Preparation method of trifluoromethanesulfonic anhydride and lithium fluoride

Abstract

The invention relates to a preparation method of trifluoromethanesulfonic anhydride and lithium fluoride, which is characterized in that trifluoromethanesulfonyl fluoride and lithium hydroxide react in a solvent to obtain trifluoromethanesulfonic anhydride and lithium fluoride. Compared with a traditional multi-step complex reaction, the method has the advantages that the operation steps and time are greatly reduced, the operation difficulty is reduced, and industrial large-scale production is facilitated; the preparation of trifluoromethanesulfonic anhydride and lithium fluoride is realized in the same reaction system, and the production process is simplified; the yield of the obtained trifluoromethanesulfonic anhydride can reach 85% or above, the yield of the lithium fluoride can reach 90% or above, the yield is remarkably higher than that of a traditional preparation method, the raw material utilization rate is increased, and the production cost is reduced; the purity of trifluoromethanesulfonic anhydride can reach 99.5% or above, the strict requirements of high-end fields such as medicine and electronics for the purity of raw materials are met, the purity of lithium fluoride can also reach 98% or above, and lithium fluoride can serve as a high-quality lithium salt raw material; in addition, the method is environment-friendly, conforms to the development concept of green chemistry, and is beneficial to sustainable development.

Description

Technical Field

[0001] This invention relates to the field of organic synthesis technology, and in particular to a method for preparing trifluoromethanesulfonic anhydride and lithium fluoride. Background Technology

[0002] Trifluoromethanesulfonic anhydride, as an extremely important organic synthesis intermediate, has wide and crucial applications in many fields such as medicine, pesticides, and electronic materials. In the pharmaceutical field, it is often used to synthesize drug molecules with special structures and effects, and is indispensable in the key synthetic steps of some antiviral and anticancer drugs. In the pesticide field, it helps to develop new pesticides that are highly efficient, low in toxicity, and environmentally friendly, thereby improving the yield and quality of crops. In the field of electronic materials, it plays a vital role in the preparation of high-performance semiconductor materials and display materials, and can improve the performance and stability of electronic components.

[0003] However, existing methods for preparing trifluoromethanesulfonic anhydride present numerous problems that urgently need to be addressed. Traditional methods are typically cumbersome and complex, involving multiple reaction steps and intricate operational procedures. This not only leads to low production efficiency and increased labor and material costs but also easily introduces various impurities during the reaction process, affecting product quality. Some methods have low yields, resulting in significant waste of raw materials and further increasing production costs. Simultaneously, the purity of the product is insufficient to meet the increasingly stringent standards of high-end applications, limiting the wider application and development of trifluoromethanesulfonic anhydride. Furthermore, some preparation methods also cause environmental pollution problems, such as the use of large amounts of difficult-to-recover organic solvents and the generation of difficult-to-treat byproducts.

[0004] Lithium fluoride serves as a key precursor in lithium-ion battery electrolytes in the new energy field, enhancing ionic conductivity. In optics, it is a high-transmittance material in the deep ultraviolet band, used in ultraviolet lenses and laser windows. In metallurgy, it can lower aluminum electrolysis temperatures and improve current efficiency. In the nuclear industry, lithium fluoride can be used in neutron detectors and reactor shielding. However, existing methods for preparing lithium fluoride have several drawbacks. For example: the neutralization method (reaction of lithium carbonate with hydrofluoric acid) suffers from severe equipment corrosion, high energy consumption, low product purity, and large wastewater discharge; the metathesis method (reaction of ammonium fluoride with lithium carbonate) involves high mother liquor circulation pressure and is prone to ammonia residue; the ion exchange method produces high-salt wastewater with high treatment costs; and the high-temperature calcination method is energy-intensive, and some impurities react with lithium fluoride, affecting purity.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing trifluoromethanesulfonic anhydride and lithium fluoride, so as to solve the problems of complex operation, low yield, low purity and environmental pollution in existing preparation methods, and to achieve efficient, green and high-quality preparation of trifluoromethanesulfonic anhydride and lithium fluoride.

[0007] In a first aspect, the present invention provides a method for preparing trifluoromethanesulfonic anhydride and lithium fluoride, wherein trifluoromethanesulfonyl fluoride (CF3SO2F) and lithium hydroxide (LiOH) are reacted in a solvent to obtain trifluoromethanesulfonic anhydride ((CF3SO2)2O) and lithium fluoride (LiF).

[0008] Preferably, the solvent is toluene; more preferably, the toluene is anhydrous toluene with a purity of 99.5% or higher to ensure the stability of the reaction system. The toluene solvent can be recycled, reducing the consumption and emissions of organic solvents.

[0009] Preferably, the steps include:

[0010] S1. Add solvent and lithium hydroxide to the reaction vessel in sequence to make the lithium hydroxide evenly dispersed in the solvent;

[0011] S2. Trifluoromethanesulfonyl fluoride is slowly introduced into the reaction vessel to produce lithium trifluoromethanesulfonate (CF3SO3Li) and lithium fluoride (LiF). After the reaction is completed, the solvent and water in the reaction system are distilled off.

[0012] S3. Add solvent to the reaction vessel again to fully dissolve lithium trifluoromethanesulfonate;

[0013] S4. Cooling: Slowly introduce trifluoromethanesulfonyl fluoride into the reactor to react and generate trifluoromethanesulfonic anhydride and lithium fluoride.

[0014] Preferably, in step S1, the trifluoromethanesulfonyl fluoride must have a purity of 99% or higher to reduce the adverse effects of impurities on the reaction; the lithium hydroxide is selected from analytical grade to ensure its purity and activity.

[0015] Preferably, in step S1, the temperature inside the reactor is controlled at 20-30°C. This temperature range can ensure the dispersion of lithium hydroxide in toluene and avoid excessively vigorous subsequent reactions.

[0016] Preferably, in step S2, the reaction temperature is controlled at 30-40℃ to prevent excessively high temperatures from causing side reactions, and the reaction time is controlled at 1-2 hours.

[0017] Specifically, in step S2, the reaction formula for the reaction between trifluoromethanesulfonyl fluoride and lithium hydroxide is as follows:

[0018] CF3SO2F+2LiOH→CF3SO3Li+LiF+H2O

[0019] Preferably, in step S4, after cooling to 0-5°C, trifluoromethanesulfonyl fluoride is slowly introduced into the reactor and reacted for 2-3 hours to generate trifluoromethanesulfonic anhydride and lithium fluoride.

[0020] Specifically, in step S4, the reaction formula for the reaction between lithium trifluoromethanesulfonate and trifluoromethanesulfonyl fluoride is as follows:

[0021] CF3SO3Li+CF3SO2F→(CF3SO2)2O+LiF

[0022] Preferably, the following steps are also included:

[0023] S5. After the reaction is complete, the reaction solution is filtered; the filtered residue is washed and recrystallized to obtain lithium fluoride; the filtered filtrate is distilled to obtain trifluoromethanesulfonic anhydride.

[0024] Preferably, the distillation includes the following steps: first, distilling off trifluoromethanesulfonic anhydride under normal pressure, collecting the fraction at 81-83℃ to obtain crude trifluoromethanesulfonic anhydride; then, subjecting the crude product to secondary distillation, collecting the fraction at 81.5-82.5℃ under normal pressure to obtain pure trifluoromethanesulfonic anhydride.

[0025] In a second aspect, the present invention provides trifluoromethanesulfonic anhydride and lithium fluoride prepared by the aforementioned method.

[0026] A third aspect of the present invention provides the application of the trifluoromethanesulfonic anhydride in the fields of medicine, pesticides, materials, and semiconductor manufacturing; and the application of lithium fluoride in the fields of batteries, metallurgy, medicine, semiconductor manufacturing, optical fiber communication, and nuclear industry.

[0027] Compared with the prior art, the present invention has at least the following beneficial effects:

[0028] (1) Simplified operation process: The preparation method of the present invention can complete the preparation of trifluoromethanesulfonic anhydride through only two main reactions. Compared with the traditional multi-step complex reaction, it greatly reduces the operation steps and time, reduces the operation difficulty, and is conducive to large-scale industrial production. At the same time, the preparation of trifluoromethanesulfonic anhydride and lithium fluoride is realized in the same reaction system, which simplifies the production process.

[0029] (2) High reaction yield: By precisely controlling key conditions such as temperature, raw material ratio and reaction time in each step of the reaction, the reaction can proceed fully and efficiently, and the yield of trifluoromethanesulfonic anhydride can reach more than 85%, which is significantly higher than that of traditional preparation methods, improving raw material utilization and reducing production costs. At the same time, the yield of lithium fluoride is also high, reaching more than 90%.

[0030] (3) High-purity products: Using general impurity removal and purification methods, such as filtration, distillation, rectification, washing, recrystallization, etc., various impurities generated during the reaction process can be effectively removed. The final trifluoromethanesulfonic anhydride product has extremely high purity, meeting the strict requirements of high-end fields such as pharmaceuticals and electronics for the purity of raw materials. The purity of the obtained lithium fluoride product can also reach more than 98%, which can be used as a high-quality lithium salt raw material, which has important practical significance and market demand.

[0031] (4) Green and environmentally friendly: The byproduct lithium fluoride produced during the reaction is easy to handle, environmentally friendly, in line with the development concept of green chemistry, and conducive to sustainable development. Attached Figure Description

[0032] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0033] Figure 1 The image shows the X-ray diffraction analysis results of lithium fluoride provided in Example 1 of this invention. Detailed Implementation

[0034] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0035] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form includes the plural form unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0036] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] Example 1

[0038] This embodiment provides a method for preparing trifluoromethanesulfonic anhydride and lithium fluoride, comprising the following steps:

[0039] Raw material preparation: Prepare high-purity trifluoromethanesulfonyl fluoride with a purity of 99% or higher to reduce the adverse effects of impurities on the reaction; select analytical grade lithium hydroxide to ensure its purity and activity; use anhydrous toluene as solvent, requiring a toluene purity of 99.5% or higher to ensure the stability of the reaction system.

[0040] S1. Reaction system setup: In a 500mL dry reaction vessel equipped with a stirrer, thermometer, constant pressure dropping funnel and reflux condenser, add 200mL of anhydrous toluene, slowly add 24g (1mol) of lithium hydroxide powder, start stirring to make the lithium hydroxide uniformly disperse in the toluene to form a stable reaction system, and control the temperature of the reaction vessel at 25℃.

[0041] S2. Formation of lithium trifluoromethanesulfonate intermediate: 82 g (0.57 mol) of trifluoromethanesulfonyl fluoride was slowly introduced into the reactor at a rate of 0.1 mL / min; the introduction rate was strictly controlled to keep the temperature of the reaction system at 35 °C; after the introduction was completed, the reaction was stirred for 1.5 hours; as the reaction proceeded, the generated lithium trifluoromethanesulfonate and lithium fluoride gradually dispersed in the toluene system.

[0042] S3. Toluene distillation and dehydration: After the reaction is completed, the reaction system is transferred to a distillation apparatus. The temperature is gradually increased under normal pressure to distill off the toluene. Since toluene and water can form an azeotrope, the water generated in the reaction can be carried out during the distillation of toluene, thereby achieving the purpose of dehydration. Distillation is continued until almost no liquid is distilled off to ensure that the water in the system is completely removed. At this time, lithium trifluoromethanesulfonate and lithium fluoride are the main remaining substances in the reaction system.

[0043] S4. Reaction of lithium trifluoromethanesulfonate to trifluoromethanesulfonic anhydride: Add 100 mL of fresh anhydrous toluene to the reaction vessel after distillation to completely dissolve the lithium trifluoromethanesulfonate in the system. Cool the reaction system to 2°C, and under stirring conditions, introduce 41 g (0.285 mol) of trifluoromethanesulfonyl fluoride at a rate of 0.05 mL / min. Strictly control the introduction rate of trifluoromethanesulfonyl fluoride and the reaction temperature to avoid excessively vigorous reaction leading to side reactions. After the introduction is complete, continue stirring at 2°C for 2.5 hours to ensure that the reaction is fully completed, producing trifluoromethanesulfonic anhydride and lithium fluoride.

[0044] S5. Product Separation and Purification: After the reaction, the reaction solution was filtered. The filter residue mainly consisted of crude lithium fluoride. The filter residue was washed three times with 50 mL of deionized water each time. Then, 50 mL of anhydrous ethanol was added for recrystallization. After filtration and drying, 21 g of lithium fluoride product was obtained, with a yield of 91.3% and a purity of 98.5%. The X-ray diffraction analysis results are as follows: Figure 1As shown; the filtrate is a toluene solution containing trifluoromethanesulfonic anhydride. The filtrate is transferred to a distillation apparatus, where the trifluoromethanesulfonic anhydride is first distilled off under normal pressure, and the fraction at 81-83℃ is collected to obtain 50g of crude trifluoromethanesulfonic anhydride. To further improve the purity of the product, the crude product is subjected to a second distillation, and the fraction at 81.5-82.5℃ is collected under normal pressure to obtain 45g of high-purity trifluoromethanesulfonic anhydride product, with a yield of 85.7% and a purity of 99.6%. The toluene is recovered and reused through distillation.

[0045] The fluorine spectrum of the trifluoromethanesulfonic anhydride prepared in this embodiment is 19F NMR:19F NMR:δ-117, single peak.

[0046] Example 2

[0047] This embodiment provides a method for preparing trifluoromethanesulfonic anhydride and lithium fluoride, comprising the following steps:

[0048] Raw material preparation: Prepare high-purity trifluoromethanesulfonyl fluoride with a purity of 99% or higher to reduce the adverse effects of impurities on the reaction; select analytical grade lithium hydroxide to ensure its purity and activity; use anhydrous toluene as solvent, requiring a toluene purity of 99.5% or higher to ensure the stability of the reaction system.

[0049] S1. Reaction system setup: In a 1000mL dry reaction vessel equipped with a stirrer, thermometer, constant pressure dropping funnel and reflux condenser, add 400mL of anhydrous toluene, slowly add 48g (2mol) of lithium hydroxide powder, start stirring to make the lithium hydroxide evenly dispersed in the toluene to form a stable reaction system, and control the temperature of the reaction vessel at 22℃.

[0050] S2. Formation of lithium trifluoromethanesulfonate intermediate: 164 g (1.14 mol) of trifluoromethanesulfonyl fluoride was slowly introduced into the reactor at a rate of 0.12 mL / min; the introduction rate was strictly controlled to keep the temperature of the reaction system at 32℃. After the introduction was completed, the reaction was stirred for another 2 hours; as the reaction proceeded, the generated lithium trifluoromethanesulfonate and lithium fluoride gradually dispersed in the toluene system.

[0051] S3. Toluene distillation and dehydration: After the reaction is completed, the reaction system is transferred to a distillation apparatus. The temperature is gradually increased under normal pressure to distill off the toluene. Since toluene and water can form an azeotrope, the water generated in the reaction can be carried out during the distillation of toluene, thereby achieving the purpose of dehydration. Distillation is continued until almost no liquid is distilled off to ensure that the water in the system is completely removed. At this time, lithium trifluoromethanesulfonate and lithium fluoride are the main remaining substances in the reaction system.

[0052] S4. Reaction of lithium trifluoromethanesulfonate to trifluoromethanesulfonic anhydride: Add 200 mL of fresh anhydrous toluene to the reaction vessel after distillation to completely dissolve the lithium trifluoromethanesulfonate in the system. Cool the reaction system to 3°C, and under stirring conditions, introduce 82 g (0.57 mol) of trifluoromethanesulfonyl fluoride at a rate of 0.06 mL / min. Strictly control the introduction rate of trifluoromethanesulfonyl fluoride and the reaction temperature to avoid excessively vigorous reaction leading to side reactions. After the introduction is complete, continue stirring at 3°C ​​for 3 hours to ensure that the reaction is fully completed, producing trifluoromethanesulfonic anhydride and lithium fluoride.

[0053] S5. Product Separation and Purification: After the reaction, the reaction solution was filtered, and the filter residue mainly consisted of crude lithium fluoride. The filter residue was washed three times with 50 mL of deionized water each time, and then 50 mL of anhydrous ethanol was added for recrystallization. After filtration and drying, 42 g of lithium fluoride product was obtained, with a yield of 91.7% and a purity of 98.7%. The filtrate was a toluene solution containing trifluoromethanesulfonic anhydride. The filtrate was transferred to a distillation apparatus, and the trifluoromethanesulfonic anhydride was first distilled off under normal pressure. The fraction at 81-83℃ was collected to obtain 95 g of crude trifluoromethanesulfonic anhydride. To further improve the purity of the product, the crude product was subjected to a second distillation. The fraction at 81.5-82.5℃ was collected under normal pressure to obtain 88 g of high-purity trifluoromethanesulfonic anhydride product, with a yield of 87.4% and a purity of 99.7%. The toluene was recovered and reused by distillation.

[0054] Example 3

[0055] Raw material preparation: Prepare high-purity trifluoromethanesulfonyl fluoride with a purity of 99% or higher to reduce the adverse effects of impurities on the reaction; select analytical grade lithium hydroxide to ensure its purity and activity; use anhydrous toluene as solvent, requiring a toluene purity of 99.5% or higher to ensure the stability of the reaction system.

[0056] S1. Reaction system setup: In a 250mL dry reaction vessel equipped with a stirrer, thermometer, constant pressure dropping funnel and reflux condenser, add 100mL of anhydrous toluene, slowly add 12g (0.5mol) of lithium hydroxide powder, stir evenly, turn on the stirrer to make the lithium hydroxide evenly dispersed in the toluene to form a stable reaction system, and control the temperature of the reaction vessel at 28℃.

[0057] S2. Formation of lithium trifluoromethanesulfonate intermediate: 41 g (0.285 mol) of trifluoromethanesulfonyl fluoride was slowly introduced into the reactor at a rate of 0.08 mL / min; the introduction rate was strictly controlled to keep the temperature of the reaction system at 38℃; after the introduction was completed, the reaction was stirred for 1 hour; as the reaction proceeded, the generated lithium trifluoromethanesulfonate and lithium fluoride gradually dispersed in the toluene system.

[0058] S3. Toluene distillation and dehydration: After the reaction is completed, the reaction system is transferred to a distillation apparatus. The temperature is gradually increased under normal pressure to distill off the toluene. Since toluene and water can form an azeotrope, the water generated in the reaction can be carried out during the distillation of toluene, thereby achieving the purpose of dehydration. Distillation is continued until almost no liquid is distilled off to ensure that the water in the system is completely removed. At this time, lithium trifluoromethanesulfonate and lithium fluoride are the main remaining substances in the reaction system.

[0059] S4. Reaction of lithium trifluoromethanesulfonate to trifluoromethanesulfonic anhydride: Add 50 mL of fresh anhydrous toluene to the reaction vessel after distillation to completely dissolve the lithium trifluoromethanesulfonate in the system. Cool the reaction system to 1°C, and under stirring conditions, introduce 20.5 g (0.1425 mol) of trifluoromethanesulfonyl fluoride at a rate of 0.04 mL / min. Strictly control the introduction rate of trifluoromethanesulfonyl fluoride and the reaction temperature to avoid excessively vigorous reaction leading to side reactions. After the introduction is complete, continue stirring at 1°C for 2 hours to ensure that the reaction is fully completed, producing trifluoromethanesulfonic anhydride and lithium fluoride.

[0060] S5. Product Separation and Purification: After the reaction, the reaction solution was filtered. The filter residue mainly consisted of crude lithium fluoride. The filter residue was washed three times with 50 mL of deionized water each time, and then recrystallized with 50 mL of anhydrous ethanol. After filtration and drying, 10 g of lithium fluoride product was obtained, with a yield of 90.9% and a purity of 98.3%. The filtrate was a toluene solution containing trifluoromethanesulfonic anhydride. The filtrate was transferred to a distillation apparatus. The trifluoromethanesulfonic anhydride was first distilled off under normal pressure, and the fraction at 81-83℃ was collected to obtain 28 g of crude trifluoromethanesulfonic anhydride. To further improve the product purity, the crude product was subjected to a second distillation. The fraction at 81.5-82.5℃ was collected under normal pressure to obtain 25 g of high-purity trifluoromethanesulfonic anhydride product, with a yield of 83.3% and a purity of 99.5%. The toluene was recovered and reused by distillation.

[0061] In summary, this invention is based on the reaction of trifluoromethanesulfonyl fluoride with lithium hydroxide in toluene. By optimizing reaction conditions and improving separation and purification processes, it solves the problems of complex operation, low yield, low purity, and environmental pollution in existing preparation technologies. This invention achieves efficient, green, and high-quality preparation of trifluoromethanesulfonic anhydride, while simultaneously obtaining high-purity lithium fluoride as a byproduct. This meets market demand for high-quality trifluoromethanesulfonic anhydride and lithium fluoride, promoting the sustainable development of related industries. The method for preparing trifluoromethanesulfonic anhydride and lithium fluoride by reacting trifluoromethanesulfonyl fluoride with lithium hydroxide in toluene provided by this invention is practical and feasible, with significant advantages such as simple operation, high yield, high product purity, and environmental friendliness. It has broad industrial application prospects and market value.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A process for the preparation of triflic anhydride and lithium fluoride, characterized in that, The trifluoromethanesulfonic anhydride and lithium fluoride are obtained by reacting trifluoromethanesulfonyl fluoride with lithium hydroxide in a solvent.

2. The process for preparing triflic anhydride and lithium fluoride according to claim 1, characterized in that, The solvent is toluene.

3. The method of claim 1, wherein the triflic anhydride and lithium fluoride are prepared by the steps of: The method comprises the following steps: ​ S1, adding the solvent and lithium hydroxide into a reaction kettle in sequence, so that the lithium hydroxide is uniformly dispersed in the solvent; S2, slowly introducing trifluoromethanesulfonyl fluoride into the reaction kettle, so that lithium trifluoromethanesulfonate and lithium fluoride are generated, and after the reaction is completed, the solvent and water in the reaction system are distilled out; S3, adding the solvent into the reaction kettle again, so that the lithium trifluoromethanesulfonate is fully dissolved; S4, cooling, and slowly introducing trifluoromethanesulfonyl fluoride into the reaction kettle, so that the trifluoromethanesulfonic anhydride and lithium fluoride are generated.

4. The method for producing triflic anhydride and lithium fluoride according to claim 3, wherein In step S1, the temperature in the reaction kettle is controlled at 20-30℃.

5. The method for preparing trifluoromethanesulfonic anhydride and lithium fluoride according to claim 3, characterized in that, In step S2, the reaction temperature is controlled at 30-40℃, and the reaction time is controlled at 1-2 hours.

6. The method for preparing trifluoromethanesulfonic anhydride and lithium fluoride according to claim 3, characterized in that, In step S4, after being cooled to 0-5℃, the trifluoromethanesulfonyl fluoride is slowly introduced into the reaction kettle, and the reaction is fully carried out for 2-3 hours, so that the trifluoromethanesulfonic anhydride and lithium fluoride are generated.

7. The method for preparing trifluoromethanesulfonic anhydride and lithium fluoride according to claim 3, characterized in that, The method further comprises the following steps: S5, after the reaction is completed, the reaction liquid is filtered, the filtered residue is washed and recrystallized to obtain lithium fluoride, and the filtered filtrate is rectified to obtain the trifluoromethanesulfonic anhydride.

8. The method for preparing trifluoromethanesulfonic anhydride and lithium fluoride according to claim 7, characterized in that, The rectification comprises the following steps: firstly, the trifluoromethanesulfonic anhydride is distilled out at normal pressure, and the fraction at 81-83℃ is collected to obtain the crude trifluoromethanesulfonic anhydride; and secondly, the crude product is rectified again, and the fraction at 81.5-82.5℃ is collected at normal pressure to obtain the pure trifluoromethanesulfonic anhydride.

9. The trifluoromethanesulfonic anhydride and lithium fluoride obtained by the method for preparing the trifluoromethanesulfonic anhydride and lithium fluoride according to any one of claims 1-8.

10. The trifluoromethanesulfonic anhydride according to claim 9 is applied in the fields of medicine, pesticide, material and semiconductor manufacturing; and the lithium fluoride is applied in the fields of battery, metallurgy, medicine, semiconductor manufacturing, optical fiber communication and nuclear industry.

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