Low-cost environment-friendly process for producing 1, 4-bis (4-fluorobenzoyl) benzene

Abstract

The invention discloses a low-cost and environment-friendly process for producing 1, 4-bis (4-fluorobenzoyl) benzene, and belongs to the technical field of Friedel-Craft reaction, fluorobenzene and paraphthaloyl chloride react to generate 1, 4-bis (4-fluorobenzoyl) benzene, after reaction quenching, filtering is performed to obtain a crude product 1, 4-bis (4-fluorobenzoyl) benzene and filtrate, and the 1, 4-bis (4-fluorobenzoyl) benzene is purified in a sublimation crystallization mode; standing and layering the filtrate in an inclined plate layering device, respectively treating an oil layer and a water layer, dehydrating a fluorobenzene layer in a dehydrating tower, and returning fluorobenzene; the water phase is firstly subjected to organic matter removal treatment, the obtained organic matter enters a fluorobenzene recovery device to be sleeved back, and the obtained water phase is a byproduct of crystallized aluminum chloride in an evaporative crystallization device. According to the process, the 1, 4-bis (4-fluorobenzoyl) benzene is produced in a sublimation crystallization mode instead of a solution crystallization mode, no waste solvent is generated, the waste solvent does not need to be recycled, the cost is low, organic matter removal and evaporative crystallization treatment is carried out on wastewater, organic matter recycling is carried out, crystalline aluminum chloride is produced as a byproduct, and wastewater and waste salt are not discharged.

Description

Technical Field

[0001] The present invention relates to the technical field of Friedel-Craft reaction, and specifically relates to a process for producing 1,4-bis(4-fluorobenzoyl)benzene with low cost and environmental protection. Background Art

[0002] 1,4-Bis(4-fluorobenzoyl)benzene is an important chemical intermediate with the molecular formula C 20 H 12 F 2 O 2 , molecular weight 322, melting point 220°C - 222°C, solubility: insoluble in water, DMAC, acetone and other organic solvents at room temperature. The monomer of 1,4-bis(4-fluorobenzoyl)benzene can be used to produce PEAK series plastics such as PEEK and PEKK. Compared with the traditional DFBP (difluorobenzophenone), the PEAK series plastics manufactured from 1,4-bis(4-fluorobenzoyl)benzene have varying degrees of improvement in mechanical properties, heat resistance and other aspects.

[0003] In the prior art, the synthesis of 1,4-bis(4-fluorobenzoyl)benzene mostly uses terephthaloyl chloride and excessive fluorobenzene under the condition of anhydrous aluminum trichloride as a catalyst. After the synthesis, the crude 1,4-bis(4-fluorobenzoyl)benzene is purified by solution crystallization to remove impurities such as the isomer 1,2-bis(4-fluorobenzoyl)benzene in the crude product, such as Patent US5300693A, Patent US4820791A, Patent DE3531837A1, Patent CN115135691A, etc. In the production process, not only a large amount of wastewater is generated during the quenching process of aluminum chloride, but also the removal effect of 1,2-bis(4-fluorobenzoyl)benzene in the solution crystallization process is poor, and multiple crystallizations are required, resulting in a large amount of waste solvent, and the energy consumption for solvent recovery is high, which affects the industrial production of 1,4-bis(4-fluorobenzoyl)benzene.

[0004] In view of the problems existing in the above prior art, the present invention combines the design and use experience in related fields for many years, and designs a green, environmentally friendly and low-cost production process for 1,4-bis(4-fluorobenzoyl)benzene to overcome the above defects and produce high-purity 1,4-bis(4-fluorobenzoyl)benzene. Summary of the Invention

[0005] For the problems existing in the prior art, the present invention provides a process for producing 1,4-bis(4-fluorobenzoyl)benzene with low cost and environmental protection. The process uses an evaporation crystallization process to treat the organic wastewater, the organic matter and water are recycled, and by-product crystalline aluminum chloride is produced. The crude 1,4-bis(4-fluorobenzoyl)benzene is purified by sublimation crystallization to remove isomers, and no waste solvent is generated.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows: A low-cost and environmentally friendly process for producing 1,4-bis(4-fluorobenzoyl)benzene, comprising the following steps: Step 1, using fluorobenzene as a solvent, fluorobenzene and terephthaloyl chloride undergo a Friedel-Craft reaction under the catalysis of anhydrous aluminum chloride. After the reaction ends, the reaction mixture enters a washing kettle for reaction quenching to obtain a quenched mixture; Step 2, subjecting the quenched mixture in Step 1 to solid-liquid separation in a centrifugal filtration unit I to obtain a filter cake and a filtrate. The filter cake is the crude product 1,4-bis(4-fluorobenzoyl)benzene; Step 3, adding the filter cake in Step 2 to a sublimation crystallization device for crystallization to obtain purified 1,4-bis(4-fluorobenzoyl)benzene, and the purity of the purified 1,4-bis(4-fluorobenzoyl)benzene is greater than or equal to 99.81%; Step 4, pumping the filtrate in Step 2 into an inclined plate stratifier for static stratification. The upper layer is the fluorobenzene layer, and the lower layer is the acidic organic wastewater layer containing aluminum ions. The fluorobenzene layer is passed through a fluorobenzene dehydration tower for dehydration and then enters the fluorobenzene raw material tank for recycling; Step 5, the acidic organic wastewater layer containing aluminum ions in Step 4 enters a ceramic membrane filter for filtration. The filtered aqueous phase enters a de-organic tower, and the aqueous phase at the bottom of the de-organic tower enters an evaporator for dehydration and a DTB crystallizer for crystallization in sequence, and crystalline aluminum chloride is obtained by centrifugation.

[0007] Preferably, when fluorobenzene reacts with terephthaloyl chloride in Step 1, the reaction temperature is 5 - 50 °C, the reaction pressure is 1 - 1.2 atm, and the reaction time is 4 - 16 h; The molar ratio of fluorobenzene to terephthaloyl chloride is 20:1 - 5:1, and the molar ratio of terephthaloyl chloride to anhydrous aluminum chloride is 1:2 - 1:4.

[0008] Preferably, the washing solvent used in the washing kettle in Step 1 is an acidic aqueous solution, and the mass ratio of the washing solvent to the reaction mixture is 0.5:1 - 4:1; The acidic aqueous solution is hydrochloric acid; The residence time of the reaction mixture in the washing kettle is 0.3 - 1 h, and the temperature in the washing kettle is 0 - 73 °C.

[0009] Preferably, the sublimation crystallization device includes a sublimation kettle, a first-stage crystallization tank, and a second-stage crystallization tank connected in sequence.

[0010] Preferably, the temperature of the sublimation kettle is controlled at 200 - 280 °C, and the temperature of the first-stage crystallization tank is controlled at 150 - 190 °C; The temperature of the second-stage crystallization tank is controlled at 10 - 40 °C.

[0011] Preferably, in step 4, the residence time of the filtrate in the inclined plate separator is 0.3 - 1 h, and the temperature of the inclined plate separator is 0 - 45 °C.

[0012] Preferably, the number of trays in the fluorobenzene dehydration tower in step 4 is 40 - 60, the pressure inside the fluorobenzene dehydration tower is 1 atm, the top temperature of the fluorobenzene dehydration tower is 73 - 85 °C, and the bottom temperature of the fluorobenzene dehydration tower is 85 - 90 °C.

[0013] Preferably, in step 5, the precision of the ceramic membrane filter is 10 - 20 μm, the number of trays in the de - organic tower is 40 - 60, the top pressure of the de - organic tower is 1 atm, the top temperature of the de - organic tower is 73 - 98 °C, and the bottom temperature of the de - organic tower is 105 - 120 °C.

[0014] Preferably, in step 5, the temperature of the evaporator is 65 - 85 °C, and the pressure is 5 - 15 kPa.

[0015] Preferably, in step 5, the temperature of the DTB crystallizer is 55 - 75 °C, and the pressure is 1 - 10 kPa.

[0016] The advantages of this invention are as follows: 1. After synthesizing 1,4 - bis(4 - fluorobenzoyl)benzene, this invention obtains 1,4 - bis(4 - fluorobenzoyl)benzene and the filtrate through solid - liquid separation. The filtrate is allowed to stand for layering to obtain a fluorobenzene layer and an acidic organic wastewater layer containing aluminum ions, and post - treatment is carried out on them respectively, reducing the difficulty and treatment volume of directly evaporating the filtrate. The fluorobenzene layer is purified through the fluorobenzene dehydration tower and can be recycled. The acidic organic wastewater layer containing aluminum ions removes the residual fluorobenzene in the aqueous phase through the de - organic tower and recovers the fluorobenzene. The 1,4 - bis(4 - fluorobenzoyl)benzene is filtered off through the ceramic membrane filter to avoid co - precipitation with crystalline aluminum chloride in the subsequent process, which affects the crystal purity. Then, evaporation and crystallization are carried out to precipitate aluminum chloride hexahydrate. While obtaining aluminum chloride hexahydrate, the organic matter fluorobenzene in the reaction process is recycled, and there is no wastewater or waste salt discharge in the production process.

[0017] 2. This invention uses sublimation crystallization instead of solution crystallization to purify 1,4 - bis(4 - fluorobenzoyl)benzene. Utilizing the characteristics that the molecular structure of 1,4 - bis(4 - fluorobenzoyl)benzene is symmetric and easy to sublimate, sublimation crystallization can be used to efficiently separate 1,4 - bis(4 - fluorobenzoyl)benzene from 1,2 - bis(4 - fluorobenzoyl)benzene. While obtaining 1,4 - bis(4 - fluorobenzoyl)benzene with high purity, a large amount of waste organic solvents are not generated, there is no need to recover the waste solvents, the energy consumption is low, and the purity of 1,4 - bis(4 - fluorobenzoyl)benzene is greater than or equal to 99.81%. Description of the Drawings

[0018] Figure 1It is a flow chart of a low-cost and environmentally friendly process for producing 1,4-bis(4-fluorobenzoyl)benzene. Detailed implementation mode

[0019] For the convenience of those skilled in the art to understand, the present invention will be further described below in conjunction with specific embodiments.

[0020] As Figure 1 shown, a low-cost and environmentally friendly process for producing 1,4-bis(4-fluorobenzoyl)benzene includes the following steps: Step 1: Using fluorobenzene as a solvent, fluorobenzene and terephthaloyl chloride are subjected to a Friedel-Craft reaction under the catalysis of anhydrous aluminum chloride to synthesize 1,4-bis(4-fluorobenzoyl)benzene. After the reaction is completed, the reaction mixture is dropped into a washing kettle filled with a washing solvent to quench the reaction to obtain a quenched mixture. Step 2: The quenched mixture in Step 1 is pumped into a centrifugal filtration unit I for solid-liquid separation to obtain a filter cake and a filtrate. The filter cake is the crude product 1,4-bis(4-fluorobenzoyl)benzene. Step 3: The filter cake in Step 2 is added to a sublimation crystallization device, and 1,4-bis(4-fluorobenzoyl)benzene is purified in the sublimation crystallization device to remove the isomer 1,2-bis(4-fluorobenzoyl)benzene and other heavy component impurities. The sublimation crystallization device includes a sublimation kettle, a primary crystallization tank, and a secondary crystallization tank connected in sequence. Since the crude product of 1,2-bis(4-fluorobenzoyl)benzene not only contains the isomer 1,2-bis(4-fluorobenzoyl)benzene and other heavy component impurities, but also contains trace low-boiling substances such as fluorobenzene, the present invention controls the temperature of the sublimation kettle in Step 3 to be 200-280 °C, so that the crude product 1,4-bis(4-fluorobenzoyl)benzene in Step 2 enters the sublimation kettle for heating, sublimes into a gas state and separates from the heavy components such as the isomer 1,2-bis(4-fluorobenzoyl)benzene. Control the temperature of the primary crystallization tank to be 150-190 °C, control the temperature of the secondary crystallization tank to be 10-40 °C, and the gas of 1,4-bis(4-fluorobenzoyl)benzene enters the primary crystallization tank for cooling and crystallization. The purification of 1,4-bis(4-fluorobenzoyl)benzene is completed with low energy consumption, and the purity of 1,4-bis(4-fluorobenzoyl)benzene is greater than or equal to 99.81%. Utilizing the different physical properties of trace low-boiling substances such as fluorobenzene and 1,4-bis(4-fluorobenzoyl)benzene, the separation of trace low-boiling substances such as fluorobenzene and 1,4-bis(4-fluorobenzoyl)benzene is realized. The trace low-boiling substances such as fluorobenzene can enter the secondary crystallization tank in a gaseous state for condensation, realizing the recovery of reaction raw materials.

[0021] Step 4: Pump the filtrate in Step 2 into an inclined plate separator. The filtrate is allowed to stand and separate under the action of gravity. The upper layer is the fluorobenzene layer, and the lower layer is the acidic organic wastewater layer containing aluminum ions (the acidic organic wastewater layer containing aluminum ions contains trace amounts of fluorobenzene and trace amounts of 1,4-bis(4-fluorobenzoyl)benzene). The fluorobenzene layer is fed into a fluorobenzene dehydration tower for rectification and dehydration, and then enters the fluorobenzene raw material tank for recycling. Step 5: The acidic organic wastewater layer containing aluminum ions in Step 4 enters a ceramic membrane filter to filter 1,4-bis(4-fluorobenzoyl)benzene. After filtration, the aqueous phase enters a de-organic tower to remove fluorobenzene. The aqueous phase containing aluminum chloride at the bottom of the de-organic tower enters an evaporator to remove a certain amount of water, and then crystallizes in a DTB crystallizer, and crystalline aluminum chloride is obtained by centrifugation.

[0022] Specifically, the synthesis of 1,4-bis(4-fluorobenzoyl)benzene includes the following steps: Under inert conditions, anhydrous aluminum chloride and fluorobenzene are added to a reaction vessel. Terephthaloyl chloride is continuously added dropwise or intermittently to the reaction vessel. The dropping time is 30 - 120 min, the reaction temperature is 5 - 50 °C, the reaction time is 4 - 16 h, and the reaction pressure is 1.0 - 1.2 atm. The molar ratio of fluorobenzene to terephthaloyl chloride is 20:1 - 5:1, and the molar ratio of terephthaloyl chloride to anhydrous aluminum chloride is 1:2 - 1:4.

[0023] In Step 1, the washing solvent used in the washing kettle is an acidic aqueous solution, and the mass ratio of the washing solvent to the reaction mixture is 0.5:1 - 4:1. Specifically, the acidic aqueous solution is hydrochloric acid, preferably a hydrochloric acid solution with a mass fraction of 3% - 10%. The residence time of the reaction mixture in the washing kettle is 0.3 - 1 h, the temperature in the washing kettle is 0 - 73 °C, and the pressure in the washing kettle is 1 - 1.5 atm.

[0024] In Step 4, the residence time of the filtrate in the inclined plate separator is 0.3 - 1 h, and the temperature of the inclined plate separator is 0 - 45 °C. The fluorobenzene layer is fed into the top of the fluorobenzene dehydration tower. The number of plates in the fluorobenzene dehydration tower is 40 - 60. The pressure inside the fluorobenzene dehydration tower is 1 atm. The top temperature of the fluorobenzene dehydration tower is 73 - 85 °C, and the bottom temperature of the fluorobenzene dehydration tower is 85 - 90 °C. The overhead material (water) enters the intermediate tank at the top of the fluorobenzene dehydration tower for temporary storage and can be sent to the washing kettle for recycling the water. The side draw plate is preferably the 38th - 58th plate. The side draw material (fluorobenzene) enters the fluorobenzene raw material tank, and the bottom draw material enters the residue tank.

[0025] In step 5, the precision of the ceramic membrane filter is 10 - 20 μm. The filtered aqueous phase feeds from the bottom of the de - organic tower. The number of trays of the de - organic tower is 40 - 60, and the reflux ratio is 3 - 8. The pressure at the top of the de - organic tower is 1 atm, the temperature at the top of the de - organic tower is 73 - 98 °C, and the temperature at the bottom of the de - organic tower is 105 - 120 °C. Specifically, the material at the top of the de - organic tower (fluorobenzene) enters the de - organic intermediate tank, and after being temporarily stored in the de - organic intermediate tank, it enters the fluorobenzene raw material tank to realize the recycling of fluorobenzene. The material containing aluminum chloride at the bottom of the de - organic tower enters the evaporator. The temperature of the evaporator is 65 - 85 °C, and the pressure is 5 - 15 kPa. After removing part of the water in the evaporator, it enters the DTB crystallizer for crystallization. The temperature of the DTB crystallizer is 55 - 75 °C, and the pressure is 1 - 10 kPa. The mixture in the DTB crystallizer is centrifuged and filtered by the second centrifugal filtration unit to obtain the finished product of crystalline aluminum chloride, and the mother liquor is recycled to the evaporator. The water removed by the evaporator and the DTB crystallizer enters the condensate intermediate tank for temporary storage. The water in the condensate intermediate tank and dilute hydrochloric acid with a certain mass fraction are sent to the washing kettle as the washing solvent to realize the recycling of de - ionized water.

[0026] After the reaction quenching of the present invention, the 1,4 - bis(4 - fluorobenzoyl)benzene product and the filtrate are obtained through solid - liquid separation. The crude 1,4 - bis(4 - fluorobenzoyl)benzene is purified by sublimation crystallization instead of solution crystallization to efficiently remove isomeric impurities, obtain high - purity 1,4 - bis(4 - fluorobenzoyl)benzene without generating waste solvents. The filtrate is subjected to a layering treatment, and the organic phase and the aqueous phase are separately separated and purified. All the obtained materials are recycled, and at the same time, crystalline aluminum chloride is produced as a by - product. The device does not generate waste water and waste salts, and the process is environmentally friendly.

[0027] In summary, the present invention realizes a process for the low - cost and environmentally friendly production of 1,4 - bis(4 - fluorobenzoyl)benzene. This process does not generate waste salts, waste water, and waste solvents, and high - purity 1,4 - bis(4 - fluorobenzoyl)benzene can be obtained through sublimation crystallization. The specific embodiments are as follows Example 1

[0028] Step 1, add 2364 kg of fluorobenzene to a glass - lined reactor with a volume of 5 m 3 ³. After standing for 15 min, start stirring. Add 786 kg of anhydrous aluminum trichloride to the glass - lined reactor. After the catalyst is added, slowly drop 390 kg of terephthaloyl chloride into the reactor over 60 min. While dropping, start the circulating cold salt of the glass - lined reactor, control the temperature of the glass - lined reactor at 35 °C, the pressure at 1 - 1.2 atm, and the reaction time at 4 h; After the reaction is completed, the reaction mixture in the glass-lined reactor is added to a washing kettle containing 2500 kg of dilute hydrochloric acid solution (mass fraction of hydrogen chloride is 5%). The temperature in the washing kettle is 50 °C, and it stays for 1 h to quench the reaction, obtaining a quenched mixture; Step 2: Centrifuge and filter the quenched mixture for solid-liquid separation to obtain a filter cake and a filtrate. The filter cake is the crude product 1,4-bis(4-fluorobenzoyl)benzene; Step 3: Add the filter cake from Step 2 into a sublimation kettle. The sublimation crystallization is carried out in batch operation. The temperature of the sublimation kettle is controlled at 200 °C. The gas phase obtained from the sublimation kettle enters the first-stage crystallization tank. The temperature of the first-stage crystallization tank is 180 °C. The gas phase of 1,4-bis(4-fluorobenzoyl)benzene crystallizes in the first-stage crystallization tank. The uncondensed gas phase such as fluorobenzene that does not condense in the first-stage crystallization tank enters the second-stage crystallization tank for condensation. The temperature of the second-stage crystallization tank is 30 °C. After completion, 715 kg of 1,4-bis(4-fluorobenzoyl)benzene product is obtained in the first-stage crystallization tank, and the product purity is 99.88%. The 1,2-bis(4-fluorobenzoyl)benzene accumulated in the sublimation kettle is collected into a by-product tank for other uses; Step 4: Pump the filtrate from Step 2 into an inclined plate separator. The temperature in the inclined plate separator is 45 °C, and the residence time of the filtrate in the inclined plate separator is 0.4 h. The filtrate is allowed to stand and separate into a fluorobenzene layer and an acidic organic wastewater layer containing aluminum ions. The fluorobenzene layer material enters the fluorobenzene dehydration tower. The number of trays in the fluorobenzene dehydration tower is 50, the reflux ratio is 15, the top temperature is 73 °C, and the bottom temperature is 85 °C. The overhead material of the fluorobenzene dehydration tower enters the overhead intermediate tank for temporary storage and then is recycled to the washing kettle. The side-draw material fluorobenzene enters the fluorobenzene raw material tank, and the water content in the fluorobenzene is 100 ppm. The bottom material of the tower is treated as hazardous waste; Step 5: The material of the acidic organic wastewater layer containing aluminum ions from Step 4 enters the de-organic tower through a ceramic membrane filter (10 μm). The number of trays in the de-organic tower is 60, the reflux ratio is 5, the top temperature is 88 °C, the bottom temperature is 107 °C, and the top pressure is 1 atm. The fluorobenzene at the top of the de-organic tower enters the de-organic intermediate tank for temporary storage. The solution containing crystalline aluminum chloride at the bottom of the tower enters an evaporator to remove water, and the fluorobenzene content in the bottom of the tower is less than 0.01%. The pressure of the evaporator is 15 kPa, and the temperature of the evaporator is 81 °C. The water phase at the top of the evaporator enters the condensate intermediate tank and then is recycled to the washing kettle. The evaporator concentrates the crystalline aluminum chloride solution to 50 - 55 wt% and then transfers the material to a DTB crystallizer. The pressure of the DTB crystallizer is 10 kPa, and the temperature is 72 °C. The product discharged from the DTB crystallizer is filtered by a centrifuge to obtain crystalline aluminum chloride, and the mother liquor is recycled to the evaporator. The purity of the crystalline aluminum chloride in the product is 96.68%, and the collected mass is 1295 kg. Example 2

[0029] Step 1: Add to a volume of 5 m 3Add 2837 kg of fluorobenzene to the glass-lined reactor, and start stirring after standing for 15 min. Add 917 kg of anhydrous aluminum trichloride to the glass-lined reactor. After adding the catalyst, slowly add 500 kg of terephthaloyl chloride to the reactor dropwise over 30 min. While adding dropwise, start the circulating cold salt of the glass-lined reactor, control the temperature of the glass-lined reactor at 15 °C, the pressure at 1 - 1.2 atm, and the reaction time at 16 h; After the reaction is completed, add the reaction mixture in the glass-lined reactor to the washing kettle containing dilute hydrochloric acid solution (mass fraction of hydrogen chloride is 8%) in batches. The total amount of dilute hydrochloric acid used is 8.4 t. Control the temperature in the washing kettle at 70 °C and let it stay for 0.5 h for reaction quenching to obtain the quenched mixture; Step 2: Centrifuge and filter the quenched mixture for solid-liquid separation to obtain a filter cake and a filtrate. The filter cake is the crude product 1,4-bis(4-fluorobenzoyl)benzene; Step 3: Add the filter cake from Step 2 to the sublimation kettle. The sublimation crystallization method is an intermittent operation. Control the temperature of the sublimation kettle at 230 °C. The resulting gas phase enters the first-stage crystallization tank. The gas phase of 1,4-bis(4-fluorobenzoyl)benzene crystallizes in the first-stage crystallization tank. The temperature of the first-stage crystallization tank is 160 °C. The non-condensable gas phase such as fluorobenzene that is not condensed in the first-stage crystallization tank enters the second-stage crystallization tank for condensation. The temperature of the second-stage crystallization tank is 40 °C. After completion, 725 kg of 1,4-bis(4-fluorobenzoyl)benzene product with a product purity of 99.81% is obtained in the first-stage crystallization tank. The 1,2-bis(4-fluorobenzoyl)benzene accumulated in the sublimation kettle is collected in the by-product tank for other uses; Step 4: Pump the filtrate from Step 2 into the inclined plate separator. The temperature in the inclined plate separator is 30 °C. The filtrate stays in the inclined plate separator for 0.6 h. The filtrate is allowed to stand and separate into a fluorobenzene layer and an acidic organic wastewater layer containing aluminum ions. The fluorobenzene layer material enters the fluorobenzene dehydration tower. The number of trays in the fluorobenzene dehydration tower is 50, the reflux ratio is 25, the top temperature is 85 °C, and the bottom temperature is 87 °C. The overhead material of the fluorobenzene dehydration tower enters the overhead intermediate tank for temporary storage and then is recycled to the washing kettle. The side-stream extracted fluorobenzene enters the fluorobenzene raw material tank. The water content in the fluorobenzene is 80 ppm. The bottom material of the tower is treated as hazardous waste residue; Step 5, the material of the aluminum ion-containing acidic organic wastewater layer from Step 4 enters the de-organic tower through a ceramic membrane filter (10 μm). The de-organic tower has 60 trays, a reflux ratio of 3, a top temperature of 92 °C, a bottom temperature of 112 °C, and a top pressure of 1 atm. The fluorobenzene at the top of the de-organic tower enters the de-organic intermediate tank for temporary storage, and the solution containing crystalline aluminum chloride at the bottom of the tower enters the evaporator to remove water, with the fluorobenzene content in the bottom of the tower being less than 0.01%. The pressure of the evaporator is 10 kPa, and the temperature is 72 °C. The aqueous phase at the top of the evaporator enters the condensate intermediate tank and then is recycled to the washing kettle. After the evaporator concentrates the crystalline aluminum trichloride solution to 50 - 55 wt%, the material is transferred to a DTB crystallizer. The pressure of the DTB crystallizer is 8 kPa, and the temperature is 67 °C. The product discharged from the DTB crystallizer is filtered by a centrifuge to obtain crystalline aluminum chloride, and the mother liquor is recycled to the evaporator. The purity of crystalline aluminum chloride in the product is 97.23%, and 1512 kg of the product is collected. Example 3

[0030] Step 1, add 2648 kg of fluorobenzene to a glass-lined reactor with a volume of 5 m 3 . After standing for 15 min, start stirring. Add 733 kg of anhydrous aluminum trichloride to the glass-lined reactor. After adding the catalyst, slowly drop 280 kg of terephthaloyl chloride into the reactor over 120 min. While dropping, start the circulating cold salt in the glass-lined reactor, control the temperature of the glass-lined reactor at 5 °C, and the pressure at 1 - 1.2 atm. The reaction time is 16 h; After the reaction is completed, batchwise drop the reaction mixture in the glass-lined reactor into a washing kettle filled with a dilute hydrochloric acid solution (mass fraction of hydrogen chloride is 2%). The total amount of dilute hydrochloric acid used is 12817 kg. Control the temperature in the washing kettle at 10 °C and keep it for 0.3 h to quench the reaction to obtain a quenched mixture; Step 2, centrifuge and filter the quenched mixture for solid-liquid separation to obtain a filter cake and a filtrate. The filter cake is the crude product 1,4-bis(4-fluorobenzoyl)benzene; Step 3, add the filter cake from Step 2 to a sublimation kettle. The sublimation crystallization is carried out in batch operation. Control the temperature of the sublimation kettle at 250 °C. The resulting gas phase enters a primary crystallization tank, and the gas phase of 1,4-bis(4-fluorobenzoyl)benzene crystallizes in the primary crystallization tank. The temperature of the primary crystallization tank is 150 °C. The uncondensed gas phase such as fluorobenzene in the primary crystallization tank enters the secondary crystallization tank for condensation. The temperature of the secondary crystallization tank is 10 °C. After completion, 380 kg of 1,4-bis(4-fluorobenzoyl)benzene product is obtained in the primary crystallization tank, and the product purity is 99.89%. The 1,2-bis(4-fluorobenzoyl)benzene accumulated in the sublimation kettle is collected in the by-product tank for other uses; Step 4: Pump the filtrate from Step 2 into an inclined plate separator. The temperature inside the inclined plate separator is 10°C, and the residence time of the filtrate is 0.4 h. The filtrate is allowed to stand and separate into a fluorobenzene layer and an acidic organic wastewater layer containing aluminum ions. The fluorobenzene layer material enters the fluorobenzene dehydration tower. The number of trays in the fluorobenzene dehydration tower is 50, the reflux ratio is 10, the top temperature is 85°C, and the bottom temperature is 89°C. The overhead material of the fluorobenzene dehydration tower enters the overhead intermediate tank for temporary storage and then is recycled to the washing kettle. The side-draw fluorobenzene enters the fluorobenzene raw material tank, with the water content in the fluorobenzene being 76 ppm, and the bottom material is treated as hazardous waste residue; Step 5: The material of the acidic organic wastewater layer containing aluminum ions from Step 4 passes through a ceramic membrane filter (10 μm) and enters the de-organic tower. The number of trays in the de-organic tower is 60, the reflux ratio is 8, the top temperature is 98°C, the bottom temperature is 112°C, and the top pressure is 1 atm. The fluorobenzene at the top of the de-organic tower enters the de-organic intermediate tank for temporary storage, and the solution containing crystalline aluminum chloride at the bottom enters the evaporator to remove water, with the fluorobenzene content in the bottom being less than 0.01%. The pressure of the evaporator is 5 kPa, and the temperature is 65°C. The aqueous phase at the top of the evaporator enters the condensate intermediate tank and is then recycled to the washing kettle. The evaporator concentrates the crystalline aluminum trichloride solution to 50 - 55 wt%, and then the material is transferred to a DTB crystallizer. The pressure of the DTB crystallizer is 2 kPa, and the temperature is 63°C. The product discharged from the DTB crystallizer is filtered by a centrifuge to obtain crystalline aluminum chloride, and the mother liquor is recycled to the evaporator. The purity of the crystalline aluminum chloride in the product is 96.88%, and the collected mass is 2771 kg. Example 4

[0031] Step 1: Add 1891 kg of fluorobenzene to a glass-lined reactor with a volume of 5 m 3 . After standing for 15 min, start stirring. Add 1100 kg of anhydrous aluminum trichloride to the glass-lined reactor. After adding the catalyst, slowly drop 800 kg of terephthaloyl chloride into the reactor over 90 min. While dropping, start the circulating cold salt in the glass-lined reactor, control the temperature in the glass-lined reactor at 8°C, and the pressure at 1 - 1.2 atm. The reaction time is 12 h; After the reaction is completed, add the reaction mixture in the glass-lined reactor to a washing kettle containing a dilute hydrochloric acid solution (mass fraction of hydrogen chloride is 10%). The total amount of the dilute hydrochloric acid solution added to the washing kettle is 15169 kg. Control the temperature in the washing kettle at 5°C and let it stand for 0.8 h to quench the reaction, obtaining a quenched mixture; Step 2: Centrifuge and filter the quenched mixture for solid-liquid separation to obtain a filter cake and a filtrate. The filter cake is the crude product 1,4-bis(4-fluorobenzoyl)benzene; Step 3: Add the filter cake from Step 2 into the sublimation kettle. The sublimation crystallization is an intermittent operation. The temperature of the sublimation kettle is controlled at 280°C. The resulting gas phase enters the first-stage crystallization tank. The gas phase of 1,4-bis(4-fluorobenzoyl)benzene crystallizes in the first-stage crystallization tank, and the temperature of the first-stage crystallization tank is 190°C. The uncondensed non-condensable gas phase such as fluorobenzene in the first-stage crystallization tank enters the second-stage crystallization tank for condensation, and the temperature of the second-stage crystallization tank is 35°C. After completion, 1156 kg of 1,4-bis(4-fluorobenzoyl)benzene product is obtained in the first-stage crystallization tank, and the product purity is 99.83%. The 1,2-bis(4-fluorobenzoyl)benzene accumulated in the sublimation kettle is collected in the by-product tank for other uses; Step 4: Pump the filtrate from Step 2 into the inclined plate separator. The temperature in the inclined plate separator is 5°C, and the residence time of the filtrate in the inclined plate separator is 1 h. The filtrate is allowed to stand and separate into a fluorobenzene layer and an acidic organic wastewater layer containing aluminum ions. The fluorobenzene layer material enters the fluorobenzene dehydration tower. The number of trays in the fluorobenzene dehydration tower is 45, the reflux ratio is 22, the top temperature is 76°C, and the bottom temperature is 85°C. The overhead material of the fluorobenzene dehydration tower enters the overhead intermediate tank for temporary storage and then is recycled to the washing kettle. The side-draw fluorobenzene enters the fluorobenzene raw material tank, and the water content in the fluorobenzene is 69 ppm. The bottom material of the tower is treated as hazardous waste residue; Step 5: The material of the acidic organic wastewater layer containing aluminum ions from Step 4 enters the de-organic tower through a ceramic membrane filter (10 μm). The number of trays in the de-organic tower is 45, the reflux ratio is 15, the top temperature is 85°C, the bottom temperature is 110°C, and the top pressure is 1 atm. The fluorobenzene at the top of the de-organic tower enters the de-organic intermediate tank for temporary storage. The solution containing crystalline aluminum chloride at the bottom of the tower enters the evaporator to remove water, and the fluorobenzene content in the bottom of the tower is less than 0.01%. The pressure of the evaporator is 11 kPa, and the temperature of the evaporator is 74°C. The aqueous phase at the top of the evaporator enters the condensate intermediate tank and then is recycled to the washing kettle. The evaporator concentrates the crystalline aluminum trichloride solution to 50 - 55 wt%, and then the material is transferred to a DTB crystallizer. The pressure of the DTB crystallizer is 5 kPa, and the temperature is 62°C. The product discharged from the DTB crystallizer is filtered by a centrifuge to obtain crystalline aluminum chloride, and the mother liquor is recycled to the evaporator. The purity of the crystalline aluminum chloride in the product is 97.57%, and the collected mass is 1954 kg. Example 5

[0032] Step 1: Add 2979 kg of fluorobenzene into a glass-lined reactor with a volume of 5 m 3 and let it stand for 15 min, then start stirring. Add 880 kg of anhydrous aluminum trichloride into the glass-lined reactor. After adding the catalyst, slowly drop 420 kg of terephthaloyl chloride into the reactor over 45 min. While dropping, start the circulating cold salt in the glass-lined reactor, control the temperature of the glass-lined reactor at 50°C, the pressure at 1 - 1.2 atm, and the reaction time at 6 h; After the reaction is completed, the reaction mixture in the glass-lined reactor is added to the washing kettle containing a dilute hydrochloric acid solution (mass fraction of hydrogen chloride is 4.5%). The amount of dilute hydrochloric acid used is 8600 kg. The temperature in the washing kettle is controlled at 30 °C, and it stays for 1 h for reaction quenching to obtain a quenched mixture; Step 2: Centrifuge and filter the quenched mixture for solid-liquid separation to obtain a filter cake and a filtrate. The filter cake is the crude product 1,4-bis(4-fluorobenzoyl)benzene; Step 3: Add the filter cake from Step 2 into the sublimation kettle. The sublimation crystallization method is an intermittent operation. The temperature of the sublimation kettle is controlled at 240 °C. The resulting gas phase enters the first-stage crystallization tank. The gas phase of 1,4-bis(4-fluorobenzoyl)benzene crystallizes in the first-stage crystallization tank. The temperature of the first-stage crystallization tank is 170 °C. The non-condensable gas phase such as fluorobenzene that is not condensed in the first-stage crystallization tank enters the second-stage crystallization tank for cooling. The temperature of the second-stage crystallization tank is 23 °C. After completion, 589 kg of 1,4-bis(4-fluorobenzoyl)benzene product is obtained in the first-stage crystallization tank. The product purity is 99.84%. The 1,2-bis(4-fluorobenzoyl)benzene accumulated in the sublimation kettle is collected into the by-product tank for other uses; Step 4: Pump the filtrate from Step 2 into the inclined plate separator. The temperature in the inclined plate separator is 18 °C. The residence time of the filtrate in the inclined plate separator is 0.3 h. The filtrate is allowed to stand and separate into a fluorobenzene layer and an acidic organic wastewater layer containing aluminum ions. The fluorobenzene layer material enters the fluorobenzene dehydration tower. The number of trays in the fluorobenzene dehydration tower is 60, the reflux ratio is 15, the top temperature is 73 °C, and the bottom temperature is 85 °C. The overhead material of the fluorobenzene dehydration tower enters the overhead intermediate tank for temporary storage and then is recycled to the washing kettle. The side-draw material fluorobenzene enters the fluorobenzene raw material tank. The water content in the fluorobenzene is 92 ppm. The bottom material of the tower is treated as hazardous waste residue; Step 5: The material of the acidic organic wastewater layer containing aluminum ions from Step 4 enters the de-organic tower through a ceramic membrane filter (10 μm). The number of trays in the de-organic tower is 50, the reflux ratio is 12, the top temperature is 93 °C, the bottom temperature is 108 °C, and the top pressure is 1 atm. The fluorobenzene at the top of the de-organic tower enters the de-organic intermediate tank for temporary storage. The solution containing crystalline aluminum chloride at the bottom of the tower enters the evaporator to remove water. The fluorobenzene content in the bottom of the tower is less than 0.01%. The pressure of the evaporator is 10 kPa, and the temperature of the evaporator is 72 °C. The water phase at the top of the evaporator enters the condensate intermediate tank and then is recycled to the washing kettle. The evaporator concentrates the crystalline aluminum chloride solution to 50 - 55 wt% and then transfers the material to the DTB crystallizer. The pressure of the DTB crystallizer is 8 kPa, and the temperature is 68 °C. The discharge from the DTB crystallizer is filtered by a centrifuge to obtain crystalline aluminum chloride. The mother liquor is recycled to the evaporator. The purity of the crystalline aluminum chloride in the product is 98.19%, and the collected mass is 1573 kg.

[0033] It should be understood that the use of these embodiments is only for illustrating the present invention rather than intending to limit the protection scope of the present invention. In addition, it should also be understood that after reading the technical content of the present invention, those skilled in the art can make various changes, modifications and / or variations to the present invention, and all these equivalent forms also fall within the protection scope defined by the appended claims of this application.

Claims

1. A low-cost and environmentally friendly process for producing 1,4-di(4-fluorobenzoyl)benzene, characterized in that: The following steps are involved: Step 1, using fluorobenzene as solvent, fluorobenzene and terephthaloyl chloride are subjected to Friedel-Craft reaction under the catalysis of anhydrous aluminum chloride. After the reaction is completed, the reaction mixture enters a washing kettle for reaction quenching to obtain a quenched mixture; Step 2, centrifugally filtering the quenched mixture of step 1 to separate solid from liquid to obtain a filter cake and a filtrate, wherein the filter cake is a crude product 1,4-di(4-fluorobenzoyl)benzene; Step 3, adding the filter cake of step 2 to a sublimation crystallization device for sublimation crystallization to obtain purified 1,4-di(4-fluorobenzoyl)benzene, wherein the purity of the purified 1,4-di(4-fluorobenzoyl)benzene is greater than or equal to 99.81%; Step 4, pumping the filtrate in step 2 into an inclined plate stratifier for static stratification, wherein the upper layer is a fluorobenzene layer, and the lower layer is an acidic organic wastewater layer containing aluminum ions, and the fluorobenzene layer is passed into a fluorobenzene dehydration tower for dehydration and then enters a fluorobenzene raw material tank for recycling; Step 5, the aluminum ion-containing acidic organic wastewater layer of step 4 enters the ceramic membrane filter for filtration, and the water phase after filtration enters the de-organic tower, and the water phase of the de-organic tower kettle enters the evaporator for dehydration and the DTB crystallizer for crystallization in turn, and centrifuges to obtain crystalline aluminum chloride.

2. A low-cost and environmentally friendly process for producing 1,4-di(4-fluorobenzoyl)benzene according to claim 1, characterized in that: In step 1, when fluorobenzene reacts with terephthaloyl chloride, the reaction temperature is 5-50° C., the reaction pressure is 1-1.2 atm, and the reaction time is 4-16 h; The molar ratio of fluorobenzene to terephthaloyl chloride is 20:1-5:1, and the molar ratio of terephthaloyl chloride to anhydrous aluminum chloride is 1:2-1:

4.

3. A low-cost and environmentally friendly process for producing 1,4-di(4-fluorobenzoyl)benzene according to claim 1, characterized in that: The washing solvent used in the washing kettle in step 1 is an acidic aqueous solution, and the mass ratio of the washing solvent to the reaction mixture is 0.5:1-4:1; The acidic aqueous solution is hydrochloric acid; The residence time of the reaction mixture in the washing kettle is 0.3-1h, and the temperature in the washing kettle is 0-73°C.

4. A low-cost and environmentally friendly process for producing 1,4-di(4-fluorobenzoyl)benzene according to claim 1, characterized in that: The sublimation crystallization device in step 3 comprises a sublimation kettle, a primary crystallization tank, and a secondary crystallization tank which are connected in sequence.

5. A low-cost and environmentally friendly process for producing 1,4-di(4-fluorobenzoyl)benzene according to claim 4, characterized in that: The temperature of the sublimation kettle is controlled at 200-280°C; The temperature of the primary crystallization tank is controlled at 150-190°C; The temperature of the secondary crystallization tank is controlled at 10-40°C.

6. A low-cost and environmentally friendly process for producing 1,4-di(4-fluorobenzoyl)benzene according to claim 1, characterized in that: In step 4, the residence time of the filtrate in the inclined plate separator is 0.3-1h, and the temperature of the inclined plate separator is 0-45°C.

7. A low-cost and environmentally friendly process for producing 1,4-di(4-fluorobenzoyl)benzene according to claim 1, characterized in that: The number of plates of the fluorobenzene dehydration tower in step 4 is 40-60, the pressure in the fluorobenzene dehydration tower is 1 atm, the top temperature of the fluorobenzene dehydration tower is 73-85°C, and the bottom temperature of the fluorobenzene dehydration tower is 85-90°C.

8. A low-cost and environmentally friendly process for producing 1,4-di(4-fluorobenzoyl)benzene according to claim 1, characterized in that: In step 5, the precision of the ceramic membrane filter is 10-20 μm, the number of plates of the deorganic tower is 40-60, the top pressure of the deorganic tower is 1 atm, the top temperature of the deorganic tower is 73-98° C., and the kettle temperature of the deorganic tower is 105-120° C.

9. A low-cost and environmentally friendly process for producing 1,4-di(4-fluorobenzoyl)benzene according to claim 1, characterized in that: In step 5, the temperature of the evaporator is 65-85°C and the pressure is 5-15 kPa.

10. A low-cost and environmentally friendly process for producing 1,4-di(4-fluorobenzoyl)benzene according to claim 1, characterized in that: In step 5, the temperature of the DTB crystallizer is 55-75°C and the pressure is 1-10 kPa.

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