Carbon dioxide separation and recovery method and carbon dioxide regeneration method

Abstract

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

Description

[Technical Field]

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

[0002] According to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC), in order to limit the increase in global average temperature caused by anthropogenic greenhouse gas emissions to within 1.5°C above pre-industrial levels, global carbon dioxide (CO2) emissions must be reduced to net zero by 2050. This has made the development and social implementation of low-energy-cost CO2 separation and capture from CO2 emission sources or the atmosphere an urgent issue. New methods have been proposed for CO2 separation and capture, including thermal swing and pressure swing, and more recently electrical swing, humidity swing, and pH swing.

[0003] It is known from Patent Document 1 that by using a CO2 absorbent / release agent that changes phase from liquid to solid upon absorbing CO2 in a thermal swing, it is possible to reduce the energy loss due to the sensible heat and latent heat of vaporization of the solvent when the CO2 absorbent / release agent is heated to capture CO2. An example of a problem in which energy loss due to the sensible heat and latent heat of vaporization of the solvent occurs in a typical amine process used in combustion exhaust gas treatment. To mitigate the corrosiveness of the amine, the amine concentration must be kept at, for example, 30 wt% or less in aqueous solution, which requires a large amount of energy input to heat the water. Furthermore, if the temperature of the thermal swing is significantly higher than room temperature, this can increase the energy input.

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

[0005] [ka]

[0006] [ka]

[0007] [ka]

[0008] [ka]

[0009] In an industrial-scale process, 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 form CA1·H2O (see (4) above). The pressure and temperature required to extract CO2 from CA1·H2O in an IPDA aqueous solution are, for example, about 120°C at 20 kPa and about 140°C at atmospheric pressure, requiring a fairly long regeneration process.

[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 form of CA1 rather than CA1·H2O, which may make it possible to lower the temperature required to release CO2 than CA1·H2O. However, when attempting to absorb CO2 from exhaust gas or air, the inclusion of water is unavoidable.

[0011] Because the precipitated CA1 or CA1·H2O is in the form of fine particles, the polar solvent after CO2 absorption is suspended in these particles. To separate the solvent, a solid-liquid separation process such as filtration or a filter press must be introduced, which increases process costs and energy costs. There is a need to transfer the CO2 absorption / release agent between the absorption process and the capture process in a state that makes it easier to handle. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] Patent No. 7441557 Summary of the Invention [Problem to be solved by the invention]

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

[0014] Furthermore, the process of transferring the suspended CO2 absorbent / release agent after CO2 absorption to the CO2 capture process involves a batch process such as dehydration (desolventization) using a filter press, which makes the entire process inefficient. Simplifying the process is an issue.

[0015] The present invention aims to reduce the energy required to regenerate a CO2 absorption / release agent in a carbon dioxide separation and capture method that uses an amine compound to absorb and capture carbon dioxide, and to simplify the process between the absorption step and the capture step. [Means for solving the problem]

[0016] In order to solve the above-mentioned problems, the inventors discovered that by using solvents with different polarities in the carbon dioxide absorption step and the carbon dioxide capture step, it is possible to reduce the energy required for regenerating the CO2 absorption / release agent and further simplify the process between the absorption step and the capture step, and thus completed the present invention.

[0017] An embodiment of the present invention that achieves the above object resides in a method for separating and recovering carbon dioxide, comprising: a step (A1) of 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 reactant of the amine compound and the carbon dioxide in the amine compound polar solution, thereby obtaining a polar reactant in the form of a polar suspension or a slurry obtained therefrom; a step (B1) of treating the polar reactant obtained in the step (A1) with a nonpolar solvent and removing the polar solvent to obtain a nonpolar reactant in the form of a nonpolar suspension containing the solid reactant and the nonpolar solvent or a slurry obtained therefrom; a step (C1) of heating the nonpolar reactant obtained in the step (B1) under increased pressure, normal pressure, or reduced pressure, to separate and recover carbon dioxide and regenerate the amine compound from the nonpolar reactant, thereby obtaining an amine compound nonpolar solution; and a step (D1) of treating the amine compound nonpolar solution obtained in the step (C1) with a polar solvent to replace the solvent, thereby obtaining an amine compound polar solution.

[0018] [ka]

[0019] 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; p1 and p2 are each independently 1 or 2; when m is 0, q1 is an integer of 0 to 11, with the proviso that p1+q1 is 12 or less, and when m is 1, q1 is an integer of 0 to 10, with the proviso that p1+q1 is 11 or less and q2 is an integer of 0 to 10, and when q1 is an integer of 2 or more, two or more R 1 may be the same or different, and when q2 is an integer of 2 or more, two or more R 2may be the same or different, q1 is an integer of 2 or more, and two or more R 1 is the alkyl group which may have a substituent, the two or more R 1 may be bonded to each other to form a ring, q2 is an integer of 2 or more, and two or more R 2 is the alkyl group which may have a substituent, the two or more R 2 may be bonded to each other to form a ring, provided that m is 0 and p 1 is 2 and p 1 Except when the two amino groups marked with are positioned meta to each other.

[0020] A second aspect of the present invention is the method for separating and recovering carbon dioxide according to the above aspect, wherein the amine compound polar solution obtained in the step (D1) is used as the amine compound polar solution in the step (A1), and step (E1) is performed in which the steps (A1) to (D1) are repeated.

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

[0022] A fourth aspect of the present invention is the method for separating and recovering carbon dioxide according to the above aspect, wherein in the step (C1), the nonpolar reactant is heated to 100 to 150°C under a pressure of from atmospheric pressure to 20 kPa to release CO2, thereby obtaining the nonpolar solution of the amine compound.

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

[0024] A sixth aspect of the present invention is the method for separating and recovering carbon dioxide according to the above aspects, 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 the method for separating and recovering carbon dioxide according to the above aspect, wherein the non-polar 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 includes isophoronediamine (IPDA).

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

[0028] A tenth aspect of the present invention is a method for separating and recovering carbon dioxide according to any of the above aspects, further comprising a step (F1) of carrying out step (A1) at a first location and transporting the resulting polar reactant to a second location where carbon dioxide is regenerated, and wherein step (C1) is 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 any of the above aspects, comprising a step (G1) of carrying out the steps (A1) and (B1) at a first location and transporting the resulting non-polar reactant to a second location where carbon dioxide is regenerated, and wherein the step (C1) is carried out at the second location.

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

[0031] A thirteenth aspect of the present invention is a method for separating and recovering carbon dioxide according to any of the above aspects, further comprising a step (H1) of transporting the nonpolar amine compound solution obtained in the step (C1) or the polar amine compound solution obtained in the step (D1) from the second location to the first location, and when the nonpolar amine compound solution obtained in the step (C1) has been transported, the steps (A1) to (D1), and the steps (G1) and (H1) are repeated after the step (D1) is carried out.

[0032] A fourteenth aspect of the present invention resides in the method for separating and capturing carbon dioxide according to any of the preceding aspects, wherein in the step (C1) carried out at the second location, renewable energy is used for the heating step.

[0033] A fifteenth aspect of the present invention is the method for separating and recovering carbon dioxide according to the above aspects, wherein the amine compound is an amine compound containing isophoronediamine (IPDA), and the polar solvent is water.

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

[0035] A seventeenth aspect of the present invention is a method for regenerating carbon dioxide, which comprises absorbing carbon dioxide into an amine compound polar solution containing an amine compound including isophoronediamine (IPDA) and a polar solvent to obtain a polar reactant, which is a polar suspension containing solid carbamic acid, which is a reaction product of the amine compound and the carbon dioxide, or a slurry obtained therefrom, and regenerating carbon dioxide from this polar reactant, wherein 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 containing the reactant and the nonpolar solvent or a slurry obtained therefrom, and the obtained nonpolar reactant is heated under normal pressure or reduced pressure to separate and recover carbon dioxide, thereby regenerating the amine compound from the nonpolar reactant and obtaining an amine compound nonpolar solution. [Effects of the Invention]

[0036] According to the present invention, a novel CO2 separation and capture system is provided, which can reduce the amount of energy input by lowering the regeneration temperature when regenerating CO2 from the reactant that absorbed CO2. Furthermore, even if the reactant is regenerated without being separated, the amount of energy input can be sufficiently reduced. [Brief explanation of the drawings]

[0037] [Figure 1] This graph compares the temperature of the solvent and the CO2 concentration in the outlet gas over time when a decane solvent containing solid CA1·H2O or a water solvent is heated. [Figure 2] This graph compares the solvent temperature and CO2 concentration in the outlet gas over time when decane solvent or IPDA solvent containing solid CA1·H2O is heated. DETAILED DESCRIPTION OF THE INVENTION

[0038] The present invention will now be described in further detail. The method for separating and capturing carbon dioxide of the present invention includes the steps of: obtaining a polar suspension by 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; treating the polar suspension obtained in the step (A1) with a nonpolar solvent and removing the polar solvent to obtain a nonpolar suspension containing the reaction product and the nonpolar solvent; heating the nonpolar suspension obtained in the step (B1) under atmospheric pressure or under reduced pressure to release CO2 and regenerate the reaction product into the amine compound, thereby obtaining a nonpolar solution of the amine compound; and substituting the nonpolar solvent in the nonpolar solution of the amine compound obtained in the step (C1) with the polar solvent to obtain the carbon dioxide absorbent.

[0039] Here, the amine compound of the following formula (1) is a known compound also disclosed in JP 2024-075122 A, which was previously filed by the present applicant, and is as disclosed below.

[0040] [ka]

[0041] 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; p1 and p2 are each independently 1 or 2; when m is 0, q1 is an integer of 0 to 11, with the proviso that p1+q1 is 12 or less, and when m is 1, q1 is an integer of 0 to 10, with the proviso that p1+q1 is 11 or less and q2 is an integer of 0 to 10, and when q1 is an integer of 2 or more, two or more R 1 may be the same or different, and when q2 is an integer of 2 or more, two or more R2 may be the same or different, q1 is an integer of 2 or more, and two or more R 1 is the alkyl group which may have a substituent, the two or more R 1 may be bonded to each other to form a ring, q2 is an integer of 2 or more, and two or more R 2 is the alkyl group which may have a substituent, the two or more R 2 may be bonded to each other to form a ring, provided that m is 0 and p 1 is 2 and p 1 Except when the two amino groups marked with are positioned meta to each other.

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

[0043] [ka]

[0044] In the formula, R 11 , R 12 , R 13 and R 21 are each independently an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a carboxy group, an alkyloxycarbonyl group having 2 to 11 carbon atoms, a formyl group, an alkylcarbonyl group having 2 to 11 carbon atoms, an alkylthio group having 1 to 10 carbon atoms, a sulfo group, an alkyloxysulfonyl group having 1 to 10 carbon atoms, 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 the substituent; 11 and q 12 are each independently an integer of 0 to 6, and q 11 is an integer of 2 or more, two or more R 11 may be the same or different, and q 12 is an integer of 2 or more, two or more R 12 may be the same or different, and q11 is an integer of 2 or more, and there are two or more R 11 is the alkyl group which may have an amino group as the substituent, the two or more R 11 may be bonded to each other to form a ring, and q 12 is an integer of 2 or more, and there are two or more R 12 is the alkyl group which may have an amino group as the substituent, the two or more R 12 may be bonded to each other to form a ring; q 13 and q 21 are each independently an integer of 0 to 4, and q 13 is an integer of 2 or more, two or more R 13 may be the same or different, and q 21 is an integer of 2 or more, two or more R 21 may be the same or different, and q 13 is an integer of 2 or more, and there are two or more R 13 is the alkyl group which may have an amino group as the substituent, the two or more R 13 may be bonded to each other to form a ring, and q 21 is an integer of 2 or more, and there are two or more R 21 is the alkyl group which may have an amino group as the substituent, the two or more R 21 may be bonded to each other to form a ring, except for the case where, in the formula (12A), two amino groups directly bonded to carbon atoms constituting the cyclohexane ring skeleton are positioned at meta positions relative to each other.

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

[0046] [ka]

[0047] In the formula, R 111 , R 121 , R 122 , R 131 and R 211 are each independently an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, an alkyloxycarbonyl group having 2 to 6 carbon atoms, a formyl group, an alkylcarbonyl group having 2 to 6 carbon atoms, an alkylthio group having 1 to 5 carbon atoms, a hydroxyl group, a thiol group, a cyano group or a halogen atom, and the alkyl group may have an amino group as the substituent; 111 , q 121 and q 122 are each independently an integer of 0 to 4, and q 111 is an integer of 2 or more, two or more R 111 may be the same or different, and q 121 is an integer of 2 or more, two or more R 121 may be the same or different, and q 122 is an integer of 2 or more, two or more R 122 may be the same or different, and q 111 is an integer of 2 or more, and there are two or more R 111 is the alkyl group which may have an amino group as the substituent, the two or more R 111 may be bonded to each other to form a ring, and q 121 is an integer of 2 or more, and there are two or more R 121 is the alkyl group which may have an amino group as the substituent, the two or more R 121 may be bonded to each other to form a ring, and q 122 is an integer of 2 or more, and there are two or more R 122 is the alkyl group which may have an amino group as the substituent, the two or more R 122 may be bonded to each other to form a ring; q 131 and q 211 are each independently an integer of 0 to 2, and q 131 If is 2, then two R 131may be the same or different, and q 211 If is 2, then two R 211 may be the same or different, and q 131 is 2 and there are two R 131 is the alkyl group which may have an amino group as the substituent, the two R 131 may be bonded to each other to form a ring, and q 211 is 2 and there are two R 211 is the alkyl group which may have an amino group as the substituent, the two R 211 may be bonded to each other to form a ring.

[0048] In step (A1) of the present invention, the amine compound as described above is in a liquid state, and this amine compound is mixed with a polar solvent to prepare a mixed liquid 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 the amine compound and a compatible solvent mixed together.

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

[0050] Step (A1) utilizes the property of the amine compound to solidify upon reaction with carbon dioxide. That is, carbon dioxide is absorbed by contacting a liquid carbon dioxide absorbent with air or a gas containing carbon dioxide, and the reaction product of the amine compound and carbon dioxide is precipitated 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 the contact of the carbon dioxide absorbent with carbon dioxide is preferably carried out under conditions that facilitate 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 temperature during contact as low as possible. As the amine compound that is easily precipitated, it is preferable to use a diamine, but even in the case of a monoamine, it is sufficient to maximize the concentration of the amine compound and keep the temperature during the reaction 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 amine compound concentration of 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. 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 the present invention, in step (B1), this polar suspension or slurry is treated with a nonpolar solvent to remove the polar solvent, resulting in a nonpolar suspension containing the reactant and the nonpolar solvent. This treatment is carried out based on the finding that by mixing a nonpolar solvent with a polar suspension in which a solid carbamic acid derivative is suspended, stirring, and allowing the mixture to stand, the solid carbamic acid derivative migrates to the vicinity of the nonpolar solvent phase. That is, this treatment is carried out based on the finding that a suspension phase is formed between the polar solvent phase and the nonpolar solvent phase, and removing the polar solvent yields a nonpolar suspension. That is, rather than 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 the solid carbamic acid derivative is suspended can be obtained by mixing the polar suspension and the nonpolar solvent. Of course, the substitution can also be carried out by adding a nonpolar solvent to a slurry or cake (both of which are sometimes simply referred to as "slurry") obtained by removing the solvent from a polar suspension containing a carbamic acid derivative using a cyclone, and then removing the polar solvent. In any case, this step (B1) is an important point of the present invention.

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

[0056] The second important point of the present invention is that the input energy required to release carbon dioxide from a nonpolar suspension and regenerate an amine compound is significantly smaller than the input energy required to regenerate an amine compound from a polar suspension. That is, when regenerating an amine compound from a polar suspension such as water, it is known that after the peak of carbon dioxide release has passed, the carbon dioxide release rate decreases and it takes time for the carbon dioxide content to become almost zero. However, when carbon dioxide is released from a nonpolar suspension, the carbon dioxide content becomes almost zero immediately after the peak of release has passed, resulting in a significant reduction in the input energy.

[0057] The reason why less energy is required to release carbon dioxide from a non-polar suspension and regenerate the amine compound is that the specific heat of a non-polar suspension is smaller than that of a polar suspension. However, it has also been found through experiments that the temperature at which carbon dioxide is released from a carbamic acid derivative is lower in a non-polar solvent than in a polar solvent, and the present invention was completed based on this finding.

[0058] In this step (C1), the nonpolar suspension is heated under pressure, that is, at normal pressure to 20 kPa, at 100 to 150°C, preferably at normal 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 to obtain a carbon dioxide absorbent for step (A1), which can be used in the subsequent step (A1).

[0060] The present 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 the mixture is allowed to stand, the amine compound migrates from the nonpolar solvent to the polar solvent, forming a polar solvent solution. That is, by mixing and stirring a polar solvent with a nonpolar solution and allowing the mixture to stand, the amine compound migrates to the polar solvent, forming a polar solution, and the initial carbon dioxide absorbent can be regenerated, which is the third important point of the present invention.

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

[0062] The carbon dioxide separation and capture method of the present invention is a novel CO2 separation and capture system comprising the above-mentioned steps (A1) to (D1), in which CO2 is absorbed into a carbon dioxide absorbent containing an amine compound, thereby lowering the regeneration temperature when regenerating CO2 from a carbamic acid derivative, which is a solid reactant that has reacted with CO2, thereby reducing the amount of energy input. Furthermore, even if the reactant is regenerated without being separated, the amount of energy input is sufficiently reduced. Furthermore, the nonpolar solvent in the nonpolar solution of the amine compound remaining after regenerating carbon dioxide can be easily replaced with a polar solvent, allowing the original carbon dioxide absorbent to be regenerated. This carbon dioxide absorbent can be used in step (A1) (step (E1)), thereby enabling steps (A1) to (D1) to be repeatedly performed.

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

[0064] Alternatively, step (A1) and step (B1) may be carried out at a first location, and step (G1) may be included in which the resulting non-polar reactant is transported by tanker, truck, or the like to a second location where carbon dioxide is regenerated, and step (C1) may be carried out at the second location. Here, the second location is, for example, a location where renewable energy can be used, and by carrying out the work at the second location, it is possible to achieve overall energy savings.

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

[0067] In any event, in the method for separating and recovering carbon dioxide, carbon dioxide is absorbed into an amine compound polar solution containing an amine compound including isophoronediamine (IPDA) and a polar solvent to obtain a polar reactant, which is a polar suspension containing solid carbamic acid, which is a reaction product of the amine compound and the carbon dioxide, or a slurry obtained therefrom, and carbon dioxide is separated and recovered from this polar reactant.The important points of this method are that 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 containing the reactant and the nonpolar solvent or a slurry obtained therefrom, and the obtained nonpolar reactant is heated under pressure, normal pressure, or reduced pressure to separate and recover carbon dioxide, thereby regenerating the amine compound from the nonpolar reactant and obtaining an amine compound nonpolar solution. [Example]

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

[0069] In the experiments and examples, isophoronediamine (IPDA) was used as the amine compound, and carbamic acid (CA1) and its hydrate (CA1·H2O) were used as the reaction products between this and carbon dioxide. In the examples, when isophoronediamine (IPDA) reacts with carbon dioxide, in addition to carbamic acid (CA1) and its hydrate (CA1·H2O), dicarbamic acid (CA2) and its hydrate may also be produced, but this has not been confirmed. The chemical formulas of these compounds are shown below.

[0070] [ka]

[0071] [ka]

[0072] [ka]

[0073] [ka]

[0074] [ka]

[0075] [Experimental Example] Experiments were conducted on each step of the carbon dioxide separation and capture method as follows:

[0076] [Experimental Example A11] (Step (A1)) Step (A1), i.e., the CO2 absorption step, was carried out as follows. When 100% CO2 gas was bubbled into a 20 wt% clear IPDA aqueous solution, the solution became cloudy after 33 minutes due to the precipitation of solid CA1·H2O, and after 48 minutes the entire solution became cloudy and turned into an opaque suspension. When left to stand, the solid CA1·H2O precipitated at the bottom of the solution.

[0077] [Experimental Examples B11 to B15] (Step (B1)) The following experiment was carried out for step (B1), i.e., step (B1) of replacing water in a polar suspension containing CA1·H2O solid with decane to obtain a non-polar suspension.

[0078] [Experimental Example B11] When 10 g of CA1·H2O solids, 100 mL of decane, and 100 mL of water were placed in a 300 mL beaker and stirred for 2-3 minutes, the mixture was allowed to stand. The CA1·H2O solids floated to the interface between the decane and water layers, forming a three-layer structure consisting of a decane layer, a CA1·H2O solid layer, and water from top to bottom. As shown in [Experiment A11], CA1·H2O solids would normally precipitate in water, so this unusual phenomenon is thought to be due to the effect of decane. The underlying mechanism is that the lipophilicity of the CA1·H2O solids causes the decane layer to reduce their specific gravity, allowing them to float in water. This property allows the CA1·H2O solids to be easily scooped out with a mesh like a tea strainer or by draining the water layer from the bottom, facilitating the replacement of the solvent in the CA1·H2O solids with decane.

[0079] [Experimental Example B12] This experiment was conducted to verify the use of a centrifuge in step (B1). Centrifuging is also effective in quickly eliminating bubbles that may be generated by excessive stirring during the process of step (B1) and in shortening the time required for separation.

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

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

[0082] A mixture of 100 mL of decane, 100 mL of water, and 10 g of CA1·H2O solids was filtered three or four times using a tea strainer with a mesh size of approximately 1 mm. It was found that most of the CA1·H2O solids were captured by the strainer, allowing the separation of only the liquid. The water-decane mixture that passed through the strainer was separated in a separatory funnel and weighed. It contained 79.4 g of water (81.2% of the total water) and 35.3 g of decane (49.4% of the total decane). These results also indicate that the CA1·H2O solids tend to cling to decane more than water, and that simply mixing the CA1·H2O solids with water and decane completes the replacement of water with decane to a certain extent in the CA1·H2O solids.

[0083] [Experimental Example B14] A mixture of 100 mL of water, 100 mL of decane, and 10 g of CA1·H2O solid was filtered under suction, and both water and decane were removed from the CA1·H2O solid. In this case, 95.0 g of water (95.7% of the total amount of water) and 67.3 g of decane (93.5% of the total amount of decane) were removed from the CA1·H2O solid. Because both water and decane were removed to the same extent, it was found that simple suction filtration is unable to preferentially remove water and replace it with decane.

[0084] [Experimental Example B15] To solve the problem in [Experimental Example B14], a chromatography tube was used to extract only the water layer from a mixture of 100 mL of decane, 100 mL of water, and 10 g of solid CA1·H2O using plug flow. After leaving the mixture to stand for one hour, 88.5 g of water (83.2% of the total water amount) was extracted by gravity alone, and not a single drop of decane was extracted. This indicates that the plug flow method is a promising means of replacing water with decane.

[0085] [Experimental Example C11] (Step (C1)) For step (C1), i.e., the release of CO2, the following experimental example was carried out.

[0086] In this experiment, decane, water, or IPDA solvents containing solid CA1·H2O are heated under atmospheric pressure to release CO2 and regenerate IPDA from the solid CA1·H2O. The experimental procedure is as follows: 1. A suspension containing 10 g of solid CA1·H2O and 100 mL of decane, water, or IPDA solvent is added to a three-neck flask. The temperature inside the flask is recorded with a logger. The three-neck flask is stirred. 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 exit gas from the three-neck flask is monitored by a Vaisala CARBOCAP® GMP251 CO2 probe. 4. Check that the oil bath temperature has reached 150°C and immerse the three-neck flask up to the neck. 5. The experiment will end when the CO2 release stabilizes based on the real-time measurement data from the CO2 probe.

[0087] Time-series data obtained from the experiment for the solvent temperature inside the three-neck flask and the CO2 concentration in the outlet gas are shown in Figures 1 and 2. Figure 1 compares the experimental results for the cases where decane and water were used as solvents, while Figure 2 compares the experimental results for the cases where decane and IPDA were used as solvents. The experiment was conducted using IPDA as the solvent because the boiling point of water is 100°C, making it impossible to observe a temperature rise plateau with water as a solvent. To observe this, the same experiment was conducted using IPDA as the solvent.

[0088] When decane was used as the solvent, a temperature increase plateau was observed at approximately 120 °C, associated with a phase transition, after heating to 150 °C (Figures 1 and 2). On the other hand, no temperature increase plateau was observed with IPDA (Figure 2). Therefore, the temperature at which IPDA regeneration from CA1·H2O solids occurs is thought to be lower with decane than with IPDA. With water, the temperature increase stopped at 100 °C, the boiling point of water, resulting in a slower CO2 release rate than with decane (Figure 1). However, with water, the rate of CO2 concentration decrease after the peak of CO2 release slowed, and it took a considerable amount of time for the CO2 concentration to reach zero. The CO2 release rate with decane was faster than with IPDA, and the CO2 concentration quickly reached zero after the peak of CO2 release, demonstrating that nonpolar solvents are superior to polar solvents for regeneration (Figure 2).

[0089] When IPDA was used as the solvent, the CO2 regenerated by heating and the volatilized IPDA recombined, forming a white deposit or transparent crystals on the top of the three-neck 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-neck flask. This is thought to be because nonpolar solvents inhibit CO2 absorption, or recombination, more than polar solvents. Thus, decane solvent was found to be superior to IPDA solvent from the perspective of practical processes.

[0090] [Experimental Example] (Process (D1)) The following experiment was carried out for step (D1), that is, replacing the solvent in the decane solution containing IPDA with water from decane.

[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, separation into two layers was observed: an upper decane layer and a lower aqueous layer. It is believed that the IPDA is distributed and dissolved in each layer. When the aqueous layer was separated using a separatory funnel and weighed, 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 had transferred to the aqueous layer. This suggests 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] The following procedure was used to confirm whether non-polar solvents other than decane, including IPDA, and the polar solvent acetone could be easily replaced with water by adding water.

[0093] Experimental Procedure 1. Add 2 ml each of the following non-polar solvents to 2 ml of IPDA: toluene, cyclopentane, hexane, heptane, n-octane, and decane. Mix thoroughly. 2. Add 2 ml of water to the sample and check whether separation occurs. 3. Blow in more CO2 to see if a solid forms.

[0094] Observing these results, in the case of acetone, a polar solvent, no two layers were formed even when water was added. In the case of non-polar solvents, the water sank to the bottom, forming two phases. The lower water tank was the larger volume, and in both cases, it was found that IPDA was distributed predominantly in the non-polar solvent.

[0095] All samples except for acetone turned cloudy when CO2 was blown in. This blowing test confirmed that IPDA was not deactivated.

[0096] [Example] (1) Step (A1), i.e., CO2 absorption step: IPDA was used as the amine compound and water as the polar solvent. A 600g solution of IPDA containing 10wt% IPDA was prepared and used as the CO2 absorbent. Air (CO2 concentration 0.04vol%) was aerated at 500mL / min at room temperature and pressure using a compressor to absorb CO2. Approximately 102 hours after the start of aeration, the IPDA solution began to become cloudy and precipitate formed due to the precipitation of CA1·H2O. Measurements using a total organic carbon (TOC) analyzer for the CO2 absorbent confirmed that the entire amount of CO2 in the supplied air was absorbed at least 212 hours after the start of aeration. Since 1mol of CO2 is absorbed per 1mol of IPDA, the total amount of CO2 absorbed by the CO2 absorbent after 212 hours was measured to be approximately one-third of the maximum absorption capacity. Therefore, the aeration time required for CO2 saturation is approximately three times 212 hours, i.e., approximately 650 hours.

[0097] (2) Step (B1), i.e., the step of replacing a polar solvent with a non-polar solvent: To the polar suspension containing the carbamic acid derivative precipitated in suspension in the polar solvent in step (A1), 500 mL of decane (a nonpolar solvent) is added and stirred at 200 RPM for approximately 1 minute. Upon standing, a nonpolar decane layer separates from a polar water layer, with the CA1·H2O solid floating at the interface. This decane-CA1·H2O solid-water mixture is then placed in a chromatographic tube, and the bottom water layer is drained. This single operation removes approximately 83 wt% of the total water content with almost no loss of decane. After this, the mixture is again stirred, and after decane-water phase separation, the water is drained in a plug-flow manner from the chromatographic tube. This operation is repeated twice, removing over 99 wt% of the water, completing the solvent conversion from water to decane.

[0098] For comparison, when regenerating CO2 using the water solvent, it is desirable to remove water from the CA1·H2O solids, but this requires complex and energy-intensive dehydration using a filter press. An example of the catalog values ​​for a commercially available filter press is a cake capacity of approximately 56 L and a dehydration surface area of ​​approximately 4.8 m. 2 The required power is a total of 2.3kW, consisting of a 1.5kW dehydration pump, a 0.4kW hydraulic pump, and a 0.4kW open-plate motor. When using decane as a solvent for regeneration, this input energy can be almost eliminated by using the aforementioned method of replacing water with decane.

[0099] (3) Step (C1), i.e., CO2 regeneration step: Decane containing solid CA1·H2O, obtained by replacing water with decane in step (B1), is heated to 120°C under normal pressure while stirring with a stirrer, and the solid CA1·H2O is regenerated into IPDA and CO2. When the temperature of decane reaches 84.9°C, CO2 bubbles begin to appear, and the bubbles become more intense at 116°C, so 120°C is thought to be the optimum 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 normal pressure, 0.93 g of CO2 was regenerated in 25 minutes, during which the temperature rose 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 This means that the energy input for regeneration can be roughly estimated at 1.9kJ.

[0101] For comparison, in the case of water, it took more than 80 minutes to regenerate 0.93 mol of CO2 under the same pressure, heating conditions, weight of the same CA1·H2O solid, and volume of solvent. Therefore, roughly 1.94 kJ multiplied by 80 / 25 gave an input energy of 6.1 kJ for regeneration, which was found to be more energy-intensive than the case of decane.

[0102] When comparing the amount of CO2 released over the same 25-minute period, the decane solvent produced 0.93 mol, while the water solvent produced 0.46 mol, indicating that the decane solvent was able to regenerate approximately twice the amount of CO2 in the same amount of time.

[0103] (4) Step (D1), i.e., step of replacing a non-polar solvent with a polar solvent: Water is added to the decane solution of IPDA produced in step (C1) to transfer the IPDA from the decane phase to the aqueous phase, and the decane phase is separated. Specifically, 540 g of water, approximately the same amount as used in the first step (A1), was added to the decane containing IPDA. Before the water was added, the IPDA and decane were completely mixed, but after adding the water and stirring for about one minute, the stirring was stopped and the mixture was allowed to stand for one minute, causing the mixture to separate into an upper decane layer and a lower aqueous layer. Because IPDA is hydrophilic, this operation immediately distributed 98.0 wt% of the IPDA into the aqueous layer, and the remaining 2.0 wt% into the decane layer. Only the lower aqueous IPDA solution was extracted using a chromatography tube.

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

[0105] The present invention can be used in the fields of CO2 fixation, CO2 capture, and CO2 transportation in general.

Claims

1. A process (A1) comprising: a step of absorbing carbon dioxide into an amine compound polar solution containing an amine compound including isophoronediamine (IPDA) and a polar solvent, thereby precipitating a solid reactant of the amine compound and the carbon dioxide in the amine compound polar solution, thereby obtaining a polar reactant which is a polar suspension or a slurry obtained therefrom; a step (B1) of treating the polar reactant obtained in the step (A1) with a nonpolar solvent and removing the polar solvent to obtain a nonpolar reactant which is a nonpolar suspension containing the solid reactant and the nonpolar solvent or a slurry obtained therefrom; a step (C1) of heating the nonpolar reactant obtained in the step (B1) under increased pressure, normal pressure, or reduced pressure, and separating and recovering carbon dioxide to regenerate the amine compound from the nonpolar reactant, thereby obtaining an amine compound nonpolar solution; and a step (D1) of treating the non-polar amine compound solution obtained in the step (C1) with a polar solvent to replace the solvent and obtain a polar amine compound solution, the polar solvent is at least one selected from the group consisting of water, methanol, and ethanol; the non-polar solvent is at least one selected from the group consisting of toluene, hexane, heptane, n-octane, nonane, decane, cyclopentane, and cyclohexane; The method for separating and recovering carbon dioxide, wherein the solid reactant comprises solid carbamic acid.

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

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

4. In the step (C1), the non-polar reactant is heated to 100 to 150° C. under a pressure of from atmospheric pressure to 20 kPa to obtain CO ２ 2. The method for separating and recovering carbon dioxide according to claim 1, wherein the non-polar solution of the amine compound is obtained by discharging the non-polar solution of the amine compound.

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

6. 2. The method for separating and recovering carbon dioxide according to claim 1, further comprising a step (F1) of carrying out step (A1) at a first location and transporting the resulting polar reactant to a second location where carbon dioxide is regenerated, and step (C1) being carried out at the second location.

7. 2. The method for separating and recovering carbon dioxide according to claim 1, further comprising a step (G1) of carrying out the steps (A1) and (B1) at a first location, transporting the obtained non-polar reactant to a second location where carbon dioxide is regenerated, and the step (C1) being carried out at the second location.

8. 7. The method for separating and capturing carbon dioxide according to claim 6, further comprising a step (H1) of transporting the nonpolar amine compound solution obtained in the step (C1) or the polar amine compound solution obtained in the step (D1) from the second location to the first location, and repeating the steps (A1) to (D1), and the steps (F1) and (H1).

9. 8. The method for separating and capturing carbon dioxide according to claim 7, further comprising a step (H1) of transporting the nonpolar amine compound solution obtained in the step (C1) or the polar amine compound solution obtained in the step (D1) from the second location to the first location, wherein, in a case where the nonpolar amine compound solution obtained in the step (C1) has been transported, the steps (A1) to (D1), the steps (G1), and (H1) are repeated after the step (D1) is performed.

10. The carbon dioxide separation and recovery method according to any one of claims 6 to 9, wherein renewable energy is used for the heating in the step (C1) performed at the second location.

11. The method for separating and recovering carbon dioxide according to any one of claims 6 to 9, wherein water is used as the polar solvent.

12. A method for regenerating carbon dioxide, comprising: absorbing carbon dioxide into an amine compound polar solution containing an amine compound including isophoronediamine (IPDA) and a polar solvent; obtaining a polar reactant which is a polar suspension or a slurry obtained therefrom containing solid carbamic acid, which is a reaction product of the amine compound and the carbon dioxide; and regenerating carbon dioxide from the polar reactant, the polar solvent is at least one selected from the group consisting of water, methanol, and ethanol; As a non-polar solvent, at least one selected from the group consisting of toluene, hexane, heptane, n-octane, nonane, decane, cyclopentane, and cyclohexane is used; treating the polar reactant with the non-polar solvent and removing the polar solvent to provide a non-polar reactant that is a non-polar suspension or a slurry obtained therefrom containing the reactant and the non-polar solvent; A method for regenerating carbon dioxide, comprising heating the obtained nonpolar reactant under increased pressure, normal pressure or reduced pressure, separating and recovering carbon dioxide, and regenerating the amine compound from the nonpolar reactant to obtain an amine compound nonpolar solution.

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