阅读说明：本技术 一种四氯乙烯副产物生产多氟代苯衍生物的方法 (Method for producing polyfluorobenzene derivative from tetrachloroethylene byproduct ) 是由 吴晓秉 冯晓亮 曹鸣 应亚斐 于 2020-12-28 设计创作，主要内容包括：本发明涉及工业废物资源化利用领域,具体涉及一种四氯乙烯副产物生产多氟代苯衍生物的方法,包括如下步骤：(1)按照质量份数,将50-60份四氯乙烯副产物的高沸物固体残渣、75-90份氟化剂、1.0-2.0份催化剂加入到反应釜中,混合均匀,然后将反应釜密闭,通入氮气至釜压为1.5Mpa,然后慢慢将反应釜温度升高至400-450℃,直至反应釜内氮气压力为3.0-3.5Mpa,搅拌,反应时间为12-18h,反应结束,通过通过减压阀减压、冷凝得到粗产品；(2)将粗产品精馏分离,从塔顶依次得到前馏分、六氟苯、八氟甲苯、一氯五氟苯,塔底蒸馏残液主要为多氟多氯苯,返回氟化反应釜回用。本发明的方法,相对于传统工艺,氟化反应过程中生产六氟苯和八氟甲苯的单程转化率更高。(The invention relates to the field of industrial waste resource utilization, in particular to a method for producing a polyfluorobenzene derivative from a tetrachloroethylene byproduct, which comprises the following steps: (1) adding 50-60 parts by mass of high-boiling-point residue of a tetrachloroethylene byproduct, 75-90 parts by mass of a fluorinating agent and 1.0-2.0 parts by mass of a catalyst into a reaction kettle, uniformly mixing, then sealing the reaction kettle, introducing nitrogen until the kettle pressure is 1.5Mpa, then slowly raising the temperature of the reaction kettle to 400-450 ℃ until the nitrogen pressure in the reaction kettle is 3.0-3.5Mpa, stirring for 12-18h, and after the reaction is finished, decompressing and condensing through a decompression valve to obtain a crude product; (2) and (3) rectifying and separating the crude product, sequentially obtaining a front fraction, hexafluorobenzene, octafluorotoluene and chloropentafluorobenzene from the tower top, and returning the distillation residual liquid at the tower bottom, which is mainly polyfluoro-polychlorobenzene, to the fluorination reaction kettle for recycling. Compared with the traditional process, the method has higher conversion per pass of producing hexafluorobenzene and octafluorotoluene in the fluorination reaction process.)

1. A method for producing polyfluorobenzene derivatives from tetrachloroethylene byproducts is characterized by comprising the following steps:

(1) adding 50-60 parts by mass of high-boiling-point residue of a tetrachloroethylene byproduct, 75-90 parts by mass of a fluorinating agent and 1.0-2.0 parts by mass of a catalyst into a reaction kettle, uniformly mixing, then sealing the reaction kettle, introducing nitrogen until the kettle pressure is 1.5Mpa, then slowly raising the temperature of the reaction kettle to 400-450 ℃ until the nitrogen pressure in the reaction kettle is 3.0-3.5Mpa, stirring for 12-18h, and after the reaction is finished, decompressing through a decompression valve and condensing to obtain a crude product;

(2) and (3) rectifying and separating the crude product, sequentially obtaining a front fraction, hexafluorobenzene, octafluorotoluene and chloropentafluorobenzene from the tower top, and returning the distillation residual liquid at the tower bottom, which is mainly polyfluoro-polychlorobenzene, to the fluorination reaction kettle for recycling.

2. The method according to claim 1, wherein the fluorinating agent of step (1) is prepared by:

according to the mass portion, 100-120 portions of industrial potassium fluoride and 550-650 portions of methanol are uniformly mixed, stirred for 2-3h at 20-30 ℃, then added with 0.5-1.5 portions of quaternary ammonium salt, 0.5-1.5 portions of quaternary phosphonium salt and 0.5-1.5 portions of organic metal halide, stirred for 30-60min, distilled, recovered with methanol, and the obtained powder is dried for 5-8h at 120 ℃ of 100-120 ℃ to obtain the modified fluorinating agent.

3. The method according to claim 2, wherein the quaternary ammonium salt is one or more of trimethyloctadecyl ammonium chloride, octyldecyl dimethyl ammonium chloride and N-benzylmethylpyridinium chloride.

4. The method according to claim 2, wherein the quaternary phosphonium salt is one or more of tetraphenylphosphonium bromide, tetrakis (dimethylnitrogenphosphonium bromide) and tributyltetradecylphosphonium chloride.

5. The method of claim 2, wherein the organic metal halide is one or more of triphenylcopper fluoride, triphenyltin fluoride and triphenylbismuth difluoride.

6. The method according to claim 1, wherein the catalyst of step (1) is prepared by:

according to the mass parts, 25-32.5 parts of dimethylamine aqueous solution with the mass percent content of 40% are filled into a three-neck flask, the three-neck flask is cooled by ice bath, the temperature of the dimethylamine is controlled to be 0-10 ℃, 35-39 parts of chloropropene and 28-36.5 parts of sodium hydroxide aqueous solution with the mass percent content of 30% are alternately dripped into the dimethylamine, the dripping time is controlled to be 1-2 hours, then the temperature is raised to 40-50 ℃ after heat preservation and stirring for 1-2 hours, the reaction is carried out for 7-9 hours, then 0.5-2.1 parts of ammonium persulfate, 0.02-0.3 part of 1-allyl-3-butylimidazole tetrafluoroborate and 0.2-1.2 parts of 1-allylpiperazine are heated to 60-80 ℃ and reacted for 4-6 hours, the temperature is reduced to the normal temperature, and the catalyst is obtained by filtering, washing and drying.

Technical Field

The invention relates to the field of industrial waste resource utilization, in particular to a method for producing a polyfluorobenzene derivative from a tetrachloroethylene byproduct.

Background

In the process of producing tetrachloroethylene, byproduct high-boiling residue solid residue can be generated, the main components comprise organic matters such as carbon tetrachloride, hexachloropropane, hexachlorobutane, hexachlorobenzene and octachlorotoluene, wherein the hexachlorobenzene accounts for 90-95%, and the octachlorotoluene accounts for about 3-5%, the hexachlorobenzene and the octachlorotoluene are difficult to degrade by the environment, and the environment is polluted durably.

The hexafluorobenzene product has wide application, is an important intermediate in liquid crystal material and medicine synthesis, and has the greatest application at present in preparing pentafluorophenol serving as an intermediate of an anti-hepatitis C medicament sofosbuvir, which is the most successful medicament for treating hepatitis C at present and has the cure rate of nearly 100%. The chloropentafluorobenzene can be used for preparing pentafluoroaniline through ammonolysis reaction and also can be used for preparing hexafluorobenzene through continuous deep fluorination, and is an important fluorine-containing fine chemical. Octafluorotoluene is useful as an intermediate for fluoropolymers and pharmaceuticals, as well as solvents and anesthetics. Therefore, if environmentally-friendly byproducts such as hexachlorobenzene and octachlorotoluene can be converted into products such as hexafluorobenzene and octafluorotoluene, resource utilization is realized, and the method has great social value and economic value.

CN201510083596.0 discloses an environment-friendly treatment method of hexachlorobenzene, which comprises the following steps of (1) putting hexachlorobenzene and an active potassium fluoride solution organic solvent into a single reactor; (2) carrying out pressure test leakage detection and nitrogen replacement on a single reactor filled with reaction liquid; (3) heating the single reactor to 200-300 ℃, and boosting the pressure to 2.0-3.0 MPa; reacting for 10-15 h at the reaction temperature and the reaction pressure; (4) evaporating reaction products in a single reactor, condensing and collecting; (5) rectifying and separating hexafluorobenzene and chloropentafluorobenzene of reaction products; (6) collecting the fluochlorobenzene (by-product) and the organic solvent in a single reactor by reduced pressure distillation; then taking out the potassium chloride residue in the single reactor, drying the chlorobenzene, and adding the chlorobenzene into the single reactor again for continuous use. The reaction condition is mild, the conversion rate and the yield are high, the pollution is reduced, and meanwhile, a practical chemical intermediate is obtained, and the application prospect is wide.

Cn201410244652.x discloses a method for catalytic degradation of hexachlorobenzene, which comprises the following steps: firstly, filling a catalyst into a fixed bed reactor, and reducing the catalyst; uniformly mixing hexachlorobenzene steam and preheated hydrogen to obtain mixed gas, introducing the mixed gas into a fixed bed reactor after reduction treatment is finished, and carrying out catalytic hydrogenation dechlorination reaction on a catalyst to obtain mixed gas of benzene steam, hydrogen chloride gas and unreacted hydrogen; and thirdly, feeding the mixed gas of the benzene steam, the hydrogen chloride gas and the unreacted hydrogen into a condenser for condensation to convert the benzene into liquid, then feeding the hydrogen chloride gas and the unreacted hydrogen in the mixed gas into an absorption tower to absorb the hydrogen chloride by using ammonia water, and compressing the unreacted hydrogen by a compressor and then returning the hydrogen to be recycled. When the method is used for catalytic hydrogenation degradation of hexachlorobenzene, no solvent is needed to be added, and byproducts of benzene and ammonium chloride are produced, so that zero emission of pollutants can be achieved, and the method is a green process for efficiently degrading hexachlorobenzene.

CN201810530354.5 discloses a separation system and a separation method for a byproduct high-boiling residue in tetrachloroethylene production, wherein the system comprises a pressure reduction sublimation device, a first storage tank, a hexachloroethane separation system, a hexachlorobenzene separation system and a hexachlorobutadiene separation system; wherein, the light component export of decompression sublimation unit links to each other with first storage tank feed inlet, and the sublimation gas outlet of decompression sublimation unit links to each other with hexachloroethane piece-rate system's feed inlet, and the residue export of decompression sublimation unit links to each other with hexachlorobenzene piece-rate system, and hexachloroethane piece-rate system and hexachlorobenzene piece-rate system link to each other with hexachlorobutadiene piece-rate system respectively. By sequentially carrying out reduced pressure distillation and reduced pressure sublimation on the byproduct high-boiling substances in the production of tetrachloroethylene, hexachlorobutadiene can be retained in the heavy components to the maximum extent, and the byproduct high-boiling substances in the production of tetrachloroethylene are separated and purified one by combining the processes of solvent washing, filtering, rectification and the like, so that the high-efficiency separation of hexachloroethane, hexachlorobutadiene and hexachlorobenzene is realized.

In the prior art, hexachlorobenzene and the like are prepared into hexafluorobenzene through halogen replacement reaction, solvents such as DMSO and the like are generally adopted, single tetrakis (diethylamine) phosphorus bromide, hexadecyltributylphosphorus bromide and the like are adopted as catalysts, the catalytic efficiency is low, the reaction time is long, the catalysts are easy to decompose and inactivate at high temperature, the side reactions are more, the conventional solvents have poor thermal stability, are easy to decompose or coke, and are difficult to recycle. The high-temperature reaction has extremely high requirements on the high-temperature corrosion resistance and the mechanical strength of equipment, and particularly, the stirring paddle is extremely easy to deform and deviate from the center, so that the mass transfer and heat transfer effects are directly influenced, and the fluorination reaction efficiency is low. In addition, because the reaction temperature is too high, a large amount of intermediate products of polyfluoro-polychlorobenzene (such as chloropentafluorobenzene, dichlorotetrafluorobenzene and the like) cannot be completely liquefied and are accumulated on the upper part of the reaction kettle, and the fluorination of hexachlorobenzene stays in the polyfluoro-polychlorobenzene stage to a great extent, the invention provides that the pressure is increased to 1.5Mpa before the reaction, the contact between the intermediate products and the fluorination reagent in the fluorination reaction is improved to a great extent, and the yield of hexafluorobenzene and octafluorotoluene in the fluorination reaction process is improved.

Disclosure of Invention

Compared with the traditional process, the method for producing the polyfluorobenzene derivative from the tetrachloroethylene by-product has higher one-pass conversion rate and yield of hexafluorobenzene and octafluorotoluene produced in the fluorination reaction process.

A method for producing polyfluorobenzene derivatives from tetrachloroethylene byproducts is characterized by comprising the following steps:

(1) adding 50-60 parts by mass of high-boiling-point residue of a tetrachloroethylene byproduct, 75-90 parts by mass of a fluorinating agent and 1.0-2.0 parts by mass of a catalyst into a reaction kettle, uniformly mixing, then sealing the reaction kettle, introducing nitrogen until the kettle pressure is 1.5Mpa, slowly raising the temperature of the reaction kettle to 400-450 ℃ until the nitrogen pressure in the reaction kettle is 3.0-3.5Mpa, stirring, reacting for 12-18h, and after the reaction is finished, decompressing through a decompression valve and condensing to obtain a crude product;

(2) and (3) rectifying and separating the crude product, sequentially obtaining a front fraction, hexafluorobenzene, octafluorotoluene and chloropentafluorobenzene from the tower top, and returning the distillation residual liquid at the tower bottom, which is mainly polyfluoro-polychlorobenzene, to the fluorination reaction kettle for recycling.

Preferably, the preparation method of the fluorinating agent in the step (1) comprises the following steps:

according to the mass portion, 100-120 portions of industrial potassium fluoride and 550-650 portions of methanol are uniformly mixed, stirred for 2-3h at 20-30 ℃, then added with 0.5-1.5 portions of quaternary ammonium salt, 0.5-1.5 portions of quaternary phosphonium salt and 0.5-1.5 portions of organic metal halide, stirred for 30-60min, distilled, recovered with methanol, and the obtained powder is dried for 5-8h at 120 ℃ of 100-120 ℃ to obtain the modified fluorinating agent.

Preferably, the quaternary ammonium salt is one or a combination of more of trimethyloctadecyl ammonium chloride, octyldecyl dimethyl ammonium chloride and N-benzyl methyl pyridinium chloride.

Preferably, the quaternary phosphonium salt is one or a combination of tetraphenylphosphonium bromide, tetra (dimethyl nitrogen) phosphonium bromide and tri-n-butyltetradecylphosphonium chloride.

Preferably, the organic metal halide is one or a combination of triphenyl copper fluoride, triphenyl tin fluoride and triphenyl bismuth difluoride.

Preferably, the preparation method of the catalyst in the first step comprises the following steps:

according to the mass parts, 25-32.5 parts of dimethylamine aqueous solution with the mass percent content of 40% are filled into a three-neck flask, the three-neck flask is cooled by ice bath, the temperature of the dimethylamine is controlled to be 0-10 ℃, 35-39 parts of chloropropene and 28-36.5 parts of sodium hydroxide aqueous solution with the mass percent content of 30% are alternately dripped into the dimethylamine, the dripping time is controlled to be 1-2 hours, then the temperature is raised to 40-50 ℃ after heat preservation and stirring for 1-2 hours, the reaction is carried out for 7-9 hours, then 0.5-2.1 parts of ammonium persulfate, 0.02-0.3 part of 1-allyl-3-butylimidazole tetrafluoroborate and 0.2-1.2 parts of 1-allylpiperazine are heated to 60-80 ℃ and reacted for 4-6 hours, the temperature is reduced to the normal temperature, and the catalyst is obtained by filtering, washing and drying.

In the preparation process of the catalyst, dimethylamine reacts with chloropropene to prepare a dimethyl diallyl ammonium chloride monomer, and then the dimethyl diallyl ammonium chloride monomer reacts with 1-allyl-3-butyl imidazole tetrafluoroborate and 1-allyl piperazine through free radical copolymerization to obtain the high molecular catalyst.

The reaction formula for preparing dimethyl diallyl ammonium chloride monomer is as follows:

compared with the prior art, the invention has the beneficial effects that:

1. the fluorinating agent is prepared by modifying the potassium fluoride, the phase transfer catalyst is loaded on the surface of the potassium fluoride, the dispersion is uniform, the contact area of the reaction liquid and the potassium fluoride is greatly increased, the reaction efficiency is greatly improved, and the reaction temperature and time are reduced.

2. By adding the high molecular catalyst, the stability and the catalytic efficiency of the catalyst are greatly improved, the catalyst can be recycled, and the production cost is reduced.

3. The method adopted by the invention completely does not add organic solvent, realizes solvent-free fluorination reaction, and introduces nitrogen in advance for pressurization, so that the pressure of the system is improved at the same reaction temperature, intermediate components with lower boiling points are prevented from being accumulated in a gas phase, the contact area of potassium fluoride and reaction liquid is increased, and the reaction yield is greatly improved.

Detailed Description

The raw material tetrachloroethylene byproduct used in the following examples is industrial distillation high-boiling residue, the main components are hexachlorobenzene (mass percentage content is 90-95%), octachlorotoluene (mass percentage content is 3-5%), other organic impurities (mass percentage content is 3-5%), and the others are all commercial products.

The content of the hexafluorobenzene product measured by the embodiment of the invention is the content of the hexafluorobenzene product by mass percent, and the hexafluorobenzene product is analyzed by an Agilent 6890 gas chromatograph.

A chromatographic column: type DB-5 capillary columns (30 m 0.32mm ID 0.25 um);

vaporization chamber temperature: 220 ℃;

a detector at 220 ℃;

keeping the column temperature at 50 ℃ for 2 min; the heating rate is 5 ℃/min, the temperature is raised to 70 ℃, and the temperature is kept for 1 min; then the temperature is raised to 200 ℃ at the rate of 20 ℃/min and kept for 2 min.

The content of the chloropentafluorobenzene and the octafluorotoluene product measured in the embodiment of the invention is the content in percentage by mass, and an Agilent 6890 gas chromatograph is adopted for analysis.

A chromatographic column: DB-5 type capillary column (30 m 0.32mm ID 0.25 um)

Vaporization chamber temperature: 250 ℃;

a detector at 250 ℃;

keeping the column temperature at 50 ℃ for 2 min; the heating rate is 10 ℃/min, the temperature is increased to 150 ℃, and the temperature is kept for 5 min; then the temperature is raised to 220 ℃ at the rate of 20 ℃/min and kept for 5 min.

Methods for calculating yields of hexafluorobenzene and chloropentafluorobenzene in examples:

the mass fraction of hexachlorobenzene in the raw materials is tested, the mass of hexachlorobenzene in the added byproduct mixture is calculated and converted into the mass of the substance, the mass of hexafluorobenzene and chloropentafluorobenzene obtained by the reaction is weighed and converted into the mass of the substance, and the mass of hexafluorobenzene and chloropentafluorobenzene is divided by the mass of the hexachlorobenzene to obtain the yield of hexafluorobenzene and chloropentafluorobenzene.

Method for calculating yield of octafluorotoluene in examples:

the mass fraction of octachlorotoluene in the raw material was measured, the mass of octachlorotoluene in the charged by-product mixture was calculated and converted into the amount of substance, the mass of octafluorotoluene obtained by the reaction was weighed and converted into the amount of substance, and the amount of substance of octachlorotoluene was divided by the amount of substance of octachlorotoluene to obtain the yield of octafluorotoluene.

Example 1

(1) Adding 50Kg of high-boiling-point product solid residue by-product of tetrachloroethylene, 75Kg of fluorinating agent and 1Kg of catalyst into a reaction kettle, uniformly mixing, then sealing the reaction kettle, introducing nitrogen until the kettle pressure is 1.5Mpa, then slowly raising the temperature of the reaction kettle to 400 ℃, keeping the nitrogen pressure in the reaction kettle at 3.0Mpa, stirring, reacting for 12h, reducing the pressure through a pressure reducing valve, and condensing to obtain a crude product;

(2) and (3) rectifying and separating the crude product, sequentially obtaining a front fraction, hexafluorobenzene, octafluorotoluene and chloropentafluorobenzene from the tower top, and returning the distillation residual liquid at the tower bottom, which is mainly polyfluoro-polychlorobenzene, to the fluorination reaction kettle for recycling.

The preparation method of the fluorinating agent in the step (1) comprises the following steps: 100Kg of industrial potassium fluoride and 550Kg of methanol are uniformly mixed, stirred for 2h at 20 ℃, then added with 0.5Kg of octyl decyl dimethyl ammonium chloride, 1.5Kg of tetra (dimethyl nitrogen) phosphonium bromide and 0.5Kg of triphenyl copper fluoride, stirred for 30min, distilled, recycled with methanol, and the obtained powder is dried for 5h at 100 ℃ to obtain the modified fluorinating agent.

The preparation method of the catalyst in the step (1) comprises the following steps: putting 25Kg of dimethylamine aqueous solution with the mass percent of 40 percent into a three-neck flask, cooling by using an ice bath, controlling the temperature of the dimethylamine to be 0 ℃, alternately dripping 35Kg of chloropropene and 28Kg of sodium hydroxide aqueous solution with the mass percent of 30 percent into the dimethylamine, controlling the dripping time to be 1h, then heating to 40 ℃ after stirring for 1h under heat preservation, reacting for 9h, then adding 0.5Kg of ammonium persulfate, 0.02Kg of 1-allyl-3-butylimidazole tetrafluoroborate and 0.2Kg of 1-allyl piperazine, heating to 60 ℃, reacting for 4h, cooling to normal temperature, filtering, washing and drying to obtain the catalyst.

The yield of the hexafluorobenzene is 70.2 percent (calculated by hexachlorobenzene), and the content is 99.8 percent; the yield of the chloropentafluorobenzene is 12 percent (calculated by hexachlorobenzene), and the content is 99.7 percent; the yield of octafluorotoluene was 65% (based on octachlorotoluene) and the content was 99.8%.

Example 2

(1) Adding 60Kg of high-boiling-point solid residue of a tetrachloroethylene byproduct, 90Kg of fluorinating agent and 2Kg of catalyst into a reaction kettle, uniformly mixing, then sealing the reaction kettle, introducing nitrogen until the kettle pressure is 1.5Mpa, then slowly raising the temperature of the reaction kettle to 450 ℃ until the nitrogen pressure in the reaction kettle is 3.5Mpa, stirring for 18h, reducing the pressure through a pressure reducing valve, and condensing to obtain a crude product;

(2) and (3) rectifying and separating the crude product, sequentially obtaining a front fraction, hexafluorobenzene, octafluorotoluene and chloropentafluorobenzene from the tower top, and returning the distillation residual liquid at the tower bottom, which is mainly polyfluoro-polychlorobenzene, to the fluorination reaction kettle for recycling.

The preparation method of the fluorinating agent in the step (1) comprises the following steps: 120Kg of industrial potassium fluoride and 650Kg of methanol are mixed uniformly, stirred for 3h at 30 ℃, then added with 1.5Kg of trimethyl octadecyl ammonium chloride, 0.5Kg of tetraphenyl phosphonium bromide salt and 0.5Kg of triphenyl tin fluoride, stirred for 60min, distilled, recovered methanol, and the obtained powder is dried for 8h at 120 ℃ to obtain the modified fluorinating agent.

The preparation method of the catalyst in the step (1) comprises the following steps: putting 32.5Kg of dimethylamine aqueous solution with the mass percent content of 40% into a three-neck flask, cooling by using an ice bath, controlling the temperature of the dimethylamine to be 10 ℃, alternately dropping 39Kg of chloropropene and 36.5Kg of sodium hydroxide aqueous solution with the mass percent content of 30% into the dimethylamine, controlling the dropping time to be 2h, then keeping the temperature and stirring for 2h, heating to 50 ℃, reacting for 7h, then adding 2.1Kg of ammonium persulfate, 0.3Kg of 1-allyl-3-butylimidazole tetrafluoroborate and 1.2Kg of 1-allyl piperazine, heating to 80 ℃, reacting for 6h, cooling to the normal temperature, filtering, washing and drying to obtain the catalyst.

The yield of the hexafluorobenzene is 77.8 percent (calculated by hexachlorobenzene), and the content is 99.8 percent; the yield of the chloropentafluorobenzene is 9 percent (calculated by hexachlorobenzene), and the content is 99.7 percent; the yield of octafluorotoluene was 68.2% (based on octachlorotoluene) and the content was 99.8%.

Example 3

(1) Adding 60Kg of high-boiling-point solid residue of a tetrachloroethylene byproduct, 90Kg of fluorinating agent and 1.5Kg of catalyst into a reaction kettle, uniformly mixing, then sealing the reaction kettle, introducing nitrogen until the kettle pressure is 1.5Mpa, then slowly raising the temperature of the reaction kettle to 420 ℃ until the nitrogen pressure in the reaction kettle is 3.1Mpa, stirring, reacting for 16h, reducing the pressure through a pressure reducing valve, and condensing to obtain a crude product;

(2) and (3) rectifying and separating the crude product, sequentially obtaining a front fraction, hexafluorobenzene, octafluorotoluene and chloropentafluorobenzene from the tower top, and returning the distillation residual liquid at the tower bottom, which is mainly polyfluoro-polychlorobenzene, to the fluorination reaction kettle for recycling.

The preparation method of the fluorinating agent in the step (1) comprises the following steps: 100Kg of industrial potassium fluoride and 550Kg of methanol are mixed uniformly, stirred for 2h at 25 ℃, then added with 0.6Kg of N-benzylmethylpyridinium chloride, 0.6Kg of tributyl tetradecyl phosphorus chloride and 1.0Kg of triphenyl bismuth difluoride, stirred for 45min, distilled, recycled with methanol, and the obtained powder is dried for 6h at 110 ℃ to obtain the modified fluorinating agent.

The preparation method of the catalyst in the step (1) comprises the following steps: putting 28Kg of dimethylamine aqueous solution with the mass percent content of 40 percent into a three-neck flask, cooling by using an ice bath, controlling the temperature of dimethylamine to be 5 ℃, alternately dropping 36.6Kg of chloropropene and 31.5Kg of sodium hydroxide aqueous solution with the mass percent content of 30 percent into the dimethylamine, controlling the dropping time to be 1.5h, then keeping the temperature and stirring for 1.5h, heating to 45 ℃, reacting for 8h, then adding 1.0Kg of ammonium persulfate, 0.15Kg of 1-allyl-3-butylimidazole tetrafluoroborate and 1.0Kg of 1-allylpiperazine, heating to 70 ℃, reacting for 5h, cooling to the normal temperature, filtering, washing and drying to obtain the catalyst.

The yield of the hexafluorobenzene is 73.2 percent (calculated by hexachlorobenzene), and the content is 99.8 percent; the yield of the chloropentafluorobenzene is 11 percent (calculated by hexachlorobenzene), and the content is 99.7 percent; the yield of octafluorotoluene was 68.1% (based on octachlorotoluene) and the content was 99.8%.

Example 4

(1) Adding 55 Kg of high-boiling-point product solid residue of a tetrachloroethylene byproduct, 75Kg of fluorinating agent and 1.5Kg of catalyst into a reaction kettle, uniformly mixing, then sealing the reaction kettle, introducing nitrogen until the kettle pressure is 1.5Mpa, then slowly raising the temperature of the reaction kettle to 450 ℃ until the nitrogen pressure in the reaction kettle is 3.5Mpa, stirring for 18h, reducing the pressure through a pressure reducing valve, and condensing to obtain a crude product after the reaction is finished;

(2) and (3) rectifying and separating the crude product, sequentially obtaining a front fraction, hexafluorobenzene, octafluorotoluene and chloropentafluorobenzene from the tower top, and returning the distillation residual liquid at the tower bottom, which is mainly polyfluoro-polychlorobenzene, to the fluorination reaction kettle for recycling.

The preparation method of the fluorinating agent in the step (1) comprises the following steps: 115Kg of industrial potassium fluoride and 600Kg of methanol are mixed uniformly, stirred for 2.5h at 30 ℃, then added with 1.0Kg of trimethyl octadecyl ammonium chloride, 0.50 Kg of octyl decyl dimethyl ammonium chloride, 0.5Kg of tetraphenyl phosphonium bromide salt and 1.5Kg of triphenyl tin fluoride, stirred for 60min, distilled, recovered methanol, and the obtained powder is dried for 8h at 120 ℃ to obtain the modified fluorinating agent.

The preparation method of the catalyst in the step (1) comprises the following steps: putting 32.5Kg of dimethylamine aqueous solution with the mass percent content of 40% into a three-neck flask, cooling by using an ice bath, controlling the temperature of the dimethylamine to be 10 ℃, alternately dropping 39Kg of chloropropene and 36.5Kg of sodium hydroxide aqueous solution with the mass percent content of 30% into the dimethylamine, controlling the dropping time to be 2h, then keeping the temperature and stirring for 2h, heating to 50 ℃, reacting for 9h, then adding 2.1Kg of ammonium persulfate, 0.3Kg of 1-allyl-3-butylimidazole tetrafluoroborate and 1.2Kg of 1-allyl piperazine, heating to 80 ℃, reacting for 6h, cooling to the normal temperature, filtering, washing and drying to obtain the catalyst.

The yield of the hexafluorobenzene is 74.6 percent (calculated by hexachlorobenzene), and the content is 99.8 percent; the yield of the chloropentafluorobenzene is 9.4 percent (calculated by hexachlorobenzene), and the content is 99.7 percent; the yield of octafluorotoluene was 67.8% (based on octachlorotoluene) and the content was 99.8%.

Comparative example 1

Compared with the example 2, the fluorinating agent added is common industrial potassium fluoride, and the rest is the same as the example 2, the yield of the hexafluorobenzene is 56 percent (calculated by the hexachlorobenzene), and the content is 99.8 percent; the yield of the chloropentafluorobenzene is 7.5 percent (calculated by hexachlorobenzene), and the content is 99.5 percent; the yield of octafluorotoluene was 46.2% (based on octachlorotoluene) and the content was 99.7%.

Comparative example 2

Relative to the example 2, no catalyst is added in the reaction process of the step (1), and the rest is the same as the example 2, so that the yield of the hexafluorobenzene is 52.3 percent (calculated by the hexachlorobenzene), and the content is 99.8 percent; the yield of the chloropentafluorobenzene is 7.1 percent (calculated by hexachlorobenzene), and the content is 99.5 percent; the yield of octafluorotoluene (calculated as octachlorotoluene) was 45.0%, and the content was 99.5%.

Comparative example 3

With respect to the example 2, the yield of hexafluorobenzene obtained by the same method as that of the example 2 except that no tetraphenylphosphonium bromide salt was added during the modification of potassium fluoride was 69% (calculated on the basis of hexachlorobenzene) and the content was 99.8%; the yield of the chloropentafluorobenzene is 8.2 percent (calculated by hexachlorobenzene), and the content is 99.6 percent; the yield of octafluorotoluene was 60.2% (based on octachlorotoluene) and the content was 99.5%.