A method for synthesizing 1,4-bis(4-fluorobenzoyl)benzene using ultrasonic wave

Abstract

The application discloses a method for synthesizing 1,4-di(4-fluorobenzoyl)benzene by using ultrasonic waves, and belongs to the technical field of Friedel-Craft reaction. In the method, trifluoromethanesulfonic acid compounds are used as catalysts, fluorobenzene and terephthaloyl chloride are catalyzed to synthesize 1,4-di(4-fluorobenzoyl)benzene under the action of ultrasonic waves; the trifluoromethanesulfonic acid compounds are selected from any one of Bi(OTf)3, La(OTf)3, Sn(OTf)2 and TfOH. In the method, trifluoromethanesulfonic acid compounds are used as catalysts, the catalysts are separated by filtering and rectifying, and a large amount of acidic waste liquid is avoided; meanwhile, the reaction time is shortened, the reaction yield is improved, and the production cost is reduced by combining with ultrasonic wave intensification.

Description

Technical Field

[0001] This invention relates to the field of Friedel-Craft reaction technology, and more specifically to a method for synthesizing 1,4-bis(4-fluorobenzoyl)benzene using ultrasound. Background Technology

[0002] 1,4-Di(4-fluorobenzoyl)benzene, with a melting point of 220-222℃, is the main monomer for synthesizing PEEK materials. PEAK series plastics made from 1,4-di(4-fluorobenzoyl)benzene have varying degrees of improvement in mechanical properties and heat resistance.

[0003] Currently, in industry, aluminum chloride is used to catalyze the synthesis of 1,4-bis(4-fluorobenzoyl)benzene from fluorobenzene and terephthaloyl chloride. After the reaction, the mixture is purified by water washing and quenching, filtration, and solution crystallization to obtain the product 1,4-bis(4-fluorobenzoyl)benzene. This method is simple and the raw materials are readily available, but the reaction time is long and the reaction efficiency is low. Furthermore, during the reaction, 1 mol of terephthaloyl chloride forms a complex with 2 mol of aluminum chloride, rendering the aluminum chloride in the complex structure ineffective as a catalyst. Therefore, producing 1 ton of 1,4-bis(4-fluorobenzoyl)benzene requires at least 0.9 tons of anhydrous aluminum chloride, resulting in a huge amount of catalyst used and the generation of a large amount of aluminum chloride wastewater, posing a significant environmental burden.

[0004] In view of the problems existing in the prior art, the present invention, combined with years of design and use experience in related fields, has designed a method for synthesizing 1,4-bis(4-fluorobenzoyl)benzene using ultrasound to overcome the above defects. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a method for synthesizing 1,4-bis(4-fluorobenzoyl)benzene using ultrasound. After the reaction, the catalyst is recovered by filtration and distillation of the aqueous phase, thus solving the environmental problem of acidic organic wastewater containing aluminum ions. Trifluoromethane sulfonic acid compounds are used as catalysts, and ultrasound is used to promote the diffusion of reactants. The two work synergistically to accelerate the reaction and obtain a high-purity, high-yield product.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a method for synthesizing 1,4-bis(4-fluorobenzoyl)benzene using ultrasound, wherein trifluoromethanesulfonic acid compounds are used as catalysts, and under the action of ultrasound, fluorobenzene and terephthaloyl chloride are catalyzed to synthesize 1,4-bis(4-fluorobenzoyl)benzene. The trifluoromethanesulfonic acid compound is selected from any one of Bi(OTf)3, La(OTf)3, Sn(OTf)2, and TfOH.

[0007] Preferably, the molar ratio of fluorobenzene to terephthaloyl chloride is (4:1) to (6:1).

[0008] Preferably, the mass ratio of the trifluoromethanesulfonic acid compound to terephthaloyl chloride is 0.005-0.02:1.

[0009] Preferably, it includes the following steps: Step 1: Add terephthaloyl chloride to the premix tank and melt it into the first liquid; A second liquid is prepared by mixing fluorobenzene with trifluoromethane sulfonic acid compounds at room temperature; Step 2: Using a feed pump, the first liquid and the second liquid are continuously added to the reactor for reaction, with an application intensity of 30-100 W / cm². 2 The ultrasonic waves, after the reaction is complete, are temporarily stored in an intermediate tank. Step 3: Post-process the material in the intermediate tank to obtain purified 1,4-bis(4-fluorobenzoyl)benzene.

[0010] Preferably, in step 2, the temperature of the reactor is 80-160℃, and the residence time of the reactants in the reactor is 0.2-0.5h.

[0011] Preferably, the reactor in step 2 is a tubular reactor with a length-to-diameter ratio greater than 100.

[0012] Preferably, the post-processing in step 3 includes the following steps: S1 filtration involves quenching the material in the intermediate tank with water to precipitate crude 1,4-bis(4-fluorobenzoyl)benzene. S2 material recovery, the filtrate is separated into fluorobenzene phase and aqueous phase, the fluorobenzene phase is purified by distillation to obtain fluorobenzene, and the aqueous phase is purified by distillation to obtain trifluoromethanesulfonate catalyst; S3 recrystallization, washing the crude product with water and crystallizing the solution yielded purified 1,4-bis(4-fluorobenzoyl)benzene.

[0013] Preferably, the mass ratio of material to water in the intermediate tank in step S1 is (1:1) to (1:3).

[0014] Preferably, in the water washing process of step S3, the mass ratio of crude product to water is (1:5) to (1:10).

[0015] Preferably, dipropyl carbonate is used for solution crystallization in step S3; The mass ratio of 1,4-bis(4-fluorobenzoyl)benzene to dipropyl carbonate is (1:8) to (1:20).

[0016] The advantages of this invention are: 1. This invention uses trifluoromethanesulfonic acid compounds as catalysts to catalyze the reaction of fluorobenzene and terephthaloyl chloride. After the reaction is complete, the catalyst can be recycled, avoiding the generation of a large amount of waste liquid. Since the fluorine atoms in fluorobenzene passivate the benzene ring, the yield is low when using trifluoromethanesulfonate catalysis alone. This invention also combines ultrasonic enhancement to reduce the activation energy of the reaction through cavitation, thereby accelerating the breaking of CH bonds during the reaction. The breaking of CH bonds is the rate-controlling step in the Friedel-Crafts acylation reaction. Therefore, it can improve the catalytic performance of trifluoromethanesulfonic acid catalysts for the Friedel-Crafts acylation of aromatic rings with passivating groups (such as fluorobenzene and chlorobenzene) on the benzene ring, and obtain a high yield of 1,4-bis(4-fluorobenzoyl)benzene.

[0017] 2. In this invention, a first liquid and a second liquid are introduced into a tubular reactor to continuously react and obtain 1,4-bis(4-fluorobenzoyl)benzene. This method is simple to operate, has high reaction efficiency, and the reaction process is controllable, thus realizing the continuous production of 1,4-bis(4-fluorobenzoyl)benzene. Attached Figure Description

[0018] Figure 1 This is a gas chromatogram of the product of Example 1 in this invention. Detailed Implementation

[0019] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to specific embodiments.

[0020] A method for synthesizing 1,4-bis(4-fluorobenzoyl)benzene using ultrasound includes the following steps: Step 1: Add terephthaloyl chloride to a premixing tank and heat it to melt it into a first liquid; at room temperature, mix fluorobenzene and trifluoromethane sulfonic acid compounds evenly to prepare a second liquid; wherein the trifluoromethane sulfonic acid compounds are selected from any one of Bi(OTf)3, La(OTf)3, Sn(OTf)2, and TfOH, the molar ratio of fluorobenzene to terephthaloyl chloride is (4:1)-(6:1), and the mass ratio of trifluoromethane sulfonic acid compounds to terephthaloyl chloride is 0.005-0.02:1; Step 2: Using a feed pump, the first liquid and the second liquid are continuously added to the tubular reactor for reaction, and ultrasound is applied with an intensity of 30-100 W / cm. 2 The temperature of the tubular reactor is 80-160℃, the residence time of the reactants in the reactor is 0.2-0.5h, the length-to-diameter ratio of the tubular reactor is greater than 100, and after the reaction is completed, the reactants are temporarily stored in an intermediate tank. An exhaust valve is installed at the top of the intermediate tank to discharge the generated hydrogen chloride gas into the tail gas recovery system. Step 3: The reaction system in the intermediate tank is post-processed to obtain purified 1,4-bis(4-fluorobenzoyl)benzene with a purity greater than 99.1% and a yield greater than 75.6%.

[0021] F (fluorine) is the most electronegative element in the periodic table, and its strong electron-withdrawing effect significantly reduces the electron cloud density of the benzene ring, making electrophilic Friedel-Crafts acylation reactions difficult to occur under normal circumstances. Therefore, the Friedel-Crafts acylation of fluorobenzene requires a highly acidic catalyst. Traditional anhydrous aluminum chloride exhibits high catalytic activity for acylation reactions due to its ability to form complexes with carbonyl groups. However, traditional aluminum trichloride catalysts require large quantities, generating significant wastewater and posing a heavy environmental burden. Trifluoromethanesulfonate catalysts show poor activity when catalyzing aromatic rings with passivating groups on the benzene ring, such as fluorobenzene and chlorobenzene. This invention uses trifluoromethanesulfonate compounds as catalysts, combined with ultrasonic enhancement. Through the cavitation and mechanical effects of ultrasound, the activation energy is lowered, accelerating the breaking of the CH bond during the reaction. The breaking of the CH bond is the rate-determining step in the Friedel-Crafts acylation reaction, thus significantly improving the catalytic performance of trifluoromethanesulfonate catalysts for the Friedel-Crafts acylation of fluorobenzene and reducing catalyst usage. Simultaneously, the ultrasonic mechanical effect enhances mass transfer within the reactor, shortens the reaction time, and increases the reaction yield. Furthermore, the thermal effect of ultrasound can induce cavitation, and the instantaneous vortex generated by cavitation can produce enormous explosive force and impact, and generate high pressure on the molecules of reactants, achieving high temperature and high pressure under microscopic conditions, which strengthens and accelerates the chemical reaction of substances. At the same time, ultrasound also has a supermixing effect, which promotes the diffusion of reactants, which is conducive to the formation and exposure of more reaction centers and accelerates the reaction. By using a tubular reactor as the reaction site, continuous and uninterrupted production can be achieved. Moreover, by limiting the specifications of the reactor and the residence time, this invention can achieve high purity and high recovery rate of the product with low catalyst addition.

[0022] This invention uses trifluoromethanesulfonic acid compounds as catalysts to catalyze the reaction of fluorobenzene and terephthaloyl chloride. After the reaction, water is added for quenching. The crude 1,4-bis(4-fluorobenzoyl)benzene and the filtrate are separated by filtration. The filtrate is allowed to stand and separate into an aqueous phase and a fluorobenzene phase. The trifluoromethanesulfonic acid compounds dissolve in the aqueous phase. The catalyst is recovered by distillation, avoiding the generation of acidic wastewater containing aluminum ions. This effectively solves the environmental problem of acidic organic wastewater containing aluminum ions. At the same time, the production process is continuous and simple, reducing production costs and facilitating the industrial production of 1,4-bis(4-fluorobenzoyl)benzene.

[0023] Specifically, the post-processing in step 3 includes the following steps: S1 filtration involves quenching the material in the intermediate tank with water and filtering to obtain crude 1,4-bis(4-fluorobenzoyl)benzene. The mass ratio of the material to water in the intermediate tank is (1:1) to (1:3). S2 material recovery, the filtrate is separated into fluorobenzene phase and aqueous phase, the fluorobenzene phase is purified by distillation to obtain fluorobenzene, and the aqueous phase is purified by distillation to obtain trifluoromethanesulfonate catalyst; S3 recrystallization, washing the crude product with water and crystallizing the solution yielded purified 1,4-bis(4-fluorobenzoyl)benzene.

[0024] In step S3, the mass ratio of crude product to water is (1:5)-(1:10), the water washing temperature is 80-100℃, and the water washing time is 1-2h. Dipropyl carbonate is used to crystallize the crude product solution, and the mass ratio of 1,4-bis(4-fluorobenzoyl)benzene to dipropyl carbonate is (1:8)-(1:20). Specific embodiments are as follows: Example 1

[0025] In this embodiment, the tubular reactor has a specification of φ20mm*15m; Step 1: Add terephthaloyl chloride to a premixing tank and heat to 90°C to melt it into the first liquid; At room temperature, fluorobenzene and Bi(OTf)3 were mixed evenly to prepare a second liquid, wherein the mass of Bi(OTf)3 was 0.01 times that of terephthaloyl chloride; Step 2: Using a feed pump, the first liquid and the second liquid are introduced into a tubular reactor. The reaction temperature is 80℃, and the flow rate of the mixed liquid in the reactor is 1 m / min. The feed rate of the first liquid is 237 mL / min, and the feed rate of the second liquid is 77 mL / min. The molar ratio of fluorobenzene to terephthaloyl chloride is 5:1. The reaction time is 15 min, and the ultrasonic intensity is 50 W / cm. 2 After the reaction is complete, the gas is added to the intermediate tank for temporary storage. The hydrogen chloride gas enters the tail gas recovery system through the exhaust valve at the top of the intermediate tank. Step 3: After the device is running stably, take 500g of the mixture in the intermediate tank, add 500g of water for quenching, and filter to obtain 251.0g of crude 1,4-bis(4-fluorobenzoyl)benzene; Material recovery, filtrate settling and separation, lower fluorobenzene phase being distilled at atmospheric pressure and 85℃ to obtain fluorobenzene, upper aqueous phase being evaporated in a distillation column to obtain Bi(OTf)3 catalyst, catalyst being dried in an oven, catalyst mass 1.45g. Recrystallization was performed, followed by washing the crude product with water at 80℃ for 1.5 hours, using 6 times the mass of the crude product. After washing, the product was filtered, and then dipropyl carbonate was added for crystallization. The mass ratio of crude product to dipropyl carbonate was 1:10. The purified 1,4-bis(4-fluorobenzoyl)benzene had a purity of 99.5% and a yield of 92.3%. Figure 1 As shown. Example 2

[0026] In this embodiment, the tubular reactor has a specification of φ20mm*15m; Step 1: Add terephthaloyl chloride to a premixing tank and heat to 90°C to melt it into the first liquid; At room temperature, fluorobenzene and La(OTf)3 were mixed evenly to prepare a second liquid, wherein the mass of La(OTf)3 was 0.005 of terephthaloyl chloride; Step 2: Using a feed pump, the first liquid and the second liquid are introduced into a tubular reactor. The reaction temperature is 100℃, and the flow rate of the mixed liquid in the reactor is 0.5 m / min. The feed rate of the first liquid is 124 mL / min, and the feed rate of the second liquid is 33 mL / min. The molar ratio of fluorobenzene to terephthaloyl chloride is 6:1. The residence time is 30 min, and the ultrasonic intensity is 100 W / cm. 2 After the reaction is complete, the gas is added to the intermediate tank for temporary storage. The hydrogen chloride gas enters the tail gas recovery system through the exhaust valve at the top of the intermediate tank. Step 3: After the device is running stably, take 500g of liquid from the intermediate tank and add 1000g of water for quenching. Filter to obtain 218g of crude 1,4-bis(4-fluorobenzoyl)benzene. Material recovery, filtrate settling and separation, lower fluorobenzene phase being distilled at atmospheric pressure and 85℃ to obtain fluorobenzene, upper aqueous phase being evaporated in a distillation column to obtain La(OTf)3 catalyst, catalyst being dried in an oven, catalyst mass being 0.58g; Recrystallization was performed, and the crude product was washed with water at 80℃ for 2 hours. The amount of water was 5 times the mass of the crude product. After washing, the product was filtered, and then dipropyl carbonate was added for crystallization. The mass ratio of crude product to dipropyl carbonate was 1:8. The purified 1,4-bis(4-fluorobenzoyl)benzene had a purity of 99.3% and a yield of 95.8%. Example 3

[0027] In this embodiment, the tubular reactor has a specification of φ20mm*15m; Step 1: Add terephthaloyl chloride to a premixing tank and heat to 90°C to melt it into the first liquid; At room temperature, fluorobenzene and Sn(OTf)2 were mixed evenly to prepare a second liquid, wherein the mass of Sn(OTf)2 was 0.02 times that of terephthaloyl chloride; Step 2: Using a feed pump, the first liquid and the second liquid are introduced into a tubular reactor. The reaction temperature is 160℃, the flow rate of the mixed liquid in the reactor is 0.7 m / min, the feed rate of the first liquid is 156 mL / min, the feed rate of the second liquid is 63 mL / min, the molar ratio of fluorobenzene to terephthaloyl chloride is 4:1, the residence time is 22 min, and the ultrasonic intensity is 40 W / cm.2 After the reaction is complete, the gas is added to the intermediate tank for temporary storage. The hydrogen chloride gas enters the tail gas recovery system through the exhaust valve at the top of the intermediate tank. Step 3: After the device is running stably, take 500g of liquid from the intermediate tank and add 1000g of water for quenching. Filter to obtain 262.1g of crude 1,4-bis(4-fluorobenzoyl)benzene. Material recovery, filtrate settling and separation, the lower fluorobenzene phase being distilled at atmospheric pressure and 85℃ to obtain fluorobenzene, the upper aqueous phase being evaporated in a distillation column to obtain Sn(OTf)2 catalyst, the catalyst being dried in an oven, the catalyst mass being 3.48g; Recrystallization was performed, and the crude product was washed with water at 100℃ for 1 hour, using 10 times the mass of the crude product. After washing, the product was filtered, and then dipropyl carbonate was added for crystallization. The mass ratio of crude product to dipropyl carbonate was 1:20. The purified 1,4-bis(4-fluorobenzoyl)benzene had a purity of 99.6% and a yield of 82.5%. Example 4

[0028] In this embodiment, the tubular reactor has a specification of φ20mm*15m; Step 1: Add terephthaloyl chloride to a premixing tank and heat to 90°C to melt it into the first liquid; At room temperature, fluorobenzene and TfOH are mixed evenly to prepare a second liquid, wherein the mass of TfOH is 0.005 of terephthaloyl chloride; Step 2: Using a feed pump, the first liquid and the second liquid are introduced into a tubular reactor. The reaction temperature is 100℃, the flow rate of the mixed liquid in the reactor is 1.25 m / min, the feed rate of the first liquid is 279 mL / min, the feed rate of the second liquid is 113 mL / min, the molar ratio of fluorobenzene to terephthaloyl chloride is 4:1, the residence time is 12 min, and the ultrasonic intensity is 40 W / cm². 2 After the reaction is complete, the gas is added to the intermediate tank for temporary storage. The hydrogen chloride gas enters the tail gas recovery system through the exhaust valve at the top of the intermediate tank. Step 3: After the device is running stably, take 500g of liquid from the intermediate tank and add 1000g of water for quenching. Filter to obtain 238.9g of crude 1,4-bis(4-fluorobenzoyl)benzene. Material recovery, filtrate settling and separation, the lower fluorobenzene phase being distilled at atmospheric pressure and 85℃ to obtain fluorobenzene, the upper aqueous phase being evaporated in a distillation column to obtain 0.92g of liquid TfOH catalyst; Recrystallization was performed, and the crude product was washed with water at 80℃ for 1.5 hours. The amount of water was 5 times the mass of the crude product. After washing, the product was filtered, and then dipropyl carbonate was added for crystallization. The mass ratio of crude product to dipropyl carbonate was 1:10. The purified 1,4-bis(4-fluorobenzoyl)benzene had a purity of 99.1% and a yield of 75.6%.

[0029] Comparative Example 1 Step 1: Add terephthaloyl chloride to a premixing tank and heat to 90°C to melt it into the first liquid; Step 2: Add 384g of fluorobenzene, 1.1g of TfOH, and 203g of the first liquid to the reaction vessel. The reaction time is 12min and the reaction temperature is 100℃. Step 3: After the reaction is complete, take the above liquid and add 1000g of water for quenching. Filter to obtain 143.2g of crude 1,4-bis(4-fluorobenzoyl)benzene. Let the filtrate stand to separate into layers. Distill the lower fluorobenzene phase at atmospheric pressure and 85℃ to obtain fluorobenzene. Evaporate the upper aqueous solution inside the distillation column to obtain 0.82g of TfOH catalyst. Recrystallization was performed, and the crude product was washed with water at 80℃ for 1.5 hours. The amount of water was 5 times the mass of the crude product. After washing, the product was filtered, and then dipropyl carbonate was added for crystallization. The mass ratio of crude product to dipropyl carbonate was 1:10. The purified 1,4-bis(4-fluorobenzoyl)benzene had a purity of 99.5% and a yield of 42.1%.

[0030] It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the invention. Furthermore, it should be understood that after reading the technical description of this invention, those skilled in the art can make various alterations, modifications, and / or variations to the invention, and all such equivalent forms also fall within the scope of protection defined by the appended claims.

Claims

1. A method for synthesizing 1,4-bis(4-fluorobenzoyl)benzene using ultrasound, characterized in that, Using trifluoromethanesulfonic acid compounds as catalysts, 1,4-bis(4-fluorobenzoyl)benzene was synthesized from fluorobenzene and terephthaloyl chloride under ultrasonic irradiation. The trifluoromethanesulfonic acid compound is selected from any one of Bi(OTf)3, La(OTf)3, Sn(OTf)2, and TfOH.

2. The method for synthesizing 1,4-bis(4-fluorobenzoyl)benzene using ultrasound according to claim 1, characterized in that, The molar ratio of fluorobenzene to terephthaloyl chloride is (4:1) to (6:1).

3. The method for synthesizing 1,4-bis(4-fluorobenzoyl)benzene using ultrasound according to claim 1, characterized in that, The mass ratio of the trifluoromethanesulfonic acid compound to terephthaloyl chloride is 0.005-0.02:

1.

4. The method for synthesizing 1,4-bis(4-fluorobenzoyl)benzene using ultrasound according to claim 1, characterized in that, Includes the following steps: Step 1: Add terephthaloyl chloride to the premix tank and melt it into the first liquid; A second liquid is prepared by mixing fluorobenzene with trifluoromethane sulfonic acid compounds at room temperature; Step 2: Using a feed pump, the first liquid and the second liquid are continuously added to the reactor for reaction, with an application intensity of 30-100 W / cm². 2 The ultrasonic waves, after the reaction is complete, are temporarily stored in an intermediate tank. Step 3: Post-process the material in the intermediate tank to obtain purified 1,4-bis(4-fluorobenzoyl)benzene.

5. The method for synthesizing 1,4-bis(4-fluorobenzoyl)benzene using ultrasound according to claim 4, characterized in that, In step 2, the reactor temperature is 80-160℃, and the residence time of the reactants in the reactor is 0.2-0.5h.

6. The method for synthesizing 1,4-bis(4-fluorobenzoyl)benzene using ultrasound according to claim 4, characterized in that, In step 2, the reactor is a tubular reactor with a length-to-diameter ratio greater than 100.

7. The method for synthesizing 1,4-bis(4-fluorobenzoyl)benzene using ultrasound according to claim 4, characterized in that, Post-processing in step 3 includes the following steps: S1 filtration involves quenching the material in the intermediate tank with water to precipitate crude 1,4-bis(4-fluorobenzoyl)benzene. S2 material recovery, the filtrate is separated into fluorobenzene phase and aqueous phase, the fluorobenzene phase is distilled to obtain fluorobenzene, and the aqueous phase is distilled to obtain trifluoromethane sulfonic acid compound catalyst. S3 recrystallization, washing the crude product with water and crystallizing the solution yielded purified 1,4-bis(4-fluorobenzoyl)benzene.

8. The method for synthesizing 1,4-bis(4-fluorobenzoyl)benzene using ultrasound according to claim 7, characterized in that, The mass ratio of material to water in the intermediate tank in step S1 is (1:1) - (1:3).

9. A method for synthesizing 1,4-bis(4-fluorobenzoyl)benzene using ultrasound according to claim 7, characterized in that, During the water washing process in step S3, the mass ratio of crude product to water is (1:5) - (1:10).

10. The method for synthesizing 1,4-bis(4-fluorobenzoyl)benzene using ultrasound according to claim 7, characterized in that, In step S3, dipropyl carbonate is used for solution crystallization; The mass ratio of 1,4-bis(4-fluorobenzoyl)benzene to dipropyl carbonate is (1:8) to (1:20).

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