CN103896756A - Method of preparing o-benzoylbenzoic acid by acylation reaction of benzene and phthalic anhydride - Google Patents

Abstract

The invention relates to a process for preparing o-benzoylbenzoic acid through the acylation reaction of benzene and phthalic anhydride. The process uses highly active chloroaluminate ionic liquids to catalyze the acylation reaction of benzene and phthalic anhydride; the product is extracted from the ionic liquid catalyst by using an extractant The ionic liquid catalyst in the present invention can be reused efficiently, avoiding the pressure brought by the traditional catalyst anhydrous aluminum trichloride on the treatment of three wastes, and meeting the requirements of green environmental protection. In addition, the ionic liquid catalyst has adjustable acidity, good solubility, low vapor pressure, high thermal and chemical stability, and can be used repeatedly. It can not only overcome the shortcomings of the traditional anhydrous aluminum trichloride catalyst, such as cumbersome post-treatment process and high cost of three waste treatment, but also overcome the disadvantage that the anhydrous aluminum trichloride catalyst cannot be reused.

Description

A kind of method for preparing o-benzoylbenzoic acid by acylation reaction of benzene and phthalic anhydride

technical field

The invention belongs to the technical field of green chemical industry, and specifically relates to a process method for preparing o-benzoylbenzoic acid through the acylation reaction of benzene and phthalic anhydride catalyzed by a recyclable chloroaluminate ionic liquid.

Background technique

Phthaloylbenzoic acid (BBA) is an important dye and pharmaceutical intermediate, especially it is an intermediate in the synthesis of anthraquinone by phthalic anhydride. The process of synthesizing anthraquinone from benzene and phthalic anhydride is divided into two steps. First, the Friedel-Crafts acylation reaction of benzene and phthalic anhydride produces BBA, and then BBA is decomposed to obtain anthraquinone. At present, the industrial acylation reaction of benzene and phthalic anhydride uses anhydrous aluminum trichloride as a catalyst. This process needs to consume a large amount of aluminum trichloride, and the aluminum trichloride cannot be recovered after the reaction, and the aluminum-containing waste liquid is generated after hydrolysis. Difficult to handle, easy to corrode equipment, pollute the environment, and do not meet the requirements of green environmental protection.

There are literature reports about the preparation of o-benzoylbenzoic acid by the Friedel-Crafts acylation reaction of benzene and phthalic anhydride catalyzed by fluorine-containing acids and salts, heteropolyacid compounds, and ionic liquids. Patents US4379092, US4496760 and US4591460 are about fluorine-containing acids and salts catalyzing the Friedel-Crafts acylation reaction of benzene and phthalic anhydride, but the reaction is carried out at low temperature and high pressure, which makes the process consume a lot of energy, require high equipment, and process costs are high , In addition, the use of fluorine will also pollute the environment and destroy the ozone layer, which is not suitable for industrial production. Hao Suxia [Master's Thesis: Hebei University of Technology, 2010.5] studied the catalytic activity of phosphotungstic acid, phosphomolybdic acid and silicotungstic acid for this reaction. The results showed that the better catalyst was phosphotungstic acid, but the product under the action of this catalyst The yield of anisobenzoic acid is only 7.6%; in addition, although it is reported that chloroaluminate ionic liquid [Emim]Br- _AlCl3 catalyzes the Friedel-Crafts acylation reaction conditions of benzene and phthalic anhydride, the BBA yield reaches 88.4%, but After the reaction is completed, the reaction product can be obtained by adding water to the reaction solution to destroy the ionic liquid. The literature does not consider how to separate the product o-benzoylbenzoic acid from the ionic liquid without destroying the ionic liquid; the ionic liquid in the literature cannot be recycled and reused. Zhang Xinwei [Industrial Catalysis, 2008,16(8):54-60] reported the reaction of modified silica-supported ionic liquid to catalyze the synthesis of 2-(4-ethylbenzoyl)benzoic acid from ethylbenzene and phthalic anhydride. The catalyst has high activity, but the repeated use performance of the catalyst is not good, and the activity drops rapidly. When the catalyst is used for the third time, the selectivity of the product has dropped to about 50%.

Therefore, for the preparation of o-benzoylbenzoic acid by chloroaluminate ionic liquid catalyzed acylation reaction of benzene and phthalic anhydride, how to separate the product BBA from the ionic liquid and realize the high efficiency of the ionic liquid Recycling is an unsolved problem so far. The solution to the above problems is the prerequisite for the industrialization of the synthesis of BBA from the acylation reaction of benzene and phthalic anhydride catalyzed by chloroaluminate ionic liquids.

Contents of the invention

The purpose of the present invention is to provide recyclable chlorine for the problems that existing catalysts in the process of preparing o-benzoylbenzoic acid through the acylation reaction of benzene and phthalic anhydride catalyzed by aluminum trichloride cannot be recycled, corrode equipment, and pollute the environment. A technology for preparing o-benzoylbenzoic acid through the acylation reaction of benzene and phthalic anhydride catalyzed by aluminate ionic liquid. The process uses highly active chloroaluminate ionic liquid to catalyze the acylation reaction of benzene and phthalic anhydride; an extractant is used to extract the product from the ionic liquid catalyst to separate the product from the catalyst; the ionic liquid catalyst can be reused efficiently.

Technical scheme of the present invention is:

A kind of processing method of preparing o-benzoylbenzoic acid by acylation reaction of benzene and phthalic anhydride, comprising the following steps:

1) Reaction process:

Under nitrogen protection, benzene, phthalic anhydride and ionic liquid catalyst are sequentially added into the reactor, the molar ratio of the reaction components is: benzene: ionic liquid: phthalic anhydride = 3-20:1-4:1, at 30°C-60°C, Under stirring and reflux conditions, react for 3h to 9h; after the reaction, the reaction solution is left to stand, and then the remaining benzene in the upper layer of the reaction is removed; the ionic liquid phase containing the product goes to the subsequent product separation and ionic liquid recovery steps;

2) Product separation and ionic liquid recovery:

The ionic liquid phase containing the product obtained in the previous step reaction is transferred into the liquid separator, and the extractant is added for extraction. The liquid obtained in the liquid separator is divided into upper and lower layers, and the lower layer is the ionic liquid phase, which is vacuum-dried to remove residual extraction agent, that is, the recovered ionic liquid is sealed for later use; the upper extractant phase obtained during the extraction process is distilled under reduced pressure at a temperature of 50-80°C and a vacuum of 0.06MPa-0.09MPa to obtain a solid product o-phenylene Acylbenzoic acid; the extraction agent distilled under reduced pressure is recycled to the extraction process for reuse; the volume ratio of the amount of extraction agent added during the extraction process to the benzene added during the reaction is: extraction agent: benzene = 2 ~ 7: 1.

The extraction of the product o-benzoylbenzoic acid from the ionic liquid phase obtained after the reaction process step is one-stage extraction or multi-stage extraction.

The catalyst chloroaluminate ionic liquid is an imidazole chloroaluminate ionic liquid or a quaternary ammonium chloroaluminate ionic liquid.

The imidazole chloroaluminate ionic liquid is specifically: [Emim]Cl-XAlCl ₃ , [Pmim]Cl-XAlCl ₃ , [Bmim]Cl-XAlCl ₃ , [Pmim]Br-XAlCl ₃ or [Bmim]Br- XAlCl ₃ ; wherein, Emim is 1-ethyl-3-methylimidazolium cation, Pmim is 1-propyl-3-methylimidazolium cation, Bmim is 1-butyl-3-methylimidazolium cation, X=2.0 , 2.5 or 3.0.

The quaternary ammonium chloroaluminate ionic liquid catalyst specifically includes: Me ₃ NHCl-XAlCl ₃ or Et ₃ NHCl-XAlCl ₃ ; wherein, Me represents CH ₃ , Et represents CH ₃ CH ₂ ; X=2.0, 2.5 or 3.0.

The extractant is a mixed solvent composed of hydrocarbons and esters.

The hydrocarbons are cyclohexane, n-hexane, isohexane, n-heptane, isoheptane, n-octane, isooctane, methylene chloride, chloroform or tetrachloromethane.

The esters are ethyl formate, ethyl acetate or methyl acetate.

In the mixed solvent, the volume ratio of hydrocarbons to esters is preferably 1-3:1.

In the process method for preparing o-benzoylbenzoic acid by the acylation reaction of benzene and phthalic anhydride, the activity of the ionic liquid is restored, and the steps are as follows: after the recovered ionic liquid is reused many times, the catalytic activity decreases, and the lost The living ionic liquid was supplemented with aluminum trichloride to restore its activity. The specific process is: under the conditions of nitrogen protection and condensing reflux, anhydrous aluminum trichloride is added to the ionic liquid to be reactivated, and the reaction is carried out at a temperature of 60-80°C for 8h-12h, and then vacuum-dried to make the ionic liquid The liquid restores the activity; the molar amount of aluminum trichloride supplemented during the said ionic liquid reactivation process accounts for 7%-9% of the molar amount of aluminum trichloride in the ionic liquid catalyst to be reactivated.

The beneficial effects of the present invention are as follows:

1. The use of chloroaluminate ionic liquid as a catalyst for the acylation reaction of benzene and phthalic anhydride to prepare o-benzoylbenzoic acid avoids the pressure brought by the traditional catalyst anhydrous aluminum trichloride on the treatment of three wastes and meets the requirements of green environmental protection. In addition, the ionic liquid catalyst has adjustable acidity, good solubility, low vapor pressure, high thermal and chemical stability, and can be used repeatedly. It can not only overcome the shortcomings of the traditional anhydrous aluminum trichloride catalyst, such as cumbersome post-treatment process and high cost of three waste treatment, but also overcome the disadvantage that the anhydrous aluminum trichloride catalyst cannot be reused.

2. The used chloroaluminate ionic liquid has high catalytic activity. In the catalytic acylation reaction of benzene and phthalic anhydride, the reaction condition is mild, the catalytic activity is high, the product yield is high, and it can be used repeatedly. When the imidazole-based chloroaluminate ionic liquid is used as a catalyst for the reaction, the yield of o-benzoylbenzoic acid is much higher than that obtained in the background technology. The yield of o-benzoylbenzoic acid in this patented technology can reach 93.4%, and the selectivity of o-benzoylbenzoic acid can reach 100%, which has good industrial application prospects.

3. Using a mixed solvent as the extraction agent can well extract the product o-benzoylbenzoic acid from the ionic liquid, and realize the separation of the product from the ionic liquid without destroying the activity of the ionic liquid catalyst, thereby achieving The repeated reuse of ionic liquids has good industrial application prospects.

Detailed ways

The present invention is illustrated by the following examples, but the present invention is not limited to the following examples. Without departing from the purpose described before and after, all changes and implementations are included in the technical scope of the present invention.

According to the present invention, the product o-benzoylbenzoic acid is extracted from the ionic liquid phase obtained after the reaction process steps, which is one-stage extraction or multi-stage extraction; the ionic liquid phase after the last extraction is vacuum-dried to remove residual extraction Agent, that is, the recovered ionic liquid is obtained; the extractant phases of all levels are distilled under reduced pressure to obtain the solid product o-benzoylbenzoic acid. The multi-stage extraction means that the ionic liquid phase after the first extraction is subjected to the second extraction, the ionic liquid phase after the second extraction is subjected to the third extraction, and so on, the multi-stage extraction process is performed.

Example 1

Under nitrogen protection, benzene and phthalic anhydride synthesize o-benzoylbenzoic acid reaction: add 0.20mol benzene, 0.02mol phthalic anhydride, 0.04mol [Pmim] Br-2AlCl _ionic liquid in a 100ml three-necked flask, under stirring and reflux conditions, At 40°C, react for 5h. After the reaction is over, the reaction solution is left to stand, and the remaining benzene in the upper layer reaction is removed, and then used in the reaction process of synthesizing o-benzoylbenzoic acid; According to the volume ratio of 1:1, the extractant obtained by mixing it is extracted and separated, and each time 45ml of extractant is used for two-stage extraction operation. liquid phase, the upper layer is the upper extractant phase), and the product is extracted into the extractant phase. The extracted ionic liquid phase is vacuum-dried to remove residual extractant to obtain recovered ionic liquid. Extractant phase is that temperature is 50 ℃, and vacuum is 0.09MPa condition under reduced pressure distillation, obtains 4.25g o-benzoylbenzoic acid solids, adopts high performance liquid chromatography to carry out quantitative analysis to it and determine product yield, and its yield is 92.7%.

Example 2

Under the protection of nitrogen, the reaction of benzene and phthalic anhydride to synthesize o-benzoylbenzoic acid is carried out: add 0.06mol benzene, 0.02mol phthalic anhydride, 0.06mol [Emim]Cl-2.5AlCl ₃ ionic liquid in a 100ml three-necked flask, under stirring and reflux conditions , at 50°C, reacted for 4h, and the reaction ended. After the reaction solution was allowed to stand, the remaining benzene was removed, and then the ionic liquid phase containing the product was transferred into a separatory funnel, and extracted and separated using an extractant obtained by mixing n-heptane and ethyl acetate at a volume ratio of 2:1. Use 10ml of extractant each time to carry out a three-stage extraction operation, and extract the product into the extractant phase. The extracted ionic liquid phase is vacuum-dried to remove residual extractant to obtain recovered ionic liquid. The extractant phase was distilled under reduced pressure at a temperature of 60°C and a vacuum of 0.08 MPa to obtain 4.28 g of o-benzoylbenzoic acid solid, which was quantitatively analyzed by high performance liquid chromatography to determine the product yield, which was 93.4%.

Example 3

Carry out the reaction of benzene and phthalic anhydride to synthesize o-benzoylbenzoic acid under the protection of nitrogen: add 0.40mol benzene, 0.02mol phthalic anhydride, 0.02mol [Bmim] Br-3AlCl ionic liquid in a 100ml three _- necked flask, under stirring and reflux conditions, After reacting for 9 hours at 30°C, the reaction ended. After the reaction solution was allowed to stand, the remaining benzene was removed, and then the ionic liquid phase containing the product was transferred into a separatory funnel, and extracted and separated using an extractant obtained by mixing n-octane and ethyl acetate at a volume ratio of 3:1. Use 40ml of extractant each time to carry out two-stage extraction operation, and extract the product into the extractant phase. The extracted ionic liquid phase is vacuum-dried to remove residual extractant to obtain recovered ionic liquid. Extractant phase is that temperature is 70 ℃, and vacuum is 0.07MPa condition under reduced pressure distillation, obtains 4.18g o-benzoylbenzoic acid solid, adopts high performance liquid chromatography to carry out quantitative analysis to it and determine product yield, and its yield is 91.2%.

Example 4

(1). The recovered ionic liquid restores the activity

From the [Bmim]Br- _3AlCl3 ionic liquid recovered in Example 3, 0.016mol was added to a 100ml three-necked flask, and 0.004mol anhydrous aluminum trichloride was added simultaneously. After reacting for 10 h and then drying in vacuum, the recovered ionic liquid catalyst can be reactivated.

(2) The second use of ionic liquid catalyst:

The recovered catalyst recovered in (1) was added into a 100ml three-neck flask, and the reaction was carried out according to the material ratio and reaction conditions in Example 3. After the reaction was finished, the reaction solution was allowed to stand, and the remaining benzene was removed, and then the ionic liquid phase containing the product was moved into a separatory funnel, and the extractant obtained by mixing n-octane and ethyl acetate in a volume ratio of 3:1 was used. Two extractive separations were performed. The product was extracted into the extractant phase with 30ml extractant each time. This extraction phase is that temperature is 70 ℃, and vacuum is 0.07MPa condition under reduced pressure distillation, obtains 3.44g o-benzoylbenzoic acid solids, adopts high performance liquid chromatography to carry out quantitative analysis to it and determine product yield, and its yield is 90.9%. The extracted ionic liquid phase is vacuum-dried to remove residual extractant, which is the ionic liquid recovered after the second use.

(3). The third use of ionic liquid catalyst:

According to the method shown in (1), restore the activity of the ionic liquid recovered after the second use in (2), and use this catalyst for the reaction under the same conditions as (2), and perform the same extraction and separation process, The product o-benzoylbenzoic acid was obtained by vacuum distillation of the extractant phase, and its quantitative analysis was carried out by high performance liquid chromatography to determine the product yield, and the yield was 90.9%. The extracted ionic liquid phase is vacuum-dried to remove the residual extractant, which is the ionic liquid recovered for the third time.

(4). The fourth use of ionic liquid catalyst:

According to the method shown in (1), restore the activity of the ionic liquid recovered after the third use in (3), and use it to catalyze the reaction under the same conditions as (2), and perform the same extraction and separation process, The product o-benzoylbenzoic acid was obtained by vacuum distillation of the extractant phase, and its quantitative analysis was carried out by high performance liquid chromatography to determine the product yield, and the yield was 90.7%.

Example 5

Carry out the reaction of benzene and phthalic anhydride to synthesize o-benzoylbenzoic acid under the protection of nitrogen: add 0.30mol benzene, 0.02mol phthalic anhydride, 0.04mol [Pmim]Cl-3AlCl _ionic liquid in a 100ml three-necked flask, under stirring and reflux conditions, At 50°C, react for 4h. The reaction is over. After the reaction solution was allowed to stand, the remaining benzene was removed, and then the ionic liquid phase containing the product was transferred into a separatory funnel, and extracted and separated using an extractant obtained by mixing chloroform and methyl acetate at a volume ratio of 2:1. Use 30ml extractant each time to carry out two-stage extraction operation, and extract the product into the extractant phase. The extracted ionic liquid phase is vacuum-dried to remove residual extractant to obtain recovered ionic liquid. Extractant phase is that temperature is 80 ℃, and vacuum is 0.06MPa condition under reduced pressure distillation, obtains 4.16g o-benzoylbenzoic acid solid, adopts high performance liquid chromatography to carry out quantitative analysis to it and determine product yield, and its yield is 90.8%.

Example 6

Carry out the reaction of benzene and phthalic anhydride to synthesize o-benzoylbenzoic acid under the protection of nitrogen: add 0.20mol benzene, 0.02mol phthalic anhydride, 0.08mol Et ₃ NHCl–2AlCl ₃ ionic liquid in a 100ml three-necked flask, under stirring and reflux conditions, in 40°C, react for 5h, and the reaction ends. After the reaction solution was allowed to stand, the remaining benzene was removed, and then the ionic liquid phase containing the product was transferred into a separatory funnel, and extracted and separated using an extractant obtained by mixing isooctane and ethyl acetate at a volume ratio of 2:1. With 90ml extractant, carry out one extraction operation, the product is extracted into the extractant phase. The extracted ionic liquid phase is vacuum-dried to remove residual extractant to obtain recovered ionic liquid. The extractant phase was distilled under reduced pressure at a temperature of 60°C and a vacuum of 0.08 MPa, and quantitatively analyzed by high-performance liquid chromatography to generate 4.12 g of o-benzoylbenzoic acid with a yield of 89.9%.

Example 7

Carry out the reaction of benzene and phthalic anhydride to synthesize o-benzoylbenzoic acid under the protection of nitrogen: add 0.10mol benzene, 0.02mol phthalic anhydride, 0.04mol Me ₃ NHCl–3AlCl ₃ ionic liquid in a 100ml three-necked flask, under stirring and reflux conditions, in 60°C, react for 3h, and the reaction ends. After the reaction solution was allowed to stand, the remaining benzene was removed, and then the ionic liquid phase containing the product was transferred into a separatory funnel, and extracted and separated by an extractant obtained by mixing dichloromethane and methyl acetate at a volume ratio of 2:1. Use 30ml extractant each time to carry out two-stage extraction operation, and extract the product into the extractant phase. The extracted ionic liquid phase is vacuum-dried to remove residual extractant to obtain recovered ionic liquid. Extractant phase is that temperature is 80 ℃, and vacuum is 0.06MPa condition under reduced pressure distillation, obtains 4.09g o-benzoylbenzoic acid solid, adopts high performance liquid chromatography to carry out quantitative analysis to it and determine product yield, and its yield is 75.6%.

Example 8

(1). The recovered ionic liquid restores the activity

From the _Et3NHCl - _2AlCl3 ionic liquid recovered in Example 6, 0.076mol was added to a 100ml three-necked flask, and 0.012mol anhydrous aluminum trichloride was added simultaneously, under the conditions of nitrogen protection and reflux, at 60°C, React for 12 hours, and then vacuum-dry to restore the activity of the recovered ionic liquid catalyst.

(2). The second use of ionic liquid catalyst:

The catalyst recovered in (1) was added into a 100ml three-neck flask, and the reaction was carried out according to the material ratio and reaction conditions in Example 6. After the reaction was finished, the reaction solution was allowed to stand, and the remaining benzene was removed, and then the ionic liquid phase containing the product was moved into a separatory funnel, and the extractant obtained by mixing isooctane and ethyl acetate in a volume ratio of 2:1 was used for the extraction. Extraction and separation. With 85ml extractant, carry out one extraction operation, the product is extracted into the extractant phase. This extraction phase is that temperature is 60 ℃, and vacuum is 0.08MPa condition under reduced pressure distillation, obtains 4.03g o-benzoylbenzoic acid solid, adopts high performance liquid chromatography to carry out quantitative analysis to it and determine product yield, and its yield is 89.7%. The extracted ionic liquid phase is vacuum-dried to remove residual extractant, which is the ionic liquid recovered after the second use.

(3). The third use of ionic liquid catalyst:

According to the method shown in (1), restore the activity of the ionic liquid recovered after the second use in (2), and use this catalyst for the reaction under the same conditions as (2), and perform the same extraction and separation process, The product o-benzoylbenzoic acid was obtained by vacuum distillation of the extractant phase, and its quantitative analysis was carried out by high performance liquid chromatography to determine the product yield, and the yield was 89.6%. For the extracted ionic liquid phase, the residual extractant is removed by vacuum drying, which is the ionic liquid recovered for the third time.

(4). The fourth use of ionic liquid catalyst:

According to the method shown in (1), restore the activity of the ionic liquid recovered after the third use in (3), and use it to catalyze the reaction under the same conditions as (2), and perform the same extraction and separation process, The product o-benzoylbenzoic acid was obtained by vacuum distillation of the extractant phase, and its quantitative analysis was carried out by high performance liquid chromatography to determine the product yield, and the yield was 89.3%.

Example 9

Under the protection of nitrogen, the reaction of benzene and phthalic anhydride to synthesize o-benzoylbenzoic acid: add 0.30mol benzene, 0.02mol phthalic anhydride, 0.06mol Et ₃ NHCl–2.5AlCl ₃ ionic liquid in a 100ml three-necked flask, under stirring and reflux conditions, At 40°C, react for 7h, and the reaction ends. After the reaction solution was allowed to stand, the remaining benzene was removed, and then the ionic liquid phase containing the product was transferred into a separatory funnel, and extracted and separated using an extractant obtained by mixing cyclohexane and ethyl formate at a volume ratio of 2:1. Use 30ml extractant each time, carry out two extraction operations, and extract the product into the extractant phase. The extracted ionic liquid phase is vacuum-dried to remove residual extractant to obtain recovered ionic liquid. Extractant phase is that temperature is 70 ℃, and vacuum is 0.07MPa condition under reduced pressure distillation, obtains 4.13g o-benzoylbenzoic acid solid, adopts high performance liquid chromatography to carry out quantitative analysis to it and determine product yield, and its yield is 90.1%.

Matters not covered in the present invention are known technologies.

Claims (9)

1. a kind of processing method that benzene and phthalic anhydride acylation reaction prepares o-benzoylbenzoic acid is characterized in that comprising the following steps: 1) Reaction process: Under nitrogen protection, benzene, phthalic anhydride and ionic liquid catalyst are sequentially added into the reactor, the molar ratio of the reaction components is: benzene: ionic liquid: phthalic anhydride = 3-20:1-4:1, at 30°C-60°C, Under stirring and reflux conditions, react for 3h to 9h; after the reaction, the reaction solution is left to stand, and then the remaining benzene in the upper layer of the reaction is removed; the ionic liquid phase containing the product goes to the subsequent product separation and ionic liquid recovery steps; 2) Product separation and ionic liquid recovery: The ionic liquid phase containing the product obtained in the previous step reaction is transferred into the liquid separator, and the extractant is added for extraction. The liquid obtained in the liquid separator is divided into upper and lower layers, and the lower layer is the ionic liquid phase, which is vacuum-dried to remove residual extraction agent, that is, the recovered ionic liquid is sealed for later use; the upper extractant phase obtained during the extraction process is distilled under reduced pressure at a temperature of 50-80°C and a vacuum of 0.06MPa-0.09MPa to obtain a solid product o-phenylene Acylbenzoic acid; the extraction agent that is distilled under reduced pressure is recycled to the extraction process for reuse; the volume ratio of the amount of extraction agent added during the extraction process to the benzene added during the reaction is: extraction agent: benzene=2 ~ 7: 1; The extractant is a mixed solvent composed of hydrocarbons and esters. 2. benzene as claimed in claim 1 and phthalic anhydride acylation reaction prepare the processing method of o-benzoylbenzoic acid, it is characterized in that described from the ionic liquid phase that obtains after the reaction process step, extract product o-benzoyl Benzoic acid is one-stage extraction or multi-stage extraction. 3. benzene and phthalic anhydride acylation reaction prepare the processing method of o-benzoylbenzoic acid as claimed in claim 1, it is characterized in that described catalyst chloroaluminate ionic liquid is imidazoles chloroaluminate ionic liquid or quaternary ammonium salt Chloroaluminate-like ionic liquids. 4. benzene and phthalic anhydride acylation reaction as claimed in claim 3 prepare the process method of o-benzoylbenzoic acid, it is characterized in that described imidazoles chloroaluminate ionic liquid is specifically: [Emim]Cl-XAlCl ₃ , [Pmim]Cl-XAlCl ₃ , [Bmim]Cl-XAlCl ₃ , [Pmim]Br-XAlCl ₃ or [Bmim]Br-XAlCl ₃ ; where Emim is 1-ethyl-3-methylimidazolium cation, Pmim is 1-propyl-3-methylimidazolium cation, Bmim is 1-butyl-3-methylimidazolium cation, X=2.0, 2.5 or 3.0. 5. the process method of preparing o-benzoylbenzoic acid by acylation reaction of benzene and phthalic anhydride as claimed in claim 3, it is characterized in that described quaternary ammonium salt class chloroaluminate ionic liquid catalyst specifically comprises: Me ₃ NHCl--XAlCl ₃ or Et ₃ NHCl–XAlCl ₃ ; wherein, Me represents CH ₃ , Et represents CH ₃ CH ₂ ; X=2.0, 2.5 or 3.0. 6. benzene and phthalic anhydride acylation reaction prepare the processing method of o-benzoylbenzoic acid as claimed in claim 1, it is characterized in that described hydrocarbons are cyclohexane, normal hexane, isohexane, normal heptane, isohexane Heptane, n-octane, isooctane, methylene chloride, chloroform, or tetrachloromethane. 7. the process method that benzene and phthalic anhydride acylation reaction prepares o-benzoylbenzoic acid as claimed in claim 1 is characterized in that described esters are ethyl formate, ethyl acetate or methyl acetate. 8. The process for preparing o-benzoylbenzoic acid by acylation of benzene and phthalic anhydride as claimed in claim 1, characterized in that in the mixed solvent, the volume ratio of hydrocarbons and esters is preferably 1 to 3: 1. 9. the process method that benzene and phthalic anhydride acylation reaction prepares o-benzoylbenzoic acid as claimed in claim 1 is characterized in that also comprising ionic liquid reactivation step: under the condition of nitrogen protection, condensation reflux, anhydrous Add aluminum trichloride to the ionic liquid to be reactivated, react at a temperature of 60-80°C for 8h-12h, and then vacuum-dry to restore the activity of the ionic liquid; The molar amount of aluminum chloride accounts for 7% to 9% of the molar amount of aluminum trichloride in the ionic liquid catalyst to be reactivated.