WO2018043630A1

WO2018043630A1 - Carbon dioxide absorbent, and method and apparatus for separating and recovering carbon dioxide with use of said absorbent

Info

Publication number: WO2018043630A1
Application number: PCT/JP2017/031316
Authority: WO
Inventors: 三豪末松; 上等　和良; 与一高野
Original assignee: 三菱瓦斯化学株式会社
Priority date: 2016-09-02
Filing date: 2017-08-31
Publication date: 2018-03-08
Also published as: JP6940824B2; JPWO2018043630A1

Abstract

A carbon dioxide absorbent which contains an alkylidene aminoguanidine represented by general formula (1). (In the formula, each of R¹ and R² independently represents a hydrogen atom or an optionally substituted hydrocarbon group having 1-18 carbon atoms.)

Description

Carbon dioxide absorbent, carbon dioxide separation / recovery method and separation / recovery apparatus using the absorbent

The present invention relates to a carbon dioxide absorbent, a carbon dioxide separation and recovery method using the absorbent, and a separation and recovery apparatus.

In recent years, carbon dioxide in the atmosphere has attracted attention as a causative agent of global warming, and separates and recovers carbon dioxide in exhaust gas discharged from large-scale sources such as thermal power plants, steelworks, cement factories, etc. Consideration has been made.

Conventionally, carbon dioxide contained in gas has been separated by various methods. For example, a method of absorbing and removing carbon dioxide by bringing it into contact with a basic absorbent is generally performed, such as removal of carbon dioxide in an ammonia production process. Such a method is classified as a chemical absorption method, and carbon dioxide chemically absorbed in the absorption tower is released from the absorbent and recovered by heating the absorbent in the regeneration tower. The chemical absorption process is characterized by high-efficiency removal of carbon dioxide and high-purity carbon dioxide recovery.

When separating and recovering carbon dioxide from exhaust gas, if the conventional separation and recovery technology represented by the chemical absorption method is used, the specific gravity of the additional energy required for the separation becomes large, so the economy is very large. It becomes. In the case of the chemical absorption method, the energy required for this separation is the largest in the process of heating the absorbent that has absorbed carbon dioxide and releasing the carbon dioxide. Conventional basic absorbents used in chemical absorption methods include potassium carbonate aqueous solution and alkanolamine aqueous solution typified by monoethanolamine aqueous solution. These are used as basic technologies for absorption with smaller separation energy. Drugs are being studied.

Patent Document 1 and Patent Document 2 propose a method of removing carbon dioxide from combustion exhaust gas using a specific monoamine aqueous solution. In Patent Document 3 and Patent Document 4, a method for removing carbon dioxide from combustion exhaust gas using a specific aqueous diamine solution is proposed. Although these methods are improved over the method using a monoethanolamine aqueous solution, further energy saving and higher efficiency are desired.

Japanese Patent No. 2871334 Japanese Patent No. 2895325 JP-A-7-313840 Special table 2010-514549 gazette

As described above, one problem with the conventional carbon dioxide absorbent is further energy saving during the separation and recovery of carbon dioxide. Further, in the conventional absorbent, there is a problem that a small amount of amine compound volatilizes and loses when contacting with gas in the process of absorbing carbon dioxide, so the volatility of the amine compound contained in the carbon dioxide absorbent One of the challenges is to lower

In the conventional chemical absorption method, steam heating is performed to a temperature of about 110 ° C. to 130 ° C., and the absorbent is boiled for regeneration. Therefore, this method requires very large heat energy. Furthermore, since there is a concern that the amine compound contained in the carbon dioxide absorbent is thermally decomposed in this regeneration step, the thermal stability of the carbon dioxide absorbent is also a problem.

The present invention has been made in view of the above problems, and uses a carbon dioxide absorbent having high carbon dioxide absorption and release performance, low volatility, and excellent thermal stability, and the carbon dioxide absorbent. An object is to provide a carbon dioxide separation and recovery method and a carbon dioxide separation and recovery device.

As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be solved by using a specific alkylideneaminoguanidine, and have completed the present invention.

That is, the present invention is as follows.
[1]
Containing an alkylideneaminoguanidine represented by the following general formula (1),
Carbon dioxide absorbent.

(In the formula, R ¹ and R ² are each independently a hydrogen atom or a hydrocarbon group having 1 to 18 carbon atoms which may have a substituent.)
[2]
Further containing a solvent,
The carbon dioxide absorbent according to [1].
[3]
The solvent contains at least one selected from the group consisting of water, glycol solvents, alcohol solvents, and aprotic polar solvents,
[2] The carbon dioxide absorbent according to [2].
[4]
The glycol solvent contains at least one selected from the group consisting of ethylene glycol, propylene glycol, and diethylene glycol,
The carbon dioxide absorbent according to [3].
[5]
The alkylidene aminoguanidine includes a compound represented by the following formula (2):
The carbon dioxide absorbent according to any one of [1] to [4].

[6]
The alkylidene aminoguanidine content is 5.0% by mass or more and 80.0% by mass or less based on the total amount of the carbon dioxide absorbent.
The carbon dioxide absorbent according to any one of [1] to [5].
[7]
The total content of the solvent is 1.0% by mass or more and 95.0% by mass or less with respect to the total amount of the carbon dioxide absorbent.
[2] to [6] The carbon dioxide absorbent according to any one of [6].
[8]
A contact step of causing the carbon dioxide absorbent to absorb the carbon dioxide by contacting the carbon dioxide absorbent according to any one of [1] to [7] and a gas containing carbon dioxide;
Desorbing the carbon dioxide from the carbon dioxide absorbent by heating the carbon dioxide absorbent that has absorbed the carbon dioxide.
Carbon dioxide separation and recovery method.
[9]
The temperature in the contact step is 0 ° C. or more and less than 60 ° C.,
[8] The method for separating and recovering carbon dioxide according to [8].
[10]
The temperature in the desorption step is 60 ° C. or higher and 120 ° C. or lower.
The carbon dioxide separation and recovery method according to [8] or [9].
[11]
The carbon dioxide absorbent according to any one of [1] to [7] is provided, and a gas containing carbon dioxide is brought into contact with the carbon dioxide absorbent so that the carbon dioxide is introduced into the carbon dioxide absorbent. An absorbing device to absorb,
A desorption device that desorbs the carbon dioxide from the carbon dioxide absorbent by heating the carbon dioxide absorbent that has absorbed the carbon dioxide in the absorber.
Carbon dioxide separation and recovery device.
[12]
Having a recovery device for recovering the desorbed carbon dioxide;
[11] The carbon dioxide separation and recovery device according to [11].

According to the present invention, a carbon oxide absorbent having high carbon dioxide absorption / release performance, low volatility, and excellent thermal stability, a method for separating and recovering carbon dioxide using the carbon dioxide absorbent, and carbon dioxide A separation and recovery device can be provided.

Schematic diagram showing the carbon dioxide separation and recovery device of the present embodiment Schematic diagram of the equipment used for evaluating carbon dioxide absorption and recovery in the examples

Hereinafter, embodiments of the present invention (hereinafter referred to as “present embodiments”) will be described in detail. However, the present invention is not limited to these embodiments, and various modifications can be made without departing from the scope of the present invention. is there.

[CO2 absorbent]
The carbon dioxide absorbent of the present embodiment contains an alkylideneaminoguanidine represented by the following general formula (1).

(In the formula, R ¹ and R ² are each independently a hydrogen atom or a hydrocarbon group having 1 to 18 carbon atoms which may have a substituent.)

As represented by the above formula (1), by having both an aminoguanidine moiety and an alkylidene moiety, a high carbon dioxide absorption / release performance is exhibited, and the volatility is low and the thermal stability is also excellent. Become.

In particular, with regard to high carbon dioxide absorption performance, aminoguanidine having no alkylidene moiety is known to easily react with carbon dioxide to give aminoguanidine bicarbonate. Even in alkylideneaminoguanidine having the above structure, aminoguanidine moiety Is considered to be involved in the high reactivity with carbon dioxide, and it is considered that the aminoguanidine site easily reacts with carbon dioxide to form an aminoguanidine bicarbonate structure.

With respect to high carbon dioxide release performance, aminoguanidine bicarbonate releases carbon dioxide at around 120 ° C, while surprisingly alkylidene aminoguanidines with alkylidene moieties release carbon dioxide at lower temperatures than aminoguanidine bicarbonate. This has been clarified by the study of the present inventors.

Furthermore, when aminoguanidine bicarbonate is heated to 120 ° C., the pyrolysis reaction proceeds simultaneously with the release of carbon dioxide, but the alkylidene aminoguanidine having the above structure does not thermally decompose at 120 ° C., and the alkylidene site is the molecular heat. It is assumed that it contributes to the improvement of stability. In addition, alkylideneaminoguanidine having the above structure has low volatility when heated, and it is speculated that the alkylidene moiety is also involved in the effect of suppressing volatility in this respect.

As described above, the carbon dioxide absorbent of this embodiment containing an alkylideneaminoguanidine represented by the following general formula (1) exhibits high carbon dioxide absorption / release performance, has low volatility, and It is also excellent in stability. Therefore, by using the carbon dioxide absorbent of the present embodiment, it becomes possible to separate and collect carbon dioxide stably and continuously with energy saving, and to achieve a continuous and efficient carbon dioxide separation and recovery method. Is possible.

In the present embodiment, the “carbon dioxide absorbent” is capable of absorbing carbon dioxide under a specific condition, and particularly capable of desorbing carbon dioxide under another condition. is there. In addition, the carbon dioxide absorbent of the present embodiment may absorb other acidic gases in addition to carbon dioxide.

(Alkylidene aminoguanidine)
In the present embodiment, alkylideneaminoguanidine represented by the general formula (1) is used. In general formula (1), the hydrocarbon group having 1 to 18 carbon atoms represented by R ¹ and R ² is not particularly limited, and examples thereof include an alkyl group, a cycloalkyl group, an alkenyl group, an alkylene group, and an aryl group. And a group in which an alkyl group and an aryl group are bonded, and a group in which an alkylene group and an aryl group are bonded. Among these, an aryl group, a group in which an alkyl group and an aryl group are bonded, a group in which an alkylene group and an aryl group are bonded are preferable, and a group in which an alkylene group and an aryl group are bonded is more preferable.

The alkyl group is not particularly limited, but for example, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, t-butyl group, n-pentyl group, neopentyl group Group, n-hexyl group, texyl group, n-heptyl group, n-octyl group, n-ethylhexyl group, n-nonyl group, n-decyl group and the like.

The cycloalkyl group is not particularly limited, and examples thereof include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cyclooctyl group, a cyclodecyl group, a cyclododecyl group, a cyclohexadecyl group, and a cyclooctadecyl group.

The alkenyl group is not particularly limited, and examples thereof include a vinyl group, propynyl group, butynyl group, pentynyl group, hexynyl group, octynyl group, decynyl group, dodecynyl group, hexadecynyl group, and octadecynyl group.

The alkylene group is not particularly limited, and examples thereof include a methylene group, an ethylene group, and a propylene group.

The aryl group is not particularly limited, and examples thereof include a phenyl group and a naphthyl group.

The number of carbon atoms of the hydrocarbon group is 1 to 18, preferably 2 to 16, more preferably 4 to 14, and further preferably 6 to 12.

Although it does not specifically limit as a substituent which substitutes the hydrogen atom of a hydrocarbon group, For example, the group containing a sulfur atom, the group containing a nitrogen atom, or the group containing an oxygen atom is mentioned.

The alkylideneaminoguanidine represented by the general formula (1) is not particularly limited, and examples thereof include 1-methylethylideneaminoguanidine, 1-methylpropylideneaminoguanidine, 1-methylbutylideneaminoguanidine, 1,3- Dimethylbutylideneaminoguanidine, 1,2-dimethylpropylideneaminoguanidine, 1-methylpentylideneaminoguanidine, 2,6-dimethyl-4-heptylideneaminoguanidine, 2-furylmethylideneaminoguanidine, benzylideneaminoguanidine, 4-dimethylaminophenylmethyleneaminoguanidine, 4-methoxyphenylmethyleneaminoguanidine, 4-hydroxyphenylmethyleneaminoguanidine, 1-phenylethylideneaminoguanidine, 1-methyl-3-phenyl Ruarylideneaminoguanidine, diphenylmethyleneaminoguanidine, 1- (2,4-dihydroxyphenyl) benzylideneaminoguanidine, 2-methylarylideneaminoguanidine, 2-butene-1-ylideneaminoguanidine, 1-methylhexylidene Aminoguanidine, 3-phenylarylideneaminoguanidine, 2-methylpropylideneaminoguanidine and the like can be mentioned.

Among these, the alkylideneaminoguanidine preferably includes an arylideneaminoguanidine represented by the following formula (1a), more preferably includes a phenylarylideneaminoguanidine represented by the following formula (1b), It preferably contains 3-phenylallylideneaminoguanidine represented by the formula (2). By using such alkylideneaminoguanidine, volatility is lowered and carbon dioxide absorption / release performance and thermal stability tend to be further improved.

R ³ is a hydrogen atom or an optionally substituted hydrocarbon group having 1 to 16 carbon atoms, preferably an alkyl group, a cycloalkyl group, an alkenyl group, an alkylene group, an aryl group, an alkyl group and an aryl group. A group bonded to a group, a group bonded to an alkylene group and an aryl group, more preferably an aryl group, a group bonded to an alkyl group and an aryl group, a group bonded to an alkylene group and an aryl group, More preferably, it is a group in which an alkylene group and an aryl group are bonded.

R ⁴ is a hydrogen atom or an optionally substituted hydrocarbon group having 1 to 10 carbon atoms, preferably an alkyl group, a cycloalkyl group, an alkenyl group, or an alkylene group. Further, n is 0 to 5, preferably 0 to 3, and more preferably 0 to 1.

The alkylidene aminoguanidine represented by the above formula (1) is obtained by mixing an aminoguanidine salt as a raw material and a carbonyl compound such as acetone or methyl isobutyl ketone forming an alkylidene skeleton in an alcohol solvent such as water or methanol. If necessary, it can be synthesized by adding an acid such as hydrochloric acid, sulfuric acid, nitric acid, carbonic acid and reacting.

The content of alkylideneaminoguanidine is preferably 1.0% by mass or more, more preferably 5.0% by mass or more, and further preferably 10.0% by mass or more with respect to the total amount of carbon dioxide absorbent. . The content of alkylideneaminoguanidine is preferably 100.0% by mass or less, more preferably 80.0% by mass or less, and further preferably 70.0% by mass or less, based on the total amount of carbon dioxide absorbent. More preferably, it is 65.0 mass% or less, More preferably, it is 50.0 mass% or less. When the content of the alkylideneaminoguanidine is 1.0% by mass or more, the effect of the alkylideneaminoguanidine in the carbon dioxide absorbent tends to be more effectively exhibited. Further, when the content of alkylideneaminoguanidine is 100.0% by mass or less, particularly 80.0% by mass or less, an appropriate amount of water molecules is hydrated with respect to alkylideneaminoguanidine that contributes to the carbon dioxide absorption reaction. The reactivity between carbon dioxide and alkylideneaminoguanidine tends to be further improved, and the carbon dioxide absorption / release performance tends to be further improved.

(solvent)
The carbon dioxide absorbent of the present embodiment preferably further contains a solvent. The solvent can be appropriately selected according to the solubility or dispersibility of the alkylideneaminoguanidine, but from the viewpoint of being less volatile in the desorption step, a solvent having a low vapor pressure and a high boiling point is preferred, and alkylideneaminoguanidine and carbon dioxide. From the viewpoint that it is difficult to prevent this reaction, a solvent that is not reactive with alkylideneaminoguanidine is preferable, and from the viewpoint of energy saving, a solvent having low specific heat and good thermal conductivity is preferable.

Examples of such a solvent include, but are not limited to, water; glycol solvents such as ethylene glycol, propylene glycol, diethylene glycol, 1,3-butanediol, and 1,4-butanediol; ethanol, methanol, butanol, Alcohol solvents such as pentanol and cyclohexanol; polyhydric alcohol solvents having three or more hydroxyl groups such as glycerin; aprotic polar solvents such as dimethyl sulfoxide; 2-pyrrolidone, N-methylpyrrolidone, dimethyl Examples thereof include at least one selected from the group consisting of amide solvents such as acetamide; carbonate solvents such as ethylene carbonate, propylene carbonate, and diethyl carbonate; or silicon oil. Among these, water, glycol solvents, alcohol solvents, and aprotic polar solvents are preferable, water, ethylene glycol, propylene glycol, diethylene glycol, methanol, and ethanol are more preferable, and water and ethylene glycol are more preferable. By using such a solvent, the reactivity of the alkylideneaminoguanidine and carbon dioxide tends to be further improved from the solvation of the solvent molecules and the carbon dioxide solubility of the solvent. Further, the viscosity of the solvent is low, and the carbon dioxide absorption / release performance tends to be further improved. Furthermore, the viscosity can be further reduced by using water or ethylene glycol. A solvent may be used individually by 1 type, or may use 2 or more types together.

Among the above solvents, the carbon dioxide absorbent of the present embodiment preferably further contains water. By containing water, water molecules are hydrated with respect to alkylideneaminoguanidine that contributes to carbon dioxide absorption reaction, the reactivity between carbon dioxide and alkylideneaminoguanidine is further improved, and carbon dioxide absorption and release performance is further improved. It tends to improve.

The water content is preferably 1.0% by mass or more, more preferably 5.0% by mass or more, and further preferably 10.0% by mass or more with respect to the total amount of the carbon dioxide absorbent. . The water content is preferably 99.0% by mass or less, more preferably 95.0% by mass or less, and still more preferably 90.0% by mass or less, based on the total amount of the carbon dioxide absorbent. It is. When the water content is 1.0% by mass or more, an appropriate amount of water molecules are hydrated with respect to the alkylideneaminoguanidine that contributes to the carbon dioxide absorption reaction, and the reactivity between carbon dioxide and alkylideneaminoguanidine is increased. The carbon dioxide absorption and release performance tends to be further improved. Moreover, when the water content is 99.0% by mass or less, the effect of the alkylideneaminoguanidine in the carbon dioxide absorbent tends to be more effectively exhibited. Note that the optimum value of the water content may vary depending on the alkylideneaminoguanidine used.

The content of the glycol solvent is preferably 1.0% by mass or more, more preferably 5.0% by mass or more, and further preferably 10.0% by mass or more with respect to the total amount of the carbon dioxide absorbent. It is. Further, the content of the glycol solvent is preferably 99.0% by mass or less, more preferably 95.0% by mass or less, and further preferably 90.0% by mass with respect to the total amount of the carbon dioxide absorbent. % Or less. When the glycol solvent content is 1.0% by mass or more, an appropriate amount of solvent molecules are solvated with respect to the alkylideneaminoguanidine that contributes to the carbon dioxide absorption reaction, and the reaction between carbon dioxide and alkylideneaminoguanidine. Tend to be improved, and the carbon dioxide absorption and release performance tends to be further improved. Moreover, when the content of the glycol solvent is 99.0% by mass or less, the effect of the alkylideneaminoguanidine in the carbon dioxide absorbent tends to be more effectively exhibited. Note that the optimum value of the content of the glycol solvent may vary depending on the alkylideneaminoguanidine used.

Further, the content of the solvent other than water and the glycol solvent is preferably 1.0% by mass or more, more preferably 5.0% by mass or more, and still more preferably based on the total amount of the carbon dioxide absorbent. Is 10.0% by mass or more. Further, the content of the solvent other than water and the glycol solvent is preferably 99.0% by mass or less, more preferably 95.0% by mass or less, and still more preferably based on the total amount of the carbon dioxide absorbent. Is 90.0 mass% or less. When the content of the solvent other than water and glycol solvent is 1.0% by mass or more, an appropriate amount of solvent molecules are solvated with respect to the alkylideneaminoguanidine contributing to the carbon dioxide absorption reaction, and carbon dioxide and alkylidene. The reactivity with aminoguanidine tends to be further improved, and the carbon dioxide absorption / release performance tends to be further improved. Moreover, it exists in the tendency for the effect of the alkylidene amino guanidine in a carbon dioxide absorbent to exhibit more effectively because content of solvents other than water and a glycol type solvent is 99.0 mass% or less.

The total content of the solvent is preferably 1.0% by mass or more, more preferably 5.0% by mass or more, and further preferably 10.0% by mass or more with respect to the total amount of the carbon dioxide absorbent. is there. The total content of the solvent is preferably 99.0% by mass or less, more preferably 95.0% by mass or less, and further preferably 90.0% by mass with respect to the total amount of the carbon dioxide absorbent. It is as follows. When the total content of the solvent is 1.0% by mass or more, an appropriate amount of solvent molecules is solvated with respect to the alkylideneaminoguanidine that contributes to the carbon dioxide absorption reaction, and the reactivity between carbon dioxide and alkylideneaminoguanidine. However, the carbon dioxide absorption and release performance tends to be further improved. Moreover, when the total content of the solvent is 99.0% by mass or less, the effect of the alkylideneaminoguanidine in the carbon dioxide absorbent tends to be more effectively exhibited.

(Other amine compounds)
The carbon dioxide absorbent of the present embodiment may contain other amine compounds other than alkylideneaminoguanidine as necessary. By containing other amine compounds, the performance of the carbon dioxide absorbent such as the amount of carbon dioxide absorbed and released can be supplementarily improved.

The other amine compound is not particularly limited as long as it does not interfere with the reaction between alkylideneaminoguanidine and carbon dioxide, but preferably has a low vapor pressure or a high boiling point, and more preferably has a low reaction heat with carbon dioxide. .

Examples of such other amine compounds include, but are not limited to, monoethanolamine, 1-amino-2-propanol, 1-amino-2-butanol, 2-amino-1-propanol, 2-amino-1 -Butanol, 2-amino-2-methyl-1-propanol, 2-amino-1,3-propanediol, 3-amino-1-propanol, 3-amino-1,2-propanediol, aniline, cyclohexylamine, etc. Primary amines: 2-methylaminoethanol, 2-ethylaminoethanol, 2-isopropylaminoethanol, 2-propylaminoethanol, diethanolamine, diisopropanolamine, 2-t-butylaminoethanol, 2-n-butyl Secondary amines such as aminoethanol and piperidine; 2- Methylaminoethanol, 2-diethylaminoethanol, 1-dimethylamino-2-propanol, N-ethyl-N-methylethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, triethanolamine, N, N-dimethylaniline, pyridine Tertiary amines such as 1-hydroxyethylpiperidine; 1,3-diaminopropan-2-ol, ethylenediamine, N- (2-hydroxyethyl) -1,2-ethylenediamine, N- (2-hydroxypropyl) -1,2-ethylenediamine, N, N′-bis (2-hydroxyethyl) -1,2-ethylenediamine, N, N, N′-tris (2-hydroxyethyl) -1,2-ethylenediamine, N, N , N'-Tris (2-hydroxypropyl) -1,2-ethyl Diamine, N, N, N ′, N′-tetrakis (2-hydroxyethyl) -1,2-ethylenediamine, N, N, N ′, N′-tetrakis (2-hydroxypropyl) -1,2-ethylenediamine, Hexamethylenediamine, N- (2-hydroxyethyl) -1,6-hexamethylenediamine, N- (2-hydroxypropyl) -1,6-hexamethylenediamine, N, N′-bis (2-hydroxyethyl) -1,6-hexamethylenediamine, N, N, N′-tris (2-hydroxyethyl) -1,6-hexamethylenediamine, N, N, N′-tris (2-hydroxypropyl) -1,6 -Hexamethylenediamine, N, N, N ', N'-tetrakis (2-hydroxyethyl) -1,6-hexamethylenediamine, N, N, N', N'-tetrakis (2 Diamines such as hydroxypropyl) -1,6-hexamethylenediamine; piperazines such as piperazine, 2-methylpiperazine, 2,5-dimethylpiperazine, 1-hydroxyethylpiperazine; diethylenetriamine, tetraethylenepentamine, polyethyleneimine, Examples include polyvinylamine and polyallylamine.

(Other ingredients)
The carbon dioxide absorbent of this embodiment further includes other components such as an acid component, an alkali component, a salt, an antifoaming agent, a dispersion stabilizer, a surfactant, a viscosity modifier, and a corrosion inhibitor as necessary. You may contain.

The above-mentioned acid component, alkali component, or salt can be added for the purpose of adjusting the performance of desorbing carbon dioxide from alkylideneaminoguanidine.

The antifoaming agent, dispersion stabilizer, surfactant, viscosity modifier, corrosion inhibitor and the like can be appropriately selected and added according to the form of the carbon dioxide absorbent. Although it does not specifically limit as a form of the carbon dioxide absorbent of this embodiment, For example, liquids, such as a uniform solution, a dispersion liquid, or an emulsion; Various forms, such as solids, such as powder, a swelling gel form, or a molded object, are included. It is possible to take. It is also possible to use it while supporting it on a porous support.

[Method for separating and recovering carbon dioxide]
The method for separating and recovering carbon dioxide according to the present embodiment comprises a contact step of causing the carbon dioxide absorbent to absorb carbon dioxide by bringing the carbon dioxide absorbent into contact with a gas containing carbon dioxide, and absorbing carbon dioxide. A desorption step of desorbing carbon dioxide from the carbon dioxide absorbent by heating the carbon dioxide absorbent. In FIG. 1, the schematic diagram which shows an example of the carbon dioxide separation-and-recovery apparatus of this embodiment is shown.

(Contact process)
The contact step is a step of causing the carbon dioxide absorbent to absorb carbon dioxide by bringing the carbon dioxide absorbent into contact with a gas containing carbon dioxide. The contact method can be selected according to the form of the carbon dioxide absorbent, and is not particularly limited. For example, when the carbon dioxide absorbent is a liquid, the carbon dioxide absorbent and the carbon dioxide are mixed by blowing a gas containing carbon dioxide into the solution or by gas-liquid mixing the solution and the gas containing carbon dioxide. The containing gas can be contacted. When the carbon dioxide absorbent is solid, the gas containing carbon dioxide is passed through the solid, the solid is dispersed in the gas containing carbon dioxide, or the solid is placed in the gas containing carbon dioxide. Thus, the carbon dioxide absorbent and the gas containing carbon dioxide can be brought into contact with each other.

The temperature in the contacting step is preferably 0 ° C. or higher and lower than 60 ° C., more preferably 20 ° C. or higher and lower than 60 ° C., and further preferably 40 ° C. or higher and lower than 60 ° C. When the temperature in the contact step is within the above range, the carbon dioxide absorbent tends to absorb carbon dioxide more efficiently.

(Gas containing carbon dioxide)
The gas containing carbon dioxide is not particularly limited, and examples thereof include thermal power plant exhaust gas, steel plant exhaust gas, cement factory exhaust gas, chemical plant exhaust gas, biofermentation gas, and natural gas. These gases are particularly required to separate carbon dioxide with energy saving, and the present invention is particularly effective. In addition, the density | concentration of the carbon dioxide in gas, the pressure of gas, and the temperature of gas are not restrict | limited in particular, This embodiment can be applied in the gas of a wide range of conditions. Moreover, the gas containing carbon dioxide may contain an acidic gas other than carbon dioxide. In the case where the exhaust gas or the like contains an acid gas other than carbon dioxide, it is preferable to combine known processes for removing other acid gases. Specifically, from a mode in which the carbon dioxide separation and recovery method of the present embodiment is applied to a gas containing an acidic gas other than carbon dioxide, or a gas containing an acidic gas other than carbon dioxide or the like, known means Then, after removing other acidic gas, an embodiment in which the method for separating and recovering carbon dioxide of the present embodiment is applied.

[Desorption step]
The desorption step is a step of desorbing carbon dioxide from the carbon dioxide absorbent by heating the carbon dioxide absorbent that has absorbed carbon dioxide. The heating temperature in this desorption step is preferably 60 ° C. or higher and 120 ° C. or lower, more preferably 65 ° C. or higher and 110 ° C. or lower, and further preferably 70 ° C. or higher and 100 ° C. or lower. When the temperature in the desorption step is within the above range, carbon dioxide tends to be more efficiently desorbed from the carbon dioxide absorbent.

[CO2 separation and recovery equipment]
The carbon dioxide separation and recovery device of the present embodiment includes the carbon dioxide absorbent, and makes the carbon dioxide absorbent absorb the carbon dioxide by bringing a gas containing carbon dioxide into contact with the carbon dioxide absorbent. And a desorption device for desorbing the carbon dioxide from the carbon dioxide absorbent by heating the carbon dioxide absorbent that has absorbed the carbon dioxide in the absorption device.

(Absorber)
The absorption device includes the carbon dioxide absorbent, and makes the carbon dioxide absorbent absorb carbon dioxide by bringing a gas containing carbon dioxide into contact with the carbon dioxide absorbent. The absorption device is not particularly limited as long as it has a configuration in which a gas containing carbon dioxide and a carbon dioxide absorbent are brought into contact with each other according to the form of the carbon dioxide absorbent.

For example, the absorption device can include an absorbent holding unit that holds a carbon dioxide absorbent and a gas supply unit that supplies a gas containing carbon dioxide to the absorbent holding unit. Also, from the viewpoint of discharging the carbon dioxide absorbent that has absorbed carbon dioxide from the absorbent holding section and supplying a new carbon dioxide absorbent, the absorption device discharges the carbon dioxide absorbent held in the absorbent holding section. And an absorbent supply section for supplying a new carbon dioxide absorbent to the absorbent holding section. In addition, as a contact method, what was mentioned above is mentioned.

Furthermore, in order to adjust the temperature at which the gas containing carbon dioxide and the carbon dioxide absorbent are brought into contact with each other, the absorption device may have a heating / cooling mechanism, and the carbon dioxide concentration can be measured so that the carbon dioxide concentration can be measured. It may have a carbon concentration measurement mechanism. Furthermore, in order to adjust the pressure when the gas containing carbon dioxide and the carbon dioxide absorbent are brought into contact with each other, the absorption device may have a pressurization / decompression mechanism.

(Desorption device)
The desorption device desorbs carbon dioxide from the carbon dioxide absorbent by heating the carbon dioxide absorbent that has absorbed carbon dioxide in the absorption device. The desorption device is not particularly limited as long as it has a configuration for desorbing carbon dioxide from the carbon dioxide absorbent according to the form of the carbon dioxide absorbent.

For example, the desorption device can include an absorbent holding unit that holds a carbon dioxide absorbent, and a gas discharge unit that discharges carbon dioxide released from the absorbent holding unit. The means for supplying the carbon dioxide absorbent that has absorbed carbon dioxide from the absorption device to the desorption device is not particularly limited, and the absorption device that has been operated for a certain period of time is temporarily stopped to remove the carbon dioxide absorbent in the absorption device. The carbon dioxide absorbent may be supplied collectively to the separation apparatus, or may be continuously or intermittently supplied from the absorbent holding section to the desorption apparatus using the absorbent discharge section.

Furthermore, in order to adjust the temperature at which carbon dioxide is desorbed from the carbon dioxide absorbent, the desorption device may have a heating / cooling mechanism, or the carbon dioxide concentration measurement so that the carbon dioxide concentration can be measured. You may have a mechanism. Furthermore, in order to adjust the pressure when the gas containing carbon dioxide and the carbon dioxide absorbent are brought into contact with each other, the desorption device may have a pressurization / decompression mechanism.

The carbon dioxide absorbent after desorbing carbon dioxide by the desorption device (also referred to as “regeneration tower” or “regeneration device”) can be used again (reused) in the absorption device.

(Recovery device)
The carbon dioxide separation and recovery device of this embodiment may have a recovery device for recovering the desorbed carbon dioxide. The recovered carbon dioxide is used for agricultural applications such as enhanced oil recovery and plant factories; industrial gas applications such as beverages and welding; chemical synthesis applications; and carbon dioxide storage (CCS) applications. Can do. Moreover, you may concentrate the carbon dioxide collect | recovered before using for these uses.

Hereinafter, the present invention will be described in more detail using examples and comparative examples. In addition, this invention is not limited at all by the following examples.

(Synthesis Example 1) Synthesis of 3-phenylarylideneaminoguanidine (2) To a 50 mL eggplant-shaped flask was added 1.332 g (12.0 mmol) of aminoguanidine hydrochloride, 6 mL of methanol, and 0.25 mL of 12N hydrochloric acid at room temperature. Stir for 10 minutes. Thereafter, 1.609 g (12.2 mmol) of cinnamaldehyde was added, and the mixture was stirred at room temperature using a magnetic stirring bar. After stirring for 2 hours, the resulting reaction solution was added dropwise to 20 mL of a saturated aqueous sodium hydrogen carbonate solution to precipitate pale yellow crystals. This was collected by filtration, washed with water, and then vacuum-dried at 50 ° C. for 24 hours to obtain 2.213 g (11.8 mmol) of a pale yellow solid. The molar yield based on aminoguanidine hydrochloride was 98%.

The obtained solid was analyzed by 1H-NMR and confirmed to be 3-phenylarylideneaminoguanidine represented by the following formula (2).
1H-NMR measurement conditions:
(DMSO-d6, 500 MHz, δ; ppm) = 5.5 (s; 2H), 5.7-5.8 (br; 2H), 6.7 (d; 1H), 6.9 (dd; 1H) ), 7.2 (dd; 1H), 7.3 (dd; 2H), 7.5 (d; 2H), 7.8 (d; 1H))

Further, when the melting point of the obtained 3-phenylarylideneaminoguanidine was measured using a trace melting point measuring device BY-1 (manufactured by Yazawa Kagaku Co., Ltd.), it was 190 to 192 ° C.

Furthermore, elemental analysis was performed using a simultaneous carbon, hydrogen, and nitrogen quantitative determination apparatus CHN Coder MT-6 (Yanaco Analytical Industrial Co., Ltd.), and the following results were obtained.
Calculated C, 63.81; H, 6.43; N, 29.77
Found C, 63.26; H, 6.45; N, 29.43

(Synthesis Example 2) Synthesis of 3-phenylarylideneaminoguanidine bicarbonate 9.50 g (10% by mass) of 3-phenylarylideneaminoguanidine obtained in Synthesis Example 1 above and 85.5 g (90% by mass) of water Were mixed to prepare 95 g of a slurry carbon dioxide absorbent. This carbon dioxide absorbent is filled in a 200 mL flask, heated to 25 ° C. with an aluminum block, and stirred with a magnetic stirrer to achieve a carbon dioxide (CO ₂ ) purity of 99.5 vol% at a flow rate of 100 mL / min. Bubbling was performed for a minute. Thereafter, the solid component in the carbon dioxide absorbent was collected by filtration and vacuum dried at 50 ° C. for 24 hours to obtain 11.0 g of a light yellow solid.

The obtained solid was analyzed by 1H-NMR and confirmed to be 3-phenylarylideneaminoguanidine bicarbonate represented by the following formula (3).
1H-NMR measurement conditions:
(DMSO-d6, 500 MHz, δ; ppm) = 5.5 (s; 2H), 5.7-5.8 (br; 2H), 6.7 (d; 1H), 6.9 (dd; 1H) ), 7.2 (dd; 1H), 7.3 (dd; 2H), 7.5 (d; 2H), 7.8 (d; 1H))

Further, the following results were obtained when elemental analysis was performed using a CHN coder MT-6 (Yanaco Analytical Industrial Co., Ltd.), a simultaneous carbon, hydrogen, and nitrogen quantitative determination apparatus.
Calculated C, 52.79; H, 5.64; N, 22.39
Found C, 52.24; H, 5.49; N, 22.78

[Method of evaluating carbon dioxide absorption and recovery]
(Example 1)
9.5 g (10% by mass) of 3-phenylarylideneaminoguanidine obtained in Synthesis Example 1 and 85.5 g (90% by mass) of water were mixed to prepare 95 g of a slurry carbon dioxide absorbent. . This carbon dioxide absorbent is filled in a 200 mL flask, heated to 25 ° C. with an aluminum block, and stirred with a magnetic stirrer to achieve a carbon dioxide (CO ₂ ) purity of 99.5 vol% at a flow rate of 100 mL / min. Bubbling was performed for a minute. The weight of the carbon dioxide absorbent before and after aeration was measured, and the weight increase at 25 ° C. was calculated from the obtained weight. Then, was calculated from the amount of weight increase at 25 ° C. (CO ₂ absorption), 3-phenyl-arylidene aminoguanidine 1 mol mol amount of CO ₂ absorbed against the (CO ₂ absorption amount A). This apparatus diagram is shown in FIG.

Separately, a carbon dioxide absorbent was prepared, and the weight increase at 80 ° C. was calculated in the same manner as described above except that the heating temperature of the aluminum block was 80 ° C. The increase in weight at 80 ° C. from (CO ₂ absorption amount) was calculated 3-phenyl arylidene aminoguanidine 1 mol mol amount of CO ₂ absorbed against the (CO ₂ absorption amount C). Similarly, the molar amount of CO ₂ at 40 ° C. (CO ₂ absorption amount B) and the molar amount of CO ₂ at 100 ° C. (CO ₂ absorption amount D) were also measured.

The difference between the amount of CO ₂ mol absorbed at 25 ° C. and the amount of CO ₂ mol absorbed at 80 ° C. was evaluated as the CO ₂ recovery amount (AC). The room was at normal pressure and room temperature. The results are shown in Table 1.

(Example 2)
A carbon dioxide absorbent was prepared in the same manner as in Example 1 except that ethylene glycol (Tokyo Chemical Industry Co., Ltd.) was used instead of water, and the same apparatus as in Example 1 was used under the same conditions. The CO ₂ absorption amounts A to D and the CO ₂ recovery amount (AC) were measured.

(Comparative Example 1)
A carbon dioxide absorbent was prepared in the same manner as in Example 1 except that monoethanolamine (Tokyo Chemical Industry Co., Ltd.) was used instead of 3-phenylarylideneaminoguanidine, and the same apparatus as in Example 1 was prepared. Was used to measure the CO ₂ absorption amounts AD and the CO ₂ recovery amount (AC).

(Comparative Example 2)
A carbon dioxide absorbent was prepared in the same manner as in Example 1 except that ethylaminoethanol (Tokyo Chemical Industry Co., Ltd.) was used instead of 3-phenylarylideneaminoguanidine. Was used to measure the CO ₂ absorption amounts AD and the CO ₂ recovery amount (AC).

(Comparative Example 3)
A carbon dioxide absorbent was prepared in the same manner as in Example 1 except that methyldiethanolamine (Tokyo Chemical Industry Co., Ltd.) was used instead of 3-phenylallylideneaminoguanidine, and an apparatus similar to that in Example 1 was prepared. Used, under the same conditions, the CO ₂ absorption amounts A to D and the CO ₂ recovery amount (AC) were measured.

(Comparative Example 4)
A carbon dioxide absorbent was prepared in the same manner as in Example 1 except that diphenylamine (Tokyo Chemical Industry Co., Ltd.) was used instead of 3-phenylarylideneaminoguanidine, and the same apparatus as in Example 1 was used. Under the same conditions, the CO ₂ absorption amounts A to D and the CO ₂ recovery amount (AC) were measured.

PAG: 3- phenyl-allylidene aminoguanidine MEA: monoethanolamine EAE: ethylamino ethanol MDEA: methyldiethanolamine DPA: Diphenylamine CO ₂ absorption _units: CO 2 mol / amine mol

From Table 1, the carbon dioxide absorbent (Example 1) containing the alkylideneaminoguanidine of the present invention is excellent in carbon dioxide absorption performance at room temperature and carbon dioxide release performance at 80 ° C., and CO ₂ is superior to Comparative Examples 1 to 4. It was found that the recovery amount was large and CO ₂ could be separated and recovered with energy saving. Further, in the carbon dioxide absorbent in which alkylideneaminoguanidine is uniformly dissolved by using ethylene glycol instead of water (Example 2), the carbon dioxide absorbent in which alkylideneaminoguanidine is dispersed in water in a slurry state. As compared with Example 1, it was found that the CO ₂ absorption amount A increased and the CO ₂ recovery amount (AC) also increased.

[Evaluation of desorption temperature of carbon dioxide and heat resistance of compounds]
(Example 3)
A predetermined amount of 3-phenylarylideneaminoguanidine (solid) obtained in Synthesis Example 1 was measured, and the desorption temperature of carbon dioxide and the heat resistance were evaluated.

For the evaluation of the carbon dioxide desorption temperature and heat resistance of the carbon dioxide absorbent, a differential scanning calorimeter (manufactured by Seiko Instruments Inc.) and a thermogravimetric instrument (manufactured by Seiko Instruments Inc.) were used. The desorption temperature and melting point of carbon dioxide were determined from the endothermic peak by differential scanning calorimetry and the thermogravimetric decrease at the temperature showing the endothermic peak. Moreover, heat resistance was evaluated from the thermogravimetric temperature. The measurement conditions are shown below.
(Differential scanning calorimetry measurement conditions)
Container: Aluminum pan Temperature increase rate: 10 ° C / min
Atmosphere: N ₂
Measurement temperature: 30-330 ° C
(Measurement conditions for thermogravimetry)
Container: Aluminum pan Temperature increase rate: 10 ° C / min
Atmosphere: N ₂
Measurement temperature: 30-350 ° C

Example 4
The desorption temperature of carbon dioxide was the same as in Example 3 except that 3-phenylarylideneaminoguanidine bicarbonate (solid) obtained in Synthesis Example 2 was used instead of 3-phenylarylideneaminoguanidine. And the heat resistance of the compound was evaluated.

(Comparative Example 5)
The desorption temperature of carbon dioxide and the heat resistance of the compound were evaluated in the same manner as in Example 3 except that aminoguanidine bicarbonate (Tokyo Chemical Industry Co., Ltd.) was used instead of 3-phenylallylideneaminoguanidine.

(Comparative Example 6)
The desorption temperature of carbon dioxide and the heat resistance of the compound were evaluated in the same manner as in Example 3 except that guanidine carbonate (Tokyo Chemical Industry Co., Ltd.) was used instead of 3-phenylallylideneaminoguanidine.

* 1: Not observed because it does not contain carbon dioxide * 2: Contains carbon dioxide but not observed PAG: 3-phenylarylideneaminoguanidine PAG (C): Bicarbonate 3-phenylarylidene Aminoguanidine AG (C): Aminoguanidine bicarbonate G (C): Guanidine carbonate

Example 3 is an example using 3-phenylarylideneaminoguanidine before absorbing carbon dioxide, and Example 4 is 3-phenylarylideneaminoguanidine (bicarbonate) after absorbing carbon dioxide. Salt 3-phenylallylideneaminoguanidine).

From Table 2, the carbon dioxide absorbent containing the alkylidene aminoguanidine of the present invention has a lower carbon dioxide desorption temperature than the aminoguanidine bicarbonate having a similar structure (comparison of Example 4 and Comparative Example 5). Moreover, since the thermogravimetric reduction temperature was also high, it turned out that it is excellent also in heat resistance (comparison of Example 3 and Comparative Example 5). Further, although guanidine carbonate having a similar structure is excellent in heat resistance, no desorption of carbon dioxide was observed, indicating that it cannot be used as a carbon dioxide separating agent (Comparative Example 6).

From the above, it was shown that the alkylideneaminoguanidine contained in the carbon dioxide absorbent of the present invention exhibits excellent properties in carbon dioxide recovery, desorption temperature, and heat resistance.

This application includes a Japanese patent application filed with the Japan Patent Office on September 2, 2016 (Japanese Patent Application No. 2016-172182), and a Japanese patent application filed with the Japan Patent Office on December 14, 2016 (Japanese Patent No. 2016-242666), the contents of which are incorporated herein by reference.

The present invention can provide a carbon dioxide absorbent for absorbing and separating carbon dioxide contained in gas, and more specifically, carbon dioxide for energy-saving and stable separation. It has industrial applicability as an absorbent. Further, it has industrial applicability as a method for separating carbon dioxide from a gas containing carbon dioxide such as combustion exhaust gas.

Claims

Containing an alkylideneaminoguanidine represented by the following general formula (1),
Carbon dioxide absorbent.

(In the formula, R 1 and R 2 are each independently a hydrogen atom or a hydrocarbon group having 1 to 18 carbon atoms which may have a substituent.)
Further containing a solvent,
The carbon dioxide absorbent according to claim 1.
The solvent contains at least one selected from the group consisting of water, glycol solvents, alcohol solvents, and aprotic polar solvents,
The carbon dioxide absorbent according to claim 2.
The glycol solvent contains at least one selected from the group consisting of ethylene glycol, propylene glycol, and diethylene glycol,
The carbon dioxide absorbent according to claim 3.
The alkylidene aminoguanidine includes a compound represented by the following formula (2):
The carbon dioxide absorbent according to any one of claims 1 to 4.
The alkylidene aminoguanidine content is 5.0% by mass or more and 80.0% by mass or less based on the total amount of the carbon dioxide absorbent.
The carbon dioxide absorbent according to any one of claims 1 to 5.
The total content of the solvent is 1.0% by mass or more and 95.0% by mass or less with respect to the total amount of the carbon dioxide absorbent.
The carbon dioxide absorbent according to any one of claims 2 to 6.
A contacting step in which the carbon dioxide absorbent is absorbed by the carbon dioxide absorbent according to any one of claims 1 to 7 and a gas containing carbon dioxide;
Desorbing the carbon dioxide from the carbon dioxide absorbent by heating the carbon dioxide absorbent that has absorbed the carbon dioxide.
Carbon dioxide separation and recovery method.
The temperature in the contact step is 0 ° C. or more and less than 60 ° C.,
The method for separating and recovering carbon dioxide according to claim 8.
The temperature in the desorption step is 60 ° C. or higher and 120 ° C. or lower.
The method for separating and recovering carbon dioxide according to claim 8 or 9.
A carbon dioxide absorbent according to any one of claims 1 to 7, wherein a gas containing carbon dioxide and the carbon dioxide absorbent are brought into contact with each other to cause the carbon dioxide absorbent to absorb the carbon dioxide. An absorption device;
A desorption device that desorbs the carbon dioxide from the carbon dioxide absorbent by heating the carbon dioxide absorbent that has absorbed the carbon dioxide in the absorber.
Carbon dioxide separation and recovery device.
Having a recovery device for recovering the desorbed carbon dioxide;
The carbon dioxide separation and recovery device according to claim 11.