Method for co-producing fluorobenzene compound and lithium hexafluorophosphate

Abstract

The invention relates to the technical field of chemical synthesis, in particular to a method for co-producing fluorobenzene compounds and lithium hexafluorophosphate. The method comprises the following steps: (1) heating and decomposing an aniline diazonium hexafluorophosphate compound to obtain a fluorobenzene compound, phosphorus pentafluoride and nitrogen; and (2) introducing a mixed gas of phosphorus pentafluoride and nitrogen into a solution of lithium fluoride and anhydrous hydrogen fluoride or a solution of lithium fluoride and an organic solvent for reaction to obtain lithium hexafluorophosphate. The method provided by the invention has the advantages of high product yield, small equipment and cost investment, no pressure to the environment, simple operation, and suitableness for large-scale industrial production.

Description

Technical Field

[0001] The invention relates to the technical field of chemical synthesis, and in particular to a method for co-producing fluorobenzene compounds and lithium hexafluorophosphate. Background Art

[0002] Fluorobenzene compounds have the advantages of low dosage, low toxicity, high efficacy and strong metabolic capacity in medicines and pesticides. When fluorine atoms or fluorine-containing groups are introduced into the benzene ring, their electrical effect and simulation effect change the distribution of electron cloud density inside the molecule, affecting the acidity and alkalinity of the structure, and then changing its activity; in addition, the introduction of fluorine atoms will increase the fat solubility of the compound, promote its absorption and transfer speed in the body, and change its physiological effects.

[0003] Lithium hexafluorophosphate is an inorganic compound with the chemical formula LiPF6. It is a white crystalline powder that is easily soluble in water and in low-concentration organic solvents such as methanol, ethanol, acetone, and carbonates. At present, lithium hexafluorophosphate is still the main material used as lithium-ion battery electrolyte in the short term due to its many advantages. Using phosphorus pentafluoride as a raw material, lithium hexafluorophosphate with excellent performance can be prepared, making the preparation of phosphorus pentafluoride more meaningful for research. So far, the main methods for preparing phosphorus pentafluoride that have been reported are as follows: (1) Directly use fluorine gas to fluorinate phosphorus or phosphorus pentoxide to obtain phosphorus pentafluoride: 5F2+2P=2PF5, 10F2+2P2O5=4PF5+5O2; This method involves great safety risks due to the use of highly active fluorine gas, and the high pressure places stringent requirements on the equipment.

[0004] (2) Japanese Patent Publication No. 4-175216 uses phosphorus pentachloride to react with anhydrous hydrogen fluoride to generate a mixed gas of phosphorus pentafluoride and hydrogen chloride. The principle is: PC15+5HF=PF5+5HCl.

[0005] This process has a high conversion rate and is suitable for large-scale production, but it produces a large amount of hydrochloric acid as a by-product, which contains a small amount of hydrogen fluoride. Its industrial application is limited and there is a great pressure of environmental pollution.

[0006] (3) Japanese Patent Publication No. JP2005-507849A decomposes hexafluorophosphoric acid to produce phosphorus pentafluoride, hydrogen fluoride and water and treats with fuming sulfuric acid: HPF6=PF5+HF, H2O+SO3=H2SO4, HF+SO3=FSO3H, H2O+PF5=POF3+2HF; This process will generate a large amount of sulfuric acid, which contains some fluorosulfonic acid. It cannot be used in industry, is difficult to handle, and has great environmental pressure. The sulfuric acid is particularly corrosive in the presence of hydrogen fluoride and has strict requirements on equipment. Even if fuming sulfuric acid is used, the water in the system can react with phosphorus pentafluoride to generate impurities such as phosphorus oxyfluoride, which affects the quality of the final product, lithium hexafluorophosphate.

[0007] In summary, the existing processes for preparing lithium hexafluorophosphate have by-products that are difficult to handle and are not environmentally friendly.

[0008] Fluorobenzene compounds and lithium hexafluorophosphate are both important chemical raw materials, but the existing technology does not produce the two together, resulting in problems such as difficult treatment of by-products in the production process, waste of by-products, and great pressure on the environment. Therefore, a reasonable, efficient, safe, environmentally friendly, simple to operate, and high product yield method for co-producing fluorobenzene compounds and lithium hexafluorophosphate is provided, which maximizes the use of by-products in the production of fluorobenzene compounds, simplifies the processing steps of intermediates, and reduces production costs, which is of great significance to the large-scale production of fluorobenzene compounds and lithium hexafluorophosphate. Summary of the invention

[0009] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for co-producing fluorobenzene compounds and lithium hexafluorophosphate. The mixed gas generated in the preparation process of the fluorobenzene compounds is phosphorus pentafluoride and nitrogen, and the mixed gas can be directly used as a raw material for the preparation of lithium hexafluorophosphate without separation, and the amount of nitrogen used in the preparation process can also be reduced. The method has a high product yield, a small investment in equipment and cost, no pressure on the environment, simple operation, and is suitable for large-scale industrial production.

[0010] The present invention is achieved through the following technical solutions: A method for co-producing fluorobenzene compounds and lithium hexafluorophosphate comprises the following steps: (1) heating and decomposing the compound of formula II to obtain a fluorobenzene compound of formula I, phosphorus pentafluoride and nitrogen; (2) Passing a mixed gas of phosphorus pentafluoride and nitrogen into a solution of lithium fluoride and anhydrous hydrogen fluoride or into a solution of lithium fluoride and an organic solvent to react and obtain lithium hexafluorophosphate; The reaction route is as follows: ; ; In the compounds of formula I and formula II, R1, R2, R3, R4 and R5 each independently represent hydrogen, halogen, C1-C4 alkyl, C1-C4 alkoxy or C3-C6 cycloalkyl.

[0011] In some embodiments of the present invention, at least one of R1, R2, R3, R4 and R5 is not hydrogen.

[0012] In some embodiments of the present invention, at least one of R1, R2, R3, R4 and R5 is halogen.

[0013] In some embodiments of the present invention, at least one of R1, R2, R3, R4 and R5 is fluorine.

[0014] In some embodiments of the present invention, the compound of formula II is any one of 2,4-difluoroaniline diazonium hexafluorophosphate, 3-bromo-5-fluoroaniline diazonium hexafluorophosphate, and 2-fluoro-3-methylaniline diazonium hexafluorophosphate.

[0015] In some embodiments of the present invention, the heating temperature in step (1) is 100-210°C, preferably 120-190°C.

[0016] In some embodiments of the present invention, in step (1), the product obtained after heating and decomposing the compound of formula II is separated by three-stage condensation to obtain the fluorobenzene compound of formula I and a mixed gas of phosphorus pentafluoride and nitrogen.

[0017] In some embodiments of the present invention, the molar ratio of the compound of formula II to lithium fluoride is 1-1.3:1, preferably 1.05-1.15:1.

[0018] In some embodiments of the present invention, the mass ratio of lithium fluoride to anhydrous hydrogen fluoride in step (2) is 1:10-90, preferably 1:30-60.

[0019] In some embodiments of the present invention, the mixed gas in step (2) is introduced into a solution of lithium fluoride and anhydrous hydrogen fluoride, and the reaction temperature is -20 to 15°C, preferably -10 to 5°C.

[0020] In some embodiments of the present invention, the mixed gas in step (2) is introduced into a solution of lithium fluoride and anhydrous hydrogen fluoride, and the reaction time is 0.5-6 hours, preferably 1-3 hours.

[0021] In some embodiments of the present invention, the mixed gas in step (2) is introduced into a solution of lithium fluoride and anhydrous hydrogen fluoride to react to obtain a lithium hexafluorophosphate hydrogen fluoride solution, which is then cooled, crystallized, filtered and dried to obtain lithium hexafluorophosphate.

[0022] In some preferred embodiments of the present invention, the anhydrous hydrogen fluoride in step (2) adopts the hydrogen fluoride filtrate obtained by the above filtration.

[0023] In some embodiments of the present invention, the organic solvent in step (2) is any one of carbonate solvents, carboxylate solvents, ether solvents, and nitrile solvents, or a combination of at least two of them.

[0024] Furthermore, the carboxylate solvent includes ethyl acetate and / or butyl acetate.

[0025] Furthermore, the nitrile solvent includes acetonitrile.

[0026] Furthermore, the ether solvent includes diethyl ether and / or ethylene glycol dimethyl ether.

[0027] Furthermore, the carbonate solvent includes any one of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethylene carbonate or propylene carbonate, or a combination of at least two thereof.

[0028] In some embodiments of the present invention, the mass ratio of lithium fluoride to organic solvent in step (2) is 1:18-60, preferably 1:18-36.

[0029] In some embodiments of the present invention, the mixed gas described in step (2) is introduced into a solution of lithium fluoride and an organic solvent, and the reaction temperature is -10 to 30°C, preferably 0 to 20°C.

[0030] In some embodiments of the present invention, the mixed gas in step (2) is introduced into a solution of lithium fluoride and an organic solvent, and the reaction time is 0.5-6 hours, preferably 1-3 hours.

[0031] In some embodiments of the present invention, the preparation method of the compound of formula II described in step (1) is as follows: Add the compound of formula III to an aqueous solution of hexafluorophosphoric acid and hydrochloric acid, then add an aqueous solution of sodium nitrite, stir until the reaction is complete, and dry to obtain a compound of formula II; The reaction route is as follows: .

[0032] In some embodiments of the present invention, during the preparation of the compound of formula II, the molar ratio of hexafluorophosphoric acid to the compound of formula III is 1.2:1, the reaction temperature does not exceed 5° C., and the reaction time is 2 h.

[0033] In some embodiments of the present invention, during the preparation of the compound of formula II, after the reaction is completed, the mixture is filtered to dryness, the filter cake is washed with ethanol and water, and dried to obtain the compound of formula II.

[0034] The present invention also relates to an aniline diazonium hexafluorophosphate compound, the structure of which is shown in Formula II: ; wherein R1, R2, R3, R4 and R5 each independently represent hydrogen, halogen, C1-C4 alkyl, C1-C4 alkoxy or C3-C6 cycloalkyl.

[0035] In some embodiments of the present invention, at least one of R1, R2, R3, R4 and R5 is not hydrogen.

[0036] In some embodiments of the present invention, at least one of R1, R2, R3, R4 and R5 is halogen.

[0037] In some embodiments of the present invention, at least one of R1, R2, R3, R4 and R5 is fluorine.

[0038] In some embodiments of the present invention, the compound of formula II is any one of 2,4-difluoroaniline diazonium hexafluorophosphate, 3-bromo-5-fluoroaniline diazonium hexafluorophosphate, and 2-fluoro-3-methylaniline diazonium hexafluorophosphate.

[0039] The beneficial effects of the present invention are: The invention provides a method for co-producing lithium hexafluorophosphate with fluorobenzene compounds. The method adopts a compound of formula II as a raw material to obtain a high-yield fluorobenzene compound. Phosphorus pentafluoride and nitrogen produced in the reaction are directly used for preparing lithium hexafluorophosphate without separation and purification. The obtained lithium hexafluorophosphate has high yield and high purity, and the production route is reasonable, efficient and simple to operate. In addition, the method does not produce toxic and harmful substances, avoids complex by-product treatment steps, is environmentally friendly, and is suitable for large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is the NMR fluorine spectrum of 2,4-difluoroaniline diazonium hexafluorophosphate prepared in Example 1.

[0041] Figure 2 This is the NMR fluorine spectrum of 1,2,4-trifluorobenzene prepared in Example 2.

[0042] Figure 3 This is the NMR fluorine spectrum of lithium hexafluorophosphate prepared in Example 2. DETAILED DESCRIPTION

[0043] The present invention will be further described below in conjunction with specific embodiments, and the advantages and features of the present invention will become clearer as the description proceeds. However, these embodiments are exemplary only and do not constitute any limitation to the scope of the present invention. It should be understood by those skilled in the art that the details and forms of the technical solution of the present invention may be modified or replaced without departing from the spirit and scope of the present invention, but these modifications and replacements all fall within the scope of protection of the present invention.

[0044] Example 1 Preparation of 2,4-difluoroaniline diazonium hexafluorophosphate 500g of 70% hexafluorophosphoric acid aqueous solution (hexafluorophosphoric acid content 2.4mol) was added to the reaction bottle, and then 500g of concentrated hydrochloric acid was added. 258g (2mol) 2,4-difluoroaniline was added dropwise at room temperature. The reaction was exothermic. After the addition was complete, stirring was continued at room temperature for 1 hour, and then the temperature was lowered to -5~0℃. A solution of 145g (2.1mol) sodium nitrite and 340g water was added dropwise. The reaction was exothermic. The addition rate was controlled to maintain the reaction temperature at no more than 5℃. After the addition was complete, the reaction was continued at 0-5℃ for 2 hours. Filter, wash the solid with 300mL of water and 300mL of ethanol precooled to 0℃ in turn, and dry to obtain 531.5g of 2,4-difluoroaniline diazo hexafluorophosphate with a yield of 93.0%. The NMR fluorine spectrum of the product is as follows: Figure 1 shown.

[0045] Example 2 Preparation of 1,2,4-trifluorobenzene and lithium hexafluorophosphate 286g (1.00mol) of 2,4-difluoroaniline diazo hexafluorophosphate was put into a reaction flask (the reaction flask was connected to a three-stage condenser, and the coolant was set at -10~-5℃), and the temperature was raised to 140℃ for decomposition reaction to obtain 1,2,4-trifluorobenzene, phosphorus pentafluoride and nitrogen. After three-stage condensation, an oily substance and a mixed gas of phosphorus pentafluoride and nitrogen were separated. The oily substance was distilled to obtain 1,2,4-trifluorobenzene (the product NMR fluorine spectrum was as follows: Figure 2 As shown), the yield is 94.4% and the purity is 99.1%. Under the temperature control of -20°C, the mixed gas of phosphorus pentafluoride and nitrogen is passed into a reactor containing 20.0g lithium fluoride (0.77mol) and 1800g hydrogen fluoride for about 3h. After the passing, the mixture is kept at -20°C for 6h to obtain a lithium hexafluorophosphate hydrogen fluoride solution, which is then cooled to -50°C for crystallization, filtered under temperature control, and the hydrogen fluoride filtrate can be applied to the next batch. The solid is dried to obtain the lithium hexafluorophosphate product (the product NMR fluorine spectrum is as shown Figure 3 As shown), yield 55.2%, purity 99.96%, moisture 9ppm, acid value 31ppm, ICP test results: sodium, calcium, potassium, nickel, lead, zinc, chromium, magnesium, copper, zinc, iron ions are all less than 3ppm, chloride ion 1.7ppm, sulfate ion 8ppm.

[0046] Example 3 Preparation of 1,2,4-trifluorobenzene and lithium hexafluorophosphate 278 g (0.97 mol) of 2,4-difluoroaniline diazo hexafluorophosphate was put into a reaction flask (the reaction flask was connected to a three-stage condenser, and the coolant was set at -10~-5°C), and the temperature was raised to 100°C for decomposition reaction to obtain 1,2,4-trifluorobenzene, phosphorus pentafluoride and nitrogen. After three-stage condensation, an oily substance and a mixed gas of phosphorus pentafluoride and nitrogen were separated. The oily substance was distilled to obtain 1,2,4-trifluorobenzene with a yield of 95.3% and a purity of 99.5%. At 0°C, a mixture of phosphorus pentafluoride and nitrogen is passed into a reactor containing 25.2g lithium fluoride (0.97mol) and 750g of hydrogen fluoride filtrate from the previous batch for about 3 hours. After the reaction is completed, the mixture is kept at 0°C for 4 hours to obtain a lithium hexafluorophosphate hydrogen fluoride solution, which is then cooled to -55°C for crystallization, filtered under temperature control, and the hydrogen fluoride filtrate can be applied to the next batch. The solid is dried to obtain a lithium hexafluorophosphate product with a yield of 97.2% and a purity of 99.97%. The moisture content is 5ppm, the acid value is 46ppm, and the ICP test results show that sodium, calcium, potassium, nickel, lead, zinc, chromium, magnesium, copper, zinc, and iron ions are all less than 3ppm, chloride ions are 1.9ppm, and sulfate ions are 9ppm.

[0047] The hydrogen fluoride used in this example is the hydrogen fluoride filtrate from the previous batch. Since lithium hexafluorophosphate is dissolved in the filtrate, the mother liquor can be reused to significantly increase the yield.

[0048] Example 4 Preparation of 1,2,4-trifluorobenzene and lithium hexafluorophosphate solution 272g (0.95mol) of 2,4-difluoroaniline diazo hexafluorophosphate was put into a reaction flask (the reaction flask was connected to a three-stage condenser, and the coolant was set at -10~-5℃), and the temperature was raised to 150℃ for decomposition reaction to obtain 1,2,4-trifluorobenzene, phosphorus pentafluoride and nitrogen. After three-stage condensation, an oily substance and a mixed gas of phosphorus pentafluoride and nitrogen were separated. The oily substance was distilled to obtain 1,2,4-trifluorobenzene with a yield of 94.8% and a purity of 99.3%. The mixed gas of phosphorus pentafluoride and nitrogen was slowly introduced into a reactor containing 23.4g of lithium fluoride (0.90mol) and 421g of dimethyl carbonate, and the reaction was carried out at 10℃ for 3h. The solution of lithium hexafluorophosphate dimethyl carbonate was obtained by filtration, with a yield of 95.9% (equivalent to the yield of pure lithium hexafluorophosphate) and a content of 21.8%. Moisture content is 5ppm, acid value is 35ppm, ICP test results: sodium, calcium, potassium, nickel, lead, zinc, chromium, magnesium, copper, zinc, and iron ions are all less than 3ppm, chloride ions are 1.2ppm, and sulfate ions are 11ppm.

[0049] Example 5 Preparation of 3-bromo-5-fluoroaniline diazonium hexafluorophosphate 500g of 70% hexafluorophosphoric acid aqueous solution (hexafluorophosphoric acid content 2.4mol) was put into a reaction bottle, and then 500g of concentrated hydrochloric acid was added. 370g (2mol) of 3-bromo-5-fluoroaniline was added dropwise at room temperature. The reaction was exothermic. After the addition was completed, stirring was continued at room temperature for 1 hour, and then the temperature was lowered to -2°C. A solution prepared by adding 159g (2.3mol) of sodium nitrite and 370g of water was added dropwise. The reaction was exothermic. The dropwise addition rate was controlled to maintain the reaction temperature at no more than 5°C. After the addition was completed, the reaction was continued at 0°C for 2 hours. The solid was filtered and washed with 300mL of water and 300mL of ethanol precooled to 0°C in sequence. After drying, 628g of 3-bromo-5-fluoroaniline diazo hexafluorophosphate was obtained with a yield of 90.5%.

[0050] Example 6 Preparation of 3,5-difluorobromobenzene and lithium hexafluorophosphate 347 g (1.00 mol) of 3-bromo-5-fluoroaniline diazo hexafluorophosphate was put into a reaction flask (the reaction flask was connected to a three-stage condenser, and the coolant was set at -10~-5°C), and the temperature was raised to 210°C for decomposition reaction to obtain 3,5-difluorobromobenzene, phosphorus pentafluoride and nitrogen. After three-stage condensation, an oily substance and a mixed gas of phosphorus pentafluoride and nitrogen were separated. The oily substance was distilled to obtain 3,5-difluorobromobenzene with a yield of 93.9% and a purity of 99.6%. At a temperature controlled temperature of 15° C., a mixed gas of phosphorus pentafluoride and nitrogen is introduced into a reactor containing 23.4 g of lithium fluoride (0.90 mol) and 900 g of hydrogen fluoride, and the mixture is reacted at 15° C. for 0.5 h to obtain a lithium hexafluorophosphate hydrogen fluoride solution, which is then cooled to -58° C. for crystallization, and filtered under temperature control. The hydrogen fluoride filtrate can be applied to the next batch, and the solid is dried to obtain a lithium hexafluorophosphate product with a yield of 50.4%, a purity of 99.98%, a moisture content of 11 ppm, an acid value of 31 ppm, and ICP test results: sodium, calcium, potassium, nickel, lead, zinc, chromium, magnesium, copper, zinc, and iron ions are all less than 3 ppm, chloride ions are 1.2 ppm, and sulfate ions are 6 ppm.

[0051] Example 7 Preparation of 3,5-difluorobromobenzene and lithium hexafluorophosphate 354 g (1.02 mol) of 3-bromo-5-fluoroaniline diazo hexafluorophosphate was put into a reaction flask (the reaction flask was connected to a three-stage condenser, and the coolant was set at -10~-5°C), and the temperature was raised to 170°C for decomposition reaction to obtain 3,5-difluorobromobenzene, phosphorus pentafluoride and nitrogen. After three-stage condensation, an oily substance and a mixed gas of phosphorus pentafluoride and nitrogen were separated. The oily substance was distilled to obtain 3,5-difluorobromobenzene with a yield of 95.9% and a purity of 99.6%. Under the temperature control of -8°C, a mixed gas of phosphorus pentafluoride and nitrogen is introduced into a reactor added with 23.4 g of lithium fluoride (0.90 mol) and 800 g of hydrogen fluoride filtrate from the previous batch, and the mixture is reacted at -8°C for 3 hours to obtain a lithium hexafluorophosphate hydrogen fluoride solution, which is then cooled to -50°C for crystallization, filtered under the temperature control, and the hydrogen fluoride filtrate can be applied to the next batch. The solid is dried to obtain a lithium hexafluorophosphate product with a yield of 98.4%, a purity of 99.98%, a moisture content of 10 ppm, an acid value of 25 ppm, and ICP test results: sodium, calcium, potassium, nickel, lead, zinc, chromium, magnesium, copper, zinc, and iron ions are all less than 3 ppm, chloride ions are 0.7 ppm, and sulfate ions are 8 ppm.

[0052] Example 8 Preparation of 3,5-difluorobromobenzene and lithium hexafluorophosphate solution 340 g (0.98 mol) of 3-bromo-5-fluoroaniline diazo hexafluorophosphate was put into a reaction flask (the reaction flask was connected to a three-stage condenser, and the coolant was set at -10~-5°C), and the temperature was raised to 180°C for decomposition reaction to obtain 3,5-difluorobromobenzene, phosphorus pentafluoride and nitrogen. After three-stage condensation, an oily substance and a mixed gas of phosphorus pentafluoride and nitrogen were separated. The oily substance was distilled to obtain 3,5-difluorobromobenzene with a yield of 95.1% and a purity of 99.0%. A mixed gas of phosphorus pentafluoride and nitrogen was introduced into a reactor containing 23.4 g of lithium fluoride (0.90 mol) and 500 g of acetonitrile, and the mixture was reacted at -10°C for 6 hours. The lithium hexafluorophosphate acetonitrile solution was filtered, with a yield of 96.9% (equivalent to the yield of pure lithium hexafluorophosphate), a content of 20.95%, a moisture content of 7 ppm, an acid value of 23 ppm, and ICP test results: sodium, calcium, potassium, nickel, lead, zinc, chromium, magnesium, copper, zinc, and iron ions were all less than 3 ppm, chloride ions were 0.5 ppm, and sulfate ions were 6 ppm.

[0053] Example 9 Preparation of 2-fluoro-3-methylaniline diazonium hexafluorophosphate 500g of 70% hexafluorophosphoric acid aqueous solution (hexafluorophosphoric acid content 2.4mol) was put into a reaction bottle, and then 500g of concentrated hydrochloric acid was added. 250.3g (2mol) of 2-fluoro-3-methylaniline was added dropwise at room temperature. The reaction was exothermic. After the addition was completed, stirring was continued at room temperature for 1 hour, and then the temperature was lowered to -5°C. A solution composed of 159g (2.3mol) of sodium nitrite and 370g of water was added dropwise. The reaction was exothermic. The dropwise addition speed was controlled to maintain the reaction temperature not exceeding 5°C. After the addition was completed, the reaction was continued at 5°C for 2 hours. The solid was filtered, and the solid was washed with 300mL of water and 300mL of ethanol precooled to 0°C in sequence. After drying, 507g of 2-fluoro-3-methylaniline diazo hexafluorophosphate was obtained with a yield of 89.9%.

[0054] Example 10 Preparation of 2,3-difluorotoluene and lithium hexafluorophosphate 282 g (1.00 mol) of 2-fluoro-3-methylaniline diazonium hexafluorophosphate was put into a reaction flask (the reaction flask was connected to a three-stage condenser, and the coolant was set at -10~-5°C), and the temperature was raised to 160°C for decomposition reaction to obtain 2,3-difluorotoluene, phosphorus pentafluoride and nitrogen. After three-stage condensation, an oily substance and a mixed gas of phosphorus pentafluoride and nitrogen were separated. The oily substance was distilled to obtain 2,3-difluorotoluene with a yield of 92.7% and a purity of 99.4%. Under the temperature control of -5°C, a mixed gas of phosphorus pentafluoride and nitrogen is passed into a reactor added with 23.4g of lithium fluoride (0.90mol) and 850g of hydrogen fluoride for about 3h. After the passing, the mixture is kept at -5°C for reaction for 4h to obtain a lithium hexafluorophosphate hydrogen fluoride solution, which is then cooled to -55°C for crystallization, filtered under temperature control, and the hydrogen fluoride filtrate can be applied to the next batch. The solid is dried to obtain a lithium hexafluorophosphate product with a yield of 53.5%, a purity of 99.96%, a moisture content of 6ppm, an acid value of 37ppm, and ICP test results: sodium, calcium, potassium, nickel, lead, zinc, chromium, magnesium, copper, zinc, and iron ions are all less than 3ppm, chloride ions are 1.2ppm, and sulfate ions are 9ppm.

[0055] Example 11 Preparation of 2,3-difluorotoluene and lithium hexafluorophosphate 282 g (1.00 mol) of 2-fluoro-3-methylaniline diazo hexafluorophosphate was put into a reaction flask (the reaction flask was connected to a three-stage condenser, and the coolant was set at -10~-5°C), and the temperature was raised to 175°C for decomposition reaction to obtain 2,3-difluorotoluene, phosphorus pentafluoride and nitrogen. After three-stage condensation, an oily substance and a mixed gas of phosphorus pentafluoride and nitrogen were separated. The oily substance was distilled to obtain 2,3-difluorotoluene with a yield of 93.6% and a purity of 99.7%. At 0°C, a mixture of phosphorus pentafluoride and nitrogen is passed into a reactor containing 23.4g lithium fluoride (0.90mol) and 750g of hydrogen fluoride filtrate from the previous batch for about 3 hours. After the reaction is completed, the mixture is kept at 0°C for 5 hours to obtain a lithium hexafluorophosphate hydrogen fluoride solution, which is then cooled to -56°C for crystallization, filtered under temperature control, and the hydrogen fluoride filtrate can be applied to the next batch. The solid is dried to obtain a lithium hexafluorophosphate product with a yield of 96.8% and a purity of 99.93%. The moisture content is 4ppm, the acid value is 26ppm, and the ICP test results show that sodium, calcium, potassium, nickel, lead, zinc, chromium, magnesium, copper, zinc, and iron ions are all less than 3ppm, chloride ions are 1.1ppm, and sulfate ions are 6ppm.

[0056] Example 12 Preparation of 2,3-difluorotoluene and lithium hexafluorophosphate solution 290.6g (1.03mol) of 2-fluoro-3-methylaniline diazonium hexafluorophosphate was put into a reaction flask (the reaction flask was connected to a three-stage condenser, and the coolant was set at -10~-5℃), and the temperature was raised to 165℃ for decomposition reaction to obtain 2,3-difluorotoluene, phosphorus pentafluoride and nitrogen. After three-stage condensation, an oily substance and a mixed gas of phosphorus pentafluoride and nitrogen were separated. The oily substance was distilled to obtain 2,3-difluorotoluene with a yield of 95.7% and a purity of 98.8%. The mixed gas of phosphorus pentafluoride and nitrogen was slowly passed into a reactor containing 23.4g of lithium fluoride (0.90mol) and 550g of ethylene glycol dimethyl ether, and the reaction was carried out at 30℃ for 0.5h. The solution of lithium hexafluorophosphate ethylene glycol dimethyl ether was obtained by filtration, with a yield of 97.7% (equivalent to the yield of pure lithium hexafluorophosphate) and a content of 19.5%. Moisture content is 7ppm, acid value is 32ppm, ICP test results: sodium, calcium, potassium, nickel, lead, zinc, chromium, magnesium, copper, zinc, and iron ions are all less than 3ppm, chloride ions are 1.1ppm, and sulfate ions are 7ppm.

[0057] Example 13 Preparation of 2,3-difluorotoluene and lithium hexafluorophosphate solution 296.0g (1.05mol) of 2-fluoro-3-methylaniline diazo hexafluorophosphate was put into a reaction flask (the reaction flask was connected to a three-stage condenser, and the coolant was set at -10~-5℃), and the temperature was raised to 165℃ for decomposition reaction to obtain 2,3-difluorotoluene, phosphorus pentafluoride and nitrogen. After three-stage condensation, an oily substance and a mixed gas of phosphorus pentafluoride and nitrogen were separated. The oily substance was distilled to obtain 2,3-difluorotoluene with a yield of 97.1% and a purity of 98.4%. The mixed gas of phosphorus pentafluoride and nitrogen was slowly introduced into a reactor containing 23.4g of lithium fluoride (0.90mol) and 1404g of ethyl acetate, and the mixture was reacted at 20℃ for 3h. The lithium hexafluorophosphate ethyl acetate solution was filtered to obtain a yield of 97.1% (equivalent to the yield of pure lithium hexafluorophosphate) and a content of 18.9%. Moisture content is 3ppm, acid value is 22ppm, ICP test results: sodium, calcium, potassium, nickel, lead, zinc, chromium, magnesium, copper, zinc, and iron ions are all less than 3ppm, chloride ions are 1.1ppm, and sulfate ions are 7ppm.

[0058] The above detailed description is a specific description of one feasible embodiment of the present invention. The embodiment is not intended to limit the patent scope of the present invention. Any equivalent implementation or modification that does not deviate from the present invention should be included in the scope of the technical solution of the present invention.

Claims

1. A method for co-producing fluorobenzene compounds and lithium hexafluorophosphate, characterized in that: The steps include: (1) heating and decomposing the compound of formula II to obtain a fluorobenzene compound of formula I, phosphorus pentafluoride and nitrogen; (2) Passing a mixed gas of phosphorus pentafluoride and nitrogen into a solution of lithium fluoride and anhydrous hydrogen fluoride or into a solution of lithium fluoride and an organic solvent to react and obtain lithium hexafluorophosphate; The reaction route is as follows: ； ； In the compounds of formula I and formula II, R1, R2, R3, R4 and R5 each independently represent hydrogen, halogen, C1-C4 alkyl, C1-C4 alkoxy or C3-C6 cycloalkyl.

2. The method according to claim 1, characterized in that At least one of R1, R2, R3, R4 and R5 is not hydrogen.

3. The method according to claim 2, characterized in that At least one of R1, R2, R3, R4 and R5 is fluorine.

4. The method according to claim 1, characterized in that: The heating temperature in step (1) is 100-210°C.

5. The method according to claim 1, characterized in that The molar ratio of the compound of formula II to lithium fluoride is 1-1.3:

1.

6. The method according to claim 1, characterized in that The mass ratio of lithium fluoride to anhydrous hydrogen fluoride in step (2) is 1:10-90.

7. The method according to claim 1, characterized in that The mixed gas in step (2) is introduced into a solution of lithium fluoride and anhydrous hydrogen fluoride, and the reaction temperature is -20 to 15°C.

8. The method according to claim 1, characterized in that The mixed gas in step (2) is introduced into a solution of lithium fluoride and anhydrous hydrogen fluoride to react to obtain a lithium hexafluorophosphate hydrogen fluoride solution, which is then cooled, crystallized, filtered and dried to obtain lithium hexafluorophosphate.

9. The method according to claim 8, characterized in that The anhydrous hydrogen fluoride in step (2) is the filtrate obtained by filtration in claim 8.

10. The method according to claim 1, characterized in that The organic solvent in step (2) is any one of carbonate solvents, carboxylate solvents, ether solvents, and nitrile solvents, or a combination of at least two of them.

11. The method according to claim 1, characterized in that The mass ratio of lithium fluoride to organic solvent in step (2) is 1:18-60.

12. The method according to claim 1, characterized in that The mixed gas described in step (2) is introduced into a solution of lithium fluoride and an organic solvent, and the reaction temperature is -10 to 30°C.

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