JP2024008922A - Carbon dioxide absorption liquid and separation and recovery method of carbon dioxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carbon dioxide absorption liquid which provides an energy-saving direct air recovery (DAC) technique and accordingly can separate and recovery a carbon dioxide using a pressure difference from atmospheric air by decompression requiring no heat energy, or the like, and a separation and recovery method of a carbon dioxide using the same.

SOLUTION: A carbon dioxide absorption liquid for separating and recovering a carbon dioxide from separated gas containing a carbon dioxide contains primary amine and an organic solvent, wherein the organic solvent has a vapor pressure at 25°C of 0-1,000 Pa.

SELECTED DRAWING: None

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to a carbon dioxide absorption liquid and a method for separating and recovering carbon dioxide.

In recent years, the rapid increase in greenhouse gas emissions such as carbon dioxide and methane accompanying human social activities has been cited as one of the causes of global warming. In particular, carbon dioxide is the most important greenhouse gas, and in accordance with the Paris Agreement that went into effect in 2016, there is an urgent need to take measures to reduce carbon dioxide emissions.

Under these circumstances, direct air capture (DAC) technology, which adsorbs carbon dioxide from the atmosphere and buries it underground, is one of the few methods that can contribute to negative emissions.

To date, companies such as Carbon Engineering, Climeworks, and Global Thermostat have advanced initiatives in direct air capture (DAC) technology.

For example, Carbon Engineering Co., Ltd. uses an alkaline solution to absorb carbon dioxide and fix it in carbonate, but recovering carbon dioxide requires heating at an extremely high temperature of 900°C. Therefore, an excessive amount of thermal energy is required.

Furthermore, when an aqueous solution is used as the carbon dioxide absorption liquid, the vapor pressure of water is extremely high. For this reason, the splitting of carbon dioxide in the atmosphere is about 40 Pa at 25° C., which is not suitable for separating and recovering carbon dioxide using a pressure difference from the atmosphere, such as by reducing pressure, which does not require thermal energy.

For this reason, currently no carbon dioxide absorbent suitable for separating and recovering carbon dioxide using the pressure difference from the atmosphere, such as decompression that does not require thermal energy, has been put into practical use. Air recovery (DAC) technology is required.

The present invention aims to solve the above-mentioned problems, and in order to provide a more energy-saving direct air recovery (DAC) technology, it uses a pressure difference from the atmosphere through depressurization etc. that does not require thermal energy. An object of the present invention is to provide a carbon dioxide absorption liquid that can separate and recover carbon dioxide, and a method for separating and recovering carbon dioxide using the same.

As a result of intensive studies to solve the above problems, the present inventors solved the above problems by using a primary amine and an organic solvent with a vapor pressure of 0 to 1000 Pa at 25°C, and the thermal energy We have discovered that a carbon dioxide absorption liquid can be obtained in which carbon dioxide can be separated and recovered by using a pressure difference from the atmosphere, such as by depressurization, which does not require a pressure difference.

The present invention has been completed based on the above knowledge and further thorough studies, and includes the following configurations.

Item 1. A carbon dioxide absorption liquid for separating and recovering carbon dioxide from a gas to be separated containing carbon dioxide,
contains a primary amine and an organic solvent, and
The organic solvent is a carbon dioxide absorption liquid having a vapor pressure of 0 to 1000 Pa at 25°C.

Item 2. Dioxide according to Item 1, wherein the difference in CO ₂ absorption amount at 25° C. when the carbon dioxide partial pressure is 40 Pa and 10 Pa is 0.01 to 1.00 mol-CO ₂ /mol-amine. Carbon absorption liquid.

Item 3. The carbon dioxide absorbing liquid according to Item 1 or 2, wherein the carbon dioxide absorbing liquid has a vapor pressure of 100 Pa or less at 25°C.

Item 4. Items 1 to 3, in which the CO ₂ absorption amount at 25° C. and when the carbon dioxide partial pressure of the carbon dioxide absorption liquid is 40 Pa is 0.010 g-CO ₂ /g-carbon dioxide absorption liquid or more. The carbon dioxide absorption liquid according to any one of the above.

Item 5. Item 5. The carbon dioxide absorption liquid according to any one of Items 1 to 4, wherein the primary amine is a primary alkanolamine.

Item 6. The primary alkanolamine is monoethanolamine, diglycolamine, 2-amino-2-methyl-1-propanol, monopropanolamine, monoisopropanolamine, DL-1-amino-2-propanol, and 3-amino Item 5. The carbon dioxide absorption liquid according to item 5, which is at least one member selected from the group consisting of -1,2-propanediol.

Section 7. 7. The carbon dioxide absorption liquid according to any one of Items 1 to 6, wherein the organic solvent is at least one selected from the group consisting of polyols or alkyl ethers thereof, and ionic liquids.

Section 8. The organic solvent is triethylene glycol, tetraethylene glycol, polyethylene glycol, and monoalkyl ethers thereof,
The cation is an imidazolinium cation, a quaternary phosphonium cation, or a cation having a heterocyclic skeleton containing a phosphorus atom, and the anion is Br ⁻ , Cl ⁻ , BF ₄ ⁻ , PF ₆ ⁻ , or (CF ₃ SO ₂ ). _8. The carbon dioxide absorption liquid according to any one of Items 1 to 7, which is at least one selected from the group consisting of an ionic liquid that is 2 N ^- .

Item 9. 9. The carbon dioxide absorption liquid according to any one of Items 1 to 8, wherein the content of the primary amine is 1 to 50% by mass, with the total amount of the carbon dioxide absorption liquid being 100% by mass.

Item 10. Item 10. The carbon dioxide absorption liquid according to any one of Items 1 to 9, wherein the content of the organic solvent is 50 to 99% by mass, with the total amount of the carbon dioxide absorption liquid being 100% by mass.

Item 11. The carbon dioxide absorption liquid according to any one of Items 1 to 10, which is used for direct air recovery technology that adsorbs carbon dioxide and buries it underground.

Item 12. A method for separating and recovering carbon dioxide from a gas to be separated containing carbon dioxide, the method comprising:
(1) Carbon dioxide absorption in which the carbon dioxide absorption liquid according to any one of items 1 to 11 is brought into contact with a gas to be separated containing carbon dioxide, and carbon dioxide is absorbed from the gas to be separated containing carbon dioxide. obtaining a liquid, and
(2) A method comprising a step of desorbing and dissipating carbon dioxide from the carbon dioxide absorption liquid obtained in step (1) above under reduced pressure and recovering the dissipated carbon dioxide.

Item 13. 13. The method according to item 12, wherein the step (2) is a step of sublimating carbon dioxide from a carbon dioxide absorption liquid under reduced pressure.

Section 14. Item 14. The method according to Item 12 or 13, wherein the steps (1) and (2) are performed at 0 to 60°C.

Item 15. Any one of items 12 to 14, wherein the step (1) is carried out under a pressure of a carbon dioxide partial pressure of 30 to 100 Pa, and the step (2) is carried out under a pressure of a carbon dioxide partial pressure of 1 to 20 Pa. The method described in.

According to the present invention, there is provided a carbon dioxide absorption liquid that can separate and recover carbon dioxide by using a pressure difference from the atmosphere through depressurization or the like that does not require thermal energy, and a method for separating and recovering carbon dioxide using the same. be able to.

In the carbon dioxide absorption liquid obtained in Example 3, the relationship between carbon dioxide partial pressure and carbon dioxide absorption amount at 25°C, 30°C and 40°C is shown.

As used herein, "comprise" is a concept that includes "consist essentially of" and "consist of".

In this specification, when a range is expressed as "A to B", unless otherwise specified, it means greater than or equal to A and less than or equal to B.

1. Carbon dioxide absorption liquid The carbon dioxide absorption liquid of the present invention is a carbon dioxide absorption liquid for separating and recovering carbon dioxide from a gas to be separated containing carbon dioxide, and contains an amine and an organic solvent.

(1-1) Primary amine The primary amine used in the present invention is not particularly limited, but primary amines with low vapor pressure at 25°C are preferred.

Specifically, from the viewpoint of easy separation and recovery of carbon dioxide using a pressure difference from the atmosphere, the vapor pressure at 25° C. of the primary amine used in the present invention is preferably 0 to 100 Pa, and preferably 0 to 50 Pa. is more preferable. For the vapor pressure of the primary amine at 25°C, if there is a previously reported literature value, the literature value is used, otherwise it is estimated from the molecular structure.

Specifically, such primary amines include monoethanolamine, diglycolamine, 2-amino-2-methyl-1-propanol, monopropanolamine, monoisopropanolamine, DL-1-amino-2 Examples include alkanolamines such as -propanol and 3-amino-1,2-propanediol. Among these, monoethanolamine, diglycolamine, etc. are preferred from the viewpoint of easy separation and recovery of carbon dioxide using a pressure difference from the atmosphere.

As the above primary amine, publicly known or commercially available products can be used. Moreover, the above can be used alone, or two or more types can be used in combination.

In addition, when using a secondary amine or tertiary amine instead of a primary amine, it is necessary to use a secondary amine or tertiary amine with a low vapor pressure, and to reduce the vapor pressure as described below. Even when a low-pressure organic solvent or ionic liquid is used, the obtained carbon dioxide absorption liquid does not react sufficiently with carbon dioxide and cannot sufficiently absorb carbon dioxide.

In the carbon dioxide absorption liquid of the present invention, the content of the above-mentioned primary amine is not particularly limited, but from the viewpoint of easy separation and recovery of carbon dioxide using a pressure difference from the atmosphere, carbon dioxide absorption The total amount of the liquid is 100% by mass, preferably 1 to 50% by mass, more preferably 5 to 40% by mass.

(1-2) Organic Solvent The organic solvent used in the present invention has a vapor pressure of 0 to 1000 Pa at 25°C. In particular, from the viewpoint of easy separation and recovery of carbon dioxide using a pressure difference from the atmosphere, the vapor pressure at 25°C of the organic solvent used in the present invention is 0 to 1000 Pa, preferably 0.01 to 100 Pa, more preferably is 0.02 to 10 Pa, more preferably 0.03 to 1 Pa. Further, as the organic solvent, an ionic liquid whose vapor pressure is substantially zero (for example, 0 to 0.005 Pa) can also be preferably used. Note that the vapor pressure of the organic solvent at 25° C. is estimated from the molecular structure if there is a previously reported literature value.

As such an organic solvent, polyols or alkyl ethers thereof, and ionic liquids are preferable from the viewpoint of easy separation and recovery of carbon dioxide using a pressure difference from the atmosphere. Among these, examples of polyols or alkyl ethers thereof include triethylene glycol, tetraethylene glycol, polyethylene glycol, and monoalkyl ethers thereof.

In addition, as an ionic liquid, from the viewpoint of easy separation and recovery of carbon dioxide using a pressure difference from the atmosphere, the cation is an imidazolinium cation, a pyridinium cation, a quaternary phosphonium cation, or a heterocyclic skeleton containing a phosphorus atom. cation (1-butyl-3-methylimidazolium, 1-butylpyridinium, etc.), and the anion is Br ⁻ , Cl ⁻ , BF ₄ ⁻ , PF ₆ ⁻ , or (CF ₃ SO ₂ ) ₂ N ⁻ Ionic liquids are preferred.

Among these, triethylene glycol, 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF ₆ ), and the like are preferred from the viewpoint of easy separation and recovery of carbon dioxide using a pressure difference from the atmosphere.

For the above organic solvents, known or commercially available products can be used. Further, the above organic solvents can be used alone or in combination of two or more.

In the carbon dioxide absorption liquid of the present invention, the content of the above-mentioned organic solvent is not particularly limited, but from the viewpoint of easy separation and recovery of carbon dioxide using a pressure difference from the atmosphere, the content of the organic solvent in the carbon dioxide absorption liquid is The total amount is 100% by weight, preferably 50 to 99% by weight, more preferably 60 to 95% by weight.

(1-3) Other components In addition to the above-mentioned primary amines and organic solvents with a vapor pressure of 0 to 1000 Pa at 25°C, the carbon dioxide absorption liquid of the present invention contains antioxidants and other substances that suppress side reactions. It is also possible to include various components such as deterioration inhibitors such as corrosion inhibitors.

Examples of side reaction inhibitors such as antioxidants include dibutylhydroxytoluene, butylhydroxyanisole, sodium erythorbate, sodium sulfite, and sulfur dioxide.

Examples of deterioration inhibitors such as corrosion inhibitors include 1-hydroxyethane-1,1-diphosphonic acid, 2-phosphonobutane-1,2,4-tricarboxylic acid, and 1-phosphonopropane-2,3-dicarboxylic acid. , phosphonosuccinic acid, 2-hydroxyphosphonoacetic acid, maleic acid-based polymers (copolymers of maleic acid and amylene; ternary copolymers of maleic acid, acrylic acid, and styrene, etc.).

These various components can be included within a range that does not impair the effects of the present invention, for example, 0.01 to 10% by mass, preferably 0.02 to 5% by mass, assuming the total amount of the carbon dioxide absorption liquid as 100% by mass. % by mass.

However, it is preferable to use as few solvents as possible, such as water, methanol, ethanol, etc., whose vapor pressure is higher than 1000 Pa at 25°C, from the viewpoint of easy separation and recovery of carbon dioxide using the pressure difference from the atmosphere. It is preferably 10% by mass, particularly 0 to 5% by mass, and more preferably 0 to 1% by mass, and most preferably does not contain a solvent with a vapor pressure of more than 1000 Pa at 25°C.

(1-4) Carbon dioxide absorption liquid The carbon dioxide absorption liquid of the present invention containing each of the above-mentioned components is not particularly limited, but can separate and recover carbon dioxide using a pressure difference from the atmosphere. From a simple viewpoint, it is preferable that the difference in CO ₂ absorption amount at 25° C. when the carbon dioxide partial pressure is 40 Pa and 10 Pa is 0.01 to 1.00 mol-CO 2 /mol-amine, and 0.01 to 1.00 mol-CO ₂ /mol-amine. 03 to 0.50 mol-CO ₂ /mol-amine, more preferably 0.05 to 0.50 mol-CO ₂ /mol-amine.

The carbon dioxide absorption liquid of the present invention containing each of the above-mentioned components is not particularly limited, but from the viewpoint of easy separation and recovery of carbon dioxide using a pressure difference from the atmosphere, the carbon dioxide absorbing liquid of the present invention can be heated at 25°C with steam. The pressure is preferably 100 Pa or less, more preferably 0.01 to 95 Pa, and even more preferably 0.02 to 90 Pa. Note that this vapor pressure can also be set to 0.03 to 20 Pa or less.

The carbon dioxide absorption liquid of the present invention containing each of the above components is not particularly limited, but from the viewpoint of easy separation and recovery of carbon dioxide using a pressure difference from the atmosphere, it is possible to absorb carbon dioxide at 25°C. The CO ₂ absorption amount (solubility) when the carbon partial pressure is 40 Pa is preferably 0.010 g-CO ₂ /g-carbon dioxide absorption liquid or more, and 0.015 to 0.100 g-CO ₂ /g. - More preferably a carbon dioxide absorption liquid, and even more preferably a 0.020 to 0.100g-CO ₂ /g-carbon dioxide absorption liquid.

The carbon dioxide absorption liquid of the present invention can absorb carbon dioxide as a gas containing carbon dioxide, in addition to the atmosphere, for example, thermal power plants using coal, heavy oil, natural gas, etc. as fuel. Exhaust gas from power plants, manufacturing plant boilers, cement factory kilns, ironmaking blast furnaces that reduce iron oxide with coke, steelmaking converters that burn the carbon in pig iron to make steel, coal gasification combined power generation facilities, tankers, etc. , natural gas during mining, reformed gas, etc. can also be used, and the carbon dioxide concentration in the gas can be generally about 0.01 to 50% by volume, particularly about 0.04 to 20% by volume. . In such a carbon dioxide concentration range, the effects of the present invention can be particularly suitably exhibited. Note that the gas containing carbon dioxide may include gases such as N ₂ , water vapor, CO, H ₂ S, COS, SO ₂ , NO ₂ , CH ₄ , and hydrogen in addition to carbon dioxide.

As explained in the separation and recovery method below, the separated and recovered carbon dioxide can be used in direct air capture (DAC) technology, which is currently being developed and which adsorbs carbon dioxide and buries it underground. Therefore, the carbon dioxide absorption liquid of the present invention as described above is particularly suitable for use in direct air capture (DAC) technology in which carbon dioxide is adsorbed and buried underground.

2. Method for separating and recovering carbon dioxide The method for separating and recovering carbon dioxide using the carbon dioxide absorption liquid of the present invention is not particularly limited;
(1) A step of bringing the carbon dioxide absorption liquid of the present invention into contact with a gas to be separated containing carbon dioxide to obtain a carbon dioxide absorption liquid that has absorbed carbon dioxide from the gas to be separated containing carbon dioxide, and
(2) This can be carried out by desorbing and dissipating carbon dioxide from the carbon dioxide-absorbing liquid obtained in step (1) above under reduced pressure and recovering the dissipated carbon dioxide.

(2-1) Process (1)
In step (1), the carbon dioxide absorption liquid of the present invention is brought into contact with the gas to be separated containing carbon dioxide, so that the carbon dioxide in the gas to be separated containing carbon dioxide is removed by the carbon dioxide absorption liquid of the present invention. absorb and separate.

The method of bringing the carbon dioxide absorption liquid of the present invention into contact with the gas to be separated containing carbon dioxide in step (1) is not particularly limited. For example, a method of bubbling the gas to be separated containing carbon dioxide into the carbon dioxide absorbing liquid of the present invention, a method of dropping the carbon dioxide absorbing liquid of the present invention in the form of a mist into the gas to be separated containing carbon dioxide (spraying or spray method), a method in which the gas to be separated containing high-pressure carbon dioxide and the carbon dioxide absorption liquid of the present invention are brought into countercurrent contact in an absorption tower containing a filler made of porcelain or metal mesh, and the like.

The temperature in step (1) can be 0 to 60°C, preferably 5 to 50°C, more preferably 10 to 40°C. Within this range, it is easy to separate and recover carbon dioxide using a pressure difference from the atmosphere, and it is also easy to achieve energy-saving direct air recovery (DAC) technology with less thermal energy.

The pressure in step (1) is assumed to be about the same as the partial pressure of carbon dioxide in the atmosphere, and from the viewpoint of easy separation and recovery of carbon dioxide using the pressure difference from the atmosphere, the pressure is, for example, 30 to 100 Pa, preferably. can be set to 32 to 80 Pa, more preferably 35 to 60 Pa.

(2-2) Process (2)
In step (2), carbon dioxide is desorbed and diffused under reduced pressure from the carbon dioxide absorption liquid of the present invention obtained in step (1) that has absorbed carbon dioxide, and the diffused carbon dioxide is recovered.

The step (2) of desorbing and diffusing carbon dioxide can be performed without excessive heating. Specifically, the temperature in step (2) of desorbing and diffusing carbon dioxide can be 0 to 60°C, preferably 5 to 50°C, and more preferably 10 to 40°C. Within this range, it is easy to separate and recover carbon dioxide using a pressure difference from the atmosphere, and it is also easy to achieve energy-saving direct air recovery (DAC) technology with less thermal energy.

The pressure in the step (2) of desorbing and dissipating carbon dioxide is, for example, 1 to 20 Pa, preferably 2 to 18 Pa, more preferably from the viewpoint of easy separation and recovery of carbon dioxide using a pressure difference from the atmosphere. can be 3 to 15 Pa.

The method of desorbing and diffusing carbon dioxide in step (2) is not particularly limited. In particular, in the present invention, since carbon dioxide can be separated and recovered using a pressure difference from the atmosphere, carbon dioxide can be desorbed and diffused by reducing the pressure to a predetermined pressure range.

In particular, from the perspective of easily achieving energy-saving direct air recovery (DAC) technology, a carbon dioxide sublimator that sublimates (solidifies) the separated carbon dioxide is used to transfer the separated carbon dioxide to a refrigerant using a fluid with cold heat. It can also be sublimated (solidified) and recovered by cooling. Dry ice produced by sublimation (solidification) of this carbon dioxide can be recovered by sublimation (vaporization) again and can be utilized as carbon dioxide gas or the like. As a device that can be used at this time, for example, the device described in International Publication No. 2021/221007 can also be used.

In step (2), the carbon dioxide absorption liquid of the present invention after dissipating carbon dioxide can be returned to step (1) again for circulation and reuse.

In addition, in the method for separating and recovering carbon dioxide using a carbon dioxide absorption liquid of the present invention, a method for separating and recovering carbon dioxide using a pressure difference from the atmosphere has been described. It is also possible to separate and recover carbon dioxide using the difference.

The carbon dioxide separated and recovered by the carbon dioxide separation and recovery method using a carbon dioxide absorption liquid of the present invention usually has a volume concentration of 95 to 100%, and can be pure or very highly concentrated. The separated and recovered carbon dioxide can be applied to direct air capture (DAC) technology, which is currently being developed and which adsorbs carbon dioxide and buries it underground. Other uses of the separated and recovered carbon dioxide are not particularly limited. Examples include synthetic raw materials such as chemical products, refrigerants for freezing foods, and the like.

Hereinafter, the present invention will be explained in more detail with reference to Examples. However, the present invention is not limited to these Examples.

In addition, the vapor pressure at 25° C. was quoted from a literature value.

Reagents and Solvents Reagents and solvents used in Examples and Comparative Examples are shown below.

Example 1
30% by mass of monoethanolamine and 70% by mass of triethylene glycol were mixed to obtain the carbon dioxide absorption liquid of Example 1.

Example 2
A carbon dioxide absorption liquid of Example 2 was obtained by mixing 10% by mass of monoethanolamine and 90% by mass of triethylene glycol.

Example 3
30% by mass of diglycolamine and 70% by mass of triethylene glycol were mixed to obtain the carbon dioxide absorption liquid of Example 3.

Example 4
30% by mass of monopropanolamine and 70% by mass of triethylene glycol were mixed to obtain the carbon dioxide absorption liquid of Example 4.

Example 5
30% by mass of diglycolamine and 70% by mass of 1-butyl-3-methylimidazolium hexafluorophosphate were mixed to obtain the carbon dioxide absorption liquid of Example 5.

Comparative example 1
A carbon dioxide absorption liquid of Comparative Example 1 was obtained by mixing 30% by mass of diethanolamine and 70% by mass of triethylene glycol.

Comparative example 2
A carbon dioxide absorption liquid of Comparative Example 2 was obtained by mixing 30% by mass of monoethanolamine and 70% by mass of water.

Comparative example 3
A carbon dioxide absorption liquid of Comparative Example 3 was obtained by mixing 30% by mass of diethanolamine and 70% by mass of water.

Test method (vapor pressure)
Table 3 shows the vapor pressure at 25° C. of the carbon dioxide absorption liquids obtained in Examples 1 to 5 and Comparative Examples 1 to 3.

(carbon dioxide absorption amount)
It was found that the carbon dioxide absorption liquid of Comparative Example 2 had a high vapor pressure at 25° C., and because it volatilized, it was found that it was not suitable as a carbon dioxide absorption liquid in which carbon dioxide is separated and recovered by a pressure difference.

Next, the carbon dioxide absorption amount of the carbon dioxide absorption liquids obtained in Examples 1 to 5 and Comparative Examples 1 to 3 was measured at 25° C. when the carbon dioxide partial pressure was 10 Pa and 40 Pa. Measurements were performed by headspace gas chromatography. The results are shown in Table 4 and Figure 1. Note that FIG. 1 shows the relationship between carbon dioxide partial pressure and carbon dioxide absorption amount at 25° C., 30° C., and 40° C. in the carbon dioxide absorption liquid of Example 3. Furthermore, in FIG. 1, the calculated carbon dioxide absorption amount of the carbon dioxide absorption liquid of Example 3 is shown by a broken line, and the actual measured value is shown by a marker.

As a result, in Examples 1 to 5, even at 25°C, it is difficult to volatilize, and there is a large difference in the amount of carbon dioxide absorbed when the partial pressure of carbon dioxide is 10 Pa and 40 Pa. It has been suggested that carbon dioxide can be separated and recovered. On the other hand, in Comparative Examples 1 and 3, although it is difficult to volatilize, there is almost no difference in the amount of carbon dioxide absorbed when the carbon dioxide partial pressure is 10 Pa and 40 Pa, and it is possible to separate and recover carbon dioxide using the pressure difference from the atmosphere. It has been suggested that this is not possible. Furthermore, as described above, Comparative Example 2 has a high vapor pressure and evaporates, so it is not suitable as a carbon dioxide absorption liquid in which carbon dioxide is separated and recovered by a pressure difference.

Claims (15)

A carbon dioxide absorption liquid for separating and recovering carbon dioxide from a gas to be separated containing carbon dioxide,
contains a primary amine and an organic solvent, and
The organic solvent is a carbon dioxide absorption liquid having a vapor pressure of 0 to 1000 Pa at 25°C. The carbon dioxide absorption according to claim 1, wherein the difference in CO ₂ absorption amount when the carbon dioxide partial pressure is 40 Pa and 10 Pa at 25° C. is 0.01 to 1.00 mol-CO ₂ /mol-amine. liquid. The carbon dioxide absorption liquid according to claim 1, wherein the vapor pressure of the carbon dioxide absorption liquid is 100 Pa or less at 25°C. The carbon dioxide according to claim 1, wherein at 25° C., the CO ₂ absorption amount when the carbon dioxide partial pressure of the carbon dioxide absorption liquid is 40 Pa is 0.010 g-CO ₂ /g-carbon dioxide absorption liquid or more. Carbon absorption liquid. The carbon dioxide absorption liquid according to claim 1, wherein the primary amine is a primary alkanolamine. The primary alkanolamine is monoethanolamine, diglycolamine, 2-amino-2-methyl-1-propanol, monopropanolamine, monoisopropanolamine, DL-1-amino-2-propanol, and 3-amino The carbon dioxide absorption liquid according to claim 5, which is at least one selected from the group consisting of -1,2-propanediol. The carbon dioxide absorption liquid according to claim 1, wherein the organic solvent is at least one selected from the group consisting of polyols or alkyl ethers thereof, and ionic liquids. The organic solvent is triethylene glycol, tetraethylene glycol, polyethylene glycol, and monoalkyl ethers thereof,
The cation is an imidazolinium cation, a quaternary phosphonium cation, or a cation having a heterocyclic skeleton containing a phosphorus atom, and the anion is Br ⁻ , Cl ⁻ , BF ₄ ⁻ , PF ₆ ⁻ , or (CF ₃ SO ₂ ). 8. The carbon dioxide absorption liquid according to claim 7, which is at least one selected from the group consisting of ₂ N ^- ionic liquid. The carbon dioxide absorption liquid according to claim 1, wherein the content of the primary amine is 1 to 50% by mass, assuming a total amount of the carbon dioxide absorption liquid as 100% by mass. The carbon dioxide absorption liquid according to claim 1, wherein the content of the organic solvent is 50 to 99% by mass, where the total amount of the carbon dioxide absorption liquid is 100% by mass. The carbon dioxide absorption liquid according to any one of claims 1 to 10, which is used for direct air recovery technology in which carbon dioxide is adsorbed and buried underground. A method for separating and recovering carbon dioxide from a gas to be separated containing carbon dioxide, the method comprising:
(1) Carbon dioxide obtained by bringing the carbon dioxide absorption liquid according to any one of claims 1 to 10 into contact with a gas to be separated containing carbon dioxide, and absorbing carbon dioxide from the gas to be separated containing carbon dioxide. obtaining an absorption liquid, and
(2) A method comprising a step of desorbing and dissipating carbon dioxide from the carbon dioxide absorption liquid obtained in step (1) above under reduced pressure and recovering the dissipated carbon dioxide. The method according to claim 12, wherein the step (2) is a step of sublimating carbon dioxide under reduced pressure from a carbon dioxide absorption liquid that has absorbed carbon dioxide. The method according to claim 12, wherein the steps (1) and (2) are performed at 0 to 60°C. The method according to claim 12, wherein the step (1) is carried out under a pressure of a carbon dioxide partial pressure of 30 to 100 Pa, and the step (2) is carried out under a pressure of a carbon dioxide partial pressure of 1 to 20 Pa.

Images