JP7739746B2 - Amine composition for carbon dioxide separation - Google Patents

Description

The present invention relates to a carbon dioxide separation composition for separating carbon dioxide from a carbon dioxide-containing mixed gas.

The present invention relates to, for example, a carbon dioxide separation composition for removing and capturing _CO2 from synthesis gas.

Synthetic gas, which is primarily composed of hydrogen and carbon monoxide, is used as a raw material for producing useful intermediate raw materials for the chemical industry, such as methanol and oxoalcohols.

The synthesis gas can be produced, for example, by introducing raw hydrocarbons, steam, and carbon dioxide gas into a nickel-based catalyst and reacting them under a high temperature of about 800 to 900°C and a high pressure of about 20 to 30 atm. A reformed gas containing _H2 , CO, _CO2 , _H2O , and _CH4 as its main components is obtained as a reaction product, and the reformed gas from which _CO2 and _H2O have been removed is used as synthesis gas. The removed _CO2 is reused as a raw material for producing synthesis gas.

Cited Document 2 discloses the use of a scrubbing device using methyldiethanolamine as a method for removing _CO2 from crude synthesis gas (reformed gas). Furthermore, by treating the synthesis gas from which _CO2 has been removed in a cryogenic separation device, carbon monoxide, which is an important basic raw material for heavy chemical industries, can be isolated and purified.

Japanese Patent Application Publication No. 11-132651 Special Publication No. 2008-528423

Regarding _CO2 removal using the above-mentioned methyldiethanolamine, the absorption rate of carbon dioxide at low concentrations is low, i.e., the ability to completely remove carbon dioxide is insufficient. As a result, trace amounts of _CO2 were observed to flow into the cryogenic separation device. Such trace amounts of _CO2 condense inside the cold box of the cryogenic separation device, leading to the problem of clogging the equipment and gas flow paths (for example, Patent Document 1).

The present invention was made in consideration of the above-mentioned problems, and its purpose is to provide a carbon dioxide separation composition that has a superior ability to remove carbon dioxide (faster carbon dioxide absorption rate at low concentrations) than known compositions.

As a result of extensive research to solve the above problems, the inventors discovered the composition described below and completed the present invention.

That is, the present invention relates to a composition for carbon dioxide separation as shown below.

[1] A composition for carbon dioxide separation, comprising an amine compound represented by the following general formula (1) (hereinafter referred to as "amine compound (1)") and an amine compound represented by the following general formula (2) (hereinafter referred to as "amine compound (2)"):

[In the above general formula (1), R ¹⁰ , R ¹¹ , R ¹² , R ¹³ and R ¹⁴ each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a hydroxyl group, a hydroxymethyl group, a 2-hydroxyethyl group, or an alkoxy group having 1 to 4 carbon atoms.
a and b each independently represent 0 or 1, and satisfy the relationship a+b=1.
R ¹⁵ represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a methoxymethyl group, a methoxyethoxymethyl group, or a 2-hydroxyethyl group.]

[In the above general formula (2), R ⁴ and R ⁵ each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a hydroxymethyl group, a 2-hydroxyethyl group, an aminoalkyl group having 3 to 4 carbon atoms, or a hydroxyalkyl group having 3 to 4 carbon atoms.
^R4 and ^R5 may be bonded to each other to form a ring.
^R6 represents an alkylene group having 1 to 4 carbon atoms.
[2] The amine compound (1) is represented by the following formula:

The carbon dioxide separation composition described in [1] is characterized in that it is 1,4-diazabicyclo[2.2.2]octane-2-methanol represented by the formula:

[3] The above amine compound (2) is represented by the following formula:

The carbon dioxide separation composition according to [1] or [2], characterized in that it is a piperazine represented by the formula:

[4] The carbon dioxide separation composition according to any one of [1] to [3] above, characterized in that the composition ratio of the amine compound (1) to the amine compound (2) is 5 to 100 parts by weight of the amine compound (2) per 100 parts by weight of the amine compound (1).

[5] The carbon dioxide separation composition according to any one of [1] to [4] above, further comprising, in addition to the amine compound (1) and the amine compound (2), at least one amine compound (3) selected from the group consisting of alkanolamines, propylenediamines, piperazines, piperidines, morpholines, pyrrolidines, azepanes, and polyethylenepolyamines (excluding amine compounds (1) and (2)).

[6] A carbon dioxide separation composition according to any one of [1] to [5] above, further comprising water, wherein the concentration of the water is 30 to 95% by weight of the entire carbon dioxide separation composition containing water.

[7] A method for separating carbon dioxide, comprising the step of contacting a gas containing carbon dioxide with the carbon dioxide separation composition described in any one of [1] to [6] above, thereby absorbing the carbon dioxide in the mixed gas.

The carbon dioxide separation composition of the present invention has a higher carbon dioxide absorption rate per unit time than conventionally known materials, and is effective in absorbing and separating even low concentrations of carbon dioxide at high speed with a small amount of carbon dioxide separation composition. Therefore, the present invention is extremely useful industrially, particularly when a subsequent cryogenic separation process is involved, in that it can more effectively remove impurities that may freeze.

The present invention is described in detail below.

First, we will explain the carbon dioxide separation composition of the present invention.

The carbon dioxide separation composition of the present invention is characterized by containing the above-mentioned amine compound (1) and the above-mentioned amine compound (2). More specifically, for example, a more preferable carbon dioxide separation composition can be prepared by dissolving a mixture of the above-mentioned amine compound (1) and amine compound (2) in a solvent such as water.

In the present invention, the above-mentioned amine compounds (1) and (2) both play a role in absorbing and releasing carbon dioxide.

In the present invention, R ¹⁰ , R ¹¹ , R ¹² , R ¹³ , and R ¹⁴ in the above amine compound (1) each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a hydroxyl group, a hydroxymethyl group, a 2-hydroxyethyl group, or an alkoxy group having 1 to 4 carbon atoms.

In the present invention, R ¹⁰ , R ¹¹ , R ¹² , R ¹³ , and R ¹⁴ in the above general formula (1) are not particularly limited as long as they fall within the definitions above, but examples of groups that can be independently selected include a hydrogen atom, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, a butyl group (more specifically, an n-butyl group, an isobutyl group, a sec-butyl group, or a tert-butyl group), a hydroxyl group, a hydroxymethyl group, a 2-hydroxyethyl group, a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, an n-butoxy group, or a sec-butoxy group. Of these, in terms of excellent carbon dioxide diffusion efficiency, preferably, they are independently selected from a hydrogen atom, a methyl group, an ethyl group, a butyl group, a hydroxymethyl group, or a methoxy group, and more preferably a hydrogen atom.

In the present invention, R ¹⁵ in the above amine compound (1) represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a methoxymethyl group, a methoxyethoxymethyl group, or a 2-hydroxyethyl group.

Furthermore, R ¹⁵ in the above amine compound (1) is not particularly limited as long as it satisfies the above definition, but examples thereof include a hydrogen atom, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, a butyl group (more specifically, an n-butyl group, an isobutyl group, a sec-butyl group, or a tert-butyl group), a methoxymethyl group, a methoxyethoxymethyl group, or a 2-hydroxyethyl group. Among these, in terms of excellent carbon dioxide diffusion efficiency, a hydrogen atom, a methyl group, an ethyl group, a butyl group, a methoxymethyl group, a methoxyethoxymethyl group, or a 2-hydroxyethyl group is preferred, and a hydrogen atom is more preferred.

In the above amine compound (1), a and b are each independently 0 or 1, and satisfy the relationship a + b = 1.

When a = 1 and b = 0, the above general formula (1) is represented by the following general formula (1a) (hereinafter referred to as "amine compound (1a)").

[In the above general formula (1a), the definitions and preferred ranges of R ¹⁰ , R ¹¹ , R ¹² , R ¹³ , R ¹⁴ , and R ¹⁵ are the same as the definitions and preferred ranges of R ¹⁰ , R ¹¹ , R ¹² , R ¹³ , R ¹⁴ , and R ¹⁵ shown in the above general formula (1)]
When a=0 and b=1, the above general formula (1) is represented by the following general formula (1b) (hereinafter referred to as "amine compound (1b)").

[In the above general formula (1b), the definitions and preferred ranges of R ¹⁰ , R ¹¹ , R ¹² , R ¹³ , R ¹⁴ , and R ¹⁵ are the same as the definitions and preferred ranges of R ¹⁰ , R ¹¹ , R ¹² , R ¹³ , R ¹⁴ , and R ¹⁵ shown in the above general formula (1)]
Specific examples of the amine compound (1) include the following compounds (exemplary compounds 1 to 28), but the present invention is not limited to these.

From the viewpoint of availability, the above amine compound (1) is preferably 1,4-diazabicyclo[2.2.2]octane-2-methanol (R ¹⁰ =R ¹¹ =R ¹² =R ¹³ =R ¹⁴ =R ¹⁵ =hydrogen atoms, a=0, b=1, the above exemplary compound 1). That is, an amine compound represented by the following chemical structural formula is preferred.

In the amine compound (2) of the present invention, ^R4 and ^R5 each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a hydroxymethyl group, a 2-hydroxyethyl group, an aminoalkyl group having 3 to 4 carbon atoms, or a hydroxyalkyl group having 3 to 4 carbon atoms. ^R4 and ^R5 may be bonded to each other to form a ring. ^R6 represents an alkylene group having 1 to 4 carbon atoms.

In terms of excellent carbon dioxide adsorption/desorption efficiency, ^R4 and ^R5 in the amine compound (2) are preferably each independently a hydrogen atom, a methyl group, an ethyl group, a 2-hydroxyethyl group, a 2-hydroxypropyl group, or a 3-aminopropyl group, more preferably ^R4 and ^R5 are bonded to each other to form a ring, and even more preferably ^R4 and ^R5 are methyl groups that are bonded to each other to form 1,2-ethylene.

^R6 in the amine compound (2) represents an alkylene group having 1 to 4 carbon atoms, and is not particularly limited. Examples include a methylene group, a 1,2-ethylene group, a 1,3-propylene group, and a 1,4-butylene group. In terms of excellent carbon dioxide adsorption/desorption efficiency, 1,2-ethylene or 1,3-propylene is preferred, and 1,2-ethylene is more preferred.

In the above amine compound (2), the ring formed by ^R4 and ^R5 bonding to each other is not particularly limited, but an amine compound represented by the following general formula (2a) is preferred in terms of excellent carbon dioxide absorption efficiency.

[In the above general formula (2a), each R ⁷ independently represents an alkylene group having 1 to 4 carbon atoms.]
The definition and preferred range of R ⁷ (alkylene having 1 to 4 carbon atoms) in general formula (2a) are the same as the definition and preferred range of R ⁶ (alkylene having 1 to 4 carbon atoms) shown in general formula (2).

Specific examples of amine compounds represented by general formula (2) include, for example, N,N'-dimethyl-1,4-diaminobutane, N-methyl-1,4-diaminobutane, N,N'-dimethyl-1,3-diaminopropane, N-methyl-1,3-diaminopropane, N,N'-dimethyl-1,2-diaminopropane, N-methyl-1,2-diaminopropane, N,N'-dimethyl-1,2-diaminoethane, N-methyl-1,2-diaminoethane, N,N'-diethyl-1,4-diaminobutane, N-ethyl-1,4-diaminobutane, N,N'-diethyl-1,3-diaminopropane, N-ethyl-1,3-diaminopropane, N,N'-diethyl-1,2-diaminopropane, Examples include N-ethyl-1,2-diaminopropane, N,N'-diethyl-1,2-diaminoethane, N-ethyl-1,2-diaminoethane, N,N'-dipropyl-1,4-diaminobutane, N-propyl-1,4-diaminobutane, N,N'-dipropyl-1,3-diaminopropane, N-propyl-1,3-diaminopropane, N,N'-dipropyl-1,2-diaminopropane, N-propyl-1,2-diaminopropane, N,N'-dipropyl-1,2-diaminoethane, N-propyl-1,2-diaminoethane, piperazine, N-(2-aminoethyl)-2-aminoethanol, and 2-(3-aminopropyl)-2-aminoethanol.

From the viewpoint of availability, the above-mentioned amine compound (2) is preferably at least one amine selected from the group consisting of N,N'-dimethyl-1,3-diaminopropane (R ⁴ =R ⁵ =methyl group, R ⁶ =1,3-propylene), N,N'-dimethyl-1,2-diaminoethane (R ⁴ =R ⁵ =methyl group, R ⁶ =1,2-ethylene), piperazine, N-(2-aminoethyl)-2-aminoethanol, and 2-(3-aminopropyl)-2-aminoethanol.

The carbon dioxide separation composition of the present invention, which is characterized by containing the above-mentioned amine compound (1) and the above-mentioned amine compound (2), is preferably a carbon dioxide separation composition characterized by containing amine compound (1) which is 1,4-diazabicyclo[2.2.2]octane-2-methanol and at least one amine compound (2) selected from the group consisting of piperazine, N,N'-dimethyl-1,3-diaminopropane, N,N'-dimethyl-1,2-diaminoethane, N-(2-aminoethyl)-2-aminoethanol, and 2-(3-aminopropyl)-2-aminoethanol, in terms of its excellent carbon dioxide absorption rate.

In terms of achieving a fast carbon dioxide absorption rate, the composition ratio of amine compound (1) to amine compound (2) for the carbon dioxide separation composition of the present invention is preferably 5 to 100 parts by weight of amine compound (2) per 100 parts by weight of amine compound (1), more preferably 10 to 70 parts by weight of amine compound (2) per 100 parts by weight of amine compound (1), and even more preferably 20 to 40 parts by weight of amine compound (2) per 100 parts by weight of amine compound (1).

In the present invention, the amine compounds represented by the above general formulas (1) and (2) may be commercially available or may be synthesized by known methods, and are not particularly limited. Furthermore, the purity of these amine compounds is not particularly limited, but is preferably 95% or higher, and more preferably 99% or higher. If the purity is below 95%, there is a risk that the amount of carbon dioxide absorbed will decrease.

The carbon dioxide separation composition of the present invention may contain, in addition to amine compound (1) and amine compound (2), at least one amine compound (3) different from these selected from the group consisting of alkanolamines, propylenediamines, piperazines, piperidines, morpholines, pyrrolidines, azepanes, and polyethylenepolyamines. The coexistence of amine compound (3) may increase the N atom content per unit weight of the carbon dioxide separation composition, which may be industrially advantageous in that it increases the amount of carbon dioxide absorbed per unit weight of the carbon dioxide separation composition.

In the present invention, specific examples of the alkanolamines include ethanolamine, N-methylethanolamine, N,N-dimethylethanolamine, diethanolamine, N-[2-(dimethylamino)ethyl]-N-methylethanolamine, N-[2-(diethylamino)ethyl]-N-ethylethanolamine, 2-(2-aminoethoxy)ethanol, 2-[2-(dimethylamino)ethoxy]ethanol, 2-[2-(diethylamino)ethoxy]ethanol, N-[2-(2-aminoethoxy)ethyl]ethanolamine, N-[2-{2-(dimethylamino)ethoxy}ethyl]-N-methylethanolamine, or N-[2-{2-(diethylamino)ethoxy}ethyl],N-ethylethanolamine. Of these, from the standpoint of availability and production costs, it is preferable that the alkanolamine be at least one selected from the group consisting of ethanolamine, N-(2-aminoethyl)ethanolamine, and 2-(2-aminoethoxy)ethanol.

In the present invention, specific examples of the propylene diamines include 1,3-bis(dimethylamino)propane and 1,3-bis(diethylamino)propane.

In the present invention, specific examples of the piperazines include 1-(2-hydroxyethyl)-4-methylpiperazine, 1-(2,3-dihydroxypropyl)-4-methylpiperazine, 1-(2,3-dihydroxypropyl)-4-ethylpiperazine, 1-(2,3-dihydroxypropyl)-4-propylpiperazine, 1-(2,3-dihydroxypropyl)-4-butylpiperazine, 1-(2-hydroxy-3-methoxypropyl)-4-methylpiperazine, 1-(2-hydroxy-3-methoxypropyl)-4-methylpiperazine, 1-(2,3-dimethoxypropyl)-4-ethylpiperazine, 1-(2-hydroxy-3-methoxypropyl)-4-propylpiperazine, 1-(2-hydroxy-3-methoxypropyl)-4-butylpiperazine, 1-(2,3-dimethoxypropyl)-4-methylpiperazine, 1-(2,3-dimethoxypropyl)-4-ethylpiperazine, 1-(2,3-dimethoxypropyl)-4-propylpiperazine, 1-(2,3-dimethoxypropyl)-4-butylpiperazine, or 1,4-diazabicyclo[2.2.2]octane.

In the present invention, specific examples of the piperidines include piperidine, 2-methylpiperidine, 1-(2,3-dihydroxypropyl)-piperidine, 1-(2,3-dihydroxypropyl)-4-methylpiperidine, 1-(2,3-dihydroxypropyl)-4-ethylpiperidine, 1-(2,3-dihydroxypropyl)-4-propylpiperidine, 1-(2,3-dihydroxypropyl)-4-butylpiperidine, 1-(2-hydroxy-3-methoxypropyl)-piperidine, and 1-(2-hydroxy-3-methoxypropyl)-4-methylpiperidine. Examples include lysine, 1-(2-hydroxy-3-methoxypropyl)-4-ethylpiperidine, 1-(2-hydroxy-3-methoxypropyl)-4-propylpiperidine, 1-(2-hydroxy-3-methoxypropyl)-4-butylpiperidine, 1-(2,3-dimethoxypropyl)-piperidine, 1-(2,3-dimethoxypropyl)-4-methylpiperidine, 1-(2,3-dimethoxypropyl)-4-ethylpiperidine, 1-(2,3-dimethoxypropyl)-4-propylpiperidine, and 1-(2,3-dimethoxypropyl)-4-butylpiperidine.

In the present invention, specific examples of the morpholines include morpholine, 2-methylmorpholine, 2,6-dimethylmorpholine, 1-(2,3-dihydroxypropyl)-morpholine, 1-(2-hydroxy-3-methoxypropyl)-morpholine, and 1-(2,3-dimethoxypropyl)-morpholine.

Specific examples of pyrrolidines in the present invention include pyrrolidine, 2-methylpyrrolidine, 2,5-dimethylpyrrolidine, 1-(2,3-dihydroxypropyl)-pyrrolidine, 1-(2-hydroxy-3-methoxypropyl)-pyrrolidine, 1-(2,3-dimethoxypropyl)-pyrrolidine, and 1,5-diazabicyclo[4.3.0]-5-nonene.

In the present invention, specific examples of the azepanes include azepane, 2-methylazepane, 2,7-dimethylazepane, and 1,8-diazabicyclo[5.4.0]-7-undecene.

In the present invention, specific examples of the polyethylene polyamines include diethylenetriamine (DETA), triethylenetetramine (TETA), tetraethylenepentamine (TEPA), pentaethylenehexamine (PEHA), hexaethyleneheptamine (HEHA), and polyethylene polyamines having eight or more amino groups.

Here, the aforementioned "TETA" refers to a compound in which four amino groups are connected in a linear or branched fashion via an ethylene chain, but in the present invention, it also includes compounds that similarly have four amino groups and a piperazine ring structure. Specific examples of TETA compounds include 1,4,7,10-tetraazadecane, N,N-bis(2-aminoethyl)-1,2-ethanediamine, 1-[2-[(2-aminoethyl)amino]ethyl]-piperazine, and 1,4-bis(2-aminoethyl)-piperazine.

The aforementioned "TEPA" refers to a compound in which five amino groups are connected in a linear or branched fashion via an ethylene chain, but in the present invention, it also includes compounds that also have five amino groups and a piperazine ring structure. Specific examples of TEPA compounds include 1,4,7,10,13-pentaazatridecane, N,N,N'-tris(2-aminoethyl)-1,2-ethanediamine, 1-[2-[2-[2-[(2-aminoethyl)amino]ethyl]amino]ethyl]-piperazine, 1-[2-[bis(2-aminoethyl)amino]ethyl]-piperazine, and bis[2-(1-piperazinyl)ethyl]amine.

Furthermore, the above-mentioned "PEHA" refers to a compound in which six amino groups are connected in a linear or branched manner via an ethylene chain, but in the present invention, it also includes compounds that also have six amino groups and a piperazine ring structure. Specific examples of PEHA compounds include 1,4,7,10,13,16-hexaazahexadecane, N,N,N',N'-tetrakis(2-aminoethyl)-1,2-ethanediamine, N,N-bis(2-aminoethyl)-N'-[2-[(2-aminoethyl)amino]ethyl]-1,2-ethanediamine, 1-[2-[2-[2-[2-[(2-aminoethyl)amino]ethyl]amino]ethyl]amino]ethyl]-piperazine, 1-[2-[2-[2-[bis(2-aminoethyl)amino]ethyl]amino]ethyl]-piperazine, and N,N'-bis[2-(1-piperazinyl)ethyl]-1,2-ethanediamine, etc.

The aforementioned "HEHA" refers to a compound in which seven amino groups are connected in a linear or branched fashion via an ethylene chain, but in the present invention, it also includes compounds that similarly have seven amino groups and a piperazine ring structure. Specific examples of HEHA compounds include 1,4,7,10,13,16,19-heptaazanonadecane, N-[2-[(2-aminoethyl)amino]ethyl]-N,N',N'-tris(2-aminoethyl)-1,2-ethanediamine, 1-[2-[2-[2-[2-[2-[2-[(2-aminoethyl)amino]ethyl]amino]ethyl]amino]ethyl]-piperazine, and N-(2-aminoethyl)-N,N'-bis[2-(1-piperazinyl)ethyl]-1,2-ethanediamine, etc.

The aforementioned "polyethylene polyamine having eight or more amino groups" refers to a compound in which eight or more amino groups are connected in a linear or branched manner via an ethylene chain, but in the present invention, it also includes compounds that similarly have eight or more amino groups and also have a piperazine ring structure. Specific examples of polyethylene polyamines having eight or more amino groups include those under the trade name "Poly8" (manufactured by Tosoh Corporation) and polyethyleneimine.

Among these, from the viewpoint of availability and acquisition cost, the polyethylene polyamines include diethylenetriamine (DETA),
triethylenetetramine (TETA), which consists of a mixture of 1,4,7,10-tetraazadecane, N,N-bis(2-aminoethyl)-1,2-ethanediamine, 1-[2-[(2-aminoethyl)amino]ethyl]-piperazine, and 1,4-bis(2-aminoethyl)-piperazine;
tetraethylenepentamine (TEPA) consisting of a mixture of 1,4,7,10,13-pentaazatridecane, N,N,N'-tris(2-aminoethyl)-1,2-ethanediamine, 1-[2-[2-[2-[(2-aminoethyl)amino]ethyl]amino]ethyl]-piperazine, 1-[2-[bis(2-aminoethyl)amino]ethyl]-piperazine, and bis[2-(1-piperazinyl)ethyl]amine;
pentaethylenehexamine (PEHA) consisting of a mixture of 1,4,7,10,13,16-hexaazahexadecane, N,N,N',N'-tetrakis(2-aminoethyl)-1,2-ethanediamine, N,N-bis(2-aminoethyl)-N'-[2-[(2-aminoethyl)amino]ethyl]-1,2-ethanediamine, 1-[2-[2-[2-[2-[(2-aminoethyl)amino]ethyl]amino]ethyl]amino]ethyl]-piperazine, 1-[2-[2-[2-[bis(2-aminoethyl)amino]ethyl]amino]ethyl]piperazine, and N,N'-bis[2-(1-piperazinyl)ethyl]-1,2-ethanediamine;
Hexaethyleneheptamine (HEHA) consisting of a mixture of 1,4,7,10,13,16,19-heptaazanonadecane, N-[2-[(2-aminoethyl)amino]ethyl]-N,N',N'-tris(2-aminoethyl)-1,2-ethanediamine, 1-[2-[2-[2-[2-[2-[2-[(2-aminoethyl)amino]ethyl]amino]ethyl]amino]ethyl]-piperazine, and N-(2-aminoethyl)-N,N'-bis[2-(1-piperazinyl)ethyl]-1,2-ethanediamine, and a polyethylene polyamine having eight or more amino groups under the trade name "Poly8" (manufactured by Tosoh Corporation).
It is preferable that the polymer is at least one selected from the group consisting of:

In the present invention, amine compound (3) may be a commercially available product or may be synthesized by a known method, and is not particularly limited. Furthermore, the purity of amine compound (3) is not particularly limited, but is preferably 95% or higher, and particularly preferably 99% or higher. If the purity is below 95%, there is a risk that the amount of carbon dioxide absorbed will decrease.

In the present invention, when the carbon dioxide separation composition contains amine compound (3), the weight of amine compound (3) relative to the total weight of amine compounds (1) and (2) and amine compound (3) is not particularly limited, but from the perspective of increasing the amount of carbon dioxide absorbed per unit weight, it is preferably 50% by weight or less, more preferably 30% by weight or less, and even more preferably 20% by weight or less.

The carbon dioxide separation composition of the present invention can be used as is for its intended purpose, but from the perspective of operability, it can also be used as a composition further containing a solvent. The solvent used in the carbon dioxide separation composition is not particularly limited, but examples include water, alcohol compounds, and polyol compounds (e.g., ethylene glycol, glycerin, and polyethylene glycol, but are not particularly limited), and mixtures of these may also be used. Of these, water is preferred because it is highly efficient in absorbing and separating carbon dioxide gas as bicarbonate, is excellent in suppressing increases in the viscosity of absorbents and separating agents and the generation of solids, and does not significantly increase the energy emitted by carbon dioxide.

When using the above-mentioned solvent (e.g., water), the concentration of the solvent is preferably 30 to 95% by weight, and more preferably 50 to 80% by weight, based on the total weight of the carbon dioxide separation composition including the solvent, in order to ensure excellent operability of the carbon dioxide separation composition of the present invention.

Next, we will explain the carbon dioxide separation method of the present invention.

The carbon dioxide separation method of the present invention is characterized by comprising a step of contacting a carbon dioxide-containing gas with the carbon dioxide separation composition of the present invention and allowing the carbon dioxide to be highly selectively absorbed into the carbon dioxide separation composition. After the carbon dioxide has been absorbed in this manner, the method may also include a step of heating and/or reducing the pressure of the carbon dioxide separation composition to release the absorbed carbon dioxide.

In the carbon dioxide separation method of the present invention, there are no particular limitations on the method for contacting a carbon dioxide-containing gas with the carbon dioxide separation composition of the present invention, and any known method can be used. Known methods include the bubbling method and the head-on contact method using a packed column or a plate column.

In the carbon dioxide separation method of the present invention, the temperature at which a carbon dioxide-containing gas is absorbed into the carbon dioxide separation composition of the present invention is not particularly limited, but is typically in the range of 10°C to 60°C.

Furthermore, the carbon dioxide separation composition of the present invention can be used in the chemical absorption of carbon dioxide as a carbon dioxide absorption and desorption agent by supporting or impregnating it on any carrier.

The chemical absorption method involves contacting the carbon dioxide separation composition with a gas containing carbon dioxide to absorb the carbon dioxide, and then dissipating the absorbed carbon dioxide by increasing the temperature or reducing the pressure. In this chemical absorption method, the temperature at which carbon dioxide is dissipated is generally 100°C or higher, but when using the carbon dioxide separation composition of the present invention, there are no particular temperature restrictions and temperatures below 100°C may also be used.

The carrier is not particularly limited, but examples that can be used include silica, alumina, magnesia, porous glass, activated carbon, polymethyl methacrylate-based porous resin, and fibers.

The silica mentioned above can be crystalline or non-crystalline (amorphous), and many types are known, including zeolite-like silica with fine pores and mesoporous silica. There are no particular restrictions on the silica that can be used in the carbon dioxide absorption/desorption agent of the present invention, and any commercially available silica can be used, but silica with a large surface area is preferred.

The carbon dioxide absorption/desorption agent using the carrier of the present invention may further contain water.

The amount of carbon dioxide separation composition supported in a carbon dioxide absorption/desorption agent using the carrier of the present invention is preferably 5 to 70% by weight, and more preferably 10 to 60% by weight, of the weight of the carrier on which the carbon dioxide separation composition is supported, in order to achieve excellent carbon dioxide absorption and ease of supporting the carbon dioxide separation composition.

The amount of water contained in the carbon dioxide absorption/desorption agent using the carrier of the present invention is preferably at least equimolar to the amount of carbon dioxide to be absorbed. An amount of water at least equimolar to the amount of carbon dioxide is preferable because the energy emitted by carbon dioxide is not too large.

The carbon dioxide absorption/desorption agent using the carrier of the present invention can be used in a carbon dioxide separation method widely known as the solid absorption method. The solid absorption method involves contacting a carbon dioxide separating agent with a gas containing carbon dioxide to absorb the carbon dioxide, and then desorbing the absorbed carbon dioxide by increasing the temperature or reducing the pressure. In the solid absorption method, the temperature at which carbon dioxide is desorbed is generally 100°C or higher, but when using the carbon dioxide separating composition of the present invention, there are no particular restrictions on the temperature, and it can be below 100°C.

The above-mentioned gas containing carbon dioxide may be pure carbon dioxide gas or a mixed gas containing carbon dioxide and other gases. The other gases mentioned above are not particularly limited, but examples include air, nitrogen, oxygen, hydrogen, argon, neon, helium, carbon monoxide, water vapor, methane, and nitrogen oxides.

There are no particular restrictions on the mixed gases that can be used in the carbon dioxide separation method of the present invention, as long as they contain carbon dioxide. However, in order to improve the separation performance between carbon dioxide and other gases, it is preferable that the carbon dioxide concentration be 0.5% or higher, and more preferably 1% or higher.

In the carbon dioxide separation method of the present invention, additional processes other than the above-mentioned processes (absorption process and desorption process) may be carried out without any problems. For example, a cooling process, heating process, washing process, extraction process, ultrasonic treatment process, distillation process, and other processes involving treatment with chemical solutions may be carried out as appropriate.

The carbon dioxide separation method of the present invention is not particularly limited, but can be applied to, for example, carbon dioxide separation in carbon monoxide production facilities that produce carbon monoxide from fossil fuels and hydrogen production facilities that produce hydrogen from coal gasification gas. It can also be applied to carbon dioxide recovery systems from combustion exhaust gases generated in thermal power plants, steel plants, cement factories, and other facilities that release gases into the atmosphere after carbon dioxide removal.

The present invention will be explained using the following examples, but the present invention should not be construed as being limited to these. The carbon dioxide concentration meter used was the RSIR-2000 manufactured by J Science Labs.

[Example 1]
30 g of 1,4-diazabicyclo[2.2.2]octane-2-methanol (manufactured by Tosoh Corporation), 10 g of piperazine (manufactured by Tokyo Chemical Industry Co., Ltd.), and 60 g of pure water were mixed and stirred to obtain a carbon dioxide separation composition (100 g). The weight ratio of amine compound (1) to amine compound (2) was 100 parts by weight/33.3 parts by weight. The water content in the carbon dioxide separation composition was 60 wt%. This was placed in a 200 mL gas absorption bottle and the temperature was adjusted to 50°C in a water bath. A mixed gas of carbon dioxide gas and nitrogen gas (carbon dioxide concentration 2.0% by volume) was blown into the carbon dioxide separation composition through the gas inlet of the gas absorption bottle at a rate of 10 mL/min. The carbon dioxide concentration of the released gas was continuously measured using a carbon dioxide concentration meter for the mixed gas released from the gas outlet. 30 minutes after the start of blowing, the carbon dioxide concentration of the released gas was 0.005% by volume. After one hour it was 0.064% by volume, and after one and a half hours it was 0.158% by volume.

[Example 2]
32.6 g of 1,4-diazabicyclo[2.2.2]octane-2-methanol (manufactured by Tosoh Corporation), 7.4 g of piperazine (manufactured by Tokyo Chemical Industry Co., Ltd.), and 60 g of pure water were mixed and stirred to obtain a carbon dioxide separation composition (100 g). The weight ratio of amine compound (1) to amine compound (2) was 100 parts by weight/22.7 parts by weight. The water content in the carbon dioxide separation composition was 60% by weight. The carbon dioxide separation composition was subjected to the same procedure as in Example 1 to measure the carbon dioxide concentration of the released gas. The carbon dioxide concentration of the released gas 30 minutes after the start of blowing was 0.003% by volume. After one hour, it was 0.048% by volume, and after one and a half hours, it was 0.166% by volume.

[Comparative Example 1]
30 g of N-methyldiethanolamine (manufactured by Tokyo Chemical Industry Co., Ltd.), 10 g of piperazine (manufactured by Tokyo Chemical Industry Co., Ltd.), and 60 g of pure water were mixed and stirred to obtain a carbon dioxide separation composition (100 g). The carbon dioxide separation composition was subjected to the same procedure as in Example 1 to measure the carbon dioxide concentration of the released gas. The carbon dioxide concentration of the released gas 30 minutes after the start of blowing was 0.031 vol%. After 1 hour, it was 0.076 vol%, and after 1.5 hours, it was 0.168 vol%.

[Comparative Example 2]
32.6 g of N-methyldiethanolamine (Tokyo Chemical Industry Co., Ltd.), 7.4 g of piperazine (Tokyo Chemical Industry Co., Ltd.), and 60 g of pure water were mixed and stirred to obtain a carbon dioxide separation composition (100 g). The carbon dioxide separation composition was subjected to the same procedure as in Example 1 to measure the carbon dioxide concentration of the released gas. The carbon dioxide concentration of the released gas 30 minutes after the start of blowing was 0.055% by volume. After 1 hour, it was 0.159% by volume, and after 1.5 hours, it was 0.333% by volume.

The results of Examples 1, 2, Comparative Examples 1, and 2 are shown in the table below.

Claims (4)

The following formula

1,4-diazabicyclo[2.2.2]octane-2-methanol (hereinafter referred to as "amine compound (1)") represented by the formula:
The following formula

and water, wherein the concentration of the water is 30 to 95% by weight of the entire composition for carbon dioxide separation containing water. The carbon dioxide separation composition according to claim 1, characterized in that the composition ratio of the amine compound (1) to the amine compound (2) is 5 to 100 parts by weight of the amine compound (2) per 100 parts by weight of the amine compound (1). The carbon dioxide separation composition according to claim 1 or 2, further comprising, in addition to the amine compound (1) and the amine compound (2), at least one amine compound (3) selected from the group consisting of alkanolamines, propylenediamines, piperazines, piperidines, morpholines, pyrrolidines, azepanes, and polyethylenepolyamines (excluding amine compounds (1) and (2)). A method for separating carbon dioxide, comprising the step of contacting a gas containing carbon dioxide with the carbon dioxide separation composition according to any one of claims 1 to 3 to absorb the carbon dioxide in the gas containing carbon dioxide.