Carbon dioxide absorbent and its preparation method and application

Abstract

The present invention relates to the technical field of carbon dioxide capture, and discloses a carbon dioxide absorbent, its preparation method, and application. The absorbent comprises component A, component B, and a solvent; wherein component A is an imidazole-modified amino acid ionic liquid, the cation of the ionic liquid is an imidazole cation, the imidazole cation contains an etheroxy group and / or an amino group, and the etheroxy group and / or amino group is directly connected to the N atom on the imidazole ring; the anion of the ionic liquid is selected from sarcosine, lysine, valine, or alanine; and component B is selected from aminoethylethanolamine, triethanolamine, or methyldiethanolamine. The carbon dioxide absorbent of the present invention can be used in carbon dioxide capture to improve the selectivity and acid gas load during carbon dioxide capture and reduce energy consumption.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of PCT International Patent Application No. PCT / CN2023 / 110298 filed on July 31, 2023, the contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to the technical field of carbon dioxide capture, and in particular to a carbon dioxide absorbent and a preparation method and application thereof. Background Art

[0004] Large-scale CO2 emissions are a major cause of global warming. Traditional atmospheric pressure CO2 separation processes typically remove CO2 through low-temperature absorption and high-temperature desorption, or recover some heat through heat pumps or mechanical vapor recompression to achieve energy savings and reduce consumption.

[0005] Currently, there are several mature processes for separating CO2 from gas mixtures, such as chemical absorption, physical absorption, adsorption, and membrane separation, each with its own scope of application. Of these methods, chemical absorption is currently the most widely used and widespread. In chemical absorption carbon capture technology, the performance of the chemical absorbent determines the CO2 capture effect and system energy consumption. Traditional chemical absorption, often using hot potash solution, ammonia, or alcohol amine solution as absorbents in the carbon capture process, is effective in capturing CO2 and the technology is relatively mature. However, chemical absorption suffers from high energy consumption, poor absorbent resistance, susceptibility to degradation and strong corrosiveness, and other issues. Decarbonization absorbents include mixed amines or formulated absorbents primarily composed of monoethanolamine (MEA), diethanolamine (DEA), and N-methyldiethanolamine (MDEA). MEA and DEA are primary and secondary amines with strong alkalinity, reacting quickly with CO2 and exhibiting good absorption rates. They are often used when the partial pressure of CO2 in the mixed gas is below 0.2 MPa. However, due to their high corrosiveness, MEA and DEA are generally used at concentrations as low as 15%-25%. The acid gas load is low, and the large solution circulation required to remove large amounts of CO2 results in high regeneration heat and power consumption. When the partial pressure of CO2 is higher than 0.2 MPa, various formulations of absorbents, mainly MDEA, are often used. Traditional formulations also present a contradiction between decarbonization purification and treatment load. Summary of the Invention

[0006] The purpose of the present invention is to overcome the problems of high loss, high energy consumption, and strong corrosiveness in the existing technology when capturing carbon dioxide, and to provide a carbon dioxide absorbent and its preparation method and application. The invention can improve the selectivity and acid gas load when capturing carbon dioxide by chemical absorption method, and reduce energy consumption.

[0007] In order to achieve the above-mentioned object, the first aspect of the present invention provides a carbon dioxide absorbent, which comprises a component A, a component B and a solvent; wherein the component A is an imidazole-modified amino acid ionic liquid, the cation of the ionic liquid is an imidazole cation, the imidazole cation contains an etheroxy group and / or an amino group, and the etheroxy group and / or amino group is directly connected to the N atom on the imidazole ring; the anion of the ionic liquid is selected from sarcosine, lysine, valine or alanine; and the component B is selected from aminoethylethanolamine, triethanolamine or methyldiethanolamine.

[0008] A second aspect of the present invention provides a method for preparing a carbon dioxide absorbent, comprising: mixing component A, component B and a solvent to obtain a carbon dioxide absorbent; wherein component A is an imidazole-modified amino acid ionic liquid, the cation of the ionic liquid is an imidazole cation, the imidazole cation contains an etheroxy group and / or an amino group, and the etheroxy group and / or amino group is directly connected to the N atom on the imidazole ring; the anion of the ionic liquid is selected from sarcosine, lysine, valine or alanine; and the component B is selected from aminoethylethanolamine, triethanolamine or methyldiethanolamine.

[0009] A third aspect of the present invention provides use of the aforementioned absorbent in capturing carbon dioxide.

[0010] A fourth aspect of the present invention provides a method for capturing carbon dioxide, the method comprising: capturing carbon dioxide using the aforementioned absorbent.

[0011] Through the above technical solution, the beneficial technical effects achieved by the present invention are as follows:

[0012] (1) The carbon dioxide absorbent proposed in the present invention includes an ionic liquid with an imidazole cation as a cation and sarcosine, lysine, valine or alanine as an anion, which is compounded with aminoethylethanolamine, triethanolamine or methyldiethanolamine to improve the selectivity and acid gas load when capturing carbon dioxide and reduce energy consumption.

[0013] (2) The cost, energy consumption, and loss of the absorbent of the present invention for capturing carbon dioxide are greatly reduced, while the capture capacity and stability are greatly improved. DETAILED DESCRIPTION

[0014] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0015] A first aspect of the present invention provides a carbon dioxide absorbent, comprising a component A, a component B, and a solvent; wherein the component A is an imidazole-modified amino acid ionic liquid, the cation of the ionic liquid is an imidazole cation, the imidazole cation contains an etheroxy group and / or an amino group, and the etheroxy group and / or amino group is directly connected to the N atom on the imidazole ring; the anion of the ionic liquid is selected from sarcosine, lysine, valine, or alanine; and the component B is selected from aminoethylethanolamine, triethanolamine, or methyldiethanolamine.

[0016] The present invention utilizes the multiple excellent properties of ionic liquids, such as extremely low vapor pressure, high thermal stability, strong dissolving power, stable properties, non-flammability, and low corrosivity. An ionic liquid with imidazole cations as cations and sarcosine, lysine, valine, or alanine as anions is selected and compounded with aminoethylethanolamine, triethanolamine, or methyldiethanolamine as an absorbent for capturing carbon dioxide. By combining the advantages of low energy consumption of physical methods and strong decarbonization ability of chemical methods, the present invention can effectively overcome the problems of low selectivity, low acid gas load, and large solvent loss in CO2 capture methods.

[0017] The present invention can improve the capture performance and reduce the viscosity by mixing the ionic liquid with the alcohol amine molecules. The composite ionic liquid has great application potential in CO2 absorption.

[0018] In some embodiments of the present invention, the imidazolium cation is selected from 3-etheroxy-1-methylimidazolium cation, 3-etheroxy-1-aminoimidazolium cation or 1,3-aminoimidazolium cation.

[0019] The molecular formula of the 3-etheroxy-1-methylimidazolium cation is shown in formula (1):

[0020]

[0021] The molecular formula of 3-etheroxy-1-aminoimidazolium cation is shown in formula (2):

[0022]

[0023] The molecular formula of 1,3-aminoimidazolium cation is shown in formula (3):

[0024]

[0025] In some embodiments of the present invention, the amino acid anion is selected from sarcosine anion, lysine anion, valine anion or alanine anion.

[0026] In the present invention, the molar ratio of the imidazole cation to the amino acid anion is 1:1.

[0027] In the present invention, ionic liquids include but are not limited to: 3-etheroxy-1-methylimidazole sarcosine ionic liquid, 3-etheroxy-1-methylimidazole lysine ionic liquid, 3-etheroxy-1-methylimidazole valine ionic liquid, 3-etheroxy-1-methylimidazole alanine ionic liquid, 3-etheroxy-1-aminoimidazole sarcosine ionic liquid, 3-etheroxy-1-aminoimidazole lysine ionic liquid, 3-etheroxy-1-methylimidazole valine ionic liquid, 3-etheroxy-1-aminoimidazole alanine ionic liquid, 1,3-aminoimidazole sarcosine ionic liquid, 1,3-aminoimidazole lysine ionic liquid, 1,3-aminoimidazole valine ionic liquid, and 1,3-aminoimidazole alanine ionic liquid.

[0028] In some specific embodiments, the ionic liquid preparation method is as follows: Accurately weigh the ionic liquid raw materials R1-imidazole (R1 is selected from an amino group or a methyl group) and R2-Br (R2 is selected from an amino group or an ether group), wherein the molar ratio of R1-imidazole to R2-Br is 1:1, dissolve them in anhydrous ethanol at room temperature, place them in a three-necked flask, and place the three-necked flask in a water bath thermostat in a fume hood. Stir and reflux the mixture at 15-25°C under N2 protection. After the reaction is completed, the ethanol is removed under reduced pressure using a rotary evaporator at 38-42°C, and the residue is dissolved in deionized water. Solid KOH is added in 10 batches with stirring, and the reaction system exotherms. After the KOH is completely added, the reaction is stirred for 60-62 minutes. Water is removed under reduced pressure using a rotary evaporator at 60-65°C, the imidazole bromide is extracted with ethanol-tetrahydrofuran, and the ethanol-tetrahydrofuran is removed under reduced pressure. The product after reduced pressure distillation is mixed with 2-2.2 times the volume of ethanol-water, and 1.1-1.15 times the mole of amino acid (sarcosine, lysine, valine or alanine) is added. The mixture is heated at 30-35° C. for 24-24.5 hours, taken out and cooled to room temperature, filtered, and the filtrate is evaporated to dryness and extracted with anhydrous ethanol, filtered again, and the filtrate is rotary evaporated to remove ethanol to obtain an ionic liquid.

[0029] In some embodiments of the present invention, based on the total mass of the absorbent, the sum of component A and component B is 25-40wt%, for example, 25wt%, 28wt%, 30wt%, 32wt%, 35wt%, 38wt%, 40wt%, and any value in the range consisting of any two values, preferably 30-35wt%.

[0030] In some embodiments of the present invention, the mass ratio of component A to component B is 1:0.8-2.5, for example, 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, 1:3, 1:1.4, 1:1.5, and any value in the range of any two values, preferably 1:1-1.5.

[0031] In some embodiments of the present invention, based on the total mass of the absorbent, the component A is 12-15wt%, for example, 12wt%, 13wt%, 14wt%, 15wt%, and any value in the range consisting of any two numerical values, preferably 13-14wt%; the component B is 12-30wt%, for example, 12wt%, 13wt%, 15wt%, 18wt%, 20wt%, 22wt%, 25wt%, 28wt%, 30wt%, and any value in the range consisting of any two numerical values, preferably 13-20wt%.

[0032] In some embodiments of the present invention, the solvent is water or an alcohol aqueous solution.

[0033] In some embodiments of the present invention, the alcohol in the alcohol aqueous solution is selected from one or more of propylene glycol, ethanol and ethylene glycol.

[0034] In some embodiments of the present invention, in the alcohol aqueous solution, the volume concentration of the alcohol is 5-15%; more preferably, the solvent is an ethanol aqueous solution with a volume concentration of 8-12%, and further preferably an ethanol aqueous solution with a volume concentration of 10%.

[0035] A second aspect of the present invention provides a method for preparing a carbon dioxide absorbent, comprising: mixing component A, component B, and a solvent to obtain a carbon dioxide absorbent; wherein component A is an imidazole-modified amino acid ionic liquid, the cation of the ionic liquid is an imidazole cation, the imidazole cation contains an etheroxy group and / or an amino group, and the etheroxy group and / or amino group is directly connected to the N atom on the imidazole ring; the anion of the ionic liquid is selected from sarcosine, lysine, valine, or alanine; and the component B is selected from aminoethylethanolamine, triethanolamine, or methyldiethanolamine.

[0036] In some preferred embodiments of the present invention, the preparation method specifically comprises the following steps:

[0037] First, the B component is mixed with a solvent to obtain a mixed liquid; then the mixed liquid is mixed with the A component to obtain a carbon dioxide absorbent.

[0038] The present invention provides a method for capturing carbon dioxide using a composite solvent of ionic liquid and ethanolamine. Compared with traditional carbon dioxide absorbents, the absorbent obtained by the method of the present invention has a greater acid gas load and a higher carbon dioxide capture rate.

[0039] In some embodiments of the present invention, the imidazolium cation is selected from 3-etheroxy-1-methylimidazolium cation, 3-etheroxy-1-aminoimidazolium cation or 1,3-aminoimidazolium cation.

[0040] In some embodiments of the present invention, the amino acid anion is selected from sarcosine anion, lysine anion, valine anion or alanine anion.

[0041] In some embodiments of the present invention, based on the total mass of the absorbent, the sum of the component A and the component B is 25-40 wt%, preferably 30-35 wt%.

[0042] In some embodiments of the present invention, the mass ratio of component A to component B is 1:0.8-2.5, preferably 1:1-1.5.

[0043] In some embodiments of the present invention, based on the total mass of the absorbent, the component A accounts for 12-15 wt%, preferably 13-14 wt%; the component B accounts for 12-30 wt%, preferably 13-20 wt%.

[0044] In some embodiments of the present invention, the solvent is water or an alcohol aqueous solution.

[0045] In some embodiments of the present invention, the alcohol in the alcohol aqueous solution is selected from one or more of propylene glycol, ethanol and ethylene glycol.

[0046] In some embodiments of the present invention, in the alcohol aqueous solution, the volume concentration of the alcohol is 5-15%; more preferably, the solvent is an ethanol aqueous solution with a volume concentration of 8-12%, and further preferably an ethanol aqueous solution with a volume concentration of 10%.

[0047] A third aspect of the present invention provides use of the aforementioned absorbent in capturing carbon dioxide.

[0048] The absorbent of the present invention can also be used to capture carbon dioxide from high-pressure gas sources. Compared to conventional high-pressure gas source carbon dioxide absorbents, the absorbent of the present invention has a greater acid gas load and a higher carbon dioxide capture rate. The absorbent of the present invention effectively overcomes the problems of low selectivity, low acid gas load, and high solvent loss associated with conventional high-pressure gas source CO2 capture methods. It can improve the selectivity and acid gas load of carbon dioxide captured from high-pressure gas sources while reducing energy consumption.

[0049] A fourth aspect of the present invention provides a method for capturing carbon dioxide, the method comprising: capturing carbon dioxide using the aforementioned absorbent.

[0050] In some embodiments of the present invention, the capture temperature is 20-80°C, for example, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, and any value in the range of any two values, preferably 30-70°C.

[0051] In some embodiments of the present invention, the method further comprises: after the capture is completed, regenerating the absorbent that has absorbed the carbon dioxide to release the carbon dioxide.

[0052] In some embodiments of the present invention, the regeneration temperature is 60-120°C, for example, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 100°C, 110°C, 120°C, and any value in the range of any two values, preferably 65-80°C.

[0053] Specifically, the method mainly includes the following steps: contacting the raw gas with the absorbent described in the present invention, and carbon dioxide is absorbed into the absorbent solution to form a rich liquid; then heating and regenerating the rich liquid that absorbs carbon dioxide to produce a carbon dioxide product and a lean liquid, and then circulating the lean liquid for absorption.

[0054] The present invention is described in detail below by way of examples, but the scope of the present invention is not limited to the following description. In the following examples and comparative examples, where specific conditions are not specified, the experiments were conducted under conventional conditions or those recommended by the manufacturer. All reagents and instruments used, where the manufacturer is not specified, are commercially available conventional products.

[0055] In the following examples and comparative examples,

[0056] The lean liquid acid gas load is measured by a carbon dioxide generator.

[0057] The regeneration energy consumption is reflected by the regeneration temperature, which is measured by a thermometer. A high regeneration temperature indicates that a high regeneration heat energy is required, resulting in high regeneration energy consumption.

[0058] Selectivity is reflected by the acid gas load. When the carbon dioxide content and flow rate of the feed gas remain unchanged, the higher the acid gas load, the better the selectivity.

[0059] Example 1

[0060] The carbon dioxide absorbent comprises: 13 wt% of ionic liquid, 18 wt% of N-methyldiethanolamine (MDEA) and 69 wt% of a 10 vol% aqueous ethanol solution; wherein the cation of the ionic liquid is a 3-etheroxy-1-methylimidazolium cation, and the anion is a lysine anion.

[0061] The preparation method of the carbon dioxide absorbent comprises the following steps:

[0062] (1) Preparation of 3-methylimidazole-1-methylimidazolium lysine ionic liquid: Accurately weigh equimolar amounts of 3-methylimidazole and etheroxy bromide, dissolve them in anhydrous ethanol at room temperature, place them in a three-necked flask, and place the three-necked flask in a water bath thermostat in a fume hood. Stir and reflux the reaction at room temperature under N2 protection. After the reaction is completed, use a rotary evaporator to remove ethanol under reduced pressure at 40°C, and dissolve the residue in deionized water. Add KOH solid in 10 batches under stirring, and the reaction system will release heat. After all the KOH has been added, continue stirring and react for 60 minutes. Use a rotary evaporator to remove water under reduced pressure at 60°C, extract the imidazole bromide with ethanol-tetrahydrofuran, and remove the ethanol-tetrahydrofuran under reduced pressure. The product after reduced pressure distillation was mixed with 2 volumes of ethanol-water, 1.1 moles of lysine was added, and the mixture was heated at 30°C for 24 hours. The mixture was cooled to room temperature and filtered. The filtrate was evaporated to dryness and extracted with anhydrous ethanol, filtered again, and the filtrate was rotary evaporated to remove ethanol to obtain 3-etheroxy-1-methylimidazolium lysine ionic liquid;

[0063] (2) MDEA and a 10 vol% ethanol aqueous solution were first mixed to form a mixed solution; and then the 3-etheroxy-1-methylimidazolium lysine ionic liquid obtained in step (1) was added to obtain a carbon dioxide absorbent.

[0064] Application of carbon dioxide absorbent: The obtained carbon dioxide absorbent is used to capture carbon dioxide. The mixed gas pressure is 0.5 MPa, the temperature is room temperature, the volume content of CO2 in the gas source is 13.0%, and the rest is N2.

[0065] Carbon dioxide capture: 200 mL of absorbent was placed in an absorption bottle with magnetic stirring. The absorption temperature was maintained at 40°C. Gas was then slowly introduced at a flow rate of 250 mL / min. 1 mL of absorbent was sampled periodically and analyzed using a carbon dioxide generator until the molar CO2 content in the absorbent remained constant. Testing showed that absorption equilibrium was reached in 45 minutes, with an absorbed CO2 content of 1.5 mol CO2 / mol solvent. The absorbent was then regenerated at 65°C, achieving a regeneration rate of 61.2%. The results are shown in Table 1.

[0066] Examples 2-7

[0067] The absorbent was prepared according to the method of Example 1, except that the contents of ionic liquid and N-methyldiethanolamine (MDEA) were different. The results are shown in Table 1.

[0068] Example 8

[0069] The absorbent was prepared according to the method of Example 1, except that the cation of the ionic liquid was 3-etheroxy-1-methylimidazolium cation and the anion was alanine anion. The results are shown in Table 1.

[0070] The preparation method of 3-etheroxy-1-methylimidazolium alanine ionic liquid comprises the following steps:

[0071] Accurately weigh equimolar amounts of 3-methylimidazole and etheroxybromide, dissolve them in anhydrous ethanol at room temperature, place them in a three-necked flask, and place the flask in a thermostatic water bath in a fume hood. Stir and reflux the mixture at room temperature under N2 protection. After the reaction is complete, remove the ethanol using a rotary evaporator at 40°C under reduced pressure, and dissolve the residue in deionized water. Add solid KOH in 10 batches while stirring, causing the reaction to exotherm. After the KOH is completely added, continue stirring and react for 60 minutes. Remove the water using a rotary evaporator at 60°C under reduced pressure, extract the imidazole bromide with ethanol-tetrahydrofuran, and remove the ethanol and tetrahydrofuran under reduced pressure. The product after reduced pressure distillation is mixed with 2 volumes of ethanol-water, add 1.1 moles of alanine, and heat at 30°C for 24 hours. Remove the mixture, cool to room temperature, filter, and evaporate the filtrate to dryness, extract with anhydrous ethanol, and filter again. The resulting filtrate is then rotary evaporated to remove the ethanol, yielding the 3-etheroxy-1-methylimidazole alanine ionic liquid.

[0072] Example 9

[0073] The absorbent was prepared according to the method of Example 1, except that the cation of the ionic liquid was a 3-etheroxy-1-aminoimidazole cation and the anion was a sarcosine anion. The results are shown in Table 1.

[0074] The preparation method of 3-etheroxy-1-aminoimidazole sarcosine ionic liquid comprises the following steps:

[0075] Accurately weigh equimolar amounts of 3-aminoimidazole and etheroxybromide, dissolve them in anhydrous ethanol at room temperature, place them in a three-necked flask, and place the flask in a thermostatic water bath in a fume hood. Stir and reflux the mixture at room temperature under N2 protection. After the reaction is complete, remove the ethanol using a rotary evaporator at 40°C under reduced pressure, and dissolve the residue in deionized water. Add solid KOH in 10 batches while stirring, causing the reaction to exotherm. After the KOH is completely added, continue stirring and react for 60 minutes. Remove the water using a rotary evaporator at 60°C under reduced pressure, extract the imidazole bromide with ethanol-tetrahydrofuran, and remove the ethanol and tetrahydrofuran under reduced pressure. The product after reduced pressure distillation is mixed with 2 volumes of ethanol-water, add 1.1 moles of sarcosine, and heat at 30°C for 24 hours. Remove the mixture, cool to room temperature, filter, and evaporate the filtrate to dryness, extract with anhydrous ethanol, and filter again. The filtrate is then rotary evaporated to remove the ethanol, yielding the 3-etheroxy-1-aminoimidazole sarcosine ionic liquid.

[0076] Example 10

[0077] The absorbent was prepared according to the method of Example 1, except that triethanolamine was used instead of N-methyldiethanolamine. The results are shown in Table 1.

[0078] Example 11

[0079] The absorbent was prepared according to the method of Example 1, except that the cation of the ionic liquid was 1,3-aminoimidazole cation and the anion was valine anion. The results are shown in Table 1.

[0080] The preparation method of 1,3-aminoimidazole valine ionic liquid comprises the following steps:

[0081] Accurately weigh equimolar amounts of 3-aminoimidazole and aminobromide, dissolve them in anhydrous ethanol at room temperature, place them in a three-necked flask, and place the flask in a thermostatic water bath in a fume hood. Stir and reflux the mixture at room temperature under N2 protection. After the reaction is complete, remove the ethanol using a rotary evaporator at 40°C under reduced pressure, and dissolve the residue in deionized water. Add solid KOH in 10 batches while stirring, causing the reaction to exotherm. After the KOH is completely added, continue stirring and react for 60 minutes. Remove the water using a rotary evaporator at 60°C under reduced pressure, extract the imidazole bromide with ethanol-tetrahydrofuran, and remove the ethanol and tetrahydrofuran under reduced pressure. The product after reduced pressure distillation is mixed with 2 volumes of ethanol-water, add 1.1 moles of valine, and heat at 30°C for 24 hours. Remove the mixture, cool to room temperature, filter, and evaporate the filtrate to dryness, extract with anhydrous ethanol, and filter again. The filtrate is then rotary evaporated to remove the ethanol, yielding the 1,3-aminoimidazole valine ionic liquid.

[0082] Example 12

[0083] The absorbent was prepared according to the method of Example 1, except that the 10 vol% ethanol aqueous solution was replaced by a 5 vol% ethanol aqueous solution. The results are shown in Table 1.

[0084] Example 13

[0085] The absorbent was prepared according to the method of Example 1, except that the 10 vol% ethanol aqueous solution was replaced with a 1 vol% ethanol aqueous solution. The results are shown in Table 1.

[0086] Example 14

[0087] The absorbent was prepared according to the method of Example 1, except that the 10 vol% ethanol aqueous solution was replaced by water. The results are shown in Table 1.

[0088] Comparative Example 1

[0089] The absorbent was prepared according to the method of Example 1, except that the ionic liquid was not contained. The results are shown in Table 1.

[0090] Comparative Example 2

[0091] The absorbent was prepared according to the method of Example 1, except that N-methyldiethanolamine (MDEA) was not contained. The results are shown in Table 1.

[0092] Comparative Example 3

[0093] An absorbent was prepared according to the method of Example 1, except that the ionic liquid was replaced with a bisaminoimidazole ionic liquid. The CO2 absorption capacity was 1.13 mol CO2 / mol solvent, as shown in Table 1.

[0094] Comparative Example 4

[0095] An absorbent was prepared according to the method of Example 1, except that the ionic liquid was replaced with 2-amino-2-methyl-1-propanol (AMP). The CO2 absorption capacity was 0.97 mol CO2 / mol solvent, as shown in Table 1.

[0096] Table 1

[0097]

[0098] From the results in Table 1, it can be seen that, compared with the absorbents of Comparative Examples 1-4, the absorbents of Examples 1-14 of the present invention have a higher acid gas load, a lower tail gas carbon dioxide content, and a regeneration temperature. By comparing Example 1 with Comparative Examples 1 and 2, it can be seen that Example 1 contains both ionic liquid and N-methyldiethanolamine, while Comparative Example 1 does not contain an ionic liquid and Comparative Example 2 does not contain N-methyldiethanolamine. From the result data, it can be seen that simultaneously containing the ionic liquid provided by the present invention and N-methyldiethanolamine can achieve a better effect, indicating that the two have a synergistic effect. By comparing Example 1 with Comparative Examples 3 and 4, it can be seen that replacing the ionic liquid provided by the present invention with other ionic liquids cannot achieve the technical effect of the embodiments of the present invention. In summary, compounding an ionic liquid with an imidazole cation as a cation and sarcosine, lysine, valine, or alanine as an anion with aminoethylethanolamine, triethanolamine, or methyldiethanolamine can improve the selectivity and acid gas load when capturing carbon dioxide and reduce energy consumption.

[0099] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A carbon dioxide absorbent, characterized in that The absorbent comprises component A, component B and a solvent; wherein component A is an imidazole modified amino acid ionic liquid, the cation of the ionic liquid is an imidazole cation, the imidazole cation contains an ether radical and / or an amino radical, and the ether radical and / or the amino radical are directly connected to the nitrogen atom on the imidazole ring; the anion of the ionic liquid is selected from amino acid anions; and the component B is selected from aminoethylethanolamine, triethanolamine or methyldiethanolamine. The imidazolium cation is selected from 3-etheroxy-1-methylimidazolium cation, 3-etheroxy-1-aminoimidazolium cation or 1,3-aminoimidazolium cation; The amino acid anion is selected from sarcosine anion, lysine anion, valine anion or alanine anion Based on the total mass of the absorbent, the sum of the component A and the component B is 25-40wt%; The mass ratio of component A to component B is 1:0.8-2.5; Based on the total mass of the absorbent, the A component accounts for 12-15 wt%, and the B component accounts for 12-30 wt%; The solvent is water or an alcohol aqueous solution.

2. The absorbent according to claim 1, wherein Based on the total mass of the absorbent, the sum of the component A and the component B is 30-35 wt %.

3. The absorbent according to claim 1 or 2, wherein The mass ratio of the component A to the component B is 1:1-1.

5.

4. The absorbent according to claim 1 or 2, wherein Based on the total mass of the absorbent, the A component accounts for 13-14 wt%; the B component accounts for 13-20 wt%.

5. The absorbent according to claim 1 or 2, wherein The alcohol in the alcohol aqueous solution is selected from one or more of propylene glycol, ethanol and ethylene glycol; And / or, in the alcohol aqueous solution, the volume concentration of the alcohol is 5-15%. The absorbent according to claim 5 , wherein The solvent is an ethanol aqueous solution with a volume concentration of 8-12%.

7. A method for preparing a carbon dioxide absorbent, characterized in that: The preparation method comprises: Component A, component B, and a solvent are mixed to obtain a carbon dioxide absorbent; wherein, component A is an imidazole-modified amino acid ionic liquid, the cation of the ionic liquid is an imidazole cation, the imidazole cation contains an ether group and / or an amino group, and the ether group and / or amino group are directly connected to the nitrogen atom on the imidazole ring; the anion of the ionic liquid is selected from sarcosine, lysine, valine, or alanine; and the component B is selected from aminoethylethanolamine, triethanolamine, or methyldiethanolamine; The imidazolium cation is selected from 3-etheroxy-1-methylimidazolium cation, 3-etheroxy-1-aminoimidazolium cation or 1,3-aminoimidazolium cation; The amino acid anion is selected from sarcosine anion, lysine anion, valine anion or alanine anion Based on the total mass of the absorbent, the sum of the component A and the component B is 25-40wt%; The mass ratio of component A to component B is 1:0.8-2.5; Based on the total mass of the absorbent, the A component accounts for 12-15 wt%, and the B component accounts for 12-30 wt%; The solvent is water or an alcohol aqueous solution.

8. The preparation method according to claim 7, wherein Based on the total mass of the absorbent, the sum of the component A and the component B is 30-35 wt%; And / or, the mass ratio of component A to component B is 1:1-1.5; And / or, based on the total mass of the absorbent, the component A accounts for 13-14 wt%; the component B accounts for 13-20 wt%.

9. The preparation method according to claim 7 or 8, wherein The alcohol in the alcohol aqueous solution is selected from one or more of propylene glycol, ethanol and ethylene glycol; And / or, in the alcohol aqueous solution, the volume concentration of the alcohol is 5-15%.

10. The preparation method according to claim 9, wherein The solvent is an ethanol aqueous solution with a volume concentration of 8-12%.

11. Use of the absorbent according to any one of claims 1 to 6 or the absorbent prepared by the preparation method according to any one of claims 7 to 10 in capturing carbon dioxide.

12. A method for capturing carbon dioxide, characterized in that: The method comprises: capturing carbon dioxide using the absorbent according to any one of claims 1 to 6 or the absorbent prepared by the preparation method according to any one of claims 7 to 10.

13. The method according to claim 12, wherein: The capture temperature is 20-80°C.

14. The method according to claim 12 or 13, wherein: The method further comprises: after the capture is completed, regenerating the absorbent that has absorbed the carbon dioxide to release the carbon dioxide.

15. The method according to claim 14, wherein The regeneration temperature is 60-120°C.

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