Method for preparing aromatic carboxylic acid by adopting deep eutectic solvent

Abstract

The invention discloses a method for preparing aromatic carboxylic acid by using a deep eutectic solvent, belongs to the technical field of organic synthesis, and particularly relates to a method for preparing aromatic carboxylic acid by using a deep eutectic solvent. Comprising the following steps: using at least one of N-hydroxyphthalimide, N-hydroxysuccinimide, N-chloro phthalimide and N-acetyl phthalimide as a catalyst, forming a catalytic system with a deep eutectic solvent, and catalyzing substituted aromatic hydrocarbon to generate aromatic carboxylic acid. According to the invention, N-hydroxyphthalimide and derivatives thereof are adopted as organic molecules and a deep eutectic solvent to form a metal-free and corrosion-free catalytic system, and the interaction of multiple hydrogen bonds in the system has the following effects: (1) accelerating the activation and dissolution of a substrate; and (2) promoting the N-hydroxyphthalimide and the derivatives thereof to generate active free radicals.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic synthesis, and particularly relates to a method for preparing aromatic carboxylic acids using deep eutectic solvents. Background Art

[0002] Aromatic carboxylic acids are widely used in multiple industries such as pharmaceuticals, chemicals, food, and feed additives, and almost penetrate all aspects of daily life. Alkyl aromatic hydrocarbons are mainly used in the production of oil products, polyesters, and various chemical intermediates, and their sources mainly rely on petroleum, which is a key raw material for preparing aromatic carboxylic acids.

[0003] As early as the beginning of the 20th century, industrial production processes for aromatic carboxylic acids had emerged. Initially, the nitric acid oxidation method was used. Subsequently, the technology gradually evolved to a liquid-phase oxidation process using transition metal salts as catalysts. In the 1940s, liquid-phase air oxidation processes for substances such as cyclohexane, butane, cumene, and p-xylene began to be industrially applied. In 1958, Mid-Century Company developed an innovative catalytic system that used soluble divalent cobalt, divalent manganese, and bromide salts, with acetic acid as the solvent, for the liquid-phase catalytic oxidation of substituted aromatics. This technology was later bought out and further optimized by Amoco Company, forming the currently widely used Amoco-MC process, especially in the process of oxidizing p-xylene to produce terephthalic acid. Although this catalyst system has high activity and high selectivity, its strong corrosiveness places high requirements on equipment.

[0004] On the other hand, N-hydroxyphthalimide (NHPI), as a nitrogen oxide radical precursor, can effectively catalyze the C-H bond activation of hydrocarbons and molecular oxygen under mild conditions. However, when NHPI is used alone, its activity is low and it is difficult to achieve an ideal catalytic effect, which limits its application range. To overcome this limitation, a common strategy is to combine NHPI with a transition metal promoter to promote the formation of PINO, thereby accelerating the catalytic oxidation reaction. However, this method relying on metal promoters is contrary to the concept of green chemistry of metal-free catalysis. Summary of the Invention

[0005] In view of the problems of high corrosiveness and high equipment requirements in the existing aromatic carboxylic acid preparation systems, the purpose of the present invention is to provide a method for preparing aromatic carboxylic acids using deep eutectic solvents. This method uses non-toxic and non-corrosive deep eutectic solvents, oxidizes substituted aromatics with these solvents and N-hydroxyphthalimide and its derivatives to prepare aromatic carboxylic acids, and the aromatic carboxylic acids have high purity and the preparation method has a high yield.

[0006] The present invention provides a method for preparing aromatic carboxylic acids using a deep eutectic solvent. At least one of N-hydroxyphthalimide, N-hydroxysuccinimide, N-chlorophthalimide, and N-acetylphthalimide is used as a catalyst, which forms a catalytic system with the deep eutectic solvent to catalyze substituted aromatic hydrocarbons to produce aromatic carboxylic acids.

[0007] The method includes the following steps: adding the catalyst, the deep eutectic solvent, and the substituted aromatic hydrocarbon into a reaction kettle, discharging air with an inert gas and then adjusting to a first pressure, heating to the reaction temperature, introducing high-purity air to a second reaction pressure, carrying out the reaction to produce a crude product of aromatic carboxylic acid, filtering, washing, and drying to obtain the aromatic carboxylic acid.

[0008] Preferably, the substituted aromatic hydrocarbon refers to benzene, naphthalene, or other aromatic compounds having one or more substituents, and the substituents are alkyl groups or functional groups having a methoxy group. The substituted aromatic hydrocarbons include one or more of toluene, o-xylene, m-xylene, p-xylene, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene, 1,2,4,5-tetramethylbenzene, dimethyl-substituted biphenyl, 2,6-dimethylnaphthalene, 2,6-diethylnaphthalene, 2,6-diisopropylnaphthalene, 2,7-dimethylnaphthalene, 2,3-dimethylnaphthalene, 2-methyl-6-acetylnaphthalene, and 5-hydroxymethylfurfural.

[0009] Preferably, the preparation method of the deep eutectic solvent includes the following steps: adding a hydrogen bond donor and a hydrogen bond acceptor into a reaction kettle, heating and reacting to obtain a uniformly transparent colorless solution, which is the deep eutectic solvent.

[0010] More preferably, the hydrogen bond donor is selected from one or more of polypropylene glycol, urea, 1,3-butanediol, acetamide, p-toluenesulfonic acid, oxalic acid, and citric acid; and / or the hydrogen bond acceptor is selected from one or more of tetrabutylammonium chloride, tetrabutylammonium bromide, and choline chloride.

[0011] More preferably, the molar ratio of the hydrogen bond donor to the hydrogen bond acceptor is (1:2)-(2:1).

[0012] More preferably, the temperature of the heating reaction is 80 °C and the time is 1 h.

[0013] Preferably, the molar ratio of the catalyst to the substituted aromatic hydrocarbon is (0.1-0.5):1.

[0014] Preferably, the mass ratio of the deep eutectic solvent to the substituted aromatic hydrocarbon is 20:1;

[0015] Preferably, the first reaction pressure is 1.5 MPa; and / or the reaction temperature is 190 °C; and / or the second reaction pressure is 2 MPa; and / or the reaction time is 3-6 h.

[0016] Compared with the prior art, the present invention has the following advantages and technical effects:

[0017] The present invention uses at least one of N-hydroxyphthalimide, N-hydroxysuccinimide, N-chlorophthalimide, and N-acetylphthalimide as a catalyst to form a metal-free and corrosion-free catalytic system with a deep eutectic solvent. The multiple hydrogen bond interactions in this system have the following effects: (1) The original intermolecular hydrogen bonds of the substrate molecules are disrupted by the newly formed hydrogen bond interactions between the deep eutectic solvent and the reaction substrate, thereby accelerating the dissolution and activation of the substrate; (2) The newly formed hydrogen bond interactions between the deep eutectic solvent and N-hydroxyphthalimide and its derivatives promote the activation of N-hydroxyphthalimide and its derivatives and the generation of PINO radical active substances. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0019] Figure 1 It is a process flow diagram of a method for preparing aromatic carboxylic acids using a deep eutectic solvent provided by the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] The various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, characteristics, and embodiments of the present invention.

[0021] It should be understood that the terms used in the present invention are only for describing specific embodiments and are not intended to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0022] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Although this invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of this invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the said documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0023] Without departing from the scope or spirit of this invention, various modifications and variations can be made to the specific embodiments of the specification of this invention, which will be apparent to those skilled in the art. Other embodiments obtained from the specification of this invention will be apparent to those skilled in the art. The specification and examples of this invention are merely exemplary.

[0024] Regarding the use of "comprising", "including", "having", "containing", etc. in this article, they are all open-ended terms, meaning including but not limited to.

[0025] The raw materials and reagents required in the embodiments of this invention are all obtained by purchasing from the market.

[0026] The embodiments of this invention provide a method for preparing aromatic carboxylic acids using deep eutectic solvents, which includes the following steps: using at least one of N-hydroxyphthalimide, N-hydroxysuccinimide, N-chlorophthalimide, and N-acetylphthalimide as a catalyst to form a metal-free and non-corrosive catalytic system with the deep eutectic solvent. This method includes the following steps: (1) adding the catalyst, deep eutectic solvent, and substituted aromatic hydrocarbon into a reaction kettle; (2) controlling the temperature in the reaction kettle to be maintained at 190 °C and the pressure to be maintained at 2 MPa, and then introducing air for reaction; (3) after reacting for 3 - 6 h, taking out the solid-liquid mixture from the reaction kettle, and the solid-liquid mixture is filtered, washed, and dried to obtain a crude aromatic carboxylic acid product. This invention uses a metal-free and non-corrosive catalytic system, which has low requirements for equipment, and the obtained aromatic carboxylic acids have high purity and high yield. Figure 1 It is a process flow chart of a method for preparing aromatic carboxylic acids using deep eutectic solvents provided by this invention.

[0027] Example 1

[0028] The preparation method of the deep eutectic solvent in this example is: adding 2000 g of polypropylene glycol (relative molecular mass of 2000, 1 mol) and 555.84 g (2 mol) of tetrabutylammonium chloride into the reaction kettle in a molar ratio of 1:2, and heating at 80 °C for 1 h to obtain a uniform, transparent, colorless solution, which is the deep eutectic solvent.

[0029] In this embodiment, p-xylene is used as the substrate raw material, and the method for preparing aromatic carboxylic acid using the above-mentioned deep eutectic solvent is as follows:

[0030] (1) Add 127.8 g (1.2 mol) of p-xylene, 2555.84 g of deep eutectic solvent, and 39.33 g (0.24 mol) of N-hydroxyphthalimide into a 5 L titanium reaction kettle;

[0031] (2) After purging the air in the kettle with argon, pressurize it to 1.5 MPa, adjust the back pressure valve behind the condenser to keep the pressure in the reaction kettle stable, start stirring (1000 rpm), and heat up (heating rate is 10 °C / min);

[0032] (3) When the reaction temperature reaches 190 °C, introduce high-purity air at a rate of 10 L / min until the pressure reaches 2 MPa, start timing, and react for 3 h;

[0033] (4) After the reaction is completed, terephthalic acid is produced. Filter the mixed solution containing crude terephthalic acid, wash it with distilled water at 80 °C, the amount of distilled water used is 500 g, weigh it after drying, dissolve the obtained product with dimethyl sulfoxide, and analyze it by high performance liquid chromatography to measure the purity of the product.

[0034] Example 2

[0035] In this embodiment, the preparation method of the deep eutectic solvent is as follows: Add 2000 g of polypropylene glycol (relative molecular mass is 2000, 1 mol) and 277.92 g (1 mol) of tetrabutylammonium chloride into the reaction kettle in a molar ratio of 1:1, heat it at 80 °C for 1 h to obtain a uniform, transparent, colorless solution, which is the deep eutectic solvent.

[0036] In this embodiment, p-xylene is used as the substrate raw material, and the method for preparing aromatic carboxylic acid using the above-mentioned deep eutectic solvent is as follows:

[0037] (1) Add 113.9 g (1.073 mol) of p-xylene, 2277.92 g of deep eutectic solvent, and 35.06 g (0.215 mol) of N-hydroxyphthalimide into a 5 L titanium reaction kettle;

[0038] (2) After purging the air in the kettle with argon, pressurize it to 1.5 MPa, adjust the back pressure valve behind the condenser to keep the pressure in the reaction kettle stable, start stirring (1000 rpm), and heat up (heating rate is 10 °C / min).

[0039] (3) When the reaction temperature reaches 190 °C, introduce high-purity air at a rate of 10 L / min until the pressure reaches 2 MPa, start timing, and react for 3 h;

[0040] (4) After the reaction is completed, terephthalic acid is produced. The mixed solution containing crude terephthalic acid is filtered, washed with distilled water at 80 °C, the amount of distilled water used is 500 g, weighed after drying, and the obtained product is dissolved in dimethyl sulfoxide and analyzed by high performance liquid chromatography to measure the purity of the product.

[0041] Example 3

[0042] In this example, the preparation method of the deep eutectic solvent is as follows: 2000 g of polypropylene glycol (relative molecular mass of 2000, 1 mol) and 138.96 g (0.5 mol) of tetrabutylammonium chloride are added to the reaction kettle in a molar ratio of 2:1, and heated at 80 °C for 1 h to obtain a uniform, transparent, colorless solution, which is the deep eutectic solvent.

[0043] In this example, using p-xylene as the substrate raw material, the method for preparing aromatic carboxylic acid using the above deep eutectic solvent is as follows:

[0044] (1) Add 106.95 g (1.007 mol) of p-xylene, 2138.96 g of the deep eutectic solvent, and 32.87 g (0.201 mol) of N-hydroxyphthalimide to a 5 L titanium reaction kettle;

[0045] (2) After purging the air in the kettle with argon, pressurize to 1.5 MPa, adjust the back pressure valve behind the condenser to keep the pressure in the reaction kettle stable, start stirring (1000 rpm), and heat up (heating rate is 10 °C / min);

[0046] (3) When the reaction temperature reaches 190 °C, introduce high-purity air at a rate of 10 L / min until the pressure reaches 2 MPa, start timing, and react for 3 h;

[0047] (4) After the reaction is completed, terephthalic acid is produced. The mixed solution containing crude terephthalic acid is filtered, washed with distilled water at 80 °C, the amount of distilled water used is 500 g, weighed after drying, and the obtained product is dissolved in dimethyl sulfoxide and analyzed by high performance liquid chromatography to measure the purity of the product.

[0048] Example 4

[0049] In this example, the preparation method of the deep eutectic solvent is as follows: 2000 g of polypropylene glycol (relative molecular mass of 2000, 1 mol) and 161.18 g (0.5 mol) of tetrabutylammonium bromide are added to the reaction kettle in a molar ratio of 2:1, and heated at 80 °C for 1 h to obtain a uniform, transparent, colorless solution, which is the deep eutectic solvent.

[0050] In this example, using p-xylene as the substrate raw material, the method for preparing aromatic carboxylic acid using the above deep eutectic solvent is as follows:

[0051] (1) Add 108.06 g (1.018 mol) of p-xylene, 2161.18 g of deep eutectic solvent, and 33.21 g (0.204 mol) of N-hydroxyphthalimide into a 5 L titanium reaction kettle.

[0052] (2) After purging the air in the kettle with argon, pressurize it to 1.5 MPa. Adjust the back pressure valve behind the condenser to keep the pressure in the reaction kettle stable. Then start stirring (1000 rpm) and heating (heating rate is 10 °C / min).

[0053] (3) When the reaction temperature reaches 190 °C, introduce high-purity air at a rate of 10 L / min until the pressure reaches 2 MPa. Start timing and react for 3 h.

[0054] (4) After the reaction is completed, terephthalic acid is produced. Filter the mixed solution containing crude terephthalic acid, wash it with distilled water at 80 °C, and the amount of distilled water used is 500 g. Dry it and weigh it. Dissolve the obtained product in dimethyl sulfoxide and analyze it by high performance liquid chromatography to measure the purity of the product.

[0055] Example 5

[0056] In this example, the preparation method of the deep eutectic solvent is as follows: Add 2000 g of polypropylene glycol (relative molecular mass is 2000, 1 mol) and 69.82 g (0.5 mol) of choline chloride into the reaction kettle in a molar ratio of 2:1, and heat it at 80 °C for 1 h to obtain a uniform, transparent, colorless solution, which is the deep eutectic solvent.

[0057] In this example, using p-xylene as the substrate raw material, the method for preparing aromatic carboxylic acid with the above deep eutectic solvent is as follows:

[0058] (1) Add 103.49 g (0.975 mol) of p-xylene, 2139.63 g of deep eutectic solvent, and 31.80 g (0.195 mol) of N-hydroxyphthalimide into a 5 L titanium reaction kettle.

[0059] (2) First, purge the air in the kettle with argon and then pressurize it to 1.5 MPa. Adjust the back pressure valve behind the condenser to keep the pressure in the reaction kettle stable. Then start stirring (1000 rpm) and heating (heating rate is 10 °C / min).

[0060] (3) When the reaction temperature reaches 190 °C, introduce high-purity air at a rate of 10 L / min until the pressure reaches 2 MPa. Start timing and react for 3 h.

[0061] (4) After the reaction is completed, terephthalic acid is generated. The mixed solution containing crude terephthalic acid is filtered, washed with distilled water at 80 °C, the amount of distilled water used is 500 g, weighed after drying, and the obtained product is dissolved in dimethyl sulfoxide and analyzed by high performance liquid chromatography to measure the purity of the product.

[0062] Example 6

[0063] In this example, the preparation method of the deep eutectic solvent is as follows: 900 g (15 mol) of urea and 2084.4 g (7.5 mol) of tetrabutylammonium chloride are added to the reaction kettle in a molar ratio of 2:1, and heated at 80 °C for 1 h to obtain a homogeneous, transparent, colorless solution, which is the deep eutectic solvent.

[0064] In this example, using p-xylene as the substrate raw material, the method for preparing aromatic carboxylic acid using the above deep eutectic solvent is as follows:

[0065] (1) 149.22 g (1.406 mol) of p-xylene, 2984.4 deep eutectic solvent, and 45.86 g (0.281 mol) of N-hydroxyphthalimide are added to a 5 L titanium reaction kettle;

[0066] (2) After purging the air in the kettle with argon, pressurize to 1.5 MPa, adjust the back pressure valve behind the condenser to keep the pressure in the reaction kettle stable, start stirring (1000 rpm), and raise the temperature (the heating rate is 10 °C / min);

[0067] (3) When the reaction temperature reaches 190 °C, high-purity air is introduced at a rate of 10 L / min until the pressure reaches 2 MPa, start timing, and react for 3 h;

[0068] (4) After the reaction is completed, terephthalic acid is generated. The mixed solution containing crude terephthalic acid is filtered, washed with distilled water at 80 °C, the amount of distilled water used is 500 g, weighed after drying, and the obtained product is dissolved in dimethyl sulfoxide and analyzed by high performance liquid chromatography to measure the purity of the product.

[0069] Example 7

[0070] In this example, the preparation method of the deep eutectic solvent is as follows: 1722 g (10 mol) of p-toluenesulfonic acid and 1389.6 g (5 mol) of tetrabutylammonium chloride are added to the reaction kettle in a molar ratio of 2:1, and heated at 80 °C for 1 h to obtain a homogeneous, transparent, colorless solution, which is the deep eutectic solvent.

[0071] In this example, using p-xylene as the substrate raw material, the method for preparing aromatic carboxylic acid using the above deep eutectic solvent is as follows:

[0072] (1) Add 155.58 g (1.465 mol) of p-xylene, 3111.6 g of deep eutectic solvent, and 47.81 g (0.293 mol) of N-hydroxyphthalimide into a 5 L titanium reaction kettle;

[0073] (2) After purging the air in the kettle with argon, pressurize it to 1.5 MPa. Adjust the back pressure valve behind the condenser to keep the pressure in the reaction kettle stable. Then start stirring (1000 rpm) and heating (heating rate is 10 °C / min);

[0074] (3) When the reaction temperature reaches 190 °C, introduce high-purity air at a rate of 10 L / min until the pressure reaches 2 MPa. Start timing and react for 3 h;

[0075] (4) After the reaction is completed, terephthalic acid is produced. Filter the mixed solution containing crude terephthalic acid, wash it with distilled water at 80 °C, with the amount of distilled water being 500 g. Dry it and weigh it. Dissolve the obtained product in dimethyl sulfoxide and analyze it by high performance liquid chromatography to measure the purity of the product.

[0076] Example 8

[0077] The preparation method of the deep eutectic solvent in this example is as follows: Add 2000 g of polypropylene glycol (relative molecular mass 2000, 1 mol) and 138.96 g (0.5 mol) of tetrabutylammonium chloride into the reaction kettle in a molar ratio of 2:1, and heat at 80 °C for 1 h to obtain a uniform, transparent, colorless solution, which is the deep eutectic solvent.

[0078] The method for preparing aromatic carboxylic acid using the above deep eutectic solvent with 2,6-dimethylnaphthalene as the substrate raw material in this example is as follows:

[0079] (1) Add 106.95 g (0.685 mol) of 2,6-dimethylnaphthalene, 2139.63 g of deep eutectic solvent, and 22.34 g (0.137 mol) of N-hydroxyphthalimide into a 5 L titanium reaction kettle;

[0080] (2) After purging the air in the kettle with argon, pressurize it to 1.5 MPa. Adjust the back pressure valve behind the condenser to keep the pressure in the reaction kettle stable. Then start stirring (1000 rpm) and heating (heating rate is 10 °C / min);

[0081] (3) When the reaction temperature reaches 190 °C, introduce high-purity air at a rate of 10 L / min until the pressure reaches 2 MPa. Start timing and react for 3 h;

[0082] (4) After the reaction is completed, 2,6-naphthalenedicarboxylic acid is produced. The mixed solution containing crude 2,6-naphthalenedicarboxylic acid is filtered, washed with distilled water at 80 °C, the amount of distilled water used is 500 g, dried and weighed. The obtained product is dissolved in dimethyl sulfoxide and analyzed by high performance liquid chromatography to measure the purity of the product.

[0083] Example 9

[0084] The preparation method of the deep eutectic solvent in this example is as follows: 2000 g of polypropylene glycol (relative molecular mass 2000, 1 mol) and 138.96 g (0.5 mol) of tetrabutylammonium chloride are added to the reaction kettle in a molar ratio of 2:1, and heated at 80 °C for 1 h to obtain a uniform, transparent and colorless solution, which is the deep eutectic solvent.

[0085] In this example, 2-methyl-6-acetylnaphthalene is used as the substrate raw material, and the method for preparing aromatic carboxylic acid using the above deep eutectic solvent is as follows:

[0086] (1) 106.95 g (0.581 mol) of 2-methyl-6-acetylnaphthalene, 2139.63 g of deep eutectic solvent and 18.96 g (0.116 mol) of N-hydroxyphthalimide are added to a 5 L titanium reaction kettle;

[0087] (2) After purging the air in the kettle with argon, pressurize to 1.5 MPa, adjust the back pressure valve behind the condenser to keep the pressure in the reaction kettle stable, start stirring (1000 rpm), and raise the temperature (heating rate is 10 °C / min);

[0088] (3) When the reaction temperature reaches 190 °C, high-purity air is introduced at a rate of 10 L / min until the pressure reaches 2 MPa, start timing, and react for 3 h;

[0089] (4) After the reaction is completed, 2,6-naphthalenedicarboxylic acid is produced. The mixed solution containing crude 2,6-naphthalenedicarboxylic acid is filtered, washed with distilled water at 80 °C, the amount of distilled water used is 500 g, dried and weighed. The obtained product is dissolved in dimethyl sulfoxide and analyzed by high performance liquid chromatography to measure the purity of the product.

[0090] Example 10

[0091] The preparation method of the deep eutectic solvent in this example is as follows: 2000 g of polypropylene glycol (relative molecular mass 2000, 1 mol) and 138.96 g (0.5 mol) of tetrabutylammonium chloride are added to the reaction kettle in a molar ratio of 2:1, and heated at 80 °C for 1 h to obtain a uniform, transparent and colorless solution, which is the deep eutectic solvent.

[0092] In this example, 1,2,4-trimethylbenzene was used as the substrate raw material, and the method for preparing aromatic carboxylic acids using the above-mentioned deep eutectic solvent was as follows:

[0093] (1) Add 106.95 g (0.890 mol) of 1,2,4-trimethylbenzene, 2139.63 g of deep eutectic solvent, and 29.03 g (0.178 mol) of N-hydroxyphthalimide into a 5 L titanium reaction kettle.

[0094] (2) After purging the air in the kettle with argon, pressurize it to 1.5 MPa, adjust the back pressure valve behind the condenser tube to keep the pressure in the reaction kettle stable, start stirring (1000 rpm), and heat up (heating rate is 10 °C / min).

[0095] (3) When the reaction temperature reaches 190 °C, introduce high-purity air at a rate of 10 L / min until the pressure reaches 2 MPa, start timing, and react for 3 h.

[0096] (4) After the reaction is completed, trimellitic acid is formed. Filter the mixed solution containing crude trimellitic acid, wash it with distilled water at 80 °C, the amount of distilled water used is 500 g, weigh it after drying, dissolve the obtained product in dimethyl sulfoxide, and analyze it by high performance liquid chromatography to measure the purity of the product.

[0097] The compositions of the deep eutectic solvents, substrates, and the purities and yields of the obtained aromatic carboxylic acids in Examples 1 - 10 are shown in Table 1.

[0098] Table 1

[0099]

[0100] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for preparing aromatic carboxylic acids using a deep eutectic solvent, characterized in that: At least one of N-hydroxyphthalimide, N-hydroxysuccinimide, N-chlorophthalimide and N-acetylphthalimide is used as a catalyst and a deep eutectic solvent to form a catalytic system to catalyze the substitution of aromatic hydrocarbons to generate aromatic carboxylic acids.

2. The method for preparing aromatic carboxylic acid using a deep eutectic solvent according to claim 1, characterized in that: The method comprises the following steps: adding the catalyst, deep eutectic solvent and substituted aromatic hydrocarbon into a reaction kettle, adjusting the pressure to a first reaction pressure after exhausting the air with an inert gas, heating the temperature to the reaction temperature and then introducing high-purity air to a second reaction pressure to react to generate a crude aromatic carboxylic acid, filtering, washing and drying to obtain the aromatic carboxylic acid.

3. The method for preparing aromatic carboxylic acid using a deep eutectic solvent according to claim 2, characterized in that: The preparation method of the deep eutectic solvent comprises the following steps: adding a hydrogen bond donor and a hydrogen bond acceptor into a reaction kettle, heating for reaction, and obtaining a uniform, transparent, colorless solution, which is the deep eutectic solvent.

4. The method for preparing aromatic carboxylic acid using a deep eutectic solvent according to claim 3, characterized in that: The hydrogen bond donor is selected from one or more of polypropylene glycol, urea, 1,3-butanediol, acetamide, p-toluenesulfonic acid, oxalic acid and citric acid; and / or, the hydrogen bond acceptor is selected from one or more of tetrabutylammonium chloride, tetrabutylammonium bromide and choline chloride.

5. The method for preparing aromatic carboxylic acid using a deep eutectic solvent according to claim 3, characterized in that: The molar ratio of the hydrogen bond donor to the hydrogen bond acceptor is (1:2) ～ (2∶1).

6. The method for preparing aromatic carboxylic acid using a deep eutectic solvent according to claim 3, characterized in that: The heating reaction was carried out at a temperature of 80° C. and for a time of 1 h.

7. The method for preparing aromatic carboxylic acid using a deep eutectic solvent according to claim 2, characterized in that: The molar ratio of the catalyst to the substituted aromatic hydrocarbon is (0.1-0.5):

1.

8. The method for preparing aromatic carboxylic acid using a deep eutectic solvent according to claim 2, characterized in that: The mass ratio of the deep eutectic solvent to the substituted aromatic hydrocarbon is 20:

1.

9. The method for preparing aromatic carboxylic acid using a deep eutectic solvent according to claim 2, characterized in that: The first reaction pressure is 1.5 MPa; the second reaction pressure is 2 MPa.

10. The method for preparing aromatic carboxylic acid using a deep eutectic solvent according to claim 2, characterized in that: The reaction temperature is 190° C. and the reaction time is 3 to 6 hours.

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