Method for continuously preparing p-fluorophenol

Abstract

The invention discloses a method for continuously preparing p-fluorophenol, which comprises the following steps of: salifying p-fluoroaniline and dilute sulphuric acid in a first static mixer, diazotizing the salified solution and nitroso sulfuric acid in a second static mixer to form a diazonium salt solution, injecting the diazonium salt solution and an extracting solvent into a pressurized tower reactor for hydrolysis, according to the present invention, the reaction process is simple and efficient, the whole-process continuous production can be achieved, the production risk is low, the controllability is good, the three wastes are less, the pollution is less, the investment is low, the product p-fluorophenol is rapidly separated by using the thin film flash evaporation, and the method is suitable for industrial production. The thermal decomposition of the product under the condition of high temperature and long time is obviously reduced, the total yield of the prepared p-fluorophenol is 90% or above, and the purity is 99.5% or above.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of organic synthesis, and particularly relates to a method for continuously preparing 4-fluorophenol. BACKGROUND

[0002] 4-Fluorophenol, also known as 4-fluorophenol, has a molecular formula of , is a white to yellow solid, has a melting point of about 43-46 DEG C, and has a boiling point of about 185 DEG C. 4-Fluorophenol is an important chemical raw material and pharmaceutical intermediate, and can be used for synthesizing high-efficiency, low-toxicity and short-residual pesticides, herbicides, algicides and the like. 4-Fluorophenol can also be used for synthesizing various drugs, such as an intermediate for synthesizing broad-spectrum antibiotic cephalosporin, antibacterial drugs for treating intestinal diseases and the like, and can be used for synthesizing special liquid crystal materials.

[0003] At present, the synthesis methods of 4-fluorophenol are as follows: (1) taking p-fluoroaniline as a raw material: the p-fluoroaniline is diazotized, and then hydrolyzed in sulfuric acid solution to generate 4-fluorophenol. This method has a relatively simple process and easy-to-obtain raw materials, but the traditional method is a conventional kettle method, has high production cost, low yield, high impurity content in the product, and belongs to intermittent production, so the production efficiency is low and the market requirements cannot be met.

[0004] (2) taking p-chlorofluorobenzene or p-bromofluorobenzene as a raw material, hydrolyzing the p-chlorofluorobenzene or p-bromofluorobenzene in a strong alkaline solution under high temperature and high pressure to obtain 4-fluorophenol; although the yield of this reaction is high, the reaction needs to be carried out under high temperature and high pressure, the conditions are relatively harsh, in addition, the corrosion problem of the production equipment is also relatively serious, and the preparation cost is high.

[0005] (3) taking p-aminophenol as a raw material, diazotizing the p-aminophenol, adding fluoroboric acid into the diazonium salt solution to generate fluoroborate salt precipitate, taking out and drying the fluoroborate salt precipitate, and then heating and decomposing the fluoroborate salt precipitate to obtain 4-fluorophenol. Since the generated fluoroborate salt contains a hydroxyl group, the solubility in water is large, and the yield is low.

[0006] The above several synthesis processes of 4-fluorophenol have many defects and hidden dangers in safety, environmental protection, cost and product quality and the like. Therefore, it is of great significance to provide a synthesis method of 4-fluorophenol with high product yield and purity, low investment, low cost and small amount of three wastes. SUMMARY

[0007] To solve the above problems, the purpose of the present application is to provide a method for continuously preparing 4-fluorophenol.

[0008] To achieve the above purpose, the present application is implemented through the following technical scheme: A method for continuously preparing p-fluorophenol, p-fluoroaniline and dilute sulfuric acid are reacted to form a salt, then diazotization reaction with nitroso sulfuric acid, and then the diazonium salt solution and extraction solvent are injected into a pressurized column reactor for hydrolysis, wherein the pressurized column reactor is filled with mesoporous molecular sieve catalyst, and after hydrolysis, the reaction liquid is treated to obtain p-fluorophenol.

[0009] The mesoporous molecular sieve catalyst is prepared by the following method: The polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer is added to 2 mol / L hydrochloric acid, stirred and dissolved at 40°C, then dimethylformamide is added and stirred for 1 h, then sodium metasilicate nonahydrate and 3-mercaptopropyltrimethoxysilane are added, and stirred and reacted at 40°C for 4 h to obtain a mixed solution; copper sulfate pentahydrate and citric acid are added to deionized water, stirred and dissolved, then the mixed solution is added, and stirred and reacted at 40°C for 24 h; after the reaction is completed, it is transferred to a stainless steel reactor with a polytetrafluoroethylene lining, crystallized at 100°C for 24 h, removed and suction filtered to obtain the original powder molecular sieve, then the original powder molecular sieve is washed with anhydrous ethanol solution, dried at 60°C for 10 h, then added to 30% hydrogen peroxide solution, stirred at 25-30°C for 6 h, suction filtered, washed with 20% sulfuric acid, and finally dried at 60°C for 10 h to obtain the mesoporous molecular sieve catalyst.

[0010] The mass ratio of the polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, hydrochloric acid, dimethylformamide, sodium metasilicate nonahydrate, 3-mercaptopropyltrimethoxysilane, copper sulfate pentahydrate, citric acid, deionized water and hydrogen peroxide is 1:8-12:1-2:3-3.5:0.25-0.3:0.1-0.2:0.08-0.1:1-2:1-1.5.

[0011] The method for continuously preparing p-fluorophenol specifically comprises the following steps: 1) p-fluoroaniline and dilute sulfuric acid are pumped into a first static mixer by a metering pump to perform a salt formation reaction at 40-60°C, with a residence time of 4-10 s to obtain reaction liquid 1; 2) reaction liquid 1 prepared in step 1) and nitroso sulfuric acid are pumped into a second static mixer by a metering pump to perform a diazotization reaction at 20-40°C, with a residence time of 15-20 s to obtain reaction liquid 2; 3) reaction liquid 2 prepared in step 2) and an extraction solvent are pumped into a pressurized column reactor by a metering pump, wherein the pressurized column reactor is filled with a mesoporous molecular sieve catalyst, and hydrolysis is performed at 90-110°C and 0.3-0.8 MPa, with a reaction time of 2-5 min to obtain reaction liquid 3; 4) reaction liquid 3 prepared in step 3) is introduced into a continuous extraction column for extraction to obtain an extraction oil phase and an aqueous phase. 5) The extraction oil phase obtained in step 4) is introduced into a first thin film evaporator, the thin film evaporator is set to a temperature of 40-60 DEG C, and a vacuum degree of 100-200 mbar, and the reaction solution is concentrated under reduced pressure to obtain an evaporation liquid and a mother liquor; 6) The mother liquor obtained in step 5) is introduced into a second thin film evaporator, the thin film evaporator is set to a temperature of 100-120 DEG C, and a vacuum degree of 10-30 mbar, and the mother liquor is concentrated under reduced pressure to obtain the p-fluorophenol.

[0012] The mass concentration of the dilute sulfuric acid in step 1) is 20-30%, and the mass ratio of the p-fluoroaniline to the dilute sulfuric acid is 1:5-8.

[0013] The molar ratio of the nitroso sulfuric acid to the p-fluoroaniline in step 1) in step 2) is 1-1.2:1.

[0014] The extraction solvent in step 3) is one or both of dichloroethane and dichloromethane.

[0015] The mass ratio of the extraction solvent to the p-fluoroaniline in step 1) in step 3) is 2-4:1.

[0016] The synthesis route of the p-fluorophenol of the present application is as follows:

[0017] Compared with the prior art, the present application has the following advantages: The continuous preparation method of the p-fluorophenol of the present application uses a tubular reactor to perform the diazotization reaction, has less investment, large flux, is more suitable for large-scale production, and the p-fluorophenol has a certain solubility in water and is easy to have an azo side reaction with the diazonium salt, so it needs to be extracted and separated in time by using an organic solvent, which further requires that the reaction system has a good mixing effect, the boiling point of the system is reduced after the organic solvent is added, and the reaction needs to be performed under pressure, the pressure tower reactor can meet the requirement of a relatively long residence time for hydrolysis, and can be filled with mesoporous molecular sieve catalyst to accelerate the reaction process, the built-in mixing structure helps to strengthen the mass transfer, and can adapt to the pressure operation condition, so it is an ideal device selection for realizing the reaction.

[0018] The continuous preparation method of the p-fluorophenol of the present application, due to the strong electron-withdrawing effect of fluorine, the hydrolysis reaction rate of the p-fluoroaniline diazonium salt is slow, the mesoporous molecular sieve catalyst not only contains copper, but also contains a proton acid center on the surface, the water nucleophilicity is enhanced by coordinating and polarizing the water molecules, the intermediate benzene cation is stabilized, the catalytic effect is better, the reaction activation energy can be effectively reduced, the hydrolysis can be performed under more mild and faster conditions, the amount of sulfuric acid can be reduced, the catalyst can be used continuously for a long time, and the method is more environmentally friendly.

[0019] The present application adopts a pressurized column reactor and uses a mesoporous molecular sieve catalyst, greatly reduces the occurrence of side reactions, significantly improves the product yield, and the optimized reaction conditions reduce the difficulty of subsequent purification - only through a scraped film evaporator, the organic solvent and p-fluorophenol can be quickly and efficiently separated and evaporated, and the product p-fluorophenol is quickly separated by film flash evaporation, significantly reducing the thermal decomposition of the product under high temperature and long time conditions, greatly improving the overall process efficiency, and the water phase obtained by hydrolysis separation can be completely recycled by a continuous extraction process. Organic matter such as p-fluorophenol, after sulfuric acid content detection, the water phase can be directly recycled for the salt formation reaction of p-fluoroaniline, thereby significantly reducing the amount of wastewater generated during production.

[0020] The present application has the advantages of simple and efficient reaction process, simple post-treatment, high yield and purity, low production cost, less waste, low operation risk, strong process controllability, etc., and can be adapted to a continuous production mode, and has significant comprehensive benefits. The total yield of p-fluorophenol prepared is more than 90%, and the purity is more than 99.5%. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 The present application is a continuous process for preparing p-fluorophenol. DETAILED DESCRIPTION

[0022] In order to better understand the technical solutions of the present application, the above content of the present application will be further explained in the form of examples, but it should not be understood that the scope of the above subject matter of the present application is limited to the following examples. Any technology realized based on the above content of the present application belongs to the scope of the present application.

[0023] Example 1: Preparation of mesoporous molecular sieve catalyst 40g of polyethylene oxide-polypropylene oxide-polyethylene oxide triblock polymer was added to 320g of 2mol / L hydrochloric acid, and after stirring and dissolving at 40℃, 40g of dimethylformamide was added and stirred for 1h, then 120g of sodium metasilicate nonahydrate and 10g of 3-mercaptopropyltrimethoxysilane were added, and stirred and reacted at 40℃ for 4h to obtain a mixed solution; 4g of copper sulfate pentahydrate and 3.2g of citric acid were added to 40g of deionized water, stirred and dissolved, then added to the mixed solution, and stirred and reacted at 40℃ for 24h; after the reaction was completed, it was transferred to a stainless steel reaction kettle with a polytetrafluoroethylene liner, crystallized at 100℃ for 24h, and then removed and filtered to obtain the original powder molecular sieve; the original powder molecular sieve was washed with anhydrous ethanol solution by reflux, dried at 60℃ for 10h, then added to 40g of 30% mass concentration hydrogen peroxide solution, stirred at 25℃ for 6h, filtered, washed with 20% mass concentration sulfuric acid, and finally dried at 60℃ for 10h to obtain the mesoporous molecular sieve catalyst.

[0024] Example 2: Preparation of mesoporous molecular sieve catalysts: 40g of polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer was added to 400g of 2mol / L hydrochloric acid and stirred at 40℃ until dissolved. Then, 60g of dimethylformamide was added and stirred for 1 hour. Finally, 128g of sodium metasilicate nonahydrate and 11g of [unspecified substance] were added. 3-Mercaptopropyltrimethoxysilane was stirred at 40°C for 4 hours to obtain a mixed solution. 6g of copper sulfate pentahydrate and 3.6g of citric acid were added to 60g of deionized water and stirred until dissolved. This solution was then added to the mixed solution and stirred at 40°C for 24 hours. After the reaction was complete, the mixture was transferred to a stainless steel reactor with a polytetrafluoroethylene liner and crystallized at 100°C for 24 hours. The mixture was then removed and filtered to obtain the original molecular sieve powder. The original molecular sieve powder was then refluxed with anhydrous ethanol solution, dried at 60°C for 10 hours, and then added to 45g of 30% hydrogen peroxide solution. The mixture was stirred at 26°C for 6 hours, filtered, washed with 20% sulfuric acid solution, and finally dried at 60°C for 10 hours to obtain the mesoporous molecular sieve catalyst.

[0025] Example 3: Preparation of mesoporous molecular sieve catalysts: 40g of polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer was added to 480g of 2mol / L hydrochloric acid and stirred at 40℃ until dissolved. Then, 80g of dimethylformamide was added and stirred for 1 hour. Finally, 140g of sodium metasilicate nonahydrate and 12g of [unspecified substance] were added. 3-Mercaptopropyltrimethoxysilane was stirred at 40°C for 4 hours to obtain a mixed solution. 8g of copper sulfate pentahydrate and 4g of citric acid were added to 80g of deionized water, stirred to dissolve, and then added to the mixed solution. The mixture was stirred at 40°C for 24 hours. After the reaction was completed, the mixture was transferred to a stainless steel reactor with a polytetrafluoroethylene liner and crystallized at 100°C for 24 hours. The mixture was then removed and filtered to obtain the original molecular sieve powder. The original molecular sieve powder was then washed with anhydrous ethanol solution under reflux and dried at 60°C for 10 hours. It was then added to 60g of 30% hydrogen peroxide solution and stirred at 30°C for 6 hours. The mixture was then filtered, washed with 20% sulfuric acid solution, and finally dried at 60°C for 10 hours to obtain the mesoporous molecular sieve catalyst.

[0026] Example 4: Preparation of p-fluorophenol: 555.6 g of p-fluoroaniline and 2778 g of 30% dilute sulfuric acid were metered into the first static mixer and subjected to a salt-forming reaction at 40°C for 4 s to obtain reaction solution 1. Reaction solution 1 and 1585 g of 40% pure nitrososulfuric acid were metered into the second static mixer and subjected to a diazotization reaction at 20°C for 15 s to obtain reaction solution 2. Reaction solution 2 and 1112 g of dichloroethane were metered into a pressurized tower reactor, which was filled with the mesoporous material prepared in Example 1. The catalyst was hydrolyzed at 90℃ and 0.3 MPa for 2 min to obtain reaction solution 3. Reaction solution 3 was then introduced into a continuous extraction tower for extraction, yielding an extractable oil phase and an aqueous phase. The extracted oil phase was then passed into a first thin-film evaporator at 40℃ and a vacuum of 100 mbar to concentrate the reaction solution under reduced pressure, yielding an evaporator and a mother liquor. The mother liquor was then passed into a second thin-film evaporator at 100℃ and a vacuum of 10 mbar to concentrate the mother liquor under reduced pressure, yielding p-fluorophenol. The overall yield of p-fluorophenol prepared was 91.8%, and the purity was 99.7%.

[0027] Example 5: Preparation of p-fluorophenol: 555.6 g of p-fluoroaniline and 3333 g of 28% dilute sulfuric acid were metered into the first static mixer and subjected to a salt-forming reaction at 45°C for 6 s to obtain reaction solution 1. Reaction solution 1 and 1750 g of 40% nitrososulfuric acid were metered into the second static mixer and subjected to a diazotization reaction at 25°C for 16 s to obtain reaction solution 2. Reaction solution 2 and 1666.8 g of dichloromethane were metered into a pressurized tower reactor, which was filled with the mesoporous material prepared in Example 2. The catalyst was hydrolyzed at 100℃ and 0.4 MPa for 3 min to obtain reaction solution 3. Reaction solution 3 was then introduced into a continuous extraction tower for extraction, yielding an extractable oil phase and an aqueous phase. The extracted oil phase was then passed into a first thin-film evaporator at 50℃ and a vacuum of 120 mbar to concentrate the reaction solution under reduced pressure, yielding an evaporator and a mother liquor. The mother liquor was then passed into a second thin-film evaporator at 105℃ and a vacuum of 20 mbar to concentrate the mother liquor under reduced pressure, yielding p-fluorophenol. The total yield of p-fluorophenol prepared was 92.3%, and the purity was 99.8%.

[0028] Example 6 Preparation of p-fluorophenol: 555.6 g of p-fluoroaniline and 3000 g of 25% dilute sulfuric acid were metered into the first static mixer and subjected to a salt-forming reaction at 50°C for 8 s to obtain reaction solution 1. Reaction solution 1 and 1826 g of 40% pure nitrososulfuric acid were metered into the second static mixer and subjected to a diazotization reaction at 30°C for 18 s to obtain reaction solution 2. Reaction solution 2 and 1945 g of dichloroethane were metered into a pressurized tower reactor, which was filled with the mesoporous molecules prepared in Example 2. The catalyst was screened and hydrolyzed at 105℃ and 0.6MPa for 4 min to obtain reaction solution 3. Reaction solution 3 was then introduced into a continuous extraction tower for extraction, yielding an extractable oil phase and an aqueous phase. The extracted oil phase was then passed into a first thin-film evaporator at 55℃ and a vacuum of 150 mbar to concentrate the reaction solution under reduced pressure, yielding an evaporator and a mother liquor. The mother liquor was then passed into a second thin-film evaporator at 110℃ and a vacuum of 25 mbar to concentrate the mother liquor under reduced pressure, yielding p-fluorophenol. The total yield of p-fluorophenol prepared was 92.8%, and the purity was 99.9%.

[0029] Example 7 Preparation of p-fluorophenol: 555.6 g of p-fluoroaniline and 4440 g of 20% dilute sulfuric acid were metered into the first static mixer and subjected to a salt-forming reaction at 60°C for 10 s to obtain reaction solution 1. Reaction solution 1 and 1900 g of 40% nitrososulfuric acid were metered into the second static mixer and subjected to a diazotization reaction at 40°C for 20 s to obtain reaction solution 2. Reaction solution 2 and 2222 g of dichloromethane were metered into a pressurized tower reactor, which was filled with the mesoporous material prepared in Example 3. The catalyst was hydrolyzed at 110℃ and 0.8 MPa for 5 min to obtain reaction solution 3. Reaction solution 3 was then introduced into a continuous extraction tower for extraction, yielding an extractable oil phase and an aqueous phase. The extracted oil phase was then passed into a first thin-film evaporator at 60℃ and a vacuum of 200 mbar to concentrate the reaction solution under reduced pressure, yielding an evaporator and a mother liquor. The mother liquor was then passed into a second thin-film evaporator at 120℃ and a vacuum of 30 mbar to concentrate the mother liquor under reduced pressure, yielding p-fluorophenol. The total yield of p-fluorophenol prepared was 92.1%, with a purity of 99.8%.

[0030] Comparative Example 1: 555.6 g of p-fluoroaniline and 3000 g of 25% dilute sulfuric acid were metered into a first static mixer and subjected to a salt-forming reaction at 50°C for 8 s to obtain reaction solution 1. Reaction solution 1 and 1826 g of 40% pure nitrososulfuric acid were metered into a second static mixer and subjected to a diazotization reaction at 30°C for 18 s to obtain reaction solution 2. Reaction solution 2 and 1945 g of dichloroethane were metered into a pressurized tower reactor (without a catalyst). Hydrolysis was carried out at 105℃ and 0.6MPa for 4 min to obtain reaction solution 3. Reaction solution 3 was then introduced into a continuous extraction tower for extraction, yielding an extractable oil phase and an aqueous phase. The extracted oil phase was then passed into a first thin-film evaporator at 55℃ and a vacuum of 150 mbar to concentrate the reaction solution under reduced pressure, yielding an evaporator and a mother liquor. The mother liquor was then passed into a second thin-film evaporator at 110℃ and a vacuum of 25 mbar to concentrate the mother liquor under reduced pressure, yielding p-fluorophenol. The total yield of p-fluorophenol prepared was 52.8%, with a purity of 95.6%. In this comparative example, no mesoporous molecular sieve catalyst was used, and the sulfuric acid concentration was low, resulting in incomplete reaction within a short time, leading to lower yield and purity.

[0031] Comparative Example 2: 555.6 g of p-fluoroaniline and 3000 g of 25% dilute sulfuric acid were metered into the first static mixer and subjected to a salt formation reaction at 50°C for 8 s, yielding reaction solution 1. Reaction solution 1 and 1826 g of 40% pure nitrososulfuric acid were metered into the second static mixer and subjected to a diazotization reaction at 30°C for 18 s, yielding reaction solution 2. Reaction solution 2 and 1945 g of dichloroethane were metered into a pressurized tower reactor (without a catalyst). Hydrolysis was carried out at 110℃ and 0.6MPa for 40 min to obtain reaction solution 3. Reaction solution 3 was then introduced into a continuous extraction tower for extraction, yielding an oil phase and an aqueous phase. The obtained oil phase was then passed into a first thin-film evaporator at 55℃ and a vacuum of 150 mbar to concentrate the reaction solution under reduced pressure, yielding an evaporator and a mother liquor. The mother liquor was then passed into a second thin-film evaporator at 110℃ and a vacuum of 25 mbar to concentrate the mother liquor under reduced pressure, yielding p-fluorophenol. The total yield of p-fluorophenol prepared was 83.6%, with a purity of 98.2%. In this comparative example, no mesoporous molecular sieve catalyst was used, and the sulfuric acid concentration was low. Even with extended reaction time until complete reaction, the yield and purity remained relatively low.

[0032] Comparative Example 3: 555.6 g of p-fluoroaniline and 3000 g of 45% dilute sulfuric acid were metered into the first static mixer and subjected to a salt formation reaction at 50°C for 8 s to obtain reaction solution 1. Reaction solution 1 and 1826 g of 40% nitrososulfuric acid were metered into the second static mixer and subjected to a diazotization reaction at 30°C for 18 s to obtain reaction solution 2. Reaction solution 2 and 1945 g of dichloroethane were metered into a pressurized tower reactor (without a catalyst). Hydrolysis was carried out at 110℃ and 0.6MPa for 40 min to obtain reaction solution 3. Reaction solution 3 was then introduced into a continuous extraction tower for extraction, yielding an oil phase and an aqueous phase. The obtained oil phase was then passed into a first thin-film evaporator at 55℃ and a vacuum of 150 mbar to concentrate the reaction solution under reduced pressure, yielding an evaporator and a mother liquor. The mother liquor was then passed into a second thin-film evaporator at 110℃ and a vacuum of 25 mbar to concentrate the mother liquor under reduced pressure, yielding p-fluorophenol. The total yield of p-fluorophenol prepared was 88.0%, with a purity of 99.3%. In this comparative example, a mesoporous molecular sieve catalyst was not used, but the amount of sulfuric acid was increased, and the reaction time was extended to complete reaction, resulting in slightly lower yield and purity.

[0033] As can be seen from the above examples and comparative examples, the use of mesoporous molecular sieve catalysts can greatly improve the yield and purity of the products, effectively reduce the activation energy of the reaction, and enable hydrolysis under milder and faster conditions. At the same time, it can reduce the amount of sulfuric acid used, and the catalyst can be used continuously for a long time, making it more environmentally friendly.

[0034] While the specific embodiments of the present invention have been described above, they are not intended to limit the scope of protection of the present invention. Based on the technical solutions of the present invention, various modifications or variations that can be made by those skilled in the art without creative effort are still within the scope of protection of the present invention.

Claims

1. A method for the continuous preparation of p-fluorophenol, characterized in that: After reacting with dilute sulfuric acid to form a salt, p-fluoroaniline undergoes a diazotization reaction with nitrososulfuric acid. The diazonium salt solution and extraction solvent are then injected into a pressurized tower reactor for hydrolysis. The pressurized tower reactor is filled with a mesoporous molecular sieve catalyst. After hydrolysis, the reaction solution is post-treated to obtain p-fluorophenol.

2. The method for continuous preparation of p-fluorophenol as described in claim 1, characterized in that: The mesoporous molecular sieve catalyst was prepared according to the following method: A triblock copolymer of polyethylene oxide-polypropylene oxide-polyethylene oxide was added to 2 mol / L hydrochloric acid and stirred at 40 °C to dissolve. Dimethylformamide was then added and stirred for 1 h. Sodium metasilicate nonahydrate and 3-mercaptopropyltrimethoxysilane were added and stirred at 40 °C for 4 h to obtain a mixed solution. Copper sulfate pentahydrate and citric acid were added to deionized water and stirred to dissolve. This solution was then added to the mixed solution and stirred at 40 °C for 24 h. After the reaction was completed, the solution was transferred to a stainless steel reactor with a polytetrafluoroethylene liner and crystallized at 100 °C for 24 h. The solution was then removed and filtered to obtain the original molecular sieve powder. The original molecular sieve powder was then washed with anhydrous ethanol solution under reflux and dried at 60 °C for 10 h. It was then added to 30% hydrogen peroxide solution and stirred at 25-30 °C for 6 h. The solution was then filtered, washed with 20% sulfuric acid solution, and finally dried at 60 °C for 10 h to obtain the mesoporous molecular sieve catalyst.

3. The method for continuous preparation of p-fluorophenol as described in claim 2, characterized in that: The mass ratio of the polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, hydrochloric acid, dimethylformamide, sodium metasilicate nonahydrate, 3-mercaptopropyltrimethoxysilane, copper sulfate pentahydrate, citric acid, deionized water, and hydrogen peroxide is 1:8~12:1~2:3~3.5:0.25~0.3:0.1~0.2:0.08~0.1:1~2:1~1.

5.

4. The method for continuous preparation of p-fluorophenol as described in claim 3, characterized in that: Specifically, the following steps are included: 1) P-fluoroaniline and dilute sulfuric acid are pumped into the first static mixer via a metering pump and a salt-forming reaction is carried out at 40~60℃ for a residence time of 4~10s to obtain reaction solution 1; 2) The reaction solution 1 prepared in step 1) and nitrososulfuric acid are pumped into the second static mixer by a metering pump and diazotization reaction is carried out at 20~40℃ for a residence time of 15~20s to obtain reaction solution 2. 3) The reaction solution 2 prepared in step 2) and the extraction solvent are pumped into a pressurized tower reactor via a metering pump. The pressurized tower reactor is filled with a mesoporous molecular sieve catalyst and hydrolyzed at 90~110℃ and 0.3~0.8MPa for 2~5min to obtain reaction solution 3. 4) The reaction solution 3 prepared in step 3) is introduced into a continuous extraction tower for extraction to obtain an oil phase and an aqueous phase; 5) Pass the extracted oil phase obtained in step 4) into the first thin film evaporator, set the temperature of the thin film evaporator to 40~60℃ and the vacuum degree to 100~200mbar, concentrate the reaction liquid under reduced pressure to obtain the evaporated liquid and the mother liquor; 6) Pass the mother liquor obtained in step 5) into the second thin film evaporator, set the temperature of the thin film evaporator to 100~120℃ and the vacuum degree to 10~30mbar, concentrate the mother liquor under reduced pressure, and the resulting distillate is p-fluorophenol.

5. The method for continuous preparation of p-fluorophenol as described in claim 4, characterized in that: The mass concentration of the dilute sulfuric acid in step 1) is 20-30%, and the mass ratio of p-fluoroaniline to dilute sulfuric acid is 1:5-8.

6. The method for continuous preparation of p-fluorophenol as described in claim 4, characterized in that: The molar ratio of nitrososulfuric acid in step 2) to p-fluoroaniline in step 1) is 1~1.2:

1.

7. The method for continuous preparation of p-fluorophenol as described in claim 4, characterized in that: The extraction solvent mentioned in step 3) is one or both of dichloroethane and dichloromethane.

8. The method for continuous preparation of p-fluorophenol as described in claim 4, characterized in that: The mass ratio of the extraction solvent in step 3) to p-fluoroaniline in step 1) is 2-4:1.

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