A method for separating and utilizing 2,4-dichloro-5-fluoroacetophenone mother liquor

Abstract

The invention belongs to the technical field of organic chemical production, and discloses a method for separating and utilizing a 2,4-dichloro-5-fluoroacetophenone mother liquor. The method comprises the following steps: firstly preparing a mixed acid from 98% sulfuric acid and fuming nitric acid, then dropping the mixed acid into a mother liquor containing 2,4-dichloro-5-fluoroacetophenone and 2,6-dichloro-3-fluoroacetophenone, heating, keeping the temperature for reaction, standing for stratification, and subjecting an organic phase to vacuum distillation to obtain 2,4-dichloro-5-fluoroacetophenone; adding tetramethylammonium chloride, potassium fluoride and DMF to a residual bottom liquid, heating the liquid to react, filtering, decompressing the filtrate to remove DMF, then adding a sodium hypochlorite solution, keeping the temperature for stirring, adjusting the pH value, filtering and collecting a solid, obtaining 5-nitro-2,3,6-trifluorobenzoic acid, and then adding a quinoline solvent and a cuprous oxide catalyst; heating the liquid under nitrogen protection, and distilling to obtain 2,4,5-trifluoronitrobenzene. The present invention can effectively separate 2,4-dichloro-5-fluoroacetophenone and 2,6-difluoro-3-fluoroacetophenone in a mother liquor, and prepare 2,4,5-trifluoronitrobenzene; the production cost is reduced and considerable economic benefits are brought about.

Description

Technical Field

[0001] The invention belongs to the technical field of organic chemical production, and specifically relates to a method for separating and utilizing 2,4-dichloro-5-fluoroacetophenone mother liquor. Background Art

[0002] 2,4-dichloro-5-fluoroacetophenone is an important intermediate in the production of quinolone drugs such as ciprofloxacin. The main synthesis method is to use 2,4-dichlorofluorobenzene and acetyl chloride as raw materials for Friedel-Crafts reaction, which will inevitably produce 2,6-dichloro-3-fluoroacetophenone as a by-product. When 2,4-dichloro-5-fluoroacetophenone is separated and purified by crystallization in the later stage of production, it is inevitable to obtain some 2,4-dichloro-5-fluoroacetophenone and 2,6-dichloro-3-fluoroacetophenone, each accounting for 50% of the crystallization mother liquor. This part of the mother liquor is difficult to handle. Although there are many existing treatment methods, each has its own defects. For example, patent CN104496772A is a method for purifying acetophenone crystallization mother liquor. Because hydrazine hydrate is used as an auxiliary material, the cost is relatively high; although hydrazine sulfate by-product can be obtained, the acid hydrolysis catalyst contained therein will affect the quality. Patent CN101747167A reports a method for recovering 2,4-dichloro-5-fluoroacetophenone from acetophenone crystal mother liquor, which requires the generation of ketal. Since ketal has a high boiling point, the distillation separation conditions are harsh; the neopentyl glycol used has good water solubility, the recovery rate is only about 80%, and a large amount of auxiliary reagent neopentyl glycol will be lost during the separation process. There are also some technologies that have been disclosed, and the separation process is complicated and cumbersome, which is not easy to carry out industrial production. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a method for separating and utilizing 2,4-dichloro-5-fluoroacetophenone mother liquor, which overcomes the defects in the prior art, can effectively separate 2,4-dichloro-5-fluoroacetophenone from 2,6-dichloro-3-fluoroacetophenone in the mother liquor, and prepare 2,4,5-trifluoronitrobenzene; and reduces production costs while bringing considerable economic benefits.

[0004] In order to solve the above technical problems, the technical solution of the present invention is:

[0005] A method for separating and utilizing 2,4-dichloro-5-fluoroacetophenone mother liquor comprises the following steps:

[0006] a. First, prepare a mixed acid by adding 98% sulfuric acid (compared with the mass of 2,6-dichloro-3-fluoroacetophenone in the mother liquor, each batch is tested in actual production) with a mass multiple of 0.43 to 0.61 times the mass of 2,6-dichloro-3-fluoroacetophenone in the mother liquor and 1.0 to 1.1 equivalents of fuming nitric acid (the amount of 2,6-dichloro-3-fluoroacetophenone in the mother liquor is regarded as 1.0 equivalent); at 0°C, drop the mixed acid into the mother liquor containing 2,4-dichloro-5-fluoroacetophenone and 2,6-dichloro-3-fluoroacetophenone, and add the mixed acid dropwise. After the acid is completed, the temperature is raised to 60-100°C and the reaction is kept at this temperature for 2-5 hours. After the reaction is completed, the reaction is allowed to stand for stratification and the upper organic phase is separated. The organic phase is washed with an equal weight of water for 1 hour and the aqueous phase is separated. The organic phase is then subjected to vacuum distillation and the fractions are collected to obtain 2,4-dichloro-5-fluoroacetophenone. The residual bottom liquid from the distillation is transferred to a reactor and (in no particular order) 0.05-0.15 equivalents of tetramethylammonium chloride, 2.1-2.3 equivalents of potassium fluoride, and DMF twice the mass of 2,6-dichloro-3-fluoroacetophenone in the mother liquor are added. (N, N-dimethylformamide), heated to 100-140°C and reacted for 5-7h; after the reaction, the reaction system was filtered; the filtrate obtained by filtration was decompressed to remove DMF; after removing DMF, 4.0-6.0 equivalents of 10% mass concentration sodium hypochlorite aqueous solution were added to the remaining filtrate, and the mixture was stirred at 80°C-100°C for 3-5h; the pH value of the system was adjusted to 1, and the precipitated solid was collected by filtration to obtain 5-nitro-2,3,6-trifluorobenzoic acid;

[0007] b. Add the 5-nitro-2,3,6-trifluorobenzoic acid obtained in step a into a reaction kettle, add quinoline solvent with a mass of 4 to 8 times that of 5-nitro-2,3,6-trifluorobenzoic acid, and 0.05 to 0.15 equivalents of cuprous oxide catalyst; react at 100 to 140° C. for 8 to 12 hours under nitrogen protection; after the reaction, perform vacuum distillation to obtain 2,4,5-trifluoronitrobenzene.

[0008] Preferably, in step a, a mixed acid is prepared by adding sulfuric acid having a mass concentration of 98% of the mass of 2,6-dichloro-3-fluoroacetophenone in the mother liquor and 1.05 equivalents of fuming nitric acid.

[0009] Preferably, after the mixed acid is added dropwise in step a, the temperature is raised to 80° C. and the reaction is kept at this temperature for 3 hours.

[0010] Preferably, the pressure of the reduced pressure distillation of the organic phase in step a is a vacuum degree of 100 kPa and a temperature of 100°C.

[0011] Preferably, in step a, 0.1 equivalent of tetramethylammonium chloride and 2.2 equivalents of potassium fluoride are added, and the temperature is raised to 120° C. and the reaction is carried out for 6 hours.

[0012] Preferably, in the step a, the pressure in the DMF removal under reduced pressure is 96 kPa and the temperature is 80°C.

[0013] Preferably, the pH value of the system is adjusted in step a by using a hydrochloric acid solution with a mass concentration of 10%.

[0014] Preferably, in step b, quinoline solvent with a mass of 6 times that of 5-nitro-2,3,6-trifluorobenzoic acid and 0.1 equivalent of cuprous oxide catalyst are added; and the reaction is carried out at 120° C. for 10 hours under nitrogen protection.

[0015] Preferably, the pressure of the vacuum distillation in step b is 96 kPa, and the fraction at a temperature of 79° C. is collected.

[0016] Due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0017] The invention realizes separation and recovery of 2,4-dichloro-5-fluoroacetophenone with a high recovery rate from acetophenone crystal mother liquor through nitration reaction, and simultaneously synthesizes 2,4,5-trifluoronitrobenzene with a high yield through fluorination, oxidation and decarboxylation reaction of the byproduct 2,6-dichloro-3-fluoroacetophenone; 2,4,5-trifluoronitrobenzene is an important chemical intermediate for synthesizing chemical products such as 1,2,4-trifluorobenzene, 2,4,5-trifluorophenylacetic acid and 2,4,5-trifluoroaniline, so the invention can produce important chemical intermediates while reducing industrial production costs, thereby bringing additional considerable economic benefits.

[0018] In conclusion, the present invention can effectively separate 2,4-dichloro-5-fluoroacetophenone from 2,6-dichloro-3-fluoroacetophenone in the mother liquor and prepare 2,4,5-trifluoronitrobenzene, thereby reducing production costs and bringing considerable economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Gas chromatogram of 5-nitro-2,3,6-trifluorobenzoic acid, the product of Example 18 of the present invention;

[0020] Figure 2 Gas chromatogram of 2,4-dichloro-5-fluoroacetophenone, the product of Example 2 of the present invention. DETAILED DESCRIPTION

[0021] The present invention will be further described below in conjunction with the embodiments. Example 1

[0022] A mixed acid was prepared by mixing 108 g of sulfuric acid (0.52 times the mass of 2,6-dichloro-3-fluoroacetophenone in the mother liquor; the mass of 2,6-dichloro-3-fluoroacetophenone in each batch of mother liquor was tested during actual production) and 63.01 g of fuming nitric acid (1 equivalent, equivalent to the amount of 2,6-dichloro-3-fluoroacetophenone in the mother liquor). At 0°C, the mixed acid was dropped into 414.06g of mother liquor (the amount of 2,6-dichloro-3-fluoroacetophenone in the mother liquor was 207.03g, which was regarded as 1 equivalent); after the addition of the mixed acid was completed, the temperature was raised to 80°C and the reaction was kept at this temperature for 3h; after the reaction was completed, the upper organic phase was allowed to stand and the upper organic phase was separated; the organic phase was washed with an equal mass of water for 1h, and the aqueous phase was separated; then the organic phase was subjected to vacuum distillation at a vacuum degree of 100kPa and a temperature of 100°C, and the fraction 2,4-dichloro-5-fluoroacetophenone was collected; the residual bottom liquid was transferred to a reactor, 116.90g of potassium fluoride (2.1 equivalents), 5.48g of tetramethylammonium chloride (0.05 equivalents), and 414.06g of DMF (twice the mass of 2,6-dichloro-3-fluoroacetophenone in the mother liquor) were added, and the temperature was raised to 140°C for reaction for 6h; after the reaction was completed, the reaction system was filtered. The filtrate obtained by filtration was decompressed to remove DMF under vacuum at 96 kPa and 80°C; after removing DMF, 2977.60 g of 10% mass concentration sodium hypochlorite aqueous solution (4 equivalents) was added to the remaining filtrate, and the mixture was stirred at 90°C for 4 hours; then the pH value of the system was adjusted to 1 with 10% mass concentration hydrochloric acid solution, and the precipitated solid was filtered to obtain 5-nitro-2,3,6-trifluorobenzoic acid. The yield of 5-nitro-2,3,6-trifluorobenzoic acid was 170.75 g, the purity was 97.88%, and the yield was 75.59%; the yield of 2,4-dichloro-5-fluoroacetophenone was 203.36 g, the purity was 97.89%, and the recovery rate was 96.16%. Example 2

[0023] The amount of nitric acid used in Example 1 was changed to 66.16 g (1.05 equivalents), and the other operations were the same. The yield of 5-nitro-2,3,6-trifluorobenzoic acid was 182.35 g, the purity was 97.46%, and the yield was 80.39%; the yield of 2,4-dichloro-5-fluoroacetophenone was 195.57 g, the purity was 99.29%, and the recovery rate was 93.79%. Example 3

[0024] The amount of nitric acid used in Example 1 was changed to 69.31 g (1.10 equivalents), and the other operations were the same. The yield of 5-nitro-2,3,6-trifluorobenzoic acid was 183.53 g, the purity was 96.36%, and the yield was 79.99%; the yield of 2,4-dichloro-5-fluoroacetophenone was 186.62 g, the purity was 99.90%, and the recovery rate was 90.05%.

[0025] Comparative Examples 1 to 3 show that the yield of 5-nitro-2,3,6-trifluorobenzoic acid increases with the increase of nitric acid dosage when the nitric acid dosage is 1.00 equivalent to 1.10 equivalent. When the nitric acid dosage is greater than 1.05 equivalent, the yield of 5-nitro-2,3,6-trifluorobenzoic acid does not change much, with a maximum of 80.39%. Therefore, the preferred dosage of nitric acid is 1.05 equivalent. Example 4

[0026] In Example 2, the amount of sulfuric acid was changed to 90.00 g (0.43 times the mass of 2,6-dichloro-3-fluoroacetophenone in the mother liquor), and the other operations were the same. The yield of 5-nitro-2,3,6-trifluorobenzoic acid was 173.05 g, the purity was 97.12%, and the yield was 76.02%; the yield of 2,4-dichloro-5-fluoroacetophenone was 197.90 g, the purity was 93.48%, and the recovery rate was 97.80%. Example 5

[0027] In Example 2, the amount of sulfuric acid was changed to 126.00 g (0.61 times the mass of 2,6-dichloro-3-fluoroacetophenone in the mother liquor), and the other operations were the same. The yield of 5-nitro-2,3,6-trifluorobenzoic acid was 183.84 g, the purity was 96.42%, and the yield was 80.17%; the yield of 2,4-dichloro-5-fluoroacetophenone was 188.07 g, the purity was 99.79%, and the recovery rate was 90.65%.

[0028] Comparative Examples 2, 4-5 show that when the amount of sulfuric acid used is in the range of 0.43-0.61 times the mass of 2,6-dichloro-3-fluoroacetophenone in the mother liquor, the yield of 5-nitro-2,3,6-trifluorobenzoic acid ranges from 76.02% to 80.39%, wherein the maximum yield of 5-nitro-2,3,6-trifluorobenzoic acid is 80.39% when the amount of sulfuric acid used is 0.52 times. Therefore, the amount of sulfuric acid used is preferably 0.52 times. Example 6

[0029] In Example 2, the temperature was changed to 100° C. after the mixed acid was added, and the other operations were the same. The yield of 5-nitro-2,3,6-trifluorobenzoic acid was 175.36 g, the purity was 98.15%, and the yield was 77.85%; the yield of 2,4-dichloro-5-fluoroacetophenone was 194.85 g, the purity was 98.55%, and the recovery rate was 92.75%. Example 7

[0030] In Example 2, the temperature was changed to 60° C. after the mixed acid was added, and the other operations were the same. The yield of 5-nitro-2,3,6-trifluorobenzoic acid was 167.56 g, the purity was 98.00%, and the yield was 74.27%; the yield of 2,4-dichloro-5-fluoroacetophenone was 205.97 g, the purity was 96.93%, and the recovery rate was 96.43%.

[0031] Comparison of Examples 2, 6 to 7 shows that the yield of 5-nitro-2,3,6-trifluorobenzoic acid ranges from 74.27% to 80.39% at a temperature range of 60 to 100° C. after adding the mixed acid, and the maximum yield of 5-nitro-2,3,6-trifluorobenzoic acid is 80.39% at 80° C. Therefore, the temperature after adding the mixed acid is preferably 80° C. Example 8

[0032] In Example 2, the holding time after adding the mixed acid was changed to 2 h, and the other operations were the same. The yield of 5-nitro-2,3,6-trifluorobenzoic acid was 171.33 g, the purity was 97.91%, and the yield was 75.87%; the yield of 2,4-dichloro-5-fluoroacetophenone was 201.41 g, the purity was 98.57%, and the recovery rate was 95.90%. Example 9

[0033] In Example 2, the holding time after adding the mixed acid was changed to 5 h, and the other operations were the same. The yield of 5-nitro-2,3,6-trifluorobenzoic acid was 182.10 g, the purity was 97.52%, and the yield was 80.33%; the yield of 2,4-dichloro-5-fluoroacetophenone was 194.02 g, the purity was 99.64%, and the recovery rate was 93.38%.

[0034] Comparative Examples 2, 8-9 show that the yield of 5-nitro-2,3,6-trifluorobenzoic acid ranges from 75.87% to 80.39% when the temperature is kept for 2-5 hours after the addition of the mixed acid, wherein the maximum yield of 5-nitro-2,3,6-trifluorobenzoic acid is 80.39% at 3 hours, and the yield does not change much when the time is extended. Therefore, the temperature is preferably kept for 3 hours after the addition of the mixed acid.

[0035] Compared with Examples 1 to 9, in Example 2, the recovery rate of 2,4-dichloro-5-fluoroacetophenone is 93.79% and the purity is 99.29%. This condition can not only improve the yield of 5-nitro-2,3,6-trifluorobenzoic acid, but also recover 2,4-dichloro-5-fluoroacetophenone with high recovery rate and high purity. Example 10

[0036] In Example 2, the amount of potassium fluoride was changed to 127.82 g (2.2 equivalents), and the other operations were the same. The yield of 5-nitro-2,3,6-trifluorobenzoic acid was 186.09 g, the purity was 97.44%, and the yield was 82.01%. Since the operation before the recovery of 2,4-dichloro-5-fluoroacetophenone was not changed, the recovery rate and purity were the same as in Example 2, and no further description was given; the subsequent examples were the same. Embodiment 11

[0037] The amount of potassium fluoride in Example 2 was changed to 133.63 g (2.3 equivalents), and the other operations were the same to obtain 185.90 g of 5-nitro-2,3,6-trifluorobenzoic acid with a purity of 97.45% and a yield of 81.94%.

[0038] Comparative Examples 2, 10-11 show that the yield of 5-nitro-2,3,6-trifluorobenzoic acid ranges from 80.39% to 82.01% when the amount of potassium fluoride is 2.1-2.3 equivalents, wherein the yield of 5-nitro-2,3,6-trifluorobenzoic acid is 82.01% at 2.2 equivalents, and the yield does not change much when the amount of potassium fluoride is further increased. Therefore, the amount of potassium fluoride is preferably 2.2 equivalents. Example 12

[0039] In Example 10, the amount of tetramethylammonium chloride used was changed to 10.96 g (0.10 equivalent), and the remaining operations were the same. The yield of 5-nitro-2,3,6-trifluorobenzoic acid was 191.33 g, the purity was 97.41%, and the yield was 84.29%. Example 13

[0040] In Example 10, the amount of tetramethylammonium chloride used was changed to 16.44 g (0.15 equivalent), and the remaining operations were the same. The yield of 5-nitro-2,3,6-trifluorobenzoic acid was 189.31 g, the purity was 97.43%, and the yield was 83.42%.

[0041] Comparative Examples 10, 12-13 show that when the amount of tetramethylammonium chloride is 0.05-0.15 equivalents, the yield of 5-nitro-2,3,6-trifluorobenzoic acid ranges from 82.01% to 84.29%, wherein the yield of 5-nitro-2,3,6-trifluorobenzoic acid is the highest at 84.29% at 0.10 equivalents. Therefore, the amount of tetramethylammonium chloride used is preferably 0.10 equivalents. Embodiment 14

[0042] In Example 12, after tetramethylammonium chloride, potassium fluoride and DMF were added, the temperature was changed to 120° C., and the remaining operations were the same. 5-nitro-2,3,6-trifluorobenzoic acid was obtained in an amount of 192.68 g, a purity of 97.44%, and a yield of 84.92%. Embodiment 15

[0043] In Example 12, after tetramethylammonium chloride, potassium fluoride and DMF were added, the temperature was changed to 100° C., and the remaining operations were the same. The yield of 5-nitro-2,3,6-trifluorobenzoic acid was 185.77 g, the purity was 97.50%, and the yield was 81.92%.

[0044] Comparative Examples 12, 14-15 show that after adding tetramethylammonium chloride, potassium fluoride and DMF, the temperature range is 100-140°C, and the yield of 5-nitro-2,3,6-trifluorobenzoic acid ranges from 81.92% to 84.92%. Among them, at 120°C, the yield of 5-nitro-2,3,6-trifluorobenzoic acid is the highest at 84.92%. Therefore, the temperature is preferably 120°C. Example 16

[0045] In Example 14, after tetramethylammonium chloride, potassium fluoride and DMF were added, the holding time was changed to 7 h, and the other operations were the same to obtain 191.79 g of 5-nitro-2,3,6-trifluorobenzoic acid with a purity of 97.40% and a yield of 84.49%. Embodiment 17

[0046] In Example 14, after tetramethylammonium chloride, potassium fluoride and DMF were added, the holding time was changed to 5 h, and the other operations were the same to obtain 185.94 g of 5-nitro-2,3,6-trifluorobenzoic acid with a purity of 97.44% and a yield of 81.95%.

[0047] Comparative Examples 14, 16-17 show that after adding tetramethylammonium chloride, potassium fluoride and DMF, the holding time ranges from 5 to 7 hours, and the yield of 5-nitro-2,3,6-trifluorobenzoic acid ranges from 81.95% to 84.92%. Among them, the yield of 5-nitro-2,3,6-trifluorobenzoic acid is the highest at 84.92% at 6 hours. Therefore, the preferred holding time is 6 hours. Embodiment 18

[0048] In Example 14, the amount of 10% sodium hypochlorite solution was changed to 3722.00 g (5.0 equivalents), and the remaining operations were the same. The yield of 5-nitro-2,3,6-trifluorobenzoic acid was 205.51 g, the purity was 97.43%, and the yield was 90.56%. Embodiment 19

[0049] The amount of 10% sodium hypochlorite solution in Example 14 was changed to 4466.40 g (6.0 equivalents), and the remaining operations were the same. The yield of 5-nitro-2,3,6-trifluorobenzoic acid was 205.26 g, the purity was 97.39%, and the yield was 90.42%.

[0050] Comparative Examples 14, 18-19 show that the dosage of 10% sodium hypochlorite solution ranges from 4.0 to 6.0 equivalents, and the yield of 5-nitro-2,3,6-trifluorobenzoic acid ranges from 84.92% to 90.56%. Among them, at 5.0 equivalents, the yield of 5-nitro-2,3,6-trifluorobenzoic acid is the highest at 90.56%, and there is no significant change in the yield when the sodium hypochlorite dosage is further increased. Therefore, the dosage of 10% sodium hypochlorite solution is preferably 5.0 equivalents. Embodiment 20

[0051] After adding sodium hypochlorite in Example 18, the temperature was changed to 100° C., and the other operations were the same. The yield of 5-nitro-2,3,6-trifluorobenzoic acid was 205.58 g, the purity was 97.40%, and the yield was 90.57%. Embodiment 21

[0052] After adding sodium hypochlorite in Example 18, the temperature was changed to 80° C., and the other operations were the same. The yield of 5-nitro-2,3,6-trifluorobenzoic acid was 194.92 g, the purity was 97.43%, and the yield was 85.90%.

[0053] Comparative Examples 18, 20-21 show that the temperature range after adding sodium hypochlorite is 80-100°C, and the yield of 5-nitro-2,3,6-trifluorobenzoic acid ranges from 85.90% to 90.57%. When the temperature reaches 80°C, the yield remains basically unchanged, and the yield of 5-nitro-2,3,6-trifluorobenzoic acid is 90.56% at 90°C. Therefore, the temperature after adding sodium hypochlorite is preferably 90°C. Embodiment 22

[0054] The holding time after adding sodium hypochlorite in Example 18 was changed to 3 h, and the other operations were the same. The yield of 5-nitro-2,3,6-trifluorobenzoic acid was 198.53 g, the purity was 97.42%, and the yield was 87.48%. Embodiment 23

[0055] The holding time after adding sodium hypochlorite in Example 18 was changed to 5 h, and the other operations were the same. The yield of 5-nitro-2,3,6-trifluorobenzoic acid was 204.98 g, the purity was 97.40%, and the yield was 90.30%.

[0056] Comparative Examples 18, 22-23 show that after adding sodium hypochlorite, the holding time ranges from 3 to 5 hours, and the yield of 5-nitro-2,3,6-trifluorobenzoic acid ranges from 87.48% to 90.57%. When the holding time reaches 4 hours, the yield remains basically unchanged, and the yield of 5-nitro-2,3,6-trifluorobenzoic acid is 90.56% at 4 hours. Therefore, the holding time after adding sodium hypochlorite is preferably 4 hours. Embodiment 24

[0057] 221.09g of 5-nitro-2,3,6-trifluorobenzoic acid (regarded as 1 equivalent) was added to the reactor, and 1326.54g (6 times the mass of 5-nitro-2,3,6-trifluorobenzoic acid) of quinoline solvent and 14.31g (0.1 equivalent) of cuprous oxide catalyst were added. The temperature was raised to 120°C under nitrogen protection and the reaction was carried out for 10 hours. After the reaction was completed, 2,4,5-trifluoronitrobenzene was obtained by vacuum distillation. The yield of 2,4,5-trifluoronitrobenzene was 159.81g, the purity was 99.86%, and the yield was 95.77%. Embodiment 25

[0058] In Example 24, the amount of cuprous oxide used was changed to 7.15 g (0.1 equivalent), and the other operations were the same. The yield of 2,4,5-trifluoronitrobenzene was 160.00 g, the purity was 99.88%, and the yield was 90.25%. Embodiment 26

[0059] The amount of cuprous oxide used in Example 24 was changed to 21.46 g (0.15 equivalents), and the remaining operations were the same to obtain 171.23 g of 2,4,5-trifluoronitrobenzene with a purity of 99.16% and a yield of 95.89%.

[0060] Comparative Examples 24 to 26 show that the cuprous oxide dosage ranges from 0.05 to 0.15 equivalents, and the 2,4,5-trifluoronitrobenzene yield ranges from 95.77% to 95.89%. When the cuprous oxide dosage is greater than 0.10, the 2,4,5-trifluoronitrobenzene yield remains substantially unchanged. Therefore, the cuprous oxide dosage is preferably 0.10 equivalents. Embodiment 27

[0061] The amount of quinoline in Example 24 was changed to 884.36 g (4 times the mass of 5-nitro-2,3,6-trifluorobenzoic acid), and the remaining operations were the same to obtain 164.47 g of 2,4,5-trifluoronitrobenzene with a purity of 99.57% and a yield of 92.48%. Embodiment 28

[0062] The amount of quinoline in Example 24 was changed to 1768.72 g (8 times the mass of 5-nitro-2,3,6-trifluorobenzoic acid), and the remaining operations were the same to obtain 166.94 g of 2,4,5-trifluoronitrobenzene with a purity of 99.88% and a yield of 94.16%.

[0063] Comparative Examples 24, 27-28 show that the amount of quinoline used ranges from 4 to 8 times the mass of 5-nitro-2,3,6-trifluorobenzoic acid, and the yield of 2,4,5-trifluoronitrobenzene ranges from 92.48% to 95.77%. Among them, the yield is the highest at 95.77% when the amount of quinoline used is 6 times the mass of 5-nitro-2,3,6-trifluorobenzoic acid. Therefore, the amount of quinoline used is preferably 6 times the mass of 5-nitro-2,3,6-trifluorobenzoic acid. Embodiment 29

[0064] The reaction temperature in Example 24 was changed to 140° C., and the other operations were the same. The yield of 2,4,5-trifluoronitrobenzene was 159.76 g, the purity was 99.41%, and the yield was 89.69%. Embodiment 30

[0065] The reaction temperature in Example 24 was changed to 100° C., and the other operations were the same. The yield of 2,4,5-trifluoronitrobenzene was 162.51 g, the purity was 99.24%, and the yield was 91.08%.

[0066] Comparison of Examples 24, 29 to 30 shows that the reaction temperature ranges from 100 to 140°C, and the yield of 2,4,5-trifluoronitrobenzene ranges from 89.69% to 95.77%. Among them, the yield is the highest at 95.77% when the reaction temperature is 120°C. Therefore, the reaction temperature is preferably 120°C. Embodiment 31

[0067] The reaction time in Example 24 was changed to 8 h, and the other operations were the same. The yield of 2,4,5-trifluoronitrobenzene was 160.35 g, the purity was 99.49%, and the yield was 90.09%. Embodiment 32

[0068] The reaction time in Example 24 was changed to 12 h, and the other operations were the same to obtain 169.46 g of 2,4,5-trifluoronitrobenzene with a purity of 99.54% and a yield of 95.25%.

[0069] Comparative Examples 24, 31-32 show that the reaction time ranges from 8 to 12 hours, and the yield of 2,4,5-trifluoronitrobenzene ranges from 80.09% to 95.77%. Among them, the yield reaches a maximum of 95.77% after the reaction time reaches 10 hours, and then basically does not change with time. Therefore, the reaction time is preferably 10 hours.

[0070] It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope limited by the appended claims of the application.

Claims

1. A method for separating and utilizing 2,4-dichloro-5-fluoroacetophenone mother liquor, characterized in that: The following steps are involved: a. First, prepare a mixed acid with 98% mass concentration of sulfuric acid and 1.05 equivalents of fuming nitric acid, the mass multiple of which is 0.52 times the mass of 2,6-dichloro-3-fluoroacetophenone in the mother liquor, wherein the amount of 2,6-dichloro-3-fluoroacetophenone in the mother liquor is regarded as 1.0 equivalent; at a temperature of 0°C, drop the mixed acid into the mother liquor containing 2,4-dichloro-5-fluoroacetophenone and 2,6-dichloro-3-fluoroacetophenone, after the addition of the mixed acid is completed, heat the temperature to 80°C, and keep the temperature for reaction for 3 hours; after the reaction is completed, stand the mixture for stratification and separate the upper organic phase; wash the organic phase with an equal weight of water for 1 hour, and then separate the aqueous phase; then perform vacuum distillation on the organic phase, collect the fractions to obtain 2, 4-dichloro-5-fluoroacetophenone; the residual bottom liquid of the distillation is transferred to a reaction kettle, 0.1 equivalent of tetramethylammonium chloride, 2.2 equivalents of potassium fluoride, and DMF twice the mass of 2,6-dichloro-3-fluoroacetophenone in the mother liquor are added, and the temperature is raised to 120°C for reaction for 6 hours; after the reaction is completed, the reaction system is filtered; the filtrate obtained by filtration is decompressed to remove DMF; after removing DMF, 4.0 to 6.0 equivalents of 10% mass concentration of sodium hypochlorite aqueous solution are added to the remaining filtrate, and the mixture is stirred at 80°C to 100°C for 3 to 5 hours; the pH value of the system is adjusted to 1, and the precipitated solid is collected by filtration to obtain 5-nitro-2,3,6-trifluorobenzoic acid; b. Add the 5-nitro-2,3,6-trifluorobenzoic acid obtained in step a into a reactor, add quinoline solvent with a mass that is 6 times that of 5-nitro-2,3,6-trifluorobenzoic acid, and 0.1 equivalent of cuprous oxide catalyst; react at 120° C. for 10 h under nitrogen protection; after the reaction, perform vacuum distillation to obtain 2,4,5-trifluoronitrobenzene.

2. The method for separating and utilizing 2,4-dichloro-5-fluoroacetophenone mother liquor as claimed in claim 1, characterized in that: The pressure of the reduced pressure distillation of the organic phase in step a is a vacuum degree of 100 kPa and a temperature of 100°C.

3. The method for separating and utilizing 2,4-dichloro-5-fluoroacetophenone mother liquor as claimed in claim 1, characterized in that: In the step a, the pressure during the decompression to remove DMF is 96 kPa and the temperature is 80°C.

4. The method for separating and utilizing 2,4-dichloro-5-fluoroacetophenone mother liquor as claimed in claim 1, characterized in that: The pressure of the vacuum distillation in step b is 96 kPa, and the fraction at a temperature of 79° C. is collected.

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