Viscosity increase resistant ionic liquid as well as preparation method and application thereof

Abstract

The invention relates to an anti-viscosity increase ionic liquid and a preparation method and application thereof, the ionic liquid comprises cations and anions, the structural formula of the cations is [P (R1) (R2) (R3) (L-A)] < + >, wherein R < 1 >, R < 2 > and R < 3 > are independently selected from C1-C18 alkyl groups; l is a linking group; a is a group containing boric acid. The cationic skeleton of the ionic liquid prepared by the invention is covalently connected with a group containing a boric acid group, and a reversible dynamic covalent bond network is constructed on cations, so that the industrial problem that the viscosity is sharply increased due to the formation of a hydrogen bond network after the amine functionalized ionic liquid chemically captures CO2 is solved. According to the ionic liquid disclosed by the invention, the viscosity growth rate of the ionic liquid is inhibited by more than 90% while the high CO2 trapping capacity is maintained, the fluidity and industrial application potential of the ionic liquid are greatly improved, and a brand new solution is provided for realizing a low-energy-consumption and low-cost CO2 trapping technology.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of carbon dioxide capture, and relates to an anti-viscosity-increasing ionic liquid as well as a preparation method and application thereof. BACKGROUND

[0002] With the increasing global concern about climate change, capturing carbon dioxide (CO2) from point sources such as industrial flue gas has become a key technology for reducing greenhouse gas emissions. Among the many CO2 capture technologies, liquid absorption based on amine chemical absorption is of great concern due to its high selectivity and high capture capacity.

[0003] Ionic liquids (ILs), as a kind of salt composed of anions and cations, are in a liquid state near room temperature, and are considered to be an ideal absorbent to replace traditional volatile amine solutions due to their negligible vapor pressure, good thermal stability, and designable structure. In particular, after introducing an amine group into ionic liquids (i.e., amine-functionalized ionic liquids), they can efficiently capture CO2 through chemical reactions. For example, phosphorus-based ionic liquids with amino acid salts as anions, such as trihexyl (tetradecyl) phosphonium glycinate ([P66614][Gly]), have been proven to achieve high-efficiency CO2 chemical absorption with a molar ratio close to 1:1.

[0004] However, the existing amine-functionalized ionic liquids face a common and fatal problem in industrial application: high viscosity and viscosity increase. The viscosity of such ionic liquids is as high as hundreds of mPa•s (hundreds of times that of water) in itself, and after capturing CO2, a large number of rigid hydrogen bond networks are formed between ionic liquid molecules, resulting in a sharp rise in the viscosity of the system by several orders of magnitude, and even changing from a flowable liquid to a gel or solid. For example, it has been reported in the literature (such as the literature published by Goodrich B. F. et al. in Ind. Eng. Chem. Res. 2011, 50, 111-118) that the viscosity of [P66614][Gly] increases by 48 times after absorbing CO2 at 25°C, and the viscosity of [P66614][Ile] with a similar structure increases by 240 times. Such a huge change in viscosity not only greatly hinders gas mass transfer and reduces absorption kinetics rate, but also makes it extremely difficult to pump, transport the saturated ionic liquid in the pipeline and heat exchange in the regeneration tower, thereby resulting in extremely high equipment investment and operating energy consumption.

[0005] To solve this problem, the skilled person has tried various methods, such as adding water or an organic solvent as a diluent, but this would sacrifice the CO2 capture capacity and introduce new separation and volatilization problems; or reducing the viscosity by increasing the temperature, but this is contrary to the low temperature requirement of the capture process, and increases the additional sensible heat and latent heat energy consumption when CO2 is desorbed. Therefore, how to fundamentally solve the problem of dramatic viscosity increase in the chemical capture process while maintaining high CO2 capture capacity is a technical bottleneck that needs to be broken through in the field. SUMMARY

[0006] In view of the deficiencies of the prior art, the purpose of the present application is to provide an anti-viscosity growth ionic liquid and its preparation method and application.

[0007] To achieve this purpose of the present application, the following technical solutions are adopted:

[0008] In a first aspect, the present application provides an anti-viscosity growth ionic liquid, which comprises a cation and an anion.

[0009] The structural formula of the cation is: [P(R1)(R2)(R3)(L-A)] + ;

[0010] Wherein: R1, R2, R3 are independently selected from C1-C18 alkyl;

[0011] L is a linking group;

[0012] A is a boronic acid-containing group.

[0013] The purpose of the present application is to overcome the defects of the prior art and provide a functional ionic liquid which can significantly inhibit the increase of the system viscosity while efficiently capturing CO2, thereby improving its flowability and industrial application potential.

[0014] Preferably, the linking group is selected from C1-C10 alkylene.

[0015] Preferably, the boronic acid-containing group is selected from a phenylboronic acid group, a 4-methylphenylboronic acid group or a naphthylboronic acid group.

[0016] Preferably, the anion is selected from one or more of L-dopa anion, 3,4-dihydroxy-L-phenylglycine anion or caffeic acid anion.

[0017] In a second aspect, the present application provides a preparation method of the anti-viscosity growth ionic liquid according to the first aspect, which comprises:

[0018] (1) mixing and reacting a phosphorus-containing raw material with a raw material containing a boronic acid group to obtain a first intermediate;

[0019] (2) mixing the first intermediate with a salt containing an anion to obtain an anti-viscosity growth ionic liquid.

[0020] Preferably, the molar ratio of the phosphorus-containing raw material to the raw material containing a boronic acid group is 1:(1-1.5).

[0021] The specific point values in (1-1.5) can be selected as 1, 1.1, 1.2, 1.3, 1.4, 1.5, and other specific point values within the above numerical range can be selected, which will not be repeated here.

[0022] Preferably, the temperature of the reaction in step (1) is 60-120°C, and the time is 12-72 h.

[0023] The temperature can be selected as 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, and the time can be selected as 12 h, 15 h, 20 h, 25 h, 30 h, 35 h, 40 h, 45 h, 50 h, 55 h, 60 h, 65 h, 72 h, and other specific point values within the above numerical range can be selected, which will not be repeated here.

[0024] Preferably, the reaction in step (1) is carried out in an organic solvent.

[0025] Preferably, the mass ratio of the phosphorus-containing raw material, the raw material containing a boronic acid group, and the organic solvent is 1:(0.5-2):(2-10).

[0026] The specific point values in (0.5-2) can be selected as 0.5, 0.8, 1, 1.2, 1.5, 1.8, 2, and the specific point values in (2-10) can be selected as 2, 3, 4, 5, 6, 7, 8, 9, 10, and other specific point values within the above numerical range can be selected, which will not be repeated here.

[0027] Preferably, the organic solvent is selected from one or more of acetonitrile, tetrahydrofuran, dimethylformamide, and toluene.

[0028] Preferably, the molar ratio of the first intermediate to the salt containing an anion in step (2) is 1:(1-1.2).

[0029] The specific point values in (1-1.2) can be selected as 1, 1.02, 1.05, 1.08, 1.1, 1.12, 1.15, 1.18, 1.2, and other specific point values within the above numerical range can be selected, which will not be repeated here.

[0030] Preferably, the temperature of the reaction in step (2) is 0-50°C, and the time is 6-36 h.

[0031] Temperatures can be selected from 0℃, 5℃, 10℃, 15℃, 20℃, 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, etc., and time can be selected from 6 h, 10 h, 15 h, 20 h, 25 h, 30 h, 36 h, etc. Other specific point values ​​within the above range can be selected, which will not be elaborated here.

[0032] Preferably, the reaction in step (2) is carried out under conditions of a polar solvent.

[0033] Preferably, the mass ratio of the first intermediate, the anionic salt, and the polar solvent is 1:(0.2-1):(2-10).

[0034] The specific point values ​​in (0.2-1) can be selected from 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, etc., and the specific point values ​​in (2-10) can be selected from 2, 3, 4, 5, 6, 7, 8, 9, 10, etc. Other specific point values ​​within the above range can be selected, which will not be elaborated here.

[0035] Preferably, the polar solvent is selected from one or more of methanol, ethanol, isopropanol, acetone, and water.

[0036] Thirdly, the present invention provides a CO2 absorption composition comprising the anti-viscosity-growth ionic liquid described in the first aspect.

[0037] Preferably, the mass percentage of the anti-viscosity-growth ionic liquid in the composition is 50-99%, such as 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 99%, etc. Other specific values ​​within the above range can be selected, and will not be elaborated here.

[0038] Preferably, the composition further includes any one or a combination of at least two of water, ethylene glycol, polyethylene glycol, and N-methylpyrrolidone.

[0039] Fourthly, the present invention provides the use of the anti-viscosity-growth ionic liquid according to the first aspect or the CO2 absorption composition according to the third aspect in capturing carbon dioxide from a gas mixture.

[0040] Fifthly, the present invention provides the use of the anti-viscosity-growth ionic liquid according to the first aspect or the CO2 absorption composition according to the third aspect in the catalytic conversion of CO2 into cyclic carbonates.

[0041] Preferably, the cyclic carbonate is a cyclic propylene carbonate.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] 1. Unexpected Anti-Viscosity Growth Effect: Conventional knowledge in the art holds that introducing functional groups capable of forming intermolecular chemical bonds (such as esterification) into a molecule typically increases the degree of cross-linking, leading to a further increase in viscosity. However, this invention surprisingly discovers that after covalently integrating group A, capable of forming dynamic borate ester bonds intermolecularly, into the ionic liquid cation, the viscosity of the system during CO2 capture not only does not increase dramatically due to the formation of a "chemical cross-linking network" as expected, but is instead greatly suppressed. Compared to classic amine-functionalized ionic liquids, at a similar CO2 saturation absorption capacity, the viscosity growth rate of the ionic liquid of this invention is reduced by more than 90%, maintaining excellent fluidity throughout. This counterintuitive positive effect, which cannot be directly predicted by existing theory, fully demonstrates the non-obviousness of this invention.

[0044] 2. Maintaining high CO2 capture capacity: The ionic liquid of the present invention can solve the viscosity problem while maintaining a high CO2 absorption capacity comparable to that of high-efficiency amine-functionalized ionic liquids in the prior art through the functional groups such as amine groups integrated on the anions.

[0045] 3. Significantly improved process performance: Since the system retains low viscosity and good fluidity after capturing CO2, it greatly reduces the operational difficulty and energy consumption of pumping, heat transfer and other units in industrial processes. This helps to reduce equipment size, thereby reducing equipment investment and operating costs, and clearing a key obstacle for the large-scale application of amine functionalized ionic liquids.

[0046] 4. Integrated catalytic function: The ionic liquid provided by this invention can itself serve as a highly efficient catalyst for in-situ catalytic conversion of captured CO2 into high-value-added chemicals (such as cyclic carbonates), thus achieving the integration of CO2 capture and conversion and simplifying the process flow. Attached Figure Description

[0047] Figure 1 This is a schematic diagram of the chemical structure of the ionic liquid IL-1 prepared in Example 1 of the present invention.

[0048] Figure 2 This is a comparison graph showing the viscosity changes of different ionic liquids during CO2 absorption.

[0049] Figure 3 A comparison chart of CO2 absorption capacities of different ionic liquids. Detailed Implementation

[0050] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0051] Example 1

[0052] This embodiment provides a method for preparing an ionic liquid, the method comprising:

[0053] (1) Synthesis of intermediate 1: Under nitrogen protection, trihexylphosphine (143.5 g, 0.5 mol), 1,6-dibromohexane (366 g, 1.5 mol), and 500 mL of acetonitrile were added to a 1 L three-necked flask. The mixture was heated to reflux for 48 hours. After the reaction was completed, the mixture was cooled to room temperature, and the solvent and excess 1,6-dibromohexane were removed by rotary evaporation to obtain a viscous liquid. The liquid was washed three times with diethyl ether and dried under vacuum to obtain intermediate (6-bromohexyl)trihexylphosphine bromide in 92% yield.

[0054] (2) Synthesis of intermediate 2: Under nitrogen protection, 4-hydroxyphenylboronic acid (69 g, 0.5 mol), sodium hydroxide (40 g, 1.0 mol), and 500 mL of anhydrous ethanol were added to another dry 1 L three-necked flask and stirred at room temperature for 30 minutes. Then, intermediate 1 (260 g, 0.5 mol) obtained in step (1) was dissolved in 200 mL of acetonitrile and slowly added dropwise to the above reaction system. The reaction was heated under reflux for 48 hours. After the reaction was completed, the inorganic salts were removed by cooling and filtration. The solvent was removed by rotary evaporation of the filtrate to obtain a viscous crude product. The crude product was dissolved in 500 mL of dichloromethane and then washed twice (200 mL each time) with 1 M dilute hydrochloric acid aqueous solution to neutralize the residual base in the system and convert the borate anion into a neutral borate group, and then washed once with saturated brine. After separation, the organic phase was dried over anhydrous sodium sulfate, filtered, and the solvent was removed by rotary evaporation to obtain a bromide salt with the cationic part being [(6-(4-boronicophenoxy)hexyl)trihexylphosphine] cation. The bromide was a pale yellow oily liquid with a yield of 85%.

[0055] (3) Preparation of ionic liquid IL-1: Intermediate 2 (350 g, 0.4 mol) obtained in step (2) was dissolved in 500 mL of ethanol. In another flask, L-DOPA (L-3,4-dihydroxyphenylalanine) (79 g, 0.4 mol) was dissolved in an equimolar amount of potassium hydroxide ethanol solution. The two were mixed and stirred at room temperature for 24 hours. The generated KBr was removed by filtration. The ethanol was removed by rotary evaporation of the filtrate to obtain the crude product. The crude product was dissolved in dichloromethane, washed three times with water, separated, and the organic phase was dried over anhydrous sodium sulfate and the solvent was removed by rotary evaporation. Finally, the product was dried under vacuum at 80 °C for 48 hours to obtain the target product IL-1, whose cation is [(6-(4-boronicophenoxy)hexyl)trihexylphosphine] cation and anion is L-DOPA anion.

[0056] Example 2

[0057] This embodiment provides a method for preparing an ionic liquid, which differs from Example 1 only in that step (3) is: "Preparation of ionic liquid IL-C1: Dissolve intermediate 2 (350g, 0.4mol) obtained in step (2) in 500mL of ethanol. In another flask, dissolve glycine (0.4mol) in an equimolar amount of potassium hydroxide ethanol solution. Mix the two and stir the reaction at room temperature for 24 hours. Filter to remove the generated KBr. Rotary evaporate the filtrate to remove ethanol, and obtain the crude product. Dissolve the crude product in dichloromethane, wash three times with water, separate the liquids, dry the organic phase with anhydrous sodium sulfate, and then rotary evaporate to remove the solvent. Finally, vacuum dry at 80°C for 48 hours to obtain the target product IL-C1", with other operations remaining unchanged.

[0058] Example 3

[0059] This embodiment provides a method for preparing an ionic liquid, which is prepared according to the method disclosed in the literature (Gurkan BE, de la Fuente JC, Mindrup EM, Ficke LE, Goodrich BF, Price EA, Schneider WF, Brennecke JF Equimolar CO2 Absorption by Anion-Functionalized Ionic Liquids Journal of the American Chemical Society, 2010, 132(7), 2116–2117 DOI: 10.1021 / ja909305t) to obtain the target product IL-C2.

[0060] Example 4

[0061] This embodiment provides a method for preparing an ionic liquid, the method comprising:

[0062] Using IL-C2 as the host ionic liquid, two small molecule additives, 4-methoxyphenylboronic acid (as an analog of the "boric acid arm") and 3,4-dihydroxybenzoic acid (as an analog of the "diol arm"), with molar numbers equivalent to those in Example 1, were added to it. The mixture was magnetically stirred at 60°C for 4 hours to ensure complete dissolution and uniform mixing of the additives, resulting in the physically mixed system IL-C3.

[0063] Example 5

[0064] Expansion of cation structure

[0065] This embodiment provides a method for preparing an ionic liquid, the method comprising:

[0066] (1) Synthesis of intermediate 3: Under nitrogen protection, tributylphosphine (101.2 g, 0.5 mol), 1,3-dibromopropane (302.9 g, 1.5 mol), and 400 mL of acetonitrile were added to a three-necked flask. The mixture was heated to 85 °C and refluxed for 48 hours. After the reaction was completed, the mixture was cooled to room temperature, and the solvent and excess 1,3-dibromopropane were removed by rotary evaporation to obtain a yellow viscous liquid. After washing three times with diethyl ether, the liquid was dried under vacuum for 24 hours to obtain (3-bromopropyl)tributylphosphine bromide (intermediate 3) in 90% yield.

[0067] (2) Synthesis of intermediate 4: Under nitrogen protection, 4-hydroxymethylphenylboronic acid (68.4 g, 0.45 mol), sodium hydroxide (36.0 g, 0.9 mol), and 500 mL of anhydrous tetrahydrofuran were added to a dry three-necked flask and magnetically stirred at room temperature for 1 hour. Then, intermediate 3 (202.5 g, 0.45 mol) obtained in step (1) was dissolved in 200 mL of acetonitrile and slowly added dropwise to the above reaction system. After the addition was complete, the system was heated to 70 °C and refluxed for 48 hours.

[0068] After the reaction was complete, the mixture was cooled to room temperature and filtered to remove the inorganic salts. The solvent was removed by rotary evaporation of the filtrate, yielding a viscous crude product. The crude product was dissolved in 500 mL of dichloromethane, then washed twice with 1M dilute hydrochloric acid, followed by one wash with saturated sodium chloride aqueous solution. The organic phase was dried over anhydrous sodium sulfate. Dichloromethane was removed by rotary evaporation to give the bromide salt of the [(3-(4-boronobenzoxy)propyl)tributylphosphine] cation (intermediate 4) in 82% yield.

[0069] (3) Preparation of ionic liquid IL-2 (cationic extended example): Intermediate 4 (234.9 g, 0.4 mol) obtained in step (2) was dissolved in ethanol. In another flask, L-DOPA (79 g, 0.4 mol) was dissolved in an equimolar amount of potassium hydroxide ethanol solution. The two solutions were mixed and reacted magnetically at 25 °C for 24 hours. After the reaction was completed, the generated KBr was removed by filtration, and the ethanol was removed by rotary evaporation of the filtrate to obtain the crude product. The crude product was redissolved in dichloromethane, washed three times with deionized water, and the organic phase was dried with anhydrous sodium sulfate. The dichloromethane was removed by rotary evaporation, and the product was dried under vacuum for 48 hours to obtain another ionic liquid IL-2 conforming to the general formula of this invention, with a yield of 89%.

[0070] Tests have shown that it also exhibits high CO2 absorption capacity and excellent resistance to viscosity growth.

[0071] Example 6

[0072] Expansion of anion structure

[0073] This embodiment provides a method for preparing an ionic liquid, which differs from Example 1 only in that step (3) is: "The intermediate 2 (350g, 0.4mol) obtained in step (2) is dissolved in 500mL of ethanol. In another flask, 3,4-dihydroxy-L-phenylglycine (0.4mol) is dissolved in an equimolar amount of potassium hydroxide ethanol solution. The two are mixed and stirred at room temperature for 24 hours. The generated KBr is removed by filtration. The ethanol in the filtrate is removed by rotary evaporation to obtain the crude product. The crude product is dissolved in dichloromethane, washed three times with water, separated, and the organic phase is dried over anhydrous sodium sulfate and the solvent is removed by rotary evaporation. Finally, it is dried under vacuum at 80°C for 48 hours to obtain the target product IL-3". All other operations remain unchanged.

[0074] Example 7

[0075] This embodiment provides a method for preparing an ionic liquid, which differs from Example 1 only in that step (3) is: "Preparation of ionic liquid IL-4: Dissolve intermediate 2 (350g, 0.4mol) obtained in step (2) in 500mL of ethanol. In another flask, dissolve caffeic acid (3-(3,4-dihydroxyphenyl)-2-acrylic acid (0.4mol)) in an equimolar amount of potassium hydroxide ethanol solution. Mix the two and stir the reaction at room temperature for 24 hours. Filter to remove the generated KBr. Rotary evaporate the filtrate to remove ethanol, and obtain the crude product. Dissolve the crude product in dichloromethane, wash three times with water, separate the liquids, dry the organic phase with anhydrous sodium sulfate, and then rotary evaporate to remove the solvent. Finally, vacuum dry at 80°C for 48 hours to obtain the target product IL-4", with other operations remaining unchanged.

[0076] Test Example 1

[0077] The ionic liquid IL-1 prepared in Example 1, the ionic liquid IL-C1 prepared in Example 2, the ionic liquid IL-C2 prepared in Example 3 according to the prior art, the physical mixing system IL-C3 prepared in Example 4, and the ionic liquids IL-2 / IL-3 / IL-4 prepared in Examples 5-7 were subjected to CO2 absorption and viscosity tests, respectively.

[0078] Test conditions: 10.0 g of each ionic liquid sample was placed in a thermostatically controlled magnetically stirred reactor. Pure CO2 gas was introduced at a flow rate of 50 mL / min at 30 °C for absorption until saturation. The viscosity before and after absorption was measured using a rotational viscometer at 30 °C. The test results are summarized in Table 1 below. Figure 2 , Figure 3 .

[0079] Table 1

[0080]

[0081] (1) The ionic liquid IL-1 provided by the present invention (Example 1) has a CO2 saturation absorption capacity of up to 1.18 mol / mol, which is basically the same as the efficient IL-C2 (1.26 mol / mol) in the prior art, proving that the structural modification of the present invention has not sacrificed its high capture capacity advantage.

[0082] (2) Most importantly, after absorbing CO2, the viscosity of IL-C2 increases dramatically from 410 mPa·s to 19680 mPa·s, an increase of 48 times, making the system extremely viscous and difficult to flow. This is completely consistent with the defects of the prior art described in the background section.

[0083] (3) In stark contrast, the viscosity of IL-1 of the present invention, after absorbing an equal amount of CO2, only increased slightly from 525 mPa·s to 1030 mPa·s, an increase of less than 2 times. Compared with IL-C2, its viscosity growth was suppressed by more than 96%. This fully demonstrates that the present invention has an unexpected and groundbreaking technical effect in suppressing viscosity growth.

[0084] (4) Comparing the results of IL-C2 (cation lacking borate arm) and IL-C3 (physical mixing), neither the lack of functional arm nor simple physical mixing can effectively suppress the increase in viscosity. This conversely proves that the beneficial effects of the present invention must rely on the synergistic effect of the borate group covalently bonded to the cation and the diol group on the anion, which is necessary and non-obvious for achieving its unexpected technical effects.

[0085] Test Example 2

[0086] Catalytic reaction of CO2 with propylene oxide

[0087] In a 100 mL high-pressure reactor, 2.0 g of the ionic liquid IL-1 prepared in Example 1 was added as a catalyst, along with 14.5 g (0.25 mol) of propylene oxide. The reactor was sealed, and the air inside was replaced three times with CO2, after which CO2 was introduced to a pressure of 2.0 MPa. The reactor was placed in an oil bath at 100 °C and the reaction was carried out with magnetic stirring for 2.5 hours. After the reaction was completed, the reactor was cooled to room temperature, and the pressure was slowly released. The reaction solution was analyzed by gas chromatography (GC).

[0088] The results showed that the conversion rate of propylene oxide was 96.2%, and the selectivity of the product cyclic propylene carbonate (PC) was 98.5%. Due to the low viscosity of the system after the reaction, the product PC could be easily separated by vacuum distillation (85℃, 1kPa). The catalyst could be recovered and directly used in the next reaction. After five cycles, the catalytic activity did not decrease significantly.

[0089] The applicant declares that this invention illustrates an anti-viscosity-growth ionic liquid, its preparation method, and its application through the above embodiments. However, this invention is not limited to the above embodiments, meaning that this invention does not necessarily rely on the above embodiments for implementation. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of raw materials, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection and disclosure scope of this invention.

[0090] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0091] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

Claims

1. An ionic liquid with resistance to viscosity growth, characterized in that, The ionic liquid includes cations and anions; The structural formula of the cation is: [P(R1)(R2)(R3)(LA)] + ; Wherein: R1, R2, and R3 are independently selected from C1-C18 alkyl groups; L is the linker base; A is a boric acid-containing group.

2. The anti-viscosity-growth ionic liquid according to claim 1, characterized in that, The linker group is selected from C1-C10 alkylene groups.

3. The anti-viscosity-growth ionic liquid according to claim 1 or 2, characterized in that, The boric acid-containing group is selected from phenylboronic acid group, 4-methylphenylboronic acid group or naphthaleneboronic acid group; Preferably, the anion is selected from one or more of L-DOPA anion, 3,4-dihydroxy-L-phenylglycine anion, or caffeic acid anion.

4. The method for preparing the anti-viscosity-growth ionic liquid according to any one of claims 1-3, characterized in that, The preparation method includes: (1) The phosphorus-containing raw material is mixed and reacted with the raw material containing boric acid groups to obtain the first intermediate; (2) The first intermediate is mixed with a salt containing anion to react and obtain an ionic liquid that resists viscosity growth.

5. The method for preparing the anti-viscosity-growth ionic liquid according to claim 4, characterized in that, The molar ratio of the phosphorus-containing raw material to the raw material containing boric acid groups is 1:(1-1.5); Preferably, the reaction in step (1) is carried out at a temperature of 60-120°C for 12-72 h. Preferably, the reaction in step (1) is carried out under conditions of an organic solvent; Preferably, in step (2), the molar ratio of the first intermediate to the salt containing the anion is 1:(1-1.2); Preferably, the reaction temperature in step (2) is 0-50℃ and the reaction time is 6-36 h; Preferably, the reaction in step (2) is carried out under conditions of a polar solvent.

6. A CO2 absorption composition, characterized in that, The composition contains an anti-viscosity-growth ionic liquid as described in any one of claims 1-3.

7. The CO2 absorption composition according to claim 6, characterized in that, The composition contains 50-99% by mass of an anti-viscosity-growth ionic liquid. Preferably, the composition further includes any one or a combination of at least two of water, ethylene glycol, polyethylene glycol, and N-methylpyrrolidone.

8. The use of the anti-viscosity-growth ionic liquid according to any one of claims 1-3 or the CO2 absorption composition according to claim 6 or 7 in capturing carbon dioxide from a gas mixture.

9. The use of the anti-viscosity-growth ionic liquid according to any one of claims 1-3 or the CO2 absorption composition according to claim 6 or 7 in the catalytic conversion of CO2 to cyclic carbonates.

10. The application according to claim 9, characterized in that, The cyclic carbonate is cyclic propylene carbonate.

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