An absorbent and its use in carbon dioxide capture

Abstract

The application discloses an absorbent and application thereof in carbon dioxide capture, and belongs to the technical field of carbon dioxide emission reduction. The absorbent provided by the application comprises an alcohol ether compound; the chemical formula of the alcohol ether compound is shown as formula (I); in formula (I), n>2; R1 is C1-C 10 alkylene; R2 and R3 are each independently H or C1-C 10 alkyl. The alcohol ether compound has suitable polarity, volatility and viscosity by adjusting the ether group, hydroxyl group and alkyl structure of the alcohol ether compound, the alcohol ether compound is used as a component of the absorbent, the physical and chemical properties of the absorbent are optimized, the absorbent has the advantages of low viscosity, low volatility, low cost and high safety, and therefore has good application effect in carbon dioxide capture.

Description

Technical Field

[0001] This invention belongs to the field of carbon dioxide emission reduction technology, and particularly relates to an absorbent and its application in carbon dioxide capture. Background Technology

[0002] Carbon dioxide emission reduction from low-CO2 flue gas produced by coal-fired power plants, steel mills, and cement plants can be achieved through post-combustion chemical absorption. Carbon capture using organic amines as absorbents is currently the most mature and commercially widely applied technology. Ethanolamine (MEA) was the earliest commercially available carbon capture absorbent, offering advantages such as high absorption efficiency and low cost, but it also suffers from high energy consumption, easy degradation, and high corrosiveness. Developing novel absorbents with high and stable absorption performance and low operating costs is crucial for the application of carbon capture technology.

[0003] In recent years, numerous researchers have proposed various types of novel absorbents, including mixed amine absorbents, two-phase absorbents, and low-aqueous absorbents, to reduce energy consumption and operating costs in carbon capture. Two-phase absorbents are mainly composed of organic amines, a phase-separating agent, and water. The phase-separating agent is typically a tertiary amine or an organic solvent. After absorbing CO2, the two-phase absorbent forms two immiscible phases: a lean phase (low CO2 content) and a rich phase (high CO2 content). The lean phase, after separation, is recycled back to the absorption tower to capture CO2, while the rich phase is recycled to the desorption tower for desorption. This process improves the efficiency of both absorption and desorption processes while effectively reducing the consumption of sensible heat and latent heat of vaporization during regeneration, thereby lowering energy costs. Low-aqueous absorbents are composed of organic amines, a non-aqueous solvent, and water. The non-aqueous solvent used is an organic solvent, which has a lower specific heat capacity than water. Therefore, low-aqueous absorbents have greater potential for lower energy consumption than conventional mixed amine absorbents.

[0004] Organic solvents are an important component in two-phase absorbents and low-water absorbents. Existing patents disclose organic solvents mainly including n-propanol, n-butanol, sulfolane, dimethyl sulfoxide, N-methylpyrrolidone, and polyethylene glycol dimethyl ether, for example:

[0005] A study has published a two-phase absorbent composed of N-aminoethylpiperazine, n-propanol, and water. N-aminoethylpiperazine serves as the main absorbent, n-propanol as the phase separator, and water as the solvent. The two-phase structure reduces regeneration energy consumption, but it suffers from the high volatility of n-propanol and the high viscosity of the rich solution after phase separation.

[0006] Another study disclosed a liquid for carbon dioxide capture. Liquid phase change absorbents are composed of primary amines, secondary amines, organic solvents, and water. Primary amines refer to monoethanolamine (MEA), and secondary amines refer to... Ethylaminoethanol (EAE), an organic solvent, refers to sulfolane. This absorbent has good phase separation characteristics and low energy consumption, but the secondary amine has relatively poor resistance to degradation.

[0007] Another study discloses an organic amine low-water absorbent for carbon dioxide capture, consisting of 30-55% diamine, 40-67% organic solvent, and 2-15% water, as well as other additives. The organic solvent is N-methylpyrrolidone. The low water content in this absorbent can effectively reduce the latent heat and sensible heat of the solution.

[0008] Another study discloses an organic amine absorbent for capturing carbon dioxide, which is prepared by uniformly mixing 10-60% main absorbent, 0-10% co-absorbent, 10-80% organic solvent, 5-70% water, 0.01-5% antioxidant, and 0.01-5% corrosion inhibitor by mass percentage. The organic solvent is one or a mixture of several of dimethyl sulfoxide, N,N-dimethylformamide, 1,3-dimethyl-2-imidazolinone, hexamethylphosphoric triamine, N,N-dimethylacetamide, and N-methylpyrrolidone.

[0009] Another study disclosed a low-corrosion phase change absorbent, which consists of 10-30% main absorbent, 1-10% activator, 30-60% phase separator, and the balance being water, wherein the phase separator is polyethylene glycol dimethyl ether.

[0010] In the above studies, the application of organic solvents in absorbents is prone to problems such as excessively high viscosity of the absorbent rich solution, large evaporation and escape of organic solvents, difficulty in controlling phase separation behavior, and high cost, which are not conducive to the long-term stable application of absorbents. Summary of the Invention

[0011] In order to overcome at least one of the problems existing in the prior art, one of the objectives of the present invention is to provide an absorbent that can effectively solve the problems of phase separation difficulty, high viscosity, high volatility and high cost that are easily caused by absorbents during application.

[0012] The second objective of this invention is to provide a method for capturing carbon dioxide.

[0013] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0014] A first aspect of the present invention provides an absorbent comprising an alcohol ether compound; the chemical formula of the alcohol ether compound is shown in formula (I):

[0015] Formula (I);

[0016] In equation (I), n > 2; R1 is C1 ~ C 10Alkylene; R2 and R3 are each independently H or C1~C 10 alkyl.

[0017] Diols contain two hydroxyl groups. The dehydration and etherification of the hydroxyl groups of two diol molecules can form a straight-chain alcohol ether. This alcohol ether compound has a hydroxyl group at each end, which can further dehydrate and etherify with the hydroxyl groups, thus forming alcohol ether compounds with different structures. Taking ethylene glycol as an example, the dehydration and etherification of the hydroxyl groups of two ethylene glycol molecules can form a straight-chain diethylene glycol, also called diethylene glycol or diethylene glycol ether. Diethylene glycol has two hydroxyl groups on both sides, which can dehydrate and etherify with the hydroxyl groups of methanol, ethanol, butanol, etc., thus forming diethylene glycol dimethyl ether, diethylene glycol diethyl ether, etc. In turn, multiple ethylene glycols can form straight-chain polyethylene glycols, and further form compounds such as polyethylene glycol dimethyl ether and polyethylene glycol diethyl ether. Common solvents such as polyethylene glycol dimethyl ether (NHD) are derived in this way.

[0018] Therefore, there are many types of alcohol ether compounds, but the main factors affecting their physicochemical properties as solvents are: ether group, hydroxyl group, alkyl group, and long chain molecular weight. These factors jointly affect their water solubility (e.g., the more hydroxyl and ether groups there are, the stronger the hydrogen bonding with water, and the better the water solubility), volatility (e.g., the larger the long chain molecular weight, the higher the boiling point and the lower the volatility), and viscosity (e.g., the larger the long chain molecular weight, the higher the viscosity). This invention, by designing alcohol ether compounds with suitable structures, helps the absorbent maintain appropriate polarity, volatility, and viscosity, thereby effectively improving the performance of the absorbent. In addition, alcohol ether compounds also have advantages such as low toxicity, low corrosivity, and low cost.

[0019] Preferably, in formula (I), 3 ≤ n ≤ 7; for example, n can be any one of 3, 4, 5, 6 or 7 or a range between any two, such as 3 to 5. In some embodiments of the present invention, n is selected from 3 or 4.

[0020] This invention has a specific value for n, which is beneficial for controlling the compound to have a suitable chain length and molecular weight, thereby enabling the absorbent to have suitable polarity, volatility and viscosity.

[0021] In some embodiments of the present invention, n is an integer.

[0022] Preferably, in formula (I), R1 is a C1-C4 alkylene group; for example, R1 can be any one of methylene, ethylene, propylene, or butylene. In some embodiments of the present invention, R1 is selected from ethylene.

[0023] In some embodiments of the present invention, the absorbent is a two-phase absorbent or a single-phase absorbent.

[0024] For two-phase absorbents, alcohol ether compounds mainly serve as phase-separating agents. In this case, they need to remain in a single phase and be miscible with aqueous solution when the absorbent has not absorbed CO2. However, after the absorbent absorbs a certain amount of CO2, they become immiscible with aqueous solution and form a phase separation. Therefore, the polarity of the selected alcohol ether compound must be moderate to avoid either no phase separation or excessively rapid phase separation. In addition, the balance between the volatility and viscosity of the alcohol ether compound must also be considered.

[0025] Preferably, in formula (I), R2 and R3 are each independently selected from C1 to C2. 10 Alkyl group, or R2 selected from C1~C2. 10 Alkyl groups and R3 are selected from H.

[0026] By designing R2 and R3, the number of hydroxyl groups in the alcohol ether compound can be either 0 or 1. Adjusting the number of hydroxyl groups helps to give the alcohol ether compound moderate polarity, thus avoiding either no phase separation or excessively rapid phase separation.

[0027] In some embodiments of the present invention, in formula (I), R2 and R3 are each independently selected from C1 to C2. 10 The alkyl group, and the number of carbon atoms of R2 is greater than or equal to 1 and less than or equal to n-1, and the number of carbon atoms of R3 is less than or equal to the number of carbon atoms of R2; furthermore, the number of carbon atoms of R3 is less than the number of carbon atoms of R2.

[0028] In some embodiments of the present invention, in formula (I), R2 is selected from C1 to C2. 10 The alkyl group, R3 is selected from H, and the number of carbon atoms in R2 is greater than or equal to 1 and less than or equal to n+2; further, the number of carbon atoms in R2 is greater than or equal to 1 and less than or equal to n+1.

[0029] The above structural design enables alcohol ether compounds to have moderate polarity, thus avoiding the occurrence of phase separation or excessively rapid phase separation. In addition, it achieves a balance between the volatility and viscosity of alcohol ether compounds, which is beneficial for use as two-phase absorbents and achieves good carbon dioxide capture effect.

[0030] For single-phase absorbents, alcohol ether compounds are used as adjuvants. In this case, they need to remain in a single phase both before and after the absorbent absorbs CO2. Therefore, the selected alcohol ether compounds are required to have high polarity. In addition, the balance between the volatility and viscosity of the alcohol ether compounds also needs to be considered.

[0031] Preferably, both R2 and R3 are selected from H, or R2 is selected from C1 to C2. 10 Alkyl groups and R3 are selected from H.

[0032] By designing R2 and R3, the number of hydroxyl groups in alcohol ether compounds can be either 1 or 2. Adjusting the number of hydroxyl groups can help to give alcohol ether compounds higher polarity.

[0033] In some embodiments of the present invention, in formula (I), R2 and R3 are each independently selected from C1 to C2. 10 The alkyl group, and the number of carbon atoms of R2 is greater than or equal to 1 and less than or equal to n-2, and the number of carbon atoms of R3 is greater than or equal to 1 and less than or equal to n-2; furthermore, the number of carbon atoms of R2 is selected from 1, and / or the number of carbon atoms of R3 is selected from 1.

[0034] In some embodiments of the present invention, in formula (I), R2 is selected from C1 to C2. 10 Alkyl group, R3 is selected from H, and the number of carbon atoms in R2 is greater than or equal to 1 and less than or equal to n-1; further, the number of carbon atoms in R2 is selected from 1 or 2.

[0035] The above structural design enables alcohol ether compounds to have high polarity, which is beneficial for them to remain in a single phase before and after absorbing CO2. In addition, it also achieves a balance between the volatility and viscosity of alcohol ether compounds, which is beneficial for their use as single-phase absorbents and achieves good carbon dioxide capture effect.

[0036] In some embodiments of the present invention, the alcohol ether compound includes at least one of triethylene glycol dimethyl ether, triethylene glycol monobutyl ether, tetraethylene glycol dimethyl ether, triethylene glycol monomethyl ether, or tetraethylene glycol monomethyl ether.

[0037] It is understood that the specific alcohol ether compounds mentioned above are merely examples, and the present invention is not limited to the specific alcohol ether compounds mentioned above. Those skilled in the art can freely design based on the content described in the present invention.

[0038] Preferably, the alcohol ether compound in the absorbent has a mass percentage of 25-60%; more preferably 30-55%; and even more preferably 40-48%.

[0039] Preferably, the absorbent further comprises organic amines and water.

[0040] In some embodiments of the present invention, the amino group in the organic amine includes at least one of a primary amino group, a secondary amino group, or a tertiary amino group.

[0041] In some embodiments of the present invention, the organic amine has a chain-like or cyclic structure.

[0042] In some embodiments of the present invention, the organic amines are one or more types.

[0043] Preferably, the absorbent comprises the following components in parts by weight: 25-60 parts of alcohol ether compound, 20-40 parts of organic amine and 10-40 parts of water; more preferably, the absorbent comprises the following components in parts by weight: 30-55 parts of alcohol ether compound, 22-38 parts of organic amine and 15-38 parts of water; even more preferably, the absorbent comprises the following components in parts by weight: 40-48 parts of alcohol ether compound, 25-35 parts of organic amine and 20-35 parts of water.

[0044] A second aspect of the present invention provides the application of an absorbent as described in the first aspect of the present invention in carbon dioxide capture.

[0045] A second aspect of the present invention provides a carbon dioxide capture method, comprising the following steps: using the absorbent described in the first aspect of the present invention to absorb and treat carbon dioxide-containing flue gas.

[0046] Preferably, the absorption treatment temperature is 30~50℃; more preferably 35~45℃.

[0047] Preferably, the absorption treatment time is 20-40 min; more preferably 25-35 min.

[0048] Preferably, the volume percentage of carbon dioxide in the carbon dioxide-containing flue gas is 5-20%; more preferably 8-18%; and even more preferably 10-15%.

[0049] The beneficial effects of this invention are: by regulating the ether group, hydroxyl group and alkyl group structure of alcohol ether compounds to make them have suitable polarity, volatility and viscosity, and using them as components of absorbents, the physicochemical properties of absorbents can be optimized, so that absorbents have the advantages of low viscosity, low volatility, low cost and high safety, thus having good application effect in carbon dioxide capture. Detailed Implementation

[0050] The following specific embodiments further illustrate the content of the present invention in detail. It should also be understood that the following embodiments are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Non-essential improvements and adjustments made by those skilled in the art based on the principles described herein are all within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make selections within a suitable range based on the description herein, and are not intended to be limited to the specific data in the examples below. Unless otherwise specified, the raw materials, reagents, or apparatus used in the following embodiments and comparative examples can be obtained from conventional commercial sources or by existing known methods.

[0051] Some embodiments of the present invention provide an absorbent comprising alcohol ether compounds; the chemical formula of the alcohol ether compounds is shown in formula (I):

[0052] Formula (I);

[0053] In equation (I), n > 2; R1 is C1 ~ C 10 Alkylene; R2 and R3 are each independently H or C1~C 10 alkyl.

[0054] In alcohol ether compounds, n is greater than 2 mainly because when n is 1 or 2, the boiling point of alcohol ether compounds is generally below 200℃ and the vapor pressure is relatively high, which easily leads to volatilization.

[0055] Furthermore, n does not exceed 7, mainly because when n≤7, alcohol ether compounds have lower cost and lower viscosity.

[0056] The boiling point, vapor pressure, and enthalpy of vaporization of some alcohol ether compounds are shown in Table 1.

[0057] Table 1. Boiling point, vapor pressure, and enthalpy of vaporization data for some alcohol ether compounds.

[0058]

[0059] The present invention will be further described below with reference to specific embodiments and comparative examples.

[0060] Example 1

[0061] An absorbent, by mass percentage, comprises: 30% MEA, 40% triethylene glycol dimethyl ether, and 30% water.

[0062] In the triethylene glycol dimethyl ether structure, n is 3; R1 is ethylene; R2 is methyl with 1 carbon atom; R3 is methyl with 1 carbon atom; and the number of hydroxyl groups is 0.

[0063] In this example, the absorbent, acting as a two-phase absorbent, can be used for carbon dioxide capture. Specifically, this absorbent was used to absorb simulated flue gas with a CO2 volume fraction of 12%, at an absorption temperature of 40°C and an absorption time of 30 minutes. After absorbing CO2, the absorbent undergoes phase separation, with a light phase to rich phase ratio of 40%:60%. Amine accounts for over 98% of the rich phase, and the CO2 load in the rich phase reaches 0.528 mol CO2 / mol amine. The phase separation is completed in less than 3 minutes, and the viscosity of the rich phase saturated with carbon dioxide is only 13.5 mPa·s (40°C).

[0064] Example 2

[0065] An absorbent, by mass percentage, comprises: 30% MEA, 40% triethylene glycol monobutyl ether, and 30% water.

[0066] In the triethylene glycol monobutyl ether structure, n is 3; R1 is ethylene; R2 is butyl with 4 carbon atoms; R3 is H; and the number of hydroxyl groups is 1.

[0067] In this example, the absorbent, acting as a two-phase absorbent, can be used for carbon dioxide capture. Specifically, this absorbent was used to absorb simulated flue gas with a CO2 volume fraction of 12%, at an absorption temperature of 40°C and an absorption time of 30 minutes. After absorbing CO2, the absorbent undergoes phase separation, with a light phase to rich phase ratio of 44%:56%. Amine accounts for over 97% of the rich phase, and the CO2 load in the rich phase reaches 0.533 mol CO2 / mol amine. The phase separation is completed in less than 3 minutes, and the viscosity of the rich phase saturated with carbon dioxide is only 12.3 mPa·s (40°C).

[0068] Example 3

[0069] An absorbent, by mass percentage, comprises: 30% MAE, 48% tetraethylene glycol dimethyl ether, and 22% water.

[0070] In the tetraethylene glycol dimethyl ether structure, n is 4; R1 is ethylene; R2 is methyl with 1 carbon atom; R3 is methyl with 1 carbon atom; and the number of hydroxyl groups is 0.

[0071] In this example, the absorbent, acting as a two-phase absorbent, can be used for carbon dioxide capture. Specifically, this absorbent was used to absorb simulated flue gas with a CO2 volume fraction of 12%, at an absorption temperature of 40°C and an absorption time of 30 minutes. After absorbing CO2, the absorbent undergoes phase separation, with a light phase to rich phase ratio of 42%:58%. Amine accounts for over 96% of the rich phase, and the CO2 load in the rich phase reaches 0.503 mol CO2 / mol amine. The phase separation is completed in less than 3 minutes, and the viscosity of the rich phase saturated with carbon dioxide is only 19.3 mPa·s (40°C).

[0072] Example 4

[0073] An absorbent, by mass percentage, comprises: 30% MEA, 40% triethylene glycol monomethyl ether, and 30% water.

[0074] In the triethylene glycol monomethyl ether structure, n is 3; R1 is ethylene; R2 is methyl with 1 carbon atom; R3 is H; and the number of hydroxyl groups is 1.

[0075] In this example, the absorbent, acting as a single-phase absorbent, can be used for carbon dioxide capture. Specifically, this absorbent was used to absorb simulated flue gas with a CO2 volume fraction of 12%, at an absorption temperature of 40°C and an absorption time of 30 minutes. After absorbing CO2, the absorbent remained single-phase, with the CO2-rich phase exhibiting a loading of 0.52 mol CO2 / mol amine and a viscosity of 14.2 mPa·s (40°C).

[0076] Example 5

[0077] An absorbent, by mass percentage, comprises: 30% MAE, 45% tetraethylene glycol monomethyl ether, and 25% water.

[0078] In the tetraethylene glycol monomethyl ether structure, n is 4; R1 is ethylene; R2 is methyl with 1 carbon atom; R3 is H; and the number of hydroxyl groups is 1.

[0079] In this example, the absorbent, acting as a single-phase absorbent, can be used for carbon dioxide capture. Specifically, this absorbent was used to absorb simulated flue gas with a CO2 volume fraction of 12%, at an absorption temperature of 40°C and an absorption time of 30 minutes. After absorbing CO2, the absorbent remained single-phase, with the CO2-rich phase exhibiting a loading of 0.51 mol CO2 / mol amine and a viscosity of 15.6 mPa·s (40°C).

[0080] Comparative Example 1

[0081] An absorbent, by mass percentage, is composed of: 30% MEA, 40% sulfolane, and 30% water.

[0082] In this example, the absorbent is a two-phase absorbent used for carbon dioxide capture. Specifically, this absorbent was used to absorb simulated flue gas with a CO2 volume fraction of 12%, at an absorption temperature of 40°C, for 30 minutes. After absorbing CO2, the absorbent undergoes phase separation, with a light phase to rich phase ratio of 40%:60%. Amine accounts for over 95% of the rich phase, and the CO2 load in the rich phase reaches 0.51 mol CO2 / mol amine. The phase separation is completed in 5 minutes, and the viscosity of the rich phase saturated with carbon dioxide is 22.5 mPa·s (40°C).

[0083] Comparative Example 2

[0084] An absorbent, by mass percentage, is composed of: 30% MAE, 40% n-butanol, and 30% water.

[0085] In this example, the absorbent is a two-phase absorbent used for carbon dioxide capture. Specifically, this absorbent was used to absorb simulated flue gas with a CO2 volume fraction of 12%, at an absorption temperature of 40°C, for a time of 30 minutes. After absorbing CO2, the absorbent undergoes phase separation, with a light phase to rich phase ratio of 46%:54%. Amine accounts for over 90% of the rich phase, and the CO2 load in the rich phase reaches 0.50 mol CO2 / mol amine. The phase separation is completed in 5 minutes, and the viscosity of the rich phase saturated with carbon dioxide is 18.5 mPa·s (40°C).

[0086] Comparative Example 3

[0087] An absorbent, by mass percentage, comprises: 30% MAE, 40% N-methylpyrrolidone, and 30% water.

[0088] In this example, the absorbent is a single-phase absorbent used for carbon dioxide capture. Specifically, the absorbent is used to absorb simulated flue gas with a CO2 volume fraction of 12%, at an absorption temperature of 40°C and an absorption time of 30 min. After absorbing CO2, the absorbent remains a single phase, with a CO2 loading of 0.50 mol CO2 / mol amine in the rich phase and a viscosity of 17.8 mPa·s (40°C).

[0089] Comparative Example 4

[0090] An absorbent, by mass percentage, comprises: 30% MAE, 40% diethylene glycol monoethyl ether, and 30% water.

[0091] In the diethylene glycol monoethyl ether structure, n is 2; R1 is ethylene; R2 is ethyl with 2 carbon atoms; R3 is H; and the number of hydroxyl groups is 1.

[0092] In this example, the absorbent is a single-phase absorbent used for carbon dioxide capture. Specifically, the absorbent is used to absorb simulated flue gas with a CO2 volume fraction of 12%, at an absorption temperature of 40°C and an absorption time of 30 min. After absorbing CO2, the absorbent remains a single phase, with a CO2 loading of 0.49 mol CO2 / mol amine in the rich phase and a viscosity of 22.8 mPa·s (40°C).

[0093] Comparative Example 5

[0094] An absorbent, by mass percentage, comprises: 30% MAE, 40% diethylene glycol diethyl ether, and 30% water.

[0095] In the diethylene glycol diethyl ether structure, n is 2; R1 is ethylene; R2 is ethyl with 2 carbon atoms; R3 is ethyl with 2 carbon atoms; and the number of hydroxyl groups is 0.

[0096] In this example, the absorbent is a two-phase absorbent used for carbon dioxide capture. Specifically, the absorbent was used to absorb simulated flue gas with a CO2 volume fraction of 12%, at an absorption temperature of 40°C, for 30 minutes. After absorbing CO2, the absorbent separated into two phases, with a light phase to rich phase ratio of 47%:53%. The load of the rich phase after CO2 absorption was 0.49 mol CO2 / mol amine. The phase separation was completed in 5 minutes, and the viscosity of the rich phase saturated with carbon dioxide was 27.6 mPa·s (40°C).

[0097] Through the structural design of Examples 1-3, the alcohol ether compounds possess moderate polarity, thus avoiding situations where phase separation does not occur or occurs too quickly. Furthermore, a balance between the volatility and viscosity of the alcohol ether compounds is achieved, which is beneficial for use as two-phase absorbents and results in good carbon dioxide capture performance. Examples 1-3 and Comparative Examples 1-2 and 5 are all used as two-phase absorbents. Compared to Comparative Examples 1-3, due to their suitable structural design, especially the value of n being greater than 2, the absorbents obtained after carbon dioxide capture exhibit lower viscosity and faster phase separation time.

[0098] The structural designs in Examples 4-5 resulted in alcohol ether compounds with high polarity, which is beneficial for maintaining a single phase before and after CO2 absorption. Furthermore, a balance between the volatility and viscosity of the alcohol ether compounds was achieved, making them suitable for use as single-phase absorbents and achieving good carbon dioxide capture performance. Examples 4-5 and Comparative Examples 3-4 were all used as single-phase absorbents. However, compared to Comparative Examples 3-4, Examples 4-5, due to their suitable structural design, especially with n values ​​greater than 2, resulted in absorbents with lower viscosity after carbon dioxide capture.

[0099] In summary, this invention optimizes the physicochemical properties of alcohol ether compounds by controlling their ether, hydroxyl, and alkyl structures to achieve suitable polarity, volatility, and viscosity. Using these compounds as components of an absorbent optimizes the absorbent's properties, resulting in absorbents with advantages such as low viscosity, low volatility, low cost, and high safety, thus achieving excellent application results in carbon dioxide capture.

Claims

1. A method for capturing carbon dioxide, characterized in that, Includes the following steps: Absorbents are used to absorb and treat flue gas containing carbon dioxide. The absorbent is composed of the following components in parts by weight: 40-48 parts alcohol ether compounds, 25-35 parts organic amines and 20-35 parts water; The alcohol ether compound in the absorbent has a mass percentage of 40-48%; The absorbent is a two-phase absorbent; the alcohol ether compound serves as a phase-separating agent for the absorbent. The alcohol ether compound is selected from triethylene glycol monobutyl ether; the organic amine is selected from MEA. The absorption treatment temperature is 30~50℃; the absorption treatment time is 20~40min.

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