Method for recovering carbon dioxide from a gas containing carbon dioxide, and aqueous amine solution for recovering carbon dioxide

Abstract

Provided is a method for recovering carbon dioxide, that includes: a first step in which an aqueous amine solution that contains a amine compound is caused to absorb carbon dioxide in a gas containing carbon dioxide; and a second step in which the aqueous amine solution that has absorbed the carbon dioxide is heated and the carbon dioxide is desorbed and recovered from the aqueous solution. The amine compound includes 2-isopropyl aminoethanol and H2N-A-NH-A-OH (where the two As each indicate a C2–4 alkylene group, respectively, that may be the same or different from each other).

Description

[Technical Field]

[0001] The present invention relates to a method for recovering carbon dioxide from a gas containing carbon dioxide, and to an aqueous amine solution for recovering carbon dioxide. [Background technology]

[0002] Global warming is thought to be caused by the increase in greenhouse gases such as carbon dioxide in the atmosphere due to increased human activity. In order to prevent global warming, measures to reduce carbon dioxide emissions are urgently needed.

[0003] As a method for recovering carbon dioxide in a gas, for example, Patent Document 1 proposes a method for recovering carbon dioxide including a step of absorbing carbon dioxide in a gas into an aqueous solution containing 2-isopropylaminoethanol and at least one selected from the group consisting of piperazines and alkanolamines, and a step of heating the aqueous solution into which the carbon dioxide has been absorbed to desorb and recover the carbon dioxide. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] WO2009 / 001804 Pamphlet Summary of the Invention [Problem to be solved by the invention]

[0005] To efficiently capture carbon dioxide in gas using an aqueous amine solution at low cost, an aqueous amine solution that can quickly absorb carbon dioxide to as high a concentration as possible is required. This requirement becomes stronger as the partial pressure of carbon dioxide in the gas decreases. Several aqueous amine solutions have been proposed, but all of them have room for improvement in terms of the balance between the amount of carbon dioxide absorbed and the absorption rate. [Means for solving the problem]

[0006] One aspect of the present invention is a method for recovering carbon dioxide from a gas containing carbon dioxide, the method comprising: a first step of absorbing carbon dioxide into an aqueous amine solution containing an amine compound; and a second step of heating the aqueous amine solution having the carbon dioxide absorbed therein to desorb and recover the carbon dioxide, wherein the amine compound is a first amine component represented by the formula (I):

[0007] [ka]

[0008] and as a secondary amine component, a compound represented by the general formula (II):

[0009] [ka]

[0010] wherein in the general formula (II), two A's each represent an alkylene group having 2 to 4 carbon atoms and may be the same or different.

[0011] Another aspect of the present invention is an aqueous amine solution for recovering carbon dioxide from a gas containing carbon dioxide, the aqueous amine solution comprising an amine compound, the amine compound having a first amine component represented by formula (I):

[0012] [ka]

[0013] and as a secondary amine component, a compound represented by the general formula (II):

[0014] [ka]

[0015] In the general formula (II), two A's each represent an alkylene group having 2 to 4 carbon atoms and may be the same or different from each other. [Effects of the Invention]

[0016] According to the present disclosure, in the carbon dioxide recovery method, the balance between the amount and rate of carbon dioxide absorption can be well controlled, thereby enabling carbon dioxide to be recovered efficiently at low cost. The aqueous amine solution quickly absorbs a sufficient amount of carbon dioxide even when the partial pressure of carbon dioxide in the gas is less than 5 kPa.

[0017] The novel features of the present invention are set forth in the appended claims, but the present invention, both in terms of structure and content, together with other objects and features of the present invention, will be better understood from the following detailed description taken in conjunction with the drawings. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a graph showing the relationship between the amount of carbon dioxide absorbed and the absorption rate by aqueous amine solutions of Examples and Comparative Examples. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments of the carbon dioxide recovery method and the amine aqueous solution for recovering carbon dioxide will be described, but the carbon dioxide recovery method and the amine aqueous solution for recovering carbon dioxide according to the present disclosure are not limited to the following embodiments.

[0020] In the following description, specific numerical values, materials, etc. may be exemplified, but other numerical values, materials, etc. may be applied as long as the effects of the present disclosure are obtained. Note that known carbon dioxide recovery methods and components of amine aqueous solutions may be applied to components other than those characteristic of the present disclosure. In this specification, when a "range between numerical value A and numerical value B" is mentioned, the range includes numerical value A and numerical value B.

[0021] In the following description, when lower and upper limits of numerical values relating to specific physical properties, conditions, etc. are exemplified, any of the exemplified lower limits and any of the exemplified upper limits can be arbitrarily combined, as long as the lower limit is not equal to or greater than the upper limit. When multiple materials are exemplified, one of them may be selected and used alone, or two or more may be used in combination.

[0022] In this specification, the content (mass%) of the amine compound in the aqueous amine solution means the percentage of the amine compound relative to the mass of the aqueous amine solution (total of water and the amine compound) excluding carbon dioxide absorbed in the aqueous amine solution.

[0023] The method for recovering carbon dioxide from a gas containing carbon dioxide has a first step and a second step. The first step involves absorbing carbon dioxide into an aqueous amine solution containing an amine compound. The second step involves heating the aqueous amine solution in which carbon dioxide has been absorbed, thereby desorbing and recovering the carbon dioxide from the aqueous solution. In the first step, the method for absorbing carbon dioxide into the aqueous amine solution is not particularly limited. For example, the method for contacting the gas containing carbon dioxide with the aqueous amine solution is not limited. In the second step, the method for heating the aqueous amine solution in which carbon dioxide has been absorbed is not limited. The method for recovering the carbon dioxide desorbed from the aqueous amine solution is also not limited.

[0024] The amine compound in the aqueous amine solution contains a first amine component and a second amine component. The amine compound may contain a tertiary amine component other than the first and second amine components, but the total of the first amine component and the second amine component preferably accounts for, for example, 70% by mass or more, more preferably 80% by mass or more, or even 90% by mass or more of the amine compounds (total of all amine compounds).

[0025] The primary amine component has the formula (I):

[0026] [ka]

[0027] The most popular example is 2-isopropylaminoethanol (hereinafter also referred to as "IPAE"), which is expressed by the formula: When a gas containing carbon dioxide at a partial pressure of 5 kPa or more is used, IPAE is excellent in terms of its carbon dioxide absorption performance and resistance to degradation, as well as its low heat of reaction. Here, carbon dioxide absorption performance refers to the amount of carbon dioxide absorbed per unit mass (loading amount) and the carbon dioxide dissipation (desorption performance). Carbon dioxide dissipation (desorption performance) refers to the amount and rate of desorption.

[0028] Carbon dioxide absorbed by an aqueous amine solution forms either carbamate anions or bicarbonate ions in the amine solution. The reaction heat generated during absorption is higher for the reaction that produces carbamate anions. This difference is thought to be due to differences in the molecular structure of the amine compounds. The difference in the bonding state between carbon dioxide and amine compounds affects the desorption rate and amount of carbon dioxide desorbed during the desorption process.

[0029] According to 13C-NMR measurements, 2-aminoethanol (MEA), a representative primary alkanolamine, produces a large amount of carbamate anion, which has a high heat of reaction, and produces little bicarbonate ion, which has a low heat of reaction. 2-Ethylaminoethanol (EAE), a secondary alkanolamine, also produces a large amount of carbamate anion, which has a high heat of reaction, and produces little bicarbonate ion, which has a low heat of reaction, similar to MEA.

[0030] In contrast, IPAE, although a secondary alkanolamine, produces only traces of carbamate anions, with the majority producing bicarbonate ions. This is presumably because the isopropyl group substituted on the amino group of the IPAE molecule is bulky, unlike the ethyl group in EAE, and its steric properties significantly inhibit the formation of carbamate bonds. The above characteristics of IPAE are thought to be due to the carbon dioxide absorption mechanism that generates bicarbonate ions.

[0031] On the other hand, IPAE has a slow absorption rate of carbon dioxide and, for example, when a gas containing carbon dioxide at a partial pressure of less than 5 kPa is used, its carbon dioxide absorption performance is insufficient. Furthermore, since IPAE has a relatively low boiling point (approximately 171°C), it is prone to volatilization and loss when the aqueous amine solution is heated in the second step.

[0032] Patent Document 1 proposes the use of a specific piperazine compound or a specific alkanolamine compound in combination with IPAE to supplement the absorption rate of IPAE when targeting gases with a carbon dioxide concentration of, for example, 5 to 30% by volume. However, there is a limit to how quickly the absorption rate can be increased, and the absorption rate is insufficient, particularly when targeting gases containing carbon dioxide at a partial pressure of less than 5 kPa. Furthermore, piperazine compounds have low solubility in water, so they may precipitate in aqueous solutions.

[0033] In contrast, when a secondary amine component is used in combination with IPAE, the rate of carbon dioxide absorption is significantly improved. The second component is represented by the general formula (II):

[0034] [ka]

[0035] In general formula (II), two A's each represent an alkylene group having 2 to 4 carbon atoms, and may be the same or different.

[0036] The secondary amine component has a fast carbon dioxide absorption rate, particularly when dealing with gases containing carbon dioxide at partial pressures of less than 5 kPa (even 2 kPa or less, or 1 kPa or less), and its carbon dioxide absorption performance is also sufficient. Furthermore, because the secondary amine component has a relatively high boiling point, it is less likely to volatilize when the aqueous amine solution is heated in the second step, resulting in less loss. Furthermore, the secondary amine component has high solubility in water, eliminating the risk of precipitation in the aqueous solution.

[0037] Although the secondary amine component has a lower carbon dioxide loading capacity than IPAE, a high loading capacity can be maintained by using the secondary amine component in combination with IPAE. The combined use of the secondary amine component and IPAE maximizes the advantages of each. An aqueous amine solution containing the secondary amine component and IPAE quickly absorbs sufficient amounts of carbon dioxide even when the target gas contains carbon dioxide at a partial pressure of less than 5 kPa. This makes it possible to efficiently recover carbon dioxide from gases containing low concentrations of carbon dioxide (e.g., the atmosphere) at low cost.

[0038] Among secondary amine components, N-(2-aminoethyl)-2-aminoethanol (hereinafter also referred to as "AEAE"), in which both A's are ethylene groups having two carbon atoms, has a high carbon dioxide absorption rate and excellent carbon dioxide absorption performance. AEAE has a high boiling point (approximately 244°C), is stable, and is less likely to cause loss. AEAE also has very high solubility in water. The content of AEAE in the secondary amine component is, for example, preferably 70% by mass or more, more preferably 80% by mass or more, and may be 90% by mass or more (or 100%).

[0039] The content of amine compounds (total of all amine compounds) contained in the aqueous amine solution (hereinafter also referred to as the "total amine amount") is, for example, not particularly limited, but is 20% to 60% by mass, alternatively 30% to 60% by mass, 30 to 55% by mass, or 40% to 55% by mass. When the total amine amount is 60% by mass or less, it is believed that the effect of water as an activator is improved, the amount of carbon dioxide absorption is likely to increase, and the miscibility of the first amine component and the second amine component is improved. In addition, the viscosity of the aqueous amine solution is maintained low. Furthermore, when the total amine amount is 20% by mass or more (even more preferably 30% by mass or more), the carbon dioxide absorption performance per unit volume of the aqueous amine solution can be sufficiently increased, thereby enabling more efficient carbon dioxide recovery.

[0040] The content (C2) of the second amine component contained in the amine compound may be greater than the content (C1) of the first amine component (IPAE) contained in the amine compound. In this case, the rate of absorption of carbon dioxide by the aqueous amine solution increases, particularly when a gas containing carbon dioxide at a partial pressure of less than 5 kPa (even 2 kPa or less, or 1 kPa or less) is used, enabling more efficient recovery of carbon dioxide. The ratio C2 of the content C2 of the second amine component to the content C1 of the first amine component (IPAE): C2 / C1, may be, for example, 1.5 to 3, 2 to 3, or 2 to 2.5.

[0041] More specifically, the content of the first amine component (IPAE) in the aqueous amine solution is, for example, 5% by mass or more and less than 30% by mass, and may be 10% by mass or more and 25% by mass or less.

[0042] The content of the second amine component in the aqueous amine solution is, for example, 15% by mass or more and 55% by mass or less, or may be 25% by mass or more and 50% by mass or less, or 30% by mass or more and 45% by mass or less.

[0043] It is not necessary for C2 to be greater than C1; the content (C2) of the second amine component contained in the amine compound may be less than the content (C1) of the first amine component (IPAE) contained in the amine compound, and C1 may be equal to C2. In this case, the carbon dioxide absorption and desorption performance of the aqueous amine solution can be further improved. Furthermore, even when the C2 / C1 ratio is approximately 0.05, the effect of improving the carbon dioxide absorption rate by the second amine component can be observed. When the C2 / C1 ratio is 0.05 or higher, or even 0.1 or higher, a more stable improvement can be observed.

[0044] The aqueous amine solution may contain various additives, such as a phosphoric acid-based anticorrosive to prevent corrosion of equipment, a silicone-based antifoaming agent to prevent foaming, or an antioxidant to prevent deterioration of the amine compound.

[0045] As described above, the aqueous amine solution is suitable for recovering carbon dioxide from a gas containing carbon dioxide at a low concentration. That is, the first step may be a step of bringing a gas containing carbon dioxide at a partial pressure of less than 5 kPa (or even 2 kPa or less, or 1 kPa or less) into contact with the aqueous amine solution to absorb the carbon dioxide into the aqueous amine solution.

[0046] The gas containing carbon dioxide at a partial pressure of less than 5 kPa may be the atmosphere. In other words, the present disclosure may be applied to DAC (Direct Air Capture). The gas containing carbon dioxide at a partial pressure of less than 5 kPa may be a gas containing carbon dioxide emitted in an enclosed space by human breathing, energy conversion by equipment, etc. Examples of enclosed spaces include the indoor spaces of submersible research vessels, space stations, buildings, offices, etc.

[0047] The gas containing carbon dioxide may contain carbon dioxide at a higher concentration. The gas containing carbon dioxide may be, for example, exhaust gas emitted from a thermal power plant fueled by coal, heavy oil, natural gas, or the like, a blast furnace in a steelworks that reduces iron oxide with coke, a converter in a steelworks that burns carbon in pig iron to make steel, boilers in various manufacturing plants, kilns in cement factories, or transportation equipment such as automobiles, ships, and aircraft that fuels gasoline, heavy oil, light oil, or the like.

[0048] In the first step, the gas containing carbon dioxide may be brought into contact with an aqueous amine solution at a temperature of, for example, 60°C or lower (even 50°C or lower, or 45°C or lower), preferably 20°C to 45°C. This can promote the absorption of carbon dioxide into the aqueous amine solution.

[0049] The carbon dioxide-containing gas can be brought into contact with the aqueous amine solution by, for example, bubbling the carbon dioxide-containing gas into the aqueous amine solution, atomizing or spraying the aqueous amine solution into a gas stream containing carbon dioxide, or countercurrently contacting the carbon dioxide-containing gas with the aqueous amine solution in an absorption tower.

[0050] In the first step, the pressure of the gas containing carbon dioxide may be approximately atmospheric pressure. To improve absorption performance, the gas may be pressurized to a higher pressure. From the viewpoint of reducing the energy consumption required for compressing the gas, it is preferable to carry out the first step under atmospheric pressure.

[0051] In the second step, the aqueous amine solution having absorbed carbon dioxide may be heated to a temperature of, for example, 70°C or higher. The higher the temperature of the aqueous amine solution, the more easily carbon dioxide is desorbed from the aqueous amine solution. The aqueous amine solution having absorbed carbon dioxide may be heated to 80°C or higher, or even 90°C or higher, preferably 90 to 120°C. This can promote the desorption of carbon dioxide from the aqueous amine solution. Note that the boiling point of the aqueous amine solution according to this embodiment can be 120°C or higher, and therefore it can be heated to 120°C without boiling even under atmospheric pressure.

[0052] In the second step, the amine aqueous solution that has absorbed carbon dioxide may be heated and bubbled in a vessel in the same manner as distillation to desorb the carbon dioxide, or the liquid contact surface may be expanded and heated in a plate tower, spray tower, or desorption tower containing a porcelain or metal mesh packing. This liberates and releases carbon dioxide from the carbamate anions or bicarbonate ions.

[0053] The pressure of the atmosphere of the amine aqueous solution when carbon dioxide is desorbed may be approximately atmospheric pressure. The atmosphere may be reduced in pressure to promote desorption of carbon dioxide. When carbon dioxide is desorbed in the internal space of a vessel, plate column, spray column, desorption column, or the like, the pressure of the internal space may be higher than atmospheric pressure.

[0054] The aqueous amine solution from which carbon dioxide has been desorbed is recycled and reused in the first step to absorb carbon dioxide again.

[0055] The purity of the recovered carbon dioxide can be extremely high, for example, about 95 to 99.9% by volume. High-concentration carbon dioxide can be used as a raw material for synthesizing chemicals and polymeric substances, a refrigerant for freezing food, etc. In addition, it is also possible to store the recovered carbon dioxide underground, for example, a technology that is currently being developed.

[0056] [Example] Next, the present disclosure will be described in more detail using examples and comparative examples, but the present disclosure is not limited to the following examples. All chemicals used in the examples are reagents manufactured by Tokyo Chemical Industry Co., Ltd.

[0057] Example 1 A glass gas absorption bottle was immersed in a thermostatic water bath set to keep the temperature of the amine aqueous solution at 40°C, and 50 mL of an amine aqueous solution A1 (total 100%) containing 15 mass% IPAE, 35 mass% AEAE, and 50 mass% water was filled in the bottle. The partial pressure (P CO2A mixed gas of carbon dioxide and nitrogen at a pressure of 1 kPa was bubbled through the aqueous amine solution A1 at a rate of 0.7 liters / minute to absorb the carbon dioxide into the aqueous amine solution A1.

[0058] Gas was collected at the inlet and outlet of the mixed gas in the gas absorption bottle, and the carbon dioxide concentration in the gas was continuously measured with an infrared carbon dioxide meter (HORIBA GAS ANALYZER VA-3000). The amount of carbon dioxide absorbed was monitored from the difference in the carbon dioxide flow rate between the inlet and outlet.

[0059] The amount of carbon dioxide absorbed at the point when the carbon dioxide concentration at the outlet coincided with the carbon dioxide concentration at the inlet was taken as the saturated absorption amount.

[0060] Next, in the same gas flow, the temperature of the aqueous amine solution A1, which had absorbed carbon dioxide to a saturated state, was raised to 120°C under atmospheric pressure, and carbon dioxide was desorbed from the aqueous amine solution A1. The gas absorption bottle was filled with carbon dioxide, and therefore, the partial pressure of carbon dioxide (P CO2 ) was approximately 100 kPa.

[0061] The amount of inorganic carbon in the amine aqueous solution A1 that had absorbed carbon dioxide to saturation at 40°C and the amine aqueous solution A1 after carbon dioxide desorption at 120°C was measured using a gas chromatographic total organic carbon meter (SHIMADZU TOC-VCSH), and the amount of carbon dioxide absorbed in each was calculated.

[0062] Table 1 shows the carbon dioxide absorption rate, the saturated carbon dioxide absorption amount at 40°C (M_rich), the carbon dioxide absorption amount after carbon dioxide desorption at 120°C (M_lean), and the carbon dioxide recovery amount calculated from the difference between these (loading amount, M_rich - M_lean). The absorption amount is shown as the mass of carbon dioxide absorbed in a unit volume (1 L) of amine aqueous solution (g-CO2 / L-soln.).

[0063] Comparative Example 1 Measurements were carried out in the same manner as in Example 1, except that 50 mL of an aqueous amine solution B1 containing 30 mass % IPAE, 20 mass % piperazine (PZ), and 50 mass % water (total 100%) was filled into the gas absorption bottle. The results are shown in Table 1.

[0064] Comparative Example 2 The same measurements as in Example 1 were carried out, except that 50 mL of an amine aqueous solution C1 containing 30 mass % of monoethanolamine (MEA) and 70 mass % of water (total 100%) was filled into the gas absorption bottle. The results are shown in Table 1.

[0065] [Table 1]

[0066] Considering the results in Table 1, for amine solution A1, the loading range corresponds to the amount of carbon dioxide recovered in one absorption and desorption cycle (loading amount) between 112.8 g CO2 / L-soln and 143.3 g CO2 / L-soln. For amine solution B1, the loading range corresponds to the amount of carbon dioxide recovered in one absorption and desorption cycle (loading amount). For amine solution C1, the loading range corresponds to the amount of carbon dioxide recovered in one absorption and desorption cycle (loading amount). For amine solution B1, the loading range corresponds to the amount of carbon dioxide recovered in one absorption and desorption cycle (loading amount), and for amine solution C1, the loading range corresponds to the amount of carbon dioxide recovered in one absorption and desorption cycle (loading amount).

[0067] Next, Figure 1 shows the relationship between the carbon dioxide absorption amount (g / L-soln.) and absorption rate (g-CO2 / L / min.) at 40°C. From Figure 1, it can be seen that in the case of amine aqueous solution A1, the absorption rate does not change much in the loading region and a high liquid absorption rate can be maintained. On the other hand, it can be seen that in the case of amine aqueous solution B1, the absorption rate drops sharply in the loading region. It can also be seen that in the case of amine aqueous solution C1, the absorption rate drops sharply in the loading region and the loading amount is also small.

[0068] Considering practical requirements, the shorter the takt time for capturing carbon dioxide by repeatedly absorbing and desorbing carbon dioxide, the more desirable it is. Amine aqueous solution A1 quickly absorbs and releases carbon dioxide in the loading area, resulting in a significantly shorter takt time than amine aqueous solutions B1 and C1. In other words, using an amine aqueous solution such as amine aqueous solution A1 makes it possible to capture carbon dioxide efficiently and at low cost. [Industrial Applicability]

[0069] The method for recovering carbon dioxide according to the present disclosure makes it possible to recover carbon dioxide from gas efficiently and at low cost. The aqueous amine solution according to the present disclosure can quickly absorb carbon dioxide to a high concentration even when the partial pressure of carbon dioxide in the gas is low. The present disclosure is suitable for practical application of, for example, direct air capture (DAC), which recovers carbon dioxide from the atmosphere.

[0070] While the present invention has been described in terms of presently preferred embodiments, such disclosure is not to be interpreted as limiting. Various changes and modifications will no doubt become apparent to those skilled in the art to which the present invention pertains upon reading the above disclosure. It is therefore intended that the appended claims be interpreted to cover all changes and modifications that do not depart from the true spirit and scope of the invention.

Claims

1. A method for recovering carbon dioxide from a gas containing carbon dioxide, comprising: a first step of absorbing carbon dioxide into an amine aqueous solution containing an amine compound; a second step of heating the aqueous amine solution having the carbon dioxide absorbed therein to desorb and recover the carbon dioxide from the aqueous solution, The amine compound is As the primary amine component, a compound represented by formula (I): 【Chemical 1】 and 2-isopropylaminoethanol represented by the formula: As the secondary amine component, a compound represented by the general formula (II): 【Chemistry 2】 The alkanolamine is represented by In the general formula (II), two A's each represent an alkylene group having 2 to 4 carbon atoms and may be the same or different from each other. In the first step, a gas containing carbon dioxide at a partial pressure of less than 5 kPa is brought into contact with the aqueous amine solution, thereby allowing the aqueous amine solution to absorb the carbon dioxide.

2. 2. The method for recovering carbon dioxide according to claim 1, wherein the second amine component is N-(2-aminoethyl)-2-aminoethanol in which both of the two A's are ethylene groups.

3. 3. The method for recovering carbon dioxide according to claim 1, wherein the content of the amine compound in the aqueous amine solution is 20% by mass or more and 60% by mass or less.

4. The method for recovering carbon dioxide according to any one of claims 1 to 3, wherein a content of the second amine component contained in the amine compound is higher than a content of the first amine component contained in the amine compound.

5. The method for recovering carbon dioxide according to any one of claims 1 to 4, wherein the content of the first amine component contained in the aqueous amine solution is 5% by mass or more and less than 30% by mass.

6. 6. The method for recovering carbon dioxide according to claim 5, wherein in the first step, the gas is brought into contact with the aqueous amine solution at a temperature of 60°C or less, and in the second step, the aqueous amine solution having absorbed the carbon dioxide is heated to a temperature of 70°C or more.

7. An aqueous amine solution for recovering carbon dioxide from a gas containing carbon dioxide, comprising: The amine aqueous solution contains an amine compound, The amine compound is As the primary amine component, a compound represented by formula (I): 【Chemistry 3】 and 2-isopropylaminoethanol represented by the formula: As the secondary amine component, a compound represented by the general formula (II): 【Chemistry 4】 The alkanolamine is represented by In the general formula (II), two A's each represent an alkylene group having 2 to 4 carbon atoms and may be the same or different from each other. An aqueous amine solution for recovering carbon dioxide, wherein the total proportion of the first amine component and the second amine component in the amine compound is 90 mass % or more.

8. A method for recovering carbon dioxide from a gas containing carbon dioxide, comprising: a first step of absorbing carbon dioxide into an amine aqueous solution containing an amine compound; a second step of heating the aqueous amine solution having the carbon dioxide absorbed therein to desorb and recover the carbon dioxide from the aqueous solution, The amine compound is As the primary amine component, a compound represented by formula (I): 【Chemical 1】 and 2-isopropylaminoethanol represented by the formula: As the secondary amine component, a compound represented by the general formula (II): 【Chemistry 2】 The alkanolamine is represented by In the general formula (II), two A's each represent an alkylene group having 2 to 4 carbon atoms and may be the same or different from each other. The method for recovering carbon dioxide, wherein the total proportion of the first amine component and the second amine component in the amine compound is 90 mass% or more.

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