Method for separating and capturing carbon dioxide and method for recycling carbon dioxide

Abstract

In a carbon dioxide separation and recovery method that uses amine compounds for carbon dioxide absorption and recovery, the energy required for regenerating the CO2 absorption / release agent is reduced, and the process between the absorption and recovery steps is simplified. [Solution] A method for separating and recovering carbon dioxide, comprising: (A1) absorbing carbon dioxide into an amine compound polar solution containing an amine compound and a polar solvent to precipitate a solid reaction product of the amine compound and carbon dioxide in the amine compound polar solution, thereby obtaining a polar reaction product which is a polar suspension or slurry obtained therefrom; (B1) treating the polar reaction product obtained in step (A1) with a nonpolar solvent to remove the polar solvent, thereby obtaining a nonpolar reaction product which is a nonpolar suspension or slurry obtained therefrom containing the solid reaction product and the nonpolar solvent; (C1) heating the nonpolar reaction product obtained in step (B1) under pressure, atmospheric pressure or reduced pressure to separate and recover carbon dioxide and regenerate the amine compound from the nonpolar reaction product, thereby obtaining an amine compound nonpolar solution; and (D1) treating the amine compound nonpolar solution obtained in step (C1) with a polar solvent to replace the solvent and obtain an amine compound polar solution.

Description

Technical Field

[0001] The present invention relates to a method for separating and recovering carbon dioxide and a method for regenerating carbon dioxide.

Background Art

[0002] According to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC), in order to limit the increase in the global average temperature caused by anthropogenic greenhouse gas emissions to within 1.5°C compared to before the Industrial Revolution, it is necessary to reduce the net global carbon dioxide (CO2) emissions to zero by 2050. Thus, the development and social implementation of technologies for low-energy-cost CO2 separation, recovery, transportation, and fixation from CO2 emission sources or the atmosphere have become urgent issues. As methods for CO2 separation and recovery, thermal swing, pressure swing, and more recently, new methods such as electric swing, humidity swing, and pH swing have been proposed.

[0003] In thermal swing, by using a CO2 absorption and release agent that undergoes a phase change from liquid to solid when absorbing CO2, it is known from Patent Document 1 that the energy loss due to the sensible heat and latent heat of vaporization of the solvent when heating the CO2 absorption and release agent to recover CO2 can be reduced. As an example where the energy loss due to the sensible heat and latent heat of vaporization of the solvent becomes a problem, in a general amine process used for treating combustion exhaust gas, in order to mitigate the corrosiveness of the amine, it is necessary to use an aqueous solution with an amine concentration of, for example, 30 wt% or less, which requires a large amount of energy input for heating the water. Also, when the temperature of the thermal swing is significantly higher than normal temperature, it becomes a factor for increasing the input energy.

[0004] According to Patent Document 1, when a compound represented by the following general formula (1), for example, isophoronediamine (IPDA) which is a liquid at normal temperature and pressure (see the following formula (2)), absorbs CO2 and the precipitated carbamic acid (CA1) (see the following formula (3)) is dried and then heated in a nitrogen gas atmosphere, CO2 can be released at a relatively low temperature of about 60°C at atmospheric pressure.

[0005] [ka]

[0006] [ka]

[0007] [ka]

[0008] [ka]

[0009] In industrial-scale processes, CA1 is heated in a suspension state mixed with IPDA and a solvent. When water is used as the solvent, CA1 attracts water of hydration to become CA1·H2O (see (4) above). The pressure and temperature required to extract CO2 from CA1·H2O in an aqueous IPDA solution are, for example, around 120°C at 20kPa and around 140°C at atmospheric pressure, and a considerably long regeneration process is required.

[0010] By using an organic solvent such as DMSO instead of water as the solvent for the IPDA stock solution, the precipitate formed when CO2 is absorbed can be in the state of CA1 rather than CA1·H2O, potentially allowing for a lower temperature to be required for CO2 release compared to CA1·H2O. However, when attempting to absorb CO2 from exhaust gas or air, water contamination is unavoidable.

[0011] Because the precipitated CA1 or CA1·H2O consists of fine particles, the polar solvent after CO2 absorption becomes suspended in these particles. Separating the solvent requires the introduction of solid-liquid separation processes such as filtration or a filter press, which increases process costs and energy costs. A method for transferring the CO2 absorption / release agent between the absorption and recovery processes in a more manageable state is desired. [Prior art documents] [Patent Documents]

[0012] [Patent Document 1] Patent No. 7441557 [Overview of the project] [Problems that the invention aims to solve]

[0013] The CO2 separation and recovery method described in Patent Document 1 requires low pressure conditions such as 20 kPa and 120°C, as well as a high-temperature heat source, when regenerating CA1·H2O in an IPDA solution. A challenge is to reduce the amount of power required for depressurization and the energy input for heating by shortening the regeneration time.

[0014] Furthermore, the entire process becomes inefficient if a batch process, such as dehydration (solvent removal) using a filter press, is inserted between the transfer of the suspended CO2 absorption / release agent after CO2 absorption to the CO2 recovery process. Simplifying the process is a challenge.

[0015] The present invention aims to reduce the energy required for the regeneration of the CO2 absorption / release agent and to simplify the process between the absorption and recovery steps in a carbon dioxide separation and recovery method using amine compounds. [Means for solving the problem]

[0016] To solve the aforementioned problems, we discovered that by using solvents with different polarities in the carbon dioxide absorption and recovery processes, it is possible to reduce the energy required for the regeneration of the CO2 absorption and release agent, and further simplify the process between the absorption and recovery processes, thus completing the present invention.

[0017] An aspect of the present invention that achieves the above objective is a method for separating and recovering carbon dioxide, comprising the steps of: (A1) absorbing carbon dioxide into an amine compound polar solution containing an amine compound represented by the following formula (1) and a polar solvent to precipitate a solid reaction product of the amine compound and the carbon dioxide in the amine compound polar solution, thereby obtaining a polar reaction product which is a polar suspension or slurry obtained therefrom; (B1) treating the polar reaction product obtained in step (A1) with a nonpolar solvent to remove the polar solvent, thereby obtaining a nonpolar reaction product which is a nonpolar suspension or slurry obtained therefrom containing the solid reaction product and the nonpolar solvent; (C1) heating the nonpolar reaction product obtained in step (B1) under pressure, atmospheric pressure or reduced pressure to separate and recover carbon dioxide and regenerate the amine compound from the nonpolar reaction product, thereby obtaining an amine compound nonpolar solution; and (D1) treating the amine compound nonpolar solution obtained in step (C1) with a polar solvent to replace the solvent and obtain an amine compound polar solution.

[0018] [ka]

[0019] However, in the formula, m is either 0 or 1; R 1 and R 2 Each of these is independently an alkyl group, an alkoxy group, a carboxyl group, an alkyloxycarbonyl group, a formyl group, an alkylcarbonyl group, an alkylthio group, a sulfo group, an alkyloxysulfonyl group, a nitro group, a hydroxyl group, a thiol group, a cyano group, or a halogen atom, and the alkyl group may have substituents; p1 and p2 are independently 1 or 2; when m is 0, q1 is an integer from 0 to 11, provided that p1 + q1 is 12 or less, when m is 1, q1 is an integer from 0 to 10, provided that p1 + q1 is 11 or less, q2 is an integer from 0 to 10, and when q1 is an integer of 2 or more, there are two or more R 1 They may be the same or different from each other, and if q2 is an integer greater than or equal to 2, then there may be two or more R 2may be the same as or different from each other, q1 is an integer of 2 or more, and two or more Rs 1 When it is the alkyl group which may have a substituent, the two or more Rs 1 may be bonded to each other to form a ring, q2 is an integer of 2 or more, and two or more Rs 2 When it is the alkyl group which may have a substituent, the two or more Rs 2 may be bonded to each other to form a ring. However, except when m is 0, p 1 is 2, and the two amino groups to which p 1 is attached are arranged in the meta position to each other.

[0020] A second aspect of the present invention is a method for separating and recovering carbon dioxide according to the above aspect, which comprises performing a step (E1) of repeating the steps (A1) to (D1) using the polar solution of the amine compound obtained in the step (D1) as the polar solution of the amine compound in the step (A1).

[0021] A third aspect of the present invention is a method for separating and recovering carbon dioxide according to the above aspect, in which in the step (B1), a suspension or a slurry is used as the polar reactant, the nonpolar solvent is mixed with this, and then the polar solvent is separated and removed to obtain the nonpolar reactant.

[0022] A fourth aspect of the present invention is a method for separating and recovering carbon dioxide according to the above aspect, in which in the step (C1), the nonpolar reactant is heated to 10−150° C. under a pressure of normal pressure to 20 kPa to release CO2 and obtain the nonpolar solution of the amine compound.

[0023] A fifth aspect of the present invention is a method for separating and recovering carbon dioxide according to the above aspect, in which in the step (D1), a polar solvent is mixed with the nonpolar solution of the amine compound to transfer the amine compound to the polar solvent, and then the nonpolar solvent is separated and recovered to obtain the polar solution of the amine compound.

[0024] A sixth aspect of the present invention is a method for separating and recovering carbon dioxide according to the above aspect, wherein the polar solvent is at least one selected from the group consisting of water, methanol, ethanol, acetone, acetic acid, ammonia, dimethyl sulfoxide (DMSO), and sulfuric acid.

[0025] A seventh aspect of the present invention is a method for separating and recovering carbon dioxide according to the above aspect, wherein the nonpolar solvent is at least one selected from the group consisting of hexane, octane, nonane, decane, benzene, toluene, xylene, diethyl ether, and cyclohexane.

[0026] An eighth aspect of the present invention is the method for separating and recovering carbon dioxide according to the above aspect, wherein the amine compound comprises isophorone diamine (IPDA).

[0027] A ninth aspect of the present invention is a method for separating and recovering carbon dioxide according to the above aspect, wherein the solid reactant includes solid carbamic acid.

[0028] A tenth aspect of the present invention is a method for separating and recovering carbon dioxide according to the above aspect, comprising the step (A1) being carried out at a first location, the step (F1) being transported to a second location where carbon dioxide is regenerated, and the step (C1) being carried out at the second location.

[0029] An eleventh aspect of the present invention is a method for separating and recovering carbon dioxide according to the above aspect, comprising the steps (A1) and (B1) performed at a first location, the step (G1) of transporting the obtained nonpolar reactant to a second location where carbon dioxide is regenerated, and the step (C1) performed at the second location.

[0030] A twelfth aspect of the present invention is a method for separating and recovering carbon dioxide as described above, comprising the step (H1) of transporting the nonpolar solution of the amine compound obtained in step (C1) or the polar solution of the amine compound obtained in step (D1) from the second location to the first location, and repeating steps (A1) to (D1), steps (F1) and (H1).

[0031] A thirteenth aspect of the present invention is a method for separating and recovering carbon dioxide as described in the above aspect, comprising a step (H1) of transporting the nonpolar solution of the amine compound obtained in step (C1) or the polar solution of the amine compound obtained in step (D1) from a second location to a first location, wherein if the nonpolar solution of the amine compound obtained in step (C1) is transported, after performing step (D1), steps (A1) to (D1), steps (G1) and (H1) are repeated.

[0032] A fourteenth aspect of the present invention is a method for separating and recovering carbon dioxide according to the above aspect, wherein in step (C1) performed at the second location, renewable energy is used for the heating step.

[0033] A fifteenth aspect of the present invention is a method for separating and recovering carbon dioxide as described above, wherein the amine compound used is an amine compound containing isophorone diamine (IPDA), and the polar solvent used is water.

[0034] A sixteenth aspect of the present invention is a method for separating and recovering carbon dioxide as described above, wherein the nonpolar solvent is at least one selected from the group consisting of hexane, octane, nonane, decane, benzene, toluene, xylene, diethyl ether, and cyclohexane.

[0035] A 17th aspect of the present invention is a method for regenerating carbon dioxide, wherein carbon dioxide is absorbed into a polar solution of an amine compound containing an amine compound including isophorone diamine (IPDA) and a polar solvent to obtain a polar reaction product which is a polar suspension or slurry containing solid carbamic acid, which is a reaction product of the amine compound and the carbon dioxide, and carbon dioxide is regenerated from this polar reaction product, wherein the polar reaction product is treated with a nonpolar solvent to remove the polar solvent to obtain a nonpolar reaction product which is a nonpolar suspension or slurry containing the reaction product and the nonpolar solvent, the obtained nonpolar reaction product is heated under normal or reduced pressure to separate and recover carbon dioxide, the amine compound is regenerated from the nonpolar reaction product, and a nonpolar solution of the amine compound is obtained. [Effects of the Invention]

[0036] According to the present invention, a novel CO2 separation and recovery system is provided, which can reduce energy input by lowering the regeneration temperature when regenerating CO2 from the CO2-absorbing reactants. Furthermore, even when regeneration is performed without separating the reactants, the energy input is sufficiently reduced. [Brief explanation of the drawing]

[0037] [Figure 1] A graph comparing the relationship between the temperature of a decane solvent containing solid CA1·H2O or an aqueous solvent and the time course of the CO2 concentration in the outlet gas when these solvents are heated. [Figure 2] A graph comparing the time course of the solvent temperature and the CO2 concentration in the outlet gas when a decane solvent containing solid CA1·H2O or an IPDA solvent is heated. [Modes for carrying out the invention]

[0038] The present invention will be described in more detail below. The present invention provides a method for separating and recovering carbon dioxide, comprising the steps of: (A1) absorbing carbon dioxide into a liquid carbon dioxide absorbent containing an amine compound represented by the following formula (1) and a polar solvent, thereby precipitating a reaction product of the amine compound and the carbon dioxide in the carbon dioxide absorbent to obtain a polar suspension; (B1) treating the polar suspension obtained in step (A1) with a nonpolar solvent to remove the polar solvent to obtain a nonpolar suspension containing the reaction product and the nonpolar solvent; (C1) heating the nonpolar suspension obtained in step (B1) under normal or reduced pressure to release CO2 and regenerate the reaction product into the amine compound to obtain a nonpolar solution of the amine compound; and (D1) replacing the nonpolar solvent in the nonpolar solution of the amine compound obtained in step (C1) with the polar solvent to obtain the carbon dioxide absorbent.

[0039] Here, the amine compound of formula (1) below is a known compound that was also disclosed in Japanese Patent Application Publication No. 2024-075122, which was previously filed by the present applicant, and is disclosed below.

[0040] [ka]

[0041] In the formula, m is either 0 or 1; R 1 and R 2 Each of these is independently an alkyl group, an alkoxy group, a carboxyl group, an alkyloxycarbonyl group, a formyl group, an alkylcarbonyl group, an alkylthio group, a sulfo group, an alkyloxysulfonyl group, a nitro group, a hydroxyl group, a thiol group, a cyano group, or a halogen atom, and the alkyl group may have substituents; p1 and p2 are independently 1 or 2; when m is 0, q1 is an integer from 0 to 11, provided that p1 + q1 is 12 or less, when m is 1, q1 is an integer from 0 to 10, provided that p1 + q1 is 11 or less, q2 is an integer from 0 to 10, and when q1 is an integer of 2 or more, there are two or more R 1 They may be the same or different from each other, and if q2 is an integer greater than or equal to 2, then there may be two or more R2 The elements may be identical or different from each other, q1 is an integer greater than or equal to 2, and there are two or more R elements. 1 If the alkyl group may have substituents, then the two or more R 1 The elements may be interconnected to form a ring, and q2 is an integer greater than or equal to 2, and there are two or more R elements. 2 If the alkyl group may have substituents, then the two or more R 2 They may be bonded to each other to form a ring. However, m is 0 and p 1 Since is 2, p 1 Except when the two amino groups with the notation are positioned at the meta position relative to each other.

[0042] Here, the amine compound represented by formula (1) above is preferably the compound represented by the following formulas (11A), (12A), or (11B).

[0043] [ka]

[0044] In the formula, R 11 , R 12 , R 13 and R 21 Each of these is independently a C1-C10 alkyl group, a C1-C10 alkoxy group, a carboxyl group, a C2-C11 alkyloxycarbonyl group, a formyl group, a C2-C11 alkylcarbonyl group, a C1-C10 alkylthio group, a sulfo group, a C1-C10 alkyloxysulfonyl group, a nitro group, a hydroxyl group, a thiol group, a cyano group, or a halogen atom, and the alkyl group may have an amino group as a substituent;q 11 and q 12 Each of these is an integer from 0 to 6, and q 11 If is an integer greater than or equal to 2, then two or more R 11 They may be the same or different from each other, q 12 If is an integer greater than or equal to 2, then two or more R 12 They may be the same or different from each other, q11 If is an integer greater than or equal to 2, and there are two or more R 11 If the alkyl group may have an amino group as a substituent, then the two or more R 11 They may be bonded to each other to form a ring, q 12 If is an integer greater than or equal to 2, and there are two or more R 12 If the alkyl group may have an amino group as a substituent, then the two or more R 12 They may be bonded to each other to form a ring; q 13 and q 21 Each of these is an integer from 0 to 4, and q 13 If is an integer greater than or equal to 2, then two or more R 13 They may be the same or different from each other, q 21 If is an integer greater than or equal to 2, then two or more R 21 They may be the same or different from each other, q 13 If is an integer greater than or equal to 2, and there are two or more R 13 If the alkyl group may have an amino group as a substituent, then the two or more R 13 They may be bonded to each other to form a ring, q 21 If is an integer greater than or equal to 2, and there are two or more R 21 If the alkyl group may have an amino group as a substituent, then the two or more R 21 These may be bonded to each other to form a ring. However, this excludes the case in formula (12A) where the two amino groups directly bonded to the carbon atoms constituting the cyclohexane ring skeleton are positioned meta relative to each other.

[0045] Furthermore, the amine compound (11A), compound (12A), or compound (11B) of formula (1) is preferably a compound represented by the following formulas (111A), (121A), (122A), or (111B).

[0046] [ka]

[0047] In the formula, R 111 , R 121 , R 122 , R 131 and R 211 Each of these is independently a C1-C5 alkyl group, a C1-C5 alkoxy group, a C2-C6 alkyloxycarbonyl group, a formyl group, a C2-C6 alkylcarbonyl group, a C1-C5 alkylthio group, a hydroxyl group, a thiol group, a cyano group, or a halogen atom, and the alkyl group may have an amino group as a substituent;q 111 , q 121 and q 122 Each of these is an integer from 0 to 4, and q 111 If is an integer greater than or equal to 2, then two or more R 111 They may be the same or different from each other, q 121 If is an integer greater than or equal to 2, then two or more R 121 They may be the same or different from each other, q 122 If is an integer greater than or equal to 2, then two or more R 122 They may be the same or different from each other, q 111 If is an integer greater than or equal to 2, and there are two or more R 111 If the alkyl group may have an amino group as a substituent, then the two or more R 111 They may be bonded to each other to form a ring, q 121 If is an integer greater than or equal to 2, and there are two or more R 121 If the alkyl group may have an amino group as a substituent, then the two or more R 121 They may be bonded to each other to form a ring, q 122 If is an integer greater than or equal to 2, and there are two or more R 122 If the alkyl group may have an amino group as a substituent, then the two or more R 122 They may be bonded to each other to form a ring; q 131 and q 211 Each of these is an integer between 0 and 2, and q 131 If it is 2, then two R 131They may be the same or different from each other, q 211 If it is 2, then two R 211 They may be the same or different from each other, q 131 The value is 2, and there are 2 R 131 If the alkyl group may have an amino group as a substituent, then the two R 131 They may be bonded to each other to form a ring, q 211 The value is 2, and there are 2 R 211 If the alkyl group may have an amino group as a substituent, then the two R 211 They may be bonded to each other to form a ring.

[0048] In step (A1) of the present invention, the amine compound described above is in liquid form, but this amine compound is mixed with a polar solvent to create a mixture of the amine compound and the polar solvent, which is used as a carbon dioxide absorbent. The polar solvent is a liquid carbon dioxide absorbent containing a mixture of a solvent compatible with the amine compound.

[0049] The polar solvent is not limited as long as it is compatible with the amine compound, but at least one selected from, for example, water, methanol, ethanol, acetone, acetic acid, ammonia, dimethyl sulfoxide (DMSO), sulfuric acid, etc., may be used. While there are no particular restrictions in step (A1), if the same polar solvent as in step (D1) described later is used, it is preferable to use one that has higher compatibility with the amine compound than the nonpolar solvent described later. Considering cost and other factors, water is preferable.

[0050] Step (A1) utilizes the property of amine compounds to solidify upon reaction with carbon dioxide. Specifically, a liquid carbon dioxide absorbent is brought into contact with air or a gas containing carbon dioxide to absorb the carbon dioxide, causing the reaction product of the amine compound and carbon dioxide to precipitate in the carbon dioxide absorbent, thereby obtaining a polar suspension. The reaction product of the amine compound and carbon dioxide is a carbamic acid derivative, and it is preferable to carry out the contact between the carbon dioxide absorbent and carbon dioxide under conditions that facilitate the precipitation of the reaction product.

[0051] It is preferable to maximize the contact area and contact efficiency between the carbon dioxide absorbent and carbon dioxide, and to keep the contact temperature as low as possible. While diamines are preferable as the easily precipitated amine compounds, monoamines can also be used if the concentration of the amine compound is as high as possible and the reaction temperature is kept as low as possible.

[0052] Considering the above points, the temperature of the carbon dioxide absorbent is, for example, 0 to 90°C, preferably 5 to 60°C, and more preferably 5 to 40°C. The concentration of the amine compound in the carbon dioxide absorbent is, for example, 0.05 to 10 M, preferably 0.08 to 3 M, and more preferably 0.1 to 1 M. Note that the concentration unit "M" represents "mol / L".

[0053] As described above, in step (A1), a polar suspension is obtained in which a solid carbamic acid derivative, which is a reaction product of an amine compound and carbon dioxide, is suspended in a polar solvent.

[0054] In this invention, in step (B1), the polar suspension or slurry is then treated with a nonpolar solvent to remove the polar solvent and obtain a nonpolar suspension containing the reactants and the nonpolar solvent. This treatment is based on the understanding that by mixing a nonpolar solvent with a polar suspension in which a solid carbamic acid derivative is suspended in a polar solvent, stirring, and allowing it to stand, the solid carbamic acid derivative migrates to the vicinity of the nonpolar solvent phase. That is, a suspension phase is formed between the polar solvent phase and the nonpolar solvent phase, and a nonpolar suspension is obtained by removing the polar solvent. In other words, instead of separating the carbamic acid derivative from the polar suspension by filtration or the like and mixing it with a nonpolar solvent to obtain a nonpolar suspension, a nonpolar suspension in which a solid carbamic acid derivative is suspended can be obtained by mixing the polar suspension with a nonpolar solvent. Of course, substitution may also be performed by adding a nonpolar solvent to a slurry or cake (both sometimes simply called a slurry) obtained by desolvating a polar suspension containing a carbamic acid derivative with a cyclone and removing the polar solvent. In any case, this step (B1) is a crucial point of the present invention.

[0055] In the present invention, in step (C1), a nonpolar suspension containing a solid carbamic acid derivative is heated under pressure, atmospheric pressure, or reduced pressure to release CO2 and regenerate the carbamic acid derivative into an amine compound, thereby obtaining a nonpolar solution of the amine compound.

[0056] A second important point of this invention is that the energy input required to regenerate amine compounds by releasing carbon dioxide from a non-polar suspension is significantly less than the energy input required to regenerate amine compounds from a polar suspension. That is, when regenerating amine compounds from a polar suspension such as water, it is known that after the peak of carbon dioxide release has passed, the rate of carbon dioxide release decreases and it takes time for the carbon dioxide content to become almost zero. However, when carbon dioxide is released from a non-polar suspension, the carbon dioxide content becomes almost zero immediately after the peak of release has passed, and as a result, the energy input is greatly reduced.

[0057] The reason why less energy is required to release carbon dioxide from a nonpolar suspension and regenerate amine compounds is partly because nonpolar suspensions have a lower specific heat than polar suspensions. However, experiments have shown that the temperature at which carbon dioxide is released from carbamic acid derivatives is lower in nonpolar solvents than in polar solvents, and this finding formed the basis for the present invention.

[0058] In this step (C1), the nonpolar suspension is heated under pressure, at atmospheric pressure to 20 kPa, at 100 to 150°C, preferably at atmospheric pressure to 90 kPa, at 110 to 130°C to release CO2 and obtain a nonpolar solution containing the amine compound.

[0059] Furthermore, in the present invention, in step (D1), the nonpolar solvent in the nonpolar solution of the amine compound obtained in step (C1) is replaced with a polar solvent, which is then used as a carbon dioxide absorbent in step (A1), and this can be used in the next step (A1).

[0060] This invention is also based on the finding that when a polar solvent is mixed with a nonpolar solution in which an amine compound is dissolved in a nonpolar solvent and allowed to stand, the amine compound migrates from the nonpolar solvent to the polar solvent, resulting in a polar solvent solution. In other words, the third important point of this invention is that by mixing and stirring a polar solvent with a nonpolar solution and allowing it to stand, the amine compound migrates to the polar solvent, becoming a polar solution and allowing the original carbon dioxide absorbent to be regenerated.

[0061] The nonpolar solvent that can be used in the present invention is not particularly limited as long as it can carry out steps (B1), (C1), and (D1) and the energy input in step (C1) is reduced compared to when a polar solvent is used. Preferably, it is selected from the group consisting of hexane, octane, nonane, decane, benzene, toluene, xylene, diethyl ether, and cyclohexane, and more preferably from hydrocarbons such as hexane, octane, nonane, and decane.

[0062] The carbon dioxide separation and recovery method of the present invention is a novel CO2 separation and recovery system that includes the steps (A1) to (D1) described above. By absorbing CO2 with a carbon dioxide absorbent containing an amine compound, the energy input can be reduced by lowering the regeneration temperature when regenerating CO2 from the carbamic acid derivative, which is a solid reactant formed by the reaction with CO2. Furthermore, even if the regeneration is performed without separating the reactants, the energy input can be sufficiently reduced. In addition, the nonpolar solvent in the nonpolar solution of the amine compound remaining after carbon dioxide regeneration can be easily replaced with a polar solvent, allowing the original carbon dioxide absorbent to be regenerated. This carbon dioxide absorbent can then be used in step (A1) (step (E1)), thereby enabling the steps (A1) to (D1) to be repeated.

[0063] Furthermore, the carbon dioxide separation and recovery method of the present invention includes a step (F1) in which step (A1) is carried out at a first location, and the obtained polar reaction product is transported by tanker or truck to a second location where carbon dioxide is regenerated, and step (C1) can be carried out at the second location.

[0064] Furthermore, the process may also include a step (G1) in which steps (A1) and (B1) are carried out at a first location, and the resulting nonpolar reactant is transported by tanker or truck to a second location where carbon dioxide is regenerated, and step (C1) is carried out at the second location. Here, the second location is, for example, a place where renewable energy can be used, and by conducting the project at this second location, overall energy reduction can be achieved.

[0065] Furthermore, the nonpolar amine compound solution obtained in step (C1) carried out at the second location can be transported from the second location to the first location, and steps (A1) to (D1), step (F1) or step (G1), and (H1) can be repeated.

[0066] Alternatively, steps (C1) and (D1) can be carried out at a second location, the resulting amine compound polar solution can be transported from the second location to the first location, and steps (A1) to (D1), steps (F1) or (G1), and (H1) can be repeated.

[0067] In any case, the present invention provides a method for separating and recovering carbon dioxide, in which carbon dioxide is absorbed into a polar solution of an amine compound containing an amine compound including isophorone diamine (IPDA) and a polar solvent to obtain a polar reaction product which is a polar suspension or slurry containing solid carbamic acid, which is a reaction product of the amine compound and the carbon dioxide, and carbon dioxide is separated and recovered from this polar reaction product. The key point of this method is that the polar reaction product is treated with a nonpolar solvent to remove the polar solvent, resulting in a nonpolar reaction product which is a nonpolar suspension or slurry containing the reaction product and the nonpolar solvent, and the obtained nonpolar reaction product is heated under pressure, atmospheric pressure or reduced pressure to separate and recover carbon dioxide and regenerate the amine compound from the nonpolar reaction product to obtain a nonpolar solution of the amine compound. [Examples]

[0068] The present invention will be described in more detail below with reference to specific examples. However, the present invention is not limited in any way to the examples shown below. First, we will explain the results of experiments conducted to confirm the effects of steps (D1) and (B1) of the present invention.

[0069] In the experiments and examples, isophorone diamine (IPDA) was used as the amine compound, and carbamic acid (CA1) and its hydrate (CA1·H2O) were used as the reaction products with carbon dioxide. In the examples, it is possible that dicarbamic acid (CA2) and its hydrate were also produced when isophorone diamine (IPDA) reacted with carbon dioxide, in addition to carbamic acid (CA1) and its hydrate (CA1·H2O), but this point remains unconfirmed. The chemical formulas for these compounds are shown below.

[0070] [ka]

[0071] [ka]

[0072] [ka]

[0073] [ka]

[0074] [ka]

[0075] [Example of experiment] The following experiments were conducted on each step of the carbon dioxide separation and recovery method.

[0076] [Experimental Example A11] (Process (A1)) Process (A1), namely the CO2 absorption process, was carried out as follows. When 100% CO2 gas was blown into a 20 wt% clear IPDA aqueous solution, turbidity due to the precipitation of CA1·H2O solid occurred after 33 minutes, and after 48 minutes, the entire solution became turbid and turned into an opaque suspension. Upon standing, CA1·H2O solid precipitated at the bottom of the aqueous solution.

[0077] [Experimental Examples B11-B15] (Process (B1)) The following experiment was conducted on step (B1), which involves replacing the water in a polar suspension containing CA1·H2O solid with decane to obtain a nonpolar suspension.

[0078] [Experimental Example B11] When 10g of solid CA1·H2O, 100mL of decane, and 100mL of water were placed in a 300mL beaker and stirred with a stirrer for 2-3 minutes, then allowed to stand, it was found that the solid CA1·H2O floated at the interface between the decane layer and the aqueous layer, forming a three-layer structure from top to bottom: a decane layer, a solid CA1·H2O layer, and an aqueous layer. As shown in [Experimental Example A11], solid CA1·H2O normally precipitates in water, so this unique phenomenon is thought to be due to the effect of decane. In principle, it is thought that because solid CA1·H2O is lipophilic, the specific gravity of the solid becomes lighter when it is coated with decane, causing it to float on water. Due to this property, it is possible to scoop up the solid CA1·H2O with a mesh like a tea strainer, or to drain only the aqueous layer from the bottom, making it easy to replace the solvent of solid CA1·H2O from water to decane.

[0079] [Experimental Example B12] This experiment is for the purpose of using a centrifuge in process (B1). Using a centrifuge is effective in quickly eliminating bubbles generated by excessive stirring during process (B1) and in shortening the time required for separation.

[0080] 4g of solid CA1·H2O, 40mL of water, and 40mL of decane were placed in a glass container for a centrifuge, shaken by hand, and then centrifuged at 1000 RPM for 10 minutes. The changes before and after the centrifugation were observed. To improve visibility, the aqueous layer was colored blue with food coloring, and the same procedure was performed and observed again. Observation of the color revealed that the CA1·H2O solid was floating on the surface of the lower aqueous layer rather than sinking into the upper decane layer.

[0081] [Experimental Example B13] Experimental Examples A11 and B11 showed that the CA1·H2O solid preferentially envelops itself in decane rather than water. Therefore, it is thought that the solvent of the CA1·H2O solid can be easily replaced from water to decane simply by washing it with a mixture of water and decane.

[0082] When a mixture of 100 mL of decane, 100 mL of water, and 10 g of solid CA1·H2O was filtered 3 or 4 times using a tea strainer with a mesh of about 1 mm, it was found that most of the solid CA1·H2O was captured by the tea strainer, and only the liquid could be separated. When the mixed solution of water and decane that passed through the tea strainer was separated using a separatory funnel and weighed, it was found that there was 79.4 g of water (81.2% of the total water) and 35.3 g of decane (49.4% of the total decane). From these measurement results, it was found that solid CA1·H2O tends to surround itself with decane more than water, and that simply mixing solid CA1·H2O with water and decane completes a certain degree of substitution of the solid CA1·H2O from water to decane.

[0083] [Experimental Example B14] A mixture of 100 mL of water, 100 mL of decane, and 10 g of solid CA1·H2O was filtered by suction to remove both water and decane from the solid CA1·H2O. At this time, 95.0 g of water (95.7% of the total water) and 67.3 g of decane (93.5% of the total decane) were removed from the solid CA1·H2O. Since both water and decane were removed to roughly equal amounts, it was found that simple suction filtration preferentially removes only water, making it difficult to replace water with decane.

[0084] [Experimental Example B15] To solve the problem in [Experimental Example B14], a chromatographic tube was used to push out only the aqueous layer from a mixture of 100 mL of decane, 100 mL of water, and 10 g of solid CA1·H2O using a plug flow method. After standing for 1 hour, 88.5 g of water (83.2% of the total water volume) was discharged by gravity alone, and not a single drop of decane was discharged. From this, it was found that the plug flow method is a promising means of replacing water with decane.

[0085] [Experimental Example C11] (Process (C1)) The following experimental example was conducted regarding process (C1), namely the release of CO2.

[0086] In this experiment, under atmospheric pressure, CO2 is released by heating a decane solvent, aqueous solvent, or IPDA solvent containing solid CA1·H2O, thereby regenerating IPDA from the solid CA1·H2O. The experimental procedure is as follows. 1. Add a suspension containing 10 g of CA1·H2O solid and 100 mL of decane solvent, aqueous solvent, or IPDA solvent to a three-necked flask. Record the temperature inside the flask using a data logger. Stir the contents of the three-necked flask. 2. Set the oil bath temperature to 150°C. 3. Sweep gas N2 is blown in at 450 mL / min, and the CO2 concentration of the outlet gas from the three-necked flask is monitored using a Vaisala CARBOCAP® GMP251 CO2 probe. 4. Once the oil bath temperature reaches 150°C, immerse the three-necked flask up to its neck. 5. The experiment is terminated when CO2 emission stabilizes, based on real-time measurement data from the CO2 probe.

[0087] Figures 1 and 2 show the time-series data of the solvent temperature inside the three-necked flask and the CO2 concentration in the outlet gas obtained from the experiment. Figure 1 compares the experimental results for the decane solvent case and the aqueous solvent case, and Figure 2 compares the experimental results for the decane solvent case and the IPDA solvent case. IPDA was used as the solvent in the experiment because, with aqueous solvent, the boiling point of water is 100°C, so the temperature rise stagnation could not be observed. Therefore, the same experiment was conducted with IPDA as the solvent to observe this.

[0088] When using decane solvent, a temperature rise plateau associated with a phase transition was observed at approximately 120°C when heated to 150°C (Figures 1 and 2). On the other hand, no temperature rise plateau associated with a phase transition was observed when using IPDA solvent (Figure 2). Therefore, it is considered that the temperature at which IPDA is regenerated from solid CA1·H2O is lower in decane solvent than in IPDA solvent. When using aqueous solvent, the temperature rise stopped at 100°C, the boiling point of water, so the CO2 release rate was lower compared to when using decane solvent (Figure 1). However, in aqueous solvent, after the peak of CO2 release, the rate of decrease in CO2 concentration slowed down, and it was found that it took a considerable amount of time for the CO2 concentration to become zero. The CO2 release rate in the case of decane solvent was faster than that in the case of IPDA solvent, and the CO2 concentration became almost zero immediately after the peak of CO2 release, indicating that nonpolar solvents are superior to polar solvents in terms of regeneration (Figure 2).

[0089] When IPDA was used as the solvent, the regenerated CO2 and volatile IPDA recombined upon heating, resulting in a white deposit or transparent crystals adhering to the top of the three-necked flask. On the other hand, when decane was used as the solvent, no such white deposits due to recombination were observed on the top of the three-necked flask. This is thought to be because nonpolar solvents inhibit the absorption, i.e., recombination, of CO2 compared to polar solvents. Thus, from the perspective of practical processes, decane solvent was found to be superior to IPDA solvent.

[0090] [Experimental Example] (Process (D1)) The following experiment was conducted regarding step (D1), which involves replacing the solvent from decane to water in a decane solution containing IPDA.

[0091] [Experimental Example D11] When 100 mL of water was added to a completely mixed solution of 100 mL of IPDA and 100 mL of decane, it was observed that the solution separated into two layers: an upper decane layer and a lower aqueous layer. It appears that the IPDA is distributed and dissolved in each layer. When only the aqueous layer was separated using a separatory funnel and its weight was measured, it was found to be 186.4 g. Therefore, it was found that 98.0% by weight of the IPDA that was completely mixed with decane migrated to the aqueous layer. From this, it can be concluded that IPDA is soluble in both polar and nonpolar solvents, but has a higher affinity for polar solvents. Due to this property, it is possible to easily replace decane containing IPDA with water.

[0092] [Experimental Example D12] We investigated whether nonpolar solvents other than decane, including IPDA, and the polar solvent acetone, could be easily replaced with water by adding water, using the following procedure.

[0093] • Experimental procedure 1. Add 2 ml each of the nonpolar solvents toluene, cyclopentane, hexane, heptane, n-octane, and decane to 2 ml of IPDA. Mix all solvents thoroughly. 2. Add 2 ml of water to the sample and check if it separates. 3. Blow in more CO2 and check if a solid is formed.

[0094] Observing these results, it was found that in the case of acetone, a polar solvent, no two phases were formed when water was added. In the case of nonpolar solvents, water always settled at the bottom, forming two phases. The larger volume was the lower water tank, indicating that in both cases, IPDA was largely distributed in the nonpolar solvent.

[0095] Each sample, except for the acetone sample, was checked for turbidity by blowing CO2 into it. This blowing test confirmed that the IPDA was not deactivated.

[0096] [Examples] (1) Process (A1), i.e., the CO2 absorption process: IPDA was used as the amine compound, and water as the polar solvent. 600 g of an IPDA aqueous solution containing 10 wt% IPDA was prepared and used as the CO2 absorbent. Air (CO2 concentration 0.04 vol%) was aerated through the absorbent at 500 mL / min under normal temperature and pressure conditions using a compressor to absorb CO2. Approximately 102 hours after the start of aeration, the IPDA aqueous solution became cloudy and precipitated due to the solid precipitation of CA1·H2O. It was confirmed that the total amount of CO2 in the supplied air was absorbed at least up to 212 hours after the start of aeration by measuring the total organic carbon (TOC) of the CO2 absorbent. The total amount of CO2 absorbed by the CO2 absorbent after 212 hours was measured to be approximately 1 / 3 of the maximum absorption amount, since it is known that 1 mole of CO2 is absorbed per mole of IPDA. Therefore, approximately three times 212 hours, or about 650 hours, is a guideline for the aeration time required for CO2 absorption saturation.

[0097] (2) Step (B1), namely the substitution step from a polar solvent to a nonpolar solvent: In step (A1), 500 mL of decane, a nonpolar solvent, is added to the polar suspension containing the carbamic acid derivative precipitated in the polar solvent in a suspended state, and the mixture is stirred with a stirrer at 200 RPM for about 1 minute. Upon standing, the mixture separates into a decane layer (nonpolar solvent) at the top and an aqueous layer (polar solvent) at the bottom, with the CA1·H2O solid suspended at the interface. This decane-CA1·H2O solid-water mixture is placed in a chromatography tube, and only the water from the lower layer is drained. This single operation removes approximately 83 wt% of the total water volume without losing almost any decane. After this, the mixture is stirred again, and the operation of draining the water in a plug-flow manner in the chromatography tube after the decane-water phase separation is repeated twice. Calculations show that more than 99 wt% of the water can be removed, completing the solvent replacement from water to decane.

[0098] For comparison, when regenerating CO2 using an aqueous solvent, it is desirable to remove water from the CA1·H2O solid, but this requires a complicated and energy-intensive process such as dehydration using a filter press. An example of a commercially available filter press catalog value is approximately 56L of cake capacity and 4.8m² of dehydration area. 2 The required power is a total of 2.3 kW, consisting of a 1.5 kW dewatering pump, a 0.4 kW hydraulic pump, and a 0.4 kW plate motor. When using decane solvent for regeneration, this input energy can be almost eliminated by using the aforementioned water-to-decane substitution method.

[0099] (3) Process (C1), i.e., the CO2 regeneration process: The decane containing solid CA1·H2O, obtained by replacing water with decane in process (B1), is heated to 120°C under atmospheric pressure while being stirred with a stirrer to regenerate the solid CA1·H2O into IPDA and CO2. CO2 bubbles are generated when the decane temperature reaches 84.9°C, and the bubbling becomes more vigorous at 116°C, so 120°C is considered to be a suitable temperature for CO2 regeneration.

[0100] When 100 mL of decane and 10 g of solid CA1·H2O were heated in an oil bath at 150°C under atmospheric pressure, 0.93 g of CO2 was regenerated in 25 minutes, during which time the temperature was raised from 25°C to 145°C. The specific gravity of decane was 0.73 g / cc, the molecular weight of decane was 142.29, and the specific heat of decane was 315.46 JK-1 mol. -1 Therefore, the energy invested for regeneration can be estimated at 1.9 kJ.

[0101] For comparison, when considering the case of water, under the same pressure, heating conditions, the same weight of solid CA1·H2O, and the same volume of solvent, it took more than 80 minutes to regenerate 0.93 mol of CO2. Therefore, by approximation, multiplying 1.94 kJ by the value 80 / 25, the energy input for regeneration is 6.1 kJ, which is more energy required than in the case of decane.

[0102] When comparing the amount of CO2 released over the same 25-minute period, the decane solvent released 0.93 mol, while the aqueous solvent released 0.46 mol, indicating that the decane solvent can regenerate approximately twice as much CO2 in the same amount of time.

[0103] (4) Step (D1), namely the substitution step from a nonpolar solvent to a polar solvent: Water is added to the decane solution of IPDA generated in step (C1) to move the IPDA from the decane phase to the aqueous phase and separate the decane phase. Specifically, an amount of water equivalent to that used in the first step (A1), i.e., 540g, is added to the decane containing IPDA. Before adding water, the IPDA and decane are completely mixed, but after adding water and stirring for about 1 minute, stirring is stopped and the mixture is allowed to stand for 1 minute, separating it into an upper decane layer and a lower aqueous layer. Because IPDA is hydrophilic, this operation immediately distributes 98.0 wt% of the IPDA into the aqueous layer, and the remaining 2.0 wt% into the decane layer. Using a chromatography tube, only the lower IPDA aqueous solution could be isolated.

[0104] (5) Process (E1): The aqueous solution of IPDA obtained in step (D1) was returned to step (A1), and the nonpolar solvent decane was returned to step (B1), and steps (A1) to (D1) were repeated multiple times. [Industrial applicability]

[0105] This invention can be used in all areas of CO2 fixation, CO2 capture, and CO2 transport.

Claims

1. Step (A1) involves absorbing carbon dioxide into an amine compound polar solution containing an amine compound represented by the following formula (1) and a polar solvent, thereby precipitating a solid reaction product of the amine compound and carbon dioxide in the amine compound polar solution, and obtaining a polar reaction product which is a polar suspension or slurry obtained therefrom. Step (B1) involves treating the polar reactant obtained in step (A1) with a nonpolar solvent, removing the polar solvent, and obtaining a nonpolar reactant that is a nonpolar suspension or slurry containing the solid reactant and the nonpolar solvent. Step (C1) involves heating the nonpolar reactant obtained in step (B1) under pressure, atmospheric pressure, or reduced pressure, separating and recovering carbon dioxide, regenerating the amine compound from the nonpolar reactant, and obtaining a nonpolar amine compound solution. A method for separating and recovering carbon dioxide, comprising: step (D1) treating the nonpolar solution of the amine compound obtained in step (C1) with a polar solvent to replace the solvent and obtain a polar solution of the amine compound. 【Chemistry 1】 However, in the formula, m is 0 or 1; R １ and R ２ are each independently an alkyl group, an alkoxy group, a carboxy group, an alkyloxycarbonyl group, a formyl group, an alkylcarbonyl group, an alkylthio group, a sulfo group, an alkyloxysulfonyl group, a nitro group, a hydroxyl group, a thiol group, a cyano group or a halogen atom, and the alkyl group may have a substituent; p １ and p ２ are each independently 1 or 2; when m is 0, q １ is an integer from 0 to 11, provided that p １ + q １ is 12 or less; when m is 1, q １ is an integer from 0 to 10, provided that p １ + q １ is 11 or less; q ２ is an integer from 0 to 10, and when q １ is an integer of 2 or more, two or more R １ may be the same as or different from each other, and when q ２ is an integer of 2 or more, two or more R ２ may be the same as or different from each other, and when q １ is an integer of 2 or more and two or more R １ is the alkyl group which may have a substituent, then the two or more R １ may be bonded to each other to form a ring, and when q ２ is an integer of 2 or more and two or more R ２ is the alkyl group which may have a substituent, then the two or more R ２ may be bonded to each other to form a ring. However, this excludes the case where m is 0, p １ is 2, and the two amino groups to which p １ is attached are arranged in the meta position to each other.

2. The method for separating and recovering carbon dioxide according to claim 1, wherein the amine compound polar solution obtained in step (D1) is used as the amine compound polar solution in step (A1), and step (E1) is repeated from step (A1) to step (D1).

3. The method for separating and recovering carbon dioxide according to claim 1, wherein in step (B1), a suspension or slurry is used as the polar reactant, the nonpolar solvent is mixed thereto, and then the polar solvent is separated and removed to obtain the nonpolar reactant.

4. In step (C1), the nonpolar reactant is heated to 100-150°C under a pressure of atmospheric pressure to 20 kPa to produce CO ２ A method for separating and recovering carbon dioxide according to claim 1, comprising releasing the amine compound to obtain a nonpolar solution of the amine compound.

5. The method for separating and recovering carbon dioxide according to claim 1, wherein in step (D1), a polar solvent is mixed with the nonpolar solution of the amine compound to transfer the amine compound to the polar solvent, and then the nonpolar solvent is separated and recovered to obtain the polar solution of the amine compound.

6. The method for separating and recovering carbon dioxide according to claim 1, wherein the polar solvent is at least one selected from the group consisting of water, methanol, ethanol, acetone, acetic acid, ammonia, dimethyl sulfoxide (DMSO), and sulfuric acid.

7. The method for separating and recovering carbon dioxide according to claim 1, wherein the nonpolar solvent is at least one selected from the group consisting of hexane, octane, nonane, decane, benzene, toluene, xylene, diethyl ether, and cyclohexane.

8. The method for separating and recovering carbon dioxide according to claim 1, wherein the amine compound comprises isophorone diamine (IPDA).

9. The method for separating and recovering carbon dioxide according to claim 8, wherein the solid reactant includes solid carbamic acid.

10. A method for separating and recovering carbon dioxide according to claim 1, comprising the step (A1) being carried out at a first location, the step (F1) being transported to a second location where carbon dioxide is regenerated, and the step (C1) being carried out at the second location.

11. A method for separating and recovering carbon dioxide according to claim 1, comprising the steps (A1) and (B1) above to be performed at a first location, the step (G1) of transporting the obtained nonpolar reaction product to a second location where carbon dioxide is regenerated, and the step (C1) above to be performed at the second location.

12. A method for separating and recovering carbon dioxide according to claim 10, comprising the step (H1) of transporting the nonpolar solution of the amine compound obtained in step (C1) or the polar solution of the amine compound obtained in step (D1) from the second location to the first location, and repeating steps (A1) to (D1), steps (F1) and (H1).

13. A method for separating and recovering carbon dioxide according to claim 11, comprising step (H1) of transporting the nonpolar solution of the amine compound obtained in step (C1) or the polar solution of the amine compound obtained in step (D1) from the second location to the first location, wherein if the nonpolar solution of the amine compound obtained in step (C1) is transported, after performing step (D1), steps (A1) to (D1), steps (G1) and (H1) are repeated.

14. The method for separating and recovering carbon dioxide according to any one of claims 10 to 13, wherein in the step (C1) performed at the second location, renewable energy is used for the heating step.

15. A method for separating and recovering carbon dioxide according to any one of claims 10 to 13, wherein the amine compound used is an amine compound containing isophorone diamine (IPDA), and the polar solvent used is water.

16. The method for separating and recovering carbon dioxide according to any one of claims 10 to 13, wherein at least one selected from the group consisting of hexane, octane, nonane, decane, benzene, toluene, xylene, diethyl ether, and cyclohexane is used as the nonpolar solvent.

17. A method for regenerating carbon dioxide, comprising: absorbing carbon dioxide into a polar solution of an amine compound containing an amine compound including isophorone diamine (IPDA) and a polar solvent; obtaining a polar reaction product, which is a polar suspension containing solid carbamic acid, a reaction product of the amine compound and carbon dioxide, or a slurry obtained therefrom; and regenerating carbon dioxide from this polar reaction product. The polar reactant is treated with a nonpolar solvent, and the polar solvent is removed to obtain a nonpolar reactant which is a nonpolar suspension or slurry containing the reactant and the nonpolar solvent. A method for regenerating carbon dioxide, comprising heating the obtained nonpolar reactant under pressure, atmospheric pressure, or reduced pressure to separate and recover carbon dioxide, regenerating the amine compound from the nonpolar reactant, and obtaining a nonpolar solution of the amine compound.

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