A process for producing 1,4-bis(4-fluorobenzoyl)benzene

Abstract

The invention discloses a low-cost and environmentally friendly process for producing 1,4-bis(4-fluorobenzoyl)benzene, belonging to the technical field of Friedel-Craft reactions. Fluorobenzene and terephthaloyl chloride react to generate 1,4-bis(4-fluorobenzoyl)benzene, and after quenching the reaction, crude 1,4-bis(4-fluorobenzoyl)benzene and a filtrate are obtained by filtration. The 1,4-bis(4-fluorobenzoyl)benzene is purified by sublimation crystallization. The filtrate is allowed to stand in an inclined plate separator for separation, and an oil layer and a water layer are treated separately. The fluorobenzene layer enters a dehydration tower for dehydration, and the fluorobenzene is then recycled. The aqueous phase is first subjected to a treatment for removing organic matter, and the obtained organic material enters a fluorobenzene recovery device for recycling. The obtained aqueous phase produces crystalline aluminum chloride as a by-product in an evaporation crystallization device. This process uses sublimation crystallization rather than solution crystallization to produce 1,4-bis(4-fluorobenzoyl)benzene, which does not produce waste solvents and does not require waste solvent recovery, resulting in low costs. The wastewater is treated for organic matter removal and evaporation crystallization, and the organic matter is recycled. Crystallized aluminum chloride is produced as a by-product, and no wastewater or waste salt is discharged.

Description

Technical Field

[0001] The present invention relates to the technical field of Friedel-Craft reactions, and in particular to a process for producing 1,4-di(4-fluorobenzoyl)benzene in a low-cost and environmentally friendly manner. Background Art

[0002] 1,4-bis(4-fluorobenzoyl)benzene is an important chemical intermediate with the molecular formula C 20 H 12 F2O2 has a molecular weight of 322 and a melting point of 220°C-222°C. Solubility: Insoluble in water, DMAC, acetone, and other organic solvents at room temperature. 1,4-Bis(4-fluorobenzoyl)benzene monomer can be used to produce PEAK series plastics, including PEEK and PEKK. Compared to traditional DFBP (difluorobenzophenone), PEAK series plastics made with 1,4-bis(4-fluorobenzoyl)benzene exhibit varying degrees of improvement in mechanical properties and heat resistance.

[0003] In existing technologies, 1,4-bis(4-fluorobenzoyl)benzene is mostly synthesized using terephthaloyl chloride and excess fluorobenzene in the presence of anhydrous aluminum chloride as a catalyst. After 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. These methods are described in patents such as US5300693A, US4820791A, DE3531837A1, and CN115135691A. Not only does the aluminum chloride quenching process generate a large amount of wastewater, but the solution crystallization process is also ineffective in removing 1,2-bis(4-fluorobenzoyl)benzene. Multiple crystallizations are required, resulting in large amounts of waste solvent and high energy consumption for solvent recovery. This hinders the industrial production of 1,4-bis(4-fluorobenzoyl)benzene.

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

[0005] To address the problems existing in the prior art, the present invention provides a low-cost and environmentally friendly process for producing 1,4-bis(4-fluorobenzoyl)benzene. The process uses an evaporation crystallization process to treat organic wastewater, recycles the organic matter and water, and produces crystalline aluminum chloride as a by-product. The crude 1,4-bis(4-fluorobenzoyl)benzene is purified by sublimation crystallization to remove isomers without generating waste solvents.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a low-cost and environmentally friendly process for producing 1,4-di(4-fluorobenzoyl)benzene, comprising the following steps:

[0007] 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. After the reaction is completed, the reaction mixture is placed in a washing kettle for reaction quenching to obtain a quenched mixture;

[0008] Step 2, performing solid-liquid separation on the quenched mixture of step 1 in a centrifugal filtration unit 1 to obtain a filter cake and a filtrate, wherein the filter cake is a crude product 1,4-di(4-fluorobenzoyl)benzene;

[0009] Step 3: adding the filter cake from step 2 to a sublimation crystallization device for 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%;

[0010] Step 4: pump the filtrate in step 2 into a slanted plate separator and let it stand for stratification. The upper layer is a fluorobenzene layer, and the lower layer is an acidic organic wastewater layer containing aluminum ions. The fluorobenzene layer is passed into a fluorobenzene dehydration tower for dehydration and then enters a fluorobenzene raw material tank for recycling;

[0011] In step 5, the aluminum ion-containing acidic organic wastewater layer in step 4 enters a ceramic membrane filter for filtration, and the filtered aqueous phase enters a dehydration tower. The aqueous phase in the dehydration tower kettle sequentially enters an evaporator for dehydration and a DTB crystallizer for crystallization, and is centrifuged to obtain crystalline aluminum chloride.

[0012] Preferably, when fluorobenzene and terephthaloyl chloride react 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;

[0013] The molar ratio of the fluorobenzene to terephthaloyl chloride is 20:1-5:1, and the molar ratio of the terephthaloyl chloride to anhydrous aluminum chloride is 1:2-1:4.

[0014] Preferably, the washing solvent used in the washing tank 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;

[0015] The acidic aqueous solution is hydrochloric acid;

[0016] The residence time of the reaction mixture in the washing tank is 0.3-1 h, and the temperature in the washing tank is 0-73°C.

[0017] Preferably, the sublimation crystallization device comprises a sublimation kettle, a primary crystallization tank, and a secondary crystallization tank connected in sequence.

[0018] Preferably, the temperature of the sublimation kettle is controlled at 200-280°C, and the temperature of the primary crystallization tank is controlled at 150-190°C;

[0019] The temperature of the secondary crystallization tank is controlled at 10-40°C.

[0020] Preferably, 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.

[0021] Preferably, 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.

[0022] Preferably, the precision of the ceramic membrane filter in step 5 is 10-20 μm, the number of plates of the degassing tower is 40-60, the top pressure of the degassing tower is 1 atm, the top temperature of the degassing tower is 73-98° C., and the bottom temperature of the degassing tower is 105-120° C.

[0023] Preferably, the temperature of the evaporator in step 5 is 65-85° C. and the pressure is 5-15 kPa.

[0024] Preferably, the temperature of the DTB crystallizer in step 5 is 55-75° C. and the pressure is 1-10 kPa.

[0025] The invention is beneficial in that:

[0026] 1. The present invention obtains 1,4-di(4-fluorobenzoyl)benzene and a filtrate through solid-liquid separation after synthesizing 1,4-di(4-fluorobenzoyl)benzene. The filtrate is allowed to stand for separation to obtain a fluorobenzene layer and an aluminum ion-containing acidic organic wastewater layer, which are post-treated separately to reduce the difficulty and processing volume of directly evaporating the filtrate. The fluorobenzene layer is purified by passing through a fluorobenzene dehydration tower so as to be recycled. The aluminum ion-containing acidic organic wastewater layer is passed through a de-organic tower to remove fluorobenzene remaining in the aqueous phase and recover the fluorobenzene. The 1,4-di(4-fluorobenzoyl)benzene is filtered out through a ceramic membrane filter to prevent subsequent precipitation with crystalline aluminum chloride and affect the purity of the crystals. Aluminum chloride hexahydrate is then evaporated and crystallized to precipitate. While obtaining aluminum chloride hexahydrate, the organic fluorobenzene produced in the reaction process is recycled and utilized. No wastewater or waste salt is discharged during the production process.

[0027] 2. The present invention uses sublimation crystallization rather than solution crystallization to purify 1,4-di(4-fluorobenzoyl)benzene. Utilizing the symmetrical molecular structure and easy sublimation of 1,4-di(4-fluorobenzoyl)benzene, sublimation crystallization can be used to efficiently separate 1,4-di(4-fluorobenzoyl)benzene from 1,2-di(4-fluorobenzoyl)benzene. While obtaining high-purity 1,4-di(4-fluorobenzoyl)benzene, a large amount of waste organic solvent is not generated, and there is no need to recover the waste solvent, resulting in low energy consumption. The purity of 1,4-di(4-fluorobenzoyl)benzene is greater than or equal to 99.81%. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The figure shows a flow chart of a low-cost and environmentally friendly process for producing 1,4-bis(4-fluorobenzoyl)benzene. DETAILED DESCRIPTION

[0029] To facilitate understanding by those skilled in the art, the present invention is further described below with reference to specific embodiments.

[0030] like Figure 1 As shown, a low-cost and environmentally friendly process for producing 1,4-bis(4-fluorobenzoyl)benzene comprises the following steps:

[0031] Step 1: Using fluorobenzene as a solvent, fluorobenzene and terephthaloyl chloride are subjected to a Friedel-Craft reaction in the presence of anhydrous aluminum chloride to synthesize 1,4-di(4-fluorobenzoyl)benzene. After the reaction is completed, the reaction mixture is dropwise added to a washing kettle containing a washing solvent to quench the reaction to obtain a quenched mixture.

[0032] Step 2: pumping the quenched mixture from step 1 into a centrifugal filtration unit 1 for solid-liquid separation to obtain a filter cake and a filtrate, wherein the filter cake is a crude product 1,4-di(4-fluorobenzoyl)benzene;

[0033] In step 3, the filter cake from step 2 is added to a sublimation crystallization apparatus, where 1,4-di(4-fluorobenzoyl)benzene is purified to remove the isomer 1,2-di(4-fluorobenzoyl)benzene and other heavy impurities. The sublimation crystallization apparatus includes a sublimation kettle, a primary crystallization tank, and a secondary crystallization tank connected in sequence.

[0034] Since the crude 1,2-di(4-fluorobenzoyl)benzene product contains not only the isomer 1,2-di(4-fluorobenzoyl)benzene and other heavy impurities, but also trace amounts of low-boiling substances such as fluorobenzene, the present invention controls the temperature of the sublimation kettle in step 3 to 200-280°C, allowing the crude 1,4-di(4-fluorobenzoyl)benzene product from step 2 to enter the sublimation kettle for heating, sublimating to a gaseous state, and then separating it from the isomer 1,2-di(4-fluorobenzoyl)benzene and other heavy components. The temperature of the primary crystallizer is controlled at 150-190°C, and the temperature of the secondary crystallizer is controlled at 10-40°C, allowing the 1,4-di(4-fluorobenzoyl)benzene gas to enter the primary crystallizer for cooling and crystallization. This completes the purification of 1,4-di(4-fluorobenzoyl)benzene with low energy consumption, achieving a purity of 1,4-di(4-fluorobenzoyl)benzene greater than or equal to 99.81%. By utilizing the different physical properties of trace low-boiling substances such as fluorobenzene and 1,4-di(4-fluorobenzoyl)benzene, the separation of trace low-boiling substances such as fluorobenzene and 1,4-di(4-fluorobenzoyl)benzene is achieved. Trace low-boiling substances such as fluorobenzene can enter the secondary crystallization tank in gaseous form for condensation, thereby realizing the recovery of reaction raw materials.

[0035] Step 4: Pump the filtrate from step 2 into an inclined plate separator, and the filtrate is allowed to stand and separate under gravity. The upper layer is a fluorobenzene layer, and the lower layer is an 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-di(4-fluorobenzoyl)benzene). The fluorobenzene layer is passed through a fluorobenzene dehydration tower for rectification and dehydration, and then enters a fluorobenzene raw material tank for recycling;

[0036] In step 5, the aluminum ion-containing acidic organic wastewater layer in step 4 enters a ceramic membrane filter to filter 1,4-di(4-fluorobenzoyl)benzene. After filtration, the aqueous phase enters a de-organic tower to remove fluorobenzene. The aqueous phase containing aluminum chloride in 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 centrifuges to obtain crystalline aluminum chloride.

[0037] Specifically, the synthesis of 1,4-bis(4-fluorobenzoyl)benzene includes the following steps: adding anhydrous aluminum chloride and fluorobenzene to a reaction vessel under inert conditions;

[0038] Terephthaloyl chloride is continuously or intermittently added dropwise to the reaction vessel, the addition 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;

[0039] 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.

[0040] The washing solvent used in the washing tank in step 1 is an acidic aqueous solution, with a mass ratio of washing solvent to reaction mixture of 0.5:1 to 4:1. Specifically, the acidic aqueous solution is hydrochloric acid, preferably a 3% to 10% hydrochloric acid solution. The reaction mixture is retained in the washing tank for 0.3 to 1 hour, the temperature in the washing tank is 0 to 73°C, and the pressure in the washing tank is 1 to 1.5 atm.

[0041] In step 4, the filtrate stays in the inclined plate separator for 0.3-1h, and the temperature of the inclined plate separator is 0-45°C. The fluorobenzene layer is fed from the top of the fluorobenzene dehydration tower, and the number of plates of the fluorobenzene dehydration tower is 40-60. The pressure in the fluorobenzene dehydration tower is 1atm, the temperature at the top of the fluorobenzene dehydration tower is 73-85°C, and the temperature of the bottom of the fluorobenzene dehydration tower is 85-90°C. The top 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 water recycling. The side line extraction plates are preferably 38-58, the side line extraction material (fluorobenzene) enters the fluorobenzene raw material tank, and the bottom extraction material enters the foot material tank.

[0042] The ceramic membrane filter in step 5 has a precision of 10-20 μm. The filtered aqueous phase is fed into the de-organization column kettle. The de-organization column has 40-60 trays and a reflux ratio of 3-8. The de-organization column overhead pressure is 1 atm, the de-organization column overhead temperature is 73-98°C, and the de-organization column kettle temperature is 105-120°C. Specifically, the de-organization column overhead material (fluorobenzene) enters the de-organization intermediate tank, where it is temporarily stored before entering the fluorobenzene feed tank for recycling. The de-organization column kettle material containing aluminum chloride enters the evaporator at a temperature of 65-85°C and a pressure of 5-15 kPa. After partial water removal in the evaporator, it enters the DTB crystallizer for crystallization. The DTB crystallizer temperature is 55-75°C and the pressure is 1-10 kPa. The mixture in the DTB crystallizer is filtered through a second centrifugal filtration unit to produce the finished crystalline aluminum chloride product, and the mother liquor is recycled to the evaporator. The water removed from the evaporator and DTB crystallizer enters the condensate intermediate tank for temporary storage. The water in the condensate intermediate tank is sent to the washing kettle together with a certain mass fraction of dilute hydrochloric acid as a washing solvent to realize the recycling of deionized water.

[0043] After the reaction is quenched, the present invention obtains a 1,4-di(4-fluorobenzoyl)benzene product and a filtrate through solid-liquid separation. The crude 1,4-di(4-fluorobenzoyl)benzene is purified by sublimation crystallization rather than solution crystallization, so as to efficiently remove isomer impurities and obtain high-purity 1,4-di(4-fluorobenzoyl)benzene without generating waste solvent. The filtrate is subjected to layering treatment, and the organic phase and the aqueous phase are separated and purified respectively. All the obtained materials are recycled, and crystalline aluminum chloride is produced as a by-product. The device does not generate wastewater and waste salt, and the process is environmentally friendly.

[0044] In summary, the present invention realizes a low-cost and environmentally friendly process for producing 1,4-bis(4-fluorobenzoyl)benzene. The process does not produce waste salt, wastewater, or waste solvent, and high-purity 1,4-bis(4-fluorobenzoyl)benzene can be obtained by sublimation crystallization.

[0045] The specific embodiments are as follows Example 1

[0046] Step 1: Add a volume of 5m 3 Add 2364kg of fluorobenzene to a glass-lined reactor and allow it to stand for 15 minutes before stirring. Add 786kg of anhydrous aluminum chloride to the glass-lined reactor. After the catalyst is added, slowly add 390kg of terephthaloyl chloride dropwise to the reactor over 60 minutes. While doing so, circulate cold salt through the glass-lined reactor. Maintain the temperature of the reactor at 35°C and the pressure at 1-1.2 atm for 4 hours.

[0047] After the reaction is completed, the reaction mixture in the glass-lined reactor is added to a washing kettle filled with 2500 kg of dilute hydrochloric acid solution (hydrogen chloride mass fraction is 5%), the temperature in the washing kettle is 50 ° C, and the mixture is kept for 1 hour to quench the reaction and obtain a quenched mixture;

[0048] Step 2: centrifugally filtering the quenched mixture for solid-liquid separation to obtain a filter cake and a filtrate, wherein the filter cake is a crude product 1,4-di(4-fluorobenzoyl)benzene;

[0049] In step 3, the filter cake from step 2 is added to a sublimation kettle. Sublimation crystallization is performed intermittently, and the temperature of the sublimation kettle is controlled at 200°C. The vapor phase obtained from the sublimation kettle enters a primary crystallizer at a temperature of 180°C. 1,4-bis(4-fluorobenzoyl)benzene vapor crystallizes in the primary crystallizer. Non-condensable gases such as fluorobenzene that do not condense in the primary crystallizer enter a secondary crystallizer for condensation, and the temperature of the secondary crystallizer is maintained at 30°C. Upon completion, 715 kg of 1,4-bis(4-fluorobenzoyl)benzene product is obtained in the primary crystallizer with a purity of 99.88%. The 1,2-bis(4-fluorobenzoyl)benzene accumulated in the sublimation kettle is collected in a by-product tank for other uses.

[0050] Step 4, pump the filtrate from step 2 into the inclined plate separator, the temperature in the inclined plate separator is 45°C, the residence time of the filtrate in the inclined plate separator is 0.4h, the filtrate is allowed to stand and separate to obtain a fluorobenzene layer and an acidic organic wastewater layer containing aluminum ions, the fluorobenzene layer material enters the fluorobenzene dehydration tower, the fluorobenzene dehydration tower has 50 plates, a reflux ratio of 15, a top temperature of 73°C, and a bottom temperature of 85°C. The top material of the fluorobenzene dehydration tower enters the middle tank at the top of the tower for temporary storage, and then is returned to the washing tank. The fluorobenzene material extracted from the side line enters the fluorobenzene raw material tank, the water content in fluorobenzene is 100ppm, and the bottom material is treated as hazardous waste;

[0051] In step 5, the aluminum ion-containing acidic organic wastewater layer from step 4 passes through a ceramic membrane filter (10μm) and enters the de-organization tower. The de-organization tower has 60 trays, a reflux ratio of 5, a top temperature of 88°C, a bottom temperature of 107°C, and a top pressure of 1 atm. Fluorobenzene at the top of the de-organization tower is temporarily stored in the de-organization intermediate tank, while the solution containing crystallized aluminum chloride in the bottom of the tower enters the evaporator for water removal. The fluorobenzene content in the bottom of the tower is less than 0.01%. The evaporator pressure is 15 kPa, and the evaporator temperature is 81°C. The water phase at the top of the evaporator enters the condensed water intermediate tank and then is recycled to the washing kettle. The evaporator concentrates the crystalline aluminum chloride solution to 50-55wt% and then transfers the material to the DTB crystallizer. The pressure of the DTB crystallizer is 10kPa and the temperature is 72℃. The discharge of the DTB crystallizer is filtered through 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 96.68%, and the collected mass is 1295kg. Example 2

[0052] Step 1: Add a volume of 5m 3 Add 2837kg of fluorobenzene to a glass-lined reactor and allow it to stand for 15 minutes before stirring. Add 917kg of anhydrous aluminum chloride to the reactor. After the catalyst is added, slowly add 500kg of terephthaloyl chloride dropwise to the reactor over a 30-minute dropwise addition period. While doing so, circulate cold salt through the reactor. Maintain the reactor temperature at 15°C and the pressure at 1-1.2 atm for 16 hours.

[0053] After the reaction is complete, the reaction mixture in the glass-lined reactor is added in batches to a washing kettle filled with dilute hydrochloric acid solution (hydrogen chloride mass fraction 8%). The total amount of dilute hydrochloric acid used is 8.4 tons. The temperature in the washing kettle is controlled at 70°C, and the reaction is quenched for 0.5 hours to obtain a quenched mixture.

[0054] Step 2: centrifugally filtering the quenched mixture for solid-liquid separation to obtain a filter cake and a filtrate, wherein the filter cake is a crude product 1,4-di(4-fluorobenzoyl)benzene;

[0055] In step 3, the filter cake from step 2 is added to a sublimation kettle. Sublimation crystallization is performed intermittently, and the temperature of the sublimation kettle is controlled at 230°C. The resulting vapor phase enters a primary crystallizer, where the 1,4-bis(4-fluorobenzoyl)benzene vapor phase crystallizes. The primary crystallizer is maintained at 160°C. Non-condensable gases such as fluorobenzene that do not condense in the primary crystallizer enter a secondary crystallizer, where they are condensed. The secondary crystallizer is maintained at 40°C. Upon completion, 725 kg of 1,4-bis(4-fluorobenzoyl)benzene product is obtained in the primary crystallizer with a purity of 99.81%. The accumulated 1,2-bis(4-fluorobenzoyl)benzene in the sublimation kettle is collected in a by-product tank for other uses.

[0056] Step 4, pump the filtrate of step 2 into the inclined plate separator, the temperature in the inclined plate separator is 30°C, the residence time of the filtrate in the inclined plate separator is 0.6h, the filtrate is allowed to stand and separate to obtain a fluorobenzene layer and an acidic organic wastewater layer containing aluminum ions, the fluorobenzene layer material enters the fluorobenzene dehydration tower, the fluorobenzene dehydration tower has 50 plates, a reflux ratio of 25, a top temperature of 85°C, and a bottom temperature of 87°C. The top material of the fluorobenzene dehydration tower enters the middle tank at the top of the tower for temporary storage, and then returns to the washing tank. The fluorobenzene material extracted from the side line enters the fluorobenzene raw material tank, the water content in fluorobenzene is 80ppm, and the bottom material is treated as hazardous waste;

[0057] In step 5, the aluminum ion-containing acidic organic wastewater layer from step 4 passes through a ceramic membrane filter (10μm) and enters the de-organization tower. The de-organization 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. Fluorobenzene at the top of the de-organization tower is temporarily stored in the de-organization intermediate tank, while the solution containing crystallized aluminum chloride in the bottom of the tower enters the evaporator for water removal. The fluorobenzene content in the bottom of the tower is less than 0.01%. The evaporator pressure is 10 kPa, and the evaporator temperature is 72°C. The water phase at the top of the evaporator enters the condensed water intermediate tank and then is recycled to the washing kettle. The evaporator concentrates the crystalline aluminum chloride solution to 50-55wt% and then the material is transferred to the DTB crystallizer. The pressure of the DTB crystallizer is 8kPa and the temperature is 67°C. The discharge of the DTB crystallizer is filtered through 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 97.23%, and the collected mass is 1512kg. Example 3

[0058] Step 1: Add a volume of 5m 3 Add 2648kg of fluorobenzene to a glass-lined reactor and allow it to stand for 15 minutes before stirring. Add 733kg of anhydrous aluminum chloride to the glass-lined reactor. After the catalyst is added, slowly add 280kg of terephthaloyl chloride dropwise to the reactor over 120 minutes. While doing so, circulate cold salt through the glass-lined reactor. Maintain the temperature at 5°C and the pressure at 1-1.2 atm for 16 hours.

[0059] After the reaction is completed, the reaction mixture in the glass-lined reactor is added dropwise in batches to a washing kettle filled with a dilute hydrochloric acid solution (hydrogen chloride mass fraction is 2%). The total amount of dilute hydrochloric acid used is 12817 kg. The temperature in the washing kettle is controlled at 10°C. The mixture is left for 0.3 h to quench the reaction and obtain a quenched mixture.

[0060] Step 2: centrifugally filtering the quenched mixture for solid-liquid separation to obtain a filter cake and a filtrate, wherein the filter cake is a crude product 1,4-di(4-fluorobenzoyl)benzene;

[0061] In step 3, the filter cake from step 2 is added to a sublimation kettle. The sublimation crystallization is performed intermittently. The temperature of the sublimation kettle is controlled at 250°C. The resulting vapor phase enters a primary crystallizer, where the 1,4-bis(4-fluorobenzoyl)benzene vapor phase crystallizes. The primary crystallizer is maintained at 150°C. Non-condensable gases such as fluorobenzene that have not condensed in the primary crystallizer enter a secondary crystallizer for condensation. The secondary crystallizer is maintained at 10°C. Upon completion, 380 kg of 1,4-bis(4-fluorobenzoyl)benzene product is obtained in the primary crystallizer with a purity of 99.89%. The accumulated 1,2-bis(4-fluorobenzoyl)benzene in the sublimation kettle is collected in a by-product tank for other uses.

[0062] Step 4, pump the filtrate from step 2 into the inclined plate separator, the temperature inside the inclined plate separator is 10°C, the residence time of the filtrate in the inclined plate separator is 0.4h, the filtrate is allowed to stand and separate to obtain a fluorobenzene layer and an acidic organic wastewater layer containing aluminum ions, the fluorobenzene layer material enters the fluorobenzene dehydration tower, the fluorobenzene dehydration tower has 50 plates, a reflux ratio of 10, a top temperature of 85°C, and a bottom temperature of 89°C. The top material of the fluorobenzene dehydration tower enters the middle tank at the top of the tower for temporary storage, and then is returned to the washing tank. The fluorobenzene material extracted from the side line enters the fluorobenzene raw material tank, the water content in fluorobenzene is 76ppm, and the bottom material is treated as hazardous waste;

[0063] In step 5, the aluminum ion-containing acidic organic wastewater layer from step 4 passes through a ceramic membrane filter (10μm) and enters the de-organization tower. The de-organization tower has 60 trays, a reflux ratio of 8, a top temperature of 98°C, a bottom temperature of 112°C, and a top pressure of 1 atm. Fluorobenzene at the top of the de-organization tower is temporarily stored in the de-organization intermediate tank, while the solution containing crystallized aluminum chloride in the bottom of the tower enters the evaporator for water removal. The fluorobenzene content in the bottom of the tower is less than 0.01%. The evaporator pressure is 5 kPa, and the evaporator temperature is 65°C. The water phase at the top of the evaporator enters the condensed water intermediate tank and then is recycled to the washing kettle. The evaporator concentrates the crystalline aluminum chloride solution to 50-55wt% and then transfers the material to the DTB crystallizer. The pressure of the DTB crystallizer is 2kPa and the temperature is 63°C. The discharge of the DTB crystallizer is filtered through 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 96.88%, and the collected mass is 2771kg. Example 4

[0064] Step 1: Add a volume of 5m 3 Add 1891 kg of fluorobenzene to a glass-lined reactor and allow it to stand for 15 minutes before stirring. Add 1100 kg of anhydrous aluminum chloride to the glass-lined reactor. After the catalyst is added, slowly add 800 kg of terephthaloyl chloride dropwise to the reactor over 90 minutes. While doing so, start circulating cold salt in the glass-lined reactor. Maintain the temperature of the reactor at 8°C and the pressure at 1-1.2 atm for 12 hours.

[0065] After the reaction is completed, the reaction mixture in the glass-lined reactor is added to a washing kettle filled with a dilute hydrochloric acid solution (with a mass fraction of hydrogen chloride of 10%). The total amount of dilute hydrochloric acid solution added to the washing kettle is 15169 kg. The temperature in the washing kettle is controlled at 5°C. The reaction is quenched for 0.8 h to obtain a quenched mixture.

[0066] Step 2: centrifugally filtering the quenched mixture for solid-liquid separation to obtain a filter cake and a filtrate, wherein the filter cake is a crude product 1,4-di(4-fluorobenzoyl)benzene;

[0067] In step 3, the filter cake from step 2 is added to a sublimation kettle. Sublimation crystallization is performed in an intermittent manner, with the kettle temperature controlled at 280°C. The resulting vapor phase enters a primary crystallizer, where the 1,4-bis(4-fluorobenzoyl)benzene vapor phase crystallizes at 190°C. Uncondensed fluorobenzene and other non-condensable vapors in the primary crystallizer enter a secondary crystallizer for condensation at 35°C. Upon completion, 1,156 kg of 1,4-bis(4-fluorobenzoyl)benzene product is obtained in the primary crystallizer with a purity of 99.83%. The accumulated 1,2-bis(4-fluorobenzoyl)benzene in the sublimation kettle is collected in a by-product tank for other uses.

[0068] Step 4, pump the filtrate from step 2 into the inclined plate separator, the temperature in the inclined plate separator is 5°C, the residence time of the filtrate in the inclined plate separator is 1h, the filtrate is allowed to stand and separate to obtain a fluorobenzene layer and an acidic organic wastewater layer containing aluminum ions, the fluorobenzene layer material enters the fluorobenzene dehydration tower, the fluorobenzene dehydration tower has 45 plates, a reflux ratio of 22, a top temperature of 76°C, and a bottom temperature of 85°C. The top material of the fluorobenzene dehydration tower enters the middle tank at the top of the tower for temporary storage, and then is returned to the washing tank. The fluorobenzene material extracted from the side line enters the fluorobenzene raw material tank, the water content in fluorobenzene is 69ppm, and the bottom material is treated as hazardous waste;

[0069] In step 5, the aluminum ion-containing acidic organic wastewater layer from step 4 passes through a ceramic membrane filter (10μm) and enters the de-organization tower. The de-organization tower has 45 trays, a reflux ratio of 15, a top temperature of 85°C, a bottom temperature of 110°C, and a top pressure of 1 atm. Fluorobenzene at the top of the de-organization tower is temporarily stored in the de-organization intermediate tank, while the solution containing crystallized aluminum chloride in the bottom of the tower enters the evaporator for water removal. The fluorobenzene content in the bottom of the tower is less than 0.01%. The evaporator pressure is 11 kPa, and the evaporator temperature is 74°C. The water phase at the top of the evaporator enters the condensed water intermediate tank and then returns to the washing kettle. The evaporator concentrates the crystalline aluminum chloride solution to 50-55wt% and then transfers the material to the DTB crystallizer. The pressure of the DTB crystallizer is 5kPa and the temperature is 62°C. The discharge of the DTB crystallizer is filtered through a centrifuge to obtain crystalline aluminum chloride. The mother liquor is returned to the evaporator. The purity of the crystalline aluminum chloride in the product is 97.57%, and the collected mass is 1954kg. Example 5

[0070] Step 1: Add a volume of 5m 3 Add 2979kg of fluorobenzene to a glass-lined reactor and allow it to stand for 15 minutes before stirring. Add 880kg of anhydrous aluminum chloride to the glass-lined reactor. After the catalyst is added, slowly add 420kg of terephthaloyl chloride dropwise to the reactor over 45 minutes. While doing so, circulate cold salt through the glass-lined reactor. Maintain the temperature at 50°C and the pressure at 1-1.2 atm for 6 hours.

[0071] After the reaction is completed, the reaction mixture in the glass-lined reactor is added to a washing kettle containing a dilute hydrochloric acid solution (with a mass fraction of hydrogen chloride of 4.5%). The amount of dilute hydrochloric acid used is 8600 kg. The temperature in the washing kettle is controlled at 30°C. The reaction is quenched for 1 hour to obtain a quenched mixture.

[0072] Step 2: centrifugally filtering the quenched mixture for solid-liquid separation to obtain a filter cake and a filtrate, wherein the filter cake is a crude product 1,4-di(4-fluorobenzoyl)benzene;

[0073] In step 3, the filter cake from step 2 is added to a sublimation kettle. The sublimation crystallization is performed intermittently. The temperature of the sublimation kettle is controlled at 240°C. The resulting vapor phase enters a primary crystallizer, where the 1,4-bis(4-fluorobenzoyl)benzene vapor phase crystallizes. The primary crystallizer is maintained at 170°C. Non-condensable vapors, such as fluorobenzene, that do not condense in the primary crystallizer enter a secondary crystallizer for cooling. The secondary crystallizer is maintained at 23°C. Upon completion, 589 kg of 1,4-bis(4-fluorobenzoyl)benzene product is obtained in the primary crystallizer with a purity of 99.84%. The 1,2-bis(4-fluorobenzoyl)benzene accumulated in the sublimation kettle is collected in a by-product tank for other uses.

[0074] Step 4, pump the filtrate of 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 0.3h, the filtrate is allowed to stand and separate to obtain a fluorobenzene layer and an acidic organic wastewater layer containing aluminum ions, the fluorobenzene layer material enters the fluorobenzene dehydration tower, the fluorobenzene dehydration tower has 60 plates, a reflux ratio of 15, a top temperature of 73°C, and a bottom temperature of 85°C. The top material of the fluorobenzene dehydration tower enters the middle tank at the top of the tower for temporary storage, and then returns to the washing tank. The fluorobenzene material extracted from the side line enters the fluorobenzene raw material tank, the water content of fluorobenzene is 92ppm, and the bottom material is treated as hazardous waste;

[0075] In step 5, the aluminum ion-containing acidic organic wastewater layer from step 4 passes through a ceramic membrane filter (10μm) and enters the de-organization tower. The de-organization tower has 50 trays, a reflux ratio of 12, a top temperature of 93°C, a bottom temperature of 108°C, and a top pressure of 1 atm. Fluorobenzene at the top of the de-organization tower is temporarily stored in the de-organization intermediate tank, while the solution containing crystallized aluminum chloride in the bottom of the tower enters the evaporator for water removal. The fluorobenzene content in the bottom of the tower is less than 0.01%. The evaporator pressure is 10 kPa, and the evaporator temperature is 72°C. The water phase at the top of the evaporator enters the condensed water intermediate tank and then is recycled to the washing kettle. The evaporator concentrates the crystalline aluminum chloride solution to 50-55wt% and then the material is transferred to the DTB crystallizer. The pressure of the DTB crystallizer is 8kPa and the temperature is 68°C. The discharge of the DTB crystallizer is filtered through 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 1573kg.

[0076] It should be understood that the purpose of these embodiments is only to illustrate the present invention and is not intended to limit the scope of protection 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 may make various changes, modifications and / or variations to the present invention, and all of these equivalent forms also fall within the scope of protection defined by the claims appended hereto.

Claims

1. A process for producing 1,4-bis(4-fluorobenzoyl)benzene, characterized in that: The following steps are involved: 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. After the reaction is completed, the reaction mixture is placed in a washing kettle for reaction quenching to obtain a quenched mixture; Step 2, centrifugally filtering the quenched mixture of step 1 to perform solid-liquid separation 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 from 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: pump the filtrate in step 2 into a slanted plate separator and let it stand for stratification. The upper layer is a fluorobenzene layer, and the lower layer is an acidic organic wastewater layer containing aluminum ions. 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 in step 4 enters a ceramic membrane filter for filtration, and the filtered aqueous phase enters a dehydration tower. The aqueous phase in the dehydration tower kettle sequentially enters an evaporator for dehydration and a DTB crystallizer for crystallization, and is centrifuged to obtain crystalline aluminum chloride; The sublimation crystallization device in step 3 includes a sublimation kettle, a primary crystallization tank, and a secondary crystallization tank connected in sequence.

2. A process for producing 1,4-bis(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 process for producing 1,4-bis(4-fluorobenzoyl)benzene according to claim 1, characterized in that: The washing solvent used in the washing tank 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 tank is 0.3-1 h, and the temperature in the washing tank is 0-73°C.

4. A process for producing 1,4-bis(4-fluorobenzoyl)benzene according to claim 1, 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.

5. A process for producing 1,4-bis(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.

6. A process for producing 1,4-bis(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.

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

8. A process for producing 1,4-bis(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.

9. The process for producing 1,4-bis(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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