Carbon dioxide absorbent as well as preparation method and application thereof

Abstract

The invention relates to the technical field of carbon dioxide trapping, and discloses a carbon dioxide absorbent as well as a preparation method and application thereof. The absorbent comprises a component A, a component B and a solvent, wherein the component A is imidazole improved amino acid ionic liquid, cations of the ionic liquid are imidazole cations, the imidazole cations contain ether oxygen groups and / or amino groups, and the ether oxygen groups and / or amino groups are directly connected with N atoms on imidazole rings; anions of the ionic liquid are selected from sarcosine, lysine, valine or alanine; and the component B is selected from amino ethyl ethanolamine, triethanolamine or methyldiethanolamine. The carbon dioxide absorbent can be applied to carbon dioxide trapping, selectivity and acid gas load during carbon dioxide trapping can be improved, and energy consumption can be reduced.

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 the main cause of global warming. Traditional atmospheric pressure CO2 separation processes generally remove CO2 through low-temperature absorption and high-temperature desorption, or recover part of the heat through heat pumps, mechanical vapor recompression, etc., to achieve energy saving and consumption reduction.

[0005] At present, there are many mature process methods for separating CO2 from gas mixtures, such as chemical absorption, physical absorption, adsorption, membrane separation, etc., and they all have their own scope of use. Among these methods, chemical absorption is currently the most widely used method. In the chemical absorption carbon capture technology, the performance of the chemical absorbent determines the CO2 capture effect and the energy consumption of the system. In traditional chemical absorption, hot potassium alkali solution, ammonia water, and alcohol amine solution are often used as absorbents in the carbon capture process. They have a good effect on capturing CO2 and the technology is relatively mature. However, due to the high energy consumption of chemical absorption, the absorbent has poor antioxidant properties, is easy to degrade and deteriorate, and is highly corrosive. Decarbonization absorbents are mixed amines or formula absorbents mainly composed of monoethanolamine (MEA), diethanolamine (DEA), and N-methyldiethanolamine (MDEA). MEA and DEA are primary and secondary amines, with strong alkalinity, fast reaction speed with CO2, and good absorption speed. They are often used when the partial pressure of CO2 in the mixed gas is lower than 0.2MPa. However, due to the strong corrosiveness of MEA and DEA, the concentration used is generally 15%-25%, the acid gas load is small, and the solution circulation volume required to remove a large amount of CO2 is large, resulting in high regeneration heat consumption and power energy consumption. When the partial pressure of CO2 is higher than 0.2MPa, various formula absorbents mainly based on MDEA are mostly used. Traditional formula absorbents also have the contradiction between decarbonization purification degree and processing load. Summary of the invention

[0006] The purpose of the present invention is to overcome the problems of high loss, high energy consumption, strong corrosiveness, etc. in the prior art 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 includes 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 ether oxygen group and / or an amino group, and the ether oxygen group and / or the amino group are directly connected to the N atom on the imidazole ring; the anion of the ionic liquid is selected from sarcosine, lysine, valine or alanine; the component B is selected from aminoethylethanolamine, triethanolamine or methyldiethanolamine.

[0008] The second aspect of the present invention provides a method for preparing a carbon dioxide absorbent, the preparation method comprising: mixing component A, component B and a solvent 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, the imidazole cation contains an ether oxygen group and / or an amino group, and the ether oxygen group and / or the 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; 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: using the aforementioned absorbent to capture carbon dioxide.

[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, loss, etc. of the absorbent used to capture carbon dioxide are greatly reduced, while the capture capacity and stability are greatly improved. DETAILED DESCRIPTION

[0014] The endpoints and any values ​​of the ranges disclosed in this article 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 endpoint values ​​of each range, the endpoint values ​​of each range and the 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 as specifically disclosed in this article.

[0015] The first aspect of the present invention provides a carbon dioxide absorbent, which includes 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 ether oxygen group and / or an amino group, and the ether oxygen group and / or the amino group are directly connected to the N atom on the imidazole ring; the anion of the ionic liquid is selected from sarcosine, lysine, valine or alanine; the component B is selected from aminoethylethanolamine, triethanolamine or methyldiethanolamine.

[0016] The present invention utilizes the various excellent properties of ionic liquids, such as extremely low vapor pressure, high thermal stability, strong solubility, stable properties, non-flammability, low corrosivity, etc., selects ionic liquids with imidazole cations as cations and sarcosine, lysine, valine or alanine as anions, and compounding them with aminoethylethanolamine, triethanolamine or methyldiethanolamine as absorbents 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, large solvent loss, etc. existing 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] Wherein, the molecular formula of 3-etheroxy-1-methylimidazolium cation is shown in formula (1):

[0020]

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

[0022]

[0023] The molecular formula of 1,3-aminoimidazole 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, 1,3-aminoimidazole alanine ionic liquid.

[0028] In some specific embodiments, the preparation method of the ionic liquid is as follows: accurately weigh the ionic liquid raw materials R1-imidazole (R1 is selected from amino or methyl) and R2-Br (R2 is selected from amino or ether oxygen), wherein the molar ratio of R1-imidazole to R2-Br is 1:1, and dissolve in anhydrous ethanol at room temperature, place 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 15-25°C under N2 protection. After the reaction is completed, use a rotary evaporator to remove ethanol under reduced pressure at 38-42°C, and the residue is dissolved in deionized water. Add KOH solid in 10 batches under stirring, and the reaction system releases heat. After all KOH is added, continue to stir the reaction for 60-62 minutes, use a rotary evaporator to remove water under reduced pressure at 60-65°C, extract imidazole bromide with ethanol-tetrahydrofuran, and remove ethanol-tetrahydrofuran under reduced pressure. The product after reduced pressure distillation is mixed with 2-2.2 times the volume of ethanol-water, 1.1-1.15 times the mole of amino acid (sarcosine, lysine, valine or alanine) is added, heated at 30-35° C. for 24-24.5 hours, taken out and cooled to room temperature, filtered, 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 numerical 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] The second aspect of the present invention provides a method for preparing a carbon dioxide absorbent, which comprises: mixing component A, component B and a solvent 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, the imidazole cation contains an ether oxygen group and / or an amino group, and the ether oxygen group and / or the amino group are 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 an ionic liquid and an ethanolamine composite solvent. Compared with a traditional carbon dioxide absorbent, the absorbent obtained by the method of the present invention has a larger 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 A component accounts for 12-15 wt%, preferably 13-14 wt%; the B component 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 in a high-pressure gas source. Compared with a conventional high-pressure gas source carbon dioxide absorbent, 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 can effectively overcome the problems of low selectivity, low acid gas load, and high solvent loss in conventional CO2 capture methods in high-pressure gas sources, and can improve the selectivity and acid gas load when capturing carbon dioxide in a high-pressure gas source, and reduce energy consumption.

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

[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 consisting 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 solution of the absorbent to form a rich liquid; then heating and regenerating the rich liquid absorbed with carbon dioxide to produce a carbon dioxide product and a lean liquid, and then circulating and absorbing the lean liquid.

[0054] The present invention is described in detail below by way of examples, but the protection scope of the present invention is not limited to the following description. In the following examples and comparative examples, if no specific conditions are specified, the conditions are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used, if the manufacturer is not specified, are all conventional products that can be obtained through commercial channels.

[0055] In the following examples and comparative examples,

[0056] The lean liquid acid gas load is measured by the 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 raw gas remain unchanged, the higher the acid gas load, the better the selectivity.

[0059] Example 1

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

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

[0062] (1) Preparation of 3-Etheroxy-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 releases heat. After all KOH is added, continue stirring the reaction for 60 minutes, use a rotary evaporator to remove water under reduced pressure at 60°C, extract imidazole bromide with ethanol-tetrahydrofuran, and remove 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, cooled to room temperature, filtered, and 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-methylimidazole lysine ionic liquid;

[0063] (2) First, MDEA and a 10 vol% ethanol aqueous solution are mixed to form a mixed solution; and then the 3-etheroxy-1-methylimidazolium lysine ionic liquid obtained in step (1) is 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 0.5MPa, room temperature, the volume content of CO2 in the gas source is 13.0%, and the rest is N2.

[0065] Capturing carbon dioxide: 200 mL of absorbent was placed in an absorption bottle, magnetically stirred, and the absorption temperature was controlled at 40°C. Then the gas was slowly introduced, and the gas flow rate was controlled at 250 mL / min. 1 mL of absorbent was taken at regular intervals and analyzed using a carbon dioxide generator until the molar content of carbon dioxide in the absorbent remained unchanged. After testing, the time to finally reach absorption equilibrium was 45 minutes, and the absorbed carbon dioxide was 1.5 mol CO2 / mol solvent. The absorbent was then regenerated at 65°C, and the regeneration rate reached 61.2%. The results are shown in Table 1.

[0066] Embodiment 2-7

[0067] The absorbent was prepared according to the method of Example 1, except that the contents of the 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 a 3-etheroxy-1-methylimidazolium cation, and the anion was an alanine anion. The results are shown in Table 1.

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

[0071] Accurately weigh equimolar 3-methylimidazole and ether oxybromide, 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 the residue is dissolved in deionized water. Add KOH solid in 10 batches under stirring, and the reaction system releases heat. After all KOH is added, continue to stir and react for 60 minutes, use a rotary evaporator to remove water under reduced pressure at 60°C, extract imidazole bromide with ethanol-tetrahydrofuran, and remove ethanol-tetrahydrofuran under reduced pressure. The product after reduced pressure distillation is mixed with 2 times the volume of ethanol-water, add 1.1 times the mole of alanine, heat at 30°C for 24 hours, take out and cool to room temperature, filter, evaporate the filtrate to dryness, extract with anhydrous ethanol, and filter again. The filtrate obtained is rotary evaporated to remove ethanol to obtain 3-ether oxy-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] Wherein, the preparation method of 3-etheroxy-1-aminoimidazole sarcosine ionic liquid comprises the following steps:

[0075] Accurately weigh equimolar 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 reaction under N2 protection and at room temperature. After the reaction is completed, use a rotary evaporator to remove ethanol under reduced pressure at 40°C, and the residue is dissolved in deionized water. Add KOH solid in 10 batches under stirring, and the reaction system releases heat. After all KOH is added, continue to stir and react for 60 minutes, use a rotary evaporator to remove water under reduced pressure at 60°C, extract imidazole bromide with ethanol-tetrahydrofuran, and remove ethanol-tetrahydrofuran under reduced pressure. The product after reduced pressure distillation is mixed with 2 times the volume of ethanol-water, add 1.1 times the mole of sarcosine, heat at 30°C for 24 hours, take out and cool to room temperature, filter, evaporate the filtrate to dryness, extract with anhydrous ethanol, and filter again. The filtrate obtained is rotary evaporated to remove ethanol to obtain 3-etheroxy-1-aminoimidazole sarcosine ionic liquid.

[0076] Example 10

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

[0078] Embodiment 11

[0079] The absorbent was prepared according to the method of Example 1, except that the cation of the ionic liquid was a 1,3-aminoimidazole cation and the anion was a 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 3-aminoimidazole and aminobromide, 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 under N2 protection and at room temperature. After the reaction is completed, use a rotary evaporator to remove ethanol under reduced pressure at 40°C, and the residue is dissolved in deionized water. Add KOH solid in 10 batches under stirring, and the reaction system releases heat. After all KOH is added, continue to stir and react for 60 minutes, use a rotary evaporator to remove water under reduced pressure at 60°C, extract imidazole bromide with ethanol-tetrahydrofuran, and remove ethanol-tetrahydrofuran under reduced pressure. The product after reduced pressure distillation is mixed with 2 times the volume of ethanol-water, add 1.1 times the mole of valine, heat at 30°C for 24 hours, take out and cool to room temperature, filter, evaporate the filtrate to dryness, extract with anhydrous ethanol, and filter again. The filtrate is rotary evaporated to remove ethanol to obtain 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 by a 1 vol% ethanol aqueous solution. The results are shown in Table 1.

[0086] Embodiment 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] The absorbent was prepared according to the method of Example 1, except that the ionic liquid was replaced by a bisaminoimidazole ionic liquid. The CO2 absorption amount was 1.13 mol CO2 / mol solvent. The results are shown in Table 1.

[0094] Comparative Example 4

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

[0096] Table 1

[0097]

[0098] It can be seen from the results of Table 1 that, relative to the absorbents of Comparative Examples 1-4, the absorbents of Examples 1-14 of the present invention have higher acid gas loads, lower tail gas carbon dioxide content and 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 ionic liquid, and Comparative Example 2 does not contain N-methyldiethanolamine. It can be seen from the result data 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 and 4, it can be seen that replacing the ionic liquid provided by the present invention with other ionic liquids also 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 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 are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope 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, the imidazole cation contains an ether oxygen group and / or an amino group, and the ether oxygen group and / or the amino group are directly connected to the N 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.

2. The absorbent according to claim 1, wherein The imidazolium cation is selected from 3-etheroxy-1-methylimidazolium cation, 3-etheroxy-1-aminoimidazolium cation or 1,3-aminoimidazolium cation; And / or, the amino acid anion is selected from sarcosine anion, lysine anion, valine anion or alanine anion.

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 solvent is water or an alcohol aqueous solution; Preferably, the alcohol in the alcohol aqueous solution is selected from one or more of propylene glycol, ethanol and ethylene glycol; Preferably, 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%.

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, the imidazole cation contains an ether oxygen group and / or an amino group, and the ether oxygen group and / or the amino group are 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.

8. The preparation method according to claim 7, wherein: The imidazolium cation is selected from 3-etheroxy-1-methylimidazolium cation, 3-etheroxy-1-aminoimidazolium cation or 1,3-aminoimidazolium cation; And / or, the amino acid anion is selected from sarcosine anion, lysine anion, valine anion or alanine anion.

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 solvent is water or an alcohol aqueous solution; Preferably, the alcohol in the alcohol aqueous solution is selected from one or more of propylene glycol, ethanol and ethylene glycol; Preferably, 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%.

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.

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