Antioxidant, carbon dioxide absorbing solution, carbon dioxide separation method, carbon dioxide separation / recovery method, and device using carbon dioxide absorbing solution

Abstract

The present invention provides: a carbon dioxide absorbing solution that has superior oxidation resistance over the prior art and that has excellent carbon dioxide absorption performance; a carbon dioxide absorbing solution that in addition to the above performance makes it possible to easily separate carbon dioxide when recycling the absorbing solution; a carbon dioxide separation method and carbon dioxide separation / recovery method that use the carbon dioxide absorbing solution; and a device using the carbon dioxide absorbing solution. The present invention relates to a carbon dioxide absorbing solution comprising a carbon dioxide absorbing material, an antioxidant, and a solvent, wherein the antioxidant is a phosphine compound represented by general formula (1) (in the formula, a, b, and c each represent an integer of 1-10, and R1, R2, and R3 each independently represent an amino group or a hydroxy group).

Description

Antioxidant, carbon dioxide absorbent, carbon dioxide separation method, carbon dioxide separation and recovery method, and apparatus using carbon dioxide absorbent

[0001] The present invention relates to an antioxidant, a carbon dioxide absorbent, a carbon dioxide separation method, a carbon dioxide separation and recovery method, and an apparatus using a carbon dioxide absorbent.

[0002] In recent years, increased consumption of fossil fuels such as oil and coal due to industrial activities, as well as deforestation, has led to a continuous increase in the concentration of greenhouse gases such as carbon dioxide and methane in the atmosphere, resulting in global warming. If this warming continues at this rate, it is believed that serious consequences will appear in various aspects of life, including desertification of the Earth's surface, rising sea levels, and changes in ecosystems.

[0003] In this context, technologies for reducing carbon dioxide emissions and capturing carbon dioxide are attracting attention as a way to prevent global warming and reduce greenhouse gas emissions. Technologies for capturing carbon dioxide include chemical absorption, physical absorption, solid absorption, and membrane separation, but chemical absorption is mainly used because it can handle a wide range of concentrations. This chemical absorption method involves absorbing carbon dioxide into a liquid through a chemical reaction, and then releasing and capturing the carbon dioxide by heating the absorbent liquid.

[0004] As a liquid used to absorb carbon dioxide, for example, Patent Document 1 discloses an ionic liquid having one or more primary or secondary amino groups in the cation and an ethylenediamine or propylenediamine skeleton of amino acid.

[0005] Japanese Patent Publication No. 2016-10760

[0006] The acidic gas chemical absorbent described in Patent Document 1 can absorb a large amount of carbon dioxide at room temperature, but it has the problem of being prone to oxidative degradation when repeatedly used in an oxidizing atmosphere such as air.

[0007] In addition, there is a need for a novel antioxidant that can prevent oxidation in various liquid compositions such as carbon dioxide absorption liquids, water-based paints, emulsion paints, coating agents, adhesives, fiber treatment agents, softeners, inks, lubricating oils, and sealants.

[0008] Therefore, an object of the present invention is to provide a carbon dioxide absorption liquid that is more excellent in oxidation resistance than conventional ones and has excellent carbon dioxide absorption performance, and further, a carbon dioxide absorption liquid that can easily desorb carbon dioxide when regenerating the absorption liquid, a carbon dioxide separation method using the carbon dioxide absorption liquid, a carbon dioxide separation and recovery method, and an apparatus using the carbon dioxide absorption liquid. Another object of the present invention is to provide an antioxidant for a novel liquid composition.

[0009] As a result of intensive studies in view of the above circumstances, the present inventors have found that a carbon dioxide absorption liquid containing a phosphine compound represented by the following general formula (1) as an antioxidant is more excellent in oxidation resistance than conventional ones, has excellent carbon dioxide absorption performance, and can easily desorb carbon dioxide when regenerating the carbon dioxide absorption liquid, thus completing the present invention.

[0010]

[0011] (In the formula, a, b, and c represent integers of 1 or more and 10 or less, and R １ , R ２ and R ３ each independently represents an amino group or a hydroxy group.)

[0012] That is, the present invention (1) provides an antioxidant characterized by being a phosphine compound represented by the following general formula (1):

[0013]

[0014] (In the formula, a, b, and c represent integers of 1 or more and 10 or less, and R １ , R ２ and R ３ each independently represents an amino group or a hydroxy group.)

[0015] Further, the present invention (2) includes a carbon dioxide absorption material, a solvent, and an antioxidant, and the antioxidant is represented by the following general formula (1):

[0016]

[0017] (In the formula, a, b, and c represent integers of 1 or more and 10 or less, and R １ , R ２ and R ３ each independently represent an amino group or a hydroxy group.) The present invention provides a carbon dioxide absorption liquid characterized by being a phosphine compound represented by the formula.

[0018] Further, the present invention (3) has a carbon dioxide separation step of separating carbon dioxide from a mixed gas by bringing the mixed gas containing carbon dioxide into contact with the carbon dioxide absorption liquid of the present invention (2) to absorb carbon dioxide in the mixed gas into the carbon dioxide absorption liquid.

[0019] Further, the present invention (4) includes a carbon dioxide separation step of separating carbon dioxide from a mixed gas by bringing the mixed gas containing carbon dioxide into contact with the carbon dioxide absorption liquid of the present invention (2) to absorb carbon dioxide in the mixed gas into the carbon dioxide absorption liquid, and heating the carbon dioxide absorption liquid that has absorbed carbon dioxide in the carbon dioxide separation step at a temperature of 50°C or higher and 150°C or lower to desorb carbon dioxide from the carbon dioxide absorption liquid that has absorbed carbon dioxide, thereby regenerating the carbon dioxide absorption liquid and recovering the desorbed carbon dioxide.

[0020] Further, the present invention (5) provides an apparatus characterized by using the carbon dioxide absorption liquid of the present invention (2).

[0021] According to the present invention, it is possible to provide a carbon dioxide absorbing liquid that has superior oxidation resistance and carbon dioxide absorption performance compared to conventional liquids, and that allows carbon dioxide to be easily desorbed when the carbon dioxide absorbing liquid is regenerated, a carbon dioxide separation method using the carbon dioxide absorbing liquid of the present invention, a carbon dioxide separation and recovery method, and an apparatus using the carbon dioxide absorbing liquid of the present invention. Furthermore, an object of the present invention is to provide a novel antioxidant for liquid compositions.

[0022] The present invention will be described below based on preferred embodiments. The antioxidant of the present invention is given by the following general formula (1):

[0023]

[0024] (In the formula, a, b, and c represent integers between 1 and 10, and R １ , R ２ and R ３ The antioxidant is characterized by being a phosphine compound represented by (where each independently represents an amino group or a hydroxyl group).

[0025] In general formula (1), a, b, and c represent integers between 1 and 10, preferably between 1 and 4, and more preferably between 3 and 4. The numbers a, b, and c may be the same or different, but it is preferable that they be the same from the viewpoint of facilitating synthesis. In the present invention, it is particularly preferable that a, b, and c are each 3 from the viewpoint of industrial availability.

[0026] R in general formula (1) １ , R ２ and R ３ Each of these independently forms an amino group (-NH ２ R represents a hydroxyl group (-OH). １ , R ２ and R ３ These may be the same or different, but it is preferable that they be the same from the viewpoint of facilitating synthesis. In other words, R １ , R ２ and R ３ Preferably, all of these are amino groups or hydroxyl groups.

[0027] The antioxidant of the present invention is used, for example, as an antioxidant for liquid compositions. That is, the antioxidant of the present invention functions as an antioxidant by dissolving in the solvent of a liquid composition. The solvent of the liquid composition is not particularly limited, but examples include water, alcohol-based solvents, mixed solvents of water and alcohol, glycol-based solvents, etc., and water is preferred.

[0028] Applications of the antioxidant of the present invention include antioxidants for aqueous paints, emulsion paints, coatings, adhesives, textile treatments, softeners, inks, lubricants, sealants, carbon dioxide absorbers, and the like. The amount of the antioxidant of the present invention added to a liquid composition is preferably determined by testing or other means to determine a suitable amount depending on the type and amount of the substance to be oxidized.

[0029] The carbon dioxide absorbent liquid of the present invention comprises a carbon dioxide absorbent material, a solvent, and an antioxidant, wherein the antioxidant is of the following general formula (1):

[0030]

[0031] (In the formula, a, b, and c represent integers between 1 and 10, and R １ , R ２ and R ３ The carbon dioxide absorbent is characterized by being a phosphine compound represented by (where each independently represents an amino group or a hydroxyl group).

[0032] In the carbon dioxide absorbing liquid of the present invention, the carbon dioxide absorbing material is a material that can absorb carbon dioxide by reacting with carbon dioxide. From the viewpoint of carbon dioxide absorption performance, the carbon dioxide absorbing material is preferably a compound having an amino group.

[0033] Examples of compounds containing an amino group include monoethanolamine, diethanolamine, methyldiethanolamine, diethylenetriamine, triethylenediamine, triethylenetetramine, piperazine, and tris(3-aminopropyl)phosphine oxide. Among these, diethylenetriamine, triethylenetetramine, and tris(3-aminopropyl)phosphine oxide are preferred because, although they are prone to oxidative degradation, they have excellent carbon dioxide absorption capabilities.

[0034] These carbon dioxide absorbing materials may be used individually or in combination of two or more types, as long as they do not affect the performance of the carbon dioxide absorbing liquid.

[0035] In the carbon dioxide absorbent liquid of the present invention, suitable solvents include water, glycol-based solvents, alcohol-based solvents, amine compounds, and alkanolamine compounds. Among these, water, glycol-based solvents, and alcohol-based solvents are preferred because they do not easily increase the viscosity of the carbon dioxide absorbent liquid after carbon dioxide absorption and offer good handling properties.

[0036] Examples of glycol-based solvents include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, and glycerin.

[0037] These solvents may be used individually or in mixtures of two or more types.

[0038] In the carbon dioxide absorbent solution of the present invention, the antioxidant is a phosphine compound represented by general formula (1). In other words, the carbon dioxide absorbent solution of the present invention is in the form of a solution containing a phosphine compound represented by general formula (1) as an antioxidant. The phosphine compound represented by general formula (1) in the carbon dioxide absorbent solution of the present invention is the same as the phosphine compound represented by general formula (1) in the antioxidant of the present invention.

[0039] The phosphine compound represented by general formula (1) is more easily oxidized than the carbon dioxide absorbent material. Therefore, when repeatedly used in an oxidizing atmosphere such as air, it is preferentially oxidized over the carbon dioxide absorbent material, preventing the carbon dioxide absorbent material from degrading.

[0040] In general formula (1), a, b, and c represent integers between 1 and 10, preferably between 1 and 4, and more preferably between 3 and 4. The numbers a, b, and c may be the same or different, but it is preferable that they be the same from the viewpoint of facilitating synthesis. In the present invention, it is particularly preferable that a, b, and c are each 3 from the viewpoint of industrial availability.

[0041] R in general formula (1) １ , R ２ and R ３ Each of these independently forms an amino group (-NH ２ R represents a hydroxyl group (-OH). １ , R ２ and R ３ These may be the same or different, but it is preferable that they be the same from the viewpoint of facilitating synthesis. In other words, R １ , R ２ and R ３ Preferably, all of these are amino groups or hydroxyl groups.

[0042] In the carbon dioxide absorbent liquid of the present invention, the phosphine compound represented by general formula (1), when it has at least one amino group, has the function of absorbing carbon dioxide in addition to functioning as an antioxidant. Therefore, in the carbon dioxide absorbent liquid of the present invention, from the viewpoint of carbon dioxide absorption performance, R in general formula (1) １ , R ２ and R ３ Preferably, at least one of them is an amino group, and more preferably, all of them are amino groups.

[0043] In the carbon dioxide absorbent liquid of the present invention, the content of the carbon dioxide absorbent material in the carbon dioxide absorbent liquid is 5% by mass or more and 60% by mass or less, preferably 10% by mass or more and 50% by mass or less. By having the content of the carbon dioxide absorbent material in the carbon dioxide absorbent liquid within the above range, the carbon dioxide absorbent liquid has excellent oxidation resistance and excellent carbon dioxide absorption performance.

[0044] In the carbon dioxide absorbent liquid of the present invention, the content of the phosphine compound represented by general formula (1) in the carbon dioxide absorbent liquid is 1% by mass or more and 30% by mass or less, preferably 1% by mass or more and 10% by mass or less. By having the content of the phosphine compound represented by general formula (1) in the carbon dioxide absorbent liquid within the above range, the carbon dioxide absorbent liquid has excellent oxidation resistance and excellent carbon dioxide absorption performance.

[0045] In the carbon dioxide absorbent liquid of the present invention, the mass ratio of the phosphine compound represented by general formula (1) to the carbon dioxide absorbent material (phosphine compound represented by general formula (1): carbon dioxide absorbent material) is preferably 1:100 to 1:1, more preferably 1:20 to 1:5.

[0046] Because the carbon dioxide absorbent of the present invention is in the form of a solution, it is suitably used for separating and recovering carbon dioxide emitted from large-scale carbon dioxide sources such as power plants (including coal-fired and natural gas-fired power plants), chemical plants, waste treatment plants, and steel mills, from the viewpoint of ease of acquisition and safety. Because the carbon dioxide absorbent of the present invention is a solution, it can be used in existing carbon dioxide absorbent equipment in large-scale facilities and factories where high concentrations of carbon dioxide are present and large-scale processing is required. Furthermore, because the carbon dioxide absorbent of the present invention is a solution, it is easy to transport to and fill into large-scale carbon dioxide separation and recovery equipment, or to remove from equipment.

[0047] The carbon dioxide absorbent liquid of the present invention can separate and recover carbon dioxide from a mixed gas containing carbon dioxide. The other components of the mixed gas are not particularly limited, as long as the gas contains carbon dioxide. Examples of the other components include oxygen, nitrogen, carbon monoxide, nitric oxide, nitrogen dioxide, dinitrogen monoxide, dinitrogen trioxide, dinitrogen tetroxide, dinitrogen pentoxide, sulfur monoxide, sulfur dioxide, sulfur trioxide, phosphoric acid, sulfuric acid, nitric acid, hydrochloric acid, water, etc. The concentration of carbon dioxide in the mixed gas is not particularly limited and may be a high concentration with a purity of about 100%, or it may be a concentration similar to that found in the atmosphere.

[0048] The carbon dioxide absorbent of the present invention is useful as an absorbent for separating and recovering carbon dioxide from mixed gases containing carbon dioxide emitted from sources such as power plants (coal-fired and natural gas-fired), factories (chemical plants, waste treatment plants, steel mills, etc.), and transportation equipment (automobiles, aircraft, ships, etc.). It is also useful as an absorbent used in DAC (Direct Air Capture) devices that directly separate and recover carbon dioxide from the atmosphere. In other words, the carbon dioxide absorbent of the present invention is suitable as a carbon dioxide absorbent used in various devices such as equipment used in power plants, factories, and transportation equipment, as well as DAC devices.

[0049] Next, a method for separating carbon dioxide and a method for separating and recovering carbon dioxide using the carbon dioxide absorption liquid of the present invention will be described.

[0050] The present invention relates to a carbon dioxide separation method characterized by having a carbon dioxide separation step (A) in which a mixed gas containing carbon dioxide is brought into contact with a carbon dioxide absorption liquid of the present invention, and the carbon dioxide in the mixed gas is absorbed by the carbon dioxide absorption liquid, thereby separating the carbon dioxide from the mixed gas.

[0051] The present invention provides a carbon dioxide separation and recovery method comprising: a carbon dioxide separation step (A) in which a mixed gas containing carbon dioxide is brought into contact with a carbon dioxide absorption liquid of the present invention, and the carbon dioxide in the mixed gas is absorbed by the carbon dioxide absorption liquid, thereby separating the carbon dioxide from the mixed gas; and a carbon dioxide recovery step (B) in which the carbon dioxide absorption liquid that has absorbed carbon dioxide in the carbon dioxide separation step is heated at a temperature of 50°C to 150°C, thereby decarbonizing the carbon dioxide that has absorbed carbon dioxide, thereby regenerating the carbon dioxide absorption liquid and recovering the decarbonized carbon dioxide.

[0052] In the carbon dioxide separation method and the carbon dioxide separation and recovery method of the present invention, the step of separating carbon dioxide from a mixed gas containing carbon dioxide is the carbon dioxide separation step (A) in both cases and is the same.

[0053] The carbon dioxide separation step (A) is a step in which the carbon dioxide absorption liquid of the present invention is brought into contact with a mixed gas containing carbon dioxide, thereby allowing the carbon dioxide absorption liquid of the present invention to absorb the carbon dioxide in the mixed gas.

[0054] One example of the carbon dioxide separation process (A) is to supply a mixed gas containing carbon dioxide to an absorption tower filled with the carbon dioxide absorption liquid of the present invention, bring the mixed gas into contact with the carbon dioxide absorption liquid, and separate the carbon dioxide from the mixed gas by allowing the carbon dioxide absorption liquid to absorb the carbon dioxide in the mixed gas. In this form of carbon dioxide separation process (A), the mixed gas is brought into contact with the carbon dioxide absorption liquid by supplying the mixed gas to the absorption tower, and the mixed gas that has been in contact with the carbon dioxide absorption liquid inside the absorption tower is discharged from the absorption tower. Furthermore, the method of filling the absorption tower with the carbon dioxide absorption liquid of the present invention is not particularly limited and can be carried out under atmospheric pressure or reduced pressure.

[0055] The temperature of the carbon dioxide absorbent in the carbon dioxide separation step (A) is not limited as long as the carbon dioxide absorbent can perform its function, but a temperature of -20°C to 60°C, and particularly 0°C to 40°C, is preferable from the viewpoint of more efficient carbon dioxide absorption.

[0056] The pressure (absolute pressure) in the carbon dioxide separation process (A) is not particularly limited and can be carried out under atmospheric pressure.

[0057] In the carbon dioxide separation step (A), the carbon dioxide-containing mixed gas comes into contact with the carbon dioxide absorbent, causing the carbon dioxide in the mixed gas to be absorbed by the carbon dioxide absorbent of the present invention, thereby separating the carbon dioxide from the mixed gas. In addition, the carbon dioxide separation step (A) yields a carbon dioxide absorbent that has absorbed carbon dioxide.

[0058] The carbon dioxide separation and recovery method of the present invention includes a carbon dioxide recovery step (B) in which carbon dioxide is recovered while regenerating the carbon dioxide absorbent liquid that absorbed carbon dioxide in the carbon dioxide separation step. The carbon dioxide recovery step (B) is a step in which carbon dioxide is removed from the carbon dioxide absorbent liquid that absorbed carbon dioxide in the carbon dioxide separation step (A) by heating the carbon dioxide absorbent liquid.

[0059] Examples of carbon dioxide recovery processes (B) include a method in which, after performing the carbon dioxide separation process (A), the carbon dioxide absorbent liquid filled in the absorption tower is heated to regenerate the carbon dioxide absorbent liquid and recover the desorbed carbon dioxide; and a method in which, after performing the carbon dioxide separation process (A), the carbon dioxide absorbent liquid that has absorbed carbon dioxide is transported to a regeneration tower, where the carbon dioxide absorbent liquid is heated to regenerate the carbon dioxide absorbent liquid and recover the desorbed carbon dioxide.

[0060] In the carbon dioxide recovery step (B), the heating temperature of the carbon dioxide absorbent is 50°C to 150°C, preferably 80°C to 140°C. Generally, the higher the heating temperature, the easier it is for carbon dioxide to be released from the carbon dioxide absorbent. In the carbon dioxide absorbent of the present invention, carbon dioxide can be released at a temperature of 50°C to 150°C, preferably 80°C to 140°C, and at a temperature equivalent to or higher than the temperature of the carbon dioxide separation step (A).

[0061] In carbon dioxide recovery step (B), the pressure (absolute pressure) is not particularly limited, and the carbon dioxide absorbent liquid that has absorbed carbon dioxide may be heated under atmospheric pressure or under reduced pressure. When heated under reduced pressure, the pressure (absolute pressure) is preferably 85 kPa or less, more preferably 60 kPa or less, from the viewpoint of preventing oxidation of the carbon dioxide absorbent liquid, and further preferably 50 kPa or less, particularly 10 kPa or less, from the viewpoint of efficiently desorbing carbon dioxide from the carbon dioxide absorbent liquid. In addition, in carbon dioxide recovery step (B), the heating temperature may be set to a temperature above the boiling point of the solvent, and the carbon dioxide absorbent liquid that has absorbed carbon dioxide may be heated under reflux of the solvent. In addition, in carbon dioxide recovery step (B), the carbon dioxide absorbent liquid that has absorbed carbon dioxide may be heated while bubbling air, an inert gas, water vapor, etc. into the carbon dioxide absorbent liquid.

[0062] In the carbon dioxide separation and recovery method of the present invention, the carbon dioxide separation step (A) and the carbon dioxide recovery step (B) can be repeated two or more times by using the regenerated carbon dioxide absorbent obtained in the carbon dioxide recovery step (B) as the carbon dioxide absorbent to which a mixed gas containing carbon dioxide is contacted in the carbon dioxide separation step (A). For example, when repeating the carbon dioxide separation step (A) and the carbon dioxide recovery step (B) twice, the process is carried out as follows: "carbon dioxide separation step (A) → carbon dioxide recovery step (B) → carbon dioxide separation step (A) → carbon dioxide recovery step (B)". The carbon dioxide separation step (A) and the carbon dioxide recovery step (B) can be repeated as long as the carbon dioxide absorption performance is sustained.

[0063] In the carbon dioxide separation method and carbon dioxide separation and recovery method of the present invention, the carbon dioxide absorbent liquid of the present invention, which has excellent oxidation resistance and chemical absorption properties, is used for the absorption and desorption of carbon dioxide. Therefore, even in an oxidizing atmosphere such as air, the removal efficiency and regeneration rate of carbon dioxide in the mixed gas are excellent.

[0064] The carbon dioxide separation method and carbon dioxide separation and recovery method of the present invention are suitably used when separating or recovering carbon dioxide from mixed gases containing carbon dioxide emitted from, for example, power plants such as coal-fired power plants and natural gas-fired power plants, factories such as chemical plants, waste treatment facilities and steel mills, and transportation equipment such as automobiles, aircraft and ships. They are also suitably used when separating or recovering carbon dioxide directly from the atmosphere.

[0065] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[0066] (Synthesis Example 1: Tris(3-aminopropyl)phosphine) In a 1L stainless steel autoclave equipped with a stirrer, thermometer, injection pump, safety valve, and gas inlet pipe, 150ml of toluene and 133g (2.33 mol) of allylamine were charged, and the system was purged three times with nitrogen gas and vacuum. Then, 22g (0.65 mol) of phosphine gas manufactured by Nippon Chemical Industrial Co., Ltd. with a purity of 99.9% was charged. At this time, when the temperature was raised to 80°C using a water bath, the gauge pressure was 0.93 MPa (absolute pressure 1.03 MPa). Next, 1.06g (0.006 mol) of azobisisobutyronitrile was dissolved in 150ml of toluene and injected in stages over 6 hours, followed by overnight aging at 80°C. At this time, the gauge pressure was 0.01 MPa (absolute pressure 0.11 MPa). After overnight aging, the system was cooled to room temperature, the remaining gas was exhausted into an exhaust system, and the system was further purged with nitrogen gas and vacuum. Then, by transferring the liquid to a pear-shaped flask under reduced pressure, 585 g of a colorless, transparent liquid was obtained. Next, the obtained colorless, transparent liquid was heated under reduced pressure (gauge pressure 4 kPa (absolute pressure 105.3 kPa), 80°C) to remove excess allylamine and toluene. The vacuum and temperature were then increased and the mixture was heated further (gauge pressure 0.2 kPa (absolute pressure 101.5 kPa), 160°C). When the first distillate began to appear, heating was stopped, and the residue in the vessel was used as the product. After cooling the obtained product to room temperature, it was purged with nitrogen gas to obtain 120 g of a colorless, transparent liquid. The NMR identification data of the obtained colorless, transparent liquid is as follows: (Identification Data) ３１ P-NMR (D ２ O); -29.73ppm １ H-NMR (D ２O); 1.40 to 1.46 ppm (m, 6H, -CH ２ -), 1.52 to 1.61 ppm (m, 6H, P-CH ２ -), 2.63 to 2.71 ppm (m, 6H, -CH ２ -NH ２ ), 4.67ppm (s, 6H, -NH ２ As a result, it was confirmed to be tris(3-aminopropyl)phosphine.

[0067] (Synthesis Example 2: Tris(3-aminopropyl)phosphine oxide) Next, a 1 L four-necked flask equipped with a stirrer and thermometer was purged with nitrogen gas. 92.4 g (0.45 mol) of tris(3-aminopropyl)phosphine obtained in Synthesis Example 1 and 500 ml of pure water were charged, and 56.1 g (0.495 mol) of 30% hydrogen peroxide diluted with 100 ml of pure water was added dropwise over 1 hour while maintaining the temperature at 70-75°C. After aging for 1 hour, the mixture was cooled to room temperature and concentrated under reduced pressure using an evaporator to remove water, yielding 100.8 g of a colorless, transparent liquid. The NMR identification data of the obtained colorless, transparent liquid is as follows. (Identification Data) ３１ P-NMR (D ２ O); 60.77ppm １ H-NMR (D ２ O); 1.50 to 1.58 ppm (m, 6H, -CH ２ -), 1.71 to 1.77 ppm (m, 6H, P-CH ２ -), 2.57 to 2.60 ppm (t, 6H, -CH ２ -NH ２ ), 4.70ppm (s, 6H, -NH ２ As a result, it was confirmed to be tris(3-aminopropyl)phosphine oxide.

[0068] (Example 1) Tris(3-aminopropyl)phosphine oxide obtained in Synthesis Example 2 and tris(3-aminopropyl)phosphine obtained in Synthesis Example 1 were dissolved in pure water. A carbon dioxide absorbent solution was then prepared so that the tris(3-aminopropyl)phosphine oxide content was 30% by mass and the tris(3-aminopropyl)phosphine content was 10% by mass. The obtained carbon dioxide absorbent solution was evaluated in regeneration test 1 described later.

[0069] (Example 2) Diethylenetriamine and tris(3-aminopropyl)phosphine obtained in Synthesis Example 1 were dissolved in pure water. A carbon dioxide absorbent solution was then prepared so that the diethylenetriamine content was 30% by mass and the tris(3-aminopropyl)phosphine content was 10% by mass. The obtained carbon dioxide absorbent solution was evaluated in regeneration test 1 described later.

[0070] (Example 3) Diethylenetriamine and tris(3-aminopropyl)phosphine obtained in Synthesis Example 1 were dissolved in pure water. A carbon dioxide absorbent solution was then prepared so that the diethylenetriamine content was 40% by mass and the tris(3-aminopropyl)phosphine content was 10% by mass. The obtained carbon dioxide absorbent solution was evaluated in Regeneration Test 1, which will be described later. Furthermore, the carbon dioxide absorbent solution after the 7th regeneration in Regeneration Test 1 was subjected to phosphorus-31 nuclear magnetic resonance spectroscopy, which will be described later (hereinafter, ３１ The analysis was performed using P-NMR (also referred to as P-NMR).

[0071] (Example 4) Diethylenetriamine and tris(3-aminopropyl)phosphine obtained in Synthesis Example 1 were dissolved in pure water. A carbon dioxide absorbent solution was then prepared so that the diethylenetriamine content was 50% by mass and the tris(3-aminopropyl)phosphine content was 10% by mass. The obtained carbon dioxide absorbent solution was evaluated in regeneration test 1 described later.

[0072] (Example 5) Diethylenetriamine and tris(3-hydroxypropyl)phosphine (manufactured by Nippon Chemical Industrial Co., Ltd., Hishikorin® P-500) were dissolved in pure water. A carbon dioxide absorbent solution was then prepared so that the diethylenetriamine content was 40% by mass and the tris(3-hydroxypropyl)phosphine content was 10% by mass. The obtained carbon dioxide absorbent solution was evaluated in regeneration test 1 described later.

[0073] (Comparative Example 1) Diethylenetriamine was dissolved in pure water to obtain a carbon dioxide absorbent solution with a diethylenetriamine content of 40% by mass. The obtained carbon dioxide absorbent solution was evaluated in regeneration test 1 described later.

[0074] (Reference Example 1) Tris(3-aminopropyl)phosphine oxide obtained in Synthesis Example 2 was dissolved in pure water to obtain a carbon dioxide absorbent solution prepared so that the tris(3-aminopropyl)phosphine oxide content was 40% by mass. The obtained carbon dioxide absorbent solution was evaluated in regeneration test 1 described later.

[0075] (Evaluation) (Regeneration Test 1) The carbon dioxide absorption solutions obtained in Examples 1-5, Comparative Example 1, and Reference Example 1 were placed in 50 ml Erlenmeyer flasks, and 99.995% pure carbon dioxide gas was blown in at a flow rate of 1 L / min at room temperature (25°C). After 15 minutes, the weight was accurately measured to a sensitivity of 0.1 mg. The increased weight was used as the amount of carbon dioxide absorbed, and the number of moles was calculated. The absorption capacity was determined as the amount of carbon dioxide absorbed per gram of carbon dioxide absorption solution. Next, carbon dioxide absorption solutions, which had absorbed carbon dioxide by blowing gas into the flasks at a flow rate of 100 ml / min from an air pump, were heated in an oil bath while being stirred. The solution was heated for 2 hours from the point when the liquid temperature reached 100°C, and carbon dioxide was expelled while refluxing water in a condenser to regenerate it. Then, pure water was added to the carbon dioxide absorption solution to make it the same weight as the water lost during heating, and the carbon dioxide absorption and regeneration process was repeated multiple times. The regeneration rate was calculated using the following formula based on the number of moles of carbon dioxide absorbed. The results are shown in Tables 1-6. Regeneration rate (%) = (Number of moles of carbon dioxide absorbed during regeneration / Number of moles of carbon dioxide absorbed initially) × 100

[0076]

[0077]

[0078]

[0079]

[0080]

[0081]

[0082]

[0083] The results of regeneration test 1 confirmed that the carbon dioxide absorbent solutions of Examples 1 to 5 exhibited excellent absorption capacity and regeneration rate even after repeated carbon dioxide absorption and regeneration cycles, and also demonstrated excellent oxidation resistance.

[0084] ( ３１ (P-NMR analysis) Regarding the carbon dioxide absorbent solution of Example 3, after the completion of regeneration test 1, that is, after repeating carbon dioxide absorption and regeneration seven times, ３１ P-NMR analysis was performed. The results showed that tris(3-aminopropyl)phosphine oxide accounted for 19.9%, (bis(3-aminopropyl))(3-aminopropyloxy)phosphine oxide for 6.5%, and tris(3-aminopropyl)phosphine for 73.6%. It was confirmed that even in the carbon dioxide absorption solution after multiple cycles of carbon dioxide absorption and regeneration, more than 70% of tris(3-aminopropyl)phosphine remained.

Claims

1. The following general formula (1): (In the formula, a, b, and c represent integers between 1 and 10, and R １ , R ２ and R ３ An antioxidant characterized by being a phosphine compound represented by (where each independently represents an amino group or a hydroxyl group).

2. A material comprising a carbon dioxide absorbing material, an antioxidant, and a solvent, wherein the antioxidant is of the following general formula (1): (In the formula, a, b, and c represent integers between 1 and 10, and R １ , R ２ and R ３ A carbon dioxide absorbent characterized by being a phosphine compound represented by (where each independently represents an amino group or a hydroxyl group).

3. In the formula of the general formula (1), R １ , R ２ and R ３ are all amino groups or hydroxy groups, and the carbon dioxide absorption liquid according to claim 2 is characterized thereby.

4. The carbon dioxide absorbing liquid according to claim 2 or 3, characterized in that the carbon dioxide absorbing material is a compound having an amino group.

5. The carbon dioxide absorbent liquid according to claim 2 or 3, characterized in that the solvent comprises at least one selected from the group consisting of water, glycol-based solvents, and alcohol-based solvents.

6. The carbon dioxide absorbent liquid according to claim 2 or 3, characterized in that the content of the carbon dioxide absorbent material in the carbon dioxide absorbent liquid is 5% by mass or more and 60% by mass or less, and the content of the antioxidant in the carbon dioxide absorbent liquid is 1% by mass or more and 30% by mass or less.

7. A method for separating carbon dioxide, characterized by comprising a carbon dioxide separation step of contacting a mixed gas containing carbon dioxide with a carbon dioxide absorbing liquid according to claim 2 or 3, thereby allowing the carbon dioxide absorbing liquid to absorb the carbon dioxide in the mixed gas and separating the carbon dioxide from the mixed gas.

8. A method for separating and recovering carbon dioxide, comprising: a carbon dioxide separation step of contacting a carbon dioxide absorption liquid according to claim 2 or 3 with a mixed gas containing carbon dioxide, thereby separating carbon dioxide from the mixed gas by allowing the carbon dioxide absorption liquid to absorb the carbon dioxide in the mixed gas; and a carbon dioxide recovery step of heating the carbon dioxide absorption liquid that has absorbed carbon dioxide in the carbon dioxide separation step at a temperature of 50°C to 150°C to desorb carbon dioxide from the carbon dioxide absorption liquid, thereby regenerating the carbon dioxide absorption liquid and recovering the desorbed carbon dioxide.

9. The carbon dioxide separation and recovery method according to claim 8, characterized in that the recycled carbon dioxide absorbent obtained by the carbon dioxide recovery step is used as the carbon dioxide absorbent to which the mixed gas containing carbon dioxide is brought into contact in the carbon dioxide separation step, thereby repeating the carbon dioxide separation step and the carbon dioxide recovery step two or more times.

10. An apparatus characterized in that it uses the carbon dioxide absorption liquid described in claim 2 or 3.

11. The apparatus according to claim 10, characterized in that the apparatus is used in a power plant, factory, or transportation equipment.

12. The apparatus according to claim 10, characterized in that the apparatus is a DAC apparatus.

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