Preparation method of high-purity imidazole ionic liquid

Abstract

This invention provides a method for preparing high-purity imidazole ionic liquids, comprising the following steps: S1: 1-Ethyl-3-methylimidazolium chloride, sodium trifluoromethanesulfonate or sodium bis(trifluoromethanesulfonyl)imide, and glycerol solvent are added sequentially to a reactor, followed by stirring and reaction; S2: After the reaction is completed, stirring is turned off, and the resulting crude 1-ethyl-3-methylimidazolium ionic liquid and glycerol mixture are filtered and collected in a separator, with sodium chloride retained in the reactor and subsequently discharged; S3: Pure water is added to the separator, and the separator is stirred for a certain period of time before settling and separation; S4: The two phases in the separator are separated by a separator and then enter their respective purification devices; S5: The crude 1-ethyl-3-methylimidazolium ionic liquid is dehydrated by vacuum distillation to obtain the product; S6: The water and glycerol mixture is distilled under reduced pressure to obtain a reusable aqueous phase and a glycerol phase. This invention yields a product with a purity of over 99.5%; the solvents glycerol and water are reused after distillation. This method is simple, has a yield of over 94%, and is easy to implement in large-scale production.

Description

Technical Field

[0001] This invention belongs to the field of ionic liquid preparation technology, specifically relating to a method for preparing high-purity imidazole ionic liquids. Background Technology

[0002] 1-Ethyl-3-methylimidazolium ionic liquids are a type of ionic liquid with surface-active properties, making them suitable as electrolyte additives. Furthermore, due to their low volatility and high solubility, they can be used as green solvents. In recent years, the ionic liquid industry has experienced rapid growth, and 1-ethyl-3-methylimidazolium ionic liquids, as products with superior properties, have attracted widespread attention.

[0003] The following are the published patents related to imidazole ionic liquids: CN110396187B discloses a method for preparing imidazole-based ionic liquids. The method involves reacting terminally hydroxyl-terminated polyepoxychloropropane with alkyl imidazoles containing different chain lengths to prepare imidazole-based ionic liquids with chloride ions in the side chains. Then, the polyionic liquid is reacted with a metal salt. By adjusting the amount of metal salt, chloride ions in the polyionic liquid exchange with anions in the metal salt during ion exchange, resulting in an imidazole-based ionic liquid with two different anions in the side chains. Because the raw material epichlorohydrin is a Group 2A carcinogen and this method lacks purification methods, the product prepared by this process has a high impurity content.

[0004] CN114591181B discloses a method for preparing a high-purity ionic liquid, (1) dissolving a compound whose cation is quaternary ammonium ion, quaternary phosphorus ion, imidazole ion or imidazole ion, etc., in an organic solvent to form an organic phase, and dissolving the compound whose anion is [BF4] in an organic solvent to form an organic phase. - [PF6] - [CF3SO3] - Or [Tf2N] - The compounds are dissolved in water to form an aqueous phase; wherein the molar ratio of the anionic compound to the cationic compound is greater than or equal to 1; (2) the organic phase and the aqueous phase are mixed and stirred to allow the two phases to come into full contact and react; (3) the ionic liquid is obtained by separation through a modified polyimide nanofiltration membrane. This method generates a large amount of wastewater and has poor dissolution and dispersion effects on the product, resulting in a low conversion rate. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for preparing high-purity 1-ethyl-3-methylimidazolium ionic liquids with simple process and high product purity.

[0006] To achieve the above objectives, the present invention performs the following reaction: CF3SO3Na+(C6H 11N2)Cl→ [C6H 11 [N2][CF3SO3]+NaCl or [(CF3SO2)2N]Na+(C6H 11 N2)Cl→ [C6H 11 N2][(CF3SO2)2N]+NaCl The technical solution of the present invention: A method for preparing a high-purity imidazole ionic liquid includes the following steps: S1: 1-Ethyl-3-methylimidazolium chloride, sodium trifluoromethanesulfonate or sodium bis(trifluoromethanesulfonyl)imide and glycerol solvent are added sequentially into the reactor, and then the reaction is stirred. S2: After the reaction is complete, turn off the stirring. The crude 1-ethyl-3-methylimidazolium ionic liquid and glycerol mixture solution are filtered by a filtration device and collected in a separator. Sodium chloride is retained in the reactor and discharged later. S3: Add pure water to the separator, turn on the separator and stir for a certain period of time, then let it stand. The upper layer is a mixed phase of water and glycerol, and the lower layer is a crude 1-ethyl-3-methylimidazolium ionic liquid phase. S4: The two phases in the separator are separated by the liquid separator and then enter the corresponding purification devices respectively; S5: The crude 1-ethyl-3-methylimidazolium ionic liquid was dehydrated by vacuum distillation to obtain the product; S6: The water and glycerol mixture is distilled under reduced pressure to obtain reusable water and glycerol phases in sequence. Preferably, in S1, the mass ratio of 1-ethyl-3-methylimidazolium chloride: sodium trifluoromethanesulfonate: glycerol is 1:1.1:1.2; and the mass ratio of 1-ethyl-3-methylimidazolium chloride: sodium bis(trifluoromethanesulfonyl)imide: glycerol is 1:2:1.2.

[0007] Preferably, the reaction temperature in S1 is controlled at 30~80℃ and the reaction time is controlled at 3~8h.

[0008] Preferably, the filtration device described in S2 is integrated into the inner wall of the reactor and has an overall barrel-cone structure. The liquid is filtered out from the bottom side of the reactor, and the filter residue is released from the bottom of the reactor.

[0009] Preferably, the filter screen of the filtration device described in S2 is a stainless steel filter screen with a pore size of 200 mesh.

[0010] Preferably, the mass ratio of water added in S3 to the mass ratio of the 1-ethyl-3-methylimidazolium ionic liquid and the glycerol mixed solution is 0.4~0.8:1.

[0011] Preferably, the stirring time in S3 is controlled at 2~5h, and the settling time is controlled at 1~4h.

[0012] Preferably, the separation of the liquid in S4 is performed by observation through a sight glass.

[0013] Preferably, the crude 1-ethyl-3-methylimidazolium ionic liquid in S5 is removed by vacuum distillation, and the main impurity removed is water. The pressure of vacuum distillation is controlled below -0.090 MPa, the temperature is controlled between 60 and 120°C, and the distillation time is controlled between 6 and 10 hours.

[0014] Preferably, the pressure of both water and glycerol in S6 is controlled below -0.095 MPa during vacuum distillation. Water is distilled off first, at which point the temperature of the distillation vessel is 50-80°C. Then, the temperature is slowly increased at a rate of 0.5-2°C / min to distill off glycerol, at which point the temperature of the distillation vessel is controlled at 200-260°C. Heating is stopped once no more glycerol is distilled off.

[0015] Compared with the prior art, the present invention has the following advantages: The process described in this method involves reacting 1-ethyl-3-methylimidazolium chloride with sodium trifluoromethanesulfonate or sodium bis(trifluoromethanesulfonyl)imide in a glycerol solvent under stirring to form a suspension. After the reaction, the crude 1-ethyl-3-methylimidazolium ionic liquid is completely dissolved in the glycerol solvent. Due to the incompatibility between the by-product sodium chloride and the unreacted sodium trifluoromethanesulfonate or sodium bis(trifluoromethanesulfonyl)imide and the glycerol solvent, they can be separated by filtration. The crude 1-ethyl-3-methylimidazolium ionic liquid and glycerol can be separated into layers by adding water. After separation, the product can be obtained by simple distillation and purification, and the solvent can be recovered. The overall process is relatively simple, generates virtually no wastewater, and has a low cost.

[0016] The present invention involves the distillation and reuse of the solvents glycerol and water. This method is simple and easy to implement for large-scale production.

[0017] The yield of this invention is consistently above 94%, and the product purity is consistently above 99.5%. Detailed Implementation

[0018] The present invention will now be described in detail with reference to specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0019] Example 1 This embodiment provides a method for preparing 1-ethyl-3-methylimidazolium ionic liquids, and the operation example is as follows: S1. Open the reactor feed port and add 202g of solid 1-ethyl-3-methylimidazolium chloride and 222.2g of sodium trifluoromethanesulfonate into the reactor, then close the feed port; introduce 242.4g of glycerol into the reactor and start stirring; stir and react at 36℃ for 4.3h, then turn off the stirring. S2. Sequentially open the separator receiving valve and the reactor nitrogen valve to adjust the reactor pressure to 0.049MPa. Then, open the bottom outlet valve on the side of the reactor to transfer the mixed solution of crude 1-ethyl-3-methylimidazolium ionic liquid and glycerol to the filtration device for filtration. The filtration device is integrated on the inner wall of the reactor and has a barrel-cone structure. The filter screen of the filtration device is a stainless steel filter screen with a 200-mesh pore size. Then, it is transferred to the separator. S3. Open the separator inlet valve and control the water addition to 220g. Then turn on the separator agitator and agitate the material for 2.9 hours. After agitation, allow the material to stand for 3.3 hours, then open the discharge valve to separate the liquids. S4. Open the valve at the bottom of the separator leading to the 1-ethyl-3-methylimidazolium ionic liquid distillation vessel. When stratification appears in the sight glass at the bottom of the separator, close the valve and open the valve to the glycerol-water mixture distillation vessel, thus introducing the upper glycerol aqueous solution into the glycerol aqueous solution distillation vessel. S5. Open the vacuum valve of the 1-ethyl-3-methylimidazolium ionic liquid distillation vessel, adjust the vessel pressure to -0.097 MPa, and at the same time turn on the electric heating to adjust the vessel temperature to 92℃. After the S6, 1-ethyl-3-methylimidazolium ionic liquid distillation vessel ran for 6.1 hours, the nitrogen valve on the vessel was opened to adjust the pressure to atmospheric pressure. The bottom discharge valve was then opened, and the material was placed into a packaging barrel. The product weighed 319g, while the theoretical yield should be 336g, resulting in a calculated yield of 94.9%. Furthermore, NMR spectroscopy analysis showed that the main content of the product reached 99.82%. Turn on the vacuum valve and electric heating on the glycerol aqueous solution distillation vessel, adjust the vessel pressure to -0.097 MPa, and when the vessel temperature reaches 77.8℃, the water recovery is complete; continue to heat at a rate of 0.5℃ / min, and when the vessel temperature rises to 256.8℃, the glycerol recovery is complete.

[0020] Example 2 This embodiment provides a method for preparing 1-ethyl-3-methylimidazolium ionic liquids, and the operation example is as follows: S1. Open the reactor feed port and add 216g of solid 1-ethyl-3-methylimidazolium chloride and 237.6g of sodium trifluoromethanesulfonate into the reactor, then close the feed port; introduce 259.2g of glycerol into the reactor and start stirring; stir and react at 34.7℃ for 4.4h, then turn off the stirring. S2. Sequentially open the separator receiving valve and the reactor nitrogen valve to adjust the reactor pressure to 0.052MPa. Then, open the bottom outlet valve on the side of the reactor to transfer the mixed solution of crude 1-ethyl-3-methylimidazolium ionic liquid and glycerol to the filtration device for filtration. The filtration device is integrated on the inner wall of the reactor and has a barrel-cone structure. The filter screen of the filtration device is a stainless steel filter screen with a 200-mesh pore size. Then, it is transferred to the separator. S3. Open the separator inlet valve and control the water addition to 245g. Then turn on the separator agitator and agitate the material for 2.8 hours. After agitation, allow the material to stand for 3.4 hours, then open the discharge valve to separate the liquids. S4. Open the valve at the bottom of the separator leading to the 1-ethyl-3-methylimidazolium ionic liquid distillation vessel. When stratification appears in the sight glass at the bottom of the separator, close the valve and open the valve to the glycerol-water mixture distillation vessel, thus introducing the upper glycerol aqueous solution into the glycerol aqueous solution distillation vessel. S5. Open the vacuum valve of the 1-ethyl-3-methylimidazolium ionic liquid distillation vessel, adjust the vessel pressure to -0.098 MPa, and simultaneously turn on the electric heating to adjust the vessel temperature to 94.2℃. After the S6, 1-ethyl-3-methylimidazolium ionic liquid distillation vessel ran for 6.8 hours, the nitrogen valve on the vessel was opened to adjust the pressure to atmospheric pressure. The bottom discharge valve was then opened, and the material was placed into a packaging barrel. The product weighed 342g, and the theoretical yield should be 359.4g, with a calculated yield of 95.2%. Furthermore, NMR spectroscopy analysis showed that the main content of the product reached 99.76%. Turn on the vacuum valve and electric heating on the glycerol aqueous solution distillation vessel, adjust the vessel pressure to -0.096 MPa, and when the vessel temperature reaches 78.5℃, the water recovery is complete; continue to heat at a rate of 1.5℃ / min, and when the vessel temperature rises to 258.6℃, the glycerol recovery is complete.

[0021] Example 3 This embodiment provides a method for preparing 1-ethyl-3-methylimidazolium ionic liquids, and the operation example is as follows: S1. Open the reactor feed port and add 190g of solid 1-ethyl-3-methylimidazolium chloride and 380g of sodium bis(trifluoromethanesulfonyl)imide to the reactor, then close the feed port; introduce 228g of glycerol into the reactor and start stirring; stir and react at 45.7℃ for 4.1h, then turn off the stirring. S2. Sequentially open the separator receiving valve and the reactor nitrogen valve to adjust the reactor pressure to 0.064MPa. Then, open the bottom outlet valve on the side of the reactor to transfer the mixed solution of crude 1-ethyl-3-methylimidazolium ionic liquid and glycerol to the filtration device for filtration. The filtration device is integrated on the inner wall of the reactor and has a barrel-cone structure. The filter screen of the filtration device is a stainless steel filter screen with a 200-mesh pore size. Then, it is transferred to the separator. S3. Open the separator inlet valve and control the water addition to 278g. Then turn on the separator agitator and agitate the material for 3.1 hours. After agitation for 3.9 hours, open the discharge valve to separate the liquids. S4. Open the valve at the bottom of the separator leading to the 1-ethyl-3-methylimidazolium ionic liquid distillation vessel. When stratification appears in the sight glass at the bottom of the separator, close the valve and open the valve to the glycerol-water mixture distillation vessel, thus introducing the upper glycerol aqueous solution into the glycerol aqueous solution distillation vessel. S5. Open the vacuum valve of the 1-ethyl-3-methylimidazolium ionic liquid distillation vessel, adjust the vessel pressure to -0.097 MPa, and simultaneously turn on the electric heating to adjust the vessel temperature to 93.6℃. After the S6, 1-ethyl-3-methylimidazolium ionic liquid distillation vessel ran for 7.4 hours, the nitrogen valve on the vessel was opened to adjust the pressure to atmospheric pressure. The bottom discharge valve was then opened, and the material was placed into a packaging barrel. The product weighed 472.4g, while the theoretical yield should be 490.8g, resulting in a calculated yield of 96.3%. Furthermore, NMR spectroscopy analysis showed that the main content of the product reached 99.79%. Turn on the vacuum valve and electric heating on the glycerol aqueous solution distillation vessel, adjust the vessel pressure to -0.098 MPa, and when the vessel temperature reaches 78.9℃, the water recovery is complete; continue to heat at a rate of 2℃ / min, and when the vessel temperature rises to 256.6℃, the glycerol recovery is complete.

[0022] Example 4 This embodiment provides a method for preparing 1-ethyl-3-methylimidazolium ionic liquids, and the operation example is as follows: S1. Open the reactor feed port and add 200.5g of solid 1-ethyl-3-methylimidazolium chloride and 401g of sodium bis(trifluoromethanesulfonyl)imide to the reactor, then close the feed port; introduce 240.6g of glycerol into the reactor and start stirring; stir and react at 41.5℃ for 4.4h, then turn off the stirring. S2. Sequentially open the separator receiving valve and the reactor nitrogen valve to adjust the reactor pressure to 0.062MPa. Then, open the bottom outlet valve on the side of the reactor to transfer the mixed solution of crude 1-ethyl-3-methylimidazolium ionic liquid and glycerol to the filtration device for filtration. The filtration device is integrated on the inner wall of the reactor and has a barrel-cone structure. The filter screen of the filtration device is a stainless steel filter screen with a 200-mesh pore size. Then, it is transferred to the separator. S3. Open the separator inlet valve and control the water addition to 288g. Then turn on the separator agitator and agitate the material for 4.0 hours. After agitation, allow the material to stand for 3.8 hours, then open the discharge valve to separate the liquids. S4. Open the valve at the bottom of the separator leading to the 1-ethyl-3-methylimidazolium ionic liquid distillation vessel. When stratification appears in the sight glass at the bottom of the separator, close the valve and open the valve to the glycerol-water mixture distillation vessel, thus introducing the upper glycerol aqueous solution into the glycerol aqueous solution distillation vessel. S5. Open the vacuum valve of the 1-ethyl-3-methylimidazolium ionic liquid distillation vessel, adjust the vessel pressure to -0.098 MPa, and at the same time turn on the electric heating to adjust the vessel temperature to 92.7℃. After the S6, 1-ethyl-3-methylimidazolium ionic liquid distillation vessel ran for 7.7 hours, the nitrogen valve on the vessel was opened to adjust the pressure to atmospheric pressure. The bottom discharge valve was then opened, and the material was placed into a packaging barrel. The product weighed 490.8g, while the theoretical yield should be 517.9g, resulting in a calculated yield of 94.8%. Furthermore, NMR spectroscopy analysis showed that the main content of the product reached 99.53%. Turn on the vacuum valve and electric heating on the glycerol aqueous solution distillation vessel, adjust the vessel pressure to -0.097 MPa, and when the vessel temperature reaches 78.8℃, the water recovery is complete; continue to heat at a rate of 1℃ / min, and when the vessel temperature rises to 258.2℃, the glycerol recovery is complete.

[0023] The above description is only used to detail the specific embodiments of the present invention, but the technical solutions proposed by the present invention are not limited to the above methods. All equivalent modifications and variations made by those skilled in the art to the technology proposed by the present invention without departing from the basic principles of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing a high-purity imidazole ionic liquid, characterized in that, Includes the following steps: S1: 1-Ethyl-3-methylimidazolium chloride, sodium trifluoromethanesulfonate or sodium bis(trifluoromethanesulfonyl)imide and glycerol solvent are added sequentially into the reactor, and then the reaction is stirred. S2: After the reaction is complete, the stirring is turned off. The crude 1-ethyl-3-methylimidazolium ionic liquid and glycerol mixture solution are filtered by a filtration device and collected in a separator. Sodium chloride is retained in the reactor and discharged later. S3: Add pure water to the separator, turn on the separator and stir for a certain period of time, then let it stand. The upper layer is a mixed phase of water and glycerol, and the lower layer is a crude 1-ethyl-3-methylimidazolium ionic liquid phase. S4: The two phases in the separator are separated by the liquid separator and then enter the corresponding purification devices respectively; S5: The crude 1-ethyl-3-methylimidazolium ionic liquid was dehydrated by vacuum distillation to obtain the product; S6: The water and glycerol mixture is distilled under reduced pressure to obtain a reusable water phase and a glycerol phase.

2. The method for preparing a high-purity imidazole ionic liquid as described in claim 1, characterized in that, In S1, the mass ratio of 1-ethyl-3-methylimidazolium chloride: sodium trifluoromethanesulfonate: glycerol is 1:1.1:1.2; the mass ratio of 1-ethyl-3-methylimidazolium chloride: sodium bis(trifluoromethanesulfonylimide): glycerol is 1:2:1.

2.

3. The method for preparing a high-purity imidazole ionic liquid as described in claim 1, characterized in that, The reaction temperature in S1 is controlled at 30~80℃, and the reaction time is controlled at 3~8h.

4. The method for preparing a high-purity imidazole ionic liquid as described in claim 1, characterized in that, The filtration device described in S2 is integrated into the inner wall of the reactor and has an overall barrel-cone structure. The liquid is filtered out from the bottom side of the reactor, and the filter residue is released from the bottom of the reactor.

5. The method for preparing a high-purity imidazole ionic liquid as described in claim 1, characterized in that, The filter screen of the filtration device described in S2 is a stainless steel filter screen with a pore size of 200 mesh.

6. The method for preparing a high-purity imidazole ionic liquid as described in claim 1, characterized in that, The mass ratio of water added to S3 to the mass ratio of the mixed solution of 1-ethyl-3-methylimidazolium ionic liquid and glycerol is 0.4~0.8:

1.

7. The method for preparing a high-purity imidazole ionic liquid as described in claim 1, characterized in that, The stirring time in S3 is controlled at 2-5 hours, and the settling time is controlled at 1-4 hours.

8. The method for preparing a high-purity imidazole ionic liquid as described in claim 1, characterized in that, In S4, the separation of liquids was performed using the sight glass observation method.

9. The method for preparing a high-purity imidazole ionic liquid as described in claim 1, characterized in that, In S5, the pressure for vacuum distillation is controlled below -0.090 MPa, the temperature is controlled between 60 and 120°C, and the distillation time is controlled between 6 and 10 hours.

10. The method for preparing a high-purity imidazole ionic liquid as described in claim 1, characterized in that, In S6, the pressure for both water and glycerol vacuum distillation is controlled below -0.095 MPa. Water is distilled off first, at which point the temperature of the distillation vessel is 50-80℃. Then, the temperature is slowly increased at a rate of 0.5-2℃ / min to distill off glycerol, at which point the temperature of the distillation vessel is controlled at 200-260℃. Heating is stopped once no more glycerol is distilled off.