WO2019163867A1

WO2019163867A1 - Absorbent for carbon dioxide, and method for separating/collecting carbon dioxide

Info

Publication number: WO2019163867A1
Application number: PCT/JP2019/006457
Authority: WO
Inventors: 山本　信; 後藤　和也; フィロツアラムチョウドリ; 洋市松崎; 正巳小野田
Original assignee: 公益財団法人地球環境産業技術研究機構; 日本製鉄株式会社
Priority date: 2018-02-23
Filing date: 2019-02-21
Publication date: 2019-08-29
Also published as: JPWO2019163867A1; JP7146891B2

Abstract

Provided are: an absorbent for the efficient separation/collection of carbon dioxide in a carbon dioxide-containing gas with less energy; and a method for separating/collecting carbon dioxide using the absorbent. An absorbent for the separation/collection of carbon dioxide in a carbon dioxide-containing gas, the absorbent containing at least one alkanol amine compound represented by general formula [1], at least one tertiary aliphatic amine compound having an ether group and represented by general formula [2], and water, wherein the sum total of the mass concentrations of the amine compounds contained in the absorbent is 61 to 84%. General formula [1]: (wherein R¹ represents an alkyl group having 1 to 5 carbon atoms or a hydrogen group; R² and R³ independently represent an alkyl group having 1 or 2 carbon atoms or a hydrogen group; and n represents 2 or 3.) General formula [2]: (wherein R⁴ and R⁵ independently represent a tertiary alkyl amino group having 2 to 4 carbon atoms; and m represents 1, 2 or 3.)

Description

Carbon dioxide absorbent and carbon dioxide separation and recovery method

The present invention relates to an absorbent for separating and collecting carbon dioxide from a gas containing carbon dioxide with high efficiency, and a method for separating and collecting carbon dioxide using the absorbent.

In recent years, a rapid increase in greenhouse gas emissions such as carbon dioxide and methane accompanying human social activities has been cited as one of the causes of global warming. In particular, carbon dioxide is the most important greenhouse gas, and there is an urgent need to reduce carbon dioxide emissions in accordance with the Paris Agreement that came into effect in 2016.

Today, mixed gas discharged from coal, heavy oil, natural gas, etc., which is the source of carbon dioxide, is mixed with gas discharged from thermal power plants, ironworks blast furnaces, cement plant kilns, plant boilers, etc. A series of carbon dioxide capture and storage (CCS) technology that separates and recovers carbon dioxide contained in gas, compresses it, and injects it after transportation, until the development of alternative energy to replace fossil fuels. It is attracting attention as a bridging technology.

¡In order to put this storage technology into practical use, the lowest possible cost reduction is required. In the series of processes of carbon dioxide separation and recovery, compression, transportation, and injection, the cost required for carbon dioxide separation and recovery accounts for more than 60% of the total cost of carbon dioxide separation and recovery. Technological development to reduce carbon separation and recovery costs is important.

Therefore, in recent years, technology development of carbon dioxide separation and recovery by chemical absorption method mainly using an aqueous solution of an amine compound has been vigorously promoted for carbon dioxide-containing gas discharged from power plants and steelworks.

Examples of the amine compounds include monoethanolamine (MEA), which is a primary alkanolamine, diglycolamine (DGA), 2-amino-2-methyl-1-propanol (AMP), and 2- (methyl) which is a secondary alkanolamine. Amino) ethanol (MAE), 2- (ethylamino) ethanol (EAE), 2- (isopropylamino) ethanol (IPAE), 3- (isopropylamino) propanol (IPAP), diethanolamine (DEA), diisopropanolamine (DIPA) ), Tertiary alkanolamines N-methyldiethanolamine (MDEA), 2- (dimethylamino) ethanol (DMAE), triethanolamine (TEA), tertiary alkylamines N, N, N ', N'- Tetramethyl-1,6-diaminohexane (TMDAH), N, N, N ', N'-tetramethyl-1,4-diaminobutane (TMDAB), bis (2-dimethylaminoethyl) ether (BDER ) And the like are known, and MEA is particularly widely used.

When using an aqueous solution of the above amine compound as a liquid absorbent of carbon dioxide, primary alkanolamine such as MEA is highly corrosive to the equipment material for carbon dioxide separation and recovery, so use expensive corrosion resistant steel as the equipment material, Or measures such as lowering the amine concentration in the liquid absorbent are necessary.

In general, when regenerating the liquid absorbent, the absorbed carbon dioxide is released by heating the temperature of the liquid absorbent to about 120 ° C. The aqueous solution of the primary alkanolamine is used as the liquid absorbent. In some cases, the amount of carbon dioxide emitted during the regeneration of the liquid absorbent is not sufficient, and the heat of absorption reaction of primary alkanolamine with carbon dioxide is relatively high, resulting in a large per unit mass of carbon dioxide recovered as a result. Requires energy.

As a conventional technique for separating and recovering carbon dioxide with less energy, for example, Patent Document 1 discloses an aqueous solution of a secondary alkanolamine having steric hindrance such as an alkyl group around an amino group and combustion exhaust gas under atmospheric pressure. The method of removing carbon dioxide in the combustion exhaust gas by the method of contacting the carbon dioxide and absorbing carbon dioxide is described.

In Patent Document 1, examples of MAE and EAE are described as secondary alkanolamines, and it is described that a 30% by mass aqueous solution of MAE and EAE is preferable for absorption of carbon dioxide. As other secondary alkanolamines, although no examples are described, four types of amines such as 2-isopropylaminoethanol (IPAE) are described.

Patent Document 2 describes a liquid absorbent containing only IPAE, which is also a secondary alkanolamine, and is characterized by high absorbability and dispersibility, but as shown in Comparative Example 2. In order to make carbon dioxide recovery more efficient, if the concentration is increased to 60% by mass or more, the absorption rate will decrease and the amount of emission will decrease greatly. The results to be described are described.

In Patent Document 3, an aqueous solution of a tertiary alkanolamine is used as a liquid absorbent, and an acid gas regeneration method is performed under a pressure exceeding 3.5 bar absolute pressure (about 0.35 MPa) and not exceeding 20 bar absolute pressure (about 2 MPa). Is described. In this patent document, an example of a 43% by mass aqueous solution of MDEA as a tertiary alkanolamine is described. Examples of other tertiary alkanolamines include TEA and the like although no examples are described. These tertiary alkanolamines are generally known to have a relatively low heat of absorption reaction with carbon dioxide compared to primary or secondary alkanolamines, and are expected to significantly reduce the energy required for the separation and recovery of carbon dioxide. Is done.

Patent Document 3 is an invention intended to use an aqueous solution of MDEA or TEA as a liquid absorbent of carbon dioxide in a region where the partial pressure of carbon dioxide assumed in coal gasification product gas, mined natural gas, or the like is high. It is. These tertiary alkanolamines are effective in recovering carbon dioxide and regenerating liquid absorbents against relatively low partial pressure carbon dioxide (generally around 0.02 MPa) generated from thermal power plants and steelworks blast furnaces. Low, and thus the energy per unit mass of carbon dioxide recovered is high.

In US Pat. No. 6,057,086, an absorbent for removing carbon dioxide from a gas stream having a high carbon dioxide partial pressure of 2 bar (about 0.2 MPa) or more, in particular for removing carbon dioxide from exhaust gas from a coal gasification process. And absorption and recovery methods are described. The absorbent is a tertiary aliphatic diamine aqueous solution having no hydrogen bonding group and having an ether group.

In the example of Patent Document 4, an aqueous solution of BDER is described as the tertiary aliphatic diamine. By using the aqueous BDER solution at a high concentration (60 to 90% by mass), the partial pressure of carbon dioxide is 10 bar ( It is described that in a high region of about 1 MPa or more, a high carbon dioxide recovery rate and a high carbon dioxide absorption rate and a high carbon dioxide emission rate can be obtained. BDER used in the patent document is also known to have a relatively low heat of absorption reaction with carbon dioxide, similar to MDEA or TEA. And the efficiency of regeneration of the liquid absorbent is low.

Patent Document 5 describes an aqueous solution containing a secondary alkanolamine having steric hindrance and a tertiary alkylamine consisting only of a saturated hydrocarbon chain, and a method for recovering carbon dioxide using the aqueous solution. In the patent document, examples of TMDAH and TMDAB are shown as tertiary alkylamines contained in an aqueous solution, and a relatively high carbon dioxide absorption and desorption are obtained when IPAE is used as a secondary alkanolamine. The amount is shown. Examples of secondary alkanolamines include IPAP and EAE in addition to IPAE.

Patent Document 5 shows relatively high performance when the total amine concentration in the aqueous solution is in the range of 50 to 60% by mass. However, tertiary alkylamines consisting only of saturated hydrocarbons are generally relatively viscous, and in Comparative Example 6 of this specification, a significant decrease in performance is shown by increasing the total amine concentration to 60% by mass or more. ing.

Patent Document 6 describes a secondary alkanolamine having steric hindrance, a liquid composed only of a polyamine containing two or more amino groups and water, and a method for recovering carbon dioxide using the liquid. In this patent document, examples of primary, secondary and / or tertiary alkyl polyamines composed only of saturated hydrocarbon chains and primary alkyl polyamines containing ether groups are shown as polyamines contained in the liquid. Examples of secondary alkanolamines for IPAE and EAE are shown.

Patent Document 6 shows that high performance can be obtained by containing the polyamine in the liquid at a low mass concentration of about 0.2 to 1%. However, primary alkyl polyamines generally have a high carbon dioxide absorption reaction heat and are poor in carbon dioxide desorption. In addition, alkylpolyamines consisting only of saturated hydrocarbon chains are generally highly viscous. Therefore, as shown in Comparative Examples 7 to 10 in the present specification, when the polyamine is contained at a higher mass concentration, high performance cannot be obtained.

In addition, in the above-mentioned Patent Document 6, the effect of increasing the total amine concentration of the absorbent with a tertiary aliphatic amine compound having a low viscosity by having an ether group as provided by the present invention is not found at all. Not mentioned.

Japanese Patent Laid-Open No. 5-301023 JP 2009-6275 Gazette International Publication No. 2005/009592 International Publication No. 2011/071150 International Publication No.2013 / 118819 International Publication No. 2014/129400

In today's world where reduction of carbon dioxide generation, energy saving and resource saving are required, the large amount of energy consumption in carbon dioxide separation and recovery has become a major factor that hinders the practical application of this technology. There is a need for separation and recovery technology.

An object of the present invention is to provide an absorbent for efficiently separating and recovering carbon dioxide in a gas containing carbon dioxide with less energy and a method for separating and recovering carbon dioxide using the same.

As a result of intensive studies on an absorbent that can efficiently absorb and dissipate carbon dioxide and recover high-purity carbon dioxide with high efficiency, the present inventors have found that the alkanolamine represented by the general formula [1] The aqueous solution containing the compound and the tertiary aliphatic amine compound having an ether group represented by the general formula [2] has a high carbon dioxide recovery amount, a low specific heat and a low carbon dioxide absorption heat. It was found that the required energy consumption can be kept low.

The present invention has been completed based on the above findings, and has been completed. Further, the present invention provides an absorbent for separating and recovering the following carbon dioxide and a method for separating and recovering carbon dioxide using the same. To do.
Item 1. An absorbent for separating and recovering carbon dioxide from a gas containing carbon dioxide, which is represented by at least one alkanolamine compound represented by general formula [1] and at least one general formula [2] An absorbent comprising a tertiary aliphatic amine compound having an ether group and water, wherein the total mass concentration of the amine compound contained in the absorbent is 61 to 84%.
General formula [1]:

(Wherein R ¹ represents an alkyl group having 1 to 5 carbon atoms or a hydrogen group, R ² and R ³ each independently represents an alkyl group having 1 or 2 carbon atoms or a hydrogen group, and n is 2 or 3)
General formula [2]:

(Wherein R ⁴ and R ⁵ each independently represents a tertiary alkylamino group having 2 to 4 carbon atoms, and m represents 1, 2 or 3).
Item 2. The mass concentration of the alkanolamine compound is 37 to 83%, the mass concentration of the tertiary aliphatic amine compound having an ether group is 1 to 24%, and the mass concentration of water is 16 to 39%. Item 10. The absorbent according to Item 1, which is characterized.
Item 3. The total mass concentration of the amine compound contained in the absorbent is 65 to 80%, the mass concentration of the alkanolamine compound is 45 to 75%, and the mass concentration of the tertiary aliphatic amine compound having an ether group Item 5. The absorbent according to Item 1, wherein the absorbent is 5 to 20% and the mass concentration of water is 20 to 35%.
Item 4. The alkanolamine compound is monoethanolamine, 2-amino-2-methyl-1-propanol, 2- (methylamino) ethanol, 2- (ethylamino) ethanol, 2- (isopropylamino) ethanol and 3- (isopropyl Item 4. The absorbent according to any one of Items 1 to 3, which is at least one selected from the group consisting of amino) propanol.
Item 5. The alkanolamine compound is at least one selected from the group consisting of 2-amino-2-methyl-1-propanol, 2- (ethylamino) ethanol, 2- (isopropylamino) ethanol and 3- (isopropylamino) propanol. Item 4. The absorbent according to any one of Items 1 to 3, which is a seed.
Item 6. Item 3. The tertiary aliphatic amine compound having an ether group is at least one selected from the group consisting of tertiary aliphatic amines having an ether group, molecular symmetry, and no hydroxy group. To 5. The absorbent according to any one of 5 to 5.
Item 7. Any of the items 1 to 5, wherein the tertiary aliphatic amine compound having an ether group is at least one selected from the group consisting of bis (2-dimethylaminoethyl) ether and bis (2-morpholinoethyl) ether. The absorbent according to claim 1.
Item 8. A method for separating and recovering carbon dioxide from a gas containing carbon dioxide, including the following steps A and B:
The process A which makes the absorber as described in any one of claim | item 1 to 7 contact with the gas containing a carbon dioxide, and obtains the absorber which absorbed the carbon dioxide from the gas containing a carbon dioxide, and
A process B in which the absorbent obtained by absorbing the carbon dioxide obtained in the step A is heated to desorb and dissipate the carbon dioxide from the absorbent, and the diffused carbon dioxide is recovered.
Item 9. Item 9. The method for separating and recovering carbon dioxide from the carbon dioxide-containing gas according to Item 8, wherein the step A is performed at a temperature of 25 to 60 ° C, and the step B is performed at a temperature of 70 to 150 ° C.
Item 10. The process A is performed under a pressure of 1.0 bar or higher, and the process B is performed under a pressure of 3.5 bar or lower. Method.

According to the present invention, since the absorbent has a high carbon dioxide recovery amount, a low specific heat, and a low carbon dioxide absorption heat, the energy consumption required for the carbon dioxide recovery amount can be kept low. Carbon dioxide can be separated and recovered. Furthermore, a more compact carbon dioxide separation and recovery facility can be designed, and the initial cost is reduced.

6 is a graph comparing the absorbent performance of Examples 1 to 11 and Comparative Examples 1 to 12. (●: Examples 1 to 11, Δ: Comparative Examples 1 to 12)

Hereinafter, the present invention will be described in detail.

Absorbent for separating and recovering carbon dioxide The absorbent for separating and recovering carbon dioxide from a gas containing carbon dioxide of the present invention at low energy is an alkanolamine compound represented by at least one general formula [1] And at least one tertiary aliphatic amine compound having an ether group represented by the general formula [2] and water.

Alkanolamine compound represented by general formula [1]

(Wherein R ¹ represents an alkyl group having 1 to 5 carbon atoms or a hydrogen group, R ² and R ³ each independently represents an alkyl group having 1 or 2 carbon atoms or a hydrogen group, and n is 2 or 3)
A tertiary aliphatic amine compound having an ether group represented by the general formula [2]

(Wherein R ⁴ and R ⁵ each independently represents a tertiary alkylamino group having 2 to 4 carbon atoms, and m represents 1, 2 or 3).

In the general formula [1], R ¹ represents an alkyl group having 1 to 5 carbon atoms or a hydrogen group.

The alkyl group having 1 to 5 carbon atoms may be linear or branched, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, Examples include n-pentyl, isopentyl, sec-pentyl, tert-pentyl, 3-pentyl and the like.

Preferred R ¹ is a hydrogen atom, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, tert-pentyl or 3-pentyl, more preferably a hydrogen atom, methyl, ethyl or isopropyl. is there.

In the general formula [1], R ² and R ³ each independently represents an alkyl group having 1 or 2 carbon atoms or a hydrogen group.

Examples of the alkyl group having 1 or 2 carbon atoms include methyl and ethyl.

Preferred R ² is a hydrogen atom or methyl. The same applies to R ³ .

In the general formula [1], n represents 2 or 3, preferably 2.

Specific examples of the alkanolamine compound represented by the general formula [1] include monoethanolamine, 2-amino-2-methyl-1-propanol, 2- (methylamino) ethanol, 2- (ethylamino) ethanol, Examples include 2- (isopropylamino) ethanol and 3- (isopropylamino) propanol.

The absorbent of the present invention may contain one alkanolamine compound represented by the general formula [1] alone, or two or more kinds at the same time.

In the general formula [2], R ⁴ and R ⁵ each independently represents a tertiary alkylamino group having 2 to 4 carbon atoms.

In the tertiary alkylamino group having 2 to 4 carbon atoms, two identical or different alkyl groups which may have a substituent are bonded to the nitrogen atom constituting the amino group, and the number of carbon atoms of the alkyl group is An amino group whose sum is 2 to 4.

The alkyl group may have a substituent, and a hetero atom may be interposed between the alkyl chains or between the nitrogen atom and the alkyl group.

In addition, each alkyl group may be independently linear, branched or cyclic, and two alkyl groups bonded to a nitrogen atom are bonded to each other to form a cyclic structure with the nitrogen atom. May be.

Examples of the linear or branched alkyl group include methyl, ethyl, n-propyl, and isopropyl. Examples of the cyclic alkyl group include cyclopropyl. Examples of the alkyl group in which two alkyl groups bonded to a nitrogen atom are bonded to each other to form a cyclic structure with the nitrogen atom include ethyleneimino and pyrrolidino.

The alkyl group in which two alkyl groups bonded to a linear, branched, cyclic, or nitrogen atom are bonded to each other to form a cyclic structure with the nitrogen atom has at most three substituents. In addition, at most one heteroatom may be interposed between each alkyl chain or between each nitrogen atom and each alkyl group. Examples of the substituent include a hydroxy group, a thiol group, a fluoro group, a chloro group, a bromo group, and an iodo group. Examples of the hetero atom include an oxygen atom, a sulfur atom, and a phosphorus atom, and an oxygen atom is preferable.

Examples of the tertiary alkylamino group having 2 to 4 carbon atoms include, for example, dimethylamino, ethyl (methyl) amino, diethylamino, isopropyl (methyl) amino, methoxy (methyl) amino, methoxy (optionally substituted). Ethyl) amino, dimethoxyamino, ethoxy (methyl) amino, ethoxy (ethyl) amino, diethoxyamino, methoxymethyl (methyl) amino, methoxymethyl (ethyl) amino, dimethoxymethylamino, methoxyethyl (methyl) amino, ethoxymethyl (Methyl) amino, morpholino and the like.

Preferred R ⁴ is dimethylamino, diethylamino, dimethoxymethylamino or morpholino. R ⁵ is the same.

In the general formula [2], m represents 1, 2 or 3, preferably 1 or 2, and more preferably 1.

In the present invention, a tertiary aliphatic amine compound having an ether group represented by the general formula [3] is also preferred as the tertiary aliphatic amine compound having an ether group represented by the general formula [2].

Tertiary aliphatic amine compound having an ether group represented by the general formula [3]

(In the formula, R ⁶ and R ⁷ are a total of 2 to 4 carbon atoms in both groups, and each independently represents an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, or a carbon atom. An alkoxyalkyl group of 2 to 3 or a group of 6-membered rings together with a nitrogen atom that is an alkyl group of 2 carbon atoms, and both groups are bonded to each other through one oxygen atom to form an amino group R ⁸ and R ^{9 each} represent a cyclic structure, and the total number of carbon atoms of both groups is 2 to 4, and each independently represents an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, or 6-membered ring with an alkoxyalkyl group having 2 to 3 carbon atoms, or a nitrogen atom that forms an amino group bonded to each other through one oxygen atom, both of which are the same alkyl group having 2 carbon atoms And L represents 1, 2 or 3.)

In the general formula [3], the alkyl group having 1 to 3 carbon atoms may be linear or branched, and examples thereof include methyl, ethyl, propyl, isopropyl and the like.

The alkoxy group having 1 to 3 carbon atoms may be linear or branched, and examples thereof include methoxy, ethoxy, propoxy, isopropoxy and the like.

Examples of the alkoxyalkyl group having 2 to 3 carbon atoms include methoxymethyl, methoxyethyl, ethoxymethyl and the like.

The 6-membered ring structure represented by the nitrogen atoms constituting the amino group in which both groups are the same alkyl group having 2 carbon atoms and bonded to each other through one oxygen atom is morpholino.

In the general formula [3], L represents 1, 2 or 3, preferably 1 or 2, and more preferably 1.

Preferred R ⁶ and R ⁷ are all methyl, both ethyl, both methoxymethyl, and morpholino. The same applies to R ⁸ and R ⁹ .

Preferred —NR ⁶ R ⁷ is dimethylamino, diethylamino, dimethoxymethylamino or morpholino. The same applies to -NR ⁸ R ⁹ .

Specific examples of the tertiary aliphatic amine compound having an ether group represented by the general formulas [2] and [3] include bis (2-dimethylaminoethyl) ether, bis (2-diethylaminoethyl) ether, 1, Examples include 8-bis (dimethylamino) -3,6-dioxaoctane, 1,11-bis (dimethylamino) -3,6,9-trioxaundecane, and bis (2-morpholinoethyl) ether.

The absorbent of the present invention may contain one kind of tertiary aliphatic amine compound having an ether group represented by the general formula [2], or two or more kinds at the same time.

The alkanolamine compound represented by the general formula [1] and the tertiary aliphatic amine compound having an ether group represented by the general formula [2] are commercially available or can be produced by a known method.

The total mass concentration of the amine compound contained in the absorbent of the present invention is preferably higher than 60% and lower than 85%, and the mass concentration of water contained in the absorbent of the present invention is lower than 40% and 15%. Higher is preferred.

By making the total mass concentration of the amine compound contained in the absorbent of the present invention higher than 60% and the water mass concentration lower than 40%, the dielectric constant of the absorbent can be significantly reduced, and carbon dioxide The solvation energy in the reaction with is reduced. As a result, the carbon dioxide absorption heat can be significantly reduced. Furthermore, the effect of reducing the specific heat of the absorbent is also obtained.

Conventional carbon dioxide absorbents consisting of an aqueous solution of an amine compound, due to the increased concentration of the amine compound, increase in viscosity is remarkably suppressed, and the mass concentration of water contributing to the reaction with carbon dioxide is reduced. Therefore, when the mass concentration of the amine compound is increased from 60%, that is, when the mass concentration of water is lower than 40%, the performance is remarkably deteriorated.

The tertiary aliphatic amine compound having an ether group generally has a low viscosity. Therefore, the absorbent of the present invention has a tertiary aliphatic amine compound having an ether group represented by the general formula [2]. By increasing the concentration of water, even when the mass concentration of water is lower than 40%, it is possible to maintain good reactivity with carbon dioxide and water without suppressing the diffusion of the substance.

If the total mass concentration of the amine compound contained in the absorbent of the present invention is higher than 60% and lower than 85%, and the mass concentration of water is lower than 40% and higher than 15%, as described above, carbon dioxide In addition, while maintaining good reactivity with water, the effect of reducing the heat of absorption of carbon dioxide and lowering the specific heat can be obtained.

The total mass concentration of the amine compound contained in the absorbent of the present invention is more preferably 61 to 84%, still more preferably 65 to 80%. Further, the mass concentration of water contained in the absorbent of the present invention is more preferably 16 to 39%, and still more preferably 20 to 35%.

The water contained in the absorbent of the present invention is not particularly limited, and distilled water, ion-exchanged water, tap water, ground water, etc. can be used as appropriate.

The mass concentration of the alkanolamine compound contained in the absorbent of the present invention is preferably 37 to 83%. Within this range, due to the high carbon dioxide absorptivity of the alkanolamine compound, the absorbent has a high carbon dioxide recovery amount, and the concentration of the amine compound contained in the absorbent can be increased. More preferably, it is 45 to 75%.

The mass concentration of the tertiary aliphatic amine compound having an ether group contained in the absorbent of the present invention is preferably 1 to 24%. Within this range, the increase in viscosity due to the increase in concentration of the amine compound contained in the absorbent is suppressed, and while maintaining good reactivity with carbon dioxide and water, the carbon dioxide absorption heat is reduced and the specific heat is reduced. An effect is obtained. Moreover, the tertiary aliphatic amine compound having an ether group represented by the general formula [2] has the ability to absorb and dissipate carbon dioxide as an aqueous solution, thereby increasing the amount of carbon dioxide recovered by the absorbent. An effect is also obtained. More preferably, it is 5 to 20%.

The tertiary aliphatic amine compound having an ether group contained in the absorbent of the present invention preferably has molecular symmetry. Tertiary aliphatic amine compounds having an ether group and high molecular symmetry have a very low dielectric constant, so that the solvation energy of the absorbent obtained by increasing the concentration of the amine compound contained in the absorbent is reduced. As a result, the effect of reducing the heat absorbed by carbon dioxide is high.

Among the tertiary aliphatic amine compounds having an ether group contained in the absorbent of the present invention, a compound having molecular symmetry is a compound in which R ⁴ and R ⁵ have the same chemical structure in the general formula [2]. In general formula [3], NR ⁶ R ⁷ and NR ⁸ R ⁹ are compounds having the same chemical structure. For example, bis (2-dimethylaminoethyl) ether, bis (2-diethylaminoethyl) ether, 1,8-bis (dimethylamino) -3,6-dioxaoctane, 1,11-bis (dimethylamino) -3 , 6,9-trioxaundecane, bis (2-morpholinoethyl) ether.

The tertiary aliphatic amine compound having an ether group contained in the absorbent of the present invention preferably has no hydroxy group. A tertiary aliphatic amine compound having an ether group generally has a low viscosity, but a hydroxy group has a high hydration property and thus increases the viscosity of an absorbent containing water. By containing a tertiary aliphatic amine compound having an ether group and no hydroxy group, the absorbent can be further reduced in viscosity and excellent in carbon dioxide absorption performance and emission performance. Even if the concentration of the amine compound contained in is increased, a high carbon dioxide recovery amount can be obtained.

The absorbent of the present invention contains components other than the alkanolamine compound represented by the general formula [1], the tertiary aliphatic amine compound having an ether group represented by the general formula [2], and water as necessary. In addition, it may be included within a range that does not impair the effects of the present invention. Other components include stabilizers (side reaction inhibitors such as antioxidants) for securing the chemical or physical stability of the absorbent of the present invention, and materials for devices and equipment using the absorbent of the present invention. Examples include an inhibitor (such as a corrosion inhibitor) for preventing deterioration of carbon dioxide, a physical absorbent of carbon dioxide for supplementing absorption and emission of carbon dioxide by the absorbent of the present invention, and the like. The content of these other components in the absorbent of the present invention is not particularly limited as long as it does not inhibit the effects of the present invention, but is preferably 5% or less by mass concentration.

Examples of the antioxidant include dibutylhydroxytoluene, butylhydroxyanisole, sodium erythorbate, sodium sulfite, and sulfur dioxide.

Examples of the corrosion inhibitor include 1-hydroxyethane-1,1-diphosphonic acid, 2-phosphonobutane-1,2,4-tricarboxylic acid, 1-phosphonopropane-2,3-dicarboxylic acid, phosphonosuccinic acid, 2-hydroxyphosphonoacetic acid, maleic acid-based polymer (for example, a copolymer of maleic acid and amylene, or a terpolymer of maleic acid, acrylic acid, and styrene).

Examples of the physical absorbent include, for example, cyclotetramethylene sulfone and derivatives thereof, aliphatic acid amides (for example, acetylmorpholine or N-formylmorpholine), N-alkylated pyrrolidones and corresponding piperidones (for example, N-methylpyrrolidone, or N-methylpiperidone), propylene carbonate, methanol, dialkyl ethers of polyethylene glycol and the like.

Gases containing carbon dioxide include, for example, thermal power plants fueled with coal, heavy oil, natural gas, boilers at factories, kilns at cement plants, ironmaking blast furnaces that reduce iron oxide with coke, carbon in pig iron Exhaust gas from coal-fired combined power generation facilities, etc., natural gas at the time of mining, reformed gas, etc., and the carbon dioxide concentration in the gas is usually 5-50 by volume. %, Especially about 10-40%. In such a carbon dioxide concentration range, the effects of the present invention are suitably exhibited. The gas containing carbon dioxide may contain gases such as N ₂ , water vapor, CO, H ₂ S, COS, SO ₂ , NO ₂ , CH ₄ , and hydrogen in addition to carbon dioxide.

A method for separating and recovering carbon dioxide using an absorbent according to the present invention is a method for separating and recovering carbon dioxide in a gas containing carbon dioxide. Step A for obtaining an absorbent that has absorbed carbon dioxide from a gas containing carbon dioxide, and contacting the gas containing carbon dioxide, and heating the absorbent that has absorbed carbon dioxide obtained in step A, from the absorbent It includes a step B in which carbon dioxide is desorbed and released, and the released carbon dioxide is recovered.

(Process A)
In the step A, the absorbent is brought into contact with a gas containing carbon dioxide, so that the carbon dioxide in the gas containing carbon dioxide is absorbed by the absorbent and separated.

The method for bringing the absorbent into contact with the gas containing carbon dioxide in step A is not particularly limited. For example, a method of bubbling a gas containing carbon dioxide in the absorbent, a method of dropping the absorbent into a gas containing carbon dioxide (a spray or spray method), and a magnetic or metal mesh filler Examples thereof include a method in which a gas containing high-pressure carbon dioxide and an absorbent are brought into countercurrent contact in an absorption tower.

The temperature in step A can be 25-60 ° C. If it is this range, an absorber will be excellent in a carbon dioxide recovery amount and a carbon dioxide absorption rate. The temperature in step A is preferably 25 to 50 ° C, more preferably 25 to 40 ° C.

The pressure in step A is usually 1.0 bar or higher, preferably 1.0 to 3.5 bar. Further, higher carbon dioxide absorption performance can be obtained by carrying out at a higher pressure.

(Process B)
In the process B, the absorbent that has absorbed the carbon dioxide obtained in the process A is heated to desorb and dissipate carbon dioxide from the absorbent, and the diffused carbon dioxide is recovered.

The temperature in the step B of desorbing and releasing carbon dioxide can be 70 to 150 ° C. Within this range, the absorbent is excellent in the carbon dioxide emission rate. The temperature in step B is preferably 70 to 120 ° C, more preferably 70 to 100 ° C.

The pressure in the step B of desorbing and releasing carbon dioxide in step B is usually 3.5 bar or less, preferably 1.0 to 3.5 bar. Further, higher carbon dioxide emission performance can be obtained by carrying out at a lower pressure.

The method for heating and absorbing the carbon dioxide-absorbing agent to desorb and dissipate the carbon dioxide and recovering it is not particularly limited. For example, as with distillation, the absorbent is heated and bubbled in a kettle, and the liquid interface is expanded in a diffusion tower containing packing materials such as plate towers, spray towers, magnetic, metal mesh, etc. The method of heating etc. are mentioned. By these methods, pure or very high concentration carbon dioxide can be recovered.

The absorbent after releasing carbon dioxide in the process B can be returned to the process A and recycled. In the circulation process, the heat applied in the step B is utilized for increasing the temperature of the absorbent by heat exchange with the absorbent that has absorbed carbon dioxide. The heat exchange can reduce the energy of the entire carbon dioxide separation and recovery process.

The carbon dioxide separated and recovered by the method for separating and recovering carbon dioxide with the absorbent of the present invention usually has a volume concentration of 95 to 100%, and may be pure or very high. The separated and recovered carbon dioxide can be subjected to sequestration and storage (CCS) and enhanced oil recovery (EOR), which are currently under development of the technology. In addition, the use application of the separated and recovered carbon dioxide is not particularly limited. For example, synthetic raw materials such as chemical products, or a cooling agent for freezing foods can be used.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

The reagents and gas types used in the reagent examples and comparative examples are shown in Table 1 and Table 2, respectively.

Test method (carbon dioxide recovery)
In the examples and comparative examples, the measurement of the amount of carbon dioxide recovered with respect to the absorbent is carried out using a carbon dioxide gas cylinder and a nitrogen gas cylinder, a carbon dioxide gas flow rate controller and a nitrogen gas flow rate controller, a glass reaction vessel (0.5 L), a temperature regulator, and a gas flow meter. , A chiller, and a carbon dioxide concentration meter (IR100, manufactured by Yokogawa Electric Corporation) were used in sequence to perform the carbon dioxide absorption and emission device.

The periphery of the glass reaction vessel was covered with an electric heater, and the temperature regulator was used to arbitrarily control the temperature of the absorbent in the glass reaction vessel. A stirring blade was provided in the glass reaction vessel, and the gas-liquid contact was promoted by forcibly stirring the absorbent in the glass reaction vessel.

After adding 0.1 L of absorbent into the glass reaction vessel, the gas inside the glass reaction vessel was replaced with nitrogen gas. The absorbent in the glass reaction vessel was maintained under the temperature and pressure conditions of the carbon dioxide absorption process. Carbon dioxide gas at a flow rate of 0.14 L / min and nitrogen gas at a flow rate of 0.56 L / min were blown into the absorbent in the glass reaction vessel to start the carbon dioxide absorption process and continued for 2 hours.

The temperature condition and pressure condition in the carbon dioxide absorption process and carbon dioxide emission process were a temperature of 40 ° C. and a pressure of 1 bar, a temperature of 70 ° C. and a pressure of 1 bar, respectively. However, the above temperature conditions and pressure conditions do not limit the present invention.

After completion of the carbon dioxide absorption step, the absorbent in the glass reaction vessel was set to the temperature and pressure conditions of the carbon dioxide emission step, and the carbon dioxide emission step was started and continued for 2 hours. In the carbon dioxide absorption step and the emission step, the exhaust gas from the glass reaction vessel was analyzed with a carbon dioxide concentration meter.

The amount of carbon dioxide dissolved in the absorbent S _c [g / L] was determined from the change over time of the carbon dioxide concentration C [volume%] obtained from the carbon dioxide concentration meter using the following equation [4].

The amount of carbon dioxide recovered by the absorbent was defined as a value obtained by subtracting the amount of carbon dioxide dissolved 2 hours after the start of the carbon dioxide emission process from the amount of carbon dioxide dissolved 2 hours after the start of the carbon dioxide absorption process.

(CO2 absorption heat)
The carbon dioxide absorption heat was measured using a differential calorimeter (DRC Evolution manufactured by SETARAM). Two reactors of the same shape were each filled with a predetermined amount of absorbent, and a predetermined amount of carbon dioxide was blown into only one reactor while stirring at 40 ° C. The calorific value per absorbed amount of carbon dioxide was determined from the difference in calorific value between the two reactors at a given time and the amount of carbon dioxide dissolved in the absorbent, and was defined as the carbon dioxide absorption heat.

(Absorbent specific heat)
The specific heat of the absorbent was measured using a liquid specific heat meter (SHA-500 manufactured by Kyoto Electronics Industry Co., Ltd.).

Examples 1 to 3
For the absorbent containing IPAE as the alkanolamine compound, BDER as the tertiary aliphatic amine compound having an ether group, and the water at the concentrations shown in Table 3, respectively, the amount of carbon dioxide recovered, the carbon dioxide absorption in accordance with the test methods Heat and absorbent specific heat were measured.

Examples 4 to 9
Table 3 shows IPAE and AMP (Examples 4 to 8) or IPAE and EAE (Example 9) as the alkanolamine compound, BDER as the tertiary aliphatic amine compound having the ether group, and water. For the absorbent contained in concentration, carbon dioxide recovery, carbon dioxide absorption heat and absorbent specific heat were measured according to the test method.

Examples 10-11
IPAE and AMP (Example 10) or IPAE and EAE (Example 11) as the alkanolamine compound, BMER as the tertiary aliphatic amine compound having an ether group, and water at concentrations shown in Table 3, respectively. About the absorber to contain, according to the said test method, the carbon dioxide recovery amount, the carbon dioxide absorption heat, and the absorber specific heat were measured.

Examples 12-13
About the absorbent containing IPAP (Example 12) or EAE (Example 13) as the alkanolamine compound, BDER as the tertiary aliphatic amine compound having the ether group, and the water at concentrations shown in Table 3, respectively. According to the test method, the carbon dioxide recovery, carbon dioxide absorption heat and absorbent specific heat were measured.

Comparative Examples 1 to 3
For the absorbent containing IPAE and the water as the alkanolamine compound at the concentrations shown in Table 3 and not containing the tertiary aliphatic amine compound having the ether group, the carbon dioxide recovery amount, carbon dioxide The heat of absorption and the specific heat of the absorbent were measured.

Comparative Examples 4-6
As the alkanolamine compound, IPAE, TMDAH, which is a tertiary alkylamine consisting only of a saturated hydrocarbon chain, and the water are contained at the concentrations shown in Table 3, respectively, and the tertiary aliphatic amine compound having the ether group is not included. The absorbent was measured for carbon dioxide recovery, carbon dioxide absorption heat, and specific heat of the absorbent according to the test method.

Comparative Examples 7-8
Absorption which does not contain the tertiary aliphatic amine compound which has IPAE, DAMPA which is a primary alkyl polyamine which consists only of a saturated hydrocarbon chain, and the water as the alkanolamine compound at the concentrations shown in Table 3, respectively. With respect to the agent, the amount of carbon dioxide recovered, the carbon dioxide absorption heat, and the specific heat of the absorbent were measured according to the test method.

Comparative Examples 9-10
For the absorbent containing IPAE as the alkanolamine compound, BAEOE, which is a primary alkyl polyamine containing an ether group, and water, each at a concentration shown in Table 3, and not containing a tertiary aliphatic amine compound having the ether group, According to the test method, the carbon dioxide recovery, carbon dioxide absorption heat and absorbent specific heat were measured.

Comparative Example 11
With respect to the absorbent containing IPAE and AMP as the alkanolamine compound and water at the concentrations shown in Table 3 and not containing the tertiary aliphatic amine compound having the ether group, the amount of carbon dioxide recovered, The carbon absorption heat and the specific heat of the absorbent were measured.

Comparative Example 12
With respect to the absorbent containing IPAE and AMP as the alkanolamine compound, BDER as the tertiary aliphatic amine compound having the ether group, and the water in the concentrations shown in Table 3, the amount of carbon dioxide recovered according to the test method, carbon dioxide The heat of absorption and the specific heat of the absorbent were measured.

Comparative Examples 13-14
About the absorbent containing IPAP (Comparative Example 13) or EAE (Comparative Example 14) as the alkanolamine compound and the water at the concentrations shown in Table 3 and not containing the tertiary aliphatic amine compound having the ether group. According to the test method, the carbon dioxide recovery, carbon dioxide absorption heat and absorbent specific heat were measured.

The results obtained in Examples 1 to 13 and Comparative Examples 1 to 14 are shown in Table 3, and the results obtained in Examples 1 to 11 and Comparative Examples 1 to 12 are shown in FIG. In addition,% in a table | surface represents mass concentration.

The C value in the table is a value obtained by dividing the specific heat B of the absorbent by the amount of carbon dioxide recovered A and multiplying by 1000, and is a value that is a measure of the amount of heat consumed when carbon dioxide is separated and recovered by the absorbent. It is. It means that the carbon dioxide can be separated and recovered with lower energy as the absorbent has a lower C value and heat of absorption of carbon dioxide.

From a comparison between Examples 1 to 11 and Comparative Examples 1 to 11, the absorbent containing the tertiary aliphatic amine compound having an ether group was compared with the absorbent not containing the tertiary aliphatic amine compound having an ether group. It has been confirmed that it has a low C value and a low heat of carbon dioxide absorption, and clearly shows the effect of the absorbent according to the present invention containing a tertiary aliphatic amine compound having an ether group.

From the results of Examples 4 to 7, Comparative Example 11 and Comparative Example 12, the mass concentration of the tertiary aliphatic amine compound having an ether group contained in the absorbent is in the range of 1 to 24%, and the absorbent has high performance. It can be confirmed from the value of C value and carbon dioxide absorption heat.

From the results of Comparative Examples 1 to 10, a conventional carbon dioxide absorbent comprising an aqueous solution of an amine compound decreases the amount of carbon dioxide recovered by increasing the total mass concentration of the amine compound to 55% or more, or 60% or more. Increase in C value due to is confirmed.

From the results of Examples 1 to 11, Comparative Example 11 and Comparative Example 12, when the concentration of the absorbent was increased by including a tertiary aliphatic amine compound having an ether group, the total mass of the amine compound contained in the absorbent It can be confirmed from the C value and the value of heat of carbon dioxide absorption that the absorbent exhibits high performance in a range where the concentration is higher than 60% and lower than 85%.

From the results of Comparative Example 13, the values of C value and carbon dioxide absorption heat are higher than those of Example 12, respectively.

From the results of Comparative Example 14, the C value and the carbon dioxide absorption heat value are higher than those of Example 13, respectively.

Claims

An absorbent for separating and recovering carbon dioxide from a gas containing carbon dioxide,
At least one alkanolamine compound represented by the general formula [1],
A total of at least one tertiary aliphatic amine compound having an ether group represented by the general formula [2] and water, and the total mass concentration of the amine compounds contained in the absorbent is 61 to 84%. Absorbent.
General formula [1]:

(Wherein R 1 represents an alkyl group having 1 to 5 carbon atoms or a hydrogen group, R 2 and R 3 each independently represents an alkyl group having 1 or 2 carbon atoms or a hydrogen group, and n is 2 or 3)
General formula [2]:

(Wherein R 4 and R 5 each independently represents a tertiary alkylamino group having 2 to 4 carbon atoms, and m represents 1, 2 or 3).
The mass concentration of the alkanolamine compound is 37 to 83%, the mass concentration of the tertiary aliphatic amine compound having an ether group is 1 to 24%, and the mass concentration of water is 16 to 39%. 2. Absorbent according to claim 1, characterized in.
The total mass concentration of the amine compound contained in the absorbent is 65 to 80%, the mass concentration of the alkanolamine compound is 45 to 75%, and the mass concentration of the tertiary aliphatic amine compound having an ether group The absorbent according to claim 1, characterized in that is 5 to 20% and the mass concentration of water is 20 to 35%.
The alkanolamine compound is monoethanolamine, 2-amino-2-methyl-1-propanol, 2- (methylamino) ethanol, 2- (ethylamino) ethanol, 2- (isopropylamino) ethanol and 3- (isopropyl The absorbent according to any one of claims 1 to 3, which is at least one selected from the group consisting of amino) propanol.
The alkanolamine compound is at least one selected from the group consisting of 2-amino-2-methyl-1-propanol, 2- (ethylamino) ethanol, 2- (isopropylamino) ethanol and 3- (isopropylamino) propanol. The absorbent according to any one of claims 1 to 3, which is a seed.
The tertiary aliphatic amine compound having an ether group is at least one selected from the group consisting of tertiary aliphatic amines having an ether group, molecular symmetry, and no hydroxy group. The absorbent according to any one of 1 to 5.
6. The tertiary aliphatic amine compound having an ether group is at least one selected from the group consisting of bis (2-dimethylaminoethyl) ether and bis (2-morpholinoethyl) ether. The absorbent according to any one of the above.
A method for separating and recovering carbon dioxide from a gas containing carbon dioxide, including the following steps A and B:
A process A for obtaining an absorbent that absorbs carbon dioxide from a gas containing carbon dioxide by contacting the absorbent according to any one of claims 1 to 7 with a gas containing carbon dioxide, and
A process B in which the absorbent obtained by absorbing the carbon dioxide obtained in the step A is heated to desorb and dissipate the carbon dioxide from the absorbent, and the diffused carbon dioxide is recovered.
9. The method for separating and recovering carbon dioxide from a gas containing carbon dioxide according to claim 8, wherein the step A is performed at a temperature of 25 to 60 ° C., and the step B is performed at a temperature of 70 to 150 ° C. .
The said process A is performed under the pressure of 1.0 bar or more, and the said process B is isolate | separated and collect | recovered from the gas containing a carbon dioxide of Claim 8 or 9 performed under the pressure of 3.5 bar or less. how to.