquid outlet.
15) Similarly, the amount of carbon dioxide at the outlet of the absorbent is obtained from the carbon dioxide concentration obtained at 120 ° C. and the gas flow rate, and from the difference in the amount of carbon dioxide at the inlet of the absorbent obtained in the bypass channel, Obtain carbon emissions.
16) In the case where water vapor is entrained in the mixed gas as an impurity, the valves C and D are switched to the constant temperature humidifier 405 side, and the mixed gas passes through the inside of the membrane tube controlled to 50 ° C., and is circulated to the outside. A mixed gas saturated with ion-exchanged water at 0 ° C. is prepared, sent to a reactor filled with a carbon dioxide absorbing solution, and the operations after 10) are performed.

(Example 1-1: MEA / 2-dimethylaminoethanol)
Monoethanolamine (MEA, 2-aminoethanol, manufactured by Sigma Aldrich, purity ≧ 99.0%) 1.01 g as a carbon dioxide chemically absorbing amine, and 2-dimethylaminoethanol (Aldrich) as a tertiary amine solvent Manufactured, purity ≧ 99.5%) 5.83 g were mixed to obtain a carbon dioxide absorbing liquid E1-1 (molar fraction 20%). The moisture content is 1% or less. The carbon dioxide absorption amount of the carbon dioxide absorbing liquid E1-1 was measured at normal pressure using the apparatus shown in FIG. The results are shown in FIG. The carbon dioxide absorbed at 10 ° C. was 125.91 (mol% / carbon dioxide chemically absorbing amine). The recovery rate of carbon dioxide absorbed at 10 ° C. at 80 ° C. was 83.67%.

(Examples 1-2 to 13)
Carbon dioxide absorbents E1-2 to E1 were used in the same manner as in Example 1-1, except that the tertiary amine solvent (molar fraction 20%) shown in Table 1 was used as the tertiary amine solvent instead of MDEA. -13 was obtained (molar fraction 20%). The low temperature side (10-150 degreeC) measured the carbon dioxide absorption amount of the carbon dioxide absorption liquid E1-2 to E1-13 at normal pressure using the apparatus shown in FIG. The results are shown in FIGS. In addition, E1-4 became two phases when carbon dioxide was absorbed. Moreover, E1-2 was 60 degreeC or more, E1-5 was 80 degreeC or more, E1-6 was 40 degreeC or more, and when it absorbed the carbon dioxide, it became two phases. Table 1 shows the recovery rate of carbon dioxide absorbed at 10 ° C. and carbon dioxide absorbed at 10 ° C. at 150 ° C.

  Moreover, the heat of reaction of the carbon dioxide absorption liquid E1-7 was measured. The measurement results are shown in FIG.

(Examples 2-1 to 17)
Carbon dioxide absorbents E2-1 to E2-17 are the same as Example 1-1 except that the amine (molar fraction 20%) shown in Table 2 was used as the carbon dioxide chemically absorbing amine instead of MEA. Was obtained (molar fraction 20%). The carbon dioxide absorption amount of the carbon dioxide absorbing liquids E2-1 to E2-17 was measured at normal pressure using the apparatus shown in FIG. The results are shown in FIGS. In E2-9, turbidity was observed at 10 to 100 ° C. In E2-17, turbidity was observed at 10 to 100 ° C. In E2-15, solid precipitation was observed at 80 ° C. to 100 ° C., and in E2-16, it solidified at 60 ° C. and did not melt to over 150 ° C. Table 1 shows the recovery rate of carbon dioxide absorbed at 10 ° C. and carbon dioxide absorbed at 10 ° C. at 150 ° C.

  Reaction heat was measured about the carbon dioxide absorption liquid E2-4, E2-6, E2-7, E2-10, E2-11, E2-14, and E2-16. The measurement results are shown in FIG.

(Examples 3-1 to 3-3: MMEA / MDEA)
N-methylethanolamine (MMEA, manufactured by Aldrich, 2- (methylamino) ethanol, purity ≧ 98.0%) 0.90 g as a carbon dioxide chemically absorbing amine, and methyldiethanolamine (MDEA) as a tertiary amine solvent The carbon dioxide absorption liquid E3-1 was obtained (14 mass%) by mixing 5.61 g, manufactured by Aldrich, purity ≧ 99.0%. The moisture content is 2% or less. In the same manner, carbon dioxide absorbing liquid E3-2 (30% by mass) and carbon dioxide absorbing liquid E3-3 (50% by mass) were obtained. The carbon dioxide absorption amount of the carbon dioxide absorbing liquids E3-1, E3-2, and E3-3 was measured at normal pressure using the apparatus shown in FIG. The results are shown in FIG.

(Examples 4-1 to 4-3: 2- (butylamino) ethanol / MDEA)
1.79 g of 2- (butylamino) ethanol (manufactured by Aldrich, purity ≧ 98.0%) as a carbon dioxide chemically absorbing amine and methyldiethanolamine (MDEA, manufactured by Aldrich, purity ≧ 99) as a tertiary amine solvent 0.02) 7.29 g was mixed to obtain a carbon dioxide absorbing solution E4-1 (20% by mass). The moisture content is 2% or less. Similarly, carbon dioxide absorbing liquid E4-2 (30 mass%) and carbon dioxide absorbing liquid E4-3 (50 mass%) were obtained. The carbon dioxide absorption amount of the carbon dioxide absorbing liquids E4-1, E4-2, and E4-3 was measured at normal pressure using the apparatus shown in FIG. The results are shown in FIG.

(Examples 5-1 to 5-3: diethylenetriamine / MDEA)
1.61 g of diethylenetriamine (Sigma Aldrich, purity ≧ 99.0%) as a carbon dioxide chemically absorbing amine and methyldiethanolamine (MDEA, Aldrich, purity ≧ 99.0%) as a tertiary amine solvent 7 .42 g was mixed to obtain a carbon dioxide absorbing liquid E5-1 (18% by mass). The moisture content is 2% or less. In the same manner, carbon dioxide absorbing liquid E3-2 (30% by mass) and carbon dioxide absorbing liquid E3-3 (50% by mass) were obtained. The carbon dioxide absorption amount of the carbon dioxide absorption liquids E5-1, E5-2, and E5-3 was measured at normal pressure using the apparatus shown in FIG. The results are shown in FIG.

(Examples 6-1 to 6-3: N- (2-hydroxyethyl) ethylenediamine / MDEA)
1.59 g of N- (2-hydroxyethyl) ethylenediamine (manufactured by Aldrich, purity ≧ 99.0%) as a carbon dioxide chemically absorbing amine and methyldiethanolamine (MDEA, manufactured by Aldrich, purity) as a tertiary amine solvent ≧ 99.0%) 7.33 g was mixed to obtain a carbon dioxide absorbing liquid E5-1 (18% by mass). The moisture content is 2% or less. In the same manner, carbon dioxide absorbing liquid E3-2 (30% by mass) and carbon dioxide absorbing liquid E3-3 (50% by mass) were obtained. The carbon dioxide absorption amount of the carbon dioxide absorption liquids E5-1, E5-2, and E5-3 was measured at normal pressure using the apparatus shown in FIG. The results are shown in FIGS.

(Example 7)
Monoethanolamine (MEA, 2-aminoethanol, manufactured by Sigma-Aldrich, purity ≧ 99.0%) 45.0115 g as a carbon dioxide chemically absorbing amine, and methyldiethanolamine (MDEA, manufactured by Aldrich) as a tertiary amine solvent , Purity ≧ 99.0%) 105.0151 g was mixed to obtain a carbon dioxide absorbing liquid E7-1 (30% by mass). The moisture content is 1% or less. Carbon dioxide absorption liquid E7-1 was used to perform a carbon dioxide absorption / release test under dry conditions with simulated coal combustion exhaust gas (12 mol% CO ₂ —N ₂ ). The results are shown in FIGS.

(Example 8)
Monoethanolamine (MEA, 2-aminoethanol, Sigma-Aldrich, purity ≧ 99.0%) 36.4403 g as a carbon dioxide chemically absorbing amine, and methyldiethanolamine (MDEA, manufactured by Aldrich) as a tertiary amine solvent , Purity ≧ 99.0%) was mixed with 85.0013 g to obtain a carbon dioxide absorbing liquid E8 (30 mass%). The moisture content is 1% or less. The carbon dioxide absorption / emission test of the simulated coal combustion exhaust gas (12 mol% CO ₂ —N ₂ ) was performed under humidification conditions using the carbon dioxide absorbing liquid E8, and the results are shown in FIGS.

Example 9
Monoethanolamine (MEA, 2-aminoethanol, manufactured by Sigma-Aldrich, purity ≧ 99.0%) 40.0276 g as a carbon dioxide chemically absorbing amine and N, N, N ′, N as a tertiary amine solvent '-Tetrakis (2-hydroxyethyl) ethylenediamine (manufactured by Sigma-Aldrich, purity 99.3%) 93.3696 g was mixed to obtain a carbon dioxide absorbing liquid E9 (30% by mass). The moisture content is 1% or less. The carbon dioxide absorption / emission test of the simulated coal combustion exhaust gas (12 mol% CO ₂ —N ₂ ) was performed under humidification conditions using the carbon dioxide absorbing liquid E9, and the results are shown in FIGS.

(Comparative Example 1: MEA / water)
Carbon dioxide absorption by mixing 0.67 g of ethanolamine (MEA, 2-aminoethanol, Sigma-Aldrich, purity ≧ 99.0%) as a carbon dioxide chemical absorbing amine and 5.15 g of ultrapure water as a solvent. A liquid R1 (molar fraction 20%) was obtained. The heat of reaction of the carbon dioxide absorbing liquid R1 was measured. The results are shown in FIG.

  Various embodiments and modifications can be made to the present invention without departing from the broad spirit and scope of the present invention. The above-described embodiments are for explaining the present invention and do not limit the scope of the present invention. In other words, the scope of the present invention is shown not by the embodiments but by the claims. Various modifications within the scope of the claims and within the scope of the equivalent invention are considered to be within the scope of the present invention.

101 Nitrogen or carbon dioxide cylinder 102 Pressure reducing valve 103 Flow meter 104 Valve 105 Heat exchanger 106 Valve 107 Heating medium 108 Constant temperature bath 109 Platinum temperature sensor 110 Resistance indicator 111 Cooling water circulation device 112 Reaction vessel 113 Rotor 114 Magnetic stirrer 115 Plug 116 Gas introduction pipe 117 Release pipe 201 Vacuum pump 202 Vacuum gauge 203 High pressure cell section 204 Gas chamber section 205 Constant temperature bath 206, 207, 208, 209, 210 Valve 211 Thermistor 212 Pressure gauge 213 Cooling water circulation device 214 Carbon dioxide cylinder 215 High-pressure cell 216 Stirrer 217 Stirrer 301 Carbon dioxide cylinder 302 Nitrogen cylinder 303 Cooling water circulation device 304 Syringe pump 305 Syringe pump 306 Thermostatic water tank 307 Thermometer 308 Calorimeter 309 Control PC 310 Pressure gauge 311 Temperature control jacket 401 Carbon dioxide cylinder 402 Nitrogen cylinder 403, 404 Mass flow controller 405 Constant temperature humidifier 406 Absorbing liquid injector 407 Reactor 408 Constant temperature bath 409 Controller 410 Stirrer 411 Stirring blade 412 Thermometer 413 Cooling water circulation device 414 Cooler 415 Pressure gauge 416 Carbon dioxide concentration meter 417 Data logger 418 Gas flow meter 409 PC for recording
A, B, C, D, E, F, G, I Valve

Claims (14)

A carbon dioxide chemically absorbing amine having a nitrogen-hydrogen bond and a tertiary amine solvent having no nitrogen-hydrogen bond,
The tertiary amine solvent having no nitrogen-hydrogen bond is rich in hydrogen bond acceptability, is also sterically stabilized, and promotes the reaction between the amine having the nitrogen-hydrogen bond and carbon dioxide. A tertiary polydentate amine having a main chain containing an oxygen atom and / or a nitrogen atom via a hydrocarbon group having 2 or more carbon atoms, and a total of 2 or more oxygen atoms and nitrogen atoms, and capable of high-temperature recovery Water-based carbon dioxide absorption solution. The tertiary polydentate amine is
A tertiary amine in which one hydrocarbon group having 2 or more carbon atoms in the main chain having a hydroxyl group and two unsubstituted hydrocarbon groups having 2 or more carbon atoms are bonded to one nitrogen atom;
A tertiary amine in which one hydrocarbon group having 3 or more carbon atoms in the main chain having a hydroxyl group and two unsubstituted hydrocarbon groups are bonded to one nitrogen atom;
A tertiary amine in which two hydrocarbon groups having 2 or more carbon atoms in the main chain having a hydroxyl group and one unsubstituted hydrocarbon group having 3 or more carbon atoms are bonded to one nitrogen atom, or an acyclic skeleton A tertiary amine having a diamine skeleton via an ethylene group, a propylene group, or a butylene group;
The carbon dioxide absorbing solution according to claim 1, wherein   The tertiary polydentate amine is N-butyldiethanolamine, N, N, N ′, N′-tetrakis (2-hydroxyethyl) ethylenediamine, or N, N, N ′, N′-tetrakis (2-hydroxypropyl). The carbon dioxide absorption liquid according to claim 1 or 2 which is ethylenediamine.   The carbon dioxide absorbing liquid according to claim 3, wherein the tertiary polydentate amine is N, N, N ', N'-tetrakis (2-hydroxyethyl) ethylenediamine.   The carbon dioxide absorbing solution according to claim 1, wherein the tertiary polydentate amine is N-methyldiethanolamine, N-ethyldiethanolamine, or triethanolamine.   The carbon dioxide absorbing liquid according to any one of claims 1 to 5, wherein the carbon dioxide chemically absorbing amine having a nitrogen-hydrogen bond further has a hydrocarbon group having a hydroxyl group.   The carbon dioxide chemically absorbing amine having a nitrogen-hydrogen bond is 4-amino-1-butanol, N-methylethanolamine, 3-methylamino-1-propanol, 2- (ethylamino) ethanol, 2- ( The carbon dioxide absorbing solution according to claim 6, which is (butylamino) ethanol, monoethanolamine, or diethanolamine.   The carbon dioxide absorbing liquid according to claim 7, wherein the carbon dioxide chemically absorbing amine having a nitrogen-hydrogen bond is diethanolamine.   The carbon dioxide chemical-absorbing amine having a nitrogen-hydrogen bond has an oxygen atom and / or a nitrogen atom via a hydrocarbon group having 2 or more carbon atoms in the main chain. The carbon dioxide absorbing solution according to item.   The carbon dioxide chemical-absorbing amine having a nitrogen-hydrogen bond has a diamine skeleton having a nitrogen atom via a hydrocarbon group having 2 or more carbon atoms in the main chain. The carbon dioxide absorption liquid according to item 1.   The carbon dioxide chemically absorbing amine having a nitrogen-hydrogen bond is a polyamine having two or more diamine skeletons having a nitrogen atom via a hydrocarbon group having 2 or more carbon atoms in the main chain. Carbon dioxide absorption liquid.   The carbon dioxide chemically absorbing amine having a nitrogen-hydrogen bond is ethylenediamine, piperazine, N-hexylethylenediamine, N- (2-hydroxyethyl) ethylenediamine, N- (2-hydroxyisopropyl) ethylenediamine, N, N′-. With bis (2-hydroxyethyl) ethylenediamine, diethylenetriamine, tris (2-aminoethyl) amine, 1- (2-aminoethyl) piperazine, triethylenetetramine, or 1,2-bis (3-aminoproplamino) ethane The carbon dioxide absorption liquid according to any one of claims 9 to 11, wherein   The carbon dioxide absorbing solution according to any one of claims 1 to 12, wherein the water content is less than 5% by mass. The carbon dioxide absorbing liquid according to any one of claims 1 to 13 is brought into contact with a mixed gas containing carbon dioxide at 50 ° C or lower so that carbon dioxide is absorbed by the carbon dioxide absorbing liquid, and the mixed gas is used. An absorption step of selectively separating carbon dioxide from the carbon dioxide, and 90% or more of the absorbed carbon dioxide is diffused and recovered by heating the carbon dioxide absorbing solution that has absorbed the carbon dioxide to 120 ° C or higher, A carbon dioxide separation and recovery method comprising a heating regeneration step of regenerating the carbon absorbing liquid.