The invention relates to a 2-(4apos; continuous synthesis method of-pentylbenzoyl) benzoic acid

Abstract

The invention provides a continuous synthesis method of 2-(4 '-pentylbenzoyl) benzoic acid, and relates to the field of synthesis of 2-(4'-pentylbenzoyl) benzoic acid. The continuous synthesis method of the 2-(4 '-pentylbenzoyl) benzoic acid comprises the following steps: continuous catalytic reaction and post-treatment. The continuous synthesis method of the 2-(4 '-pentylbenzoyl) benzoic acid can effectively realize continuous and stable synthesis of the 2-(4'-pentylbenzoyl) benzoic acid on the premise of reducing the dosage of the traditional aluminum trichloride catalyst, improves the yield and purity of the continuously prepared 2-(4 '-pentylbenzoyl) benzoic acid, and reduces by-products.

Description

Technical Field

[0001] This invention relates to the field of 2-(4'-pentylbenzoyl)benzoic acid synthesis, and in particular to a continuous synthesis method for 2-(4'-pentylbenzoyl)benzoic acid. Background Technology

[0002] Hydrogen peroxide is an important chemical raw material, widely used in industries such as papermaking and textiles. In recent years, with the rapid development of industries like papermaking, the demand for hydrogen peroxide has increased rapidly. 2-alkylanthraquinone is a commonly used carrier in hydrogen peroxide production; 2-pentylanthraquinone, in particular, can be used to prepare a highly efficient working solution in hydrogen peroxide production, and its high solubility and production capacity have made it highly valued. Furthermore, 2-pentylanthraquinone is also widely used in the synthesis of photosensitive compounds. Moreover, with the continuous development of industries such as chemicals and electronics, the demand for high-purity 2-pentylanthraquinone is also constantly increasing.

[0003] 2-(4'-Pentylbenzoyl)benzoic acid is an intermediate in the synthesis of 2-pentylanthraquinone. The traditional method for synthesizing 2-(4'-pentylbenzoyl)benzoic acid uses tert-pentylbenzene and phthalic anhydride as raw materials, with aluminum trichloride as a catalyst, and is carried out in a glass reactor in a batch reaction manner. However, this batch process has drawbacks such as cumbersome operation, large catalyst consumption, severe rearrangement of tert-pentylbenzene leading to numerous byproducts and isomers, low product isomer ratio, and poor yield of the target product. The synthetic route is as follows:

[0004] In the acylation reaction for the synthesis of 2-(4'-pentylbenzoyl)benzoic acid, when AlCl3 catalyzes the reaction of tert-pentylbenzene with phthalic anhydride, the tert-pentyl carbocation readily undergoes migration and rearrangement to generate a secondary pentyl carbocation. This results in the acyl group primarily attaching to the rearranged secondary pentyl group, forming the byproduct 2-(4'-secondary pentylbenzoyl)benzoic acid.

[0005] Chinese patent CN104262131A discloses a method for producing 2-(4'-tert-amylbenzoyl)benzoic acid. The method involves first dissolving phthalic anhydride, aluminum trichloride, and chlorobenzene at room temperature by stirring. After complexation, the mixture is cooled to a predetermined temperature, and gas is introduced. The discharged gas is absorbed by water. The molar ratio of the raw materials used is phthalic anhydride:tert-amylbenzene:aluminum trichloride:chlorobenzene = 1-1.5:1:2-2.5:5-10. This method is a batch reaction process and requires a high amount of aluminum trichloride (approximately 1.5-1.8 times the molar amount of phthalic anhydride). The final product has a high proportion of isomers, resulting in a low yield of the target product. Furthermore, the existing methods for preparing 2-(4'-pentylbenzoyl)benzoic acid also fail to meet the requirements for continuous synthesis due to the lack of stability in the continuous reaction process, making it impossible to continuously and stably prepare high-yield, high-quality 2-(4'-pentylbenzoyl)benzoic acid. Summary of the Invention

[0006] To address the technical problems existing in the prior art, this invention provides a continuous synthesis method for 2-(4'-pentylbenzoyl)benzoic acid, which can effectively achieve continuous and stable synthesis of 2-(4'-pentylbenzoyl)benzoic acid while reducing the amount of aluminum trichloride catalyst used. This method improves the yield and purity of the continuously produced 2-(4'-pentylbenzoyl)benzoic acid and reduces byproducts.

[0007] To solve the above technical problems, the technical solution adopted by the present invention is as follows: A continuous synthesis method for 2-(4'-pentylbenzoyl)benzoic acid includes the following steps: continuous catalytic reaction and post-treatment; The continuous catalytic reaction method is as follows: under a nitrogen atmosphere, material A and material B are simultaneously and continuously fed into a static mixer, with the front section temperature of the static mixer controlled at 0-10℃ and the rear section temperature at 10-15℃; after mixing in the static mixer, the mixture enters a pipeline reactor, with the temperature of the pipeline reactor controlled at 20-25℃, to continuously carry out the continuous catalytic reaction and continuously obtain a crude reaction solution; the crude reaction solution is then post-treated to obtain 2-(4'-pentylbenzoyl)benzoic acid; Material A consists of a catalyst mixture and phthalic anhydride; material B is tert-amylbenzene. The catalyst mixture consists of anhydrous aluminum trichloride, N,N-dimethylaniline, ytterbium trifluoromethanesulfonate, and chlorobenzene.

[0008] Preferably, in the continuous catalytic reaction, the mass ratio of material A to material B fed into the static mixer per unit time is 25-30:2-3.

[0009] Preferably, in the continuous catalytic reaction, the total residence time of material A and material B in the static mixer is 5-8 s; the residence time of the mixture in the pipeline reactor is 50-70 s.

[0010] Preferably, the mass ratio of the catalyst mixture to phthalic anhydride in material A is 100:9-11; In the catalyst mixture, the mass ratio of anhydrous aluminum trichloride, N,N-dimethylaniline, ytterbium trifluoromethanesulfonate, and chlorobenzene is 50:34-36:7-9:500-550.

[0011] Furthermore, the post-treatment method is as follows: the crude reaction product solution is continuously introduced into a continuous acid hydrolysis tower for countercurrent contact with hydrochloric acid solution for acid hydrolysis, and the pH of the material at the outlet of the continuous acid hydrolysis tower is controlled to be 2-3; the aqueous phase after acid hydrolysis is precipitated with diethyl ether to recover ytterbium trifluoromethanesulfonate; the organic phase after acid hydrolysis is continuously introduced into a countercurrent water washing tower for countercurrent contact with washing water for water washing; the material after water washing is sequentially passed through a continuous alkali dissolution column and a continuous acid washing column to remove impurities, and the solids are separated and collected. The solids are washed and dried to obtain 2-(4'-pentylbenzoyl)benzoic acid.

[0012] Preferably, in the post-treatment, the concentration of the hydrochloric acid solution used in the continuous acidolysis tower is 4-6 wt%. The mass flow ratio of the crude product solution to the hydrochloric acid solution in the continuous acidolysis tower is 1:2.8-3.2.

[0013] Preferably, in the post-treatment, the temperature of the countercurrent water wash is 75-85℃ and the time is 25-35 min; The mass flow ratio of the acid-hydrolyzed organic phase to the washing water is 1:1-1.2.

[0014] Preferably, in the post-treatment, a sodium hydroxide solution with a concentration of 5.5-6 wt% is used in the continuous alkali dissolution column, and the mass ratio of the washed material to the sodium hydroxide solution is 5.5-6:1. A 5.5-6 wt% hydrochloric acid solution is used in the continuous pickling column, and the mass ratio of the washed material to the hydrochloric acid solution is 5.5-6:1.

[0015] Furthermore, the catalyst mixture is prepared by dissolving N,N-dimethylaniline in chlorobenzene under a nitrogen atmosphere, cooling it to 0-5°C, and keeping it at that temperature; adding anhydrous aluminum trichloride while stirring, stirring until homogeneous, and then adding ytterbium trifluoromethanesulfonate while stirring until homogeneous to obtain the catalyst mixture.

[0016] Preferably, the method for adding anhydrous aluminum trichloride is to divide the anhydrous aluminum trichloride into 3-4 equal parts, and add one part of anhydrous aluminum trichloride every 4-5 minutes until all the anhydrous aluminum trichloride has been added.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The continuous synthesis method of 2-(4'-pentylbenzoyl)benzoic acid of the present invention, taking into account the continuous flow reaction characteristics of phthalic anhydride and tert-pentylbenzene, specifically uses N,N-dimethylaniline and aluminum trichloride to form a coordination catalyst, thereby improving the product yield and reducing the generation of by-products; effectively overcoming the defect of traditional aluminum trichloride as a strong Lewis acid, which easily activates the tert-pentyl group of tert-pentylbenzene through protonation, leading to carbocation rearrangement, converting the tert-pentyl group into the secondary pentyl group, and finally generating isomeric by-products. In the present invention, after N,N-dimethylaniline is coordinated with aluminum trichloride, the nitrogen atom in the N,N-dimethylaniline molecule has a lone pair of electrons, while aluminum trichloride is a typical Lewis acid. The two can form a complex through coordination bonds, and the lone pair of electrons of the nitrogen atom provides electron density to Al, reducing the electron deficiency of Al, weakening the Lewis acidity, reducing the protonation ability of the tert-pentyl group, and effectively reducing the generation of the by-product 2-(4'-secondary pentylbenzoyl)benzoic acid.

[0018] The inventors further discovered that the coordination of N,N-dimethylaniline with aluminum trichloride reduces byproducts but also affects the acylation reaction efficiency. Therefore, this invention further introduces ytterbium trifluoromethanesulfonate (Yb(OTf)3), which can synergistically interact with the DMA-AlCl3 complex to enhance the overall catalytic activity; the Yb of Yb(OTf)3... 3+ The carbonyl group of phthalic anhydride is further polarized through coordination, enhancing its electrophilicity, promoting the binding efficiency of phthalic anhydride with AlCl3, and accelerating the formation of active complexes; simultaneously, Yb 3+ It can stabilize the acyl cation intermediate, lower the activation energy of the Friedel-Crafts acylation reaction, and increase the reaction rate of para-attack by tert-amylbenzene. Yb 3+ Its strong coordination ability can form weak interactions with the benzene ring or alkyl chain of tert-amylbenzene, and restrict the configurational transformation of the tert-amyl carbocation through steric hindrance, thereby reducing byproducts caused by rearrangement.

[0019] Meanwhile, since AlCl3 is easily hydrolyzed and deactivated, the process of this invention employs nitrogen protection and a slightly positive pressure environment to reduce moisture interference. Furthermore, Yb(OTf)3 exhibits good water resistance. 3+ It preferentially coordinates with trace amounts of moisture that may be present in the system, reducing the hydrolysis of AlCl3 by moisture and indirectly protecting the stability of the DMA-AlCl3 complex. Furthermore, Yb(OTf)3 can also undergo weak complexation with the hydrogen chloride generated in the reaction, reducing the inhibition of AlCl3 activity by HCl and maintaining the long-term stability of the catalyst system.

[0020] (2) The continuous synthesis method of 2-(4'-pentylbenzoyl)benzoic acid of the present invention is designed with a static mixer and a pipeline reactor in combination to take advantage of the continuous flow reaction characteristics of phthalic anhydride and tert-pentylbenzene. Through the turbulence effect in the static mixer and the nitrogen micro-positive pressure environment, micron-level mixing is achieved, which solves the problem of local side reaction caused by uneven mixing in the traditional batch 2-(4'-pentylbenzoyl)benzoic acid preparation. In addition, during the reaction, nitrogen can also remove HCl generated in the reaction in time, promoting the forward reaction. At the same time, a three-stage temperature control process is set up to improve the reaction yield and reduce the generation of by-products.

[0021] (3) The continuous synthesis method of 2-(4'-pentylbenzoyl)benzoic acid of the present invention can effectively reduce the amount of aluminum trichloride catalyst used, and can reduce the molar amount of aluminum trichloride from 2 times the molar amount of phthalic anhydride in the traditional process to 0.8-1 times the molar amount of phthalic anhydride; and can also effectively achieve the continuous and stable synthesis of 2-(4'-pentylbenzoyl)benzoic acid under the premise of reducing the amount of aluminum trichloride catalyst used, and further improve the yield and purity of the continuously obtained 2-(4'-pentylbenzoyl)benzoic acid, and reduce by-products.

[0022] (4) The continuous synthesis method of 2-(4'-pentylbenzoyl)benzoic acid of the present invention can better suppress the rearrangement of tert-pentylbenzene, control the injection rate of raw materials, realize continuous product preparation, improve the purity and yield of 2-(4'-pentylbenzoyl)benzoic acid, and reduce by-products. According to the experiment, the purity of 2-(4'-pentylbenzoyl)benzoic acid prepared by the continuous synthesis method of the present invention is 93.21%-96.07%, the yield is 93.59%-96.24%, and the mass ratio of 2-(4'-tert-pentylbenzoyl)benzoic acid to 2-(4'-sec-pentylbenzoyl)benzoic acid is 93.86-96.42:3.58-6.14. Detailed Implementation

[0023] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments are now described. It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0024] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments of the present invention. As used herein, "first," "second," etc., are used to distinguish similar objects and are not used to describe a particular order or sequence. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0025] This invention provides a continuous synthesis method for 2-(4'-pentylbenzoyl)benzoic acid, comprising the following steps: preparation of a catalyst mixture, continuous catalytic reaction, and post-treatment.

[0026] The method for preparing the catalyst mixture is as follows: N,N-dimethylaniline is dissolved in chlorobenzene, cooled to 0-5℃ and kept at that temperature, nitrogen is continuously introduced to provide a protective atmosphere, and anhydrous aluminum trichloride is added in batches under stirring at 300-400 rpm; after all the anhydrous aluminum trichloride has been added, the mixture is stirred for 25-30 min, and then ytterbium trifluoromethanesulfonate is added and stirred for 20-25 min to obtain the catalyst mixture.

[0027] In the preparation of the catalyst mixture, the flow rate of nitrogen gas is 0.1-0.2 L / min, and the pressure of the mixture system is maintained at 5-10 kPa (gauge pressure).

[0028] In the preparation of the catalyst mixture, the anhydrous aluminum trichloride is added in batches by dividing the anhydrous aluminum trichloride into 3-4 equal parts, adding one part of anhydrous aluminum trichloride every 4-5 minutes, until all the anhydrous aluminum trichloride has been added.

[0029] In the catalyst preparation mixture, the mass ratio of anhydrous aluminum trichloride, N,N-dimethylaniline, ytterbium trifluoromethanesulfonate, and chlorobenzene is 50:34-36:7-9:500-550.

[0030] The continuous catalytic reaction method is as follows: A nitrogen atmosphere is maintained in the first temporary storage vessel. The catalyst mixture and phthalic anhydride are introduced into the first temporary storage vessel and mixed uniformly to obtain material A. A nitrogen atmosphere is maintained in the second temporary storage vessel. Tert-amylbenzene is introduced into the second temporary storage vessel to obtain material B. While maintaining the airtightness of the reaction system, material A is transported by a peristaltic pump, and material B is transported by a horizontal flow pump. Materials A and B are simultaneously fed into the same static mixer, and nitrogen is simultaneously introduced into the static mixer to provide a protective atmosphere (maintaining a slightly positive pressure of 0.1-0.2 MPa). After mixing in the static mixer, the mixture is continuously fed into the pipeline reactor for continuous liquid-liquid mixing, continuously yielding a crude reaction product. During the continuous catalytic reaction, the material temperature in the static mixer and pipeline reactor is controlled by constant-temperature water.

[0031] In the continuous catalytic reaction, the mass ratio of the catalyst mixture to phthalic anhydride in material A is 100:9-11.

[0032] In the continuous catalytic reaction, the flow rate of material A introduced into the static mixer is 25-30 g / min; the flow rate of material B introduced into the static mixer is 2-3 g / min (that is, the mass ratio of material A to material B fed into the static mixer per unit time is 25-30:2-3).

[0033] In the continuous catalytic reaction, the static mixer is equipped with two temperature control zones: a front zone (0-150 mm) with a temperature controlled at 0-10°C, and a rear zone (150-500 mm) with a temperature controlled at 10-15°C. The total residence time of the materials in the static mixer is 5-8 seconds. During this process, materials A and B are initially mixed in the static mixer, and phthalic anhydride and aluminum trichloride form an active complex. Simultaneously, within the temperature range set by the static mixer, the turbulence of the mixture and the molecular diffusion rate reach equilibrium, which promotes effective collisions between phthalic anhydride and tert-pentanebenzene molecules while avoiding catalyst deactivation due to local overheating, thus providing a suitable environment for the stable formation of the active complex.

[0034] In the continuous catalytic reaction, the temperature of the pipeline reactor is controlled at 20-25℃; the residence time of the material in the pipeline reactor is 50-70s. During this process, the main reaction occurs in the pipeline reactor, where the para-carbon atom of tert-pentylbenzene attacks the acyl carbon of phthalic anhydride to generate the target intermediate, namely 2-(4'-pentylbenzoyl)benzoic acid.

[0035] In the continuous catalytic reaction of this invention embodiment, the tert-amyl rearrangement requires a configurational transformation of the carbocation intermediate, such as a transition from tetrahedral to planar configuration. The micro-positive pressure environment can suppress the rearrangement reaction by compressing the free volume of the molecule and increasing the steric hindrance of the configurational transformation. At the same time, the micro-positive pressure can reduce the infiltration of trace amounts of water in the system, maintain the stability of the catalyst activity, and thus avoid catalyst deactivation and side reactions.

[0036] The post-treatment method is as follows: the crude reaction liquid is continuously introduced into a continuous acid hydrolysis tower via a pipeline pump, and comes into countercurrent contact with a hydrochloric acid solution with a concentration of 4-6 wt%. The pH of the material at the outlet of the continuous acid hydrolysis tower is controlled at 2-3 by an online pH meter. The aqueous phase after acid hydrolysis is precipitated with diethyl ether to recover ytterbium trifluoromethanesulfonate. The organic phase after acid hydrolysis is continuously fed into a countercurrent water washing tower, and the water washing temperature is controlled at 75-85℃ and the water washing time is 25-35 min. The material after water washing is passed through a continuous alkali dissolution column and a continuous acid washing column in sequence to remove impurities. The solids are then collected by filtration. The solids are washed and vacuum dried to obtain 2-(4'-pentylbenzoyl)benzoic acid.

[0037] In the post-processing, during continuous acid hydrolysis, the mass flow ratio of the crude reaction solution to hydrochloric acid is 1:2.8-3.2.

[0038] In the post-treatment, the mass ratio of the aqueous phase after acid hydrolysis to diethyl ether is 10:30-40.

[0039] In the post-treatment process, during countercurrent washing, the mass flow ratio of the acid-hydrolyzed organic phase to the washing water is 1:1-1.2.

[0040] In the post-treatment, a sodium hydroxide solution with a concentration of 5.5-6 wt% is used in a continuous alkali dissolution column, and the mass ratio of the washed material to the sodium hydroxide solution is 5.5-6:1.

[0041] In the post-processing, a hydrochloric acid solution with a concentration of 5.5-6 wt% is used in the continuous pickling column, and the mass ratio of the washed material to the hydrochloric acid solution is 5.5-6:1.

[0042] In the post-processing, the vacuum degree of vacuum drying is 0.08-0.09 MPa, and the vacuum drying temperature is 70-80℃.

[0043] In the post-processing of this invention, the acidolysis process mainly involves using dilute acid to break the complexation between the product and aluminum trichloride, thus releasing the product. After the system separates into layers, the aqueous phase contains ytterbium trifluoromethanesulfonate. Diethyl ether is added to precipitate and recover ytterbium trifluoromethanesulfonate. After the system separates into layers, the organic phase enters a water washing tower. Hot water at 75-85°C promotes the dissolution of phthalic anhydride and its entry into the aqueous phase, removing unreacted anhydride. After water washing, the 2-(4'-pentylbenzoyl)benzoic acid in the material reacts with alkali in a continuous alkali dissolution column to form a water-soluble sodium carboxylate, which then enters... In the aqueous phase, the solvent chlorobenzene and unreacted tert-amylbenzene remain in the organic phase, achieving selective separation of the products. After alkali treatment, the material is acid-washed in a continuous acid washing column to restore the carboxyl group of 2-(4'-pentylbenzoyl)benzoic acid. 2-(4'-pentylbenzoyl)benzoic acid has poor water solubility, so a precipitate is formed. After washing and drying, the 2-(4'-pentylbenzoyl)benzoic acid product is obtained. The chlorobenzene and unreacted tert-amylbenzene remaining in the organic phase after water washing are recovered by distillation using the boiling point difference and reused as raw materials in the reaction.

[0044] The present invention will be further described below with reference to some specific embodiments.

[0045] Example 1 This embodiment provides a continuous synthesis method for 2-(4'-pentylbenzoyl)benzoic acid, comprising the following steps: (1) Preparation of catalyst mixture 136g of N,N-dimethylaniline was dissolved in 2000g of chlorobenzene, cooled to 0℃ and kept at that temperature, while nitrogen was continuously introduced to provide a protective atmosphere. Under stirring at 300rpm, 200g of anhydrous aluminum trichloride was divided into 3 equal portions, and one portion of anhydrous aluminum trichloride was added every 4min until all the anhydrous aluminum trichloride was added. Then the stirring was continued for 30min. Then 28g of ytterbium trifluoromethanesulfonate was added and stirred for 25min to obtain the catalyst mixture.

[0046] The flow rate of nitrogen gas is 0.1 L / min, and the pressure of the mixing system is maintained at 5 kPa (gauge pressure).

[0047] (2) Catalytic reaction The continuous catalytic reaction method is as follows: A nitrogen atmosphere is maintained in the first temporary storage vessel. The catalyst mixture and phthalic anhydride are introduced into the first temporary storage vessel and mixed uniformly to obtain material A. A nitrogen atmosphere is maintained in the second temporary storage vessel. Tert-amylbenzene is introduced into the second temporary storage vessel to obtain material B. While maintaining the airtightness of the reaction system, material A is transported by a peristaltic pump, and material B is transported by a horizontal flow pump. Materials A and B are simultaneously fed into the same static mixer, and nitrogen is simultaneously introduced into the static mixer to provide a protective atmosphere (maintaining a slightly positive pressure of 0.1 MPa). After mixing in the static mixer, the mixture enters the pipeline reactor for continuous liquid-liquid mixing, continuously yielding a crude reaction product. During the continuous catalytic reaction, the material temperature in the static mixer and pipeline reactor is controlled by constant-temperature water.

[0048] In material A, the mass ratio of the catalyst mixture to phthalic anhydride is 100:9.

[0049] The flow rate of material A introduced into the static mixer is 25 g / min; the flow rate of material B introduced into the static mixer is 2 g / min.

[0050] The static mixer is configured with two temperature control zones: the front zone (0-150mm) has a temperature control of 0℃; the rear zone (150-500mm) has a temperature control of 12℃. The total residence time of the materials in the static mixer is 5s. Materials A and B are initially mixed in the static mixer, and phthalic anhydride and aluminum trichloride form an active complex.

[0051] The temperature of the pipeline reactor is 20°C, and the residence time of the material in the pipeline reactor is 60s. The main reaction occurs in the pipeline reactor, where the para-carbon atom of tert-pentanebenzene attacks the acyl carbon of phthalic anhydride to generate the target intermediate.

[0052] (3) Post-processing The crude reaction product was continuously pumped into a continuous acid hydrolysis tower, where it was contacted countercurrently with a 4wt% hydrochloric acid solution. The pH of the material at the outlet of the continuous acid hydrolysis tower was controlled to be 2 using an online pH meter. The aqueous phase after acid hydrolysis was precipitated with diethyl ether to recover ytterbium trifluoromethanesulfonate. The organic phase after acid hydrolysis was continuously fed into a countercurrent water washing tower, where it was contacted countercurrently with washing water for washing. The washing temperature was controlled at 75℃ and the washing time was 30 min. After washing, the material was passed through a continuous alkali dissolution column and a continuous acid washing column to remove impurities. The solids were then collected by filtration. After washing, the solids were dried under vacuum at 70℃ with a vacuum degree controlled at 0.08 MPa to obtain 2-(4'-pentylbenzoyl)benzoic acid.

[0053] In the continuous acidolysis process, the mass flow ratio of the crude reaction solution to hydrochloric acid is 1:2.8.

[0054] The mass ratio of the aqueous phase to diethyl ether after acid hydrolysis is 10:30.

[0055] In countercurrent washing, the mass flow ratio of the acid-hydrolyzed organic phase to the washing water is 1:1.1.

[0056] A 6 wt% sodium hydroxide solution was used in the continuous alkali dissolution column, and the mass ratio of the washed material to the sodium hydroxide solution was 6:1.

[0057] A 6 wt% hydrochloric acid solution was used in the continuous pickling column, and the mass ratio of the washed material to the hydrochloric acid solution was 6:1.

[0058] The purity of 2-(4'-pentylbenzoyl)benzoic acid in the product obtained in this embodiment was 96.07%, the yield was 96.01%, and the mass ratio of 2-(4'-tert-pentylbenzoyl)benzoic acid to 2-(4'-sec-pentylbenzoyl)benzoic acid in the product was 96.42:3.58.

[0059] Example 2 This embodiment provides a continuous synthesis method for 2-(4'-pentylbenzoyl)benzoic acid, comprising the following steps: (1) Preparation of catalyst mixture 140g of N,N-dimethylaniline was dissolved in 2080g of chlorobenzene, cooled to 0℃ and kept at that temperature, while nitrogen was continuously introduced to provide a protective atmosphere. Under stirring at 350rpm, 200g of anhydrous aluminum trichloride was divided into 3 equal portions, and one portion of anhydrous aluminum trichloride was added every 4min until all the anhydrous aluminum trichloride was added. Stirring was continued for 28min. Then, 32g of ytterbium trifluoromethanesulfonate was added and stirred for 22min to obtain a catalyst mixture.

[0060] The flow rate of nitrogen gas introduced is 0.15 L / min, and the pressure of the mixing system is maintained at 6 kPa (gauge pressure).

[0061] (2) Catalytic reaction The continuous catalytic reaction method is as follows: A nitrogen atmosphere is maintained in the first temporary storage vessel. The catalyst mixture and phthalic anhydride are introduced into the first temporary storage vessel and mixed uniformly to obtain material A. A nitrogen atmosphere is maintained in the second temporary storage vessel. Tert-amylbenzene is introduced into the second temporary storage vessel to obtain material B. While maintaining the airtightness of the reaction system, material A is transported by a peristaltic pump, and material B is transported by a horizontal flow pump. Materials A and B are simultaneously fed into the same static mixer, and nitrogen is simultaneously introduced into the static mixer to provide a protective atmosphere (maintaining a slightly positive pressure of 0.15 MPa). After mixing in the static mixer, the mixture enters the pipeline reactor for continuous liquid-liquid mixing, continuously yielding a crude reaction product. During the continuous catalytic reaction, the material temperature in the static mixer and pipeline reactor is controlled by constant-temperature water.

[0062] In material A, the mass ratio of the catalyst mixture to phthalic anhydride is 100:10.

[0063] The flow rate of material A introduced into the static mixer is 27 g / min; the flow rate of material B introduced into the static mixer is 2.4 g / min.

[0064] The static mixer is configured with two temperature control zones: the front zone (0-150mm) has a temperature control of 2℃; the rear zone (150-500mm) has a temperature control of 13℃. The total residence time of the materials in the static mixer is 6s. Materials A and B are initially mixed in the static mixer, and phthalic anhydride and aluminum trichloride form an active complex.

[0065] The temperature of the pipeline reactor is 22°C, and the residence time of the material in the pipeline reactor is 60s. The main reaction occurs in the pipeline reactor, where the para-carbon atom of tert-pentanebenzene attacks the acyl carbon of phthalic anhydride to generate the target intermediate.

[0066] (3) Post-processing The crude reaction product was continuously pumped into a continuous acid hydrolysis tower, where it was countercurrently contacted with a 5wt% hydrochloric acid solution. The pH of the material at the outlet of the continuous acid hydrolysis tower was controlled at 2.5 using an online pH meter. The aqueous phase after acid hydrolysis was precipitated with diethyl ether to recover ytterbium trifluoromethanesulfonate. The organic phase after acid hydrolysis was continuously fed into a countercurrent water washing tower, where it was countercurrently contacted with washing water for washing. The washing temperature was controlled at 80℃ and the washing time was 30 min. After washing, the material was passed through a continuous alkali dissolution column and a continuous acid washing column to remove impurities. The solids were then collected by filtration. After washing, the solids were dried under vacuum at 75℃ with a vacuum degree controlled at 0.085 MPa to obtain 2-(4'-pentylbenzoyl)benzoic acid.

[0067] In the continuous acidolysis process, the mass flow ratio of the crude product solution to hydrochloric acid is 1:3.

[0068] The mass ratio of the aqueous phase to diethyl ether after acid hydrolysis is 10:35.

[0069] In countercurrent washing, the mass flow ratio of the acid-hydrolyzed organic phase to the washing water is 1:1.1.

[0070] A 6 wt% sodium hydroxide solution was used in the continuous alkali dissolution column, and the mass ratio of the washed material to the sodium hydroxide solution was 6:1.

[0071] A 6 wt% hydrochloric acid solution was used in the continuous pickling column, and the mass ratio of the washed material to the hydrochloric acid solution was 6:1.

[0072] The purity of 2-(4'-pentylbenzoyl)benzoic acid in the product obtained in this embodiment was 95.74%, the yield was 96.24%, and the mass ratio of 2-(4'-tert-pentylbenzoyl)benzoic acid to 2-(4'-sec-pentylbenzoyl)benzoic acid in the product was 96.36:3.64.

[0073] Example 3 This embodiment provides a continuous synthesis method for 2-(4'-pentylbenzoyl)benzoic acid, comprising the following steps: (1) Preparation of catalyst mixture 144g of N,N-dimethylaniline was dissolved in 2200g of chlorobenzene, cooled to 5°C and kept at that temperature, while nitrogen was continuously introduced to provide a protective atmosphere. Under stirring at 400rpm, 200g of anhydrous aluminum trichloride was divided into 4 equal portions, and one portion of anhydrous aluminum trichloride was added every 5 minutes until all the anhydrous aluminum trichloride was added. Then, stirring was continued for 25 minutes. Then, 36g of ytterbium trifluoromethanesulfonate was added and stirred for 20 minutes to obtain a catalyst mixture.

[0074] The flow rate of nitrogen gas introduced is 0.2 L / min, and the pressure of the mixing system is maintained at 10 kPa (gauge pressure).

[0075] (2) Catalytic reaction The continuous catalytic reaction method is as follows: A nitrogen atmosphere is maintained in the first temporary storage vessel. The catalyst mixture and phthalic anhydride are introduced into the first temporary storage vessel and mixed uniformly to obtain material A. A nitrogen atmosphere is maintained in the second temporary storage vessel. Tert-amylbenzene is introduced into the second temporary storage vessel to obtain material B. While maintaining the airtightness of the reaction system, material A is transported by a peristaltic pump, and material B is transported by a horizontal flow pump. Materials A and B are simultaneously fed into the same static mixer, and nitrogen is simultaneously introduced into the static mixer to provide a protective atmosphere (maintaining a slightly positive pressure of 0.2 MPa). After mixing in the static mixer, the mixture enters the pipeline reactor for continuous liquid-liquid mixing, continuously yielding a crude reaction product. During the continuous catalytic reaction, the material temperature in the static mixer and pipeline reactor is controlled by constant-temperature water.

[0076] In material A, the mass ratio of the catalyst mixture to phthalic anhydride is 100:11.

[0077] The flow rate of material A introduced into the static mixer is 29 g / min; the flow rate of material B introduced into the static mixer is 2.7 g / min.

[0078] The static mixer is configured with two temperature control zones: the front zone (0-150mm) has a temperature control of 10℃; the rear zone (150-500mm) has a temperature control of 15℃. The total residence time of the materials in the static mixer is 5s. Materials A and B are initially mixed in the static mixer, and phthalic anhydride and aluminum trichloride form an active complex.

[0079] The temperature of the pipeline reactor is 25°C, and the residence time of the material in the pipeline reactor is 50s. The main reaction occurs in the pipeline reactor, where the para-carbon atom of tert-pentanebenzene attacks the acyl carbon of phthalic anhydride to generate the target intermediate.

[0080] (3) Post-processing The crude reaction product was continuously pumped into a continuous acid hydrolysis tower, where it was contacted countercurrently with a 6wt% hydrochloric acid solution. The pH of the material at the outlet of the continuous acid hydrolysis tower was controlled to be 3 using an online pH meter. The aqueous phase after acid hydrolysis was precipitated with diethyl ether to recover ytterbium trifluoromethanesulfonate. The organic phase after acid hydrolysis was continuously fed into a countercurrent water washing tower, where it was contacted countercurrently with washing water for washing. The washing temperature was controlled at 85℃ and the washing time was 30 min. After washing, the material was passed through a continuous alkali dissolution column and a continuous acid washing column to remove impurities. The solids were then collected by filtration. After washing, the solids were dried under vacuum at 80℃ with a vacuum degree controlled at 0.09 MPa to obtain 2-(4'-pentylbenzoyl)benzoic acid.

[0081] In the continuous acidolysis process, the mass flow ratio of the crude reaction solution to hydrochloric acid is 1:3.2.

[0082] The mass ratio of the aqueous phase to diethyl ether after acid hydrolysis is 10:40.

[0083] In countercurrent washing, the mass flow ratio of the acid-hydrolyzed organic phase to the washing water is 1:1.1.

[0084] A 6 wt% sodium hydroxide solution was used in the continuous alkali dissolution column, and the mass ratio of the washed material to the sodium hydroxide solution was 6:1.

[0085] A 6 wt% hydrochloric acid solution was used in the continuous pickling column, and the mass ratio of the washed material to the hydrochloric acid solution was 6:1.

[0086] The purity of 2-(4'-pentylbenzoyl)benzoic acid in the product obtained in this embodiment was 93.21%, the yield was 93.59%, and the mass ratio of 2-(4'-tert-pentylbenzoyl)benzoic acid to 2-(4'-sec-pentylbenzoyl)benzoic acid in the product was 93.86:6.14.

[0087] Comparative Example 1 Comparative Example 1 uses the continuous synthesis method of 2-(4'-pentylbenzoyl)benzoic acid described in Example 2, except that the addition of N,N-dimethylaniline is omitted in the step of preparing the catalyst mixture, while the other steps are the same.

[0088] The purity of 2-(4'-pentylbenzoyl)benzoic acid in the product obtained from Comparative Example 1 was 87.25%, the yield was 89.18%, and the mass ratio of 2-(4'-tert-pentylbenzoyl)benzoic acid to 2-(4'-sec-pentylbenzoyl)benzoic acid in the product was 89.74:10.26.

[0089] Comparative Example 2 Comparative Example 1 uses the continuous synthesis method of 2-(4'-pentylbenzoyl)benzoic acid described in Example 2, except that the addition of N,N-dimethylaniline is omitted in the step of preparing the catalyst mixture, while the other steps are the same.

[0090] The purity of 2-(4'-pentylbenzoyl)benzoic acid in the product obtained from Comparative Example 1 was 87.25%, the yield was 89.18%, and the mass ratio of 2-(4'-tert-pentylbenzoyl)benzoic acid to 2-(4'-sec-pentylbenzoyl)benzoic acid in the product was 89.74:10.26.

[0091] Comparative Example 3 Comparative Example 3 uses the continuous synthesis method of 2-(4'-pentylbenzoyl)benzoic acid described in Example 2. The difference is that the addition of N,N-dimethylaniline and ytterbium trifluoromethanesulfonate is omitted in the step of preparing the catalyst mixture. All other steps are the same.

[0092] The purity of 2-(4'-pentylbenzoyl)benzoic acid in the product obtained from Comparative Example 3 was 82.37%, the yield was 78.93%, and the mass ratio of 2-(4'-tert-pentylbenzoyl)benzoic acid to 2-(4'-sec-pentylbenzoyl)benzoic acid in the product was 83.91:16.09.

[0093] Comparative Example 4 Comparative Example 4 uses the continuous synthesis method of 2-(4'-pentylbenzoyl)benzoic acid described in Example 2. The difference is that in the step of preparing the catalyst mixture, the amount of anhydrous aluminum trichloride is increased from 200g to 350g, the addition of N,N-dimethylaniline and ytterbium trifluoromethanesulfonate is omitted, and the stirring time at 350rpm is set to 50min after all the anhydrous aluminum trichloride is added. All other steps are the same.

[0094] The purity of 2-(4'-pentylbenzoyl)benzoic acid in the product obtained from Comparative Example 4 was 92.06%, the yield was 91.38%, and the mass ratio of 2-(4'-tert-pentylbenzoyl)benzoic acid to 2-(4'-sec-pentylbenzoyl)benzoic acid in the product was 92.57:7.43.

[0095] It can be seen that Comparative Example 1 omitted the addition of N,N-dimethylaniline, and the content of the byproduct 2-(4'-sec-pentylbenzoyl)benzoic acid increased significantly, indicating that the combination of N,N-dimethylaniline and anhydrous aluminum chloride can reduce the yield of byproducts in the synthesis.

[0096] Comparative Example 2 omitted the addition of ytterbium trifluoromethanesulfonate, and the product yield was only 85.72%, significantly lower than the 96.24% of Example 2. This indicates that the addition of ytterbium trifluoromethanesulfonate to the catalyst composite solution can increase the yield of 2-(4'-pentylbenzoyl)benzoic acid. At the same time, the content of the byproduct 2-(4'-sec-pentylbenzoyl)benzoic acid increased, indicating that ytterbium trifluoromethanesulfonate can reduce the yield of byproducts in the synthesis to some extent.

[0097] Comparative Example 3 omitted the addition of N,N-dimethylaniline and ytterbium trifluoromethanesulfonate, resulting in a product yield of only 78.93%. Furthermore, the mass ratio of 2-(4'-tert-pentylbenzoyl)benzoic acid to 2-(4'-sec-pentylbenzoyl)benzoic acid was 83.91:16.09, leading to a higher content of the byproduct 2-(4'-sec-pentylbenzoyl)benzoic acid.

[0098] Comparative Example 4 omitted the addition of N,N-dimethylaniline and ytterbium trifluoromethanesulfonate, but increased the amount of anhydrous aluminum trichloride. Compared with Comparative Example 3, the product yield showed a relatively limited increase, and the content of the byproduct 2-(4'-sec-pentylbenzoyl)benzoic acid also decreased to some extent.

[0099] Unless otherwise stated, all percentages used in this invention are mass percentages.

[0100] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A continuous synthesis method for 2-(4'-pentylbenzoyl)benzoic acid, characterized in that, Includes the following steps: Continuous catalytic reaction and post-processing; The continuous catalytic reaction method is as follows: under a nitrogen atmosphere, material A and material B are simultaneously and continuously fed into a static mixer, with the front section temperature controlled at 0-10℃ and the rear section temperature controlled at 10-15℃; after mixing in the static mixer, the mixture enters a pipeline reactor, with the temperature controlled at 20-25℃, to continuously carry out the continuous catalytic reaction and continuously obtain a crude reaction solution; the crude reaction solution is then post-treated to obtain 2-(4'-pentylbenzoyl)benzoic acid; Material A consists of a catalyst mixture and phthalic anhydride; material B is tert-amylbenzene. The catalyst mixture consists of anhydrous aluminum trichloride, N,N-dimethylaniline, ytterbium trifluoromethanesulfonate, and chlorobenzene.

2. The continuous synthesis method of 2-(4'-pentylbenzoyl)benzoic acid according to claim 1, characterized in that, In the continuous catalytic reaction, the mass ratio of material A to material B fed into the static mixer per unit time is 25-30:2-3.

3. The continuous synthesis method of 2-(4'-pentylbenzoyl)benzoic acid according to claim 1, characterized in that, In the continuous catalytic reaction, the total residence time of material A and material B in the static mixer is 5-8 seconds; The residence time of the mixture in the pipeline reactor is 50-70 seconds.

4. The continuous synthesis method of 2-(4'-pentylbenzoyl)benzoic acid according to claim 1, characterized in that, The mass ratio of the catalyst mixture to phthalic anhydride in material A is 100:9-11; In the catalyst mixture, the mass ratio of anhydrous aluminum trichloride, N,N-dimethylaniline, ytterbium trifluoromethanesulfonate, and chlorobenzene is 50:34-36:7-9:500-550.

5. The continuous synthesis method of 2-(4'-pentylbenzoyl)benzoic acid according to claim 1, characterized in that, The post-treatment method is as follows: the crude reaction product solution is continuously introduced into a continuous acid hydrolysis tower and acidified by countercurrent contact with hydrochloric acid solution, and the pH of the material at the outlet of the continuous acid hydrolysis tower is controlled at 2-3; the aqueous phase after acid hydrolysis is precipitated with diethyl ether to recover ytterbium trifluoromethanesulfonate; the organic phase after acid hydrolysis is continuously introduced into a countercurrent water washing tower and water washed by countercurrent contact with washing water; the material after water washing is passed through a continuous alkali dissolution column and a continuous acid washing column in sequence to remove impurities, and the solids are separated and collected. The solids are washed and dried to obtain 2-(4'-pentylbenzoyl)benzoic acid.

6. The continuous synthesis method of 2-(4'-pentylbenzoyl)benzoic acid according to claim 4, characterized in that, In the post-treatment process, the concentration of the hydrochloric acid solution used in the continuous acidolysis tower is 4-6 wt%. The mass flow ratio of the crude product solution to the hydrochloric acid solution in the continuous acidolysis tower is 1:2.8-3.

2.

7. The continuous synthesis method of 2-(4'-pentylbenzoyl)benzoic acid according to claim 4, characterized in that, In the post-treatment, the temperature of the countercurrent water wash is 75-85℃, and the time is 25-35 minutes; The mass flow ratio of the acid-hydrolyzed organic phase to the washing water is 1:1-1.

2.

8. The continuous synthesis method of 2-(4'-pentylbenzoyl)benzoic acid according to claim 4, characterized in that, In the post-processing, a sodium hydroxide solution with a concentration of 5.5-6 wt% is used in a continuous alkali dissolution column, and the mass ratio of the washed material to the sodium hydroxide solution is 5.5-6:

1. A 5.5-6 wt% hydrochloric acid solution is used in the continuous pickling column, and the mass ratio of the washed material to the hydrochloric acid solution is 5.5-6:

1.

9. The continuous synthesis method of 2-(4'-pentylbenzoyl)benzoic acid according to claim 1, characterized in that, The catalyst mixture is prepared by dissolving N,N-dimethylaniline in chlorobenzene under a nitrogen atmosphere, cooling it to 0-5°C, and keeping it at that temperature; adding anhydrous aluminum trichloride while stirring, stirring until homogeneous, and then adding ytterbium trifluoromethanesulfonate while stirring until homogeneous to obtain the catalyst mixture.

10. The continuous synthesis method of 2-(4'-pentylbenzoyl)benzoic acid according to claim 9, characterized in that, The method for adding anhydrous aluminum trichloride is to divide the anhydrous aluminum trichloride into 3-4 equal parts, and add one part of anhydrous aluminum trichloride every 4-5 minutes until all the anhydrous aluminum trichloride has been added.

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