Method for continuously preparing 4-fluoro-2-trifluoromethyl acetophenone

Abstract

The invention discloses a method for continuously preparing 4-fluoro-2-trifluoromethyl acetophenone, which comprises the following steps of: pre-filling a magnesium metal bed layer in a Grignard reactor, respectively feeding a 2-bromine-5-fluorobenzotrifluoride solution and magnesium metal from the bottom and the top of the Grignard reactor, introducing inert gas from the bottom of the Grignard reactor, and continuously reacting at the temperature of between 20 and 30 DEG C to obtain 4-fluoro-2-trifluoromethyl acetophenone. After being distributed by the microporous disperser, the gas uniformly enters the Grignard reactor from bottom to top, and the gas discharged from a gas outlet in the top of the Grignard reactor is re-introduced into the bottom of the Grignard reactor; reaction liquid obtained after the Grignard reaction is completed flows out and then is divided into two parts, a small part of the first part returns to the bottom of the Grignard reactor to serve as an initiator of the Grignard reaction, and a large part of the second part is sequentially subjected to acylation reaction and acidolysis reaction and then is subjected to post-treatment, so that the target product 4-fluoro-2-trifluoromethyl acetophenone is obtained. The method has the advantages of high reaction efficiency, simple system, low cost and the like, and industrial production is easy to realize.

Description

Technical Field

[0001] This invention relates to the field of organic synthesis technology, and specifically to a method for the continuous preparation of 4-fluoro-2-trifluoromethylacetophenone. Background Technology

[0002] 4-Fluoro-2-trifluoromethylacetophenone is a key intermediate in the synthesis of chlorfluazuril. Chlorfluazuril is a novel triazole fungicide developed by BASF in 2012. It has advantages such as broad fungicidal spectrum, excellent systemic conductivity, long residual effect, high safety, low environmental pollution, low likelihood of causing pesticide residue exceeding standards, flexible application methods, and good compatibility, making its market prospects very promising.

[0003] The synthesis processes for 4-fluoro-2-trifluoromethylacetophenone include:

[0004] ① The reagents were prepared using 2-bromo-4-fluorotrifluorotoluene, methylboric acid, and carbon monoxide as raw materials under the action of palladium catalyst and phosphine ligand (CN119409561A). This route has high reagent costs and is not competitive.

[0005] ②The raw material (WO2020 / 132792Al) is prepared by degreasing reaction using 2-benzoyl malonate compounds as raw materials. However, the preparation of raw materials for this route is complicated and its competitiveness is limited.

[0006] ③ Using 2-bromo-5-fluorotrifluorotoluene as a raw material, a Grignard reagent is first prepared, followed by an acylation reaction to obtain the final product (US2014155262A1, CN105829274A, etc.). This route is currently the main method used in industrial production. The preparation of the Grignard reagent involves the direct reaction of 2-bromo-5-fluorotrifluorotoluene with metallic magnesium, or a Grignard exchange reaction with reagents such as isopropyl magnesium bromide. The reagents used in the acylation reaction mainly include acetyl chloride and acetic anhydride, which can carry out the acylation reaction without a catalyst. However, to improve selectivity and efficiency, Cu(I) salt, Cu(II) salt, or Li salt catalysts are usually added. In this preparation process, both steps are strongly exothermic, posing high safety risks. Existing reports all involve batch reactor reactions with low heat exchange efficiency, easily generating local hot spots, leading to an increase in coupling byproducts. Furthermore, both metallic magnesium and ketone salt catalysts are poorly soluble in the reaction solvent, limiting the development and implementation of continuous processes. Summary of the Invention

[0007] In view of the above-mentioned technical problems existing in the prior art, the purpose of this application is to provide a method for continuous preparation of 4-fluoro-2-trifluoromethylacetophenone, so as to achieve continuous preparation, reduce coupling impurities, improve yield and efficiency, and improve intrinsic safety level.

[0008] The technical solution adopted in this invention is as follows:

[0009] The method for continuous preparation of 4-fluoro-2-trifluoromethylacetophenone includes the following steps:

[0010] (1) The Grignard reactor is a vertical reaction tube structure with a condenser jacket on the outside and a microporous disperser at the bottom. The Grignard reactor is pre-filled with a bed of magnesium granules. The raw material 2-bromo-5-fluorotrifluorotoluene solution is continuously introduced into the bottom of the Grignard reactor by a metering pump. At the same time, the magnesium granules are continuously added through the top feed port of the Grignard reactor by a solid feeder. The temperature is controlled by circulating refrigerant in the condenser jacket on the outside of the Grignard reactor. Meanwhile, inert gas is introduced from the bottom of the Grignard reactor. After being distributed by the microporous disperser, it enters the Grignard reactor uniformly from bottom to top and is then discharged from the gas outlet at the top of the Grignard reactor. A condenser is installed on the gas outlet to condense the entrained solvent and return it to the reactor. The remaining non-condensable inert gas is pumped back into the bottom of the Grignard reactor by a circulating pump.

[0011] (2) The reaction liquid after the Grignard reaction is completed flows out from the upper side outlet of the Grignard reactor and is divided into two parts. The first part is returned to the bottom of the Grignard reactor as the initiator of the Grignard reaction. The second part is mostly Grignard reaction liquid and acylation agent are metered and pumped to the acylation tubular reactor. The acylation tubular reactor contains elemental copper catalyst and is externally temperature controlled by circulating coolant. The acylation reaction is carried out under certain conditions to obtain the acylated reaction liquid. The acylated reaction liquid and dilute hydrochloric acid are continuously pumped into the acid hydrolysis tubular reactor for acid hydrolysis reaction. The reaction liquid flows out of the reactor and is post-processed to obtain the target product 4-fluoro-2-trifluoromethylacetophenone.

[0012] Further, in step 1, the concentration of the 2-bromo-5-fluorotrifluorotoluene solution is 10wt% to 60wt%, and the solvent includes at least one of tetrahydrofuran, 2-methyltetrahydrofuran, dioxane, cyclopentyl methyl ether, toluene, and xylene; the inert gas includes at least one of nitrogen and argon; and the acylating agent includes at least one of acetyl chloride and acetic anhydride.

[0013] Further, in step (1), the feed molar flow ratio of the raw material 2-bromo-5-fluorotrifluorotoluene to metallic magnesium is 1:1 to 1.1, and the volume flow rate of the inert gas is 1 to 10 times the volume flow rate of the raw material solution.

[0014] Further, in step (1), the volume of the pre-filled magnesium bed in the Grignard reactor is 50% to 80% of the liquid holding volume of the reactor; the pore size of the microporous disperser is 1 to 50 μm.

[0015] Furthermore, in step (1), the particle size of the magnesium metal particles is 2-5 mm.

[0016] Furthermore, the Grignard reaction temperature is -10℃ to 30℃, and the residence time is 1 to 30 minutes; after the Grignard reaction is completed and the reaction liquid flows out of the Grignard reactor, the volume percentage of the first small portion of the feed liquid returned to the Grignard reactor is 1% to 5%.

[0017] Further, the acylating agent includes at least one of acetyl chloride and acetic anhydride, and the molar flow ratio of the acylating agent to the magnesium metal particles in step (1) is 1 to 1.5:1; the amount of dilute hydrochloric acid fed into the acidolysis reaction is adjusted based on the pH of the acidolysis reaction material being 4 to 7.

[0018] Furthermore, the copper element in the acylation tubular reactor includes copper wire mesh or copper balls, which are naturally filled, or the acylation tubular reactor containing elemental copper catalyst is a copper static mixer containing elemental copper catalyst; the acylation reaction temperature is -15℃ to 40℃, and the residence time is 0.3 to 10 min; the acidolysis reaction temperature is 0 to 40℃, and the residence time is 0.1 to 1 min.

[0019] Furthermore, the post-processing method involves separating the reaction solution into layers, collecting the organic phase, washing with water, and distilling to recover the solvent to obtain the product.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] (1) This invention utilizes a continuous flow reactor to achieve continuous synthesis of key steps such as Grignard reagent preparation, acylation reaction, and acidolysis reaction.

[0022] (2) The preparation of Grignard reagents involves introducing inert gas dispersed in micropores to make mass and heat transfer in the reactor more uniform and efficient, and to reduce side reactions in the preparation of Grignard reagents.

[0023] (3) Elemental copper catalyzes acylation reactions, resulting in lower catalyst costs; at the same time, the structured copper catalysis can also enhance mass and heat transfer and reduce side reactions in the acylation step.

[0024] (4) The process method of the present invention further controls the parameters such as feed temperature, reaction temperature and pressure of raw materials in steps, further improving the reaction yield and product purity, which is conducive to realizing industrial production. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the continuous preparation process of 4-fluoro-2-trifluoromethylacetophenone according to the present invention. Detailed Implementation

[0026] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0027] A schematic diagram of the continuous preparation process of 4-fluoro-2-trifluoromethylacetophenone according to this invention is shown below. Figure 1 .

[0028] Example 1:

[0029] A method for the continuous preparation of 4-fluoro-2-trifluoromethylacetophenone includes the following steps:

[0030] 1) The pre-filled bed of magnesium granules (particle size 2-5 mm, the same below) in the Grignard reactor has a loading volume of 60% of the reactor's liquid holding volume.

[0031] First, a 10 wt% tetrahydrofuran solution of 2-bromo-5-fluorotrifluorotoluene is prepared. Then, this solution is continuously introduced into the Grignard reactor through the bottom using a metering pump. Magnesium granules are continuously added to the Grignard reactor through the top feed port of the reactor via a solid feeder. At the same time, an inert gas, nitrogen, is introduced from the bottom of the Grignard reactor. The volumetric flow rate of nitrogen is 10 times that of the 2-bromo-5-fluorotrifluorotoluene tetrahydrofuran solution. After being distributed by a microporous disperser at the bottom of the reactor, the gas enters the reactor uniformly from bottom to top. The pore size of the microporous disperser is 10 μm. Then, the gas is discharged from the gas outlet at the top of the reactor. A condenser is installed at the top gas outlet of the Grignard reactor to condense the entrained solvent and return it to the reactor. The remaining gas is pumped back into the reactor by a circulation pump.

[0032] The feed molar ratio of 2-bromo-5-fluorotrifluorotoluene to metallic magnesium is 1:1. The Grignard reactor is cooled to -10°C by circulating refrigerant in a jacket, and the residence time of the Grignard reaction is 30 min.

[0033] 2) The Grignard reaction solution, after completion, flows out from the upper side outlet of the Grignard reactor and is divided into two parts. One portion of the reaction solution is fed into the bottom of the Grignard reactor through the lower side return outlet, while the remaining 99% flows to the acylation tubular reactor, where it is mixed with acetyl chloride for acylation. The acylation tubular reactor is filled with copper wire mesh, which is naturally clogged. The molar flow ratio of the Grignard reagent (magnesium metal) in step 1) to the acetyl chloride in step 2) is 1:1.4. The residence time for the acylation reaction is 9 minutes, and the reaction temperature is -10°C.

[0034] 3) The acylation reaction solution then flows directly into a tubular acidolysis reactor equipped with a static mixer, where it is mixed with 1% (w / w) dilute hydrochloric acid for acidolysis. The acidolysis reaction residence time is 0.1 min, the temperature is 0℃, and the pH of the post-acidolysis solution is controlled to be 7. After the reaction solution flows out of the acidolysis reactor, it undergoes stratification, the organic layer is collected, washed with water, and then the solvent is removed by distillation to obtain the target product, 4-fluoro-2-trifluoromethylacetophenone, with a yield of 99% and a purity of 99.5%.

[0035] Example 2:

[0036] First, a 30 wt% cyclopentyl methyl ether solution of 2-bromo-5-fluorotrifluorotoluene is prepared. Then, this solution is continuously fed into a Grignard reactor pre-loaded with 50% volume of magnesium granules (i.e., the volume of the magnesium granule bed is 10% of the liquid holding volume of the reactor) through the bottom feed inlet of the reactor using a metering pump. The magnesium granules are continuously added to the Grignard reactor through the top feed inlet of the reactor using a solid feeder. At the same time, nitrogen gas is introduced from the bottom gas inlet of the reactor. The nitrogen flow rate is twice the flow rate of the 2-bromo-5-fluorotrifluorotoluene solution. After being distributed by a microporous disperser at the bottom of the reactor, the gas enters the reactor uniformly from bottom to top. The pore size of the microporous disperser is 2 μm. Then, the gas is discharged from the top gas outlet of the reactor. A condenser is installed above the gas outlet to condense the entrained solvent and return it to the reactor. The remaining gas is pumped back into the reactor by a circulation pump. The feed molar ratio of 2-bromo-5-fluorotrifluorotoluene to magnesium was 1:1.05. The reactor temperature was controlled at 10°C via a jacketed circulating coolant. The Grignard reaction residence time was 10 min. The completed Grignard reaction liquid flowed out from the outlet on the upper side of the Grignard reactor. 3% of the reaction liquid was returned to the Grignard reactor via the inlet on the lower side of the reactor, while the remaining 97% flowed to an acylation tubular reactor to be mixed with acetyl chloride for acylation. The acylation tubular reactor was filled with copper balls in a naturally packed state. The molar ratio of Grignard reagent to acetyl chloride was 1:1. The acylation reaction residence time was 5 min, and the reaction temperature was 10°C. The acylation reaction liquid then flowed directly into a tubular acidolysis reactor equipped with a static mixer, where it was mixed with 10% dilute hydrochloric acid for acidolysis. The acidolysis reaction residence time was 0.5 min, the temperature was 20°C, and the pH of the post-acidolysis solution was controlled to be 6. After the reaction liquid flows out of the acidolysis reactor, it is separated into layers. The organic layer is collected, washed with water, and then the solvent is removed by distillation to obtain the target product 4-fluoro-2-trifluoromethylacetophenone, with a yield of 97% and a product purity of 99.6%.

[0037] Example 3:

[0038] First, a 60 wt% toluene solution of 2-bromo-5-fluorotrifluorotoluene is prepared. Then, this solution is continuously fed into a Grignard reactor pre-filled with 80% volume of magnesium granules through the bottom inlet of the reactor using a metering pump. The magnesium granules are continuously added to the Grignard reactor through the top inlet of the reactor using a solid feeder. At the same time, argon gas is introduced from the bottom gas inlet of the reactor. The volumetric flow rate of the argon gas is 1 times the volumetric flow rate of the 2-bromo-5-fluorotrifluorotoluene solution. After being distributed by a microporous disperser at the bottom of the reactor, the gas enters the reactor uniformly from bottom to top. The pore size of the microporous disperser is 50 μm. Then, the gas is discharged from the top gas outlet of the reactor. A condenser is installed above the gas outlet to condense the entrained solvent and return it to the reactor. The remaining gas is pumped back into the reactor by a circulation pump. The feed molar ratio of 2-bromo-5-fluorotrifluorotoluene to metallic magnesium is 1:1.1. The reactor temperature is controlled at 30°C via a jacketed circulating coolant. The Grignard reaction residence time is 0.3 min. The completed Grignard reaction liquid flows out from the outlet on the upper side of the Grignard reactor. 5% of the reaction liquid is returned to the Grignard reactor via the inlet on the lower side of the reactor, while the remaining 95% flows to an acylation tubular reactor, where it is mixed with acetic anhydride for acylation. The acylation tubular reactor is a static mixer containing a copper catalyst. The molar ratio of Grignard reagent to acetic anhydride is 1:1.1. The acylation reaction residence time is 5 min, and the reaction temperature is 40°C. The acylation reaction liquid then flows directly into a tubular acidolysis reactor equipped with a static mixer, where it is mixed with 10% dilute hydrochloric acid for acidolysis. The acidolysis reaction residence time is 0.5 min, the temperature is 20°C, and the pH of the post-acidolysis solution is controlled to be 6. After the reaction solution flows out of the acidolysis reactor, it is separated into layers. The organic layer is collected, washed with water, and then the solvent is removed by distillation to obtain the target product 4-fluoro-2-trifluoromethylacetophenone, with a yield of 95% and a product purity of 99.2%.

[0039] Example 4:

[0040] First, a 20 wt% xylene solution of 2-bromo-5-fluorotrifluorotoluene is prepared. Then, this solution is continuously fed into a Grignard reactor pre-filled with 70% volume of magnesium granules through the bottom inlet of the reactor using a metering pump. The magnesium granules are continuously added to the Grignard reactor through the top inlet of the reactor using a solid feeder. At the same time, argon gas is introduced from the bottom gas inlet of the reactor. The volumetric flow rate of the argon gas is 7 times the volumetric flow rate of the 2-bromo-5-fluorotrifluorotoluene solution. After being distributed by a microporous disperser at the bottom of the reactor, the gas enters the reactor uniformly from bottom to top. The pore size of the microporous disperser is 10 μm. Then, the gas is discharged from the top gas outlet of the reactor. A condenser is installed above the gas outlet to condense the entrained solvent and return it to the reactor. The remaining gas is pumped back into the reactor by a circulation pump. The feed molar ratio of 2-bromo-5-fluorotrifluorotoluene to metallic magnesium is 1:1. The reactor temperature is controlled at 0°C through a jacketed circulating coolant. The residence time for the Grignard reaction is 3 min. The completed Grignard reaction liquid flows out from the outlet on the upper side of the Grignard reactor. 3% of the reaction liquid is returned to the Grignard reactor through the inlet on the lower side of the reactor, while the remaining 97% flows to an acylation tubular reactor, where it is mixed with acetic anhydride for acylation. The acylation tubular reactor is a static mixer containing a copper catalyst. The molar ratio of Grignard reagent to acetic anhydride is 1:1.1, the residence time is 10 min, and the reaction temperature is 20°C. The acylation reaction liquid then flows directly into a tubular acidolysis reactor equipped with a static mixer, where it is mixed with 10% dilute hydrochloric acid for acidolysis. The residence time for the acidolysis reaction is 0.5 min, the temperature is 20°C, and the pH of the post-acidolysis solution is controlled to be 7. After the reaction solution flows out of the acidolysis reactor, it is separated into layers. The organic layer is collected, washed with water, and then the solvent is removed by distillation to obtain the target product 4-fluoro-2-trifluoromethylacetophenone, with a yield of 99% and a product purity of 99.7%.

[0041] Compare with Example 1:

[0042] The experimental procedure of Example 2 was repeated in accordance with Example 1, except that "the pre-filled magnesium bed in the Grignard reactor was 10% of the liquid holding volume of the reactor". All other conditions remained the same, and the target product 4-fluoro-2-trifluoromethylacetophenone was finally obtained with a yield of 67% and a product purity of 74%.

[0043] Compare with Example 2:

[0044] The experimental procedure of Example 2 was repeated, except that nitrogen was not introduced into the bottom of the Grignard reactor. All other conditions remained the same, and the target product 4-fluoro-2-trifluoromethylacetophenone was finally obtained with a yield of 93.3% and a purity of 95.8%.

[0045] Compared with Example 2, under the condition of no nitrogen gas, the reaction effect decreased to a certain extent. On the other hand, as the reaction time was extended, the pressure drop of the reaction liquid increased significantly, which was not conducive to the stable operation of the reaction process.

[0046] Compare with Example 3:

[0047] The experimental process of Example 3 was repeated in Example 2, except that "the Grignard reaction liquid flowing out of the outlet on the upper side of the Grignard reactor was not refluxed, but all of it entered the acylation tubular reactor and was mixed with acetyl chloride for acylation reaction". All other conditions remained the same, and the target product 4-fluoro-2-trifluoromethylacetophenone was finally obtained with a yield of 82.9% and a product purity of 85.4%.

[0048] Compare with Example 4:

[0049] The experimental procedure of Example 4 was repeated in Example 2, except that "20% of the Grignard reaction liquid flowing out from the outlet on the upper side of the Grignard reactor was returned to the Grignard reactor for further reaction, while the other 80% flowed to the acylation tubular reactor and mixed with acetyl chloride for acylation reaction". All other conditions remained unchanged, and the target product 4-fluoro-2-trifluoromethylacetophenone was finally obtained with a yield of 98% and a purity of 99.8%.

[0050] In Comparative Example 4, the Grignard reaction had a high liquid reflux rate, which, although resulting in higher reaction yield and purity, was not conducive to improving the equipment efficiency of the Grignard reactor.

[0051] The contents described in this specification are merely an enumeration of the implementation forms of the inventive concept, and the scope of protection of this invention should not be regarded as limited to the specific forms described in the embodiments.

Claims

1. A method for the continuous preparation of 4-fluoro-2-trifluoromethylacetophenone, characterized in that, Includes the following steps: (1) The Grignard reactor is a vertical reaction tube structure. A condensing jacket is installed on the outside of the side and a microporous disperser is installed at the bottom. The Grignard reactor is pre-filled with a bed of magnesium granules. The raw material 2-bromo-5-fluorotrifluorotoluene solution is continuously introduced through the bottom of the Grignard reactor by a metering pump. At the same time, the magnesium granules are continuously introduced from the top of the Grignard reactor. The temperature is controlled by circulating refrigerant in the condensing jacket outside the Grignard reactor. At the same time, inert gas is introduced from the bottom of the Grignard reactor. After being distributed by the microporous disperser, it enters the Grignard reactor uniformly from bottom to top. The gas discharged from the gas outlet at the top of the Grignard reactor is returned to the bottom of the Grignard reactor to form a circulation loop of inert gas. (2) The reaction liquid after the Grignard reaction is completed flows out from the upper side outlet of the Grignard reactor and is divided into two parts. The first part is returned to the bottom of the Grignard reactor as the initiator of the Grignard reaction. The second part is mostly subjected to acylation reaction and acid hydrolysis reaction in sequence, and then post-processed to obtain the target product 4-fluoro-2-trifluoromethylacetophenone.

2. The method for continuous preparation of 4-fluoro-2-trifluoromethylacetophenone as described in claim 1, characterized in that, A condenser is installed at the top outlet of the Grignard reactor. Gas discharged from the top outlet of the Grignard reactor enters the condenser, condensing the solvent entrained in the gas and flowing it back down. The remaining non-condensable inert gas is pumped back into the bottom of the Grignard reactor by a circulation pump. A solid feeder is connected to the top inlet of the Grignard reactor, through which metallic magnesium is added into the Grignard reactor. The lower side of the Grignard reactor is also provided with a reaction liquid reflux port. The reaction liquid of the first small part of the Grignard reaction is introduced into the bottom of the Grignard reactor through the reaction liquid reflux port. The reaction liquid reflux port is located above the microporous disperser.

3. The method for continuous preparation of 4-fluoro-2-trifluoromethylacetophenone as described in claim 1, characterized in that, The mass concentration of the raw material 2-bromo-5-fluorotrifluorotoluene solution is 10wt%~60wt%, and the solvent of the solution is at least one of tetrahydrofuran, 2-methyltetrahydrofuran, dioxane, cyclopentyl methyl ether, toluene, and xylene; the inert gas includes at least one of nitrogen and argon.

4. The method for continuous preparation of 4-fluoro-2-trifluoromethylacetophenone as described in claim 1, characterized in that, In step (1), the feed molar flow ratio of the raw material 2-bromo-5-fluorotrifluorotoluene to metallic magnesium is 1:1 to 1.1, and the volumetric flow rate of the inert gas is 1 to 10 times the volumetric flow rate of the raw material solution.

5. The method for continuous preparation of 4-fluoro-2-trifluoromethylacetophenone as described in claim 1, characterized in that, In step (1), the volume of the pre-filled magnesium bed in the Grignard reactor is 50% to 80% of the liquid holding volume of the reactor; the pore size of the microporous disperser is 1 to 50 μm; and the particle size of the magnesium particles is 2 to 5 mm.

6. The method for continuous preparation of 4-fluoro-2-trifluoromethylacetophenone as described in claim 1, characterized in that, The Grignard reaction temperature is -10℃ to 30℃, and the residence time is 1 to 30 minutes. After the Grignard reaction is completed, the volume percentage of the reaction liquid that flows out of the Grignard reactor is 1% to 5%.

7. The method for continuous preparation of 4-fluoro-2-trifluoromethylacetophenone as described in claim 1, characterized in that, Step (2) involves sequential acylation and acidolysis reactions as follows: The reaction solution and acylation agent completed by the Grignard reaction are metered and pumped to the acylation tubular reactor. The acylation tubular reactor contains a copper catalyst and is externally temperature-controlled by a circulating coolant. The acylation reaction is carried out under certain conditions to obtain the acylated reaction solution. The acylated reaction solution and dilute hydrochloric acid are continuously pumped into the acidolysis tubular reactor for acidolysis reaction. Finally, the target product 4-fluoro-2-trifluoromethylacetophenone is obtained after post-treatment.

8. The method for continuous preparation of 4-fluoro-2-trifluoromethylacetophenone as described in claim 7, characterized in that, The acylating agent includes at least one of acetyl chloride and acetic anhydride, and the molar flow ratio of the acylating agent to the magnesium granules in step (1) is 1~1.5:1; the amount of dilute hydrochloric acid fed into the acidolysis reaction is adjusted based on the pH of the acidolysis reaction material as 4~7.

9. The method for continuous preparation of 4-fluoro-2-trifluoromethylacetophenone as described in claim 7, characterized in that, The acylation tubular reactor contains copper elements, including copper wire mesh or copper balls, in a naturally filled state, or the acylation tubular reactor containing elemental copper catalyst is a copper static mixer containing elemental copper catalyst; the acylation reaction temperature is -15℃ to 40℃, and the residence time is 0.3 to 10 min; the acidolysis reaction temperature is 0 to 40℃, and the residence time is 0.1 to 1 min.

10. The method for continuous preparation of 4-fluoro-2-trifluoromethylacetophenone according to claim 1, characterized in that, The post-processing method involves separating the reaction solution into layers, collecting the organic phase, washing with water, and distilling to recover the solvent to obtain the product.

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