Clean production method of oxyfluorfen

Abstract

The application discloses a clean production method of oxyfluorofenner, recycles 2-chloro-4-trifluoromethyl phenol potassium by-product existing in a double etherization method process, and applies the by-product to synthesis of oxyfluorofenner, integrates a process route, opens up a new synthesis path, and solves the problem that the double etherization method by-product 2-chloro-4-trifluoromethyl phenol cannot be effectively utilized in the prior art method. Further exploration is made on recycling and utilization of 2-chloro-5-trifluoromethyl phenol potassium by-product and recycling of solvents in each step, atom economy of the process is significantly improved, process cost is reduced, yield of the target product oxyfluorofenner is improved, the method is environment-friendly, and is suitable for industrial production.

Description

Technical Field

[0001] This invention relates to the technical field of herbicide preparation methods, specifically to a clean production method for ethoxyflufen. Background Technology

[0002] Oxyfluorfen is a contact herbicide developed in 1975 by Rohm and Haas (now Dow Chemical Company). Its chemical name is 2-chloro-4-trifluoromethylphenyl-4'-nitro-3'-ethoxyphenyl ether, and its chemical structure is as follows:

[0003] Among the reported methods for preparing ethoxyflufenicol both domestically and internationally, the most common synthetic route is the dietherification method (US4093446, US4419122, CN1363548A, etc.). Using the dietherification route to produce ethoxyflufenicol effectively controls the content of isomers and impurities in the product, increasing the product content by approximately 3%-5%. The dietherification intermediate has a high activation energy during nitration, making the nitration reaction easier and more energy-efficient. The reaction conditions are mild and easily controlled, improving operational safety.

[0004]

[0005] However, the production of ethoxyfluorfen via the dietherification process inevitably generates an equivalent amount of the byproduct potassium 2-chloro-4-trifluoromethylphenol, resulting in high consumption of the raw material 3,4-dichlorotrifluorotoluene. Furthermore, the potassium 2-chloro-4-trifluoromethylphenol salt in the wastewater is unstable, as the trifluoromethyl group readily hydrolyzes to produce hydrogen fluoride, generating a strong, pungent odor. This process exhibits poor atom economy and significant environmental impact. Currently, there is no effective method to utilize the byproduct 2-chloro-4-trifluoromethylphenol from the dietherification process (CN1363548A, CN101891623A, CN102030655A, CN103980127A).

[0006] Zhejiang Heben Technology Co., Ltd. (CN112094193A) disclosed a reaction of 3,4-dichlorotrifluorotoluene, 2,4-difluoronitrobenzene, and potassium hydroxide to obtain a diether intermediate, followed by alcoholysis of the dietherified intermediate under potassium hydroxide and ethanol conditions to obtain ethoxyflufenicol.

[0007] This process avoids the generation of isomers in the dietherification process and has a higher yield, but it still cannot solve the problem of byproduct 2-chloro-4-trifluoromethylphenol.

[0008] Our previous patent (CN111470951A) reported the preparation of potassium 2-chloro-4-trifluoromethylphenol from 3,4-dichlorotrifluorotoluene as a raw material, followed by reaction with 2,4-dihalonitrobenzene to prepare a diether intermediate, and then alcoholysis to prepare ethoxyflumethrin. This method reduces the production cost by replacing resorcinol with the relatively inexpensive 2,4-dihalonitrobenzene. However, compared with CN112094193A, this method of preparing potassium 2-chloro-4-trifluoromethylphenol from 3,4-dichlorotrifluorotoluene extends the process route, and does not disclose an effective method for recovering and treating potassium 2-chloro-4-trifluoromethylphenol in the system after the reaction.

[0009]

[0010] Meanwhile, the inventors noted that isomers are inevitably generated during the dietherification process. After alcoholysis, the isomer potassium 2-chloro-5-trifluoromethylphenol is produced as a byproduct. Existing technologies lack methods for recycling potassium 2-chloro-5-trifluoromethylphenol. Addressing the shortcomings of the dietherification process, which results in the inability to recycle potassium 2-chloro-4-trifluoromethylphenol and potassium 2-chloro-5-trifluoromethylphenol byproducts, poor atom economy, and high costs, this invention discloses a clean production method for ethoxyflufenicol. Summary of the Invention

[0011] The purpose of this invention is to overcome the shortcomings of the existing double etherification process, which has the disadvantages of the inability to recover and utilize the byproducts 2-chloro-4-trifluoromethylphenol and 2-chloro-5-trifluoromethylphenol, resulting in poor atom economy and high cost. This invention provides a clean production method for ethoxyflufenicol, which achieves comprehensive utilization of resources and improves yield.

[0012] A clean production method for ethoxyflufenicol according to the present invention includes the following steps:

[0013] (1) Condensation process

[0014] An organic solvent was added to a condensation vessel, along with resorcinol and potassium hydroxide. The mixture was refluxed to remove water, yielding a potassium resorcinol solution. The solution was then heated, and 3,4-dichlorotrifluorotoluene was added. The mixture was heated and maintained at this temperature to yield the dietherified condensate and its isomers, as shown in the following reaction formula:

[0015]

[0016] (2) Nitrification process

[0017] The dietherified condensate and its isomers prepared in step (1) are introduced into a microreactor with sulfuric acid and nitric acid in a certain proportion to obtain the nitration product and its isomers. The reaction formula is as follows:

[0018]

[0019] (3) Alcoholization process

[0020] The nitration product and its isomers prepared in step (2) were subjected to alcoholysis in the presence of ethanol and KOH to obtain the main product ethoxyflufenoxam and the byproducts 2-chloro-4-trifluoromethylphenol potassium and 2-chloro-5-trifluoromethylphenol potassium, as shown in the following reaction formula:

[0021]

[0022] (4) Preparation process of 2,4-dichloronitrobenzene

[0023] m-Dichlorobenzene, sulfuric acid, and nitric acid are added to a nitration reactor, and a continuous nitration reaction is carried out to obtain 2,4-dichloronitrobenzene, as shown in the following reaction formula:

[0024]

[0025] (5) Nitration product synthesis process

[0026] The byproducts 2-chloro-4-trifluoromethylphenol potassium and 2-chloro-5-trifluoromethylphenol potassium from step (3) are reacted with the 2,4-dichloronitrobenzene prepared in step (4) to prepare the nitration product, as shown in the following reaction formula:

[0027]

[0028] Alternatively, the byproducts potassium 2-chloro-4-trifluoromethylphenol and potassium 2-chloro-5-trifluoromethylphenol from step (3) can be acidified to convert them into 2-chloro-4-trifluoromethylphenol and 2-chloro-5-trifluoromethylphenol, and then reacted with the 2,4-dichloronitrobenzene prepared in step (4) in the presence of potassium carbonate to prepare the nitrated product, as shown in the following reaction formula:

[0029]

[0030] (6) Repeat the alcoholysis process of step (3) with the nitration product and nitration product isomer prepared in step (5) to prepare ethoxyflufenoxam, and recover the by-products potassium 2-chloro-4-trifluoromethylphenol and potassium 2-chloro-5-trifluoromethylphenol for use in step (5).

[0031] According to the aforementioned clean production method of the present invention, in step (1), the organic solvent is dimethyl sulfoxide (DMSO), which may optionally include a dehydrated reflux solvent (toluene) and a desolventized recovered solvent (toluene and DMSO).

[0032] The specific operation of the reflux dehydration is as follows: turn on the vacuum, heat to reflux, dehydrate until no water droplets are generated, and the solvent (toluene / water mixture) refluxed is cooled by primary circulating water and primary cold brine, and then recovered to the water separator. After water separation, the toluene is reused in the next batch step (1).

[0033] In step (1), the specific operation for preparing the dietherified condensate and its isomers is as follows: the feed solution is heated to 120°C, the toluene recovered by desolventizing is used for the synthesis of potassium phenolate, then 3,4-dichlorotrifluorotoluene is added dropwise, the temperature is raised to 150°C and held for 10 hours, then cooled to 50°C, and the material is separated by potassium chloride pressure filtration using a pressure filter dryer. The filtrate is desolventized to obtain a mixture of the dietherified condensate and its isomers. The dimethyl sulfoxide obtained by desolventizing is used for the synthesis of potassium phenolate and / or subsequent synthesis steps. Dichloroethane is added to the mixture of the condensate and its isomers, and after dissolution, 4% liquid alkali is added for extraction and separation. The aqueous layer is acidified with 30% hydrochloric acid to obtain a small amount of mono-terminated phenol impurities. The organic layer is decolorized with activated carbon, and pressure filtration is used to obtain a purified dichloroethane solution of the dietherified condensate and its isomers.

[0034] In the reflux dehydration step (1) of this invention, dimethyl sulfoxide is used as the solvent and toluene as the dehydrating agent. Both dimethyl sulfoxide and toluene can be recycled. The conversion rate of resorcinol (to form potassium phenolate) is 100%, the conversion rate of potassium phenolate (to form a condensate) is greater than or equal to 80%, and the conversion rate of potassium phenolate (to form a condensate isomer) is about 15%.

[0035] According to the aforementioned clean production method of the present invention, in step (2), the reaction temperature of the nitration reaction is 40-50°C. After the reaction is complete, the nitrated liquid and acid liquid are separated by a liquid-phase centrifuge. The acid liquid is used for acid concentration pretreatment. The nitrated liquid is then washed with water and alkali to obtain the nitrated product. The obtained nitrated product is dissolved in a quantitative amount of toluene and water is removed to obtain a toluene nitrated product solution, which is used in the alcoholysis step (3). The conversion rate of the condensate (generating nitrate) is 99%; the conversion rate of the condensate (isomer) (generating nitrate (isomer A)) is 18.4%; and the conversion rate of the side reaction (generating nitrate (isomer B)) is 78.4%. The molar yield of the nitrate is 99%, and the molar yield of the nitrate (isomer A) is 18.4%.

[0036] According to the aforementioned clean production method of the present invention, step (3) is specifically operated as follows: After adding a quantitative amount of ethanol to the potassium alkoxide reactor, stirring is started, and the temperature of the cold brine is lowered to below 10°C. Potassium hydroxide is added, and after the addition is completed, the temperature is kept below 30°C. After 2 hours, the potassium hydroxide is completely dissolved and kept warm for later use. Then, a measured amount of toluene nitration product solution is added to the alcoholysis reactor, the temperature is raised to 35°C, and the prepared potassium alkoxide solution is added dropwise (to be completed in about 2 hours). After the addition is completed, the temperature is kept at 45°C for 4 hours. After the sample is qualified, it is transferred to the cooling reactor, cooled to 15°C, washed and extracted with water, and the organic layer is transferred to the decolorization reactor. Activated carbon is added for decolorization. After decolorization, it is continuously transferred to the falling film evaporator for decolorization and the internal decolorization reactor for decolorization and recovery of the solvent toluene. After desolvation is completed, it is transferred to the recrystallization reactor for the dissolution and crystallization process. Petroleum ether is added, and when the temperature inside the reactor drops to below 5°C, it is centrifuged. The mother liquor from the centrifugation is desolvated and the petroleum ether is recovered. The filter cake is dried to obtain the product ethoxyfluorfen, which is then packaged and stored. The aqueous layer was continuously acidified with 30% hydrochloric acid, and after distillation and dehydration, 2-chloro-4-trifluoromethylphenol and 2-chloro-5-trifluoromethylphenol byproducts were obtained, which were used in the nitration product synthesis process of step (5). The conversion rate of the nitrate (to generate ethoxyflufenicol) was 99.5%; the conversion rate of the nitrate (isomer A) (to generate ethoxyflufenicol) was 99.5%. The molar yield of ethoxyflufenicol was 83%.

[0037] According to the aforementioned clean production method of the present invention, step (4) is specifically operated as follows: m-Dichlorobenzene, sulfuric acid, and nitric acid are quantitatively added to the nitration reactor to carry out the nitration reaction. The reaction temperature is maintained below 40°C throughout the process. After the reaction is complete, the mixture enters the sedimentation separation stage. The acid layer is extracted, and the organic layer is washed. Dichloroethane is added to the acid layer for extraction. The extracted organic layer is desolventized using a primary circulating water cooling system and a primary cold brine cooling system, operating at atmospheric pressure. The dichloroethane solvent is condensed and recovered. After solvent removal, 2,4-dichloronitrobenzene is obtained for use in the nitration product synthesis process of step (5). The organic layer obtained from the sedimentation separation is washed with 10% liquid alkali and fresh water. The washed organic layer is dehydrated, and 2,4-dichloronitrobenzene is obtained for use in the nitration product synthesis process of step (5). In this step, the conversion rate of m-dichlorobenzene (to generate 2,4-dichloronitrobenzene) is 99%, and the conversion rate of the side reaction (to generate 1,5-dichloro-2,4-dinitrobenzene) is 0.5%.

[0038] According to the aforementioned clean production method of the present invention, step (5) is specifically operated as follows: fresh dimethyl sulfoxide and / or dimethyl sulfoxide and 2,4-dichloronitrobenzene obtained from the desolventizing step (1) are added into a synthesis reactor, stirred, potassium carbonate is added, and then 2-chloro-4-trifluoromethylphenol and 2-chloro-5-trifluoromethylphenol byproducts obtained from step (3) are added. The temperature is raised to 100°C and kept at this temperature for 10 hours. After the sample is qualified, the temperature is lowered to below 50°C and desalted in a pressure filter drying machine. The filtrate is desolventized and DMSO is recovered to obtain the nitration product. The nitration product is dissolved in toluene and prepared into a toluene nitration product solution for the alcoholysis process in step (3). The conversion rate of 2,4-dichloronitrobenzene (generating nitrate) is 88%, the conversion rate of 2,4-dichloronitrobenzene (generating nitrate (isomer A)) is 9.5%, and the conversion rate of the side reaction (generating nitrate (isomer B)) is 2%. The molar yield of the nitrate was 82.5%, and the molar yield of the nitrate (isomer A) was 9.0%.

[0039] Compared with existing technologies, the present invention has the following significant advantages:

[0040] This invention conducts an in-depth study of the process for preparing ethoxyflufenicol via a dietherification reaction. It recovers the potassium 2-chloro-4-trifluoromethylphenol byproduct present in the dietherification process and applies it to the synthesis of ethoxyflufenicol, integrating the process route and opening up a new synthetic pathway. This solves the problem that existing techniques cannot effectively utilize the 2-chloro-4-trifluoromethylphenol byproduct of the dietherification process. Further exploration of the recovery and utilization of the potassium 2-chloro-5-trifluoromethylphenol byproduct and the solvents in each step significantly improves the atom economy of the process, reduces process costs, increases the yield of the target product ethoxyflufenicol, and is environmentally friendly, making it suitable for industrial production. Detailed Implementation

[0041] The present invention will be further described in detail below with reference to specific embodiments. Unless otherwise specified, the methods used herein are conventional methods in the art, and the reagents used are readily available from conventional commercial sources and / or prepared according to known synthetic methods.

[0042] Example 1: Condensation Process

[0043]

[0044] A specific amount of dimethyl sulfoxide (DMSO) solvent is added to a condensation reactor, followed by resorcinol, potassium hydroxide, dehydrated reflux solvent (toluene), and recovered solvent (toluene and DMSO). A vacuum is established, and the temperature is raised to 70°C for the potassium phenolate synthesis reaction. The mixture is then refluxed for dehydration until no water droplets are produced. The refluxed toluene and water are cooled using a primary circulating water system and a primary cold brine system under negative pressure. The condensate is collected in a water separator, and the toluene is recovered after settling. The solution is heated to 120°C for solvent recovery of toluene. Then, 3,4-dichlorotrifluorotoluene is added dropwise, and the temperature is raised to 150°C and held for 10 hours. The temperature is then lowered to 50°C, and the material is separated by potassium chloride pressure filtration using a pressure filter dryer. The filtrate, after solvent removal, yields a mixture of dietherified condensates and their isomers. The dimethyl sulfoxide obtained after solvent removal is used for the synthesis of potassium phenolate and / or subsequent synthesis steps. Dichloroethane was added to the mixture of the condensate and its isomers, and after dissolution, 4% liquid alkali was added for extraction and separation. The aqueous layer was acidified with 30% hydrochloric acid to obtain a small amount of mono-conjugated phenolic impurities. The organic layer was decolorized with activated carbon for 2 hours and then filtered to obtain a purified dichloroethane solution of the dietherified condensate and its isomers.

[0045] In this reaction, the conversion rate of resorcinol (to form potassium phenolate) is 100%; the conversion rate of potassium phenolate (to form a condensate) is 80%; the conversion rate of potassium phenolate (to form a condensate isomer) is 15%; and the conversion rate of the side reaction (to form a single-linked potassium phenolate) is 5%.

[0046] The molar yield of the condensate was 77.8%, and the molar yield of the condensate (isomer) was 14.6%.

[0047] The reaction equations and the batch reaction and production amounts are as follows:

[0048]

[0049]

[0050]

[0051]

[0052]

[0053]

[0054] Example 2 Nitration Process

[0055] The dichloroethane solution of the dietherified condensate and its isomers obtained in Example 1 was introduced into a microreactor with sulfuric acid and nitric acid in a certain proportion for nitration (reaction temperature 40-50℃). After the reaction was complete, the nitrated liquid and acid solution were separated by a liquid-phase centrifuge. The acid solution was used for acid concentration pretreatment. The nitrated liquid was washed with fresh water, and the washing wastewater was discharged to the workshop wastewater collection tank for temporary storage and periodic treatment. Then, 4% liquid alkali was added for alkaline washing, and the alkaline washing wastewater was discharged to the workshop wastewater collection tank for temporary storage and periodic treatment. The solution was then transferred to a falling film evaporator and an internal desolventizing tank for solvent removal. A primary circulating water cooling + primary cold brine cooling system was used, operating at atmospheric pressure. The condensate was recovered to a water separator, and the recovered dichloroethane solvent was separated for reuse. The obtained nitration product was dissolved in a quantitative amount of toluene to obtain a toluene nitration product solution, which was used in the alcoholysis process.

[0056] The conversion rate of the condensate (forming nitrate) was 99%; the conversion rate of the condensate (isomer) (forming nitrate (isomer A)) was 18.4%; and the conversion rate of the side reaction (forming nitrate (isomer B)) was 78.4%.

[0057] The molar yield of nitrate was 99%, and the molar yield of nitrate (isomer A) was 18.4%.

[0058] The reaction equations and the batch reaction and production amounts are as follows:

[0059]

[0060]

[0061]

[0062]

[0063] Example 3: Alcohololysis Process

[0064] After adding a measured amount of ethanol to the potassium hydroxide reactor, start stirring, cool the brine to below 10°C, add potassium hydroxide, and after the addition is complete, keep the temperature below 30°C. After 2 hours, the potassium hydroxide will be completely dissolved. Keep the temperature for later use.

[0065] A precisely measured toluene nitration product solution was added to the alcoholysis reactor, and the temperature was raised to 35°C. A prepared potassium alkoxide solution was added dropwise (completed over approximately 2 hours). After the addition was complete, the mixture was kept at 45°C for 4 hours. Once a sample was deemed acceptable, the mixture was transferred to a cooling reactor and cooled to 15°C. Fresh water was added for water washing and extraction. The organic layer was transferred to a decolorization reactor, where activated carbon was added for decolorization. After decolorization, the mixture was filtered to remove the activated carbon. The resulting toluene solution was continuously transferred to a falling film evaporator for solvent removal via a primary circulating water cooling system and a primary cold brine cooling system, operating under negative pressure. The toluene solvent was condensed and recovered. After solvent removal, the mixture was transferred to a recrystallization reactor for the dissolution and crystallization process. Petroleum ether was added, and centrifugation was performed when the temperature inside the reactor dropped below 5°C. The centrifugal mother liquor was used for solvent recovery of petroleum ether, and the filter cake was dried to obtain the product ethoxyfluorfen, which was then packaged and stored. The aqueous layer obtained from water washing and extraction was continuously acidified with 30% hydrochloric acid, and then distilled and dehydrated to obtain 2-chloro-4-trifluoromethylphenol and 2-chloro-5-trifluoromethylphenol byproducts, which were used in the nitration product synthesis process.

[0066] The conversion rate of nitrate (to ethoxyflufenican) was 99.5%; the conversion rate of nitrate (isomer A) (to ethoxyflufenican) was 99.5%.

[0067] The molar yield of ethoxyflufenican was 83%.

[0068] The reaction equations and the batch reaction and production amounts are as follows:

[0069]

[0070]

[0071]

[0072]

[0073]

[0074]

[0075]

[0076] Example 4: Preparation process of 2,4-dichloronitrobenzene

[0077] m-Dichlorobenzene, sulfuric acid, and nitric acid are quantitatively added to a nitration reactor for continuous nitration. The reaction temperature is maintained below 40°C throughout the process. After the reaction is complete, the mixture undergoes sedimentation separation. The acid layer is extracted, and the organic layer is washed. The acid layer is extracted with dichloroethane, and the filtrate is used for acid concentration pretreatment. The extracted organic layer is desolventized using a primary circulating water cooling system followed by a primary cold brine cooling system at atmospheric pressure. The dichloroethane solvent is recovered by condensation, and the resulting 2,4-dichloronitrobenzene is used in the nitration product synthesis process. The sedimentation-separated organic layer is washed with 10% liquid alkali and fresh water. The washed organic layer is then dehydrated to obtain 2,4-dichloronitrobenzene, which is used in the nitration product synthesis process.

[0078] The conversion rate of m-dichlorobenzene (to produce 2,4-dichloronitrobenzene) was 99%, and the conversion rate of the side reaction (to produce 1,5-dichloro-2,4-dinitrobenzene) was 0.5%.

[0079] The molar yield of 2,4-dichloronitrobenzene was 94.1%.

[0080] The reaction equations and the batch reaction and production amounts are as follows:

[0081]

[0082]

[0083]

[0084] Example 5: Synthesis Process of Nitration Products

[0085] A measured amount of fresh DMSO, DMSO washing liquid (from washing), recovered DMSO (from solvent extraction and distillation), and 2,4-dichloronitrobenzene (from the 2,4-dichloronitrobenzene preparation process) were added to a synthesis reactor. Stirring was initiated, and potassium carbonate was added, followed by 2-chloro-4-trifluoromethylphenol and 2-chloro-5-trifluoromethylphenol byproducts (from the alcoholysis process). The temperature was raised to 100°C and maintained for 10 hours. After sampling and confirming compliance, the temperature was lowered to below 50°C, and the mixture was desalted using a pressure filter and dryer. The filtrate was desolventized to recover DMSO, yielding a nitration product. This nitration product was dissolved in toluene to prepare a toluene-nitration product solution for use in the alcoholysis process. The filter cake was washed with the recovered DMSO solvent to obtain a DMSO washing liquid for denitration in the synthesis reactor.

[0086] The conversion rate of 2,4-dichloronitrobenzene (to form a nitrate) was 88%, the conversion rate of 2,4-dichloronitrobenzene (to form a nitrate (isomer A)) was 9.5%, and the conversion rate of the side reaction (to form a nitrate (isomer B)) was 2%.

[0087] The molar yield of the nitrate was 82.5%, and the molar yield of the nitrate (isomer A) was 9.0%.

[0088] The reaction equations and the batch reaction and production amounts are as follows:

[0089]

[0090]

[0091]

[0092] The embodiments described above are merely preferred embodiments of the present invention, and not an exhaustive list of all possible implementations of the present invention. Any obvious modifications made by those skilled in the art without departing from the principles and spirit of the present invention should be considered to be included within the scope of protection of the claims of the present invention.

Claims

1. A method for producing ethoxyflufenicol, characterized in that, Includes the following steps: (1) Condensation process An organic solvent was added to a condensation vessel, along with resorcinol and potassium hydroxide. The mixture was refluxed to remove water, yielding a potassium resorcinol solution. The solution was then heated, and 3,4-dichlorotrifluorotoluene was added. The mixture was heated and maintained at this temperature to yield the dietherified condensate and its isomers, as shown in the following reaction formula: The organic solvent in step (1) is dimethyl sulfoxide (DMSO), which may optionally include toluene recovered after dehydration, toluene recovered after solvent removal, and DMSO recovered after solvent removal. (2) Nitrification process The dietherified condensate and its isomers prepared in step (1) are introduced into a microreactor with sulfuric acid and nitric acid in a certain proportion to obtain the nitration product and its isomers. The reaction formula is as follows: ； (3) Alcohololysis process The nitration product and its isomers prepared in step (2) were subjected to alcoholysis in the presence of ethanol and KOH to obtain the main product ethoxyflufenoxam and the byproducts 2-chloro-4-trifluoromethylphenol potassium and 2-chloro-5-trifluoromethylphenol potassium, as shown in the following reaction formula: ； (4) Preparation process of 2,4-dichloronitrobenzene The reaction formula is as follows: ； The specific operation is as follows: add m-dichlorobenzene, sulfuric acid and nitric acid to the nitration reactor in a quantitative manner to carry out the nitration reaction. The reaction temperature is kept below 40°C throughout the process. After the reaction is complete, the mixture enters the sedimentation separation stage. The acid layer is extracted and the organic layer is washed. Dichloroethane is added to the acid layer for extraction. The organic layer obtained by extraction is desolventized. The process is carried out by cooling with first-stage circulating water and first-stage cold brine at atmospheric pressure. The dichloroethane solvent is condensed and recovered. After removing the solvent, 2,4-dichloronitrobenzene is obtained and used in the nitration product synthesis process of step (5). The organic layer obtained by sedimentation separation is washed with 10% liquid alkali and fresh water. The washed organic layer is dehydrated and 2,4-dichloronitrobenzene is obtained and used in the nitration product synthesis process of step (5). (5) Nitration product synthesis process The reaction formula is as follows: ； The specific operation is as follows: Fresh dimethyl sulfoxide and / or dimethyl sulfoxide and 2,4-dichloronitrobenzene obtained by desolventizing in step (1) are put into the synthesis kettle, stirred, potassium carbonate is added, and then 2-chloro-4-trifluoromethylphenol and 2-chloro-5-trifluoromethylphenol byproducts obtained in step (3) are added. The temperature is raised to 100°C and kept at the temperature for 10 hours. After the sample is qualified, the temperature is lowered to below 50°C and desalted in a pressure filter drying machine. The filtrate is desolventized and DMSO is recovered to obtain nitration products. The nitration products are added to toluene to dissolve and to prepare a toluene nitration product solution for the alcoholysis process in step (3). Alternatively, the byproducts potassium 2-chloro-4-trifluoromethylphenol and potassium 2-chloro-5-trifluoromethylphenol from step (3) can be acidified to convert them into 2-chloro-4-trifluoromethylphenol and 2-chloro-5-trifluoromethylphenol, and then reacted with the 2,4-dichloronitrobenzene prepared in step (4) in the presence of potassium carbonate to prepare the nitrated product, as shown in the following reaction formula: ; ； (6) Repeat the alcoholysis process of step (3) with the nitration product and nitration product isomer prepared in step (5) to prepare ethoxyflufenicol, and recover the by-products potassium 2-chloro-4-trifluoromethylphenol and potassium 2-chloro-5-trifluoromethylphenol for use in step (5).

2. The method for producing ethoxyflufenicol according to claim 1, characterized in that, In step (1), the specific operation of reflux dehydration is as follows: turn on the vacuum, heat to reflux, dehydrate until no water droplets are generated, and the solvent dehydrated by reflux is cooled by primary circulating water and primary cold brine, and then recovered to the water separator. After water separation, the toluene is reused in the next batch of step (1).

3. The method for producing ethoxyflufenicol according to claim 1, characterized in that, In step (1), the specific operation for preparing the dietherified condensate and its isomers is as follows: the feed solution is heated to 120°C, the toluene recovered by desolventizing is used for the synthesis of potassium phenolate, then 3,4-dichlorotrifluorotoluene is added dropwise, the temperature is raised to 150°C and kept at 10h, the temperature is lowered to 50°C, and the material is separated by potassium chloride pressure filtration using a pressure filter drying machine. The dietherified condensate and its isomer mixture obtained after desolventizing the filtrate is used for the synthesis of potassium phenolate and / or subsequent synthesis steps. Dichloroethane is added to the condensate and its isomer mixture, and after dissolution, 4% liquid alkali is added for extraction and separation. The aqueous layer is acidified with 30% hydrochloric acid, the organic layer is decolorized with activated carbon, and the purified dietherified condensate and its isomer dichloroethane solution is obtained by pressure filtration.

4. The method for producing ethoxyflufenicol according to claim 1, characterized in that, In step (2), the reaction temperature of the nitration reaction is 40-50℃. After the reaction is complete, the nitration liquid and acid liquid are separated by a liquid centrifuge. The acid liquid is used for acid concentration pretreatment. The nitration liquid is then washed with water and alkali to obtain the nitration product. The obtained nitration product is dissolved in a certain amount of toluene to obtain a toluene nitration product solution, which is used for the alcoholysis process in step (3).

5. The method for producing ethoxyflufenicol according to claim 1, characterized in that, Step (3) is as follows: After adding a measured amount of ethanol to the potassium alkoxide reactor, start stirring, cool the brine to below 10°C, add potassium hydroxide, and after the addition is complete, keep the temperature below 30°C. After 2 hours, the potassium hydroxide will be completely dissolved and kept warm for later use. Then, add an accurately measured toluene nitration product solution to the alcoholysis reactor, heat to 35°C, and add the prepared potassium alkoxide solution dropwise. The addition will be completed in 2 hours. After the addition is completed, keep the temperature at 45°C for 4 hours. After the sample is qualified, transfer it to a cooling reactor, cool it to 15°C, wash and extract with water, and transfer the organic layer to a decolorization reactor. Activated carbon was added for decolorization. After decolorization, the product was continuously transferred to a falling film evaporator and an internal desolventizing vessel to remove and recover the solvent toluene. After desolventizing, the product was transferred to the dissolution and crystallization process. Petroleum ether was added. When the temperature dropped below 5°C, the product was centrifuged. The mother liquor was desolventized and the petroleum ether was recovered. The filter cake was dried to obtain the product ethoxyfluorfen, which was packaged and stored. The water layer of the water-washed extract was continuously acidified with 30% hydrochloric acid. After distillation and dehydration, 2-chloro-4-trifluoromethylphenol and 2-chloro-5-trifluoromethylphenol byproducts were obtained and used in the nitration product synthesis process of step (5).

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