Carbon dioxide separation and recovery solution

Abstract

To solve the problem in which, for conventionally known aqueous amine solutions, a large amount of energy is required at the time of carbon dioxide recovery, and therefore, there has been a demand for a composition solution that reduces the energy required for recovery.SOLUTION: A carbon dioxide separation composition is an aqueous solution containing at least one amide compound represented by general formula (1). Based on the total amount of the carbon dioxide separation composition being 100 mass%, the content of the amide compound is 0.1 to 50 mass%.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a carbon dioxide separation composition for separating carbon dioxide from a carbon dioxide-containing mixed gas, and uses thereof. [Background technology]

[0002] In recent years, due to the issue of global warming, carbon dioxide separation and capture has attracted attention, and the development of carbon dioxide absorbents has been actively pursued. Carbon dioxide separation methods are classified into chemical absorption and physical absorption, with the advantage that the captured carbon dioxide can be obtained with high purity.

[0003] Aqueous solutions of amines are commonly known as carbon dioxide separation compounds for chemical absorption (Patent Documents 1 and 2). This chemical absorption method involves absorbing carbon dioxide at a low temperature, then heating it to a high temperature to desorb and recover the carbon dioxide. However, because the aqueous solution is heated to reach a high temperature, the high latent heat and specific heat of water affect the method, requiring a large amount of energy to recover the carbon dioxide, which is an issue. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] U.S. Patent No. 4,112,052 [Patent Document 2] Patent No. 2871334 Summary of the Invention [Problem to be solved by the invention]

[0005] Conventionally known aqueous amine solutions require a large amount of energy when recovering carbon dioxide, and therefore a liquid composition that reduces the energy required for recovery has been desired. [Means for solving the problem]

[0006] The present inventors have conducted extensive research to solve the above problems, and as a result have completed the present invention described below.

[0007] That is, the present invention relates to a carbon dioxide separation composition and uses thereof as described below.

[0008] [1] A composition for carbon dioxide separation that is an aqueous solution containing at least one amide compound represented by general formula (1), wherein the content of the amide compound is 0.1 to 50 mass % relative to the total mass of the composition for carbon dioxide separation, taken as 100 mass %.

[0009] [ka]

[0010] [In formula (1), R 1 R represents an alkyl group having an amide group, represented by the following general formula (2): 2 represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms which may be branched, a hydroxyalkyl group having 1 to 4 carbon atoms which may be branched, and R 1 represents a group.]

[0011] [ka]

[0012] [In formula (2), R 3 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms which may be branched. X represents an alkylene group having 1 to 3 carbon atoms.] [2] The composition for carbon dioxide separation according to [1], wherein in general formula (2), X is an ethylene group.

[0013] [3] The amide compound is

[0014] [ka]

[0015] The composition for carbon dioxide separation according to [1], selected from the group consisting of: [4] The carbon dioxide separation composition according to [1], wherein the carbon dioxide separation composition further contains an amine compound, and the content of the at least one amine compound is 2 to 70 mass%, with the total amount of the carbon dioxide separation composition being 100 mass%.

[0016] [5] A method for separating carbon dioxide, comprising the steps of contacting a mixed gas containing carbon dioxide with the carbon dioxide separation composition according to any one of [1] to [4], and allowing the carbon dioxide in the mixed gas to be absorbed by the carbon dioxide separation composition.

[0017] [6] A method for separating carbon dioxide, comprising the steps of: bringing a mixed gas containing carbon dioxide into contact with the carbon dioxide separation composition according to any one of [1] to [4], and causing the carbon dioxide in the mixed gas to be absorbed into the carbon dioxide separation composition; and heating and / or depressurizing the carbon dioxide separation composition that has absorbed the carbon dioxide, thereby releasing the carbon dioxide. [Effects of the Invention]

[0018] The carbon dioxide separation composition of the present invention is characterized by a faster carbon dioxide emission rate per unit mass and excellent carbon dioxide emission performance compared to conventionally known materials, and has the effect of being able to absorb and separate large amounts of carbon dioxide. Therefore, the present invention is extremely useful industrially in that it can efficiently separate carbon dioxide from exhaust gases emitted in large quantities from large-scale thermal power plants and the like, thereby improving the efficiency of the entire carbon dioxide separation and capture process. DETAILED DESCRIPTION OF THE INVENTION

[0019] The present invention will be described in detail below.

[0020] First, the carbon dioxide separation composition of the present invention will be described.

[0021] The carbon dioxide separation composition of the present invention is an aqueous solution containing at least one amide compound selected from the group consisting of amine compounds represented by the following general formula (1), in which the content of the amide compound is 0.1 to 50 mass% relative to the total mass of the carbon dioxide separation composition, taken as 100 mass%:

[0022] [ka]

[0023] [In formula (1), R 1 R represents an alkyl group having an amide group, represented by the following general formula (2): 2 represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms which may be branched, a hydroxyalkyl group having 1 to 4 carbon atoms which may be branched, and R 1 represents a group.]

[0024] [ka]

[0025] [In formula (2), R 3 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms which may be branched. X represents an alkylene group having 1 to 3 carbon atoms.] In the present invention, at least one amide compound selected from the group consisting of the amide compounds represented by the above general formulas (1) and (2) plays a role in adsorbing and releasing carbon dioxide.

[0026] In the above general formula (1), R 1 represents an alkyl group having an amide group represented by the above general formula (2), and R 2 represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms which may be branched, a hydroxyalkyl group having 1 to 4 carbon atoms which may be branched, and R 1 Represents a group.

[0027] In the above general formula (2), R 3 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms which may be branched, and each X independently represents an alkylene group having 1 to 3 carbon atoms.

[0028] In the above general formula (2), R 3 is not particularly limited as long as it satisfies the above definition, and examples thereof include a hydrogen atom, a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a sec-butyl group, and a tert-butyl group.

[0029] In the above general formula (2), X is not particularly limited as long as it satisfies the above definition, and examples thereof include a methylene group, an ethylene group, and a propylene group.

[0030] In the above general formula (1), R 1 is not particularly limited as long as it satisfies the above definition, and examples thereof include an N-formylaminomethyl group, an N-acetylaminomethyl group, an N-propylaminomethyl group, an N-butylaminomethyl group, a 2-(N-formylamino)ethyl group, a 2-(N-acetylamino)ethyl group, a 2-(N-propionylamino)ethyl group, a 2-(N-butanoylamino)ethyl group, a 3-(N-formylamino)propyl group, a 3-(N-acetylamino)propyl group, a 3-(N-propionylamino)propyl group, and a 3-(N-butanoylamino)propyl group, of which the 2-(N-formylamino)ethyl group, the 2-(N-acetylamino)ethyl group, the 2-(N-propionylamino)ethyl group, and the 2-(N-butanoylamino)ethyl group are more preferred in terms of ease of availability.

[0031] In the above general formula (1), R 2is sufficient as long as it satisfies the above definition, and is not particularly limited, and examples thereof include a hydrogen atom, a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a sec-butyl group, a tert-butyl group, a hydroxymethyl group, a 1-hydroxyethyl group, a 2-hydroxyethyl group, a 1-hydroxypropyl group, a 2-hydroxypropyl group, a 3-hydroxypropyl group, a 1-hydroxyisopropyl group, a 2-hydroxyisopropyl group, a 1-hydroxybutyl group, a 2-hydroxybutyl group, a 3-hydroxybutyl group, a 4-hydroxybutyl group, an N-formylaminomethyl group, an N-acetylaminomethyl group, an N-propionylaminomethyl group, an N-methyl ... Examples of such groups include an N-butanoylaminomethyl group, a 2-(N-formylamino)ethyl group, a 2-(N-acetylamino)ethyl group, a 2-(N-propionylamino)ethyl group, a 2-(N-butanoylamino)ethyl group, a 3-(N-formylamino)propyl group, a 3-(N-acetylamino)propyl group, a 3-(N-propionylamino)propyl group, and a 3-(N-butanoylamino)propyl group. In terms of availability, a hydrogen atom, a 2-(N-formylamino)ethyl group, a 2-(N-acetylamino)ethyl group, a 2-(N-propionylamino)ethyl group, and a 2-(N-butanoylamino)ethyl group are more preferred.

[0032] Specific examples of the amide compound represented by the general formula (1) include, but are not limited to, the following compounds (exemplary compound numbers 1 to 19).

[0033] [ka]

[0034] As the amide compound represented by the general formula (1), the following compounds are more preferable in terms of ease of synthesis.

[0035] [ka]

[0036] In the present invention, the amide compounds used may be commercially available or may be synthesized by a known method, and are not particularly limited. The purity of these amine compounds is not particularly limited, but is preferably 95% or more, and particularly preferably 99% or more.

[0037] The content of the amide compound is preferably 0.1 to 50 mass %, and more preferably 0.2 to 30 mass %, with the entire carbon dioxide separation composition being 100 mass %.

[0038] As described above, the carbon dioxide separation composition of the present invention is characterized by containing water, and the water content is 30.0 to 99.9 mass % when the total amount of the carbon dioxide separation composition is 100 mass %.

[0039] The content of water is more preferably 60.0 to 99.9 mass % relative to 100 mass % of the entire carbon dioxide separation composition, in terms of excellent carbon dioxide diffusion performance.

[0040] Examples of the water include industrial water, tap water, ion-exchanged water, and distilled water, and any of these may be used.

[0041] The carbon dioxide separating composition of the present invention may further contain an amine compound, an antifoaming agent, an antioxidant, and the like in addition to the amide compound.

[0042] The amine compound is not particularly limited, and examples thereof include at least one amine compound selected from the group consisting of alkanolamines, propylenediamines, piperazines, piperidines, morpholines, pyrrolidines, azepanes, and polyethylenepolyamines. The coexistence of such an amine compound may increase the N atom content per unit mass of the carbon dioxide separation composition, which may be industrially advantageous in that it increases the amount of carbon dioxide absorbed per unit mass of the carbon dioxide separation composition.

[0043] 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, etc. Among these, from the viewpoints of availability and production costs, ethanolamine, N-(2-aminoethyl)ethanolamine, 2-(2-aminoethoxy)ethanol, etc. are preferred as alkanolamines.

[0044] In the present invention, specific examples of the propylenediamines include 1,3-bis(dimethylamino)propane and 1,3-bis(diethylamino)propane.

[0045] In the present invention, specific examples of the piperazines include piperazine, 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-ethylpiperazine, 1-(2-hydroxy-3 1-(2,3-dimethoxypropyl)-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, N-aminoethylpiperazine, N-hydroxyethylpiperazine, 1,4-diazabicyclo[2.2.2]octane, or 1,4-diazabicyclo[2,2,2]octane-2-methanol.

[0046] 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. 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.

[0047] 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.

[0048] In the present invention, specific examples of pyrrolidines 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.

[0049] 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 above-mentioned "TETA" refers to a compound in which four amino groups are connected in a linear or branched manner via an ethylene chain, but in the present invention, it also includes compounds having four amino groups and a piperazine ring structure. Specific compound names of TETA include, for example, 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 term "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 having 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 similarly have six amino groups and also have 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-[(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. The term "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 having 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. The "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 which 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 triethylenetetramine (TETA) consisting of a mixture of diethylenetriamine (DETA), 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), which consists 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 Polyethylene polyamine with 8 or more amino groups, trade name "Poly8" (manufactured by Tosoh Corporation) It is preferable that the polymer is at least one selected from the group consisting of:

[0050] In the present invention, the amine compound may be a commercially available product or may be synthesized by a known method, and is not particularly limited. Furthermore, the purity of the amine compound is not particularly limited, but is preferably 95% or more, and particularly preferably 99% or more. If the purity is less than 95%, the amount of carbon dioxide absorbed may decrease.

[0051] In the present invention, when the carbon dioxide separation composition contains an amine compound, the mass ratio of the amide compound to the amine compound is not particularly limited, but is preferably, for example, 1:400 to 400:1.

[0052] The antifoaming agent is not particularly limited, but examples thereof include silicone-based antifoaming agents and fatty acid ester-based antifoaming agents. The coexistence of such antifoaming agents can be industrially advantageous in that it can suppress the volatilization of the amide compound and the deterioration of carbon dioxide capture performance due to foaming of the carbon dioxide separation composition.

[0053] The amount of antifoaming agent added can be 0.00001 to 0.1 mass %, and more preferably 0.0005 to 0.01 mass %, assuming that the total mass of the carbon dioxide separation composition is 100 mass %.

[0054] The antioxidant is not particularly limited, but examples thereof include phosphorous compounds, disulfide compounds, phenolic compounds, polyhydric alcohols, mercaptoimidazole compounds, etc. Addition of such antioxidants can be industrially advantageous in that it can suppress deterioration of the carbon dioxide separation composition and improve its stability. The amount of antioxidant added can be 0.001 to 5 mass%, assuming the total mass of the carbon dioxide separation composition to be 100 mass%, and is more preferably 0.01 to 1 mass%, in order not to affect the carbon dioxide recovery performance.

[0055] Next, a method for separating carbon dioxide using the above carbon dioxide separating composition will be described.

[0056] The carbon dioxide separation method of the present invention is characterized by comprising the step of contacting a gas containing carbon dioxide with the above-mentioned carbon dioxide separation composition to absorb the carbon dioxide in the mixed gas into the carbon dioxide separation composition.

[0057] Furthermore, the carbon dioxide separation method of the present invention may include the steps of bringing a gas containing carbon dioxide into contact with the carbon dioxide separation composition described above to absorb the carbon dioxide in the mixed gas into the carbon dioxide separation composition, and heating and / or reducing the pressure of the carbon dioxide separation composition that has absorbed the carbon dioxide to release the carbon dioxide.

[0058] In the carbon dioxide separation method of the present invention, the method for contacting a carbon dioxide-containing gas with the carbon dioxide separation composition of the present invention is not particularly limited, and known methods can be used, such as a bubbling method and a head-on contact method using a packed column or a plate column.

[0059] In the carbon dioxide separation method of the present invention, the temperature at which a gas containing carbon dioxide is absorbed into the carbon dioxide separation composition of the present invention is not particularly limited, but can usually be in the range of 0°C to 50°C.

[0060] In the carbon dioxide separation method of the present invention, the temperature at which carbon dioxide is released from the carbon dioxide separation composition of the present invention is not particularly limited, but is typically in the range of 60 to 150° C. However, from the viewpoint of energy saving, it is preferably 100° C. or lower.

[0061] Furthermore, the carbon dioxide separating composition of the present invention can be used in a carbon dioxide chemical absorption method by supporting or impregnating it on any carrier and forming a carbon dioxide absorbing / releasing agent.

[0062] The carrier is not particularly limited, but examples thereof include silica, alumina, magnesia, porous glass, activated carbon, polymethyl methacrylate-based porous resin, and fibers.

[0063] The silica may be crystalline or non-crystalline (amorphous), and many types are known, such as zeolite-like silica having fine pores, mesoporous silica, etc. There are no particular restrictions on the silica that can be used in the carbon dioxide absorption and desorption agent of the present invention, and any silica that is commercially available can be used, but silica with a large surface area is preferred.

[0064] The amount of the carbon dioxide separation composition supported in the carbon dioxide absorption / desorption agent is preferably 5 to 70 mass%, and more preferably 10 to 60 mass%, where the mass of the carbon dioxide absorption / desorption agent on which the carbon dioxide separation composition is supported is 100 mass%, in terms of being excellent in terms of the amount of carbon dioxide absorbed and the operability of supporting the carbon dioxide separation composition.

[0065] The carbon dioxide absorbing and releasing agent can be applied to a carbon dioxide separation method widely known as a solid absorption method.

[0066] The solid absorption method is a method in which a carbon dioxide separating agent is brought into contact with a gas containing carbon dioxide to absorb the carbon dioxide, and then the absorbed carbon dioxide is released by heating or reducing the pressure.

[0067] In the solid absorption method, the temperature at which carbon dioxide is released is generally 100°C or higher, but when the carbon dioxide separation composition of the present invention is used, there are no particular restrictions on the temperature, and it may be below 100°C.

[0068] The carbon dioxide-containing gas may be pure carbon dioxide gas or a mixed gas containing carbon dioxide and other gases, such as, but not limited to, air, nitrogen, oxygen, hydrogen, argon, neon, helium, carbon monoxide, water vapor, methane, or nitrogen oxides.

[0069] The carbon dioxide-containing gas preferably has a carbon dioxide concentration of 5% by volume or more, more preferably 10% by volume or more.

[0070] In the carbon dioxide separation method of the present invention, there is no problem if additional steps other than the above steps (absorption step and diffusion step) are carried out. For example, a cooling step, a heating step, a washing step, an extraction step, an ultrasonic treatment step, a distillation step, or other steps of treating with chemicals can be carried out as appropriate.

[0071] The carbon dioxide separation method of the present invention is not particularly limited, but can be applied to, for example, separation of carbon dioxide (CO) from combustion exhaust gas generated in thermal power plants, steel plants, cement factories, etc., and separation of carbon dioxide (CO) from steam reformed gas obtained in a steam reforming process. [Example]

[0072] The present invention will be described below using examples, but the present invention should not be construed as being limited to these examples.

[0073] [Example 1] 25 g of N-[2-(N-formylamino)ethyl]piperazine and 75 g of pure water were mixed and stirred to obtain a carbon dioxide separation composition (100 g). The carbon dioxide separation composition (100 g) was placed in a 200 mL gas absorption bottle and the temperature was adjusted to 40 °C in a water bath. A mixed gas flow of 140 mL / min of carbon dioxide gas and 560 mL / min of nitrogen gas (a mixed gas with a carbon dioxide concentration of 20% by volume, hereinafter referred to as the "mixed gas flow") was blown into the carbon dioxide separation composition (100 g) at a rate of 140 mL / min. The blowing was continued until the carbon dioxide concentration of the mixed gas passing through the carbon dioxide separation composition reached 20% by volume. Next, the gas absorption bottle was adjusted to 100 °C, and the mixed gas was blown in. The amount of carbon dioxide gas emitted was measured using a gas flow meter and a carbon dioxide concentration meter. The weight of carbon dioxide gas emitted in 90 minutes was 16.0 g per 1 L of carbon dioxide separation composition.

[0074] [Example 2] 25 g of N-[2-(N-acetylamino)ethyl]piperazine and 75 g of pure water were mixed and stirred to obtain a carbon dioxide separation composition (100 g). The same procedure as in Example 1 was performed to measure the amount of carbon dioxide gas emitted from the carbon dioxide separation composition. The weight of carbon dioxide gas emitted in 90 minutes was 15.5 g per 1 L of the carbon dioxide separation composition.

[0075] [Example 3] 25 g of N-[2-(N-propionylamino)ethyl]piperazine and 75 g of pure water were mixed and stirred to obtain a carbon dioxide separation composition (100 g). The same procedure as in Example 1 was performed to measure the amount of carbon dioxide gas emitted from the carbon dioxide separation composition. The weight of carbon dioxide gas emitted over 90 minutes was 14.8 g per 1 L of the carbon dioxide separation composition.

[0076] [Comparative Example 1] 25 g of monoethanolamine (Tokyo Chemical Industry Co., Ltd.) and 75 g of pure water were mixed and stirred to obtain a carbon dioxide separation composition (100 g). The same procedure as in Example 1 was performed to measure the amount of carbon dioxide gas emitted from the carbon dioxide separation composition. The weight of carbon dioxide gas emitted in 90 minutes was 13.3 g per 1 L of the carbon dioxide separation composition.

[0077] [Table 1]

[0078] As is clear from the comparison between the above examples and comparative examples, the carbon dioxide separation composition of the present invention had a higher carbon dioxide emission rate at a constant temperature than conventional carbon dioxide separation compositions, and was superior in energy efficiency during carbon dioxide capture.

Claims

1. A carbon dioxide separation composition which is an aqueous solution containing at least one amide compound represented by general formula (1), wherein the content of the amide compound is 0.1 to 50 mass% relative to the total mass of the carbon dioxide separation composition, taken as 100 mass%. 【Chemical 1】 [In formula (1), R １ R represents an alkyl group having an amide group, represented by the following general formula (2): ２ represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms which may be branched, a hydroxyalkyl group having 1 to 4 carbon atoms which may be branched, and R １ represents a group.] 【Chemistry 2】 [In formula (2), R ３ represents a hydrogen atom or an optionally branched alkyl group having 1 to 4 carbon atoms; and X represents an alkylene group having 1 to 3 carbon atoms.

2. The carbon dioxide separation composition according to claim 1, wherein in general formula (2), X is an ethylene group.

3. The amide compound is N-[2-(1-piperazinyl)ethyl]formamide, N-[2-(1-piperazinyl)ethyl]acetamide, N-[2-(1-piperazinyl)ethyl]propionamide, N-[2-(1-piperazinyl)ethyl]butanamide, 1,4-bis[2-(N-formylamino)ethyl]piperazine, 1,4-bis[2-(N-acetylamino)ethyl]piperazine, 1,4-bis[2-(N-propionylamino)ethyl]piperazine, 1,4-bis[2-(N-butanoylamino)ethyl]piperazine, The carbon dioxide separation composition according to claim 1.

4. The carbon dioxide separation composition according to claim 1, wherein the carbon dioxide separation composition further contains an amine compound, and the content of the at least one amine compound is 2 to 70 mass% relative to the total amount of the carbon dioxide separation composition being 100 mass%.

5. A method for separating carbon dioxide, comprising the steps of contacting a mixed gas containing carbon dioxide with the carbon dioxide separation composition according to any one of claims 1 to 4, and allowing the carbon dioxide in the mixed gas to be absorbed by the carbon dioxide separation composition.

6. 5. A method for separating carbon dioxide, comprising the steps of: bringing a mixed gas containing carbon dioxide into contact with the carbon dioxide separation composition according to claim 1 to cause the carbon dioxide in the mixed gas to be absorbed into the carbon dioxide separation composition; and heating and / or reducing the pressure of the carbon dioxide separation composition that has absorbed the carbon dioxide to release the carbon dioxide.

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