A method for preparing 1,4-di(4-fluorobenzoyl)benzene

Abstract

The invention discloses a preparation method of green synthetic 1,4-di(4-fluorobenzoyl)benzene, which belongs to the technical field of Friedel-Craft reaction. An ionic liquid is used as a catalyst to catalyze the reaction of fluorobenzene and terephthaloyl chloride to generate 1,4-di(4-fluorobenzoyl)benzene. The ionic liquid is one or more of [Bmim]Cl / AlCl3, [Bmim]Br / AlCl3, [Emim]Cl / AlCl3, [Emim]Br / AlCl3, C4H9NBr / AlCl3, Et3NHCl / AlCl3, [Emim]Cl-AlCl3-MgCl2, [Bmim]Cl-AlCl3-CuCl and [Moemim]Br / AlCl3. The ionic liquid of the present invention can convert fluorobenzene and terephthaloyl chloride into 1,4-di(4-fluorobenzoyl)benzene under room temperature, without long-term reflux at the boiling point of fluorobenzene, and has high reaction safety; the ionic liquid can be separated from the reaction system by standing and stratifying after the reaction, and the separation step is simple; the catalyst does not need to be quenched after the reaction, the catalyst can be recycled, no waste salt is generated, and the environment is green and environmentally friendly; the product yield is 96.48%-99.87%, the product purity is 99.62%-99.92%, and the product yield is high.

Description

Technical Field

[0001] The invention relates to the technical field of Friedel-Craft reactions, and in particular to a method for preparing 1,4-di(4-fluorobenzoyl)benzene. Background Art

[0002] Polyaryletherketone (PEAK) is a class of aromatic polymers containing ether bonds and carbonyl groups. It has excellent thermal properties, mechanical properties, electrical insulation properties, etc. It is widely used in electronic appliances, mechanical instruments, transportation and aerospace. After decades of development, many companies have developed polyaryletherketone plastics. 1,4-di(4-fluorobenzoyl)benzene monomer can be used to synthesize polyaryletherketone series polymer materials. The structure is shown in the following formula. However, the current high price of monomers limits the scope of use of polyaryletherketone (PEAK) series polymer materials.

[0003]

[0004] The main synthetic methods of the monomer reported so far are as follows: one is to use a new Friedel-Craft reaction catalyst, such as trifluoromethanesulfonic acid in US Patent US4968845A, polyfluorinated alkyl sulfonic acid in German Patent DE3807623A1, and hydrogen fluoride / boron trifluoride in German Patent DE3806656A1. After the reaction is completed, the catalyst can be recycled, but the yield of 1,4-di(4-fluorobenzoyl)benzene is difficult to reach more than 90%. Alkyl sulfonic acids such as trifluoromethanesulfonic acid are expensive, highly corrosive, and volatile; hydrogen fluoride / boron trifluoride is highly toxic and corrosive, and has strict requirements on equipment; ultimately, none of them were industrialized. Another method is to use classic catalysts such as aluminum trichloride and ferric chloride.

[0005] US Patent US5300693A uses aluminum chloride as a catalyst and fluorobenzene as a solvent to react with terephthaloyl chloride, and the reaction yield can reach 95%. Chlorobenzene is used to recrystallize the crude product of the reaction, and the product purity is greater than 99.5%. US Patent US4820791A, German Patent DE3531837A1, Chinese Patent CN115135691A, etc. all use aluminum chloride as a catalyst to synthesize 1,4-di(4-fluorobenzoyl)benzene, but the molar ratio of aluminum chloride to terephthaloyl chloride is greater than 2:1, resulting in a large consumption of aluminum chloride; and after the reaction is completed, the reaction system is quenched to produce a large amount of waste salt, which causes great environmental pollution; at the same time, the problem that the catalyst cannot be recycled cannot be solved, so this method has not been industrialized.

[0006] In summary, there is currently no low-cost, simple and effective method to prepare 1,4-di(4-fluorobenzoyl)benzene monomer.

[0007] In view of the above problems in the prior art, the present invention combines many years of design and use experience in related fields to design a method for preparing 1,4-di(4-fluorobenzoyl)benzene to overcome the above defects. Summary of the invention

[0008] In order to solve the problems existing in the prior art, the present invention provides a method for preparing 1,4-di(4-fluorobenzoyl)benzene, wherein the reaction conditions are mild and the reaction can be carried out at room temperature; no crystalline aluminum chloride waste salt is produced in the reaction system, and the reaction is green and environmentally friendly; the catalyst can be recycled and the catalyst cost is low; the anion and cation of the catalyst can be controlled, and the reaction conversion rate selectivity is high.

[0009] In order to achieve the above object, the technical scheme adopted by the present invention is as follows: a method for preparing 1,4-di(4-fluorobenzoyl)benzene, using an ionic liquid as a catalyst to catalyze the reaction of fluorobenzene and terephthaloyl chloride to generate 1,4-di(4-fluorobenzoyl)benzene;

[0010] The ionic liquid is [Bmim]Cl / AlCl 3 、[Bmim]Br / AlCl 3 、[Emim]Cl / AlCl 3 、[Emim]Br / AlCl 3 , C 4 H 9 NBr / AlCl 3 , Et 3 NHCl / AlCl 3 、[Emim]Cl-AlCl 3 -MgCl 2 、[Bmim]Cl-AlCl 3 -CuCl, [Moemim]Br / AlCl 3 One or more of the .

[0011] Preferably, the ionic liquid is [Bmim]Cl / AlCl 3 、[Bmim]Br / AlCl 3 、[Emim]Cl / AlCl 3 、[Emim]Br / AlCl 3 One or more of the .

[0012] Preferably, the molar ratio of the organic cation to the aluminum chloride in the ionic liquid is 1:0.67-1:3;

[0013] The mass ratio of magnesium chloride to aluminum chloride in the ionic liquid is 0.01:1-0.05:1;

[0014] The mass ratio of cuprous chloride to aluminum chloride in the ionic liquid is 0.01:1-0.05:1.

[0015] Preferably, the method comprises the following steps:

[0016] (1) Under inert conditions, add ionic liquid and fluorobenzene into a reaction vessel;

[0017] (2) adding terephthaloyl chloride dropwise to the reaction vessel of step (1) at a reaction temperature of 0-30°C and reacting for 1-4 hours after the addition is completed;

[0018] (3) after the reaction is completed, the reaction system of step (2) is post-treated to obtain purified 1,4-di(4-fluorobenzoyl)benzene;

[0019] The dropping time of the terephthaloyl chloride is 10-120 min.

[0020] Preferably, the mass ratio of fluorobenzene to ionic liquid is 10:1-1:1.

[0021] Preferably, the mass ratio of fluorobenzene to terephthaloyl chloride is 10:1-2:1.

[0022] Preferably, in step (2), the reaction temperature is 10-20° C. and the reaction time is 2-3 h.

[0023] Preferably, the dropping time of terephthaloyl chloride in step (2) is 30 minutes.

[0024] Preferably, the post-processing in step (3) comprises the following steps:

[0025] A1 separation: After the reaction in step (2) is completed, the liquid in the reaction container is allowed to stand and separate into layers, the catalyst in the lower layer is separated, and the catalyst is recycled back to the jacket, leaving the liquid in the upper layer;

[0026] A2 washing: adding deionized water to the upper liquid to wash, separating the unreacted fluorobenzene in the system, leaving the remaining mixture, and recycling the fluorobenzene after dehydration;

[0027] A3 Centrifugation and recrystallization: The remaining mixture in step A2 is centrifuged and recrystallized from ethanol to obtain purified 1,4-di(4-fluorobenzoyl)benzene.

[0028] The invention is beneficial in that:

[0029] 1. The ionic liquid in the present invention can convert fluorobenzene and terephthaloyl chloride into 1,4-di(4-fluorobenzoyl)benzene at room temperature, without the need for long-term reflux at the boiling point of fluorobenzene. The reaction conditions are mild and the reaction safety is high. After the reaction is completed, the ionic liquid can be separated from the reaction system by standing and stratifying, without the need for neutralization, avoiding the generation of waste salt, and being green and environmentally friendly. The anion and cation of the catalyst in the reaction process can be adjusted, the acidity of the catalyst can be adjusted, the reaction system is homogeneous, the product yield is high, the yield is 96.48%-99.07%, and the purity is 99.62%-99.92%;

[0030] 2. The ionic liquid catalyst of the present invention can be recycled. After being recycled 10 times, the conversion rate and selectivity of the catalyst do not show obvious attenuation, and the catalyst has high stability. DETAILED DESCRIPTION

[0031] In order to facilitate understanding by those skilled in the art, the present invention is further described below in conjunction with specific embodiments.

[0032] A method for preparing 1,4-di(4-fluorobenzoyl)benzene, using an ionic liquid as a catalyst to catalyze the reaction of fluorobenzene and terephthaloyl chloride to generate 1,4-di(4-fluorobenzoyl)benzene, wherein the ionic liquid is preferably [Bmim]Cl / AlCl 3 、[Bmim]Br / AlCl 3 、[Emim]Cl / AlCl 3 、[Emim]Br / AlCl 3 , C 4 H 9 NBr / AlCl 3 , Et 3 NHCl / AlCl 3 、[Emim]Cl-AlCl 3 -MgCl 2 、[Bmim]Cl-AlCl 3 -CuCl, [Moemim]Br / AlCl 3 More preferably, [Bmim]Cl / AlCl 3 、[Bmim]Br / AlCl 3 、[Emim]Cl / AlCl 3 、[Emim]Br / AlCl 3One or more of the above. The molar ratio of organic cations to aluminum chloride in the ionic liquid is 1:0.67-1:3, the mass ratio of magnesium chloride to aluminum chloride in the ionic liquid is 0.01:1-0.05:1, and the mass ratio of cuprous chloride to aluminum chloride in the ionic liquid is 0.01:1-0.05:1. The preparation of the ionic liquid of the present invention is a conventional preparation method in the art, which will not be described in detail here.

[0033] In the present invention, ionic liquid is used as a catalyst to catalyze the Friedel-Crafts reaction, and the catalyst can be adjusted by adjusting the types and quantities of organic cations and anions, thereby improving the selectivity and conversion rate of the reaction of fluorobenzene and terephthaloyl chloride.

[0034] Specifically, the preparation of 1,4-di(4-fluorobenzoyl)benzene comprises the following steps:

[0035] (1) Under inert conditions, add ionic liquid and fluorobenzene into a reaction vessel;

[0036] (2) adding terephthaloyl chloride heated to a liquid state dropwise into the reaction vessel of step (1), the reaction temperature being 0-30°C, the addition time being 10-120 min, and the reaction being carried out for 1-4 h after the addition is completed;

[0037] (3) After the reaction is completed, the reaction system of step (2) is post-treated to obtain purified 1,4-di(4-fluorobenzoyl)benzene.

[0038] In a preferred embodiment of the present invention, the mass ratio of fluorobenzene to ionic liquid is 10:1-1:1, more preferably 8:1-6:1; the mass ratio of fluorobenzene to terephthaloyl chloride is preferably 10:1-2:1, more preferably, the mass ratio of fluorobenzene to terephthaloyl chloride is 10:1-5:1; the reaction temperature in step (2) is 10-20°C, the reaction time is 2-3h; the dropwise addition time of terephthaloyl chloride in step (2) is preferably 30min. After optimizing the reaction conditions, the purity of the obtained 1,4-di(4-fluorobenzoyl)benzene reaches 99.55%-99.92%, and the yield reaches 96.58%-99.07%.

[0039] The post-treatment in step (3) of the present invention comprises the following steps:

[0040] A1 separation: after the reaction in step (2) is completed, the liquid in the reaction container is allowed to stand and separate into layers, the lower layer of ionic liquid is separated, the ionic liquid is recycled back to the jacket, and the upper layer of liquid is retained;

[0041] A2 washing: deionized water is added to the upper liquid to wash, and the unreacted fluorobenzene in the system is separated, and the remaining mixture is retained. The fluorobenzene is dehydrated and then re-jacketed. The mass ratio of deionized water to fluorobenzene raw material is 1:0.3-1:1;

[0042] A3 Centrifugation and recrystallization: The remaining mixture in step A2 is centrifuged and recrystallized from ethanol to obtain purified 1,4-di(4-fluorobenzoyl)benzene.

[0043] After the reaction is completed, the present invention divides the reaction system into two layers, the lower layer is an ionic liquid, and the ionic liquid can be separated for reaction recycling by layering operation without quenching the reaction system, no waste salt is generated, and the post-reaction treatment process is simple. After deionized water is added to the upper liquid in step A2, the product precipitates from the liquid, and the unreacted fluorobenzene and the aqueous phase are layered to separate the fluorobenzene, and the separated fluorobenzene can be reused for the reaction after dehydration. Ethanol recrystallization is used to remove ortho-isomers and other impurities in the product. After the conditions are optimized, the product yield is 96.48%-99.07%, the purity is 99.62%-99.92%, and the activity of the catalyst does not significantly decay after 10 cycles.

[0044] The specific embodiments are as follows

[0045] [Bmim]Cl / AlCl 3 Preparation of ionic liquids:

[0046] [Bmim]Cl was placed in a pre-dried three-necked flask. Under nitrogen protection, weighed anhydrous aluminum chloride was added in batches and stirred continuously. After the anhydrous aluminum chloride was completely dissolved, an ionic liquid was obtained. By changing the amount of aluminum chloride added, ionic liquids with different acidities were prepared, and [Bmim]Cl and AlCl were obtained in turn. 3 The molar ratios of the catalysts are 1:0.67, 1:1, 1:1.5, 1:2 and 1:3. Example 1

[0047] (1) Under nitrogen protection, take 2 kg of [Bmim]Cl / AlCl 3 (1:0.67) catalyst and 10 kg of fluorobenzene were added to a 20 L reactor and stirred;

[0048] (2) Slowly add 2 kg of terephthaloyl chloride to the reactor at a reaction temperature of 15 °C, a dropwise addition time of 120 min, and a reaction time of 1 h. Stop stirring after the reaction is complete.

[0049] (3) Separation: The reaction system in step (2) in the reactor is allowed to stand for stratification, the catalyst in the lower layer is separated, and the catalyst is recycled;

[0050] Washing: Deionized water (the mass ratio of water to fluorobenzene is 1:0.8) is added to the upper liquid for washing, and white solid is precipitated from the liquid. Unreacted fluorobenzene and deionized water are separated by liquid-liquid extraction. Fluorobenzene is dehydrated and then re-jacketed. The remaining mixture after separation is sent to a centrifugal unit;

[0051] Centrifugation and recrystallization: The mixture is centrifuged to obtain a crude product of 1,4-di(4-fluorobenzoyl)benzene as a white solid substance. The crude product of 1,4-di(4-fluorobenzoyl)benzene is crystallized using ethanol to obtain purified 1,4-di(4-fluorobenzoyl)benzene. Example 2

[0052] In this example, 1,4-di(4-fluorobenzoyl)benzene was synthesized according to the steps of Example 1, except that the catalyst in this example was [Bmim]Cl / AlCl 3 (1:1), in step (2), the reaction temperature is 20°C, the dropping time of terephthaloyl chloride is 60 minutes, and the reaction time is 2 hours. Example 3

[0053] In this example, 1,4-di(4-fluorobenzoyl)benzene was synthesized according to the steps of Example 1, except that the catalyst in this example was [Bmim]Cl / AlCl 3 (1:1.5), in step (2), the reaction temperature is 30°C, the dropping time of terephthaloyl chloride is 30 min, and the reaction time is 2.5 h. Example 4

[0054] In this example, 1,4-di(4-fluorobenzoyl)benzene was synthesized according to the steps of Example 1, except that the catalyst in this example was [Bmim]Cl / AlCl 3 (1:2), in step (2), the reaction temperature is 10°C, the dropping time of terephthaloyl chloride is 10 minutes, and the reaction time is 4 hours. Example 5

[0055] In this example, 1,4-di(4-fluorobenzoyl)benzene was synthesized according to the steps of Example 1, except that the catalyst in this example was [Bmim]Cl / AlCl 3 (1:3), in step (2), the reaction temperature is 20°C, the dropping time of terephthaloyl chloride is 60 minutes, and the reaction time is 3.5 hours.

[0056] The yield and purity of the products synthesized in Examples 1-5 were tested by gas chromatography, and Table 1 was obtained.

[0057] Table 1 Table of product preparation of Examples 1-5

[0058] Example 6

[0059] In this example, 1,4-di(4-fluorobenzoyl)benzene was synthesized according to the steps of Example 1, except that the catalyst in this example was [Bmim]Cl / AlCl recycled 10 times. 3 (1:3) ionic liquid.

[0060] The product of this example was tested by gas chromatography, and the yield of 1,4-di(4-fluorobenzoyl)benzene was 93.12% and the purity was 99.86%.

[0061] Et 3 NHCl / AlCl 3 Preparation of ionic liquids:

[0062] Under nitrogen atmosphere, triethylamine hydrochloride solution was dissolved in fluorobenzene, anhydrous aluminum chloride was added to the reaction system in batches, and the temperature was raised to 60°C using an oil bath and magnetic stirring, and the reaction was continued for 120 min to ensure that the reaction was complete. After the reaction was completed, the mixture was allowed to stand and stratify to obtain a dark brown transparent ionic liquid. The amount of anhydrous aluminum chloride added was changed to obtain Et 3 NHCl and AlCl 3 The molar ratios of the catalysts are 1:0.67, 1:1, 1:1.5, 1:2 and 1:3. Example 7

[0063] (1) Under nitrogen protection, take 2 kg of Et 3 NHCl / AlCl 3 (1:0.67) catalyst and 12 kg of fluorobenzene were added to a 20 L reactor and stirred;

[0064] (2) 1.8 kg of terephthaloyl chloride was slowly added dropwise to the reactor. The addition time was 30 min, the reaction temperature was 30 °C, the reaction time was 2 h, and stirring was stopped after the reaction was completed;

[0065] (3) Separation: The reaction system in step (2) in the reactor is allowed to stand for stratification, the catalyst in the lower layer is separated, and the catalyst is recycled;

[0066] Washing: Deionized water (the mass ratio of water to fluorobenzene is 1:1) is added to the upper layer of liquid for washing, and white solid is precipitated from the liquid. Unreacted fluorobenzene and deionized water are separated by liquid-liquid extraction. Fluorobenzene is dehydrated and then re-jacketed. The remaining mixture after separation is sent to a centrifugal unit;

[0067] Centrifugation and recrystallization: The mixture is centrifuged to obtain a crude product of 1,4-di(4-fluorobenzoyl)benzene as a white solid substance. The crude product of 1,4-di(4-fluorobenzoyl)benzene is crystallized using ethanol to obtain purified 1,4-di(4-fluorobenzoyl)benzene.

[0068] Example 8

[0069] In this example, 1,4-di(4-fluorobenzoyl)benzene was synthesized according to the steps of Example 7, except that the catalyst in this example was Et 3 NHCl / AlCl 3 (1:1), the reaction temperature in step (2) is 0°C and the reaction time is 3.5h.

[0070] Example 9

[0071] In this example, 1,4-di(4-fluorobenzoyl)benzene was synthesized according to the steps of Example 7, except that the catalyst in this example was Et 3 NHCl / AlCl 3 (1:1.5), in step (2), the reaction temperature is 15°C, the dropping time of terephthaloyl chloride is 60 minutes, and the reaction time is 3 hours. Example 10

[0072] In this example, 1,4-di(4-fluorobenzoyl)benzene was synthesized according to the steps of Example 7, except that the catalyst in this example was Et 3 NHCl / AlCl 3 (1:2), the reaction temperature in step (2) is 20°C and the reaction time is 2.5h. Embodiment 11

[0073] In this example, 1,4-di(4-fluorobenzoyl)benzene was synthesized according to the steps of Example 7, except that the catalyst in this example was Et 3 NHCl / AlCl 3 (1:3), in step (2), the reaction temperature is 25°C, the addition time of terephthaloyl chloride is 60 minutes, and the reaction time is 2 hours.

[0074] The yield and purity of the products synthesized in Examples 7-11 were tested, and the results are shown in Table 2.

[0075] Table 2: Preparation of products in Examples 7-11

[0076]

[0077] [Bmim]Cl-AlCl 3 - Preparation of CuCl ionic liquid catalyst:

[0078] Under nitrogen protection, add 1 mol [Bmim]Cl and 2 mol anhydrous aluminum chloride to a three-necked flask, stir and mix, and heat at 100 ° C for 2 h to obtain an ionic liquid. Add 0.13 mol cuprous chloride to the ionic liquid and heat at 90 ° C for 2 h to obtain [Bmim]Cl-AlCl 3 -CuCl. Example 12

[0079] (1) Under argon protection, take 5kg [Bmim]Cl-AlCl 3 -CuCl catalyst and 5 kg of fluorobenzene were added into a 20 L reactor and stirred;

[0080] (2) Slowly add 2 kg of terephthaloyl chloride to the reactor at a reaction temperature of 15 °C, a dropwise addition time of 30 min, and a reaction time of 4 h. After the reaction is complete, stop stirring;

[0081] (3) Separation: The liquid phase of step (2) in the reactor is allowed to stand for stratification, the catalyst in the lower layer is separated, the upper liquid is retained, and the catalyst is recycled;

[0082] Washing: Deionized water is added to the upper liquid for washing (the mass ratio of deionized water to fluorobenzene is 1:0.9), and a white solid is precipitated from the liquid. The unreacted fluorobenzene and the deionized water are separated, and the fluorobenzene is separated by liquid-liquid extraction. The fluorobenzene is dehydrated and then re-jacketed, and the remaining mixture after separation is sent to a centrifugal unit;

[0083] Centrifugation and recrystallization: The mixture was centrifuged to obtain a crude product of 1,4-di(4-fluorobenzoyl)benzene as a white solid. The crude product of 1,4-di(4-fluorobenzoyl)benzene was crystallized using ethanol to obtain purified 1,4-di(4-fluorobenzoyl)benzene. The yield of the product was 98.65% and the purity was 99.89%.

[0084] [Emic]Cl-AlCl 3 -MgCl 2 Preparation of ionic liquid catalysts:

[0085] Under nitrogen protection, add 1 mol [Emic]Cl and 2 mol anhydrous aluminum chloride to a three-necked flask, stir and mix, and heat at 100°C for 2 hours to obtain an ionic liquid. Add 0.14 mol magnesium chloride to the ionic liquid and heat at 90°C for 2 hours to obtain [Emim]Cl-AlCl 3 -MgCl 2 . Example 13

[0086] (1) Under argon protection, take 1.3 kg [Emim] Cl-AlCl 3-MgCl 2 The catalyst and 10 kg of fluorobenzene were added into a 20 L reactor and stirred;

[0087] (2) Slowly add 1 kg of terephthaloyl chloride to the reactor at a reaction temperature of 15°C, a dropwise addition time of 30 min, and a reaction time of 4 h. After the reaction is complete, stop stirring;

[0088] (3) Separation: The liquid phase of step (2) in the reactor is allowed to stand for stratification, the catalyst in the lower layer is separated, the upper liquid is retained, and the catalyst is recycled;

[0089] Washing: Deionized water is added to the upper liquid for washing (the mass ratio of deionized water to fluorobenzene is 1:0.3), and a white solid is precipitated from the liquid. The unreacted fluorobenzene and the deionized water are separated, and the fluorobenzene is separated by liquid-liquid extraction. The fluorobenzene is dehydrated and then re-jacketed, and the remaining mixture after separation is sent to a centrifugal unit;

[0090] Centrifugation and recrystallization: The mixture was centrifuged to obtain a crude product of 1,4-di(4-fluorobenzoyl)benzene as a white solid. The crude product of 1,4-di(4-fluorobenzoyl)benzene was crystallized using ethanol to obtain purified 1,4-di(4-fluorobenzoyl)benzene. The yield of the product was 95.65% and the purity was 99.91%.

[0091] [Emim]Br / AlCl 3 Preparation of ionic liquid catalysts:

[0092] Under nitrogen protection, 1 mol of [Emim]Br was mixed with 2 mol of aluminum chloride and stirred at room temperature for 24 hours to obtain a light yellow liquid, which is [Emim]Br / AlCl 3 Ionic liquids. Embodiment 14

[0093] (1) Under argon protection, take 3kg [Emim] Br / AlCl 3 The catalyst and 8.6 kg of fluorobenzene were added into a 20 L reactor and stirred;

[0094] (2) Slowly add 2 kg of terephthaloyl chloride to the reactor at a reaction temperature of 20 °C for 30 min and a reaction time of 3 h. After the reaction is complete, stop stirring.

[0095] (3) Separation: The liquid phase of step (2) in the reactor is allowed to stand for stratification, the catalyst in the lower layer is separated, the upper liquid is retained, and the catalyst is recycled;

[0096] Washing: Deionized water is added to the upper liquid for washing (the mass ratio of deionized water to fluorobenzene is 1:0.8), and a white solid is precipitated from the liquid. The unreacted fluorobenzene and the deionized water are separated, and the fluorobenzene is separated by liquid-liquid extraction. The fluorobenzene is dehydrated and then re-jacketed. The remaining mixture after separation is sent to a centrifugal unit;

[0097] Centrifugation and recrystallization: The mixture was centrifuged to obtain a crude product of 1,4-di(4-fluorobenzoyl)benzene as a white solid substance. The crude product of 1,4-di(4-fluorobenzoyl)benzene was crystallized using ethanol to obtain purified 1,4-di(4-fluorobenzoyl)benzene. The product yield was 99.86% and the purity was 99.92%. Embodiment 15

[0098] In this example, 1,4-di(4-fluorobenzoyl)benzene was synthesized according to the steps of Example 14, except that the catalyst used in this example was [Emim]Br / AlCl recycled 10 times. 3 Ionic liquids.

[0099] The product of this example was tested by gas chromatography, and the yield of 1,4-di(4-fluorobenzoyl)benzene was 99.82% and the purity was 99.91%.

[0100] [Bmim]Br / AlCl 3 Preparation of ionic liquid catalysts:

[0101] Under nitrogen protection, 1 mol of [Bmim]Br was mixed with 2 mol of aluminum chloride and stirred at room temperature for 24 hours until the solid disappeared. The resulting liquid was [Bmim]Br / AlCl 3 Ionic liquids. Example 16

[0102] (1) Under argon protection, take 1.5 kg [Bmim] Br / AlCl 3 The catalyst and 8.6 kg of fluorobenzene were added into a 20 L reactor and stirred;

[0103] (2) Slowly add 2 kg of terephthaloyl chloride to the reactor at a reaction temperature of 20 °C for 30 min and a reaction time of 3 h. After the reaction is complete, stop stirring.

[0104] (3) Separation: The liquid phase of step (2) in the reactor is allowed to stand for stratification, the catalyst in the lower layer is separated, the upper liquid is retained, and the catalyst is recycled;

[0105] Washing: Deionized water is added to the upper liquid for washing (the mass ratio of deionized water to fluorobenzene is 1:08), the unreacted fluorobenzene and the deionized water are separated, and a white solid is precipitated from the system. The fluorobenzene in the system is separated by liquid-liquid extraction and separation operation. The fluorobenzene is dehydrated and then re-jacketed, and the remaining mixture after separation is sent to a centrifugal unit;

[0106] Centrifugation and recrystallization: The mixture was centrifuged to obtain a crude product of 1,4-di(4-fluorobenzoyl)benzene as a white solid. The crude product of 1,4-di(4-fluorobenzoyl)benzene was crystallized using ethanol to obtain purified 1,4-di(4-fluorobenzoyl)benzene. The yield of the product was 99.85% and the purity was 99.91%. Embodiment 17

[0107] In this example, 1,4-di(4-fluorobenzoyl)benzene was synthesized according to the steps of Example 16, except that the catalyst used in this example was [Bmim]Br / AlCl recycled 10 times. 3 Ionic liquids.

[0108] The product of this example was tested by gas chromatography, and the yield of 1,4-di(4-fluorobenzoyl)benzene was 99.81% and the purity was 99.93%.

[0109] [Moemim]Br / AlC1 3 Preparation of ionic liquid catalysts:

[0110] Under nitrogen protection, 1 mol of C 4 H 9 NBr is mixed with 2 mol of aluminum chloride and stirred at room temperature for 24 h until the solid disappears. The resulting liquid is [Moemim]Br / AlCl 3 Ionic liquids. Embodiment 18

[0111] (1) Under argon protection, take 1kg [Moemim] Br / AlCl 3 The catalyst and 5 kg of fluorobenzene were added into a 20 L reactor and stirred;

[0112] (2) Slowly add 0.5 kg of terephthaloyl chloride to the reactor at a reaction temperature of 20 °C for 30 min and a reaction time of 3 h. After the reaction is complete, stop stirring.

[0113] (3) Separation: The liquid phase of step (2) in the reactor is allowed to stand for stratification, the catalyst in the lower layer is separated, the upper liquid is retained, and the catalyst is recycled;

[0114] Washing: Deionized water is added to the upper liquid for washing (the mass ratio of deionized water to fluorobenzene is 1:0.8), and white solid is precipitated from the liquid. Unreacted fluorobenzene and deionized water are separated by liquid-liquid extraction. Fluorobenzene is dehydrated and recycled, and the remaining mixture after separation is sent to the centrifugal unit;

[0115] Centrifugation and recrystallization: The mixture was centrifuged to obtain a crude product of 1,4-di(4-fluorobenzoyl)benzene as a white solid. The crude product of 1,4-di(4-fluorobenzoyl)benzene was crystallized using ethanol to obtain purified 1,4-di(4-fluorobenzoyl)benzene. The yield of the product was 99.36% and the purity was 99.85%.

[0116] It can be seen from Examples 1-18 that the present invention uses ionic liquid as a catalyst, and the product yield after the reaction is between 92.25% and 99.87%, and the purity is between 98.15% and 99.92%. After screening the reaction conditions, the product yield after the reaction is 96.48% to 99.87%, and the purity is 99.62% to 99.92%. Moreover, after the ionic liquid is recycled for 10 times, the catalyst activity does not significantly decay, and the product yield and purity do not significantly decrease.

[0117] It should be understood that the purpose of these embodiments is only to illustrate the present invention and is not intended 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 of these equivalent forms also fall within the protection scope defined by the claims attached to this application.

Claims

1. A method for preparing 1,4-di(4-fluorobenzoyl)benzene, characterized in that: Using ionic liquid as catalyst, fluorobenzene and terephthaloyl chloride react to generate 1,4-di(4-fluorobenzoyl)benzene; The ionic liquid is one or more of [Bmim]Cl / AlCl3, [Bmim]Br / AlCl3, [Emim]Cl / AlCl3, [Emim]Br / AlCl3, C4H9NBr / AlCl3, Et3NHCl / AlCl3, [Emim]Cl-AlCl3-MgCl2, [Bmim]Cl-AlCl3-CuCl, and [Moemim]Br / AlC13; The molar ratio of the organic cation to aluminum chloride in the ionic liquid is 1:0.67-1:3; The mass ratio of magnesium chloride to aluminum chloride in the ionic liquid is 0.01:1-0.05:1; The mass ratio of cuprous chloride to aluminum chloride in the ionic liquid is 0.01:1-0.05:

1.

2. The method for preparing 1,4-di(4-fluorobenzoyl)benzene according to claim 1, characterized in that: The ionic liquid is one or more of [Bmim]Cl / AlCl3, [Bmim]Br / AlCl3, [Emim]Cl / AlCl3, and [Emim]Br / AlCl3.

3. The method for preparing 1,4-di(4-fluorobenzoyl)benzene according to claim 1, characterized in that: The following steps are involved: (1) Under inert conditions, add ionic liquid and fluorobenzene into a reaction vessel; (2) adding terephthaloyl chloride dropwise to the reaction vessel of step (1) at a reaction temperature of 0-30°C and reacting for 1-4 hours after the addition is completed; (3) After the reaction is completed, the reaction system of step (2) is post-treated to obtain purified 1,4-di(4-fluorobenzoyl)benzene; The dropping time of the terephthaloyl chloride is 10-120 min.

4. The method for preparing 1,4-di(4-fluorobenzoyl)benzene according to claim 3, characterized in that: The mass ratio of the fluorobenzene to the ionic liquid is 10:1-1:

1.

5. The method for preparing 1,4-di(4-fluorobenzoyl)benzene according to claim 3, characterized in that: The mass ratio of the fluorobenzene to terephthaloyl chloride is 10:1-2:

1.

6. The method for preparing 1,4-di(4-fluorobenzoyl)benzene according to claim 3, characterized in that: The mass ratio of the fluorobenzene to terephthaloyl chloride is 10:1-5:

1.

7. The method for preparing 1,4-di(4-fluorobenzoyl)benzene according to claim 3, characterized in that: In step (2), the reaction temperature is 10-20°C and the reaction time is 2-3h.

8. The method for preparing 1,4-di(4-fluorobenzoyl)benzene according to claim 3, characterized in that: The dropping time of terephthaloyl chloride in step (2) is 30 minutes.

9. The method for preparing 1,4-di(4-fluorobenzoyl)benzene according to claim 3, characterized in that: The post-processing in step (3) includes the following steps: A1 separation: After the reaction in step (2) is completed, the liquid in the reaction container is allowed to stand and separate into layers, and the lower layer of ionic liquid is separated. The ionic liquid is circulated back to the jacket, and the upper layer of liquid is retained; A2 washing: adding deionized water to the upper liquid to wash, separating the unreacted fluorobenzene in the system, leaving the remaining mixture, and recycling the fluorobenzene after dehydration; A3 Centrifugation and recrystallization: The remaining mixture in step A2 is centrifuged and recrystallized from ethanol to obtain purified 1,4-di(4-fluorobenzoyl)benzene.

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