Preparation process of 3, 4, 5-trifluoroaniline

Abstract

The invention discloses a preparation process of 3, 4, 5-trifluoroaniline, which comprises the following steps: by taking 1, 2, 3-trifluorobenzene as a raw material, firstly carrying out nitration reaction by using concentrated hydrochloric acid and concentrated nitric acid, then carrying out hydrogenation reaction under the action of a palladium carbon catalyst, and then separating to obtain the 3, 4, 5-trifluoroaniline with higher purity. The process has the advantages of easily available raw materials, simple production process, high product purity and low comprehensive cost, and is suitable for industrial production.

Description

Technical Field

[0001] The invention belongs to the technical field of fine chemical production, and specifically relates to a preparation process of 3,4,5-trifluoroaniline. Background Art

[0002] 3,4,5-Trifluoroaniline can be used to make dyes, drugs, resins, and can also be used as a rubber vulcanization accelerator, etc. It can also be used as a pharmaceutical and organic synthesis intermediate. 3,4,5-Trifluoroaniline is used as a pharmaceutical intermediate in the pharmaceutical field to synthesize a variety of drugs. It is also a key raw material for the preparation of the benzidine intermediate of the new SDHI fungicide flupyraclostrobin.

[0003] Fluopyrab is an amide fungicide developed by BASF and is also a succinate dehydrogenase inhibitor. Fluopyrab is highly efficient, broad-spectrum, long-lasting, highly selective, has excellent systemic conductivity, and has both preventive and therapeutic effects. It can inhibit spore germination, spore tube elongation, mycelium growth and spore formation, and can effectively prevent and control major diseases of cereals, soybeans, corn, rapeseed, fruit trees, vegetables, beets, peanuts, cotton, lawns and specialty crops. SDHI fungicides are the third largest fungicide category in the world, and its market grew rapidly from 2011 to 2017. Fluopyrab has topped the list since 2015, accounting for 22% to 25% of the entire SDHI fungicide market, with global sales reaching US$490 million in 2019.

[0004] The current synthesis methods of 3,4,5-trifluoroaniline are mainly:

[0005] The patent with PCT application number WO2004037765 discloses a method for preparing 3,4,5-trifluoronitrobenzene, using 2,3,4-trifluoroaniline as a raw material, and preparing the 3,4,5-trifluoroaniline product through acetylation, nitration, diazotization deamination, and reduction.

[0006] The Chinese patent publication number CN107311869 discloses a method for preparing 3,4,5-trifluoronitrobenzene, wherein 3,5-dichloro-4-fluoronitrobenzene is fluorinated with potassium fluoride to obtain 3,4,5-trifluoronitrobenzene, which is then reduced to obtain the 3,4,5-trifluoroaniline product.

[0007] The above two methods for preparing 3,4,5-trifluoroaniline both have problems such as difficult to obtain raw materials and high costs. In addition, the first method has a long process route, low yield, and a large amount of three wastes, which is not suitable for industrial production.

[0008] The document "Research on the Synthesis Process of 2,3,4-Trifluoroaniline" by the master's thesis of Central South University provides a method for preparing 2,3,4-trichloronitrobenzene, which is a nitration reaction of 1,2,3-trichlorobenzene with sulfuric acid and fuming nitric acid. The product is 2,3,4-trichloronitrobenzene, and 3,4,5-trichloronitrobenzene is not obtained. It can be seen that it is difficult to obtain 3,4,5-trichloronitrobenzene product by similar nitration reaction.

[0009] In summary, the current preparation of 3,4,5-trifluoroaniline is difficult and the cost is high. Summary of the invention

[0010] The invention aims to provide a preparation process of 3,4,5-trifluoroaniline, which has easy-to-obtain reaction raw materials, a short synthesis route, high product purity and low comprehensive cost, and has great guiding significance for industrial production.

[0011] To achieve the above purpose, the technical solution of the present invention is as follows:

[0012] A preparation process of 3,4,5-trifluoroaniline comprises the following steps:

[0013] 1) dissolving 1,2,3-trifluorobenzene in concentrated sulfuric acid to obtain a mixed solution, then controlling the temperature at 80-100° C., dropping concentrated nitric acid into the mixed solution, and keeping the temperature for reaction after the dropping is completed. During the reaction, the remaining amount of 1,2,3-trifluorobenzene raw material in the reaction solution is monitored by control system. When the remaining amount of 1,2,3-trifluorobenzene is less than 1wt%, the reaction is completed. Then, water is dropped into the reaction solution, and the temperature of the reaction solution is controlled at 0-20° C. After the dropping is completed, the reaction solution is allowed to stand and separated to obtain an organic phase 1, which is then washed with water, allowed to stand, and separated to obtain an organic phase 2 for standby use;

[0014] 2) putting the solvent, organic phase 2 and palladium-carbon catalyst into an autoclave, sealing, stirring, and replacing with nitrogen, passing hydrogen into the autoclave to control the pressure at 0.2-2MPa and the temperature at 10-40°C to carry out a hydrogenation reaction, and after the reaction is completed, releasing the pressure, replacing with nitrogen, extracting and filtering the material, recycling the obtained solid, distilling the obtained filtrate to remove the solvent, and subjecting the remaining material to negative pressure distillation to obtain 3,4,5-trifluoroaniline; the palladium content in the palladium-carbon catalyst is 0.05-0.5wt%.

[0015] Preferably, in step 1), the amount of concentrated sulfuric acid used is 5 to 10 times the weight of the 1,2,3-trifluorobenzene raw material.

[0016] Preferably, in step 1), the concentrated nitric acid content is 68% to 98%, and the amount used is 1.1 to 1.5 eq of 1,2,3-trifluorobenzene.

[0017] Preferably, in step 1), after the reaction is completed, the amount of water added dropwise to the reaction solution is 30-40% of the total weight of concentrated sulfuric acid.

[0018] Preferably, in step 2), the solvent is one or more of methanol, ethanol, isopropanol, and toluene, and the amount of the solvent used is 3 to 10 times the weight of the 1,2,3-trifluorobenzene raw material.

[0019] Preferably, in step 2), 2,3,4-trifluoroaniline is obtained in a negative pressure distillation process.

[0020] Preferably, in step 2), the remaining amount of 3,4,5-trifluoronitrobenzene in the reaction solution is monitored during the hydrogenation reaction, and the reaction is terminated when the remaining amount of 3,4,5-trifluoronitrobenzene is less than 0.5 wt%.

[0021] The present invention uses 1,2,3-trifluorobenzene as a raw material, and effectively prepares 3,4,5-trifluoroaniline product through nitration and hydrogenation:

[0022]

[0023] During the nitration reaction, the reaction temperature is controlled at 80-100° C. and concentrated nitric acid is slowly added dropwise to carry out the nitration reaction. This can control the generation of more 3,4,5-trifluoronitrobenzene and avoid the generation of by-products.

[0024] After the nitration reaction is completed, water is added dropwise to the reaction solution. During the addition process, the temperature of the reaction solution is controlled at 0-20°C. The amount of water added is generally controlled at 30-40% of the weight of concentrated sulfuric acid. The purpose is to separate the reaction product and dilute sulfuric acid into layers after adding water, and to better separate the organic phase.

[0025] During the hydrogenation reaction, a palladium carbon catalyst is added, and the palladium content in the palladium carbon catalyst is 0.05-0.5wt%. The use of a palladium carbon catalyst with a lower palladium content can effectively control the generation of benzene ring defluorination impurities and increase the yield of 3,4,5-trifluoroaniline. Although the palladium carbon catalyst used in the hydrogenation reaction is expensive, the palladium content in the catalyst is low, the amount used is small, and the catalyst can be recycled and reused, so the overall cost is low.

[0026] Although the by-product 2,3,4-trifluoroaniline is produced during the reaction, the boiling points of 2,3,4-trifluoroaniline are 173.8°C and 3,4,5-trifluoroaniline are 200.4°C. They can be effectively separated from 3,4,5-trifluoroaniline in the subsequent negative pressure distillation process, and the contents of the finally obtained 2,3,4-trifluoroaniline and 3,4,5-trifluoroaniline are both above 99%.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The invention provides a novel method for preparing 3,4,5-trifluoroaniline product. 1,2,3-trifluorobenzene is used as a raw material. The yield of 3,4,5-trifluoroaniline is improved by controlling the temperature in the nitration reaction process and using a catalyst in the hydrogenation reaction process. The total yield of 3,4,5-trifluoroaniline is 30-51%.

[0029] The present invention uses 1,2,3-trifluorobenzene as a raw material. 1,2,3-trifluorobenzene is a substance that is relatively easy to prepare in the fluorobenzene industry and is easier to obtain than 2,3,4-trifluoroaniline and 3,5-dichloro-4-fluoronitrobenzene.

[0030] In the process of preparing 3,4,5-trifluoroaniline, the present invention produces a byproduct 2,3,4-trifluoroaniline. However, after separation, the contents of both products reach more than 99%, and the purity is relatively high.

[0031] The raw materials used in the invention are easy to obtain and have low cost; the amount of catalyst used in the process is small and can be reused; the obtained by-product 2,3,4-trifluoroaniline is an intermediate for synthesizing quinolone antibacterial drugs lomefloxacin, norfloxacin and ofloxacin acid, and can also generate certain economic benefits; the overall production process is simple, the obtained product has high purity, the comprehensive cost is low, and the invention is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 GC-MS spectrum of 3,4,5-trifluoronitrobenzene in the embodiment of the present invention;

[0033] Figure 2 1H NMR spectrum of 3,4,5-trifluoronitrobenzene in the embodiment of the present invention;

[0034] Figure 3 GC-MS spectrum of 2,3,4-trifluoroaniline in the embodiment of the present invention;

[0035] Figure 4 1H NMR spectrum of 2,3,4-trifluoroaniline in the embodiment of the present invention;

[0036] Figure 5 GC-MS spectrum of 3,4,5-trifluoroaniline in the embodiment of the present invention;

[0037] Figure 6 This is the 1H NMR spectrum of 3,4,5-trifluoroaniline in the examples of the present invention. DETAILED DESCRIPTION

[0038] The present invention is further described below in conjunction with examples and drawings. Those skilled in the art should understand that the examples are only used to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0039] Example 1

[0040] Add 500 g of 98% concentrated sulfuric acid and 1,2,3-trifluorobenzene (100 g, 0.75 mol) into the reaction bottle, stir and dissolve to obtain a mixed solution, then control the temperature of the mixed solution at 80-85 ° C, slowly add 68% concentrated nitric acid (104.18 g, 1.12 mol) to the mixed solution, and the addition is completed in about 2 hours. The central control monitors the remaining amount of 1,2,3-trifluorobenzene raw material in the reaction solution. The reaction is completed when the content of 1,2,3-trifluorobenzene is less than 1%. Subsequently, 150 g of water is added to the reaction solution, and the temperature of the reaction solution is controlled at 0-20 ° C. After the addition is completed, let it stand and separate the liquid to obtain an organic phase 1, which is then washed with 100 g of water, left to stand, and separated to obtain an organic phase 2 (121.45 g, 3,4,5-trifluoronitrobenzene content 36.6%) for standby use;

[0041] Figure 1 and Figure 2 The GC-MS spectrum and 1H NMR spectrum of 3,4,5-trifluoronitrobenzene were respectively. The obtained organic phase 2 was subjected to GC-MS and 1H NMR structural analysis (MS: m / z=177; 1H NMR: 7.84-7.92, 2H, m), proving that 3,4,5-trifluoronitrobenzene was generated at the end of the nitration reaction.

[0042] Put 500g methanol, 3,4,5-trifluoronitrobenzene crude product (121.45g, content 36.61%) and 0.05% palladium carbon catalyst (1.20g) into the autoclave, cover the autoclave and seal it, stir, replace with nitrogen, pass hydrogen into the autoclave to control the pressure at 0.2MPa and the temperature at 35-40°C for hydrogenation reaction, and the central control monitors that the content of 3,4,5-trifluoronitrobenzene raw material is less than 0.5%. The reaction is completed, the autoclave is cooled to room temperature, the pressure is released, and the nitrogen is replaced. The material was extracted and filtered to obtain a solid (the catalyst was used in the next batch). The filtrate was distilled to remove the solvent, and the methanol was recovered for hydrogenation reaction. The remaining material was subjected to negative pressure distillation to obtain the front fraction by-product 2,3,4-trifluoroaniline (60.07 g, 0.40 mol, content 99%) and the rear fraction product 3,4,5-trifluoroaniline (34.70 g, 0.23 mol, content 99%). After the two-step reaction, the total yield of 3,4,5-trifluoroaniline product was 31.16%.

[0043] Figure 3 and Figure 4 They are GC-MS spectrum and 1HNMR spectrum of 2,3,4-trifluoroaniline in the embodiment of the present invention respectively. The obtained front fraction is subjected to GC-MS and 1H NMR for structural analysis (MS: m / z=147, 1H NMR: 6.43-6.49, 1H, m; 6.74-6.81, 1H, m; 3.66, 2H, s), and the by-product 2,3,4-trifluoroaniline is generated.

[0044] Figure 5 and Figure 6 They are the GC-MS spectrum and 1HNMR spectrum of 3,4,5-trifluoroaniline in the embodiment of the present invention respectively. The obtained rear fraction is subjected to GC-MS and 1H NMR for structural analysis (MS: m / z=147; 1H NMR: 6.19-6.27, 1H, m; 3.69, 2H, s), and the generated substance is 3,4,5-trifluoroaniline.

[0045] Example 2

[0046] Add 1000 g of 98% concentrated sulfuric acid and 1,2,3-trifluorobenzene (100 g, 0.75 mol) into the reaction bottle, stir and dissolve to obtain a mixed solution, then control the temperature of the mixed solution at 95-100 ° C, slowly add 80% concentrated nitric acid (76.75 g, 0.97 mol), and add the solution slowly for about 3 hours. The remaining amount of 1,2,3-trifluorobenzene raw material in the central control monitoring liquid, the content of 1,2,3-trifluorobenzene is less than 1%, and the reaction is completed. Then, 300 g of water is added to the reaction solution, and the temperature of the reaction solution is controlled at 0-20 ° C. After the addition is completed, let it stand and separate the liquid to obtain an organic phase 1, which is then washed with 100 g of water, let it stand, and separate the liquid to obtain an organic phase 2 (116.8 g, 3,4,5-trifluoronitrobenzene content 48.86%) for standby use;

[0047] Put 1000g of ethanol, crude 3,4,5-trifluoronitrobenzene (116.8g, content 48.86%) and 0.5% palladium carbon catalyst (1.20g) into the autoclave, cover the autoclave and seal it, stir, replace with nitrogen, pass hydrogen into the autoclave to control the pressure at 2MPa and the temperature at 20-25°C for hydrogenation reaction, and the central control monitors that the content of 3,4,5-trifluoronitrobenzene raw material is less than 0.5%. The reaction is over, the autoclave is depressurized, replaced with nitrogen, and the reaction materials are extracted and filtered. The obtained solid is recovered (the catalyst is used in the next batch), the obtained filtrate is distilled to remove the solvent, the recovered ethanol is used for hydrogenation reaction, and the remaining material is subjected to negative pressure distillation to separate the front fraction by-product 2,3,4-trifluoroaniline (46.11 g, 0.31 mol, content 99.1%) and the rear fraction product 3,4,5-trifluoroaniline (44.06 g, 0.30 mol, content 99.05%). After two-step reaction, the total yield of 3,4,5-trifluoroaniline product is 39.56%.

[0048] Example 3

[0049] 800 g of 98% concentrated sulfuric acid and 1,2,3-trifluorobenzene (100 g, 0.75 mol) were added to the reaction bottle, stirred and dissolved to obtain a mixed solution, and then the temperature of the mixed solution was controlled at 85-90 ° C, and 98% concentrated nitric acid (53.01 g, 0.82 mol) was slowly added dropwise. The addition was completed in about 5 hours. The central control monitored the remaining amount of 1,2,3-trifluorobenzene raw material in the reaction solution. The content of 1,2,3-trifluorobenzene was less than 1%, and the reaction was completed. The temperature of the reaction solution was lowered to 0-20 ° C, and then 300 g of water was added dropwise to the reaction solution. The temperature of the reaction solution was controlled at 0-20 ° C. After the addition was completed, it was allowed to stand and separated to obtain an organic phase 1, which was then washed with 100 g of water, allowed to stand, and separated to obtain an organic phase 2 (126.09 g, 3,4,5-trifluoronitrobenzene content 57.89%) for standby use;

[0050] Put 800g toluene, crude 3,4,5-trifluoronitrobenzene (126.09g, content 57.89%) and 0.1% palladium carbon catalyst (1.20g) into the autoclave, cover the autoclave and seal it, stir, replace with nitrogen, pass hydrogen into the autoclave to control the pressure of 0.8MPa and the temperature of 10-15°C for hydrogenation reaction, control the 3,4,5-trifluoronitrobenzene raw material content to less than 0.5% and the reaction is over, cool the autoclave to room temperature, release the pressure, replace with nitrogen, and extract the reaction materials , filter, recover the solid (the catalyst is used for the next batch), distill the filtrate to remove the solvent, recover the toluene and use it for hydrogenation reaction, and separate the remaining materials by negative pressure distillation to obtain the front fraction by-product 2,3,4-trifluoroaniline (40.98 g, 0.28 mol, content 99%) and the rear fraction product 3,4,5-trifluoroaniline (56.35 g, 0.38 mol, content 99.01%). After two-step reaction, the total yield of 3,4,5-trifluoroaniline product is 50.60%.

[0051] Example 4

[0052] Add 500 g of 98% concentrated sulfuric acid and 1,2,3-trifluorobenzene (100 g, 0.75 mol) into the reaction bottle, stir and dissolve to obtain a mixed solution, then control the temperature of the mixed solution at 80-85°C, slowly add 85% concentrated nitric acid (58.34 g, 0.79 mol), and add the mixture in about 4 hours. The remaining amount of 1,2,3-trifluorobenzene raw material in the reaction solution is monitored by the central control. The reaction is completed when the content of 1,2,3-trifluorobenzene is less than 1%. The temperature of the reaction solution is lowered to 0-20°C, and then 200 g of water is added to the reaction solution. The temperature of the reaction solution is controlled at 0-20°C. After the addition is completed, the mixture is allowed to stand and separated to obtain an organic phase 1, which is then washed with 200 g of water, allowed to stand, and separated to obtain an organic phase 2 (122.11 g, 3,4,5-trifluoronitrobenzene content 61.96%) for standby use;

[0053] Put 300g methanol, crude 3,4,5-trifluoronitrobenzene (122.11g, content 61.96%) and 0.1% palladium carbon catalyst (1.20g) into the autoclave, cover the autoclave and seal it, stir, replace with nitrogen, pass hydrogen into the autoclave to control the pressure at 0.5MPa and the temperature at 25-30°C for hydrogenation reaction, control the 3,4,5-trifluoronitrobenzene raw material content to be less than 0.5% and end the reaction, release the pressure of the autoclave, replace with nitrogen, extract the reaction materials, pass through The solid was recovered by filtration (the catalyst was used in the next batch), the filtrate was distilled to remove the solvent, the methanol was recovered and used for hydrogenation reaction, and the remaining material was separated by negative pressure distillation to obtain the front fraction by-product 2,3,4-trifluoroaniline (35.08 g, 0.24 mol, content 99%) and the rear fraction product 3,4,5-trifluoroaniline (57.13 g, 0.38 mol, content 99.01%). After two-step reaction, the total yield of 3,4,5-trifluoroaniline product was 51.30%.

[0054] Comparative Example 1

[0055] Add 500 g of 98% concentrated sulfuric acid and 1,2,3-trifluorobenzene (100 g, 0.75 mol) into the reaction bottle, stir and dissolve to obtain a mixed solution, then control the temperature of the mixed solution at 10-15 ° C, slowly add 98% concentrated nitric acid (72.29 g, 1.12 mol), and add the mixture in about 4 hours. The remaining amount of 1,2,3-trifluorobenzene raw material in the reaction solution is monitored by the central control. The content of 1,2,3-trifluorobenzene is less than 1%, and the reaction is completed. The temperature of the reaction solution is controlled at 0-20 ° C, and 200 g of water is slowly added to the reaction solution. After the addition is completed, let it stand and separate the liquids. Separate the organic phase, wash it with 200 g of water, let it stand, separate the oil phase, and obtain a crude 3,4,5-trifluoronitrobenzene (119.45 g, content 11.11%);

[0056] Put 300g methanol, 3,4,5-trifluoronitrobenzene crude product (119.45g, content 11.11%) and 0.1% palladium carbon catalyst (1.20g) into the autoclave, cover the autoclave and seal it, start stirring, replace with nitrogen three times, pass hydrogen into the autoclave to control the pressure at 0.5MPa and the temperature at 25-30°C for hydrogenation reaction, control the 3,4,5-trifluoronitrobenzene raw material content to less than 0.5% and end the reaction, release the pressure of the autoclave and replace with nitrogen The reaction material was extracted and filtered to recover the catalyst, the filtrate was distilled to remove the solvent, the methanol was recovered and used for hydrogenation reaction, and the remaining material was subjected to negative pressure distillation to obtain the front fraction by-product 2,3,4-trifluoroaniline (80.19 g, 0.53 mol, content 99%) and the rear fraction product 3,4,5-trifluoroaniline (10.02 g, 0.07 mol, content 99%). After the two-step reaction, the total yield of 3,4,5-trifluoroaniline product was 9.0%.

[0057] In Comparative Example 1, during the nitration reaction, the reaction temperature was controlled too low, and the yield of the finally obtained 3,4,5-trifluoroaniline product was low.

[0058] Comparative Example 2

[0059] Add 500 g of 98% concentrated sulfuric acid and 1,2,3-trifluorobenzene (100 g, 0.75 mol) into the reaction bottle, stir and dissolve to obtain a mixed solution, then control the temperature of the mixed solution at 85-90 ° C, slowly add 98% concentrated nitric acid (57.83 g, 0.9 mol), and the addition is completed in about 4 hours. The central control monitors the remaining amount of 1,2,3-trifluorobenzene raw material in the reaction solution. The content of 1,2,3-trifluorobenzene is less than 1% and the reaction is completed. The temperature of the reaction solution is controlled at 0-20 ° C, and 200 g of water is slowly added to the reaction solution. After the addition is completed, let it stand and separate the liquids. Separate the organic phase and wash it with 200 g of water, let it stand, separate the oil phase to obtain 3,4,5-trifluoronitrobenzene crude product (123.44 g, content 51.61%);

[0060] Put 300g of methanol, crude 3,4,5-trifluoronitrobenzene (116.80g, content 13.64%) and 1% palladium carbon catalyst (1.20g) into the autoclave, cover the autoclave and seal it, start stirring, replace with nitrogen three times, pass hydrogen into the autoclave to control the pressure at 0.3MPa and the temperature at 25-30°C for hydrogenation reaction, control the 3,4,5-trifluoronitrobenzene raw material content to be less than 0.5% and end the reaction, release the pressure of the autoclave, replace with nitrogen, extract the reaction materials, filter and return The catalyst was collected, and the filtrate was distilled to remove the solvent, and the methanol was recovered for hydrogenation reaction. The remaining material was separated by negative pressure distillation to obtain the front fraction by-product 2,3,4-trifluoroaniline (30.07 g, 0.20 mol, content 99%) and the rear fraction product 3,4,5-trifluoroaniline (32.07 g, 0.21 mol, content 99%). After two-step reaction, the total yield of 3,4,5-trifluoroaniline product was 28.8%, and a large amount of benzene ring defluorination impurities generated by the by-product and the product greatly reduced the yield.

[0061] In Comparative Document 2, during the hydrogenation reaction, the palladium content in the added palladium-carbon catalyst was too high, and the yield of the final 3,4,5-trifluoroaniline product was low.

Claims

1. A process for preparing 3,4,5-trifluoroaniline, characterized in that: The steps include: 1) dissolving 1,2,3-trifluorobenzene in concentrated sulfuric acid to obtain a mixed solution, then controlling the temperature at 80-100° C., dropping concentrated nitric acid into the mixed solution, and keeping the temperature for reaction after the dropping is completed. During the reaction, the remaining amount of 1,2,3-trifluorobenzene raw material in the reaction solution is monitored by control system. When the remaining amount of 1,2,3-trifluorobenzene is less than 1wt%, the reaction is completed. Then, water is dropped into the reaction solution, and the temperature of the reaction solution is controlled at 0-20° C. After the dropping is completed, the reaction solution is allowed to stand and separated to obtain an organic phase 1, which is then washed with water, allowed to stand, and separated to obtain an organic phase 2 for standby use; 2) putting the solvent, organic phase 2 and palladium-carbon catalyst into an autoclave, sealing, stirring, and replacing with nitrogen, passing hydrogen into the autoclave to control the pressure at 0.2-2MPa and the temperature at 10-40°C to carry out a hydrogenation reaction, and after the reaction is completed, releasing the pressure, replacing with nitrogen, extracting and filtering the material, recycling the obtained solid, distilling the obtained filtrate to remove the solvent, and subjecting the remaining material to negative pressure distillation to obtain 3,4,5-trifluoroaniline; the palladium content in the palladium-carbon catalyst is 0.05-0.5wt%.

2. The preparation process according to claim 1, characterized in that: In step 1), the amount of concentrated sulfuric acid used is 5 to 10 times the weight of the 1,2,3-trifluorobenzene raw material.

3. The preparation process according to claim 1, characterized in that: In step 1), the content of concentrated nitric acid is 68% to 98%, and the amount used is 1.1 to 1.5 eq of 1,2,3-trifluorobenzene.

4. The preparation process according to claim 1, characterized in that: In step 1), after the reaction is completed, the amount of water added dropwise to the reaction solution is 30-40% of the total weight of concentrated sulfuric acid.

5. The preparation process according to claim 1, characterized in that: In step 2), the solvent is one or more of methanol, ethanol, isopropanol, and toluene, and the amount of the solvent used is 3 to 10 times the weight of the 1,2,3-trifluorobenzene raw material.

6. The preparation process according to claim 1, characterized in that: In step 2), 2,3,4-trifluoroaniline is obtained during the negative pressure distillation process.

7. The preparation process according to claim 1, characterized in that: In step 2), the remaining amount of 3,4,5-trifluoronitrobenzene in the reaction solution is monitored during the hydrogenation reaction, and the reaction is terminated when the remaining amount of 3,4,5-trifluoronitrobenzene is less than 0.5 wt%.

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