Carbon dioxide absorbent, preparation method therefor and use thereof

Abstract

A carbon dioxide absorbent, a preparation method therefor and a use thereof. The absorbent comprises a component A, a component B and a solvent, the component A being an imidazole-modified amino acid ionic liquid; a cation of the ionic liquid is an imidazole cation, the imidazole cation having a structure as shown in formula (I), where R1, R2, R3, R4 and R5 each independently being hydrogen or a C1-C10 straight-chain or branched alkyl; the anion of the ionic liquid is selected from sarcosine, lysine, valine or alanine; the component B is selected from aminoethylethanolamine, triethanolamine or N-methyldiethanolamine; the solvent is an aqueous solution of alcohol, the volume concentration of alcohol thereof being 5-15%. Use of the carbon dioxide absorbent in capturing carbon dioxide can improve selectivity and acid gas load during carbon dioxide capture, and reduce energy consumption.

Description

Carbon dioxide absorbent and its preparation method and application

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of PCT International Application No. PCT / CN2023 / 110298 filed on July 31, 2023 and Chinese Patent Application No. 202311222921.8 filed on September 21, 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.

[0006] Summary of the Invention

[0007] The purpose of the present invention is to overcome the problems of high loss, high energy consumption, and strong corrosiveness in the capture of carbon dioxide in the existing technology, 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.

[0008] To achieve the above-mentioned object, the present invention provides a carbon dioxide absorbent in a first aspect, 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, and the imidazole cation has a structure represented by formula (I); the anion of the ionic liquid is selected from sarcosine, lysine, valine, or alanine; the component B is selected from aminoethylethanolamine, triethanolamine, or N-methyldiethanolamine; and the solvent is an aqueous alcohol solution, wherein the volume concentration of the alcohol in the aqueous alcohol solution is 5-15%.

[0009] wherein R1, R2, R3, R4 and R5 are each independently hydrogen or a C1-C10 straight or branched chain alkyl group.

[0010] 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, and the imidazole cation has a structure represented by formula (I); the anion of the ionic liquid is selected from sarcosine, lysine, valine, or alanine; the component B is selected from aminoethylethanolamine, triethanolamine, or N-methyldiethanolamine; and the solvent is an alcohol aqueous solution, wherein the volume concentration of the alcohol in the alcohol aqueous solution is 5-15%;

[0011] wherein R1, R2, R3, R4 and R5 are each independently hydrogen or a C1-C10 straight or branched chain alkyl group.

[0012] A third aspect of the present invention provides use of the aforementioned absorbent in capturing carbon dioxide.

[0013] A fourth aspect of the present invention provides a method for capturing carbon dioxide, the method comprising: capturing carbon dioxide using the aforementioned absorbent.

[0014] Through the above technical solution, the beneficial technical effects achieved by the present invention are as follows:

[0015] (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 N-methyldiethanolamine and an alcohol aqueous solution to improve the selectivity and acid gas load when capturing carbon dioxide and reduce energy consumption.

[0016] (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. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] FIG1 is a carbon-NMR spectrum of the carbon dioxide absorbent obtained in Example 1 of the present invention;

[0018] FIG2 is a carbon-NMR spectrum of the carbon dioxide absorbent obtained in Comparative Example 7 of the present invention;

[0019] FIG3 is a carbon-NMR spectrum of the carbon dioxide absorbent obtained in Comparative Example 8 of the present invention. DETAILED DESCRIPTION

[0020] 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.

[0021] 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, and the imidazole cation has a structure represented by formula (I); the anion of the ionic liquid is selected from sarcosine, lysine, valine, or alanine; the component B is selected from aminoethylethanolamine, triethanolamine, or N-methyldiethanolamine; and the solvent is an alcohol aqueous solution, wherein the volume concentration of the alcohol in the alcohol aqueous solution is 5-15%.

[0022] wherein R1, R2, R3, R4 and R5 are each independently hydrogen or a C1-C10 straight or branched chain alkyl group.

[0023] In the present invention, the absorbent formulation can be determined by infrared spectroscopy to determine whether the main functional groups such as imidazole, etheroxy, and amino groups exist, and the N-terminal groups on the imidazole ring can be determined by the NMR carbon spectrum. + The chemical shift of the attached carbon atom determines the attached group.

[0024] In the present invention, after the carbon dioxide absorbent absorbs carbon dioxide, the amino group on the cation reacts with carbon dioxide to form carbamate, and the absorbent before and after the reaction can be detected by infrared spectroscopy. The present invention utilizes the various excellent properties of ionic liquids, such as extremely low vapor pressure, high thermal stability, strong dissolving power, stable properties, non-flammability, and low corrosiveness. An ionic liquid with an imidazole cation as the cation and sarcosine, lysine, valine, or alanine as the anion is selected and compounded with aminoethylethanolamine, triethanolamine, or N-methyldiethanolamine and an aqueous alcohol solution as an absorbent for capturing carbon dioxide. 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.

[0025] 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.

[0026] In the present invention, examples of the C1-C10 straight-chain or branched alkyl group may be any one of methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, tert-pentyl, neopentyl, n-hexyl, isohexyl, n-heptyl, isoheptyl, 2-methylhexyl, 2-ethylhexyl, 1-methylheptyl, 2-methylheptyl, n-octyl, isooctyl, n-nonyl, isononyl and 3,5,5-trimethylhexyl.

[0027] In some embodiments of the present invention, R1, R2, R3, R4 and R5 are each independently hydrogen or a C1-C6 straight chain or branched alkyl group; preferably hydrogen or a C1-C4 straight chain or branched alkyl group; more preferably hydrogen, methyl or ethyl.

[0028] When R1, R2, R3, R4 and R5 are each independently hydrogen, the imidazole cation is a 3-etheroxy-1-aminoimidazolium cation having a structure shown in formula (1):

[0029] In the present invention, the molar ratio of the imidazole cation to the amino acid anion is 1:1.

[0030] In the present invention, ionic liquids include but are not limited to: 3-etheroxy-1-aminoimidazole sarcosine ionic liquid, 3-etheroxy-1-aminoimidazole lysine ionic liquid, 3-etheroxy-1-aminoimidazole valine ionic liquid, and 3-etheroxy-1-aminoimidazole alanine ionic liquid.

[0031] In some specific embodiments, the ionic liquid is prepared as follows: Accurately weigh the ionic liquid raw materials R1-imidazole (R1 is an amino group) and R2-Br (R2 is an ether group), wherein the molar ratio of R1-imidazole to R2-Br is 1:1. Dissolve the mixture in anhydrous ethanol at room temperature and place it in a three-necked flask. The flask is then placed in a water bath in a fume hood. Stir and reflux the mixture at 15-25°C under N2 protection. After the reaction is complete, 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 while 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.

[0032] 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%.

[0033] 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.

[0034] 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%, 17wt%, 20wt%, 22wt%, 25wt%, 28wt%, 30wt%, and any value in the range consisting of any two numerical values, preferably 13-20wt%.

[0035] 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.

[0036] In some embodiments of the present invention, the solvent is an ethanol aqueous solution with a volume concentration of 8-12%, more preferably an ethanol aqueous solution with a volume concentration of 10%.

[0037] 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 the carbon dioxide absorbent; wherein component A is an imidazole-modified amino acid ionic liquid, the cation of the ionic liquid is an imidazole cation, and the imidazole cation has a structure represented by formula (I); the anion of the ionic liquid is selected from sarcosine, lysine, valine, or alanine; the component B is selected from aminoethylethanolamine, triethanolamine, or N-methyldiethanolamine; and the solvent is an aqueous alcohol solution, wherein the volume concentration of the alcohol in the aqueous alcohol solution is 5-15%.

[0038] wherein R1, R2, R3, R4 and R5 are each independently hydrogen or a C1-C10 straight or branched chain alkyl group.

[0039] In some preferred embodiments of the present invention, the preparation method specifically comprises the following steps:

[0040] 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.

[0041] 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.

[0042] In some embodiments of the present invention, R1, R2, R3, R4 and R5 are each independently hydrogen or a C1-C6 straight chain or branched alkyl group; preferably hydrogen or a C1-C4 straight chain or branched alkyl group; more preferably hydrogen, methyl or ethyl.

[0043] When R1, R2, R3, R4 and R5 are each independently hydrogen, the imidazolium cation is a 3-etheroxy-1-aminoimidazolium cation.

[0044] 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%.

[0045] 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.

[0046] 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%.

[0047] 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.

[0048] In some embodiments of the present invention, the solvent is an ethanol aqueous solution with a volume concentration of 8-12%, more preferably an ethanol aqueous solution with a volume concentration of 10%.

[0049] A third aspect of the present invention provides use of the aforementioned absorbent in capturing carbon dioxide.

[0050] 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.

[0051] A fourth aspect of the present invention provides a method for capturing carbon dioxide, the method comprising: capturing carbon dioxide using the aforementioned absorbent.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] In the following examples and comparative examples,

[0058] The lean liquid acid gas load is measured by a carbon dioxide generator.

[0059] 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.

[0060] 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.

[0061] Example 1

[0062] The carbon dioxide absorbent comprises: 14 wt% of ionic liquid, 17 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-aminoimidazole cation, and the anion is a lysine anion.

[0063] The preparation method of the carbon dioxide absorbent comprises the following steps:

[0064] (1) Preparation of 3-Ethoxy-1-aminoimidazole lysine ionic liquid: Accurately weigh equimolar amounts of 3-aminoimidazole 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 mixture at room temperature under N2 protection. After the reaction is completed, remove the ethanol at 40°C under reduced pressure using a rotary evaporator, and dissolve the residue in deionized water. Add KOH solid in 10 batches while stirring, and the reaction system will release heat. After all the KOH has been added, continue stirring and react for 60 minutes. Remove water at 60°C under reduced pressure using a rotary evaporator, 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 times the molar amount of lysine was added, and the mixture was heated at 30°C for 24 hours. The mixture was taken out and cooled to room temperature, filtered, and the filtrate was evaporated to dryness and extracted with anhydrous ethanol, and then filtered. The filtrate was rotary evaporated to remove ethanol to obtain 3-etheroxy-1-aminoimidazole lysine ionic liquid.

[0065] (2) MDEA and a 10 vol% ethanol aqueous solution were first mixed to form a mixed solution; and the 3-etheroxy-1-aminoimidazole lysine ionic liquid obtained in step (1) was then added to obtain a carbon dioxide absorbent.

[0066] 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.

[0067] 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.

[0068] Examples 2-7

[0069] The absorbent was prepared according to the method of Example 1, except that the contents of ionic liquid and N-methyldiethanolamine (MDEA) were different, as shown in Table 1, and the balance was 10 vol% ethanol aqueous solution. The results are shown in Table 1.

[0070] Example 8

[0071] An absorbent was prepared according to the method of Example 1, except that the composition of the carbon dioxide absorbent was: 14 wt% ionic liquid, 17 wt% triethanolamine, and 69 wt% 10 vol% ethanol aqueous solution; wherein the cation of the ionic liquid was a 3-etheroxy-1-aminoimidazole cation, and the anion was a lysine anion.

[0072] Example 9

[0073] An absorbent was prepared according to the method of Example 1, except that the composition of the carbon dioxide absorbent was: 14 wt% of ionic liquid, 17 wt% of aminoethylethanolamine, and 69 wt% of a 10 vol% aqueous ethanol solution; wherein the cation of the ionic liquid was a 3-etheroxy-1-aminoimidazole cation, and the anion was a lysine anion.

[0074] Example 10

[0075] 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 an alanine anion. The results are shown in Table 1.

[0076] The preparation method of 3-etheroxy-1-aminoimidazole alanine ionic liquid comprises the following steps:

[0077] 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 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-aminoimidazole alanine ionic liquid.

[0078] Example 11

[0079] 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.

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

[0081] 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.

[0082] Example 12

[0083] 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 valine anion. The results are shown in Table 1.

[0084] The preparation method of 3-etheroxy-1-aminoimidazole cation valine ionic liquid comprises the following steps:

[0085] 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 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 3-etheroxy-1-aminoimidazole valine ionic liquid.

[0086] Example 13

[0087] 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.

[0088] Example 14

[0089] The absorbent was prepared according to the method of Example 1, except that the 10 vol% ethanol aqueous solution was replaced with an 8 vol% ethanol aqueous solution. The results are shown in Table 1.

[0090] Comparative Example 1

[0091] The absorbent was prepared according to the method of Example 1, except that the composition of the carbon dioxide absorbent was: 31 wt% N-methyldiethanolamine (MDEA) and 69 wt% 10 vol% ethanol aqueous solution. The results are shown in Table 1.

[0092] Comparative Example 2

[0093] An absorbent was prepared according to the method of Example 1, except that the carbon dioxide absorbent composition was: 31 wt% ionic liquid and 69 wt% 10 vol% aqueous ethanol solution; the cation of the ionic liquid was 3-etheroxy-1-aminoimidazole cation, and the anion was lysine anion. The results are shown in Table 1.

[0094] Comparative Example 3

[0095] An absorbent was prepared according to the method of Example 1, except that the ionic liquid was a bisaminoimidazole alanine ionic liquid. The CO2 absorption capacity was 1.13 mol CO2 / mol solvent, as shown in Table 1.

[0096] Comparative Example 4

[0097] An absorbent was prepared according to the method of Example 1, except that the carbon dioxide absorbent consisted of 31 wt% 2-amino-2-methyl-1-propanol (AMP) and 69 wt% 10 vol% ethanol in water. The CO₂ absorption capacity was 0.97 mol CO₂ / mol solvent, as shown in Table 1.

[0098] Comparative Example 5

[0099] An absorbent was prepared according to the method of Example 1, except that the ionic liquid was 3-etheroxy-1-aminomethylimidazolyl lysine. The CO2 absorption capacity was 1.12 mol CO2 / mol solvent, as shown in Table 1.

[0100] Comparative Example 6

[0101] An absorbent was prepared according to the method of Example 1, except that the ionic liquid was 3-etheroxy-1-aminoethylimidazolyl lysine ionic liquid. The CO2 absorption capacity was 1.22 mol CO2 / mol solvent, as shown in Table 1.

[0102] Comparative Example 7

[0103] An absorbent was prepared according to the method of Example 1, except that the carbon dioxide absorbent composition was: 14 wt% ionic liquid, 17 wt% N-methyldiethanolamine (MDEA), and 69 wt% water; the cation of the ionic liquid had the structure shown in formula (2), and the anion was a lysine anion. The results are shown in Table 1.

[0104] Comparative Example 8

[0105] An absorbent was prepared according to the method of Example 1, except that the carbon dioxide absorbent composition was: 14 wt% ionic liquid, 17 wt% N-methyldiethanolamine (MDEA), and 69 wt% water; the cation of the ionic liquid had the structure shown in formula (3), and the anion was a lysine anion. The results are shown in Table 1.

[0106] The carbon dioxide absorbent obtained in Example 1 was tested by nuclear magnetic carbon spectroscopy, and the nuclear magnetic carbon spectrum shown in Figure 1 was obtained. The carbon dioxide absorbent obtained in Comparative Example 7 was tested by nuclear magnetic carbon spectroscopy, and the nuclear magnetic carbon spectrum shown in Figure 2 was obtained. The carbon dioxide absorbent obtained in Comparative Example 8 was tested by nuclear magnetic carbon spectroscopy, and the nuclear magnetic carbon spectrum shown in Figure 3 was obtained. By comparing Figures 1 and 2, it can be seen that the C between the two N on the imidazole ring and the CH2 and CH3 on the ether group in the two structures have different chemical shifts and can be clearly distinguished. By comparing Figures 2 and 3, it can be seen that compared with N + The connected carbons have different chemical shifts. The chemical shift in Figure 2 is 78.2 ppm; the chemical shift in Figure 3 is 50 ppm, and Figure 3 has an additional peak at 74 ppm due to the extra carbon.

[0107] Comparative Example 9

[0108] An absorbent was prepared according to the method of Example 1, except that the carbon dioxide absorbent composition was: 14 wt% ionic liquid, 17 wt% N-methyldiethanolamine (MDEA), and 69 wt% 1 vol% aqueous ethanol solution. The cation of the ionic liquid was a 3-etheroxy-1-aminoimidazole cation, and the anion was a lysine anion. The results are shown in Table 1.

[0109] Comparative Example 10

[0110] An absorbent was prepared according to the method of Example 1, except that the carbon dioxide absorbent composition was: 14 wt% ionic liquid, 17 wt% N-methyldiethanolamine (MDEA), and 69 wt% water; the cation of the ionic liquid was a 3-etheroxy-1-aminoimidazole cation, and the anion was a lysine anion. The results are shown in Table 1.

[0111] Table 1

[0112] From the results in Table 1, it can be seen that, compared with the absorbents of Comparative Examples 1-8, 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, Comparative Example 1 does not contain 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 better results, indicating that the two have a synergistic effect. By comparing Example 1 with Comparative Examples 3-8, it can be seen that replacing the ionic liquid provided by the present invention with other ionic liquids cannot achieve the technical effects 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 N-methyldiethanolamine can improve the selectivity and acid gas load when capturing carbon dioxide and reduce energy consumption. By comparing Example 1 with Comparative Examples 9 and 10, it can be seen that the volume concentration of alcohol in the alcohol aqueous solution of the solvent has a significant effect on the acid gas load, the carbon dioxide content of the tail gas and the regeneration temperature.

[0113] 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 the component A is an imidazole modified amino acid ionic liquid, the cation of the ionic liquid is an imidazole cation, and the imidazole cation has a structure shown in formula (I); the anion of the ionic liquid is selected from sarcosine, lysine, valine or alanine; the component B is selected from aminoethylethanolamine, triethanolamine or N-methyldiethanolamine; the solvent is an alcohol aqueous solution, and the volume concentration of the alcohol in the alcohol aqueous solution is 5-15%; Wherein, R1, R2, R3, R4 and R5 are each independently hydrogen or a C1-C10 straight chain or branched chain alkyl group.

2. The absorbent according to claim 1, wherein R1, R2, R3, R4 and R5 are each independently hydrogen or a C1-C6 straight chain or branched alkyl group; preferably hydrogen or a C1-C4 straight chain or branched alkyl group; more preferably hydrogen, methyl or ethyl.

3. The absorbent according to claim 1 or 2, wherein 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%.

4. The absorbent according to any one of claims 1 to 3, wherein The mass ratio of the component A to the component B is 1:0.8-2.5, preferably 1:1-1.

5.

5. The absorbent according to any one of claims 1 to 4, wherein: Based on the total mass of the absorbent, the A component accounts for 12-15 wt%, preferably 13-14 wt%; the B component accounts for 12-30 wt%, preferably 13-20 wt%.

6. The absorbent according to any one of claims 1 to 5, wherein: The alcohol in the alcohol aqueous solution is selected from one or more of propylene glycol, ethanol and ethylene glycol; Preferably, 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 the component A is an imidazole modified amino acid ionic liquid, the cation of the ionic liquid is an imidazole cation, and the imidazole cation has a structure shown in formula (I); the anion of the ionic liquid is selected from sarcosine, lysine, valine or alanine; the component B is selected from aminoethylethanolamine, triethanolamine or N-methyldiethanolamine; the solvent is an alcohol aqueous solution, and the volume concentration of the alcohol in the alcohol aqueous solution is 5-15%; Wherein, R1, R2, R3, R4 and R5 are each independently hydrogen or a C1-C10 straight chain or branched chain alkyl group.

8. The preparation method according to claim 7, wherein: R1, R2, R3, R4 and R5 are each independently hydrogen or a C1-C6 straight chain or branched alkyl group; preferably hydrogen or a C1-C4 straight chain or branched alkyl group; more preferably hydrogen, methyl or ethyl.

9. The preparation method according to claim 7 or 8, wherein: Based on the total mass of the absorbent, the sum of the component A and the component B is 25-40wt%, preferably 30-35wt%; And / or, the mass ratio of component A to component B is 1:0.8-2.5, preferably 1:1-1.5; And / or, based on the total mass of the absorbent, the A component is 12-15wt%, preferably 13-14wt%; the B component is 12-30wt%, preferably 13-20wt%.

10. The preparation method according to any one of claims 7 to 9, wherein: The alcohol in the alcohol aqueous solution is selected from one or more of propylene glycol, ethanol and ethylene glycol; Preferably, 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 described in any one of claims 1 to 6 or the absorbent prepared by the preparation method described in 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; Preferably, the regeneration temperature is 60-120°C.

Images