Method for preparing 1-ethyl-3-methylimidazole trifluoromethane sulfonate

Abstract

The invention provides a method for preparing 1-ethyl-3-methylimidazole trifluoromethane sulfonate, which comprises the following steps: S1, sequentially adding 1-ethyl-3-methylimidazole chlorine salt, sodium trifluoromethanesulfonate and glycerol solvent into a reactor, and then stirring for reaction; s2, stopping stirring after the reaction is finished, and standing and separating liquid in the reactor to obtain a crude product 1-ethyl-3-methylimidazolium trifluoromethane sulfonate and a crude product glycerol; s3, filtering the crude product 1-ethyl-3-methylimidazolium trifluoromethane sulfonate and the crude product glycerol, and respectively carrying out reduced pressure distillation on the crude product 1-ethyl-3-methylimidazolium trifluoromethane sulfonate and the crude product glycerol; s4, carrying out reduced pressure distillation on the crude product 1-ethyl-3-methylimidazole trifluoromethane sulfonate, so as to obtain pure 1-ethyl-3-methylimidazole trifluoromethane sulfonate; and distilling out and recovering the crude glycerol through reduced pressure distillation. According to the method, the product with the purity of 99.5% or above is obtained; and distilling and recycling the solvent glycerol. The method is simple in process, the yield can reach 93% or above, and large-scale production and application are easy to achieve.

Description

Technical Field

[0001] The invention belongs to the technical field of organic fluoride synthesis, and specifically relates to a method for preparing 1-ethyl-3-methylimidazolium trifluoromethanesulfonate. Background Art

[0002] 1-Ethyl-3-methylimidazolium trifluoromethanesulfonate is a kind of ionic liquid. It has surface activity and can be used as an electrolyte additive. At the same time, due to the characteristics of ionic liquids themselves being difficult to volatilize and having high solubility, it can be used as a green solvent. In recent years, the ionic liquid industry has developed rapidly, and 1-ethyl-3-methylimidazolium trifluoromethanesulfonate, as a product with better properties, has attracted widespread attention.

[0003] The published patents related to imidazole ionic liquids are as follows:

[0004] CN110396187B discloses a method for preparing an imidazole ionic liquid, which is prepared by reacting terminal hydroxyl polyepichlorohydrin with alkyl imidazoles having different chain lengths to prepare an imidazole ionic liquid containing chloride ions in the side chain; then the polyionic liquid is reacted with a metal salt, and the amount of the metal salt is adjusted to exchange the chloride ions with the anions in the metal salt during the ion exchange process with the polyionic liquid, thereby obtaining an imidazole ionic liquid containing two different anions in the side chain. Since the raw material epichlorohydrin belongs to a Class 2A carcinogen and the method lacks purification means, the product prepared by the process has a high impurity content.

[0005] CN114591181B discloses a method for preparing a high-purity ionic liquid, comprising: (1) dissolving a compound whose cation is a quaternary ammonium ion, a quaternary phosphonium ion, an imidazolium ion or an imidazolinium ion in an organic solvent to form an organic phase, and dissolving an anion such as [BF4] - , [PF6] - , [CF3SO3] - or [Tf2N] - The organic phase and the aqueous phase are mixed and stirred to allow the two phases to fully contact and react; and the ionic liquid is separated by a modified polyimide nanofiltration membrane. This method generates a large amount of wastewater, and water has limited solubility in impurities, resulting in high impurity content and excessive water content in the product phase.

[0006] The currently disclosed imidazole ionic liquids all have certain defects, and there is no specific preparation method suitable for the product described in the present invention. Therefore, it is very important to develop an efficient preparation method of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate. Summary of the invention

[0007] The technical problem to be solved by the present invention is to provide a method for preparing 1-ethyl-3-methylimidazolium trifluoromethanesulfonate with simple process and high product purity.

[0008] To achieve the above object, the present invention performs the following reaction:

[0009] CF3SO3Na+(C6H 11 N2)Cl→[C6H 11 N2] + [CF3SO3] - +NaCl

[0010] The technical solution of the present invention:

[0011] A method for preparing 1-ethyl-3-methylimidazolium trifluoromethanesulfonate comprises the following steps:

[0012] S1: adding 1-ethyl-3-methylimidazolium chloride, sodium trifluoromethanesulfonate and glycerol solvent into the reactor in sequence, and then stirring to react. After the reaction is completed, the stirring is turned off;

[0013] S2: the liquid in the reactor is allowed to stand and separate to obtain crude 1-ethyl-3-methylimidazolium trifluoromethanesulfonate and crude glycerol;

[0014] S3: filtration of crude 1-ethyl-3-methylimidazolium trifluoromethanesulfonate and crude glycerol;

[0015] S4: The crude 1-ethyl-3-methylimidazolium trifluoromethanesulfonate after filtration is subjected to reduced pressure distillation to obtain pure 1-ethyl-3-methylimidazolium trifluoromethanesulfonate; the crude glycerol after filtration is subjected to reduced pressure distillation to distill out the glycerol for recovery.

[0016] Preferably, the mass ratio of 1-ethyl-3-methylimidazolium chloride: sodium trifluoromethanesulfonate: glycerol in S1 is 1:1.1:1.2.

[0017] Preferably, the reaction temperature in S1 is controlled at 30-60° C., and the reaction time is controlled at 3-6 h.

[0018] Preferably, the standing and liquid separation time in S2 is controlled within 2 to 5 hours.

[0019] Preferably, the bottom layer in S2 is separated to obtain crude 1-ethyl-3-methylimidazolium trifluoromethanesulfonate, and the upper layer is separated to obtain crude glycerol, and the separation is judged by a sight glass.

[0020] Preferably, a stainless steel filter with a pore size of 200 mesh is used for filtration in S3, and the filtered 1-ethyl-3-methylimidazolium chloride is recycled.

[0021] Preferably, the crude 1-ethyl-3-methylimidazolium trifluoromethanesulfonate in S4 is distilled under reduced pressure, the impurity removed is glycerol, the kettle pressure is controlled below -0.095 MPa, the temperature is controlled at 240-260° C., and the distillation time is controlled at 6 to 8 h.

[0022] Preferably, the kettle temperature of the crude glycerol distillation in S4 is controlled at 240-260° C., the pressure is controlled below -0.095 MPa, and the distillation time is 12-16 h.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] The process of the invention comprises the following steps: 1-ethyl-3-methylimidazolium chloride and sodium trifluoromethanesulfonate are stirred in a glycerol solvent to form a suspension and react; after the reaction, the impurity sodium chloride is completely dissolved in the solvent glycerol; and according to the incompatibility and density difference between the crude product and the solvent glycerol, liquid separation, filtration and distillation purification are performed. The overall process flow is relatively simple, no waste water is generated and the cost is low.

[0025] The solvent glycerol of the invention is reused after distillation, and the method has a simple process and is easy to realize large-scale production and application.

[0026] The yield of the invention is stable at more than 93%, and the purity of the product is stable at more than 99.5%. DETAILED DESCRIPTION

[0027] The present invention is described in detail below in conjunction with specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and a specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0028] Example 1

[0029] This embodiment provides a method for preparing 1-ethyl-3-methylimidazolium trifluoromethanesulfonate, and the operation example is as follows:

[0030] S1, open the reactor feed port, add solid 1-ethyl-3-methylimidazole chloride 200g, sodium trifluoromethanesulfonate 220g into the reactor, and then close the feed port; pass 240g solvent glycerol into the reactor, and start stirring; 30 ℃ stirring reaction 4.5h, then turn off stirring;

[0031] S2, start to stand still, open the discharge valve after standing still for 3 hours, and prepare to discharge;

[0032] S3, filter using a stainless steel filter with a pore size of 200 mesh, the lower layer is the crude 1-ethyl-3-methylimidazolium trifluoromethane sulfonate, which enters the 1-ethyl-3-methylimidazolium trifluoromethane sulfonate distillation kettle after filtration;

[0033] When stratification occurs in the sight glass at the bottom of the reactor discharge port, close the valve of the 1-ethyl-3-methylimidazolium trifluoromethanesulfonate still, open the valve of the glycerol still, and introduce the upper glycerol solution into the glycerol still;

[0034] S4, open the vacuum valve of the 1-ethyl-3-methylimidazolium trifluoromethanesulfonate distillation kettle, adjust the kettle pressure to -0.096Mpa, and turn on the electric heating at the same time to adjust the kettle temperature to 252°C;

[0035] After the 1-ethyl-3-methylimidazolium trifluoromethanesulfonate distillation kettle was run for 6.3 hours, the nitrogen valve on the kettle was opened, the kettle pressure was adjusted to normal pressure, the discharge valve at the bottom of the kettle was opened, and the material was placed in the packaging barrel. The product weighed 320g, the theoretical product should be 338g, and the yield was calculated to be 94.7%; the main content of the product was detected by nuclear magnetic resonance F spectrum and reached 99.82%;

[0036] Open the vacuum valve and electric heating on the glycerin distillation kettle, adjust the kettle pressure to -0.097Mpa, and adjust the kettle temperature to 258℃. After distillation for 14.6h, the liquid level in the glycerin solvent recovery tank no longer rises, and the solvent glycerin recovery is completed.

[0037] Example 2

[0038] This embodiment provides a method for preparing 1-ethyl-3-methylimidazolium trifluoromethanesulfonate, and the operation example is as follows:

[0039] S1, open the reactor feed port, add solid 1-ethyl-3-methylimidazole chloride 220g, sodium trifluoromethanesulfonate 242g into the reactor, and then close the feed port; pass 264g solvent glycerol into the reactor, and start stirring; 35 ℃ stirring reaction 4.8h, then turn off stirring;

[0040] S2, start to stand still, open the discharge valve after standing still for 3.3 hours, and prepare to discharge;

[0041] S3, filter using a stainless steel filter with a pore size of 200 mesh, the lower layer is the crude 1-ethyl-3-methylimidazolium trifluoromethane sulfonate, which enters the 1-ethyl-3-methylimidazolium trifluoromethane sulfonate distillation kettle after filtration;

[0042] When stratification occurs in the sight glass at the bottom of the reactor discharge port, close the valve of the 1-ethyl-3-methylimidazolium trifluoromethanesulfonate still, open the valve of the glycerol still, and introduce the upper glycerol solution into the glycerol still;

[0043] S4, open the vacuum valve of the 1-ethyl-3-methylimidazolium trifluoromethanesulfonate distillation kettle, adjust the kettle pressure to -0.098Mpa, and turn on the electric heating at the same time to adjust the kettle temperature to 251°C;

[0044] After the 1-ethyl-3-methylimidazolium trifluoromethanesulfonate distillation kettle was run for 6.6 hours, the nitrogen valve on the kettle was opened, the kettle pressure was adjusted to normal pressure, the discharge valve at the bottom of the kettle was opened, and the material was put into the packaging barrel. The product weighed 349g, the theoretical product should be 371.8g, and the yield was calculated to be 93.9%; the main content of the product was detected by nuclear magnetic resonance F spectrum and reached 99.76%;

[0045] Open the vacuum valve and electric heating on the glycerin distillation kettle, adjust the kettle pressure to -0.095Mpa, and adjust the kettle temperature to 255°C. After 15.4 hours of distillation, the liquid level in the glycerin solvent recovery tank no longer rises, and the solvent glycerin recovery is completed.

[0046] Example 3

[0047] This embodiment provides a method for preparing 1-ethyl-3-methylimidazolium trifluoromethanesulfonate, and the operation example is as follows:

[0048] S1, open the reactor feed port, add solid 1-ethyl-3-methylimidazole chloride 190g, sodium trifluoromethanesulfonate 209g into the reactor, and then close the feed port; pass 228g solvent glycerol into the reactor, and start stirring; 40 ℃ stirring reaction 4.6h, then turn off stirring;

[0049] S2, start to stand still, open the discharge valve after standing still for 3.2 hours, and prepare to discharge;

[0050] S3, filter using a stainless steel filter with a pore size of 200 mesh, the lower layer is the crude 1-ethyl-3-methylimidazolium trifluoromethane sulfonate, which enters the 1-ethyl-3-methylimidazolium trifluoromethane sulfonate distillation kettle after filtration;

[0051] When stratification occurs in the sight glass at the bottom of the reactor discharge port, close the valve of the 1-ethyl-3-methylimidazolium trifluoromethanesulfonate still, open the valve of the glycerol still, and introduce the upper glycerol solution into the glycerol still;

[0052] S4, open the vacuum valve of the 1-ethyl-3-methylimidazolium trifluoromethanesulfonate distillation kettle, adjust the kettle pressure to -0.095Mpa, and turn on the electric heating at the same time to adjust the kettle temperature to 249°C;

[0053] After the 1-ethyl-3-methylimidazolium trifluoromethanesulfonate distillation kettle was run for 6.9 hours, the nitrogen valve on the kettle was opened, the kettle pressure was adjusted to normal pressure, the discharge valve at the bottom of the kettle was opened, and the material was put into the packaging barrel. The product weighed 302g, the theoretical product should be 321.1g, and the yield was calculated to be 94.1%; the main content of the product was detected by nuclear magnetic resonance F spectrum and reached 99.78%;

[0054] Open the vacuum valve and electric heating on the glycerin distillation kettle, adjust the kettle pressure to -0.097Mpa, and adjust the kettle temperature to 253°C. After 15.5 hours of distillation, the liquid level in the glycerin solvent recovery tank no longer rises, and the solvent glycerin recovery is completed.

[0055] Example 4

[0056] This embodiment provides a method for preparing 1-ethyl-3-methylimidazolium trifluoromethanesulfonate, and the operation example is as follows:

[0057] S1, open the reactor feed port, add solid 1-ethyl-3-methylimidazole chloride 200g, sodium trifluoromethanesulfonate 220g into the reactor, and then close the feed port; pass 240g solvent glycerol into the reactor, and start stirring; 50 ℃ stirring reaction 4.6h, then turn off stirring;

[0058] S2, start to stand still, open the discharge valve after standing still for 2 hours, and prepare to discharge;

[0059] S3, filter using a stainless steel filter with a pore size of 200 mesh, the lower layer is the crude 1-ethyl-3-methylimidazolium trifluoromethane sulfonate, which enters the 1-ethyl-3-methylimidazolium trifluoromethane sulfonate distillation kettle after filtration;

[0060] When stratification occurs in the sight glass at the bottom of the reactor discharge port, close the valve of the 1-ethyl-3-methylimidazolium trifluoromethanesulfonate still, open the valve of the glycerol still, and introduce the upper glycerol solution into the glycerol still;

[0061] S4, open the vacuum valve of the 1-ethyl-3-methylimidazolium trifluoromethanesulfonate distillation kettle, adjust the kettle pressure to -0.095Mpa, and turn on the electric heating at the same time to adjust the kettle temperature to 240°C;

[0062] After the 2-ethyl-3-methylimidazolium trifluoromethanesulfonate distillation kettle was run for 6.0 hours, the nitrogen valve on the kettle was opened, the kettle pressure was adjusted to normal pressure, the discharge valve at the bottom of the kettle was opened, and the material was placed in the packaging barrel. The product weighed 319.4g, the theoretical product should be 338.0g, and the yield was calculated to be 94.5%; the main content of the product was detected by nuclear magnetic resonance F spectrum and reached 99.79%;

[0063] Open the vacuum valve and electric heating on the glycerin distillation kettle, adjust the kettle pressure to -0.097Mpa, and adjust the kettle temperature to 253°C. After 16 hours of distillation, the liquid level in the glycerin solvent recovery tank no longer rises, and the solvent glycerin recovery is completed.

[0064] Example 5

[0065] This embodiment provides a method for preparing 1-ethyl-3-methylimidazolium trifluoromethanesulfonate, and the operation example is as follows:

[0066] S1, open the reactor feed port, add solid 1-ethyl-3-methylimidazole chloride 210g, sodium trifluoromethanesulfonate 231g into the reactor, and then close the feed port; pass 252g solvent glycerol into the reactor, and start stirring; 60 ℃ stirring reaction 4.6h, then turn off stirring;

[0067] S2, start to stand still, open the discharge valve after standing still for 5 hours, and prepare to discharge;

[0068] S3, filter using a stainless steel filter with a pore size of 200 mesh, the lower layer is the crude 1-ethyl-3-methylimidazolium trifluoromethane sulfonate, which enters the 1-ethyl-3-methylimidazolium trifluoromethane sulfonate distillation kettle after filtration;

[0069] When stratification occurs in the sight glass at the bottom of the reactor discharge port, close the valve of the 1-ethyl-3-methylimidazolium trifluoromethanesulfonate still, open the valve of the glycerol still, and introduce the upper glycerol solution into the glycerol still;

[0070] S4, open the vacuum valve of the 1-ethyl-3-methylimidazolium trifluoromethanesulfonate distillation kettle, adjust the kettle pressure to -0.095Mpa, and turn on the electric heating at the same time to adjust the kettle temperature to 260°C;

[0071] After the 3-ethyl-3-methylimidazolium trifluoromethanesulfonate distillation kettle was run for 8 hours, the nitrogen valve on the kettle was opened, the kettle pressure was adjusted to normal pressure, the discharge valve at the bottom of the kettle was opened, and the material was placed in the packaging barrel. The product weighed 332.5g, the theoretical product should be 354.9g, and the yield was calculated to be 93.7%; the main content of the product was detected by nuclear magnetic resonance F spectrum and reached 99.80%;

[0072] Open the vacuum valve and electric heating on the glycerin distillation kettle, adjust the kettle pressure to -0.097Mpa, and adjust the kettle temperature to 253°C. After 12 hours of distillation, the liquid level in the glycerin solvent recovery tank no longer rises, and the solvent glycerin recovery is completed.

[0073] Comparative Example 1

[0074] This embodiment provides a method for preparing 1-ethyl-3-methylimidazolium trifluoromethanesulfonate, and the operation example is as follows:

[0075] S1, open the reactor feed port, add solid 1-ethyl-3-methylimidazole chloride 200g, sodium trifluoromethanesulfonate 220g into the reactor, and then close the feed port; pass 240g solvent glycerol into the reactor, and start stirring; 30 ℃ stirring reaction 4.5h, then turn off stirring;

[0076] S2, start to stand still, open the discharge valve after standing still for 3 hours, and prepare to discharge;

[0077] S3, the lower layer is the crude product 1-ethyl-3-methylimidazolium trifluoromethanesulfonate, which is directly put into the 1-ethyl-3-methylimidazolium trifluoromethanesulfonate distillation kettle without filtration;

[0078] When stratification occurs in the sight glass at the bottom of the reactor discharge port, close the valve of the 1-ethyl-3-methylimidazolium trifluoromethanesulfonate still, open the valve of the glycerol still, and introduce the upper glycerol solution into the glycerol still;

[0079] S4, open the vacuum valve of the 1-ethyl-3-methylimidazolium trifluoromethanesulfonate distillation kettle, adjust the kettle pressure to -0.096Mpa, and turn on the electric heating at the same time to adjust the kettle temperature to 252°C;

[0080] After the 1-ethyl-3-methylimidazolium trifluoromethanesulfonate distillation kettle was run for 6.3 hours, the nitrogen valve on the kettle was opened, the kettle pressure was adjusted to normal pressure, the discharge valve at the bottom of the kettle was opened, and the material was placed in the packaging barrel. The product weighed 324.5 g, the theoretical product should be 338 g, and the yield was calculated to be 96%. In addition, the main content of the product was detected by nuclear magnetic resonance F spectrum, which was 96.72%, lower than the average product purity of 99.5% obtained by filtering operation; and there were obvious particles precipitated at the bottom of the solution, and the specific material was 1-ethyl-3-methylimidazolium chloride.

[0081] Open the vacuum valve and electric heating on the glycerin distillation kettle, adjust the kettle pressure to -0.097Mpa, and adjust the kettle temperature to 258℃. After distillation for 14.6h, the liquid level in the glycerin solvent recovery tank no longer rises, and the solvent glycerin recovery is completed.

[0082] The difference between this comparative example and Example 1 is that there is no filtration, and the final nuclear magnetic resonance F spectrum detection product main content reaches 96.72%, which is lower than the average value of 99.5% product purity obtained by filtering operation; and there are obvious particles precipitated at the bottom of the solution.

[0083] Comparative Example 2

[0084] This embodiment provides a method for preparing 1-ethyl-3-methylimidazolium trifluoromethanesulfonate, and the operation example is as follows:

[0085] S1, open the reactor feed port, add solid 1-ethyl-3-methylimidazole chloride 220g, sodium trifluoromethanesulfonate 242g into the reactor, and then close the feed port; pass 264g solvent glycerol into the reactor, and start stirring; 35 ℃ stirring reaction 4.8h, then turn off stirring;

[0086] S2, start to stand still, open the discharge valve after standing still for 3.3 hours, and prepare to discharge;

[0087] S3, filter using a stainless steel filter with a pore size of 200 mesh, the lower layer is the crude 1-ethyl-3-methylimidazolium trifluoromethane sulfonate, which enters the 1-ethyl-3-methylimidazolium trifluoromethane sulfonate distillation kettle after filtration;

[0088] When stratification occurs in the sight glass at the bottom of the reactor discharge port, close the valve of the 1-ethyl-3-methylimidazolium trifluoromethanesulfonate still, open the valve of the glycerol still, and introduce the upper glycerol solution into the glycerol still;

[0089] S4, open the vacuum valve of the 1-ethyl-3-methylimidazolium trifluoromethanesulfonate distillation kettle, adjust the kettle pressure to -0.090Mpa, and turn on the electric heating at the same time to adjust the kettle temperature to 251°C;

[0090] After the 1-ethyl-3-methylimidazolium trifluoromethanesulfonate distillation kettle was run for 6.6 hours, the nitrogen valve on the kettle was opened, the kettle pressure was adjusted to normal pressure, the discharge valve at the bottom of the kettle was opened, and the material was placed in the packaging barrel. The product weighed 354g, the theoretical product should be 371.8g, and the yield was calculated to be 95.2%; the main content of the product was detected by nuclear magnetic resonance F spectrum and reached 97.14%; which was lower than the average product purity of 99.5% obtained by performing the crude product distillation negative pressure operation below -0.095Mpa; and there was obvious stratification on the upper part of the solution, and the specific material was glycerol.

[0091] Open the vacuum valve and electric heating on the glycerin distillation kettle, adjust the kettle pressure to -0.095Mpa, and adjust the kettle temperature to 255°C. After 15.4 hours of distillation, the liquid level in the glycerin solvent recovery tank no longer rises, and the solvent glycerin recovery is completed.

[0092] The difference between this comparative example and Example 2 is that the vacuum degree in the kettle is reduced during the distillation of the crude product, and the average product purity obtained by the operation is 99.5%; and there is an obvious stratification on the upper part of the solution.

[0093] The above description is only used to introduce the specific implementation methods of the present invention in detail, but the technical solution proposed by the present invention is not limited to the above method. Without departing from the basic principles of the present technology, equivalent modifications and changes made by those skilled in the art to the technology proposed by the present invention should be included in the scope of the claims of the present invention.

Claims

1. A method for preparing 1-ethyl-3-methylimidazolium trifluoromethanesulfonate, characterized in that: The following steps are involved: S1: adding 1-ethyl-3-methylimidazolium chloride, sodium trifluoromethanesulfonate and glycerol solvent into the reactor in sequence, and then stirring to react. After the reaction is completed, the stirring is turned off; S2: the liquid in the reactor is allowed to stand and separate to obtain crude 1-ethyl-3-methylimidazolium trifluoromethanesulfonate and crude glycerol; S3: filtration of crude 1-ethyl-3-methylimidazolium trifluoromethanesulfonate and crude glycerol; S4: The crude 1-ethyl-3-methylimidazolium trifluoromethanesulfonate after filtration is subjected to reduced pressure distillation to obtain pure 1-ethyl-3-methylimidazolium trifluoromethanesulfonate; the crude glycerol after filtration is subjected to reduced pressure distillation to distill out the glycerol for recovery.

2. A method for preparing 1-ethyl-3-methylimidazolium trifluoromethanesulfonate according to claim 1, characterized in that: The mass ratio of 1-ethyl-3-methylimidazolium chloride: sodium trifluoromethanesulfonate: glycerol in S1 is 1:1.1:1.

2.

3. A method for preparing 1-ethyl-3-methylimidazolium trifluoromethanesulfonate according to claim 1, characterized in that: In S1, the reaction temperature is controlled at 30-60°C, and the reaction time is controlled at 3-6h.

4. A method for preparing 1-ethyl-3-methylimidazolium trifluoromethanesulfonate according to claim 1, characterized in that: The standing and separation time in S2 is controlled at 2 to 5 hours.

5. A method for preparing 1-ethyl-3-methylimidazolium trifluoromethanesulfonate according to claim 1, characterized in that: The bottom layer of S2 is separated into crude 1-ethyl-3-methylimidazolium trifluoromethanesulfonate, and the upper layer is separated into crude glycerol. The separation is judged by a sight glass.

6. A method for preparing 1-ethyl-3-methylimidazolium trifluoromethanesulfonate according to claim 1, characterized in that: A stainless steel filter with a pore size of 200 mesh is used for filtration in S3, and the filtered 1-ethyl-3-methylimidazolium chloride is recycled.

7. A method for preparing 1-ethyl-3-methylimidazolium trifluoromethanesulfonate according to claim 1, characterized in that: The crude 1-ethyl-3-methylimidazolium trifluoromethanesulfonate in S4 was distilled under reduced pressure to remove glycerol as the impurity. The kettle pressure was controlled below -0.095 MPa, the temperature was controlled at 240-260°C, and the distillation time was controlled at 6-8 h.

8. A method for preparing 1-ethyl-3-methylimidazolium trifluoromethanesulfonate according to claim 1, characterized in that: The kettle temperature of crude glycerol distillation in S4 is controlled at 240-260°C, the pressure is controlled below -0.095Mpa, and the distillation time is 12-16h.