JP6685547B2 - Carbon dioxide absorption liquid and carbon dioxide separation and recovery method - Google Patents

Description

  The present invention relates to a carbon dioxide absorbent 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 absorption liquid has been put into practical use. In the process of this chemical absorption method, a gas containing an acidic gas is brought into contact with the absorbing liquid in the vicinity of room temperature in the absorption tower to selectively chemically absorb the acidic gas into the absorbing liquid, thereby reducing the concentration of the acidic gas. And the absorption liquid that has absorbed the acidic gas are separated into gas and liquid, and in the regeneration tower, the absorption liquid that has absorbed the acidic gas is heated to diffuse and recover the acidic gas, and at the same time, the absorption liquid is regenerated and circulated. To use.

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

For example, Patent Document 1 describes a circulation method for separating CO ₂ from a gas stream, including a step of contacting the gas stream with an alkanolamine CO ₂ absorbent and an absorbent containing a non-nucleophilic base. Has been done. The example of Patent Document 1 describes an alkanolamine and tetramethylguanidine as a non-nucleophilic base. In addition, 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 listed.

Special table 2013-542060 gazette Special Table 2011-521778

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

  Therefore, the problem to be solved by the present invention is that the amount of absorption at room temperature is larger than that of the conventional amine aqueous solution, and the desorption property at high temperature is excellent, the evaporation loss of the absorbing liquid is small, the specific heat is low, and the reaction heat is small. The purpose of the present invention is to provide a carbon dioxide absorbent that can reduce the energy required to regenerate the carbon dioxide absorbent 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 accepting property and a three-dimensional structure in the vicinity of room temperature. Also stabilizes and accelerates the reaction between carbon dioxide and amines, facilitates the release of carbon dioxide at high temperatures, and when a specific secondary amine is used as a carbon dioxide absorbent, the heat of reaction with carbon dioxide becomes The absorption rate of carbon dioxide is high when a polydentate amine having a plurality of specific oxygen atoms and nitrogen atoms is used, and such an absorption liquid is close to room temperature as compared with a conventional amine aqueous solution. Absorbs a large amount of carbon dioxide, and the absorption liquid can be handled at high temperatures, and at that high temperature, carbon dioxide is easily desorbed, the evaporation loss of the absorption liquid is small, and the regeneration energy of the carbon dioxide absorption liquid is high. 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) Includes a carbon dioxide chemically absorbing amine having a nitrogen-hydrogen bond, and a tertiary amine solvent having no nitrogen-hydrogen bond,
The carbon dioxide chemisorbable amine having a nitrogen-hydrogen bond is an amine represented by the formula 8 having an oxygen atom and / or a nitrogen atom via a hydrocarbon group having 2 or more carbon atoms in the main chain,
(In Formula 8, R ¹ is an unsubstituted or substituted hydrocarbon group or hydrogen, n5 is an integer of 2 or more. The carbon atom in the parentheses has a substituent. X represents —OR ⁵ , —N (R ⁶ ) R ^7, and is a nitrogen atom or an oxygen atom, and hydrogen bonded to them or an unsubstituted or substituted hydrocarbon group. (R ⁵ , R ⁶ , and R ⁷ are an unsubstituted or optionally substituted hydrocarbon group or hydrogen.)
The tertiary amine solvent having no nitrogen-hydrogen bond has a high hydrogen bond accepting property and is stable in a three-dimensional structure, so that the reaction between the carbon dioxide chemically absorbing amine having a nitrogen-hydrogen bond and carbon dioxide is performed. In order to promote, the main chain has 2 or more carbon atoms, has an oxygen atom and / or a nitrogen atom via a hydrocarbon group , which constitutes an acyclic skeleton, and the total number of oxygen atoms and nitrogen atoms is 2 or more. Ri Oh tertiary multidentate amines, which can be high temperature recovery, the carbon dioxide absorption liquid nonaqueous a moisture content of less than 10 wt%.

(2) The amine represented by the above formula 8 having an oxygen atom and / or a nitrogen atom through a hydrocarbon group whose main chain has 2 or more carbon atoms,
An amine represented by formula 9, in which one nitrogen atom is bound to two hydrogen atoms and one hydrocarbon group having a hydroxyl group,
(In formula 9, n6 is an integer of 2 or more. The carbon atom in the parenthesis may have a substituent.)
An amine represented by the formula 10, in which one nitrogen atom, one hydrocarbon group having a hydroxyl group and one hydrocarbon group having no hydroxyl group are bonded to one nitrogen atom,
(In the formula 10, R ⁷ is a hydrocarbon group which may be unsubstituted or may have a substituent (excluding a hydroxyl group) , n ⁷ is an integer of 2 or more. The carbon atom in the parenthesis has a substituent. You may have.)
An amine represented by Formula 11, in which one hydrogen atom and two hydrocarbon groups having a hydroxyl group are bonded to one nitrogen atom, and
(In formula 11, n8 and n9 are integers of 2 or more. The carbon atom in the parenthesis may have a substituent.)
One nitrogen atom represented by formula 12 is at least one selected from the group consisting of a hydrogen atom and an amine having a nitrogen atom through a hydrocarbon group having 2 or more carbon atoms in the main chain , The carbon dioxide absorbent according to (1).
(In the formula 12, R ⁸ , R ⁹ and R ¹⁰ are hydrocarbon groups which may be unsubstituted or may have a substituent, n10 is an integer of 2 or more. The carbon atom in the parentheses is a substituent. You may have.)
The carbon dioxide absorbent according to (1) above , which is at least one selected from the group consisting of:

(3) The tertiary polydentate amine is
Tertiary amine in which one nitrogen atom has one hydrocarbon group having a hydroxyl group in the main chain of 2 or more carbon atoms and two unsubstituted hydrocarbon groups having 2 or more carbon atoms,
A tertiary amine in which one nitrogen atom has one hydrocarbon group having a hydroxyl group in the main chain of 3 or more carbon atoms and two unsubstituted hydrocarbon groups,
A tertiary amine in which two nitrogen-containing hydrocarbon groups having a hydroxyl-containing main chain and one unsubstituted hydrocarbon group having three or more carbon atoms are bonded to one nitrogen atom, or
Tertiary amines having a diamine skeleton through an ethylene group, a propylene group, or a butylene group constituting an acyclic skeleton,
The carbon dioxide absorbent according to (1) or (2) above , which is

(4) 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 absorbent according to (3) above , which is hydroxypropyl) ethylenediamine .

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

(6) The carbon dioxide absorbent according to (1) or (2) , wherein the tertiary polydentate amine is N-methyldiethanolamine, N-ethyldiethanolamine, or triethanolamine .

(7) before Ki窒 containing - carbon dioxide chemical absorption amine having a hydrogen bond includes a hydrocarbon group having a hydroxyl group, the (1) carbon dioxide absorbing liquid according to any one of - (6).

(8) before Ki窒 containing - carbon dioxide chemical absorption amine having a hydrogen bond, 4-amino-1-butanol, N- methylethanolamine, 3-methylamino-1-propanol, 2- (ethylamino) ethanol The carbon dioxide absorbent according to (7) above , which is 2- (butylamino) ethanol, monoethanolamine, or diethanolamine .

(9) before Ki窒 containing - carbon dioxide chemical absorption amines having hydrogen bonds are diethanolamine, carbon dioxide absorbing solution according to (8).

(10) before Ki窒 containing - carbon dioxide chemical absorption amine having a hydrogen bond, carbon atoms in the main chain has a diamine skeleton having a nitrogen atom through a 2 or more hydrocarbon groups, wherein (1) - ( The carbon dioxide absorbent according to any one of 6) .

(11) before Ki窒 containing - carbon dioxide chemical absorption amine having a hydrogen bond is a polyamine carbon atoms in the main chain has 2 or more diamines skeleton having a nitrogen atom through a 2 or more hydrocarbon groups, the The carbon dioxide absorbent according to (10).

(12) before Ki窒 containing - carbon dioxide chemical absorbent amine having hydrogen bonding, ethylenediamine, N - hexyl ethylenediamine, N- (2- hydroxyethyl) ethylenediamine, N-(2-hydroxy isopropyl) ethylenediamine, N, N '- bis (2-hydroxyethyl) ethylenediamine, diethylenetriamine, tris (2-aminoethyl) amine, preparative triethylene tetramine, or 1,2-bis (3-aminopropionic pull amino) ethane, the (10) or ( The carbon dioxide absorbent according to 11) .

(13) The ratio of the carbon dioxide chemically absorbing amine having the nitrogen-hydrogen bond and the tertiary amine solvent not having the nitrogen-hydrogen bond in the carbon dioxide absorbing liquid is the carbon dioxide having the nitrogen-hydrogen bond. Chemically absorbable amine / (carbon dioxide chemically absorbable amine having the nitrogen-hydrogen bond + the tertiary amine solvent not having the nitrogen-hydrogen bond) (mass ratio), which is 1/100 to 50/100. The carbon dioxide absorbent according to any one of (1) to (12).

(14) Absorb carbon dioxide into the carbon dioxide absorbent by contacting the carbon dioxide absorbent according to any one of (1) to (13) with a mixed gas containing carbon dioxide at 50 ° C. or less. Then, the absorption step of selectively separating carbon dioxide from the mixed gas, and by heating the carbon dioxide absorption liquid having absorbed the carbon dioxide to 120 ° C. or higher, 90% or more of the absorbed carbon dioxide is diffused. A method of separating and recovering carbon dioxide, which comprises a heating and regenerating step of recovering the carbon dioxide absorbent by regenerating the carbon dioxide absorbent.

  The carbon dioxide absorbing solution of the present invention has a large absorption amount near room temperature as compared with a conventional amine aqueous solution, and is excellent in easy desorption at high temperature, has a small evaporation loss of the absorbing solution, has a low specific heat, and has a heat of reaction. It is small and it is possible to reduce the energy required to regenerate the carbon dioxide absorbent 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 measurement). The figure which shows a carbon dioxide reaction heat measuring apparatus. The figure which shows a carbon dioxide absorption / emission test apparatus (temperature swing type). The graph which shows the carbon dioxide absorption amount of the carbon dioxide absorption liquid (MEA / various solvent) 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. Heat of reaction of each carbon dioxide absorption liquid. The graph which shows the carbon dioxide absorption amount of the carbon dioxide absorption liquid of Examples 3-1 to 3-3 and Examples 4-1 to 4-3. The graph which shows the carbon dioxide absorption amount of the carbon dioxide absorption liquid of Examples 5-1 to 5-3 and Examples 6-1 to 6-3. The graph which shows the carbon dioxide absorption amount of the carbon dioxide absorption liquid of Examples 5-1 to 5-3 and Examples 6-1 to 6-3. 6 is a graph showing the results of carbon dioxide absorption (50 ° C.) in an impurity test (with water vapor components). The graph which shows the result of carbon dioxide emission (120 degreeC) in an impurity test (water vapor | steam component entrainment).

  The carbon dioxide absorbing liquid of the present invention is a non-aqueous carbon dioxide absorbing liquid that can be recovered at high temperature, and comprises a carbon dioxide chemically absorbing amine having a nitrogen-hydrogen bond and a tertiary amine solvent having no nitrogen-hydrogen bond. including. The tertiary amine solvent having no nitrogen-hydrogen bond is rich in hydrogen bond accepting property, is stable in three-dimensional structure, and promotes the reaction between the amine having a nitrogen-hydrogen bond and carbon dioxide. It is a tertiary polydentate amine having an oxygen atom and / or a nitrogen atom through a hydrocarbon group having 2 or more carbon atoms in the chain and having a total of 2 or more oxygen atoms and nitrogen atoms.

  The "non-aqueous system" means that the carbon dioxide absorbent of the present invention contains substantially no water, preferably the water content is less than 10% by mass, more preferably less than 5% by mass, particularly preferably It is less than 3% by mass.

  “Recoverable at high temperature” means that the carbon dioxide absorbing liquid of the present invention which 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, more preferably Is heated to 120 ° C. or higher, more preferably 140 ° C. or higher, and particularly preferably 150 ° C. or higher to release carbon dioxide as a gas from the carbon dioxide absorption liquid and to separate it, preferably 50% of carbon dioxide absorbed at 10 ° C. Mol% or more, more preferably 70 mol% or more, and particularly preferably 90 mol% or more, can be separated, the absorption liquid is required to be stable at these temperatures, the boiling point at normal pressure of the absorption liquid, these It is preferable that the temperature is higher than. The phrase "recoverable at a high temperature" does not mean that the carbon dioxide release temperature of the carbon dioxide absorbent of the present invention is limited. The carbon dioxide absorbent of the present invention can release carbon dioxide at a temperature higher than the temperature at which it absorbs carbon dioxide.

(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 stable in a three-dimensional structure, and promotes the reaction between carbon dioxide chemisorbed amine and carbon dioxide. In addition, it is a tertiary polydentate amine having an oxygen atom and / or a nitrogen atom through a hydrocarbon group having 2 or more carbon atoms in the main chain, and having a total of 2 or more oxygen atoms and nitrogen atoms. Here, “rich in hydrogen bond accepting property, stabilizing also in three-dimensional structure, and promoting reaction of carbon dioxide chemisorbable amine with carbon dioxide” means, for example, as shown in Formula 1, tertiary polydentate A nitrogen atom or an oxygen atom of an amine interacts with hydrogen of a carbon dioxide chemisorbable amine in a multidentate manner to stabilize a reaction product with carbon dioxide.

In formula 1, the 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 an unsubstituted or substituted group. R ² is an optionally substituted hydrocarbon group or hydrogen, R ² is an unsubstituted or optionally substituted hydrocarbon group.

In Formula 1, the compound represented by X ¹ R ⁵ N (R ³ ) R ⁴ represents the tertiary polydentate amine according to the present invention, and R ³ and R ⁴ are unsubstituted or have a substituent. Optionally a hydrocarbon group, R ⁵ is a hydrocarbon group having 2 or more carbon atoms in the main chain, which may be unsubstituted or may have a substituent, and X ¹ is a nitrogen atom or an oxygen atom and those Is a hydrogen atom bonded to or a hydrocarbon group which may be unsubstituted or may have a substituent. In the present specification, a 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 the oxygen atom is an ethylene group or a propylene group. , Butylene group and the like have 2 or more carbon atoms. Therefore, for example, an amine having a main chain hydrocarbon of 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. As the hydrocarbon group having 2 or more carbon atoms in the main chain, an ethylene group, a propylene group, or a butylene group forming a non-cyclic skeleton having a high degree of freedom is preferable, and an ethylene group is more preferable.

An electron-donating oxygen atom or nitrogen atom has a high hydrogen bond accepting property, and can interact with hydrogen of a carbon dioxide chemically absorbing amine to stabilize a reaction product with carbon dioxide. Since the hydrocarbon group having a carbon number of 2 or more in the main chain represented by R ⁵ and a curve in Formula 1 has a high degree of freedom, the nitrogen atom and / or the nitrogen atom bonded to both ends of the hydrocarbon group is carbon dioxide. The hydrogen of the chemisorbable amine may be included. Such a tertiary polydentate amine promotes a reaction with carbon dioxide by including and stabilizing hydrogen of a carbon dioxide chemically absorbing amine on a relatively low temperature side such as near room temperature where carbon dioxide is absorbed. . Further, the hydrogen bonded to X ¹ can form a hydrogen bond with carbon dioxide that has reacted with the carbon dioxide chemically absorbing amine, and can further stabilize the reaction product and promote the reaction with carbon dioxide. On the other hand, on the high temperature side where carbon dioxide is released, the degree of inclusion is reduced, so that the release of carbon dioxide can be promoted.

  In the present specification, when a plurality of nitrogen atoms are present in one molecule and the nitrogen atoms have different series, the series of amine is the higher series. For example, a tertiary nitrogen atom (having 3 hydrocarbon groups bonded to the nitrogen atom) and a secondary nitrogen atom (having 2 hydrocarbon groups bonded to the nitrogen atom and 1 hydrogen atom bonded to each other in one molecule) Is present, the amine is a tertiary amine. Therefore, in the case of this example, it is a tertiary amine having a hydrogen-nitrogen bond, and is not a tertiary amine solvent but is classified as a carbon dioxide chemically absorbing amine. The nitrogen-carbon double bond defines a series as having two hydrocarbon groups bonded to the nitrogen atom.

The tertiary polydentate amine used as the tertiary amine solvent in the present invention is rich in hydrogen bond acceptability, stabilized also in three-dimensional structure, and promotes the reaction between carbon dioxide chemisorbable amine and carbon dioxide. There is no particular limitation as long as it is a tertiary amine having an oxygen atom and / or a nitrogen atom through 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 the formula 2 in which one nitrogen atom-containing hydrocarbon group and two hydroxyl group-free hydrocarbon groups are bonded to one nitrogen atom;
(In Formula 2, R ³ and R ⁴ are hydrocarbon groups which may be unsubstituted or may have a substituent (excluding a hydroxyl group), n1 is an integer of 2 or more, and carbon atoms in parentheses are 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 the formula 3 in which two nitrogen-containing hydrocarbon groups and one non-hydroxyl-containing hydrocarbon group are bonded to one nitrogen atom;
(In Formula 3, R ³ is a hydrocarbon group which may be unsubstituted or has a substituent (excluding a hydroxyl group), n1 and n2 are integers of 2 or more, and the carbon atom in the parentheses is a substituent. May be included, and a part of carbon atoms may be substituted with a hetero atom.)
A tertiary polydentate amine represented by the formula 4 in which three hydrocarbon groups having a hydroxyl group are bonded to one nitrogen atom;
(In the formula 4, n1, n2, and n3 are integers of 2 or more, the carbon atom in the parentheses may have a substituent, and a part of the carbon atom may be substituted with a hetero atom. Good.)

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

  Here, in the present specification, unless otherwise specified, the hydrocarbon group includes, for example, an unsubstituted or halogen group, an alkyl group having a substituent such as a hydroxyl group, an alkenyl group, and an alkynyl group, which are cyclic. May be acyclic and may have a heteroatom in the skeleton. Among them, 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.

Examples of the tertiary polydentate amine represented by the formula 2 in which one hydrocarbon group having a hydroxyl group and two hydrocarbon groups having no hydroxyl group are bonded to one nitrogen atom include 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 the formula 2, R ³ and R ⁴ are tertiary amines having a hydrocarbon group of 2 or more carbon atoms, that is, hydrocarbons having a main chain having a hydroxyl group at one nitrogen atom of 2 or more carbon atoms. A tertiary amine in which one group is bonded to two hydrocarbon groups having 2 or more carbon atoms, or a tertiary amine in which n1 is an integer of 3 or more in Formula 2, that is, has a hydroxyl group at one nitrogen atom. 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, and 2- (dibutylamino) ethanol, and 3-dimethylamino-1-propanol and 4- (dimethylamino) -1-butanol, etc. Is mentioned.

Examples of the tertiary polydentate amine represented by the formula 3 in which two nitrogen-containing hydrocarbon groups and one non-hydroxyl-containing hydrocarbon group are bonded to one nitrogen atom include, for example, N-methyldiethanolamine ( MDEA), N-ethyldiethanolamine ((Et) N (EtOH) ₂ ), N-butyldiethanolamine ((n-Bu) N (EtOH) ₂ ).

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

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

Examples of the tertiary amine represented by Formula 5 having a diamine skeleton having two nitrogen atoms through a hydrocarbon group having 2 or more carbon atoms include, for example, N, N, N ′, N′-tetramethylethylenediamine (( Me) ₂ N (C ₂ H ₄ ) N (Me) ₂ ), or a nitrogen atom 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 H4) N (EtOH) 2), N, N, N', N'- tetrakis (2- Hydroxypropyl) ethylenediamine ((i-PrOH) ₂ N (C ₂ H ₄ ) N (i-PrOH) ₂ ) and the like having a diamine skeleton through an ethylene group, a propylene group, or a butylene group constituting an acyclic skeleton. Tertiary amine It is below. Among them, N, N, N ', N'-tetrakis (2-hydroxyethyl) ethylenediamine is preferable.

(Carbon dioxide chemical absorption amine)
The carbon dioxide chemisorbable amine used in the present invention has a nitrogen-hydrogen bond. Amines with nitrogen-hydrogen bonds can react with carbon dioxide to form carbamate salts (Formula 6-1). In addition, proton transfer occurs between the generated carbamate salt and the unreacted amine (formula 6-2), and the reaction between the carbon dioxide chemisorbable amine and carbon dioxide is stoichiometrically 2: 1. (Equation 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. The carbon dioxide chemisorbable amine that has absorbed carbon dioxide releases carbon dioxide at a temperature higher than the temperature at which it absorbs carbon dioxide, preferably at a high temperature of 100 ° C. or 150 ° C., and the carbon dioxide chemisorbable amine is regenerated. To be 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 of the hydrogen atoms of ammonia represented by the formula 7 are substituted with a hydrocarbon group. Are amines having a primary or secondary nitrogen atom.
(In the formula 7, R ¹ is an unsubstituted or substituted hydrocarbon group or hydrogen, and R ² is an unsubstituted or substituted hydrocarbon group. Some of the carbon atoms in the hydrogen group may be replaced by hetero atoms.)

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

More specifically, an amine represented by the formula 9 in which one nitrogen atom is bonded to two hydrogen atoms and one hydrocarbon group having a hydroxyl group;
(In formula 9, n6 is an integer greater than or equal to 2. The carbon atom in parenthesis may have a substituent, and some carbon atoms may be substituted by the hetero atom.)

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

An amine represented by the formula 11 in which one nitrogen 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 the parenthesis may have a substituent, and a part of the carbon atom may be substituted with a hetero atom.)

Examples of the amine represented by Formula 12 include a hydrogen atom and an amine having a diamine skeleton having a nitrogen atom through a hydrocarbon group of which main chain has 2 or more carbon atoms.
(In the formula 12, R ⁸ , R ⁹ and R ¹⁰ are hydrocarbon groups which may be unsubstituted or may have a substituent, n10 is an integer of 2 or more. The carbon atom in the parentheses is a substituent. It may have and a part of carbon atoms may be substituted with a hetero atom.)

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

  An amine represented by formula 10 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 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 can be mentioned.

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

As the amine having a diamine skeleton represented by the formula 12 and having a hydrogen atom and a nitrogen atom through a hydrocarbon group having 2 or more carbon atoms in the main chain, alkylenes such as ethylenediamine (EDA) and piperazine (PZ) are used. 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, alkylenediamine having a hydroxyalkyl group such as N'- bis (2-hydroxyethyl) ethylenediamine _{(EtOHNH (C 2 H 4)} NHEtOH); 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 each having a nitrogen atom through a hydrocarbon group having a main chain having 2 or more carbon atoms, such as HN (C ₂ H ₄ ) HN (C ₃ H ₆ ) NH ₂ ). In addition, in this specification, "having two or more diamine skeletons" includes the case where nitrogen atoms of the diamine skeleton are common such as diethylenetriamine.

  The carbon dioxide chemical-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, which may further have a substituent such as a halogen group. The hydrocarbon group having a hydroxyl group is preferably a hydroxyalkyl group. An amine having a hydroxyalkyl group is also called an alkanolamine. Examples of hydroxyalkyl groups include hydroxymethyl, hydroxyethyl, hydroxypropyl, hydroxy-i-propyl, and hydroxybutyl groups. Among them, those having 2 or 3 or more carbon atoms are preferable, and the hydroxyethyl group is particularly preferable.

  Specific examples of the carbon dioxide chemically absorbing amine having a hydrocarbon group having a hydroxyl group as well as having a nitrogen-hydrogen bond 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 , Dipropanolamine and the like. Among them, secondary amines or primary amines having a hydroxyl group-containing hydrocarbon group having 2 or more carbon atoms bonded to a nitrogen atom are preferable, since they have a high efficiency of carbon dioxide separation and recovery as a carbon dioxide absorbing liquid, and have 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 absorbent of the present invention contains the carbon dioxide chemically absorbing amine having the nitrogen-hydrogen bond described above and the tertiary amine solvent having no nitrogen-hydrogen bond described above. The carbon dioxide chemical-absorbing amine and the tertiary amine solvent used in the present invention are usually liquids at room temperature, and the carbon dioxide-absorbing liquid of the present invention is a mixture of the carbon dioxide chemical-absorbing amine and the tertiary amine solvent. Obtained by

  The combination of the carbon dioxide chemical-absorbing amine and the tertiary amine solvent is not particularly limited, but when the carbon dioxide chemical-absorbing amine is monoethanolamine, the tertiary amine solvent is a main chain having a hydroxyl group at one nitrogen atom. Tertiary amine having one hydrocarbon group having 2 or more carbon atoms and two unsubstituted hydrocarbon groups having 2 or more carbon atoms; one nitrogen atom has 3 or more carbon atoms in the main chain having a hydroxyl group 1-hydrocarbon group and two unsubstituted hydrocarbon groups bonded to each other; a single nitrogen atom, a hydrocarbon group having a hydroxyl group having two or more carbon atoms in the main chain, and a non-substituted A tertiary amine having one bonded hydrocarbon group having 3 or more carbon atoms; or a tertiary amine having a diamine skeleton through an ethylene group, a propylene group, or a 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 has an oxygen atom and / or a nitrogen atom via a hydrocarbon group whose main chain has 2 or more carbon atoms. It is preferably an amine having atoms. 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 puramino) ethane is preferred.

  The ratio of the carbon dioxide chemical-absorbing amine and the tertiary amine solvent in the carbon dioxide-absorbing liquid is not particularly limited and may be appropriately selected depending on these types, but the carbon dioxide chemical-absorbing amine / (carbon dioxide chemical-absorbing amine +3 Primary 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 absorbable amine is within this range, the carbon dioxide absorption amount near room temperature can be increased and the carbon dioxide easiness of removal at high temperature can be improved.

  The carbon dioxide absorbing liquid of the present invention is a non-aqueous carbon dioxide absorbing liquid and contains substantially no water. Specifically, the water content of the carbon dioxide absorbent 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.

(Method of separating and collecting carbon dioxide)
The carbon dioxide absorbent 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. Other components include acidic gases other than carbon dioxide, nitrogen gas, oxygen gas, water, dust and the like. Examples of acidic gases other than carbon dioxide include hydrogen sulfide; sulfur oxides such as sulfur monoxide, sulfur dioxide (sulfurous acid gas) and sulfur trioxide; nitric oxide, nitrogen dioxide, nitrous oxide (dinitrogen monoxide). , Nitrogen oxides such as dinitrogen trioxide, dinitrogen tetraoxide and dinitrogen pentoxide; inorganic acids such as hydrochloric acid, nitric acid, phosphoric acid and sulfuric acid; organic acids such as carboxylic acid, sulfonic acid and carbonic acid. The carbon dioxide absorbent of the present invention has little effect on carbon dioxide recovery even if the mixed gas contains a saturated amount of water as another component. Further, the carbon dioxide absorbent of the present invention has little influence on the carbon dioxide recoverability even if the mixed gas contains soot and dust as other components.

Next, a method of separating and recovering carbon dioxide using the carbon dioxide absorbent of the present invention will be described.
The carbon dioxide separation and recovery method of the present invention, by contacting the carbon dioxide absorption liquid with a mixed gas containing carbon dioxide, allows the carbon dioxide absorption liquid to absorb carbon dioxide, and selects carbon dioxide from the mixed gas. Absorption step that separates the carbon dioxide and the carbon dioxide absorption solution that has absorbed the carbon dioxide is heated to a higher temperature than the absorption step to dissipate and collect the absorbed carbon dioxide and regenerate the carbon dioxide absorption solution. The process is included. The carbon dioxide absorbing liquid of the present invention has a large absorption amount near room temperature, and is excellent in easy desorption at high temperature, has a small evaporation loss, has a low specific heat, and has a small reaction heat, and therefore, per carbon dioxide to be recovered, The energy required to regenerate the carbon dioxide absorbent can be reduced.

  The temperature of the carbon dioxide absorbent in the absorption step is not particularly limited as long as the lower limit does not solidify the carbon dioxide absorbent, but is preferably 60 ° C or lower, preferably 40 ° C or lower, and more preferably around room temperature (20 ° C ± 20 ° C). A temperature of 10 ° C. or lower is particularly preferable. The lower the temperature of the carbon dioxide absorbent in the absorption step, the more the absorption amount of carbon dioxide tends to increase. Since the carbon dioxide separation and recovery method of the present invention chemically absorbs carbon dioxide into the carbon dioxide absorption liquid, the pressure of the absorption step is not particularly limited, but the solubility of carbon dioxide in the carbon dioxide absorption liquid and the carbon dioxide absorption From the viewpoint of preventing loss due to entrainment of the carbon absorbing liquid, the atmospheric pressure or higher is usually preferable, and it can be used even under high pressure conditions such as 1 MPa to 6 MPa.

  The temperature of the carbon dioxide absorbing solution in the heating regeneration step is not particularly limited as long as it is higher than the temperature in the absorbing 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 higher. The larger the temperature difference, the higher the ratio of the carbon dioxide absorbed in the absorption step can be recovered. The temperature of the carbon dioxide absorbent in the more specific heat regeneration step is preferably 50 ° C or higher, more preferably 80 ° C or higher, even more preferably 120 ° C or higher, and particularly preferably 150 ° C or higher. Since the carbon dioxide absorbent 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 amine aqueous solution. The upper limit of the temperature of the carbon dioxide absorbent in the heating regeneration step is not particularly limited, but it is preferably 200 ° C or lower, more preferably 180 ° C or lower, still more preferably 160 ° C or lower. Since the carbon dioxide separation and recovery method of the present invention recovers carbon dioxide by chemically dissipating and recovering carbon dioxide, the pressure in the heating regeneration step is not particularly limited, but carbon dioxide is dissipated from the carbon dioxide absorption liquid. In terms of properties, it is preferable to make the pressure equal to or lower than the pressure of the absorption step, and it is also possible to make it higher than the pressure of the absorption step.

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

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

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

  The carbon dioxide absorbent of the present invention and the method for separating and recovering carbon dioxide using the same are excellent in separating and recovering carbon dioxide, but can also be used for separating and recovering acidic gas other than carbon dioxide.

(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 method. Pressures are absolute unless otherwise noted.
(Measuring method)

(1) Carbon dioxide absorption (normal pressure blowing type)
The measurement was performed at normal pressure using the carbon dioxide absorption test apparatus shown in FIG. The carbon dioxide absorption test apparatus includes 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 containing the heating medium 107, 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 The cooling water circulating device 111 for adjusting the temperature to the above, and the magnetic stirrer 114 for rotating the rotor 113 placed in the reaction vessel 112 are provided.
A stopper 115, a gas introduction pipe 116, and a valved discharge pipe 117 can be attached to the reaction vessel 112. The valve 106 can be connected to a gas introduction pipe 116 attached to the reaction container 112. The heat exchanger 105 and the reaction container 112 are immersed in the heat medium 107 of the constant temperature bath 108 and kept at a constant temperature by the cooling water circulation device 111. A rotor 113 is placed in the reaction container 112, and the carbon dioxide absorbing liquid in the reaction container 112 can be stirred by the magnetic stirrer 114. As the heat medium 107, water is used when measuring at 10 ° C. or higher and 80 ° C. or lower, and oil is used when measuring at 80 ° C. or higher and 150 ° C. or lower.
Below, the carbon dioxide absorption measurement procedure using this carbon dioxide absorption test apparatus is described.
1) Under a nitrogen atmosphere, a predetermined amount (about 10 cc) of carbon dioxide absorption liquid is dispensed into a glass reaction container 112, and the mouth of the reaction container 112 is sealed with a stopper 115. The mass of the entire reaction container is measured with an analytical balance, and the mass of the tare (reaction container 112, rotor 113, and stopper 115) is subtracted from this to obtain the mass W _total of the carbon dioxide absorbing liquid.
2) The gas inlet pipe 116 and the discharge pipe 117 are attached to the reaction container 112, and the mass is measured again to obtain the mass W ₂ of the entire reaction container.
3) The reaction container 112 is installed in the constant temperature bath 108. The gas introduction pipe 116 is connected to the valve 106.
4) The temperature of the constant temperature bath 108 is kept at 40 ° C., carbon dioxide is passed through the reaction vessel 112, and the carbon dioxide absorption liquid absorbs carbon dioxide. The mass of the entire reaction vessel is measured with an analytical balance at regular intervals (for example, 60 minutes). Let W ₃ be the mass of the entire reaction container when the mass change for each measurement is 0.001 g or less.
5) The mass W _CO2 of carbon dioxide absorbed in the carbon dioxide absorption liquid is calculated based on the following formula.
W _CO2 = W ₃ −W ₂
Further, the carbon dioxide absorption amount α _CO2 per mol 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 calculated by multiplying the _total by the mass fraction x ₁ .
6) The temperature of the constant temperature bath 108 is appropriately changed, 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 carbon dioxide absorbed at 40 ° C. is measured again to confirm reproducibility.

(2) Carbon dioxide absorption (high-pressure closed cell)
In the atmospheric pressure blowing type measurement method of (1), especially when the vapor pressure of the solvent is high, the solvent is discharged together with carbon dioxide gas from the reaction vessel, and the absorption amount of carbon dioxide cannot be accurately measured. Sometimes. Since the carbon dioxide absorbing liquid composed of MEA / water of Comparative Example 1 has a high vapor pressure of water, as shown in FIG. 2, the reaction vessel 112 is replaced with a high pressure cell (pressure cell) 215 which is a pressure vessel, and the stopper 115 is used. In place of the gas introduction pipe 116 and the discharge pipe 117, a gas introduction pipe with a valve and a pressure-proof stopper whose length is such that the end of the pipe does not reach the liquid surface is used for the measurement. The procedure for measuring the amount of carbon dioxide absorption using this carbon dioxide absorption test device (high pressure closed cell) is to open the valve 210 connected to the pressure resistant cell and leave it at normal pressure for an appropriate time before measuring the mass change. The procedure is the same as that of the carbon dioxide absorption device (normal pressure blowing type) except that

(3) Measurement of reaction heat of absorption liquid The amount of heat generated when the carbon dioxide absorption 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 measurement device shown in FIG. And the heat of reaction per mole of carbon dioxide was measured.
The reaction heat measuring device shown in FIG. 3 includes a carbon dioxide cylinder 301, a nitrogen cylinder 302, a cooling water circulating 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. , A temperature control jacket 311. The procedure for measuring the heat of reaction is described below.
1) In a glove box having a sufficiently low dew point, a predetermined amount (about 0.1 cc) of a sufficiently dried carbon dioxide absorbing liquid is charged in advance in a stainless steel container, and the charged amount (W _total ) is measured by an electronic balance. . Then, the stainless steel container is set in the calorimeter 308 held at 25 ° C. Further, the constant temperature water tank 306 is kept at 40 ° C. Nitrogen is caused to flow at 0.01 mL / min using the syringe pump 305, and the process waits until the change in heat quantity becomes 0.01 mW / h or less.
2) When the change in heat quantity becomes 0.01 mW / h or less, stop the syringe pump 305. Then, immediately, the syringe pump 304 is started, carbon dioxide is caused to flow into the stainless steel container set in the calorimeter 308, and the carbon dioxide absorption liquid absorbs carbon dioxide. An exothermic peak due to absorption of carbon dioxide is detected, and after a certain period of time, the change in the amount of heat becomes 0.01 mW / h or less again. 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 formula.
ΔH = Q / (W _total × (x ₁ / M _chem ) × α _CO2 ).
In the above formula, x ₁ is the mass fraction of the carbon dioxide chemical-absorbing amine in the carbon dioxide absorbing liquid, M _chem is the molar mass of the carbon dioxide chemical-absorbing amine, α _CO2 is the carbon dioxide absorption amount per 1 mol 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 for the case where the impurities were water vapor. Using the carbon dioxide absorption / emission test apparatus (temperature swing type) shown in FIG. 4, 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 After conducting the test, the temperature was raised to 120 ° C. and a carbon dioxide emission test was conducted. The carbon dioxide absorption / emission test device (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 tank 408, a controller 409, Stirrer 410, stirring blade 411, thermometer 412, cooling water circulation device 413, cooler 414, pressure gauge 415, carbon dioxide concentration meter 416, data logger 417, gas flow meter 418, recording PC 409, and A to I valves To be done.
The operation procedure of the carbon dioxide absorption and emission test is described below.
1) The reactor is set in an empty state, only nitrogen gas is flown from the nitrogen cylinder 402 at a predetermined flow rate by the mass flow controller 404, the system is replaced with nitrogen gas, and the reading of the carbon dioxide concentration meter 416 is 0.00. Make sure to show%.
2) Turn on the cooling water circulation device 413 to cool the cooler 414 to near 0 ° C.
3) With the nitrogen gas slowly flowing, 100 mL of the carbon dioxide absorption liquid is put into the reactor 407 from the absorption liquid 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 controller 409 controls the temperature of the constant temperature bath 408 so that the carbon dioxide absorption liquid becomes 50.0 ° C.
7) Open the carbon dioxide cylinder 401, and let the mass flow controller 403 flow carbon dioxide at a predetermined flow rate.
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 it is confirmed that the value is stable for 30 minutes or more.
10) Operate the valve E to switch the flow path to the reactor 407 side. The value of the carbon dioxide concentration meter 416 and the gas flow meter 418 is continuously recorded for 5 hours at intervals of 2 seconds, with the time for switching the valve E set to 0 minute.
11) After 5 hours, the temperature of the constant temperature bath 408 is controlled by the controller 409 so that the temperature of the absorbing liquid becomes 120 ° C.
12) With the time set at 120 ° C. set to 0 minute, the values of the carbon dioxide concentration meter 416 and the gas flow meter 418 are continuously recorded at 2 second intervals for 3 hours.
13) After a lapse of 3 hours, the gas flow path is switched from the reaction container side to the bypass side, the 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 conditions (0 ° C., 1 atm), respectively, and the amount of carbon dioxide at the absorbent outlet was determined. The carbon dioxide concentration and gas flow rate obtained in the flow path on the bypass side were converted into standard conditions (0 ° C., 1 atm), respectively, and the amount of carbon dioxide at the absorption liquid inlet was determined. The carbon dioxide absorption amount is calculated from the difference in the carbon dioxide amount between the absorption liquid inlet and the absorption liquid outlet.
15) Similarly, determine the amount of carbon dioxide at the absorbent outlet from the carbon dioxide concentration and the gas flow rate obtained at 120 ° C., and calculate the amount of carbon dioxide from the difference in the amount of carbon dioxide at the inlet of the absorbent obtained in the flow path on the bypass side. Calculate the amount of carbon emission.
16) In the case of entraining water vapor as an impurity in the mixed gas, the valves C and D were switched to the constant temperature humidifier 405 side, and the mixed gas was passed through the inside of the membrane tube controlled at 50 ° C. to be circulated outside 50. A mixed gas saturated with ion-exchanged water at 0 ° C. is prepared, and the mixed gas is sent to a reactor filled with a carbon dioxide absorbing solution, and the operation from 10) is performed.

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

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

  In addition, the heat of reaction of the carbon dioxide absorbent E1-7 was measured. The measurement result is shown in FIG.

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

  The heat of reaction was measured for the carbon dioxide absorbents E2-4, E2-6, E2-7, E2-10, E2-11, E2-14, E2-16. The measurement result is shown in FIG.

(Examples 3-1 to 3-3: MMEA / MDEA)
0.90 g of N-methylethanolamine (MMEA, Aldrich, 2- (methylamino) ethanol, purity ≧ 98.0%) as a carbon dioxide chemically absorbing amine, and methyldiethanolamine (MDEA as a tertiary amine solvent) , Manufactured by Aldrich Co., Ltd., purity ≧ 99.0%) was mixed with 5.61 g to obtain a carbon dioxide absorption liquid E3-1 (14% by mass). The water content is 2% or less. Similarly, a carbon dioxide absorption liquid E3-2 (30% by mass) and a carbon dioxide absorption liquid E3-3 (50% by mass) were obtained. The amount of carbon dioxide absorbed by the carbon dioxide absorbents E3-1, E3-2, E3-3 was measured at atmospheric pressure using the device shown in FIG. The results are shown in Fig. 11.

(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. (0.0%) 7.29 g was mixed to obtain a carbon dioxide absorption liquid E4-1 (20% by mass). The water content is 2% or less. Similarly, a carbon dioxide absorption liquid E4-2 (30 mass%) and a carbon dioxide absorption liquid E4-3 (50 mass%) were obtained. The carbon dioxide absorption amount of the carbon dioxide absorption liquids E4-1, E4-2, E4-3 was measured at atmospheric pressure using the device shown in FIG. The results are shown in Fig. 11.

(Examples 5-1 to 5-3: diethylenetriamine / MDEA)
1.61 g of diethylenetriamine (manufactured by Sigma-Aldrich, purity ≧ 99.0%) as a carbon dioxide chemical-absorbing amine and methyldiethanolamine (MDEA, manufactured by Aldrich, purity ≧ 99.0%) as a tertiary amine solvent 7 .42 g was mixed to obtain a carbon dioxide absorption liquid E5-1 (18% by mass). The water content is 2% or less. Similarly, a carbon dioxide absorption liquid E3-2 (30% by mass) and a carbon dioxide absorption liquid E3-3 (50% by mass) were obtained. The amount of carbon dioxide absorbed by the carbon dioxide absorbents E5-1, E5-2 and E5-3 was measured at atmospheric pressure using the device shown in FIG. 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 absorption liquid E5-1 (18% by mass). The water content is 2% or less. Similarly, a carbon dioxide absorption liquid E3-2 (30% by mass) and a carbon dioxide absorption liquid E3-3 (50% by mass) were obtained. The amount of carbon dioxide absorbed by the carbon dioxide absorbents E5-1, E5-2 and E5-3 was measured at atmospheric pressure using the device shown in FIG. The results are shown in FIGS. 12 and 13.

(Example 7)
45.0115 g of monoethanolamine (MEA, 2-aminoethanol, manufactured by Sigma-Aldrich, purity ≧ 99.0%) as a carbon dioxide chemically absorbing amine, and methyldiethanolamine (MDEA, manufactured by Aldrich) as a tertiary amine solvent , Purity ≧ 99.0%) 105.0151 g were mixed to obtain a carbon dioxide absorption liquid E7-1 (30% by mass). The water content is 1% or less. The carbon dioxide absorption / emission test was conducted under the dry condition using the simulated coal combustion exhaust gas (12 mol% CO ₂ —N ₂ ) using the carbon dioxide absorption liquid E7-1. The results are shown in FIGS. 14 and 15.

(Example 8)
36.4403 g of monoethanolamine (MEA, 2-aminoethanol, manufactured by Sigma-Aldrich, purity ≧ 99.0%) as a carbon dioxide chemically absorbing amine, and methyldiethanolamine (MDEA, manufactured by Aldrich) as a tertiary amine solvent , Purity ≧ 99.0%) were mixed to obtain carbon dioxide absorbent E8 (30% by mass). The water content is 1% or less. A carbon dioxide absorption / emission test of a simulated coal combustion exhaust gas (12 mol% CO ₂ —N ₂ ) was performed under humidified conditions using the carbon dioxide absorbent E8. The results are shown in FIGS. 14 and 15.

(Example 9)
Monoethanolamine (MEA, 2-aminoethanol, manufactured by Sigma-Aldrich Co., purity ≧ 99.0%) 40.0276 g as a carbon dioxide chemically absorbing amine, and N, N, N ′, N as a tertiary amine solvent A carbon dioxide absorbent E9 was obtained by mixing 93.3696 g of'-tetrakis (2-hydroxyethyl) ethylenediamine (manufactured by Sigma-Aldrich Co., purity 99.3%) (30% by mass). The water content is 1% or less. A carbon dioxide absorption / emission test of a simulated coal combustion exhaust gas (12 mol% CO ₂ —N ₂ ) was performed under humidified conditions using the carbon dioxide absorbent E9. The results are shown in FIGS. 14 and 15.

(Comparative Example 1: MEA / water)
0.67 g of ethanolamine (MEA, 2-aminoethanol, manufactured by Sigma-Aldrich Co., purity ≧ 99.0%) as a carbon dioxide chemically absorbing amine and 5.15 g of ultrapure water as a solvent are mixed to absorb carbon dioxide. Liquid R1 (molar fraction 20%) was obtained. The reaction heat of the carbon dioxide absorbent R1 was measured. The results are shown in Fig. 10.

  The present invention allows various embodiments and modifications without departing from the broad spirit and scope of the present invention. Further, the above-described embodiments are for explaining the present invention and do not limit the scope of the present invention. That is, the scope of the present invention is shown not by the embodiments but by the claims. Various modifications made within the scope of the claims and the scope of the invention equivalent thereto 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 Heat medium 108 Constant temperature bath 109 Platinum temperature detector 110 Resistance indicator 111 Cooling water circulation device 112 Reaction vessel 113 Rotor 114 Magnetic stirrer 115 stopper 116 gas introduction pipe 117 discharge pipe 201 vacuum pump 202 vacuum gauge 203 high pressure cell portion 204 gas chamber portion 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 Constant temperature water tank 307 Thermometer 308 Calorimeter 309 Control Personal computer 310 Pressure gauge 311 Temperature control jacket 401 Carbon dioxide cylinder 402 Nitrogen cylinders 403, 404 Mass flow controller 405 Constant temperature humidifier 406 Absorption liquid injector 407 Reactor 408 Constant temperature tank 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 Recording PC
A, B, C, D, E, F, G, I valves

Claims (14)

A carbon dioxide chemisorbable amine having a nitrogen-hydrogen bond, and a tertiary amine solvent having no nitrogen-hydrogen bond,
The carbon dioxide chemisorbable amine having a nitrogen-hydrogen bond is an amine represented by the formula 8 having an oxygen atom and / or a nitrogen atom via a hydrocarbon group having 2 or more carbon atoms in the main chain,
(In Formula 8, R ¹ is an unsubstituted or substituted hydrocarbon group or hydrogen, n5 is an integer of 2 or more. The carbon atom in the parentheses has a substituent. X represents —OR ⁵ , —N (R ⁶ ) R ^7, and is a nitrogen atom or an oxygen atom, and hydrogen bonded to them or an unsubstituted or substituted hydrocarbon group. (R ⁵ , R ⁶ , and R ⁷ are an unsubstituted or optionally substituted hydrocarbon group or hydrogen.)
The tertiary amine solvent having no nitrogen-hydrogen bond has a high hydrogen bond accepting property and is stable in a three-dimensional structure, so that the reaction between the carbon dioxide chemically absorbing amine having a nitrogen-hydrogen bond and carbon dioxide is performed. In order to promote, the main chain has 2 or more carbon atoms, has an oxygen atom and / or a nitrogen atom via a hydrocarbon group , which constitutes an acyclic skeleton, and the total number of oxygen atoms and nitrogen atoms is 2 or more. Ri Oh tertiary multidentate amines, which can be high temperature recovery, the carbon dioxide absorption liquid nonaqueous a moisture content of less than 10 wt%.   The amine represented by the above formula 8 having an oxygen atom and / or a nitrogen atom through a hydrocarbon group whose main chain has 2 or more carbon atoms is
  An amine represented by formula 9, in which one nitrogen atom is bound to two hydrogen atoms and one hydrocarbon group having a hydroxyl group,
(In formula 9, n6 is an integer of 2 or more. The carbon atom in the parenthesis may have a substituent.)
  An amine represented by the formula 10, in which one nitrogen atom, one hydrocarbon group having a hydroxyl group and one hydrocarbon group having no hydroxyl group are bonded to one nitrogen atom,
  (In Formula 10, R ⁷ Is a hydrocarbon group which may be unsubstituted or may have a substituent (excluding hydroxyl group), and n7 is an integer of 2 or more. The carbon atom in the parenthesis may have a substituent. )
  An amine represented by Formula 11, in which one hydrogen atom and two hydrocarbon groups having a hydroxyl group are bonded to one nitrogen atom, and
  (In formula 11, n8 and n9 are integers of 2 or more. The carbon atom in the parenthesis may have a substituent.)
  An amine represented by the formula 12 having a hydrogen atom and a nitrogen atom through a hydrocarbon group having a main chain of 2 or more carbon atoms in one nitrogen atom.
(In formula 12, R ⁸ , R ⁹ , R ¹⁰ Is a hydrocarbon group which may be unsubstituted or may have a substituent, and n10 is an integer of 2 or more. The carbon atom in the parenthesis may have a substituent. )
  The carbon dioxide absorbent according to claim 1, which is at least one selected from the group consisting of: The tertiary polydentate amine is
Tertiary amine in which one nitrogen atom has one hydrocarbon group having a hydroxyl group in the main chain of 2 or more carbon atoms and two unsubstituted hydrocarbon groups having 2 or more carbon atoms,
A tertiary amine in which one nitrogen atom has one hydrocarbon group having a hydroxyl group in the main chain of 3 or more carbon atoms and two unsubstituted hydrocarbon groups,
A tertiary amine or an acyclic skeleton in which one nitrogen atom has two hydrocarbon groups having two or more carbon atoms in the main chain having a hydroxyl group and one unsubstituted hydrocarbon group having three or more carbon atoms is bonded to one nitrogen atom. Tertiary amine having a diamine skeleton via a constituent ethylene group, propylene group, or butylene group,
The carbon dioxide absorbent according to claim 1 or 2 , which is 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 absorbent according to claim 3 , which is ethylenediamine. The carbon dioxide absorbent according to claim 4 , wherein the tertiary polydentate amine is N, N, N ', N'-tetrakis (2-hydroxyethyl) ethylenediamine. The carbon dioxide absorbent according to claim 1 or 2 , wherein the tertiary polydentate amine is N-methyldiethanolamine, N-ethyldiethanolamine, or triethanolamine. Before Ki窒 containing - carbon dioxide chemical absorption amine having a hydrogen bond includes a hydrocarbon group having a water group, the carbon dioxide absorbent solution according to any one of claims 1-6. Before Ki窒 containing - carbon dioxide chemical absorption amine having a hydrogen bond, 4-amino-1-butanol, N- methylethanolamine, 3-methylamino-1-propanol, 2- (ethylamino) ethanol, 2- The carbon dioxide absorbent according to claim 7 , which is (butylamino) ethanol, monoethanolamine, or diethanolamine. Before Ki窒 containing - carbon dioxide chemical absorption amines having hydrogen bonds are diethanolamine, carbon dioxide absorbing solution according to claim 8. Before Ki窒 containing - carbon dioxide chemical absorption amine having a hydrogen bond, carbon atoms in the main chain has a diamine skeleton having a nitrogen atom through a 2 or more hydrocarbon radicals, either of claims 1-6 1 The carbon dioxide absorbing liquid according to the item. Before Ki窒 containing - carbon dioxide chemical absorption amine having a hydrogen bond is a polyamine carbon atoms in the main chain has 2 or more diamines skeleton having a nitrogen atom through a 2 or more hydrocarbon groups, in claim 10 The carbon dioxide absorbent described. Before Ki窒 containing - carbon dioxide chemical absorbent amine having hydrogen bonding, ethylenediamine, N - hexyl ethylenediamine, N- (2- hydroxyethyl) ethylenediamine, N-(2-hydroxy isopropyl) ethylenediamine, N, N'-bis (2-hydroxyethyl) ethylenediamine, diethylenetriamine, tris (2-aminoethyl) amine, preparative triethylene tetramine, or 1,2-bis (3-aminopropionic pull amino) ethane, according to claim 10 or 11 dioxide Carbon absorption liquid.   The ratio of the carbon dioxide chemical-absorbing amine having the nitrogen-hydrogen bond and the tertiary amine solvent not having the nitrogen-hydrogen bond in the carbon dioxide-absorbing liquid is determined by the carbon dioxide chemical-absorbing property having the nitrogen-hydrogen bond. The ratio of amine / (carbon dioxide chemically absorbing amine having nitrogen-hydrogen bond + tertiary amine solvent not having nitrogen-hydrogen bond) (mass ratio) is 1/100 to 50/100. 12. The carbon dioxide absorbent according to any one of 12. The carbon dioxide absorption 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 less to cause the carbon dioxide absorption liquid to absorb the carbon dioxide, and thereby the mixed gas. From the absorption step of selectively separating carbon dioxide from the carbon dioxide, and by heating the carbon dioxide absorption liquid that has absorbed the carbon dioxide to 120 ° C. or higher to diffuse and recover 90% or more of the absorbed carbon dioxide, A method for separating and recovering carbon dioxide, which comprises a heating regeneration step of regenerating the carbon absorption liquid.