Carbon dioxide absorbent and method for separation and recovery of carbon dioxide

Abstract

To provide a carbon dioxide absorbing composition that is capable of reducing the energy for releasing carbon dioxide and maintaining the carbon dioxide absorption capacity over an extended period.SOLUTION: A carbon dioxide absorbing composition comprises an amine compound (A) and a polyalkylene glycol (B) having a number average molecular weight of 140 or more, wherein the carbon dioxide absorbing composition contains a low molecular weight glycol compound (C) having a number average molecular weight of less than 140 in an amount of 0 to 10 wt.% based on the weight of the polyalkylene glycol (B), and the content of the polyalkylene glycol (B) is 50 wt.% or more and 80 wt.% or less based on the total weight of the amine compound (A), the polyalkylene glycol (B), and the low molecular weight glycol compound (C).SELECTED DRAWING: None

Description

[Technical field]

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

[0002] As a technology that can save energy in the carbon dioxide recovery process, a carbon dioxide absorbing solution in which an amine is diluted with an organic solvent that has a lower latent heat and specific heat than water is being considered. For example, Patent Document 1 proposes a composition for separating and absorbing carbon dioxide, which contains an amine component containing a specific cyclic amine compound and an organic solvent such as polyethylene glycol. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2023-124995 A Summary of the Invention [Problem to be solved by the invention]

[0004] In a typical carbon dioxide capture process, a carbon dioxide absorption step in which carbon dioxide is separated from a gas containing carbon dioxide and absorbed in a carbon dioxide absorbing liquid and a carbon dioxide dissipation step in which carbon dioxide is dissipated from a composition that has absorbed carbon dioxide are repeatedly performed. The composition described in Patent Document 1 above makes it possible to save energy when dissipating carbon dioxide. However, there is a problem in that it is difficult to maintain the amount of carbon dioxide absorbed when the carbon dioxide capture process is carried out for a long period of time. An object of the present invention is to provide a composition for absorbing carbon dioxide, which can reduce the energy required for dissipating carbon dioxide and can maintain the amount of carbon dioxide absorbed for a long period of time. [Means for solving the problem]

[0005] The carbon dioxide absorption composition contains water [specific heat: 4.2 kJ / kg°C, vapor pressure (100°C): 3.2×10 3 It was found that by using a material with a specific heat and vapor pressure smaller than [1000 MPa (Pa)], it is possible to reduce energy consumption in the carbon dioxide separation and capture process. Based on this finding, a carbon dioxide absorption composition using an amine compound and a polyalkylene glycol having a lower specific heat and vapor pressure than water was studied, and there was a problem that it was difficult to maintain the carbon dioxide absorption amount when the carbon dioxide recovery process was performed for a long period of time (for example, 10 days or more). One of the reasons why it is difficult to maintain the carbon dioxide absorption amount over a long period of time is that the low molecular weight glycol component that the polyalkylene glycol may contain in its manufacturing process is oxidized in the process of repeating the carbon dioxide recovery process to produce acidic oxides, aldehyde compounds, etc., which react with the amine compound in the composition. Therefore, a composition in which the low molecular weight glycol component is set to a predetermined amount or less was studied, and it was found that it is possible to maintain the carbon dioxide absorption amount over a long period of time. The present invention is based on the above novel finding.

[0006] That is, the present invention is as follows. [1] A composition for absorbing carbon dioxide containing an amine compound (A) and a polyalkylene glycol (B) having a number average molecular weight of 140 or more, the composition for absorbing carbon dioxide containing 0 to 10% by weight of a low molecular weight glycol compound (C) having a number average molecular weight of less than 140 based on the weight of the polyalkylene glycol (B), and the content of the polyalkylene glycol (B) based on the total weight of the amine compound (A), the polyalkylene glycol (B) and the low molecular weight glycol compound (C) is 50% by weight or more and 80% by weight or less. [2] The carbon dioxide absorption composition according to [1], wherein the polyalkylene glycol (B) is at least one selected from the group consisting of polyoxyethylene glycol, polyoxypropylene glycol, and polyoxyethylene polyoxypropylene glycol. [3] The carbon dioxide absorption composition according to [1] or [2], wherein the low molecular weight glycol compound (C) is at least one selected from the group consisting of ethylene glycol, diethylene glycol, propylene glycol, and dipropylene glycol. [4] The composition for absorbing carbon dioxide according to any one of [1] to [3], wherein the polyalkylene glycol (B) has a number average molecular weight of 190 to 420. [5] The composition for absorbing carbon dioxide according to any one of [1] to [4], wherein the amine compound (A) is a diamine having a ring structure. [6] A method for separating and recovering carbon dioxide using the carbon dioxide absorbing composition according to any one of [1] to [5], comprising: step 1 of contacting a gas containing carbon dioxide with the carbon dioxide absorbing composition to obtain a composition that has absorbed the carbon dioxide in the gas; and step 2 of recovering carbon dioxide from the composition that has absorbed the carbon dioxide obtained in step 1. Effect of the Invention

[0007] According to the present invention, it is possible to provide a composition for absorbing carbon dioxide that can reduce the energy required for dissipating carbon dioxide and maintain the amount of carbon dioxide absorbed for a long period of time. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] <Carbon dioxide absorption composition> The carbon dioxide absorbing composition of the present invention is a composition for absorbing carbon dioxide containing an amine compound (A) and a polyalkylene glycol (B) having a number average molecular weight of 140 or more. In the present invention, the carbon dioxide absorbing composition contains 0 to 10% by weight of a low molecular weight glycol compound (C) having a number average molecular weight of less than 140 based on the weight of the polyalkylene glycol (B). In addition, the content of the polyalkylene glycol (B) based on the total weight of the amine compound (A), the polyalkylene glycol (B) and the low molecular weight glycol compound (C) is 50% by weight or more and 80% by weight or less. In the present invention, by having the content of polyalkylene glycol (B) within the above range and the content of low molecular weight glycol compound (C) within the above range, it is possible to keep the energy required for dissipating carbon dioxide low and to maintain the amount of carbon dioxide absorbed over a long period of time.

[0009] The amine compound (A) contained in the composition of the present invention includes monoamines and polyamines, etc. Examples of monoamines include primary amines such as monoethanolamine, secondary amines such as diethanolamine, dipropanolamine, dibutanolamine, N-methylethanolamine, N-ethylethanolamine, 3-methylamino-1-propanol, N-butylethanolamine, and N-propylethanolamine, and tertiary amines such as N-methyldiethanolamine (methyldiethanolamine), N-ethyldiethanolamine, and N-butyldiethanolamine. Examples of polyvalent amines include diamines having a ring structure such as hydroxymethyltriethylenediamine, isophoronediamine, and metaxylenediamine, polyethylene polyamines represented by the following general formula (1), linear or branched polyethyleneimines [for example, "Epomin (registered trademark)" manufactured by Nippon Shokubai Co., Ltd.], etc. The amine compound (A) may be used alone or in combination of two or more kinds.

[0010] [ka]

[0011] In the general formula (1), n ​​is an integer from 1 to 10, and R 1 ~R 3 each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. The alkyl group having 1 to 6 carbon atoms may be linear or branched.

[0012] A specific example of the compound is triethylenetetramine (n=3 in general formula (1), R 1 ~R 3are all hydrogen atoms), tetraethylenepentamine (n=4 in general formula (1), R 1 ~R 3 are all hydrogen atoms), pentaethylenehexamine (n=5 in general formula (1), R 1 ~R 3 are all hydrogen atoms), hexaethyleneheptamine (n=6 in general formula (1), R 1 ~R 3 In the general formula (1), R 1 ~R 3 Each of the groups is preferably a hydrogen atom.

[0013] As the amine compound (A), from the viewpoint of being able to maintain the amount of carbon dioxide absorption when the carbon dioxide recovery process is carried out over a long period of time, diamines having a ring structure are preferred, and hydroxymethyltriethylenediamine, isophoronediamine and metaxylenediamine are more preferred.

[0014] Polyalkylene glycols (B) with a number average molecular weight (Mn) of 140 or more include water [specific heat: 4.2 kJ / kg°C, vapor pressure (100°C): 3.2×10 3There are no particular limitations on the specific heat and vapor pressure as long as they are smaller than those of the specific heat and vapor pressure of the polyoxyethylene glycol (PEG) [specifically, "PEG-200" manufactured by Sanyo Chemical Industries, Ltd. (specific heat: 2.2 kJ / kg·K, vapor pressure (100°C): 1.3 Pa), "tetraethylene glycol" manufactured by Tokyo Chemical Industry Co., Ltd. (Mn: 194.2, specific heat: 2.2 kJ / kg·K, vapor pressure (100°C): 1.3 Pa), "PEG-300" manufactured by Sanyo Chemical Industries, Ltd. (specific heat: 2.2 kJ / kg·K, vapor pressure (100°C): 0.39 Pa), "nonaethylene glycol" manufactured by Tokyo Chemical Industry Co., Ltd. Examples of the polyoxyethylene glycol include polyoxyethylene glycol (PPG) ["Tripropylene glycol" (Mn: 192.26, specific heat 2.0 kJ / kg·K, vapor pressure (25°C) 140 Pa) manufactured by Tokyo Chemical Industry Co., Ltd., and polyoxyethylene polyoxypropylene glycol. Among these, polyoxyethylene glycol, polyoxypropylene glycol, polyoxyethylene polyoxypropylene glycol, and combinations thereof are preferred from the viewpoint of keeping the energy required for dissipating carbon dioxide low. The polyalkylene glycol (B) may be used alone or in combination of two or more kinds.

[0015] From the viewpoint of increasing the fluidity of the carbon dioxide absorbent and reducing the energy required for liquid transport during the carbon dioxide separation process, the polyalkylene glycol (B) preferably has a number average molecular weight of 190 to 420, and more preferably has a number average molecular weight of 200 to 400.

[0016] As the polyalkylene glycol (B), from the viewpoint of reducing the amount of low molecular weight glycol components that may be contained during the production process, it is preferable to use one produced from a dialkylene glycol (diethylene glycol, dipropylene glycol) as a raw material.

[0017] A low molecular weight glycol compound (C) having a number average molecular weight of less than 140 is a component that is preferably not contained in the composition of the present invention. However, when the composition of the present invention contains such a component, examples of (C) include ethylene glycol (EG), diethylene glycol (DEG), propylene glycol (PG), butylene glycol, and dipropylene glycol (DPG). Among these, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, and combinations thereof are preferred from the viewpoint of maintaining the amount of carbon dioxide absorption when the carbon dioxide recovery process is carried out over a long period of time. The low molecular weight glycol compound (C) may be contained in the composition alone or in two or more types.

[0018] The content of the amine compound (A) based on the total weight of the amine compound (A), the polyalkylene glycol (B) and the low-molecular-weight glycol compound (C) is preferably 20 to 40% by weight, and more preferably 30 to 40% by weight, from the viewpoint of increasing the amount of carbon dioxide absorption per unit amount of the carbon dioxide absorbent.

[0019] The content of the polyalkylene glycol (B) based on the total weight of the amine compound (A), the polyalkylene glycol (B) and the low molecular weight glycol compound (C) is preferably 52 to 79.8% by weight, from the viewpoint of keeping the energy required for dissipating carbon dioxide low and maintaining the amount of carbon dioxide absorption for a long period of time.

[0020] The content of the low molecular weight glycol compound (C) based on the total weight of the amine compound (A), the polyalkylene glycol (B) and the low molecular weight glycol compound (C) is preferably 0 to 7% by weight from the viewpoint of being able to maintain the carbon dioxide absorption amount for a long period of time.

[0021] The proportion of the low molecular weight glycol compound (C) based on the weight of the polyalkylene glycol (B) is preferably 0 to 9.6% by weight, from the viewpoint of being able to maintain the amount of carbon dioxide absorption for a long period of time.

[0022] The composition of the present invention may contain other components (E) other than the amine compound (A), the polyalkylene glycol (B), and the low molecular weight glycol compound (C). The other components (E) include protic solvents and / or aprotic solvents. Examples of protic solvents include water, methanol, ethanol, 1-propanol, and polyethylene glycol. Examples of aprotic solvents include amides such as N-methylpyrrolidone, sulfones such as sulfolane, carbonates such as propylene carbonate, esters such as γ-butyrolactone, nitriles such as acetonitrile, and ethers such as diglyme, triglyme, and polyethylene glycol dimethyl ether.

[0023] When a tertiary amine is used as the amine compound (A), it is preferable to use water as the other component (E). In this case, the amount of water used is preferably an amount such that the weight ratio (weight of water:weight of (A)) to the weight of the amine compound (A) is 1:1 to 1:4.

[0024] The carbon dioxide absorbing composition of the present invention can be produced by a known method, such as a method of mixing the amine compound (A), the polyalkylene glycol (B), the low molecular weight diol (C), and optional components [surfactant (D) and other components (E)] by a conventional method.

[0025] The carbon dioxide absorbing composition of the present invention can be used in a method for separating and recovering carbon dioxide. Carbon dioxide separation and recovery can be performed by repeatedly separating carbon dioxide from a gas containing carbon dioxide, absorbing it into the carbon dioxide absorbing composition, and releasing and recovering the carbon dioxide from the composition that has absorbed the carbon dioxide.

[0026] According to the carbon dioxide absorbing composition of the present invention, the polyalkylene glycol, which has a lower specific heat and vapor pressure than water, is contained in an amount of 50 to 80% by weight based on the total weight of the amine compound (A), the polyalkylene glycol (B) and the low molecular weight glycol compound (C), so that it is possible to reduce the energy required to dissipate carbon dioxide from the composition that has absorbed carbon dioxide. In addition, according to the carbon dioxide absorbing composition of the present invention, the content of the low molecular weight glycol compound (B) is set to 10% by weight or less based on the weight of the polyalkylene glycol (B), so that it is possible to reduce the amount of acidic oxides and aldehyde compounds generated due to the repetition of the carbon dioxide separation and recovery process, and to suppress a decrease in the carbon dioxide absorption capacity of the carbon dioxide absorbing composition. As a result, according to the present invention, it is possible to provide a carbon dioxide absorbing composition that can reduce the energy required for dissipating carbon dioxide and maintain the amount of carbon dioxide absorbed over a long period of time.

[0027] <Method of carbon dioxide separation and capture> The method for separating and recovering carbon dioxide of the present invention is a method for separating and recovering carbon dioxide using the carbon dioxide absorption composition of the present invention, and includes step 1 of contacting a gas containing carbon dioxide with the carbon dioxide absorption composition to obtain a composition that has absorbed the carbon dioxide in the gas, and step 2 of recovering carbon dioxide from the composition that has absorbed carbon dioxide obtained in step 1.

[0028] Step 1 is a step of contacting a gas containing carbon dioxide with the carbon dioxide absorbing composition of the present invention to obtain a composition that absorbs carbon dioxide in the gas. There is no particular limitation on the method of contacting a gas containing carbon dioxide with the carbon dioxide absorbing composition, and a known method can be used. Known methods include a countercurrent contact method and a bubbling method.

[0029] In step 1, the temperature at which the gas containing carbon dioxide is brought into contact with the carbon dioxide absorbing composition of the present invention for absorption is not particularly limited, and can be, for example, 0°C to 60°C.

[0030] Step 2 is a step of recovering carbon dioxide from the composition that has absorbed carbon dioxide obtained in step 1. In step 2, carbon dioxide is released from the composition that has absorbed carbon dioxide, and the released carbon dioxide is collected. The temperature at which carbon dioxide is released from the composition that has absorbed carbon dioxide is not particularly limited, but is preferably 50 to 150°C, and from the viewpoint of keeping energy low, is preferably 50 to 100°C.

[0031] Step 1 and step 2 may be performed only once or may be performed repeatedly two or more times. In addition to step 1 and step 2, other steps (such as a step of heating the composition that has absorbed carbon dioxide) may be performed.

[0032] The carbon dioxide absorption composition of the present invention may be used as a solid adsorbent for absorbing carbon dioxide by supporting or attaching the composition to any carrier, and may adsorb carbon dioxide in a gas containing carbon dioxide. The carrier is not particularly limited, but may be porous particles such as zeolite, activated carbon, and porous silica, fine particle aggregates such as bricks and concrete, foams such as pumice and urethane foam, and fiber aggregates such as paper, woven fabric, and nonwoven fabric. EXAMPLES

[0033] The present invention will be further described below with reference to examples, but the present invention is not limited thereto. In the following, % means % by weight, and parts means parts by weight, unless otherwise specified.

[0034] <Examples and Comparative Examples> (Examples 1 to 10, 13 to 14, Comparative Examples 1 to 2) The types of amines (A), polyalkylene glycols (B) and low molecular weight glycols (C) shown in Table 1 were mixed in the amounts shown in Table 1 and stirred for 30 minutes to obtain carbon dioxide absorbing compositions of Examples 1 to 10 and Comparative Examples 1 and 2. 10 g of the obtained carbon dioxide absorbing compositions were subjected to measurement of the carbon dioxide absorption amount immediately after the preparation of the composition (initial stage), and the remaining carbon dioxide absorbing compositions were subjected to measurement of the carbon dioxide absorption amount after long-term exposure to a high-temperature environment. The polyalkylene glycols (B) used in the examples are as follows: PEG (Mn: 194.23): Tokyo Chemical Industry Co., Ltd., "Tetraethylene glycol", specific heat 2.2 kJ / kg·K, vapor pressure (100°C) 1.3 Pa PEG (Mn: 414.49): Tokyo Chemical Industry Co., Ltd., "Nonaethylene glycol", specific heat 2.2 kJ / kg·K, vapor pressure (100°C) 0.012 Pa PPG (Mn: 192.26): Tokyo Chemical Industry Co., Ltd., "Tripropylene glycol", specific heat 2.0 kJ / kg·K, vapor pressure (25°C) 140 Pa

[0035] (Examples 11 to 12) The types of amines (A), polyalkylene glycol (B), low molecular weight glycol (C) and water shown in Table 1 were mixed in the amounts shown in Table 1 and stirred for 30 minutes to obtain carbon dioxide absorbing compositions of Examples 11 and 12. 10 g of the obtained carbon dioxide absorbing compositions were subjected to measurement of the carbon dioxide absorption amount immediately after preparation of the composition (initial stage), and the remaining carbon dioxide absorbing compositions were subjected to measurement of the carbon dioxide absorption amount after long-term exposure to a high-temperature environment.

[0036] <Evaluation test> (A) Measurement of initial carbon dioxide absorption amount X0 per 1 g of carbon dioxide absorption composition For the carbon dioxide absorbing compositions prepared in Examples 1 to 14 and Comparative Examples 1 and 2, the initial carbon dioxide absorption amount at 40° C. per 1 g of the carbon dioxide absorbing composition was measured by the following procedure. (1) A 50 mL two-necked recovery flask was fitted with a rubber stopper and its weight was measured (this weight was recorded as the "empty flask (air)"). (2) The air in the 50 mL two-necked flask was replaced with carbon dioxide, and the weight was measured again (this weight was recorded as the "empty flask (carbon dioxide)"). (3) After replacing the air inside a 50 mL two-necked recovery flask, 10 g of the carbon dioxide absorption composition immediately after preparation was placed in the flask and the weight was measured (this weight was designated as "t = 0 (air)"). (4) t = 0 (air) + [empty flask (carbon dioxide) - empty flask (air)] was calculated, and this was used as the weight of the two-necked recovery flask containing 10 g of the carbon dioxide absorption composition under a carbon dioxide atmosphere (this weight was used as "t = 0 (carbon dioxide)"). (5) Carbon dioxide was taken from a carbon dioxide cylinder [carbon dioxide gas manufactured by Iwatani Corporation] into a gas collection balloon, which was then attached to a 50 mL two-necked eggplant flask to replace the carbon dioxide. The temperature was then adjusted to 40°C under atmospheric pressure. (6) After shaking the flask for 3 minutes, the weight of the two-necked flask was measured. This procedure was repeated until the weight change was 10 mg or less (measured every 3 minutes). (7) The difference between t=0 (carbon dioxide) and the final weight of (6) was defined as the amount of carbon dioxide absorbed per 10 g of the carbon dioxide absorbing composition. (8) Finally, the amount of carbon dioxide absorbed (mg) in (7) was converted per gram of the carbon dioxide absorbing composition.

[0037] (B) Measurement of carbon dioxide absorption amount X1 per 1 g of carbon dioxide absorption composition after long-term exposure to a high-temperature environment Air was blown into the carbon dioxide absorption compositions prepared in Examples 1 to 14 and Comparative Examples 1 and 2 at 100° C. for 720 hours to prepare samples S1 for measuring the amount of carbon dioxide absorbed. (A) In the method for measuring the initial carbon dioxide absorption amount X0 per 1 g of the carbon dioxide absorption composition in (3), except that "10 g of the carbon dioxide absorption measurement sample S1" was used instead of "10 g of the carbon dioxide absorption composition immediately after preparation", the same procedure as in (A) was performed, and the carbon dioxide absorption amount X1 per 1 g of the carbon dioxide absorption composition after long-term exposure to a high-temperature environment was measured.

[0038] (C) Calculation of carbon dioxide (CO2) absorption capacity maintenance rate The carbon dioxide absorption capacity retention rate after long-term exposure to a high-temperature environment was calculated from the following formula (2) using the "initial carbon dioxide absorption amount X0 per 1 g of the carbon dioxide absorption composition" measured in (A) and the "carbon dioxide absorption amount X1 per 1 g of the carbon dioxide absorption composition after long-term exposure to a high-temperature environment" measured in (B). The results are shown in Table 1. CO2 absorption capacity maintenance rate (%) = 100 × (X1 / X0) (2)

[0039] [Table 1]

[0040] As shown in Table 1, the compositions of the examples, which contain an amine compound (A) and a polyalkylene glycol (B), in which the proportion of the low molecular weight glycol compound (C) based on the weight of (B) is 10% by weight or less, and the content of the polyalkylene glycol (B) based on the total weight of (A), (B) and (C) is 50% by weight or more and 80% by weight or less, had a significantly higher CO2 absorption capacity maintenance rate than the compositions of the comparative examples. From this result, it can be seen that the carbon dioxide absorption amount can be maintained for a long period of time according to the present invention. Furthermore, the composition of the embodiment contains 50 to 80% by weight of polyalkylene glycol (B) having a low specific heat and vapor pressure, based on the total weight of the amine compound (A), polyalkylene glycol (B) and low molecular weight glycol compound (C), so it is possible to keep the energy required to dissipate carbon dioxide from the composition that has absorbed carbon dioxide low. From the above, it is seen that the present invention can provide a carbon dioxide absorbing composition that can reduce the energy required for dissipating carbon dioxide and maintain the amount of carbon dioxide absorbed over a long period of time.

Claims

1. A carbon dioxide absorption composition comprising an amine compound (A) and a polyalkylene glycol (B) having a number average molecular weight of 140 or more, The carbon dioxide absorption composition contains 0 to 10% by weight of a low molecular weight glycol compound (C) having a number average molecular weight of less than 140 based on the weight of the polyalkylene glycol (B), A composition for absorbing carbon dioxide, wherein the content of the polyalkylene glycol (B) based on the total weight of the amine compound (A), the polyalkylene glycol (B) and the low molecular weight glycol compound (C) is 50% by weight or more and 80% by weight or less.

2. 2. The carbon dioxide absorption composition according to claim 1, wherein the polyalkylene glycol (B) is at least one selected from the group consisting of polyoxyethylene glycol, polyoxypropylene glycol, and polyoxyethylene polyoxypropylene glycol.

3. 3. The carbon dioxide absorption composition according to claim 1, wherein the low molecular weight glycol compound (C) is at least one selected from the group consisting of ethylene glycol, diethylene glycol, propylene glycol, and dipropylene glycol.

4. The carbon dioxide absorbing composition according to claim 1 or 2, wherein the polyalkylene glycol (B) has a number average molecular weight of 190 to 420.

5. The carbon dioxide absorption composition according to claim 1 or 2, wherein the amine compound (A) is a diamine having a ring structure.

6. A method for separating and recovering carbon dioxide using the carbon dioxide absorption composition according to claim 1 or 2, A step 1 of contacting a gas containing carbon dioxide with the carbon dioxide absorbing composition to obtain a composition that has absorbed carbon dioxide in the gas; A method for separating and recovering carbon dioxide, comprising: a step 2 of recovering carbon dioxide from the composition having absorbed carbon dioxide obtained in the step 1.

Images