Preparation method of p-chlorobenzotrifluoride

Abstract

The invention discloses a preparation method of p-chlorobenzotrifluoride, and belongs to the technical field of fluorine-containing carbocyclic compounds, the preparation method comprises the following steps: preparation of carbazolyl copolymer microspheres, chlorination reaction, fluorination reaction and rectification; according to the invention, a four-tower series continuous chlorination reaction system is adopted, each reaction tower independently controls the ultraviolet light power and temperature, and the chlorination reaction is intensified in a segmented manner, so that high-efficiency reaction in the front, middle and later stages is realized; the first tower is mainly used for monochlorination, the second tower is used for deepening dichlorination, the third tower and the fourth tower are used for realizing efficient conversion of polychlorinated products, the reaction time is shortened, the generation of side reaction impurities is reduced, the energy consumption is reduced, the yield and purity of target products are improved, the temperature rise in the reaction process is easier to control, and the safety of the reaction process is further improved. The purity of the parachlorobenzotrifluoride prepared by the method disclosed by the invention is 99.61 to 99.72 percent, and the two-step yield of the parachlorobenzotrifluoride is 96.48 to 96.65 percent.

Description

Technical Field

[0001] The present invention belongs to the technical field of fluorinated carbocyclic compounds, and particularly relates to a preparation method of p-chlorobenzotrifluoride. Background Art

[0002] P-chlorobenzotrifluoride is an important raw material for chemical pesticides and biopharmaceuticals, mainly used for the production of a series of fluorinated pesticides, such as insecticides and herbicides. Fluorinated aromatic hydrocarbons can also be used to synthesize medical drugs such as sedatives and diuretics. In addition, some fluorinated aromatic hydrocarbons are applied in the printing and dyeing industry to make the color more vivid.

[0003] The prior art uses p-chlorotoluene as a raw material, azobisisobutyronitrile or ultraviolet light as an initiator, and reacts with chlorine gas under certain conditions to synthesize p-chlorobenzotrichloride, and then p-chlorobenzotrifluoride is obtained through a fluorination reaction; when using azobisisobutyronitrile as an initiator, this initiator is a low-temperature catalyst with a low decomposition temperature, and the initiation reaction is relatively violent and has a high risk; and it needs to be added manually at regular intervals, with a small addition amount and a high frequency, making it difficult to achieve automation and mechanization; when using ultraviolet light as an initiator, the reaction rate in the initiation process is slow, and the reaction impurities are relatively high; and the dosage of chlorine gas is relatively high, about twice the theoretical amount; the fluorination reaction process requires a high pressure and has low safety; the yield of p-chlorobenzotrifluoride in the existing production process of producing p-chlorobenzotrifluoride with p-chlorotoluene as a raw material is relatively low, less than 90%.

[0004] CN102603471A discloses a production method of p-chlorobenzotrifluoride, which includes adding p-chlorotoluene to a chlorination kettle, introducing chlorine gas and carrying out chlorination at 90 - 100°C for 16 - 20 hours. After the chlorination is completed, hydrogen chloride is removed to obtain p-chlorobenzotrichloromethylbenzene; adding the obtained p-chlorobenzotrichloromethylbenzene to a high-pressure fluorination kettle, introducing HF, and carrying out a fluorination reaction at 1.5 MPa and 100°C for 6 - 8 hours to obtain p-chlorobenzotrifluoride. This method is simple and easy to operate, and the content of the product after rectification reaches more than 99.5%. However, in the chlorination reaction step using ultraviolet light as an initiator, p-chlorobenzotrichloride is prepared by one-time initiation chlorination. The reaction rate in the initiation process is slow, benzene ring chlorination by-products are easily generated in the later stage of chlorination, and they are not easy to remove. The yield of intermediate products is low, and the raw material utilization rate is low, resulting in an increase in production cost; and there are problems such as slow reaction rate, low selectivity, and unstable product quality in the fluorination process. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the present invention provides a preparation method of p-chlorobenzotrifluoride, which can improve the yield of p-chlorobenzotrifluoride, reduce the chlorine gas dosage in the chlorination reaction, shorten the reaction time, increase the chlorination rate, reduce the pressure in the fluorination reaction, improve the operation safety, and increase the product yield.

[0006] To solve the above technical problems, the technical solutions adopted by the present invention are as follows: A preparation method of p-chlorobenzotrifluoride, comprising the following steps: preparation of carbazole-based copolymer microspheres, chlorination reaction, fluorination reaction, rectification; The preparation method of the carbazole-based copolymer microspheres is as follows: Dissolve 2,4,5,6-tetra(9-carbazolyl)-isophthalonitrile in N,N-dimethylformamide, add triethylamine as an acid-binding agent, dropwise add acryloyl chloride under an ice bath, stir at room temperature for 10-14 hours. After the reaction, precipitate and purify with ether, and dry to obtain a pretreated carbazole-based material; Add the pretreated carbazole-based material, crosslinking agent and photoinitiator to acetonitrile, stir evenly, ultrasonically disperse for 10-15 min to form a uniform oil phase. Drop the oil phase into the water phase containing a dispersant, stir at a speed of 6000-8000 rpm for 10-15 min to form a stable oil-in-water emulsion, then adjust the stirring speed to 800-1200 rpm to control the droplet size, control the system temperature at 25-35 °C, irradiate with light of 365 nm wavelength for 20-30 min to initiate the crosslinking of acrylate groups in the ionic liquid. After the crosslinking, centrifuge at a speed of 3000-5000 rpm for 10-15 min, collect the microsphere product, wash it alternately with water and ethanol 2-3 times to remove unreacted monomers and dispersants, and vacuum dry to obtain carbazole-based copolymer microspheres; The mass ratio of 2,4,5,6-tetra(9-carbazolyl)-isophthalonitrile, N,N-dimethylformamide, triethylamine, and acryloyl chloride is 1:15-20:1-1.2:1-1.2; The crosslinking agent is polyethylene glycol diacrylate; The molecular weight of the polyethylene glycol diacrylate is 400-600; The photoinitiator is 2-hydroxy-2-methylpropiophenone; The mass ratio of the pretreated carbazole-based material, crosslinking agent, photoinitiator, and acetonitrile is 10:1-1.5:0.1-0.12:40-60; The mass ratio of the water phase to the oil phase in the oil-in-water emulsion is 3:0.8-1.2; The light irradiation power density is 10-20 mW / cm 2 ; The dispersant is one of polyvinyl alcohol or sodium dodecyl sulfate; The concentration of the dispersant in the water phase is 0.5-1 wt%; The temperature of the vacuum drying is 58-62 °C, and the drying time is 20-24 h.

[0007] The method of the chlorination reaction is as follows: the continuous chlorination of p-chlorotoluene is achieved by connecting four towers, namely Tower 1, Tower 2, Tower 3, and Tower 4, in series. The raw material p-chlorotoluene is added to Tower 1, and no materials are added to Tower 2, Tower 3, and Tower 4. Tower 1 is heated to 89 - 91 °C, and the ultraviolet lamp in Tower 1 is turned on. Then, chlorine gas is introduced into Tower 1. After the reaction in Tower 1 for 4 - 5 hours, the p-chlorotoluene raw material pump in Tower 1 is turned on, and the overflow liquid from Tower 1 is introduced into Tower 2. Tower 2 is heated to 99 - 101 °C, the ultraviolet lamp in Tower 2 is turned on, and chlorine gas is introduced into Tower 2. The overflow liquid from Tower 2 is introduced into Tower 3. Tower 3 is heated to 104 - 106 °C, the ultraviolet lamp in Tower 3 is turned on, and chlorine gas is introduced into Tower 3. The overflow liquid from Tower 3 is introduced into Tower 4. The temperature of Tower 4 is controlled at 55 - 60 °C. The tert-butyldiphenylsilyl mercaptan is atomized into liquid droplets with a size of 5 - 10 μm by an ultrasonic atomizing nozzle and added to Tower 4, where it contacts the rising chlorine gas in a countercurrent manner. A rotating disk distributor is installed at the 1 / 3 height of Tower 4, and the rotation speed of the rotating disk distributor is controlled at 200 - 300 rpm. The carbazolyl copolymer microspheres are evenly sprayed using the rotating disk distributor. The ultraviolet lamp in Tower 4 is turned on, and chlorine gas is introduced into Tower 4. The residual chlorine in Tower 4 is sent to Tower 1. When Tower 4 is full, the crude product flowing out of Tower 4 is intercepted by the microspheres through an ultrafiltration membrane, and then the tert-butyldiphenylsilyl mercaptan is extracted with an extractant. After stratification, the organic phase is dried over anhydrous sodium sulfate or molecular sieve to remove trace moisture, and p-chlorobenzotrichloride is obtained. The tert-butyldiphenylsilyl mercaptan is precipitated by acidification from the alkaline aqueous phase after extraction, and after separation and drying, it is returned to Tower 4 for reuse. The generated hydrochloric acid and residual chlorine gas are absorbed by a tail gas treatment device. The addition amount of the raw material p-chlorotoluene in Tower 1 is added to a position 4 - 6 cm below the overflow port of the tower. The main wavelengths of the ultraviolet lamps in Tower 1, Tower 2, and Tower 3 are the same, and the main wavelength is 365 nm. The light source power density of Tower 1 is 20 - 25 mW / cm 2 ; The light source power density of Tower 2 is 25 - 30 mW / cm 2 ; The light source power density of Tower 3 is 30 - 35 mW / cm 2 ; The main wavelength of the ultraviolet lamp in Tower 4 is 400 nm, and the light source power density is 15 - 20 mW / cm 2 ; The flow rate of the p-chlorotoluene raw material pump in Tower 1 is set at 400 - 450 g / h. The flow rate of chlorine gas in Tower 1 is 60 - 70 L / h. The flow rate of chlorine gas in Tower 2 is 80 - 90 L / h. The flow rate of chlorine gas in the 3# tower is 100 - 110 L / h; The flow rate of chlorine gas in the 4# tower is 130 - 140 L / h; The addition amount of tert-butyl diphenylsilyl mercaptan in the 4# tower is 25 - 30 g / h; The addition amount of carbazolyl copolymer microspheres in the 4# tower is 95 - 105 g / h; The pore size of the ultrafiltration membrane is 5 - 10 μm; The extractant is an aqueous sodium hydroxide solution with a concentration of 4 - 6 wt%; The mass ratio of the extractant to the organic phase is 1:2.5 - 3.5.

[0008] The method of the fluorination reaction is as follows: Mix p-chlorobenzotrichloride and trifluoromethanesulfonic acid obtained from the chlorination reaction step and introduce them into the 5# tower. Control the feeding flow rate of p-chlorobenzotrichloride to be 650 - 750 g / h. Open the tail gas cooling system, heat the 5# tower to 58 - 62 °C, and control the pressure to be 1.1 - 1.3 MPa. After the 5# tower starts to overflow, introduce hydrogen fluoride into the 5# tower. The overflow liquid of the 5# tower is introduced into the 6# tower, and then antimony pentafluoride is introduced. Heat the 6# tower to 88 - 92 °C, control the pressure to be 1.4 - 1.6 MPa, introduce hydrogen fluoride into the 6# tower, and introduce the hydrogen fluoride recovered by condensation in the 6# tower into the 5# tower. After the reaction in the 6# tower, a crude product of p-chlorobenzotrifluoride is obtained; The mass ratio of p-chlorobenzotrichloride to trifluoromethanesulfonic acid is 2350 - 2450:1; The feeding amount of hydrogen fluoride in the 5# tower is 100 - 120 g / h; The addition amount of antimony pentafluoride is 0.18 - 0.22 g / h; The feeding amount of hydrogen fluoride in the 6# tower is 110 - 130 g / h.

[0009] The method of rectification is as follows: Subject the crude product of p-chlorobenzotrifluoride to vacuum rectification under the conditions of a vacuum degree of 0.03 - 0.04 Mpa and a reflux ratio of 4 - 6:1, and collect the fraction with a top gas temperature of 110 - 120 °C. After condensation, a p-chlorobenzotrifluoride product is obtained; The vacuum degree of the vacuum is 0.03 - 0.04 Mpa.

[0010] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention adopts a four-tower series continuous chlorination reaction system. The ultraviolet light power and temperature of each reaction tower are independently controlled, and the chlorination reaction is strengthened in stages to enable efficient reactions in the early, middle, and late stages. The first tower focuses on monochlorination, the second tower deepens dichlorination, and the third and fourth towers achieve efficient conversion of polychlorinated products, shortening the reaction time. It reduces the generation of side reaction impurities and at the same time reduces energy consumption, which is beneficial to improving the yield and purity of the target product. It is easier to control the temperature rise during the reaction process and further improves the safety of the reaction process.

[0011] (2) In the preparation method of the carbazole-based copolymer microspheres of the present invention, 2,4,5,6-tetra(9-carbazolyl) isophthalonitrile reacts with acryloyl chloride to introduce acrylate groups; in the oil-in-water emulsion under light irradiation, the photoinitiator therein decomposes to generate free radicals, which initiate the free radical polymerization reaction of the acrylate groups in the pretreated carbazole-based material and the crosslinking agent. Through this crosslinking reaction, each molecule is interconnected and gradually forms microspheres. The oil-in-water emulsion system plays a role in restricting the reaction space, enabling the crosslinking reaction to occur inside the emulsion droplets, thereby controlling the size and morphology of the microspheres. By adjusting the stirring speed, the size of the droplets can be controlled, and thus the size of the final microspheres can be affected. After the crosslinking is completed, the unreacted monomers and dispersants are removed by centrifugation and washing, and finally the carbazole-based copolymer microspheres are obtained by vacuum drying.

[0012] (3) In the continuous tower chlorination reaction, the temperature is gradually increased in the first three towers to promote step-by-step chlorination, and the temperature is appropriately decreased in the fourth tower to inhibit over-chlorination. At the 4# tower, a long wavelength of 400 nm is used to reduce the chlorine cracking energy and form low-energy chlorine free radicals. At the same time, the carbazole-based copolymer microspheres and tert-butyl diphenylsilyl mercaptan are added to the 4# tower in the present invention. The carbazole-based copolymer microspheres are crosslinked by 2,4,5,6-tetra(9-carbazolyl) isophthalonitrile and polyethylene glycol diacrylate. The carbazole group has photosensitivity. After being photoexcited, two chlorine free radicals can be generated by chlorine through energy transfer. The microspheres have a high specific surface area and can promote the adsorption of chlorine. The flexibility of the polyethylene glycol chain segment of the microspheres promotes the diffusion of chlorine molecules to the active sites and improves the catalytic efficiency. The catalytic reaction of the carbazole-based copolymer microspheres with chlorine plays a synergistic role with the direct photo-initiation of chlorine to generate chlorine free radicals, increasing the concentration of chlorine free radicals in the tower; The strong electron-donating property of the carbazole group of the carbazole-based copolymer microspheres improves the electron-deficiency of the benzene ring methyl group through conjugation, making the chlorine free radicals more likely to attack the methyl group rather than the electron-rich benzene ring, playing a role in stabilizing the para-reaction intermediate and promoting regioselective chlorination, and reducing the by-products of benzene ring chlorination; After tert-butyl diphenylsilyl mercaptan contacts with the monochlorinated product or dichlorinated product of p-chlorotoluene in the tower, the large volume of the tert-butyl and diphenylsilyl groups prevents the direct attack of chlorine free radicals on the benzene ring through steric shielding, ensuring that the chlorination reaction occurs specifically at the methyl site. At the same time, tert-butyl diphenylsilyl mercaptan can capture excessive chlorine free radicals to avoid the generation of by-products other than p-chlorobenzotrichloride due to over-chlorination;

[0013] The π-π stacking of the carbazole groups of 2,4,5,6-tetra(9-carbazolyl) isophthalonitrile enriches the chlorine free radicals in the benzyl region through the π-stacking effect. The steric hindrance of the silyl group of tert-butyl diphenylsilyl mercaptan and the π-stacking effect protect the benzene ring doubly, which can effectively reduce the generation of by-products.

[0014] (4) Compared with the traditional process, the fluorination reaction in this synthesis method adopts continuous tower fluorination technology. By adjusting the ratio and feeding rate of anhydrous hydrogen fluoride, p-chlorobenzotrichloride, and the catalyst, and optimizing the reaction process, hydrogen fluoride can participate in the reaction more effectively, improving the utilization rate of hydrogen fluoride. The production process is safe, with controllable temperature and pressure, and the comprehensive cost is reduced.

[0015] In the fluorination reaction, adjust the addition process of the two catalysts. Add trifluoromethanesulfonic acid to Tower No. 5 to provide an acidic environment, which can protonate HF to H2F + (fluoronium ion), greatly enhancing its electrophilicity. Secondly, trifluoromethanesulfonic acid polarizes the C-Cl bond by forming hydrogen bonds or coordination with the substrate, making it more easily substituted by F - substitution, promoting the chlorine-fluorine exchange reaction; furthermore, the strong acidity of trifluoromethanesulfonic acid can inhibit the self-polymerization of HF to form (HF) n , reducing side reactions such as over-fluorination or aromatic ring fluorination caused by polymers, and avoiding its decomposition or other side reactions through protonated intermediates; trifluoromethanesulfonic acid enhances the electron cloud density or electron cloud distribution of the substrate molecule, optimizing the reaction conditions, and can reduce the pressure and temperature during the reaction process; add antimony pentafluoride to Tower No. 6. The high electronegativity of fluorine atoms directionally affects the active sites of the substrate, forming a stable intermediate to reduce the activation energy of the reaction, making it more easily combine with the raw materials, reducing the difficulty of the fluorination reaction, and improving the reaction rate and efficiency.

[0016] (5) The purity of p-chlorobenzotrifluoride prepared by the method of the present invention is 99.61 - 99.72%, the two-step yield is 96.48 - 96.65%, the yield of the chlorination reaction step is 98.41 - 98.77%, the chlorine consumption is 1.60 - 1.64 times of the theoretical value, and the purity of the intermediate p-chlorobenzotrichloride is 98.47 - 98.52%. Specific Embodiments

[0017] In order to have a clearer understanding of the technical features, objectives, and effects of the present invention, the specific embodiments of the present invention are now described.

[0018] Example 1 A preparation method of p-chlorobenzotrifluoride Comprising the following steps (1) Preparation of carbazolyl copolymer microspheres The preparation method of the carbazolyl copolymer microspheres is as follows: dissolve 2,4,5,6-tetra(9-carbazolyl)isophthalonitrile in N,N-dimethylformamide, add triethylamine as an acid-binding agent, dropwise add acryloyl chloride under ice bath, stir at room temperature for 12 hours. After the reaction is completed, precipitate and purify with ether, and dry to obtain the pretreated carbazolyl material; add the pretreated carbazolyl material, crosslinking agent and photoinitiator into acetonitrile, stir evenly, ultrasonically disperse for 12 min to form a uniform oil phase, drop the oil phase into the water phase containing a dispersant, stir at 7000 rpm for 12 min to form a stable oil-in-water emulsion, then adjust the stirring speed to 1000 rpm to control the droplet size, control the system temperature at 30 °C, irradiate with light of 365 nm wavelength for 25 min to initiate the crosslinking of acrylate groups in the ionic liquid. After the crosslinking is completed, centrifuge at 4000 rpm for 12 min, collect the microsphere product, wash it alternately with water and ethanol twice to remove unreacted monomers and dispersants, and vacuum dry to obtain the carbazolyl copolymer microspheres; The mass ratio of 2,4,5,6-tetra(9-carbazolyl)isophthalonitrile, N,N-dimethylformamide, triethylamine, and acryloyl chloride is 1:18:1.1:1.1; The crosslinking agent is polyethylene glycol diacrylate; The molecular weight of the polyethylene glycol diacrylate is 500; The photoinitiator is 2-hydroxy-2-methylpropiophenone; The mass ratio of the pretreated carbazolyl material, crosslinking agent, photoinitiator, and acetonitrile is 10:1.2:0.11:50; The mass ratio of the water phase to the oil phase in the oil-in-water emulsion is 3:1; The light irradiation power density is 15 mW / cm 2 ; The dispersant is polyvinyl alcohol; The concentration of the dispersant in the water phase is 0.5 wt%; The temperature of the vacuum drying is 60 °C, and the drying time is 22 h.

[0019] (2) Chlorination reaction Four towers numbered 1#, 2#, 3#, and 4# are connected in series in sequence to achieve the continuous chlorination of p-chlorotoluene. 1000 g of the raw material p-chlorotoluene is added to Tower 1#. The raw material is added 5 cm below the overflow port of Tower 1#. No raw material is added to Towers 2#, 3#, and 4#. Tower 1# is heated to 90 °C, and the ultraviolet lamp in Tower 1# is turned on. Then, chlorine gas is introduced into Tower 1#. After reacting in Tower 1# for 4.5 h, the p-chlorotoluene raw material pump in Tower 1# is turned on, and the overflow liquid from Tower 1# is introduced into Tower 2#. Tower 2# is heated to 100 °C, and the ultraviolet lamp in Tower 2# is turned on. Then, chlorine gas is introduced into Tower 2#. The overflow liquid from Tower 2# is introduced into Tower 3#. Tower 3# is heated to 105 °C, and the ultraviolet lamp in Tower 3# is turned on. Then, chlorine gas is introduced into Tower 3#. The overflow liquid from Tower 3# is introduced into Tower 4#. The temperature of Tower 4# is controlled at 58 °C. The tert-butyldiphenylsilyl mercaptan is atomized into 8-μm droplets by an ultrasonic atomizing nozzle and added to Tower 4#, where it contacts the rising chlorine gas in a countercurrent manner. A rotary disk distributor is installed at the 1 / 3 height of Tower 4#, and the rotation speed of the rotary disk distributor is controlled at 250 rpm. The carbazolyl copolymer microspheres are evenly sprayed using the rotary disk distributor. The ultraviolet lamp in Tower 4# is turned on, and then chlorine gas is introduced into Tower 4#. The residual chlorine in Tower 4# is sent to Tower 1#. When Tower 4# is full, the crude product flowing out of Tower 4# intercepts the microspheres through an ultrafiltration membrane, and then the tert-butyldiphenylsilyl mercaptan is extracted with an extractant. After layering, the organic phase is dried over anhydrous sodium sulfate to remove trace moisture to obtain p-chlorotrichlorotoluene; The basic aqueous phase and aqueous phase after extraction precipitate tert-butyldiphenylsilyl mercaptan through acidification, and after separation and drying, they are returned to Tower 4# for reuse; The generated hydrochloric acid and residual chlorine gas are absorbed by a tail gas treatment device; The main wavelengths of the ultraviolet lamps in Towers 1#, 2#, and 3# are the same, and the main wavelength is 365 nm; The light source power density of Tower 1# is 22 mW / cm 2 ; The light source power density of Tower 2# is 28 mW / cm 2 ; The light source power density of Tower 3# is 32 mW / cm 2 ; The main wavelength of the ultraviolet lamp in Tower 4# is 400 nm, and the light source power density is 18 mW / cm 2 ; The flow rate of the p-chlorotoluene raw material pump in Tower 1# is set at 420 g / h; The flow rate of chlorine gas in Tower 1# is 65 L / h; The flow rate of chlorine gas in Tower 2# is 85 L / h; The flow rate of chlorine gas in Tower 3# is 105 L / h; The flow rate of chlorine gas in Tower 4# is 135 L / h; The addition amount of tert-butyldiphenylsilyl mercaptan in Tower 4# is 28 g / h; The addition amount of the carbazolyl copolymer microspheres in the 4# tower is 100 g / h; The pore size of the ultrafiltration membrane is 8 μm; The extractant is a 5 wt% aqueous sodium hydroxide solution; The mass ratio of the extractant to the organic phase is 1:3.

[0020] After the 1# tower, 2# tower, 3# tower and 4# tower operate stably, 7535 g of p-chlorobenzotrichloride is obtained in 10 h, the yield is 98.77%, the chlorine consumption is 1.61 times the theoretical value, and the purity of the sampled p-chlorobenzotrichloride is 98.52%.

[0021] (3) Fluorination reaction Mix p-chlorobenzotrichloride obtained in the chlorination reaction step and trifluoromethanesulfonic acid in a mass ratio of 2400:1 and feed them into the 5# tower. Control the feeding flow rate of p-chlorobenzotrichloride at 700 g / h. Open the tail gas cooling system, heat up the 5# tower to 60 °C, and control the pressure at 1.2 MPa. After the 5# tower starts to overflow, feed hydrogen fluoride into the 5# tower, and the feeding amount of hydrogen fluoride is 110 g / h. The overflow liquid of the 5# tower is fed into the 6# tower, and then antimony pentafluoride is fed in. The addition amount of antimony pentafluoride is 0.20 g / h. Heat up the 6# tower to 90 °C, control the pressure at 1.5 MPa, feed hydrogen fluoride into the 6# tower, and the feeding amount of hydrogen fluoride is 120 g / h. The hydrogen fluoride recovered by condensation from the 6# tower is fed into the 5# tower, and a crude product of p-chlorobenzotrifluoride is obtained after the reaction in the 6# tower.

[0022] (4) Rectification Carry out vacuum rectification on the crude p-chlorobenzotrifluoride under the conditions of vacuum and a reflux ratio of 5:1, collect the fraction with a top gas temperature of 110 - 120 °C, and obtain the p-chlorobenzotrifluoride product after condensation; The vacuum degree of the vacuum is 0.035 Mpa.

[0023] The purity of the p-chlorobenzotrifluoride product is 99.72%, and the total two-step yield is 96.65%.

[0024] Example 2 A preparation method of p-chlorobenzotrifluoride Comprising the following steps (1) Preparation of carbazolyl copolymer microspheres The preparation method of the carbazolyl copolymer microspheres is as follows: Dissolve 2,4,5,6-tetra(9-carbazolyl) isophthalonitrile in N,N-dimethylformamide, add triethylamine as an acid-binding agent, dropwise add acryloyl chloride under ice bath, stir at room temperature for 10 hours. After the reaction is completed, precipitate and purify with ether, and dry to obtain the pretreated carbazolyl material; Add the pretreated carbazolyl material, crosslinking agent and photoinitiator to acetonitrile, stir evenly, ultrasonically disperse for 10 min to form a uniform oil phase. Drop the oil phase into the water phase containing a dispersant, stir at 6000 rpm for 15 min to form a stable oil-in-water emulsion, then adjust the stirring speed to 800 rpm to control the droplet size, control the system temperature at 25 °C, irradiate with light of 365 nm wavelength for 20 min to initiate the crosslinking of acrylate groups in the ionic liquid. After the crosslinking is completed, centrifuge at 3000 rpm for 15 min, collect the microsphere product, wash it alternately with water and ethanol twice to remove unreacted monomers and dispersants, and vacuum dry to obtain the carbazolyl copolymer microspheres; The mass ratio of 2,4,5,6-tetra(9-carbazolyl) isophthalonitrile, N,N-dimethylformamide, triethylamine, and acryloyl chloride is 1:15:1:1; The crosslinking agent is polyethylene glycol diacrylate; The molecular weight of the polyethylene glycol diacrylate is 400; The photoinitiator is 2-hydroxy-2-methylpropiophenone; The mass ratio of the pretreated carbazolyl material, crosslinking agent, photoinitiator, and acetonitrile is 10:1:0.1:40; The mass ratio of the water phase to the oil phase in the oil-in-water emulsion is 3:0.8; The light irradiation power density is 10 mW / cm 2 ; The dispersant is polyvinyl alcohol; The concentration of the dispersant in the water phase is 0.7 wt%; The temperature of the vacuum drying is 58 °C, and the drying time is 24 h.

[0025] (2) Chlorination reaction Four towers numbered 1#, 2#, 3#, and 4# are connected in series in sequence to achieve the continuous chlorination of p-chlorotoluene. 1000 g of the raw material p-chlorotoluene is added to tower 1#. The raw material is added 4 cm below the overflow port of tower 1#. Towers 2#, 3#, and 4# are not fed. Tower 1# is heated to 89 °C, the ultraviolet lamp of tower 1# is turned on, and chlorine gas is started to be introduced into tower 1#. After the reaction in tower 1# for 5 h, the p-chlorotoluene raw material pump of tower 1# is turned on, and the overflow liquid of tower 1# is introduced into tower 2#. Tower 2# is heated to 99 °C, the ultraviolet lamp of tower 2# is turned on, and chlorine gas is started to be introduced into tower 2#. The overflow liquid of tower 2# is introduced into tower 3#. Tower 3# is heated to 104 °C, the ultraviolet lamp of tower 3# is turned on, and chlorine gas is started to be introduced into tower 3#. The overflow liquid of tower 3# is introduced into tower 4#. The temperature of tower 4# is controlled at 55 °C. The tert-butyl diphenylsilyl mercaptan is atomized into 5-μm droplets by an ultrasonic atomizing nozzle and added to tower 4#, where it contacts the rising chlorine gas in a countercurrent manner. A rotating disk distributor is set at the 1 / 3 height of tower 4#, and the rotation speed of the rotating disk distributor is controlled at 200 rpm. The carbazolyl copolymer microspheres are evenly sprayed using the rotating disk distributor. The ultraviolet lamp of tower 4# is turned on, and chlorine gas is started to be introduced into tower 4#. The residual chlorine in tower 4# is led to tower 1#. When tower 4# is full, the crude product flowing out of tower 4# intercepts the microspheres through an ultrafiltration membrane, and then the tert-butyl diphenylsilyl mercaptan is extracted with an extractant. After stratification, the organic phase is dried over anhydrous sodium sulfate to remove trace moisture to obtain p-chlorotrichlorotoluene; The alkaline phase and aqueous phase after extraction precipitate tert-butyl diphenylsilyl mercaptan through acidification, and after separation and drying, they are returned to tower 4# for reuse; The generated hydrochloric acid and residual chlorine gas are absorbed by a tail gas treatment device; The main wavelengths of the ultraviolet lamps of tower 1#, tower 2#, and tower 3# are the same, and the main wavelength is 365 nm; The light source power density of tower 1# is 20 mW / cm 2 ; The light source power density of tower 2# is 25 mW / cm 2 ; The light source power density of tower 3# is 30 mW / cm 2 ; The main wavelength of the ultraviolet lamp of tower 4# is 400 nm, and the light source power density is 10 mW / cm 2 ; The flow rate of the p-chlorotoluene raw material pump in tower 1# is set at 400 g / h; The flow rate of chlorine gas in tower 1# is 60 L / h; The flow rate of chlorine gas in tower 2# is 80 L / h; The flow rate of chlorine gas in tower 3# is 100 L / h; The flow rate of chlorine gas in tower 4# is 130 L / h; The addition amount of tert-butyl diphenylsilyl mercaptan in tower 4# is 25 g / h; The addition amount of the carbazolyl copolymer microspheres in the 4# tower is 95 g / h; The pore size of the ultrafiltration membrane is 5 μm; The extractant is an aqueous sodium hydroxide solution with a concentration of 4 wt%; The mass ratio of the extractant to the organic phase is 1:2.5.

[0026] After the 1# tower, 2# tower, 3# tower and 4# tower operate stably, 7150 g of p-chlorobenzotrichloride is obtained in 10 h, the yield is 98.41%, the chlorine consumption is 1.60 times of the theoretical value, and the purity of the sampled p-chlorobenzotrichloride is detected to be 98.50%.

[0027] (3) Fluorination reaction Mix p-chlorobenzotrichloride obtained in the chlorination reaction step and trifluoromethanesulfonic acid in a mass ratio of 2350:1 and feed them into the 5# tower. Control the feeding flow rate of p-chlorobenzotrichloride to be 650 g / h. Open the tail gas cooling system, heat the 5# tower to 58 °C, and control the pressure to be 1.1 MPa. After the 5# tower starts to overflow, feed hydrogen fluoride into the 5# tower, and the feeding amount of hydrogen fluoride is 100 g / h. The overflow liquid of the 5# tower is fed into the 6# tower, and then antimony pentafluoride is fed in. The addition amount of antimony pentafluoride is 0.18 g / h. Heat the 6# tower to 88 °C, control the pressure to be 1.4 MPa, feed hydrogen fluoride into the 6# tower, and the feeding amount of hydrogen fluoride is 110 g / h. The hydrogen fluoride recovered by condensation from the 6# tower is fed into the 5# tower, and a crude product of p-chlorobenzotrifluoride is obtained after the reaction in the 6# tower.

[0028] (4) Rectification Carry out vacuum rectification on the crude product of p-chlorobenzotrifluoride under the conditions of vacuum and a reflux ratio of 4:1, collect the fraction with a top gas temperature of 110 - 120 °C, and obtain the p-chlorobenzotrifluoride product after condensation; The vacuum degree of the vacuum is 0.03 Mpa.

[0029] The purity of the p-chlorobenzotrifluoride product is 99.68%, and the total two-step yield is 96.48%.

[0030] Example 3 A preparation method of p-chlorobenzotrifluoride Comprising the following steps (1) Preparation of carbazolyl copolymer microspheres The preparation method of the carbazolyl copolymer microspheres is as follows: dissolve 2,4,5,6-tetra(9-carbazolyl) isophthalonitrile in N,N-dimethylformamide, add triethylamine as an acid-binding agent, dropwise add acryloyl chloride under an ice bath, stir at room temperature for 14 hours. After the reaction is completed, precipitate and purify with ether, and dry to obtain a pretreated carbazolyl material; add the pretreated carbazolyl material, a crosslinking agent and a photoinitiator to acetonitrile, stir evenly, ultrasonically disperse for 15 min to form a uniform oil phase. Drop the oil phase into the water phase containing a dispersant, stir at 8000 rpm for 10 min to form a stable oil-in-water emulsion, then adjust the stirring speed to 1200 rpm to control the droplet size, control the system temperature at 35 °C, irradiate with light at a wavelength of 365 nm for 30 min to initiate the crosslinking of acrylate groups in the ionic liquid. After the crosslinking is completed, centrifuge at 5000 rpm for 10 min, collect the microsphere product, wash it alternately with water and ethanol 3 times to remove unreacted monomers and dispersants, and vacuum dry to obtain carbazolyl copolymer microspheres; The mass ratio of 2,4,5,6-tetra(9-carbazolyl) isophthalonitrile, N,N-dimethylformamide, triethylamine, and acryloyl chloride is 1:20:1.2:1.2; The crosslinking agent is polyethylene glycol diacrylate; The molecular weight of the polyethylene glycol diacrylate is 600; The photoinitiator is 2-hydroxy-2-methylpropiophenone; The mass ratio of the pretreated carbazolyl material, the crosslinking agent, the photoinitiator, and acetonitrile is 10:1.5:0.12:60; The mass ratio of the water phase to the oil phase in the oil-in-water emulsion is 3:1.2; The light irradiation power density is 20 mW / cm 2 ; The dispersant is sodium dodecyl sulfate; The concentration of the dispersant in the water phase is 1 wt%; The temperature of the vacuum drying is 62 °C, and the drying time is 20 h.

[0031] (2) Chlorination reaction Four towers numbered 1#, 2#, 3#, and 4# are connected in series in sequence to achieve the continuous chlorination of p-chlorotoluene. 1000 g of the raw material p-chlorotoluene is added to tower 1#. The raw material is added 6 cm below the overflow port of tower 1#. No raw material is added to towers 2#, 3#, and 4#. Tower 1# is heated to 91 °C, and the ultraviolet lamp in tower 1# is turned on. Then, chlorine gas is introduced into tower 1#. After 4 hours of reaction in tower 1#, the p-chlorotoluene raw material pump in tower 1# is turned on, and the overflow liquid from tower 1# is introduced into tower 2#. Tower 2# is heated to 101 °C, and the ultraviolet lamp in tower 2# is turned on. Then, chlorine gas is introduced into tower 2#. The overflow liquid from tower 2# is introduced into tower 3#. Tower 3# is heated to 106 °C, and the ultraviolet lamp in tower 3# is turned on. Then, chlorine gas is introduced into tower 3#. The overflow liquid from tower 3# is introduced into tower 4#. The temperature in tower 4# is controlled at 62 °C. The tert-butyldiphenylsilyl mercaptan is atomized into 10-μm droplets by an ultrasonic atomizing nozzle and added to tower 4#, where it contacts the rising chlorine gas countercurrently. A rotating disk distributor is set at the 1 / 3 height of tower 4#, and the rotation speed of the rotating disk distributor is controlled at 300 rpm. The carbazolyl copolymer microspheres are evenly sprayed using the rotating disk distributor. The ultraviolet lamp in tower 4# is turned on, and then chlorine gas is introduced into tower 4#. The residual chlorine in tower 4# is sent to tower 1#. When tower 4# is full, the crude product flowing out of tower 4# intercepts the microspheres through an ultrafiltration membrane, and then the tert-butyldiphenylsilyl mercaptan is extracted with an extractant. After stratification, the organic phase is dried by a molecular sieve to remove trace moisture to obtain p-chlorotrichlorotoluene; The alkaline aqueous phase after extraction precipitates tert-butyldiphenylsilyl mercaptan through acidification, and after separation and drying, it is returned to tower 4# for reuse; The generated hydrochloric acid and residual chlorine gas are absorbed by a tail gas treatment device; The main wavelengths of the ultraviolet lamps in towers 1#, 2#, and 3# are the same, and the main wavelength is 365 nm; The light source power density of tower 1# is 25 mW / cm 2 ; The light source power density of tower 2# is 30 mW / cm 2 ; The light source power density of tower 3# is 35 mW / cm 2 ; The main wavelength of the ultraviolet lamp in tower 4# is 400 nm, and the light source power density is 20 mW / cm 2 ; The flow rate of the p-chlorotoluene raw material pump in tower 1# is set at 450 g / h; The flow rate of chlorine gas in tower 1# is 70 L / h; The flow rate of chlorine gas in tower 2# is 90 L / h; The flow rate of chlorine gas in tower 3# is 110 L / h; The flow rate of chlorine gas in tower 4# is 140 L / h; The addition amount of tert-butyldiphenylsilyl mercaptan in tower 4# is 30 g / h; The addition amount of the carbazolyl copolymer microspheres in the 4# tower is 105 g / h; The pore size of the ultrafiltration membrane is 10 μm; The extractant is 6 wt% aqueous sodium hydroxide solution; The mass ratio of the extractant to the organic phase is 1:3.5.

[0032] After the 1# tower, 2# tower, 3# tower and 4# tower operate stably, 8059 g of p-chlorobenzotrichloride is obtained in 10 h, the yield is 98.60%, the chlorine consumption is 1.64 times of the theoretical value, and the purity of the sampled p-chlorobenzotrichloride is detected to be 98.47%.

[0033] (3) Fluorination reaction Mix p-chlorobenzotrichloride obtained in the chlorination reaction step and trifluoromethanesulfonic acid in a mass ratio of 2450:1 and introduce them into the 5# tower. Control the feeding flow rate of p-chlorobenzotrichloride to be 750 g / h. Open the tail gas cooling system, heat the 5# tower to 62 °C, and control the pressure to be 1.3 MPa. After the 5# tower starts to overflow, introduce hydrogen fluoride into the 5# tower, and the feeding amount of hydrogen fluoride is 120 g / h. The overflow liquid of the 5# tower is introduced into the 6# tower, and then antimony pentafluoride is introduced. The addition amount of antimony pentafluoride is 0.22 g / h. Heat the 6# tower to 92 °C, control the pressure to be 1.6 MPa, introduce hydrogen fluoride into the 6# tower, and the feeding amount of hydrogen fluoride is 130 g / h. The hydrogen fluoride recovered by condensation from the 6# tower is introduced into the 5# tower, and a crude product of p-chlorobenzotrifluoride is obtained after the reaction in the 6# tower.

[0034] (4) Rectification Rectify the crude product of p-chlorobenzotrifluoride under vacuum with a reflux ratio of 6:1, collect the fraction with a top gas phase temperature of 110 - 120 °C, and obtain the p-chlorobenzotrifluoride product after condensation; The vacuum degree of the vacuum is 0.04 Mpa.

[0035] The purity of the p-chlorobenzotrifluoride product is 99.61%, and the total two-step yield is 96.52%.

[0036] Example 4 A preparation method of p-chlorobenzotrifluoride Comprising the following steps (1) Chlorination reaction Four towers numbered 1#, 2#, 3#, and 4# are connected in series in sequence to achieve the continuous chlorination of p-chlorotoluene. 1000 g of the raw material p-chlorotoluene is added to Tower 1#, and the raw material is added 5 cm below the overflow port of Tower 1#. No raw materials are added to Towers 2#, 3#, and 4#. Tower 1# is heated to 90 °C, the ultraviolet lamp in Tower 1# is turned on, and chlorine gas is started to be introduced into Tower 1#. After reacting in Tower 1# for 4.5 h, the p-chlorotoluene raw material pump in Tower 1# is turned on, and the overflow liquid from Tower 1# is introduced into Tower 2#. Tower 2# is heated to 100 °C, the ultraviolet lamp in Tower 2# is turned on, and chlorine gas is started to be introduced into Tower 2#. The overflow liquid from Tower 2# is introduced into Tower 3#. Tower 3# is heated to 105 °C, the ultraviolet lamp in Tower 3# is turned on, and chlorine gas is started to be introduced into Tower 3#. The overflow liquid from Tower 3# is introduced into Tower 4#. The temperature of Tower 4# is controlled at 110 °C, the ultraviolet lamp in Tower 4# is turned on, and chlorine gas is started to be introduced into Tower 4#. The residual chlorine in Tower 4# is led to Tower 1# to keep the dynamic balance between the feed of Tower 1# and the discharge of Tower 4#. When Tower 4# is full, the product flowing out of Tower 4# is dried with anhydrous sodium sulfate to remove trace moisture to obtain p-chlorobenzotrichloride; The generated hydrochloric acid and residual chlorine gas are absorbed by the tail gas treatment device; The main wavelengths of the ultraviolet lamps in Tower 1#, Tower 2#, Tower 3#, and Tower 4# are the same, and the main wavelength is 365 nm; The light source power density of Tower 1# is 22 mW / cm 2 ; The light source power density of Tower 2# is 28 mW / cm 2 ; The light source power density of Tower 3# is 32 mW / cm 2 ; The light source power density of Tower 4# is 38 mW / cm 2 ; The flow rate of the p-chlorotoluene raw material pump in Tower 1# is set to 420 g / h; The flow rate of chlorine gas in Tower 1# is 65 L / h; The flow rate of chlorine gas in Tower 2# is 85 L / h; The flow rate of chlorine gas in Tower 3# is 105 L / h; The flow rate of chlorine gas in Tower 4# is 135 L / h.

[0037] After the stable operation of Towers 1#, 2#, 3#, and 4#, 7266 g of p-chlorobenzotrichloride is obtained in 10 h, the yield is 95.24%, the consumption of chlorine gas is 1.71 times the theoretical value, and the purity of the sampled p-chlorobenzotrichloride is detected to be 93.16%.

[0038] (2) Fluorination reaction Mix the p-chlorobenzotrichloride obtained in the chlorination reaction step and trifluoromethanesulfonic acid in a mass ratio of 2400:1 and feed them into Tower No. 5. Control the feeding flow rate of p-chlorobenzotrichloride at 700 g / h. Turn on the tail gas cooling system, heat up Tower No. 5 to 60 °C, and control the pressure at 1.2 MPa. After Tower No. 5 starts to overflow, feed hydrogen fluoride into Tower No. 5, with the feeding amount of hydrogen fluoride being 110 g / h. The overflow liquid of Tower No. 5 is fed into Tower No. 6, and then antimony pentafluoride is fed in, with the addition amount of antimony pentafluoride being 0.20 g / h. Heat up Tower No. 6 to 90 °C, control the pressure at 1.5 MPa, feed hydrogen fluoride into Tower No. 6, with the feeding amount of hydrogen fluoride being 120 g / h. The hydrogen fluoride recovered by condensation from Tower No. 6 is fed into Tower No. 5, and the crude p-chlorobenzotrifluoride is obtained after the reaction in Tower No. 6.

[0039] (3)Rectification Carry out vacuum rectification on the crude p-chlorobenzotrifluoride under the conditions of vacuum and a reflux ratio of 5:1, collect the fractions with the overhead gas temperature of 110 - 120 °C, and obtain the p-chlorobenzotrifluoride product after condensation; The vacuum degree of the said vacuum is 0.035 Mpa.

[0040] The purity of the p-chlorobenzotrifluoride product is 98.27%, and the total two-step yield is 92.33%.

[0041] Compared with Example 1, in the four-tower series continuous chlorination reaction system of Example 4, the temperature of Tower No. 4 is 110 °C, and the light source power density is 38 mW / cm 2 , and tert-butyl diphenylsilyl mercaptan and carbazolyl copolymer microspheres are not added.

[0042] As the degree of chlorination increases, the electron cloud density on the benzene ring gradually decreases, resulting in a gradual decrease in the reactivity of the subsequent chlorination reaction. In the trichlorination stage, to make the reaction continue, higher energy is required to overcome the activation energy of the reaction. This requires more stringent reaction conditions, thereby increasing the possibility of side reactions occurring. Overchlorination may occur, generating tetrachlorinated or higher chlorinated products, or side reactions such as the ring opening of the benzene ring may occur.

[0043] In order to make the chlorination reaction continue in Tower No. 4, a higher temperature and light source power density are set, but at the same time, it also causes a decrease in the purity of the obtained p-chlorobenzotrichloride, a higher content of by-products, with a purity of 93.16%, an increase in the consumption of chlorine, and a decrease in the yield of the intermediate p-chlorotrichloride and the yield of the final product p-chlorobenzotrifluoride.

[0044] Example 5 A preparation method of p-chlorobenzotrifluoride Comprising the following steps (1)Preparation of carbazolyl copolymer microspheres The preparation method of the carbazolyl copolymer microspheres is as follows: Dissolve 2,4,5,6-tetra(9-carbazolyl) isophthalonitrile in N,N-dimethylformamide, add triethylamine as an acid-binding agent, dropwise add acryloyl chloride under ice bath, stir at room temperature for 12 hours. After the reaction is completed, precipitate and purify with ether, and dry to obtain the pretreated carbazolyl material; Add the pretreated carbazolyl material, crosslinking agent and photoinitiator to acetonitrile, stir evenly, ultrasonically disperse for 12 min to form a uniform oil phase. Drop the oil phase into the water phase containing a dispersant, stir at 7000 rpm for 12 min to form a stable oil-in-water emulsion, then adjust the stirring speed to 1000 rpm to control the droplet size, control the system temperature at 30 °C, irradiate with light of 365 nm wavelength for 25 min to initiate the crosslinking of acrylate groups in the ionic liquid. After the crosslinking is completed, centrifuge at 4000 rpm for 12 min, collect the microsphere product, wash it alternately with water and ethanol twice to remove unreacted monomers and dispersants, and obtain the carbazolyl copolymer microspheres after vacuum drying; The mass ratio of 2,4,5,6-tetra(9-carbazolyl) isophthalonitrile, N,N-dimethylformamide, triethylamine, and acryloyl chloride is 1:18:1.1:1.1; The crosslinking agent is polyethylene glycol diacrylate; The molecular weight of the polyethylene glycol diacrylate is 500; The photoinitiator is 2-hydroxy-2-methylpropiophenone; The mass ratio of the pretreated carbazolyl material, crosslinking agent, photoinitiator, and acetonitrile is 10:1.2:0.11:50; The mass ratio of the water phase to the oil phase in the oil-in-water emulsion is 3:1; The light irradiation power density is 15 mW / cm 2 ; The dispersant is polyvinyl alcohol; The concentration of the dispersant in the water phase is 0.5 wt%; The temperature of the vacuum drying is 60 °C, and the drying time is 22 h.

[0045] (2) Chlorination reaction Four towers numbered 1#, 2#, 3#, and 4# are connected in series in sequence to achieve the continuous chlorination of p-chlorotoluene. 1000 g of the raw material p-chlorotoluene is added to Tower 1#. The raw material is added 5 cm below the overflow port of Tower 1#. No raw material is added to Towers 2#, 3#, and 4#. Tower 1# is heated to 90 °C, and the ultraviolet lamp in Tower 1# is turned on. Then, chlorine gas is introduced into Tower 1#. After reacting in Tower 1# for 4.5 h, the p-chlorotoluene raw material pump in Tower 1# is turned on, and the overflow liquid from Tower 1# is introduced into Tower 2#. Tower 2# is heated to 100 °C, the ultraviolet lamp in Tower 2# is turned on, and chlorine gas is introduced into Tower 2#. The overflow liquid from Tower 2# is introduced into Tower 3#. Tower 3# is heated to 105 °C, the ultraviolet lamp in Tower 3# is turned on, and chlorine gas is introduced into Tower 3#. The overflow liquid from Tower 3# is introduced into Tower 4#. The temperature of Tower 4# is controlled at 58 °C. The tert-butyldiphenylsilyl mercaptan is atomized into 8-μm droplets by an ultrasonic atomizing nozzle and added to Tower 4# to contact the rising chlorine gas countercurrently. A rotary disk distributor is set at the 1 / 3 height of Tower 4#. The rotation speed of the rotary disk distributor is controlled at 250 rpm. The carbazolyl copolymer microspheres are evenly sprayed by the rotary disk distributor. The ultraviolet lamp in Tower 4# is turned on, and chlorine gas is introduced into Tower 4#. The residual chlorine in Tower 4# is sent to Tower 1#. When Tower 4# is full, the crude product flowing out of Tower 4# intercepts the microspheres through an ultrafiltration membrane, and then the tert-butyldiphenylsilyl mercaptan is extracted with an extractant. After layering, the organic phase is dried over anhydrous sodium sulfate to remove trace moisture to obtain p-chlorotrichlorotoluene; The alkaline phase and aqueous phase after extraction precipitate tert-butyldiphenylsilyl mercaptan through acidification, and after separation and drying, they are returned to Tower 4# for reuse; The generated hydrochloric acid and residual chlorine gas are absorbed by a tail gas treatment device; The main wavelengths of the ultraviolet lamps in Tower 1#, Tower 2#, and Tower 3# are the same, and the main wavelength is 365 nm; The light source power density of Tower 1# is 22 mW / cm 2 ; The light source power density of Tower 2# is 28 mW / cm 2 ; The light source power density of Tower 3# is 32 mW / cm 2 ; The main wavelength of the ultraviolet lamp in Tower 4# is 400 nm, and the light source power density is 18 mW / cm 2 ; The flow rate of the p-chlorotoluene raw material pump in Tower 1# is set at 420 g / h; The flow rate of chlorine gas in Tower 1# is 65 L / h; The flow rate of chlorine gas in Tower 2# is 85 L / h; The flow rate of chlorine gas in Tower 3# is 105 L / h; The flow rate of chlorine gas in Tower 4# is 135 L / h; The addition amount of tert-butyldiphenylsilyl mercaptan in Tower 4# is 28 g / h; The addition amount of the carbazolyl copolymer microspheres in the 4# tower is 100 g / h; The pore size of the ultrafiltration membrane is 8 μm; The extractant is a 5 wt% aqueous sodium hydroxide solution; The mass ratio of the extractant to the organic phase is 1:3.

[0046] After the 1# tower, 2# tower, 3# tower and 4# tower operate stably, 7536 g of p-chlorobenzotrichloride is obtained in 10 h, the yield is 98.79%, the chlorine consumption is 1.61 times of the theoretical value, and the purity of the sampled p-chlorobenzotrichloride is 98.54%.

[0047] (3) Fluorination reaction The p-chlorobenzotrichloride obtained in the chlorination reaction step is introduced into the 5# tower, the feeding flow rate of the p-chlorobenzotrichloride is controlled at 700 g / h, and then antimony pentafluoride is introduced. The addition amount of antimony pentafluoride is 0.20 g / h. The tail gas cooling system is turned on, the temperature of the 5# tower is raised to 90 °C, the pressure is controlled at 1.5 MPa, and the pressure is controlled at 1.2 MPa. After the 5# tower starts to overflow, hydrogen fluoride is introduced into the 5# tower. The feeding flow rate of hydrogen fluoride is 230 g / h, and the crude product of p-chlorobenzotrifluoride is obtained after the reaction.

[0048] (4) Rectification The crude product of p-chlorobenzotrifluoride is subjected to vacuum rectification under the conditions of a vacuum and a reflux ratio of 5:1, and the fraction with a top gas temperature of 110 - 120 °C is collected. After condensation, the product of p-chlorobenzotrifluoride is obtained; The vacuum degree of the vacuum is 0.035 Mpa.

[0049] The purity of the p-chlorobenzotrifluoride product is 99.62%, and the total two-step yield is 96.65%.

[0050] Compared with Example 1, in Example 5, in the fluorination reaction step, one reaction tower is omitted, and the addition of trifluoromethanesulfonic acid is also omitted. Antimony pentafluoride is directly used to catalyze and promote the fluorination reaction.

[0051] In the fluorination reaction, trifluoromethanesulfonic acid can protonate HF to H2F + (fluoronium ion), greatly enhancing its electrophilicity. At the same time, trifluoromethanesulfonic acid polarizes the C-Cl bond by forming hydrogen bonds or coordination interactions with the substrate, making it more easily substituted by F - Substitution promotes the chlorine-fluorine exchange reaction. The strong acidity of trifluoromethanesulfonic acid can inhibit the self-polymerization of HF to form (HF) n , reducing side reactions such as over-fluorination or aromatic ring fluorination caused by polymers. By protonating the intermediate, its decomposition or other side reactions are avoided. In Example 5, the addition of trifluoromethanesulfonic acid is omitted, resulting in an increase in by-products, a decrease in product purity, and a decrease in yield.

[0052] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions recorded in the foregoing embodiments or perform equivalent replacements on some of the technical features. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing parachlorobenzotrifluoride, characterized in that: The preparation method comprises the following steps: preparation of carbazole-based copolymer microspheres, chlorination reaction, fluorination reaction, and distillation; The preparation method of the carbazole-based copolymer microspheres comprises the following steps: dissolving 2,4,5,6-tetrakis(9-carbazole)-isophthalonitrile in N,N-dimethylformamide, adding triethylamine as an acid binding agent, dropping acryloyl chloride in an ice bath, stirring at room temperature for 10-14 hours, and after the reaction is completed, purifying by precipitation with ether, and drying to obtain a pretreated carbazole-based material; adding the pretreated carbazole-based material, a crosslinking agent and a photoinitiator into acetonitrile, stirring evenly, and ultrasonically dispersing for 10-15 minutes to form a uniform oil phase, dropping the oil phase into an aqueous phase containing a dispersant, and 6000-800 The mixture was stirred at 0 rpm for 10-15 min to form a stable water-in-oil emulsion, and the stirring speed was adjusted to 800-1200 rpm to control the droplet size, the system temperature was controlled to 25-35° C., and light with a wavelength of 365 nm was irradiated for 20-30 min to induce cross-linking of the acrylate groups in the ionic liquid. After the cross-linking was completed, the mixture was centrifuged at 3000-5000 rpm for 10-15 min to collect the microsphere products, and the products were washed alternately with water and ethanol for 2-3 times to remove the unreacted monomers and dispersant, and then dried in vacuo to obtain carbazole-based copolymer microspheres.

2. The method for preparing parachlorobenzotrifluoride according to claim 1, characterized in that: In the method for preparing the carbazole-based copolymer microspheres, The mass ratio of the 2,4,5,6-tetrakis(9-carbazolyl)-isophthalonitrile, N,N-dimethylformamide, triethylamine and acryloyl chloride is 1:15-20:1-1.2:1-1.2; The cross-linking agent is polyethylene glycol diacrylate; The molecular weight of the polyethylene glycol diacrylate is 400-600; The photoinitiator is 2-hydroxy-2-methylpropiophenone; The mass ratio of the pretreated carbazole-based material, the crosslinking agent, the photoinitiator and the acetonitrile is 10:1-1.5:0.1-0.12:40-60.

3. The method for preparing parachlorobenzotrifluoride according to claim 1, characterized in that: In the method for preparing the carbazole-based copolymer microspheres, The mass ratio of the water phase to the oil phase in the oil-in-water emulsion is 3:0.8-1.2; The light irradiation power density is 10-20 mW / cm 2 ; The dispersant is one of polyvinyl alcohol or sodium lauryl sulfate; The concentration of the dispersant in the water phase is 0.5-1 wt %.

4. The method for preparing parachlorobenzotrifluoride according to claim 1, characterized in that: The chlorination reaction method comprises the following steps: using 1#, 2#, 3# and 4# towers to be connected in series in sequence to realize continuous chlorination of para-chlorotoluene, adding raw para-chlorotoluene to the 1# tower, and not adding any material to the 2#, 3# and 4# towers; heating the 1# tower to 89-91° C., turning on the violet light lamp of the 1# tower, and starting to introduce chlorine gas into the 1# tower; after the 1# tower reacts for 4-5 hours, turning on the para-chlorotoluene raw material pump of the 1# tower, and introducing the overflow liquid of the 1# tower into the 2# tower; heating the 2# tower to 99-101° C., turning on the violet light lamp of the 2# tower, and starting to introduce chlorine gas into the 2# tower; the overflow liquid of the 2# tower is introduced into the 3# tower; heating the 3# tower to 104-106° C., turning on the violet light lamp of the 3# tower, and starting to introduce chlorine gas into the 3# tower; the overflow liquid of the 3# tower is introduced into the 4# tower; The tower is controlled to have a temperature of 55-60°C, tert-butyldiphenylsilanethiol is atomized into 5-10 μm droplets by an ultrasonic atomizing nozzle, added to the 4# tower, countercurrently contacted with the ascending chlorine gas, a rotating disc distributor is arranged at 1 / 3 of the tower height of the 4# tower, the rotation speed of the rotating disc distributor is controlled to be 200-300 rpm, the rotating disc distributor is used to evenly spray carbazole-based copolymer microspheres, the 4# tower ultraviolet light is turned on, chlorine gas is introduced into the 4# tower, the residual chlorine in the 4# tower is introduced into the 1# tower, when the 4# tower is full, the crude product flowing out of the 4# tower is intercepted by the microspheres through an ultrafiltration membrane, and the tert-butyldiphenylsilanethiol is extracted by an extractant, and after stratification, the organic phase is dried by anhydrous sodium sulfate or molecular sieve to remove trace water to obtain para-chlorotrichlorotoluene.

5. The method for preparing parachlorobenzotrifluoride according to claim 4, characterized in that: In the chlorination reaction method, The amount of the raw material parachlorotoluene added to the 1# tower is 4-6 cm below the overflow port of the tower; The main wavelength of the ultraviolet lamps of the 1# tower, the 2# tower and the 3# tower is the same, which is 365nm; The light source power density of the 1# tower is 20-25mW / cm 2 ; The light source power density of the 2# tower is 25-30mW / cm 2 ; The light source power density of the 3# tower is 30-35mW / cm 2 ; The main wavelength of the ultraviolet lamp of the 4# tower is 400nm, and the power density of the light source is 15-20mW / cm 2 .

6. The method for preparing parachlorobenzotrifluoride according to claim 4, characterized in that: In the chlorination reaction method, The flow rate of the parachlorotoluene feed pump in the 1# tower is set to 400-450 g / h; The flow rate of chlorine in the 1# tower is 60-70L / h; The flow rate of chlorine in the 2# tower is 80-90L / h; The flow rate of chlorine in the 3# tower is 100-110L / h; The flow rate of chlorine in the 4# tower is 130-140L / h; The addition amount of tert-butyldiphenylsilane mercaptan in the 4# tower is 25-30 g / h; The amount of carbazole copolymer microspheres added to the 4# tower is 95-105 g / h; The pore size of the ultrafiltration membrane is 5-10 μm; The extractant is a 4-6wt% aqueous sodium hydroxide solution; The mass ratio of the extractant to the organic phase is 1:2.5-3.

5.

7. The method for preparing parachlorobenzotrifluoride according to claim 1, characterized in that: The fluorination reaction method comprises the following steps: mixing the para-chlorobenzotrichloride obtained in the chlorination reaction step with trifluoromethanesulfonic acid and passing it into a 5# tower, controlling the passing flow rate of the para-chlorobenzotrichloride to be 650-750 g / h, opening the tail gas cooling system, heating the 5# tower to 58-62° C., controlling the pressure to be 1.1-1.3 MPa, and when the 5# tower begins to overflow, passing hydrogen fluoride into the 5# tower, passing the overflow liquid of the 5# tower into the 6# tower, and then passing antimony pentafluoride into the tower, heating the 6# tower to 88-92° C., controlling the pressure to be 1.4-1.6 MPa, passing hydrogen fluoride into the 6# tower, condensing and recovering the hydrogen fluoride in the 6# tower and passing it into the 5# tower, and obtaining a crude para-chlorobenzotrifluoride product after the reaction in the 6# tower.

8. The method for preparing parachlorobenzotrifluoride according to claim 7, characterized in that: In the fluorination reaction method, The mass ratio of para-chlorotrichlorotoluene to trifluoromethanesulfonic acid is 2350-2450:1; The amount of hydrogen fluoride introduced into the 5# tower is 100-120 g / h; The amount of antimony pentafluoride added is 0.18-0.22 g / h; The amount of hydrogen fluoride introduced into the 6# tower is 110-130 g / h.

9. The method for preparing parachlorobenzotrifluoride according to claim 1, characterized in that: The distillation method comprises: subjecting the crude para-chlorobenzotrifluoride product to vacuum distillation under the conditions of vacuum and a reflux ratio of 4-6:1, collecting the fraction with a gas phase temperature of 110-120° C. at the top of the tower, and condensing the fraction to obtain the para-chlorobenzotrifluoride product; The vacuum degree of the vacuum is 0.03-0.04Mpa.