A method for co-producing fluorobenzene compounds and lithium hexafluorophosphate

Abstract

The present invention relates to the technical field of chemical synthesis, and particularly relates 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; (2) introducing 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 for reaction to obtain lithium hexafluorophosphate. The method of the present invention has high product yield, less investment in equipment and cost, no pressure on the environment, simple operation, and is suitable for large-scale industrial production.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical synthesis, and particularly relates 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 ability in pharmaceuticals such as medicines and pesticides. When fluorine atoms or fluorine-containing groups are introduced into the benzene ring, their electronic effects and mimetic effects change the distribution of the electron cloud density inside the molecule, affect the acidity and basicity of the structure, and thus change their activity; in addition, the introduction of fluorine atoms will increase the lipophilicity of the compound, promote the transmission speed of its absorption in the organism, and cause changes in physiological effects.

[0003] Lithium hexafluorophosphate is an inorganic compound with the chemical formula LiPF 6 , which is a white crystalline powder, soluble in water, and soluble in organic solvents such as low-concentration methanol, ethanol, acetone, and carbonate esters. At present, due to its many advantages, lithium hexafluorophosphate remains the main material for use as a lithium-ion battery electrolyte in the short term. And using phosphorus pentafluoride as a raw material can prepare lithium hexafluorophosphate with excellent performance, making the preparation of phosphorus pentafluoride more meaningful for research. So far, the reported preparation methods of phosphorus pentafluoride mainly include the following several:

[0004] (1) Directly fluorinating phosphorus or phosphorus pentoxide with fluorine gas to obtain phosphorus pentafluoride:

[0005] 5F 2 +2P = 2PF 5 , 10F 2 +2P 2 O 5 = 4PF 5 +5O 2 ;

[0006] This method uses highly active fluorine gas, posing a great safety risk, and the high pressure requires relatively harsh equipment requirements.

[0007] (2) Japanese Patent Laid-Open No. 4-175216 uses phosphorus pentachloride to react with anhydrous hydrogen fluoride to generate a mixed gas of phosphorus pentafluoride and hydrogen chloride, and its principle is: PC1 5 +5HF = PF 5 +5HCl.

[0008] This process has a high conversion rate and is suitable for large-scale production. However, this process produces a large amount of by-product hydrochloric acid, and this by-product acid contains a small amount of hydrogen fluoride, which has limitations in industrial applications and poses a great pressure on environmental pollution.

[0009] (3)Japanese Patent Publication No. JP2005-507849A decomposes hexafluorophosphoric acid to produce phosphorus pentafluoride, hydrogen fluoride and water, and treats it with fuming sulfuric acid:

[0010] HPF 6 =PF 5 +HF,H 2 O+SO 3 =H 2 SO 4 ,HF+SO 3 =FSO 3 H,H 2 O+PF 5 =POF 3 +2HF;

[0011] This process will generate a large amount of sulfuric acid, which contains some fluorosulfonic acid. It cannot be applied industrially, is not easy to handle, and causes great environmental pressure. This sulfuric acid has extremely high corrosiveness in the presence of hydrogen fluoride and requires strict equipment requirements. And even when using fuming sulfuric acid, 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.

[0012] In summary, the existing processes for preparing lithium hexafluorophosphate all have the problems that by-products are not easy to handle and are not environmentally friendly.

[0013] Both fluorobenzene compounds and lithium hexafluorophosphate are important chemical raw materials. However, the existing technologies do not jointly produce the two, resulting in problems such as by-products being not easy to handle, by-product waste, and great environmental pressure in the production process. Therefore, providing a method for co-producing fluorobenzene compounds and lithium hexafluorophosphate that is reasonable, efficient, safe, environmentally friendly, simple to operate, and has a high product yield, maximizing the utilization of by-products in the production of fluorobenzene compounds, simplifying the treatment steps of intermediate products, and reducing production costs is of great significance for the large-scale production of fluorobenzene compounds and lithium hexafluorophosphate. Summary of the Invention

[0014] The object of the present invention is to overcome the deficiencies of the prior art and provide a method for co-producing fluorobenzene compounds and lithium hexafluorophosphate. The mixed gas generated during the preparation of the fluorobenzene compound is phosphorus pentafluoride and nitrogen, and this mixed gas can be directly used as a raw material for the preparation of lithium hexafluorophosphate without separation, and it can also reduce the usage amount of nitrogen during the preparation process. This method has a high product yield, requires less equipment and cost investment, has no environmental pressure, is simple to operate, and is suitable for large-scale industrial production.

[0015] The present invention is achieved through the following technical solutions:

[0016] A method for co-producing fluorobenzene compounds and lithium hexafluorophosphate, comprising the following steps:

[0017] (1) Heat-decompose the compound of Formula II to obtain the fluorobenzene compound of Formula I, phosphorus pentafluoride, and nitrogen gas;

[0018] (2) Pass the mixed gas of phosphorus pentafluoride and nitrogen gas into a solution of lithium fluoride and anhydrous hydrogen fluoride or into a solution of lithium fluoride and an organic solvent to react, obtaining lithium hexafluorophosphate;

[0019] The reaction route is as follows:

[0020] ;

[0021] ;

[0022] Among them, in the compounds of Formula I and Formula II, R 1 , R 2 , R 3 , R 4 and R 5 each independently represent hydrogen, halogen, C1-C4 alkyl, C1-C4 alkoxy, or C3-C6 cycloalkyl.

[0023] In some embodiments of the present invention, at least one of R 1 , R 2 , R 3 , R 4 and R 5 is not hydrogen.

[0024] In some embodiments of the present invention, at least one of R 1 , R 2 , R 3 , R 4 and R 5 is halogen.

[0025] In some embodiments of the present invention, at least one of R 1 , R 2 , R 3 , R 4 and R 5 is fluorine.

[0026] 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.

[0027] In some embodiments of the present invention, the temperature of the heating in step (1) is 100-210 °C, preferably 120-190 °C.

[0028] In some embodiments of the present invention, the product obtained by 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.

[0029] 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.

[0030] 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.

[0031] 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 -20~15°C, preferably -10~5°C.

[0032] 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 h, preferably 1 - 3 h.

[0033] In some embodiments of the present invention, after the mixed gas in step (2) is introduced into a solution of lithium fluoride and anhydrous hydrogen fluoride, a lithium hexafluorophosphate hydrogen fluoride solution is obtained, which is cooled, crystallized, filtered and dried to obtain lithium hexafluorophosphate.

[0034] In some preferred embodiments of the present invention, the anhydrous hydrogen fluoride in step (2) is the hydrogen fluoride filtrate obtained by the above filtration.

[0035] In some embodiments of the present invention, the organic solvent in step (2) is any one or a combination of at least two of carbonate solvents, carboxylate solvents, ether solvents, and nitrile solvents.

[0036] Furthermore, the carboxylate solvents include ethyl acetate and / or butyl acetate.

[0037] Furthermore, the nitrile solvent includes acetonitrile.

[0038] Furthermore, the ether solvents include diethyl ether and / or ethylene glycol dimethyl ether.

[0039] Furthermore, the carbonate solvents include any one or a combination of at least two of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene carbonate or propylene carbonate.

[0040] In some embodiments of the present invention, the mass ratio of lithium fluoride to the organic solvent in step (2) is 1:18 - 60, preferably 1:18 - 36.

[0041] 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 - 20 °C.

[0042] 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 time is 0.5 - 6 h, preferably 1 - 3 h.

[0043] In some embodiments of the present invention, the preparation method of the compound of formula II described in step (1) is as follows:

[0044] 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 obtain the compound of formula II after drying;

[0045] The reaction route is as follows:

[0046] 。

[0047] 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.

[0048] In some embodiments of the present invention, during the preparation of the compound of formula II, after the reaction is complete, filter by suction until dry, wash the filter cake with ethanol and water, and obtain the compound of formula II after drying.

[0049] The present invention also relates to an aniline diazonium hexafluorophosphate compound, the structure of which is as shown in the compound of formula II:

[0050] ;

[0051] Wherein, R 1 、R 2 、R 3 、R 4 and R 5 each independently represents hydrogen, halogen, C1 - C4 alkyl, C1 - C4 alkoxy or C3 - C6 cycloalkyl.

[0052] In some embodiments of the present invention, at least one of R 1 、R 2 、R 3 、R 4 and R 5 is not hydrogen.

[0053] In some embodiments of the present invention, R 1 、R 2 、R 3 、R 4 and R 5At least one of them is a halogen.

[0054] In some embodiments of the present invention, R 1 , R 2 , R 3 , R 4 and R 5 At least one of them is fluorine.

[0055] 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.

[0056] The beneficial effects of the present invention are as follows:

[0057] The present invention provides a method for co-producing lithium hexafluorophosphate with fluorobenzene compounds. The method uses the compound of Formula II as a raw material to obtain fluorobenzene compounds with high yields. The phosphorus pentafluoride and nitrogen gas generated in the reaction can be directly used for the preparation of lithium hexafluorophosphate without separation and purification. The obtained lithium hexafluorophosphate has high yields and high purity. The production route is reasonable, efficient, and easy 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. Description of the Drawings

[0058] Figure 1 19F NMR spectrum of 2,4-difluoroaniline diazonium hexafluorophosphate prepared in Example 1.

[0059] Figure 2 19F NMR spectrum of 1,2,4-trifluorobenzene prepared in Example 2.

[0060] Figure 3 19F NMR spectrum of lithium hexafluorophosphate prepared in Example 2. Detailed Embodiments

[0061] The present invention will be further described below with reference to specific embodiments. The advantages and features of the present invention will become clearer as the description progresses. However, these embodiments are merely exemplary and do not constitute any limitation to the scope of the present invention. Those skilled in the art should understand that modifications or substitutions can be made to the details and forms of the technical solutions of the present invention without departing from the spirit and scope of the present invention, and such modifications and substitutions fall within the protection scope of the present invention.

[0062] Example 1 Preparation of 2,4-difluoroaniline diazonium hexafluorophosphate

[0063] Put 500 g of 70% aqueous solution of hexafluorophosphoric acid (2.4 mo1 of hexafluorophosphoric acid content) into the reaction flask, then add 500 g of concentrated hydrochloric acid, and dropwise add 258 g (2 mo1) of 2,4-difluoroaniline at room temperature. The reaction is exothermic. After dropping, continue to stir at room temperature for 1 hour, and then cool down to -5~0 °C. Dropwise add a solution prepared from 145 g (2.1 mo1) of sodium nitrite and 340 g of water. The reaction is exothermic. Control the dropping rate to maintain the reaction temperature not exceeding 5 °C. After adding, continue to keep the temperature at 0-5 °C for heat preservation reaction for 2 hours, filter, and wash the solid successively with 300 mL of water and 300 mL of ethanol pre-cooled to 0 °C. After drying, 531.5 g of 2,4-difluoroaniline diazonium hexafluorophosphate is obtained, with a yield of 93.0%. The 19F NMR spectrum of the product is as shown in Figure 1 shown.

[0064] Example 2 Preparation of 1,2,4-trifluorobenzene and lithium hexafluorophosphate

[0065] Put 286 g (1.00 mol) of 2,4-difluoroaniline diazonium hexafluorophosphate into the reaction flask (the reaction flask is connected to a three-stage condenser, and the coolant is set at -10~-5 °C), heat up to 140 °C for decomposition reaction to obtain 1,2,4-trifluorobenzene, phosphorus pentafluoride and nitrogen. After separation by three-stage condensation, an oily substance and a mixed gas of phosphorus pentafluoride and nitrogen are obtained. The oily substance is distilled to obtain 1,2,4-trifluorobenzene (the 19F NMR spectrum of the product is as shown in Figure 2 shown), with a yield of 94.4% and a purity of 99.1%. At -20 °C, the mixed gas of phosphorus pentafluoride and nitrogen is introduced into a reactor containing 20.0 g of lithium fluoride (0.77 mol) and 1800 g of hydrogen fluoride for about 3 h. After passing, keep the temperature at -20 °C for heat preservation reaction for 6 h to obtain a lithium hexafluorophosphate hydrogen fluoride solution, then cool down to -50 °C for crystallization, control the temperature for filtration, and the hydrogen fluoride filtrate can be recycled to the next batch. The solid is dried to obtain a lithium hexafluorophosphate product (the 19F NMR spectrum of the product is as shown in Figure 3 shown), with a yield of 55.2%, a purity of 99.96%, a moisture content of 9 ppm, an acid value of 31 ppm. The ICP test results show that the contents of sodium, calcium, potassium, nickel, lead, zinc, chromium, magnesium, copper, zinc, and iron ions are all less than 3 ppm, the chloride ion content is 1.7 ppm, and the sulfate ion content is 8 ppm.

[0066] Example 3 Preparation of 1,2,4-trifluorobenzene and lithium hexafluorophosphate

[0067] Charge 278 g (0.97 mol) of 2,4-difluoroaniline diazonium hexafluorophosphate into a reaction flask (the reaction flask is connected to a three-stage condenser, and the coolant is set at -10~-5 °C). Heat up to 100 °C for decomposition reaction to obtain 1,2,4-trifluorobenzene, phosphorus pentafluoride and nitrogen. After three-stage condensation separation, an oily substance and a mixed gas of phosphorus pentafluoride and nitrogen are obtained. The oily substance is distilled to obtain 1,2,4-trifluorobenzene with a yield of 95.3% and a purity of 99.5%. Under temperature control at 0 °C, pass the mixed gas of phosphorus pentafluoride and nitrogen into a reactor containing 25.2 g of lithium fluoride (0.97 mol) and 750 g of the filtrate of hydrogen fluoride from the previous batch for about 3 h. After passing, keep the reaction at 0 °C for 4 h to obtain a lithium hexafluorophosphate hydrogen fluoride solution. Then cool down to -55 °C for crystallization, control the temperature for filtration, and the hydrogen fluoride filtrate can be recycled 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 5 ppm, the acid value is 46 ppm, and the ICP test results show that the contents of sodium, calcium, potassium, nickel, lead, zinc, chromium, magnesium, copper, zinc, and iron ions are all less than 3 ppm, the chloride ion content is 1.9 ppm, and the sulfate ion content is 9 ppm.

[0068] In this example, the hydrogen fluoride used is the filtrate of hydrogen fluoride from the previous batch. Since lithium hexafluorophosphate is dissolved in the filtrate, recycling the mother liquor can significantly improve the yield.

[0069] Example 4 Preparation of 1,2,4-trifluorobenzene and lithium hexafluorophosphate solution

[0070] Charge 272 g (0.95 mol) of 2,4-difluoroaniline diazonium hexafluorophosphate into a reaction flask (the reaction flask is connected to a three-stage condenser, and the coolant is set at -10~-5 °C). Heat up to 150 °C for decomposition reaction to obtain 1,2,4-trifluorobenzene, phosphorus pentafluoride and nitrogen. After three-stage condensation separation, an oily substance and a mixed gas of phosphorus pentafluoride and nitrogen are obtained. The oily substance is distilled to obtain 1,2,4-trifluorobenzene with a yield of 94.8% and a purity of 99.3%. Slowly pass the mixed gas of phosphorus pentafluoride and nitrogen into a reactor containing 23.4 g of lithium fluoride (0.90 mol) and 421 g of dimethyl carbonate and react at 10 °C for 3 h. Filter to obtain a lithium hexafluorophosphate dimethyl carbonate solution with a yield of 95.9% (yield of pure lithium hexafluorophosphate) and a content of 21.8%. The moisture content is 5 ppm, the acid value is 35 ppm, and the ICP test results show that the contents of sodium, calcium, potassium, nickel, lead, zinc, chromium, magnesium, copper, zinc, and iron ions are all less than 3 ppm, the chloride ion content is 1.2 ppm, and the sulfate ion content is 11 ppm.

[0071] Example 5 Preparation of 3-bromo-5-fluoroaniline diazonium hexafluorophosphate

[0072] Put 500 g of 70% aqueous solution of hexafluorophosphoric acid (2.4 mo1 of hexafluorophosphoric acid content) into the reaction flask, then add 500 g of concentrated hydrochloric acid, and dropwise add 370 g (2 mo1) of 3-bromo-5-fluoroaniline at room temperature. The reaction is exothermic. After dropping, continue to stir at room temperature for 1 hour, and then cool down to -2 °C. Dropwise add a solution prepared from 159 g (2.3 mo1) of sodium nitrite and 370 g of water. The reaction is exothermic. Control the dropping rate to maintain the reaction temperature not exceeding 5 °C. After adding, continue to keep the temperature at 0 °C for reaction for 2 hours. Filter, and wash the solid successively with 300 mL of water pre-cooled to 0 °C and 300 mL of ethanol. After drying, 628 g of 3-bromo-5-fluoroaniline diazonium hexafluorophosphate is obtained, with a yield of 90.5%.

[0073] Example 6 Preparation of 3,5-difluorobromobenzene and lithium hexafluorophosphate

[0074] Put 347 g (1.00 mol) of 3-bromo-5-fluoroaniline diazonium hexafluorophosphate into the reaction flask (the reaction flask is connected to a three-stage condenser, and the coolant is set at -10~-5 °C), heat up to 210 °C for decomposition reaction to obtain 3,5-difluorobromobenzene, phosphorus pentafluoride and nitrogen. After three-stage condensation separation, an oily substance and a mixed gas of phosphorus pentafluoride and nitrogen are obtained. The oily substance is distilled to obtain 3,5-difluorobromobenzene, with a yield of 93.9% and a purity of 99.6%. Control the temperature at 15 °C and pass the mixed gas of phosphorus pentafluoride and nitrogen into the reactor containing 23.4 g of lithium fluoride (0.90 mol) and 900 g of hydrogen fluoride, and react at 15 °C for 0.5 h to obtain a lithium hexafluorophosphate hydrogen fluoride solution. Then cool down to -58 °C for crystallization, control the temperature for filtration, and the hydrogen fluoride filtrate can be recycled to the next batch. The solid is dried to obtain a lithium hexafluorophosphate product, with a yield of 50.4%, a purity of 99.98%, a water content of 11 ppm, an acid value of 31 ppm. The ICP test results show that the contents of sodium, calcium, potassium, nickel, lead, zinc, chromium, magnesium, copper, zinc, and iron ions are all less than 3 ppm, the chloride ion content is 1.2 ppm, and the sulfate ion content is 6 ppm.

[0075] Example 7 Preparation of 3,5-difluorobromobenzene and lithium hexafluorophosphate

[0076] Charge 354 g (1.02 mol) of 3-bromo-5-fluoroaniline diazonium hexafluorophosphate into a reaction flask (the reaction flask is connected to a three-stage condenser, and the coolant is set at -10~-5 °C), and heat up to 170 °C for decomposition reaction to obtain 3,5-difluorobromobenzene, phosphorus pentafluoride and nitrogen. After three-stage condensation separation, an oily substance and a mixed gas of phosphorus pentafluoride and nitrogen are obtained. The oily substance is distilled to obtain 3,5-difluorobromobenzene with a yield of 95.9% and a purity of 99.6%. While controlling the temperature at -8 °C, pass the mixed gas of phosphorus pentafluoride and nitrogen into a reactor containing 23.4 g of lithium fluoride (0.90 mol) and 800 g of the hydrogen fluoride filtrate from the previous batch, and react at -8 °C for 3 h to obtain a lithium hexafluorophosphate hydrogen fluoride solution. Then cool down to -50 °C for crystallization, control the temperature for filtration, 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 water content of 10 ppm, an acid value of 25 ppm. The ICP test results show that the contents of sodium, calcium, potassium, nickel, lead, zinc, chromium, magnesium, copper, zinc, and iron ions are all less than 3 ppm, the chloride ion content is 0.7 ppm, and the sulfate ion content is 8 ppm.

[0077] Example 8 Preparation of 3,5-difluorobromobenzene and lithium hexafluorophosphate solution

[0078] Charge 340 g (0.98 mol) of 3-bromo-5-fluoroaniline diazonium hexafluorophosphate into a reaction flask (the reaction flask is connected to a three-stage condenser, and the coolant is set at -10~-5 °C), and heat up to 180 °C for decomposition reaction to obtain 3,5-difluorobromobenzene, phosphorus pentafluoride and nitrogen. After three-stage condensation separation, an oily substance and a mixed gas of phosphorus pentafluoride and nitrogen are obtained. The oily substance is distilled to obtain 3,5-difluorobromobenzene with a yield of 95.1% and a purity of 99.0%. Pass the mixed gas of phosphorus pentafluoride and nitrogen into a reactor containing 23.4 g of lithium fluoride (0.90 mol) and 500 g of acetonitrile, and react at -10 °C for 6 h. Filter to obtain a lithium hexafluorophosphate acetonitrile solution with a yield of 96.9% (the yield of lithium hexafluorophosphate after conversion), a content of 20.95%, a water content of 7 ppm, an acid value of 23 ppm. The ICP test results show that the contents of sodium, calcium, potassium, nickel, lead, zinc, chromium, magnesium, copper, zinc, and iron ions are all less than 3 ppm, the chloride ion content is 0.5 ppm, and the sulfate ion content is 6 ppm.

[0079] Example 9 Preparation of 2-fluoro-3-methylaniline diazonium hexafluorophosphate

[0080] Put 500 g of 70% aqueous solution of hexafluorophosphoric acid (the content of hexafluorophosphoric acid is 2.4 mo1) into the reaction flask, then add 500 g of concentrated hydrochloric acid, and dropwise add 250.3 g (2 mo1) of 2-fluoro-3-methylaniline at room temperature. The reaction is exothermic. After dropping, continue to stir at room temperature for 1 hour, and then cool down to -5°C. Dropwise add a solution prepared from 159 g (2.3 mo1) of sodium nitrite and 370 g of water. The reaction is exothermic. Control the dropping rate to maintain the reaction temperature not exceeding 5°C. After adding, continue to keep the temperature at 5°C for reaction for 2 hours. Filter, and wash the solid successively with 300 mL of water pre-cooled to 0°C and 300 mL of ethanol. After drying, 507 g of 2-fluoro-3-methylaniline diazonium hexafluorophosphate is obtained, with a yield of 89.9%.

[0081] Example 10 Preparation of 2,3-difluorotoluene and lithium hexafluorophosphate

[0082] Put 282 g (1.00 mol) of 2-fluoro-3-methylaniline diazonium hexafluorophosphate into the reaction flask (the reaction flask is connected to a three-stage condenser, and the coolant is set at -10~-5°C), heat up to 160°C for decomposition reaction to obtain 2,3-difluorotoluene, phosphorus pentafluoride and nitrogen. After three-stage condensation separation, an oily substance and a mixed gas of phosphorus pentafluoride and nitrogen are obtained. The oily substance is distilled to obtain 2,3-difluorotoluene, with a yield of 92.7% and a purity of 99.4%. Control the temperature at -5°C, and introduce the mixed gas of phosphorus pentafluoride and nitrogen into the reactor containing 23.4 g of lithium fluoride (0.90 mol) and 850 g of hydrogen fluoride for about 3 h. After passing through, keep the temperature at -5°C for reaction for 4 h to obtain a lithium hexafluorophosphate hydrogen fluoride solution. Then cool down to -55°C for crystallization, control the temperature for filtration, and the hydrogen fluoride filtrate can be recycled 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 6 ppm, an acid value of 37 ppm. The ICP test results show that the contents of sodium, calcium, potassium, nickel, lead, zinc, chromium, magnesium, copper, zinc, and iron ions are all less than 3 ppm, the chloride ion content is 1.2 ppm, and the sulfate ion content is 9 ppm.

[0083] Example 11 Preparation of 2,3-difluorotoluene and lithium hexafluorophosphate

[0084] Charge 282 g (1.00 mol) of 2-fluoro-3-methylaniline diazonium hexafluorophosphate into a reaction flask (the reaction flask is connected to a three-stage condenser, and the coolant is set at -10~-5 °C), and heat up to 175 °C for decomposition reaction to obtain 2,3-difluorotoluene, phosphorus pentafluoride and nitrogen. After three-stage condensation separation, an oily substance and a mixed gas of phosphorus pentafluoride and nitrogen are obtained. The oily substance is distilled to obtain 2,3-difluorotoluene with a yield of 93.6% and a purity of 99.7%. While controlling the temperature at 0 °C, introduce the mixed gas of phosphorus pentafluoride and nitrogen into a reactor containing 23.4 g of lithium fluoride (0.90 mol) and 750 g of the filtrate of hydrogen fluoride from the previous batch for about 3 h. After passing through, keep the reaction at 0 °C for 5 h to obtain a lithium hexafluorophosphate hydrogen fluoride solution. Then cool down to -56 °C for crystallization, control the temperature for filtration, and the hydrogen fluoride filtrate can be recycled 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 water content is 4 ppm, the acid value is 26 ppm, and the ICP test results show that the contents of sodium, calcium, potassium, nickel, lead, zinc, chromium, magnesium, copper, zinc, and iron ions are all less than 3 ppm, the chloride ion content is 1.1 ppm, and the sulfate ion content is 6 ppm.

[0085] Example 12 Preparation of 2,3-difluorotoluene and lithium hexafluorophosphate solution

[0086] Charge 290.6 g (1.03 mol) of 2-fluoro-3-methylaniline diazonium hexafluorophosphate into a reaction flask (the reaction flask is connected to a three-stage condenser, and the coolant is set at -10~-5 °C), and heat up to 165 °C for decomposition reaction to obtain 2,3-difluorotoluene, phosphorus pentafluoride and nitrogen. After three-stage condensation separation, an oily substance and a mixed gas of phosphorus pentafluoride and nitrogen are obtained. The oily substance is distilled to obtain 2,3-difluorotoluene with a yield of 95.7% and a purity of 98.8%. Slowly introduce the mixed gas of phosphorus pentafluoride and nitrogen into a reactor containing 23.4 g of lithium fluoride (0.90 mol) and 550 g of ethylene glycol dimethyl ether, and react at 30 °C for 0.5 h. Filter to obtain a lithium hexafluorophosphate ethylene glycol dimethyl ether solution with a yield of 97.7% (yield of lithium hexafluorophosphate after conversion to pure form) and a content of 19.5%. The water content is 7 ppm, the acid value is 32 ppm, and the ICP test results show that the contents of sodium, calcium, potassium, nickel, lead, zinc, chromium, magnesium, copper, zinc, and iron ions are all less than 3 ppm, the chloride ion content is 1.1 ppm, and the sulfate ion content is 7 ppm.

[0087] Example 13 Preparation of 2,3-difluorotoluene and lithium hexafluorophosphate solution

[0088] 296.0 g (1.05 mol) of 2-fluoro-3-methylaniline diazonium hexafluorophosphate was charged into a reaction flask (the reaction flask was connected to a three-stage condenser, and the coolant was set at -10~-5 °C). The temperature was raised to 165 °C for decomposition reaction to obtain 2,3-difluorotoluene, phosphorus pentafluoride and nitrogen. After three-stage condensation separation, an oily substance and a mixed gas of phosphorus pentafluoride and nitrogen were obtained. 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 23.4 g of lithium fluoride (0.90 mol) and 1404 g of ethyl acetate and reacted at 20 °C for 3 h. The lithium hexafluorophosphate ethyl acetate solution was obtained by filtration with a yield of 97.1% (yield of lithium hexafluorophosphate in terms of pure substance), a content of 18.9%. The water content was 3 ppm, the acid value was 22 ppm, and the ICP test results showed that the contents of sodium, calcium, potassium, nickel, lead, zinc, chromium, magnesium, copper, zinc, and iron ions were all less than 3 ppm, the chloride ion content was 1.1 ppm, and the sulfate ion content was 7 ppm.

[0089] The above detailed description is a specific description of one of the feasible embodiments of the present invention. This embodiment is not intended to limit the patent scope of the present invention. Any equivalent implementation or change without departing from the present invention should be included within 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: ； ； Wherein, 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, and at least one of R1, R2, R3, R4 and R5 is fluorine.

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

3. 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.

4. 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.

5. 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.

6. 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.

7. The method according to claim 6, characterized in that The anhydrous hydrogen fluoride solution in step (2) is the filtrate obtained by filtration in claim 6.

8. 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.

9. 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.

10. 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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