阅读说明：本技术 一种联产单取代甲基苯甲酸和单取代苯二甲酸的方法 (Method for co-producing mono-substituted methyl benzoic acid and mono-substituted phthalic acid ) 是由 熊振华 贺逍俊 于 2019-08-30 设计创作，主要内容包括：本发明公开了一种联产单取代甲基苯甲酸和单取代苯二甲酸的方法,包括：(1)在催化剂作用下,向冰醋酸或醋酸水溶液与单取代二甲苯的混合物中连续通入含氧气体进行反应,通过控制含氧气体的通入量控制尾氧浓度在反应体系的爆炸下限以内,反应终点为95％以上的单取代二甲苯被氧化,得到第一反应液；(2)将第一反应液结晶过滤,得到第一滤液和第一滤饼,将第一滤饼洗涤、干燥,得到单取代甲基苯甲酸产品；(3)将第一滤液蒸馏回收溶剂醋酸,得到蒸馏残渣；(4)将蒸馏残渣与硝酸水溶液反应0.5～24小时,得到第二反应液；(5)将第二反应液进行结晶和过滤,得到第二滤液和单取代甲基苯甲酸、单取代苯二甲酸产品。本发明具有工艺简单、易于操作、绿色环保、经济效益好的优点。(The invention discloses a method for co-producing mono-substituted methyl benzoic acid and mono-substituted phthalic acid, which comprises the following steps: (1) under the action of a catalyst, continuously introducing oxygen-containing gas into glacial acetic acid or a mixture of an acetic acid aqueous solution and mono-substituted xylene for reaction, controlling the introduction amount of the oxygen-containing gas to control the tail oxygen concentration to be within the lower explosion limit of a reaction system, and oxidizing the mono-substituted xylene with the reaction end point of more than 95 percent to obtain a first reaction liquid; (2) crystallizing and filtering the first reaction liquid to obtain a first filtrate and a first filter cake, washing and drying the first filter cake to obtain a mono-substituted methyl benzoic acid product; (3) distilling the first filtrate to recover solvent acetic acid to obtain distillation residue; (4) reacting the distillation residue with a nitric acid aqueous solution for 0.5-24 hours to obtain a second reaction solution; (5) and crystallizing and filtering the second reaction solution to obtain a second filtrate and mono-substituted methylbenzoic acid and mono-substituted phthalic acid products. The method has the advantages of simple process, easy operation, environmental protection and good economic benefit.)

1. A method for co-producing mono-substituted methyl benzoic acid and mono-substituted phthalic acid is characterized by comprising the following steps:

(1) under the action of a catalyst, continuously introducing oxygen-containing gas into a mixture of glacial acetic acid or an acetic acid aqueous solution with the water mass fraction of 0.1-10% and mono-substituted xylene for reaction, controlling the tail oxygen concentration to be within the lower explosion limit of a reaction system by controlling the introduction amount of the oxygen-containing gas, wherein the mass ratio of the mono-substituted xylene to the glacial acetic acid or the acetic acid aqueous solution is 1: 2-20, the reaction temperature is 110-250 ℃, the reaction pressure is 0.1-3 MPa, and the mono-substituted xylene with the reaction end point of more than 95% is oxidized to obtain a first reaction solution;

(2) crystallizing and filtering the first reaction liquid obtained in the step (1) to obtain a first filtrate and a first filter cake, and washing and drying the first filter cake to obtain a mono-substituted methyl benzoic acid product;

(3) distilling the first filtrate obtained in the step (2) to recover solvent acetic acid to obtain distillation residues;

(4) reacting the distillation residue obtained in the step (3) with a nitric acid aqueous solution with the mass fraction of nitric acid being 15-65% according to the mass ratio of 1: 2-20 at 80-160 ℃ and 0.09-1.5MPa for 0.5-24 hours to obtain a second reaction solution;

(5) and (4) crystallizing and filtering the second reaction liquid obtained in the step (4) to respectively obtain a second filtrate and mono-substituted methylbenzoic acid and mono-substituted phthalic acid products.

2. The method for co-producing mono-substituted methylbenzoic acid and mono-substituted phthalic acid according to claim 1, wherein the oxygen content in the oxygen-containing gas is 15% by mass or more.

3. The method for co-producing mono-substituted methylbenzoic acid and mono-substituted phthalic acid according to claim 1, wherein the mono-substituted xylene has a structure represented by general formula (I), general formula (II), general formula (III), general formula (IV), general formula (V) or general formula (VI), wherein the substituent R is nitro, chlorine, bromine or fluorine.

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4. The method for co-producing mono-substituted methylbenzoic acid and mono-substituted phthalic acid according to claim 1, wherein the catalyst is a mixture of a metal salt and bromide, and the molar ratio of the metal salt to the bromide is 0.5-5: 1.

5. The method for co-producing mono-substituted methylbenzoic acid and mono-substituted phthalic acid according to claim 4, wherein the concentration of the metal element in the catalyst in the reaction solution is 0.1 to 2 wt%.

6. The method for Co-producing mono-substituted methylbenzoic acid and mono-substituted phthalic acid according to claim 4, wherein the metal salt is one or a mixture of oxides, organic salts and inorganic salts of Co, Cu, V, Ni, Zn, Mn, Fe, Cr, Ce, Zr, Ru and Hf.

7. The method for co-producing mono-substituted methylbenzoic acid and mono-substituted phthalic acid according to claim 4, wherein the metal salt is manganese acetate, cobalt acetylacetonate, hafnium acetate, tetraphenyl cobalt porphyrin, cobalt acetate, manganese phthalocyanine, nitric acidNickel, cobalt iso-octoate, CeO₂、ZrO₂、RuCl₃、Cr₂O₃、FeSO₄、ZnO₂、CuCl、V₂O₅One or a mixture of several of them.

8. The method for co-producing mono-substituted methylbenzoic acid and mono-substituted phthalic acid according to claim 4, wherein the bromide is one or a mixture of inorganic bromine salt, bromine, hydrobromic acid and brominated alkanes.

9. The method for co-producing mono-substituted methylbenzoic acid and mono-substituted phthalic acid according to claim 8, wherein the inorganic bromine salt is cobalt bromide or sodium bromide, and the brominated alkane is tetrabromoethane or dibromoethane.

10. The process for co-producing mono-substituted methylbenzoic acid and mono-substituted phthalic acid according to claim 1, wherein the second filtrate obtained in the step (5) is distilled, and the distillate is recycled to the step (4) for further reaction.

Technical Field

The invention relates to the technical field of fine chemical engineering, in particular to a method for co-producing mono-substituted methylbenzoic acid and mono-substituted phthalic acid.

Background

Methylbenzoic acids containing a nitro group or halogen on the benzene ring are important intermediates in the pesticide and pharmaceutical fields, and one of the preparation methods is the corresponding mono-substituted xylene oxidation method, including strong oxidant oxidation method (using H as described in JP 05132450)₂SO₄And stoichiometric CrO₃Oxidation of 2, 6-dimethylnitrobenzene), nitric acid oxidation, oxygen-containing gas oxidation. The nitric acid oxidation method consumes a large amount of nitric acid and discharges a large amount of NO_XAnd tail gas seriously pollutes the environment. The production method using oxygen-containing gas as oxidant is most green and environment-friendly. It is well known that the oxidation reaction scheme for monosubstituted xylenes is as follows:

the prior art has the following defects in the process of carrying out the reaction:

(1) after introducing nitro or halogen to the benzene ring, the reactivity of the methyl group on the benzene ring is reduced, and the initiation of the reaction is more difficult than that without a substituent. Therefore, the reaction generally requires the addition of a large amount of a reaction initiator. For example, in the patent CN106458843A, when 2, 6-dimethylnitrobenzene is oxidized to prepare 2-nitro-3-methylbenzoic acid, a large amount of acetaldehyde, propionaldehyde, paraldehyde, or methylethylketone is added as an initiator. This not only increases the production cost, but also introduces and generates new compounds in the reaction system, and increases the difficulty of subsequent solvent separation and recovery.

(2) The target product of the reaction is generally methyl benzoic acid (compound 4 or 9) containing a nitro group or halogen on the benzene ring, which is an intermediate product of the reaction. An intermediate product (compounds 2, 3, 7 and 8) in which a methyl group is oxidized to an alcohol or aldehyde before the target product is produced according to the above reaction scheme; after the target product is formed, another methyl group on the target product can be further oxidized into the corresponding intermediate of the aldehyde alcohol (compound 5, 6, 10 and 11), and finally phthalic acid (compound 12) containing one substituent on the benzene ring is obtained, and the oxidation product is extremely complex. In order to improve the selectivity of the target product, in patent CN106458843A for example, the general operation is to control the conversion of xylene (compound 1) containing a nitro group or halogen on the benzene ring of the raw material to be generally not more than 90%, more preferably to control the conversion of compound 1 to be not more than 70%, and most preferably to control the conversion of compound 1 to be not more than 50%. Although the selectivity of the intermediate product (compound 4 or 9) is increased by the operation, more intermediate products (compounds 2, 3, 7 and 8) with one methyl group oxidized into alcohol or aldehyde are generated at the same time at the cost of greatly reducing the conversion rate of raw materials, so that the subsequent separation and purification are difficult, the three wastes are large, and the final yield is reduced.

(3) The isolation of the desired product (compound 4 or 9) is usually carried out in the form of a crystallization followed by filtration. This process results in a large mixture of various oxidation reaction intermediates and oxidation products, unreacted starting materials, catalyst, solvent, and a large number of deep side reaction products such as esters and acetals, which are extremely complex in composition and a dark black liquid. Some of the published data shows that it is a theoretically infeasible operation to return to the reaction system for reuse, but will eventually result in the absence of these deep side reaction products exiting the system. The conventional treatment method is distillation, the solvent and unreacted raw materials are recovered, and the residual distillation residue is used as solid waste and sent to a solid waste center for treatment. According to the operation method in the prior art, under the normal condition, every 1 ton of target compound 4 or 9 is produced, 2-3 tons of distillation residues are produced, and the molar yield of the mono-substituted methyl benzoic acid is about 30% by taking the raw material mono-substituted dimethylbenzene as a reference after the recycling of the materials is considered. Because the distillation residues are subjected to high-temperature long-time reaction and distillation, and the content of aldehyde and alcohol in the reaction liquid is higher, a large amount of high-boiling-point ester formed by esterification of alcohol acid, high-boiling-point colored impurities formed by condensation of aldol and simple dimerization of aldehyde, and high-boiling-point biphenyl compounds formed by decarboxylation coupling of carboxyl exist in the distillation residues, and finally the distillation residues are dark brown solid wastes with an asphalt-like irritating smell, so that the remarkable environmental protection pressure is formed, and the production cost is increased. By taking a monosubstituted methyl benzoic acid device which produces 1000 tons/year per year as an example, the distillation residue which produces 2000-3000 tons/year is solid waste, and the environmental protection pressure is huge. Calculated according to the current 8000 yuan/ton of treatment cost of the high-concentration nitro-containing or halogen-containing solid waste, the treatment cost of the solid waste of each ton of mono-substituted methyl benzoic acid is 16000-24000 yuan, which accounts for more than 30% of the current sale price of the mono-substituted methyl benzoic acid, and the production cost is obviously increased.

Phthalic acid containing a nitro group or halogen on a benzene ring is also an important intermediate in the fields of pesticides and medicines, and the preparation method is usually prepared by carrying out nitration or halogenation reaction on the corresponding phthalic acid, so that the production process is complex, the pollution is serious, and the cost is high. Therefore, the air oxidation of the mono-substituted dimethylbenzene reduces the generation amount of solid wastes in the production process of the mono-substituted methylbenzoic acid on the premise of producing the mono-substituted methylbenzoic acid as much as possible, and simultaneously co-produces partial mono-substituted phthalic acid, so that the method is a continuous effort direction in the technical field of engineering and has extremely strong environmental protection significance and economic benefit.

Disclosure of Invention

The invention aims to solve the problems of the prior art and provides a method for co-producing mono-substituted methylbenzoic acid and mono-substituted phthalic acid, which has the advantages of simple process, easy operation, environmental protection and good economic benefit.

The technical scheme adopted by the invention for realizing the purpose is as follows: a method for co-producing mono-substituted methyl benzoic acid and mono-substituted phthalic acid comprises the following steps:

(1) under the action of a catalyst, continuously introducing oxygen-containing gas into a mixture of glacial acetic acid or an acetic acid aqueous solution with the water mass fraction of 0.1-10% and mono-substituted xylene for reaction, controlling the tail oxygen concentration to be within the lower explosion limit of a reaction system by controlling the introduction amount of the oxygen-containing gas, wherein the mass ratio of the mono-substituted xylene to the glacial acetic acid or the acetic acid aqueous solution is 1: 2-20, the reaction temperature is 110-250 ℃, the reaction pressure is 0.1-3 MPa, and the mono-substituted xylene with the reaction end point of more than 95% is oxidized to obtain a first reaction solution;

(2) crystallizing and filtering the first reaction liquid obtained in the step (1) to obtain a first filtrate and a first filter cake, and washing and drying the first filter cake to obtain a mono-substituted methyl benzoic acid product;

(3) distilling the first filtrate obtained in the step (2) to recover solvent acetic acid to obtain distillation residues;

(4) reacting the distillation residue obtained in the step (3) with a nitric acid aqueous solution with the mass fraction of nitric acid being 15-65% according to the mass ratio of 1: 2-20 at 80-160 ℃ and 0.09-1.5MPa for 0.5-24 hours to obtain a second reaction solution;

(5) and (4) crystallizing and filtering the second reaction liquid obtained in the step (4) to respectively obtain a second filtrate and mono-substituted methylbenzoic acid and mono-substituted phthalic acid products.

In a preferred embodiment of the present invention, the oxygen-containing gas contains oxygen in an amount of 15% by mass or more.

As a preferred embodiment of the invention, the mono-substituted xylene has a structure shown in a general formula (I), a general formula (II), a general formula (III), a general formula (IV), a general formula (V) or a general formula (VI), wherein a substituent R is nitro, chlorine, bromine or fluorine.

In a preferred embodiment of the invention, the catalyst is a mixture of a metal salt and a bromide, and the molar ratio of the metal salt to the bromide is 0.5-5: 1.

In a preferred embodiment of the present invention, the concentration of the metal element in the catalyst in the reaction solution is 0.1 to 2 wt% (wt%, mass percentage content).

In a preferred embodiment of the invention, the metal salt is one or a mixture of several of oxides, organic salts and inorganic salts of Co, Cu, V, Ni, Zn, Mn, Fe, Cr, Ce, Zr, Ru and Hf.

In a preferred embodiment of the present invention, the gold isThe metal salt is manganese acetate, cobalt acetylacetonate, hafnium acetate, tetraphenyl metal cobalt porphyrin, cobalt acetate, manganese phthalocyanine (CAS number: 14325-24-7), nickel nitrate, cobalt isooctanoate, CeO₂、ZrO₂、RuCl₃、Cr₂O₃、FeSO₄、ZnO₂、CuCl、V₂O₅One or a mixture of several of them.

As a preferred embodiment of the invention, the bromide is one or a mixture of several of inorganic bromine salt, bromine, hydrobromic acid and alkyl bromide.

In a preferred embodiment of the present invention, the inorganic bromine salt is cobalt bromide or sodium bromide, and the alkyl bromide is tetrabromoethane or dibromoethane.

In a preferred embodiment of the present invention, the second filtrate obtained in step (5) may be distilled, and the distillate may be recycled to step (4) to continue the reaction.

As introduced in the background, the oxidation reaction scheme for monosubstituted xylenes is as follows:

an intermediate product (compounds 2, 3, 7 and 8) in which one methyl group is oxidized into alcohol or aldehyde before the target product monosubstituted methylbenzoic acid 4 or 9 is generated according to the reaction process; after the target product is formed, another methyl group on the target product can be further oxidized into the corresponding intermediate of the aldehyde alcohol (compound 5, 6, 10 and 11), and finally phthalic acid (compound 12) containing one substituent on the benzene ring is obtained, and the oxidation product is extremely complex. In order to improve the selectivity of the target product, in patent CN106458843A for example, the general operation is to control the conversion of xylene (compound 1) containing a nitro group or halogen on the benzene ring of the raw material to be generally not more than 90%, more preferably to control the conversion of compound 1 to be not more than 70%, and most preferably to control the conversion of compound 1 to be not more than 50%. This increases the selectivity of the intermediate (compound 4 or 9), but at the expense of a large reduction in the conversion of the starting material, more intermediate (compounds 2, 3, 7 and 8) are formed in which one methyl group is oxidized to the alcohol or aldehyde, making subsequent isolation and purification difficult and the final yield reduced. The invention greatly increases the oxidation depth and enhances the reaction by controlling the oxidation reaction conditions, so that the conversion rate of the raw material mono-substituted dimethylbenzene is not lower than 95 percent, and the single-pass selectivity of the target product mono-substituted methylbenzoic acid 4 or 9 is reduced in the reaction process, but the invention has the following two obvious advantages:

(1) meanwhile, monosubstituted phthalic acid with high added value is by-produced, and the defect of reduction of single-pass selectivity of monosubstituted methylbenzoic acid is overcome;

(2) due to the enhanced oxidation depth, the content of the intermediate product alcohol and aldehyde (compounds 2, 3, 7 and 8, compounds 5, 6, 10 and 11) is obviously reduced, which is beneficial to reducing the separation difficulty in the subsequent separation process and simultaneously is more beneficial to reducing the generation amount of distillation residues in the solvent recovery process.

The isolation of the desired product (compound 4 or 9) is usually carried out in the form of a crystallization followed by filtration. This process results in a large mixture of various oxidation reaction intermediates and oxidation products, unreacted starting materials, catalyst, solvent, and a large number of deep side reaction products such as esters and acetals, which are extremely complex in composition and a dark black liquid. Some of the published data show that it can be reused in the reaction system, but it will eventually lead to the absence of these deep side reaction products in the system, which is a theoretically infeasible operation. The conventional treatment method is distillation, the solvent and unreacted raw materials are recovered, and the residual distillation residue is used as solid waste and sent to a solid waste center for treatment. According to the operating method of the prior art, normally, 2 to 3 tons of distillation residue are produced per 1 ton of the target compound 4 or 9. The residue is dark brown solid waste in the form of asphalt with irritant gas, has very complicated components, and has more than 50 compounds detected. The inventor determines that the main components are as follows through analysis:

(1) ester: any acid and any alcohol in the above reaction schemes can form the corresponding ester, including mono-and di-esters. The diester is an ester formed by the compound 12 and one or two of the compounds 2, 5, 7 and 10, and 8 diester compounds can be formed in total. The monoester is an ester formed by any one of the compounds 4, 5, 6, 9, 10, 11 and 12 and any one of the compounds 2, 5, 7 or 10, and 28 monoester compounds can be formed in total. That is, at least 36 kinds of esters may be formed in the oxidation process, and a part of diols may be present in the oxidation process, which makes the composition extremely complicated. During the actual analysis, most of the ester was detected and confirmed to be present.

(2) Dialdehydes or higher polymeric aldehydes, including dimeric, trimeric and higher polymeric compounds of compounds 3, 6, 8 and 11, more than 10 have been found;

(3) various high-boiling point intermediate products mainly comprise compounds 2-12.

As can be seen from the above-identified compound composition of the distillation residue, the distillation residue has complicated components and cannot be separated one by the conventional method. As such, the current method in industry is incineration. The inventor experimentally and creatively discovers that after the black viscous asphalt-shaped rectification residue is mixed with the nitric acid aqueous solution and reacts for a period of time, the solution can become a clear solution, and the main reason of the solution is that the following two chemical reactions occur in the acid system through analysis:

1. hydrolysis of the ester: esters are susceptible to hydrolysis under acidic conditions. The invention adopts nitric acid water solution, after a period of reaction, various esters generated under the high temperature condition in the distillation process can be hydrolyzed into corresponding alcohol and acid;

2. depolymerization of aldehyde: dimeric or polymeric aldehydes readily depolymerize to monomers under acidic conditions. The invention adopts nitric acid aqueous solution, after a period of reaction, the dimeric or polymer of various aldehydes generated under the high temperature condition in the distillation process can be hydrolyzed into corresponding aldehydes;

after the hydrolysis of the ester and the depolymerization reaction of the aldehyde are carried out, black viscous compounds in the system do not exist, all the black viscous compounds become various high-boiling point intermediate products in the oxidation process of the mono-substituted xylene, mainly comprise 2-12 compounds, and simultaneously comprise partial unreacted raw material compound 1. Nitric acid is an oxidizing agent, and can efficiently oxidize aldehydes and alcohols into corresponding carboxylic acids, and can also oxidize the remaining unreacted raw material compound 1 into the corresponding carboxylic acid.

After hydrolysis under the catalysis of the nitric acid and oxidation reaction for a period of time under the condition that the nitric acid is used as an oxidant, nitric acid oxidation reaction liquid is obtained, rectification residues with extremely complex components originally are converted into a mixture mainly containing a plurality of mono-substituted methylbenzoic acid (compounds 4 and 9) and mono-substituted phthalic acid (compound 12), and then the mixture can be separated on the basis of the existing refining method, such as the refining method described in CN108218710A, so that qualified mono-substituted methylbenzoic acid and mono-substituted phthalic acid products are obtained. Thus, the technical scheme of the invention converts the high boiling point distillation residue which can only be treated by burning into mono-substituted methyl benzoic acid and mono-substituted phthalic acid which have obvious economic value, thereby changing waste into valuable.

The definition characterizing the molar yield of each product is:

the yield of each mono-substituted methylbenzoic acid was the moles of each mono-substituted methylbenzoic acid obtained per mole of mono-substituted xylene charged to the oxidation reactor. Expressed as a percentage in the examples.

The yield of monosubstituted phthalic acid was the moles of monosubstituted xylene charged to the oxidation reactor. Expressed as a percentage in the examples.

Compared with the prior art, the invention has the following beneficial effects:

1. the method is simple and easy to operate. The oxidation process is carried out in two stages. In the first stage, by means of oxygen-containing gas oxidation, 95% or more of mono-substituted xylene is converted into a target product and various intermediate products without adding a promoter. And (3) carrying out simple solid-liquid separation on the oxidation reaction liquid to recover most of the monosubstituted methyl nitrobenzoic acid. And (2) carrying out simple distillation on the separated filtrate to recover the solvent, and then carrying out hydrolysis and secondary oxidation on the obtained distillation residues, wherein no organic solvent is added in the hydrolysis and secondary oxidation treatment process, and directly carrying out hydrolysis and oxidation on the distillation residues generated in the production process of the mono-substituted methylbenzoic acid in the nitric acid aqueous solution to obtain the mono-substituted methylbenzoic acid and mono-substituted phthalic acid products with high added values, wherein the amount of the nitric acid is small, and the method is simple and easy to operate.

2. The environmental protection effect is obvious. According to the current normal condition in the field, each 1 ton of mono-substituted methyl benzoic acid is produced, 2-3 tons of distillation residues are calculated and are all taken as solid wastes for incineration treatment. After the method disclosed by the invention is adopted, the generated distillation residues can be treated by more than 90.2%, which means that the solid waste amount is reduced by more than 90.2% after the distillation residues are treated by the method disclosed by the invention, and the environment-friendly effect is obvious.

3. The economic benefit is remarkable. The method has the advantages that 1 ton of target product mono-substituted methyl benzoic acid is produced through the air oxidation reaction of mono-substituted dimethylbenzene while remarkable environmental protection benefits are obtained, the mono-substituted methyl benzoic acid and the mono-substituted phthalic acid are recovered from distillation residue solid waste, the yield of oxidation products is over 96.7%, the mono-substituted methyl benzoic acid and the mono-substituted phthalic acid have important applications in the fields of medicines, pesticides and materials, the economic value is obvious, waste is turned into wealth, and the economic benefits are remarkable.

Detailed Description

The present invention will be described in further detail with reference to examples, but the present invention is not limited to the examples.

The monosubstituted xylenes in the examples have the structure of formula (I), formula (II), formula (III), formula (IV), formula (V), or formula (VI):

in the embodiment of the invention, intermittent operation is adopted, the oxidation reactor is a titanium high-pressure reaction kettle with the volume of 500mL, and the reaction temperature is cooperatively controlled by cooling a coil pipe and heating a jacket. The distillation residue reactor is a pressure-resistant oxidation reaction kettle with the volume of 500ml, and the reaction temperature is cooperatively controlled by means of coil cooling and jacket heating. The operation steps are as follows:

(1) adding mono-substituted xylene, glacial acetic acid or acetic acid aqueous solution and a mixture catalyst consisting of metal salt and bromide into an oxidation reactor, heating and boosting a reaction system to reaction temperature and pressure, then continuously introducing oxygen-containing gas for reaction, controlling the tail oxygen concentration to be within the lower explosion limit of the reaction system by controlling the introduction amount of the oxygen-containing gas, continuously sampling and analyzing in the reaction process, and stopping the reaction when an HPLC (high performance liquid chromatography) detection result shows that more than 95% of the mono-substituted xylene is oxidized to obtain a first reaction liquid;

(2) crystallizing and filtering the first reaction solution obtained in the step (1) to obtain a first filtrate and a first filter cake, and washing and drying the first filter cake to obtain a mono-substituted methyl benzoic acid product;

(3) adding the first filtrate obtained in the step (2) into a distillation residue reactor, and distilling to recover the solvent acetic acid to obtain black viscous distillation residue;

(4) and (4) adding a nitric acid aqueous solution into the distillation residue obtained in the step (3), starting stirring and heating, and carrying out esterification and oxidation reactions under the action of nitric acid at a set temperature to obtain a second reaction solution.

(5) And (4) crystallizing and filtering the second reaction liquid obtained in the step (4) to respectively obtain mono-substituted methyl benzoic acid and mono-substituted phthalic acid products and second filtrate. The second filtrate obtained in step (5) may be distilled, and the distilled fraction may be recycled to step (4) for further reaction.

Example 1

2-nitro-1, 4-xylene (general formula (I), R ═ NO) is added to the oxidation reactor₂)100g of glacial acetic acid and 200g of glacial acetic acid, wherein a mixture of manganese acetate and cobalt bromide in a molar ratio of 0.5:1 is used as a catalyst, the total concentration of cobalt and manganese elements in a reaction solution is 2.0 wt%, oxygen-enriched air with the oxygen content of 80% by mass is continuously introduced at the reaction temperature of 138 ℃ and the reaction pressure of 0.4MPa for reaction, after the reaction time is 40 minutes, the conversion rate of the obtained 2-nitro-1, 4-xylene is monitored to be 96.2%, the reaction is stopped to obtain a reaction solution, the reaction solution is crystallized and filtered to obtain a filtrate and a filter cake, and the filter cake is washed with acetic acid and then dried to obtain 41.3g of 3-nitro-4-methylbenzoic acid solid. Distilling the filtrate to recover acetic acid as solventTo obtain 90.8g of a black viscous residue, 226.9g of an aqueous nitric acid solution containing 63.8% by mass of nitric acid was added to the residue, and the mixture was reacted at 112 ℃ and 0.12MPa for 3 hours to obtain a reaction solution, which was crystallized and filtered to obtain 4.6g of 3-nitro-4-methylbenzoic acid, 26.0g of 2-nitro-4-methylbenzoic acid, and 53.7g of 2-nitro-1, 4-phthalic acid, respectively, and a filtrate. The filtrate was evaporated to dryness to obtain 4.4g of distillation residue, the amount of which was decreased by 95.2%. In the final product, the yield of 3-nitro-4-methylbenzoic acid was 38.3%, the yield of 2-nitro-4-methylbenzoic acid was 21.7%, the yield of 2-nitro-1, 4-phthalic acid was 38.4%, and the total yield of the three was 98.5%.

Example 2

50g of 2-chloro-1, 4-xylene (general formula (I), R ═ Cl), 250g of glacial acetic acid, the mixture of metal salt (mixture of cobalt acetylacetonate and hafnium acetate in a molar ratio of 10: 1) and sodium bromide in a molar ratio of 1:1 is used as a catalyst, the total concentration of cobalt and hafnium elements in the reaction solution is 2.0 wt%, under the reaction temperature of 245 ℃ and the reaction pressure of 3.0MPa, oxygen-deficient air with the mass percentage of 15 percent of oxygen is continuously introduced for reaction, after the reaction time is 60 minutes, the conversion of 2-chloro-1, 4-xylene was monitored to be 99.8%, the reaction was stopped to obtain a reaction solution, the reaction solution was crystallized and filtered to obtain a filtrate and a filter cake, and the filter cake was washed with acetic acid and dried to obtain 26.7g of a solid 3-chloro-4-methylbenzoic acid. The filtrate was distilled to recover the solvent acetic acid to give 38.1g of a black viscous residue, 304.4g of an aqueous nitric acid solution containing 30.6% by mass of nitric acid was added to the residue, and the mixture was reacted at 130 ℃ and 0.35MPa for 1 hour to give a reaction solution, which was crystallized and filtered to give 3.2g of 3-chloro-4-methylbenzoic acid, 16.9g of 2-chloro-4-methylbenzoic acid and 15.1g of 2-chloro-1, 4-phthalic acid, and a filtrate, respectively. The filtrate was evaporated to dryness to obtain 2.0g of distillation residue, the amount of which was reduced by 94.6%. In the final product, the yield of 3-chloro-4-methylbenzoic acid was 49.2%, the yield of 2-chloro-4-methylbenzoic acid was 27.8%, the yield of 2-chloro-1, 4-phthalic acid was 21.2%, and the total yield of the three was 98.2%.

Example 3

20g of 2-fluoro-1, 4-xylene (general formula (I) and R ═ F) and 300g of an aqueous acetic acid solution having a water mass fraction of 8.5% were charged into an oxidation reactor, the mixture of metal salt tetraphenyl metal cobalt porphyrin (CAS number: 14172-90-8) and tetrabromoethane in the molar ratio of 0.75:1 is used as catalyst, the concentration of cobalt element in the reaction liquid is 0.63 wt%, oxygen-enriched air with the mass percentage of 40 percent of oxygen is continuously introduced for reaction at the reaction temperature of 180 ℃ and the reaction pressure of 1.0MPa, after the reaction time is 120 minutes, the conversion of 2-fluoro-1, 4-xylene obtained by monitoring was 97.6%, the reaction was stopped to obtain a reaction solution, the reaction solution was crystallized and filtered to obtain a filtrate and a filter cake, and the filter cake was washed with acetic acid and dried to obtain 9.5g of a solid 3-fluoro-4-methylbenzoic acid. 17.7g of black viscous residue was obtained after distilling the filtrate to recover the solvent acetic acid, 319.2g of aqueous nitric acid solution containing 17.8% by mass of nitric acid was added to the residue to react at 90 ℃ and 0.1MPa for 20 hours to obtain a reaction solution, and the reaction solution was crystallized and filtered to obtain 1.1g of 3-fluoro-4-methylbenzoic acid, 5.9g of 2-fluoro-4-methylbenzoic acid and 9.3g of 2-fluoro-1, 4-phthalic acid, respectively, and a filtrate. The filtrate was evaporated to dryness to obtain 0.9g of distillation residue, the amount of which was reduced by 94.9%. In the final product, the yield of 3-fluoro-4-methylbenzoic acid was 42.7%, the yield of 2-fluoro-4-methylbenzoic acid was 23.7%, the yield of 2-fluoro-1, 4-phthalic acid was 31.3%, and the total yield of the three was 97.7%.

Example 4

Adding 16g of 2-bromo-1, 4-xylene (general formula (I) and R ═ Br) and 320g of acetic acid aqueous solution with the water mass fraction of 10 percent into an oxidation reactor, taking a mixture of metal salt (a mixture of cobalt acetate and manganese phthalocyanine (CAS:14325-24-7) in a molar ratio of 5: 1) and dibromoethane in a molar ratio of 1:1 as a catalyst, continuously introducing oxygen-enriched air with the oxygen mass percentage of 70 percent at the reaction temperature of 165 ℃ and the reaction pressure of 0.7MPa for reaction, monitoring the conversion rate of the 2-bromo-1, 4-xylene after the reaction time is 48 minutes to 97.1 percent, stopping the reaction to obtain reaction liquid, crystallizing and filtering the reaction liquid to obtain filtrate and filter cake, washing the filter cake with acetic acid and drying, 6.9g of a solid of 3-bromo-4-methylbenzoic acid was obtained. The filtrate was distilled to recover the solvent acetic acid to give 13.3g of a black viscous residue, 265.4g of an aqueous nitric acid solution containing 15.0% by mass of nitric acid was added to the residue, and the mixture was reacted at 80 ℃ and 0.09MPa for 24 hours to give a reaction solution, which was crystallized and filtered to give 0.8g of 3-bromo-4-methylbenzoic acid, 4.2g of 2-bromo-4-methylbenzoic acid and 7.2g of 2-bromo-1, 4-phthalic acid, respectively, and a filtrate. The filtrate was evaporated to dryness to obtain 0.7g of distillation residue, the amount of which was reduced by 94.4%. The final implementation effect is as follows: the yield of 3-bromo-4-methylbenzoic acid was 41.1%, the yield of 2-bromo-4-methylbenzoic acid was 22.6%, the yield of 2-bromo-1, 4-phthalic acid was 33.8%, and the total yield of the three was 97.6%.

Example 5

2-Nitro-1, 3-xylene (general formula (II), R ═ NO) was added to the oxidation reactor₂)40g of acetic acid aqueous solution with the water mass fraction of 6.5 percent, 320g of metal salt (cobalt acetate and CeO)₂A mixture composed of 3:1 by mol) and 40 wt% of hydrobromic acid by mol according to a 1.5:1 ratio is used as a catalyst, the total concentration of cobalt and cerium in a reaction solution is 1.37 wt%, oxygen-enriched air with the oxygen content of 50% by mass is continuously introduced at the reaction temperature of 145 ℃ and the reaction pressure of 1.5MPa for reaction, after the reaction time is 118 minutes, the conversion rate of 2-nitro-1, 3-xylene is monitored to be 96.4%, the reaction is stopped to obtain a reaction solution, the reaction solution is crystallized and filtered to obtain filtrate and filter cake, the filter cake is washed by acetic acid and then dried to obtain 16.8g of 2-nitro-6-methylbenzoic acid solid. The filtrate was distilled to recover the solvent acetic acid to give 35.9g of a black viscous residue, 251.1g of an aqueous nitric acid solution containing 29.2% by mass of nitric acid was added to the residue, and the mixture was reacted at 140 ℃ under a pressure of 0.50MPa for 2 hours to give a reaction solution, which was crystallized and filtered to give 12.6g of 2-nitro-6-methylbenzoic acid and 20.8g of 2-nitro-1, 3-phthalic acid, respectively, and a filtrate. The filtrate was evaporated to dryness to obtain 2.1g of distillation residue, the amount of which was reduced by 94.1%. The final implementation effect is as follows: the yield of 2-nitro-6-methylbenzoic acid was 60.1%, the yield of 2-nitro-1, 3-phthalic acid was 37.2%, and the total yield of the two was 97.3%.

Example 6

Feeding to an oxidation reactor30g of 2-chloro-1, 3-xylene (general formula (II): R ═ Cl), 300g of an aqueous acetic acid solution having a water mass fraction of 7.2%, and metal salts (cobalt acetate and ZrO) were added₂A mixture composed of 2:1 in a molar ratio) and bromine in a molar ratio of 1.75:1 as a catalyst, the total concentration of cobalt and zirconium elements in the reaction solution is 1.16 wt%, oxygen-deficient air with the mass percentage content of 18% is continuously introduced at the reaction temperature of 223 ℃ and the reaction pressure of 2.6MPa for reaction, after the reaction time is 158 minutes, the conversion rate of the obtained 2-chloro-1, 3-dimethylbenzene is 99.1% by monitoring, the reaction is stopped to obtain the reaction solution, the reaction solution is crystallized and filtered to obtain filtrate and filter cake, the filter cake is washed by acetic acid and then dried to obtain 15.3g of 2-chloro-6-methylbenzoic acid solid. The filtrate was distilled to recover the solvent acetic acid to give 23.8g of a black viscous residue, 261.9g of an aqueous nitric acid solution containing 21.6% by mass of nitric acid was added to the residue, and the mixture was reacted at 108 ℃ and 0.15MPa for 10 hours to give a reaction solution, which was crystallized and filtered to give 12.1g of 2-chloro-6-methylbenzoic acid and 10.5g of 2-chloro-1, 3-phthalic acid, respectively, and a filtrate. The filtrate was evaporated to dryness to obtain 1.5g of distillation residue, the amount of which was reduced by 93.8%. The final implementation effect is as follows: the yield of 2-chloro-6-methylbenzoic acid was 73.6%, the yield of 2-chloro-1, 3-phthalic acid was 24.5%, and the total yield of the two was 98.1%.

Example 7

To an oxidation reactor, 45g of 2-bromo-1, 3-xylene (general formula (II), R ═ Br), 270g of an aqueous acetic acid solution having a water mass fraction of 4.3%, and metal salts (cobalt acetate and RuCl) were added₃A mixture composed of bromine and tetrabromoethane in a molar ratio of 25: 1) and bromide (a mixture of bromine and tetrabromoethane) in a molar ratio of 2:1 as a catalyst, wherein the total concentration of cobalt and ruthenium in a reaction solution is 1.58 wt%, air is continuously introduced at a reaction temperature of 172 ℃ and a reaction pressure of 1.0MPa to perform a reaction, after the reaction time is 66 minutes, the conversion rate of 2-bromine-1, 3-xylene is monitored to be 97.3%, the reaction is stopped to obtain a reaction solution, the reaction solution is crystallized and filtered to obtain a filtrate and a filter cake, and the filter cake is washed with acetic acid and then dried to obtain 19.6g of 2-bromine-6-methylbenzoic acid solid. Distilling the filtrate to recover acetic acid as solvent to obtain black viscous residue 36.9g, adding nitre into the residue221.3g of aqueous nitric acid solution with an acid mass fraction of 29.9% was reacted at 120 ℃ and a pressure of 0.2MPa for 4 hours to obtain a reaction solution, and the reaction solution was crystallized and filtered to obtain 15.1g of 2-bromo-6-methylbenzoic acid and 19.5g of 2-bromo-1, 3-phthalic acid, respectively, and a filtrate. The filtrate was evaporated to dryness to obtain 2.4g of distillation residue, the amount of which was reduced by 93.5%. The final implementation effect is as follows: the yield of 2-bromo-6-methylbenzoic acid was 65.1%, the yield of 2-bromo-1, 3-phthalic acid was 32.6%, and the total yield of the two was 97.7%.

Example 8

25g of 2-fluoro-1, 3-xylene (general formula (II), R ═ F), 300g of aqueous acetic acid solution containing 1.5% by mass of water, and metal salts (cobalt isooctanoate and Cr) were added to the oxidation reactor₂O₃A mixture composed of 6:1 in a molar ratio) and 40 wt% of hydrobromic acid in a molar ratio of 2.25:1 as a catalyst, the total concentration of cobalt and chromium elements in the reaction solution was 0.94 wt%, air was continuously introduced at a reaction temperature of 160 ℃ and a reaction pressure of 1.2MPa to perform a reaction, after a reaction time of 84 minutes, the conversion of 2-fluoro-1, 3-xylene was monitored to be 96.9%, the reaction was stopped to obtain a reaction solution, the reaction solution was crystallized and filtered to obtain a filtrate and a filter cake, and the filter cake was washed with acetic acid and dried to obtain 11.3g of 2-fluoro-6-methylbenzoic acid solid. The filtrate was distilled to recover the solvent acetic acid to give 23.0g of a black viscous residue, 321.7g of an aqueous nitric acid solution containing 21.1% by mass of nitric acid was added to the residue, and the mixture was reacted at 105 ℃ under a pressure of 0.10MPa for 12 hours to give a reaction solution, which was crystallized and filtered to give 8.6g of 2-fluoro-6-methylbenzoic acid and 12.8g of 2-fluoro-1, 3-phthalic acid, respectively, and a filtrate. The filtrate was evaporated to dryness to obtain 1.5g of distillation residue, the amount of which was reduced by 93.3%. The final implementation effect is as follows: the yield of 2-fluoro-6-methylbenzoic acid was 62.8%, the yield of 2-fluoro-1, 3-phthalic acid was 34.6%, and the total yield of the two was 97.5%.

Example 9

4-Nitro-1, 3-xylene (formula (III), R ═ NO) is charged to the oxidation reactor₂)60g of acetic acid aqueous solution with the water mass fraction of 0.5 percent, 240g of metal salt (cobalt acetate and FeSO)₄By a molar ratio of 50:1Substance) and 40 wt% hydrobromic acid in a molar ratio of 2.5:1 as a catalyst, the total concentration of cobalt and iron elements in the reaction solution is 1.79 wt%, pure oxygen is continuously introduced at a reaction temperature of 110 ℃ and a reaction pressure of 0.1MPa for reaction, after the reaction time is 24 hours, the conversion rate of 4-nitro-1, 3-xylene is 95.2% by monitoring, the reaction is stopped to obtain the reaction solution, the reaction solution is crystallized and filtered to obtain a filtrate and a filter cake, the filter cake is washed with acetic acid and then dried to obtain 23.0g of a solid 3-methyl-4-nitrobenzoic acid. The filtrate was distilled to recover the solvent acetic acid to give 57.0g of a black viscous residue, 285.2g of an aqueous nitric acid solution containing 42.6% by mass of nitric acid was added to the residue, and the mixture was reacted at 140 ℃ and 0.7MPa for 6 hours to give a reaction solution, which was crystallized and filtered to give 2.4g of 3-methyl-4-nitrobenzoic acid, 12.9g of 2-nitro-5-methylbenzoic acid and 36.3g of 4-nitro-1, 3-phthalic acid, respectively, and a filtrate. The filtrate was evaporated to dryness to obtain 4.0g of distillation residue, the amount of which was reduced by 93.0%. The final implementation effect is as follows: the yield of 3-methyl-4-nitrobenzoic acid was 35.4%, the yield of 2-nitro-5-methylbenzoic acid was 18.0%, the yield of 4-nitro-1, 3-phthalic acid was 43.3%, and the total yield of the three was 96.7%.

Example 10

80g of 4-chloro-1, 3-xylene (general formula (III) and R ═ Cl), 240g of an aqueous acetic acid solution having a water mass fraction of 0.6%, and metal salts (cobalt acetate and ZnO) were added to the oxidation reactor₂A mixture composed of hydrobromic acid with a molar ratio of 4: 1) and 40 wt% are used as catalysts, the total concentration of cobalt and zinc elements in the reaction solution is 1.89 wt%, air is continuously introduced at a reaction temperature of 209 ℃ and a reaction pressure of 1.9MPa for reaction, after the reaction time is 42 minutes, the conversion rate of 4-chloro-1, 3-xylene is monitored to be 98.6%, the reaction is stopped to obtain a reaction solution, the reaction solution is crystallized and filtered to obtain a filtrate and a filter cake, and the filter cake is washed with acetic acid and then dried to obtain 39.6g of 3-methyl-4-chlorobenzoic acid solid. Distilling the filtrate to recover solvent acetic acid to obtain black viscous residue 65.2g, adding 47.7% nitric acid water solution 260.7g into the residue, reacting at 130 deg.C and 0.35MPa for 15 hr to obtain reaction solution, and reactingThe reaction solution was crystallized and filtered to obtain 3-methyl-4-chlorobenzoic acid (4.7 g), 2-chloro-5-methylbenzoic acid (24.9 g) and 4-chloro-1, 3-phthalic acid (30.5 g), respectively, and a filtrate. The filtrate was evaporated to dryness to obtain 4.8g of distillation residue, the amount of which was decreased by 92.7%. The final implementation effect is as follows: the yield of 3-methyl-4-chlorobenzoic acid was 45.6%, the yield of 2-chloro-5-methylbenzoic acid was 25.7%, the yield of 4-chloro-1, 3-phthalic acid was 26.7%, and the total yield of the three was 98.0%.

Example 11

100g of 4-bromo-1, 3-xylene (general formula (III) and R ═ Br) and 200g of an aqueous acetic acid solution having a water mass fraction of 0.2% were charged into an oxidation reactor, taking a mixture of metal salt (a mixture of cobalt acetate and nickel nitrate in a molar ratio of 30: 1) and 40 wt% of hydrobromic acid in a molar ratio of 3:1 as a catalyst, wherein the total concentration of cobalt and nickel elements in a reaction solution is 2.0 wt%, continuously introducing air to react at the reaction temperature of 186 ℃ and the reaction pressure of 1.2MPa for 180 minutes, the conversion rate of 4-bromo-1, 3-xylene obtained by monitoring was 97.8%, the reaction was stopped to obtain a reaction solution, the reaction solution was crystallized and filtered to obtain a filtrate and a filter cake, and the filter cake was washed with acetic acid and dried to obtain 45.0g of a solid 3-methyl-4-bromobenzoic acid. The filtrate was distilled to recover the solvent acetic acid to give 80.0g of a black viscous residue, 240.0g of an aqueous nitric acid solution containing 57.1% by mass of nitric acid was added to the residue, and the mixture was reacted at 120 ℃ and 0.2MPa for 7 hours to give a reaction solution, which was crystallized and filtered to give 5.3g of 3-methyl-4-bromobenzoic acid, 28.1g of 2-bromo-5-methylbenzoic acid and 40.2g of 4-bromo-1, 3-phthalic acid, and a filtrate, respectively. The filtrate was evaporated to dryness to obtain 6.1g of distillation residue, the amount of which was decreased by 92.4%. The final implementation effect is as follows: the yield of 3-methyl-4-bromobenzoic acid was 43.4%, the yield of 2-bromo-5-methylbenzoic acid was 24.2%, the yield of 4-bromo-1, 3-phthalic acid was 30.4%, and the total yield of the three was 97.8%.

Example 12

50g of 4-fluoro-1, 3-xylene (general formula (III), R ═ F) and 250g of an acetic acid aqueous solution with the water mass fraction of 1.5 percent are added into an oxidation reactor, a mixture consisting of a metal salt (a mixture of cobalt acetate and CuCl in a molar ratio of 1: 1) and 40 wt% of hydrobromic acid in a molar ratio of 3.25:1 is used as a catalyst, the total concentration of cobalt and copper elements in a reaction solution is 1.68 wt%, air is continuously introduced at a reaction temperature of 176 ℃ and a reaction pressure of 1.0MPa for reaction, after the reaction time is 150 minutes, the conversion rate of 4-fluoro-1, 3-xylene is monitored to be 97.4 percent, the reaction solution is stopped, the reaction solution is crystallized and filtered to obtain a filtrate and a filter cake, the filter cake is washed by acetic acid and then dried to obtain 23.5g of a 3-methyl-4-fluorobenzoic acid solid. The filtrate was distilled to recover the solvent acetic acid to give 44.7g of a black viscous residue, 268.0g of a nitric acid aqueous solution containing 34.8% by mass of nitric acid was added to the residue, and the mixture was reacted at 140 ℃ under a pressure of 0.55MPa for 5 hours to give a reaction solution, which was crystallized and filtered to give 2.7g of 3-methyl-4-fluorobenzoic acid, 14.6g of 2-fluoro-5-methylbenzoic acid and 23.7g of 4-fluoro-1, 3-phthalic acid, respectively, and a filtrate. The filtrate was evaporated to dryness to obtain 3.5g of distillation residue, the amount of which was decreased by 92.1%. The final implementation effect is as follows: the yield of 3-methyl-4-fluorobenzoic acid was 42.3%, the yield of 2-fluoro-5-methylbenzoic acid was 23.5%, the yield of 4-fluoro-1, 3-phthalic acid was 32.0%, and the total yield of the three was 97.7%.

Example 13

Adding 5-nitro-1, 3-xylene (general formula (IV), R ═ NO) to an oxidation reactor₂)50g of glacial acetic acid, 250g of metal salt (cobalt acetate and V)₂O₅A mixture composed of 9:1 in a molar ratio) and 40 wt% of hydrobromic acid in a molar ratio of 3.5:1 as a catalyst, wherein the total concentration of cobalt and vanadium elements in a reaction solution is 1.68 wt%, continuously introducing air at a reaction temperature of 125 ℃ and a reaction pressure of 0.9MPa for reaction, monitoring the conversion rate of 5-nitro-1, 3-xylene to be 95.7% after the reaction time is 360 minutes, stopping the reaction to obtain a reaction solution, crystallizing and filtering the reaction solution to obtain a filtrate and a filter cake, washing the filter cake with acetic acid, and drying to obtain 20.0g of a solid 3-nitro-5-methylbenzoic acid. Distilling the filtrate to recover solvent acetic acid to obtain black viscous residue 46.4g, adding 35.9% nitric acid aqueous solution 255.0g into the residue, reacting at 132 deg.C and 0.45MPa for 5.5 hr to obtain reaction solution, crystallizing and filtering to obtain crystalsTo 14.5g 3-nitro-5-methylbenzoic acid and 28.4g 5-nitro-1, 3-benzenedicarboxylic acid, and the filtrate. The filtrate was evaporated to dryness to obtain 3.8g of a distillation residue, the amount of which was reduced by 91.9%. The final implementation effect is as follows: the yield of 3-nitro-5-methylbenzoic acid was 56.3%, the yield of 5-nitro-1, 3-phthalic acid was 40.7%, and the total yield of the two was 97.0%.

Example 14

60g of 5-chloro-1, 3-xylene (general formula (IV) and R ═ Cl) and 240g of glacial acetic acid are added into an oxidation reactor, a mixture of a metal salt (a mixture of cobalt acetate and manganese acetate in a molar ratio of 10: 1) and 40 wt% of hydrobromic acid in a molar ratio of 3.75:1 is used as a catalyst, the total concentration of cobalt and manganese elements in a reaction solution is 1.79 wt%, air is continuously introduced at a reaction temperature of 158 ℃ and a reaction pressure of 0.7MPa for reaction, after the reaction time is 120 minutes, the conversion rate of 5-chloro-1, 3-xylene is monitored to be 96.8%, the reaction is stopped to obtain a reaction solution, the reaction solution is crystallized and filtered to obtain a filtrate and a filter cake, and the filter cake is washed by acetic acid and then dried to obtain 26.4g of 3-chloro-5-methylbenzoic acid solid. The filtrate was distilled to recover the solvent acetic acid to give 53.6g of a black viscous residue, 241.1g of an aqueous nitric acid solution containing 40.4% by mass of nitric acid was added to the residue to react at 110 ℃ and 0.15MPa for 8.0 hours to give a reaction solution, and the reaction solution was crystallized and filtered to give 20.1g of 3-chloro-5-methylbenzoic acid and 29.9g of 5-chloro-1, 3-phthalic acid, respectively, and a filtrate. The filtrate was evaporated to dryness to obtain 4.5g of a distillation residue, the amount of which was reduced by 91.6%. The final implementation effect is as follows: the yield of 3-chloro-5-methylbenzoic acid was 62.5%, the yield of 5-chloro-1, 3-phthalic acid was 35.0%, and the total yield of the two was 97.5%.

Example 15

Adding 40g of 5-bromo-1, 3-xylene (general formula (IV) and R ═ Br) and 280g of glacial acetic acid into an oxidation reactor, taking a mixture of a metal salt (a mixture of cobalt acetate and manganese acetate in a molar ratio of 20: 1) and 40 wt% of hydrobromic acid in a molar ratio of 4.0:1 as a catalyst, wherein the total concentration of cobalt and manganese elements in a reaction solution is 1.47 wt%, continuously introducing air at a reaction temperature of 148 ℃ and a reaction pressure of 1.6MPa for reaction, monitoring the conversion rate of the 5-bromo-1, 3-xylene to be 96.5% after the reaction time is 140 minutes, stopping the reaction to obtain a reaction solution, crystallizing and filtering the reaction solution to obtain a filtrate and a filter cake, washing the filter cake with acetic acid and drying to obtain 16.4g of a solid 3-bromo-5-methylbenzoic acid. The filtrate was distilled to recover the solvent acetic acid to give 34.1g of a black viscous residue, 238.9g of an aqueous nitric acid solution containing 28.1% by mass of nitric acid was added to the residue, and the mixture was reacted at 100 ℃ and 0.5MPa for 7.5 hours to give a reaction solution, which was crystallized and filtered to give 12.4g of 3-bromo-5-methylbenzoic acid and 19.4g of 5-bromo-1, 3-phthalic acid, respectively, and a filtrate. The filtrate was evaporated to dryness to obtain 3.0g of distillation residue, the amount of which was reduced by 91.3%. The final implementation effect is as follows: the yield of 3-bromo-5-methylbenzoic acid was 60.7%, the yield of 5-bromo-1, 3-phthalic acid was 36.7%, and the total yield of the two was 97.4%.

Example 16

20g of 5-fluoro-1, 3-xylene (general formula (IV) and R ═ F) and 320g of glacial acetic acid are added into an oxidation reactor, a mixture of a metal salt (a mixture of cobalt acetate and manganese acetate in a molar ratio of 30: 1) and 40 wt% of hydrobromic acid in a molar ratio of 4.25:1 is used as a catalyst, the total concentration of cobalt and manganese elements in a reaction solution is 0.52 wt%, air is continuously introduced at a reaction temperature of 122 ℃ and a reaction pressure of 1.4MPa for reaction, after 80 minutes of reaction time, the conversion rate of 5-fluoro-1, 3-xylene is monitored to be 95.6%, the reaction is stopped to obtain a reaction solution, the reaction solution is crystallized and filtered to obtain a filtrate and a filter cake, and the filter cake is washed by acetic acid and then dried to obtain 8.2g of a solid 3-fluoro-5-methylbenzoic acid. The filtrate was distilled to recover the solvent acetic acid to give 19.6g of a black viscous residue, 294.6g of an aqueous nitric acid solution containing 19.0% by mass of nitric acid was added to the residue, and the mixture was reacted at 90 ℃ and 0.12MPa for 16 hours to give a reaction solution, which was crystallized and filtered to give 5.9g of 3-fluoro-5-methylbenzoic acid and 4.7g of 5-fluoro-1, 3-phthalic acid, respectively, and a filtrate. The filtrate was evaporated to dryness to obtain 1.8g of distillation residue, the amount of which was reduced by 91.0%. The final implementation effect is as follows: the yield of 3-fluoro-5-methylbenzoic acid was 55.7%, the yield of 5-fluoro-1, 3-phthalic acid was 41.2%, and the total yield of the two was 96.9%.

Example 17

Adding 3-nitro-1, 2-xylene (general formula (V), R ═ NO) to an oxidation reactor₂)80g of glacial acetic acid and 240g of glacial acetic acid, wherein a mixture of metal salt (a mixture of cobalt acetate and manganese acetate in a molar ratio of 1: 1) and 40 wt% of hydrobromic acid in a molar ratio of 4.5:1 is used as a catalyst, the concentration of the total concentration of cobalt and manganese elements in a reaction solution is 1.89 wt%, air is continuously introduced at the reaction temperature of 136 ℃ and the reaction pressure of 1.8MPa for reaction, after the reaction time is 90 minutes, the conversion rate of 3-nitro-1, 2-xylene is monitored to be 96.1%, the reaction is stopped to obtain a reaction solution, the reaction solution is crystallized and filtered to obtain a filtrate and a filter cake, and the filter cake is washed by acetic acid and then dried to obtain 32.9g of 2-methyl-3-nitrobenzoic acid solid. The filtrate was distilled to recover the solvent acetic acid to give 72.8g of a black viscous residue, 255.0g of an aqueous nitric acid solution containing 52.5% by mass of nitric acid was added to the residue to react at 125 ℃ and 0.25MPa for 5.0 hours to give a reaction solution, and the reaction solution was crystallized and filtered to give 3.6g of 2-methyl-3-nitrobenzoic acid, 19.4g of 2-nitro-6-methylbenzoic acid and 43.3g of 3-nitro-1, 2-phthalic acid, respectively, and a filtrate. The filtrate was evaporated to dryness to obtain 6.7g of distillation residue, the amount of which was decreased by 90.8%. The final implementation effect is as follows: the yield of 2-methyl-3-nitrobenzoic acid was 38.1%, the yield of 2-nitro-6-methylbenzoic acid was 20.3%, the yield of 3-nitro-1, 2-phthalic acid was 38.8%, and the total yield of the three was 97.2%.

Example 18

70g of 3-chloro-1, 2-xylene (general formula (V), R ═ Cl) and 280g of glacial acetic acid are added into an oxidation reactor, a mixture of a metal salt (a mixture of cobalt acetate and manganese acetate in a molar ratio of 1: 2) and 40 wt% of hydrobromic acid in a molar ratio of 4.75:1 is used as a catalyst, the total concentration of cobalt and manganese elements in a reaction solution is 1.79 wt%, air is continuously introduced at a reaction temperature of 156 ℃ and a reaction pressure of 1.5MPa for reaction, after the reaction time is 100 minutes, the conversion rate of the 3-chloro-1, 2-xylene is monitored to be 96.8%, the reaction is stopped to obtain a reaction solution, the reaction solution is crystallized and filtered to obtain a filtrate and a filter cake, and the filter cake is washed with acetic acid and then dried to obtain 30.7g of 2-methyl-3-chlorobenzoic acid solid. The filtrate was distilled to recover the solvent acetic acid to give 62.8g of a black viscous residue, 269.7g of a nitric acid aqueous solution containing 46.2% by mass of nitric acid was added to the residue to react at 118 ℃ and 0.2MPa for 1.5 hours to give a reaction solution, and the reaction solution was crystallized and filtered to give 3.5g of 2-methyl-3-chlorobenzoic acid, 18.6g of 2-chloro-6-methylbenzoic acid and 35.3g of 3-chloro-1, 2-phthalic acid, respectively, and a filtrate. The filtrate was evaporated to dryness to obtain 6.0g of distillation residue, the amount of which was decreased by 90.5%. The final implementation effect is as follows: the yield of 2-methyl-3-chlorobenzoic acid was 40.2%, the yield of 2-chloro-6-methylbenzoic acid was 21.9%, the yield of 3-chloro-1, 2-phthalic acid was 35.3%, and the total yield of the three was 97.4%.

Example 19

50g of 3-bromo-1, 2-xylene (general formula (V), R ═ Br) and 250g of an aqueous acetic acid solution having a water mass fraction of 0.8% were added to an oxidation reactor, the method comprises the steps of taking a mixture of metal salt (a mixture of cobalt acetate and manganese acetate in a molar ratio of 1: 3) and 40 wt% of hydrobromic acid in a molar ratio of 5.0:1 as a catalyst, wherein the total concentration of cobalt and manganese in a reaction solution is 1.68 wt%, continuously introducing air to react at the reaction temperature of 148 ℃ and the reaction pressure of 0.9MPa for 150 minutes, monitoring to obtain the conversion rate of the 3-bromo-1, 2-xylene to be 96.5%, stopping the reaction to obtain a reaction solution, crystallizing and filtering the reaction solution to obtain a filtrate and a filter cake, washing the filter cake with acetic acid, and drying to obtain 20.6g of a solid 2-methyl-3-bromobenzoic acid. The filtrate was distilled to recover the solvent acetic acid to give 42.7g of a black viscous residue, 298.6g of an aqueous nitric acid solution containing 33.5% by mass of nitric acid was added to the residue, and the mixture was reacted at 128 ℃ and 0.45MPa for 2.5 hours to give a reaction solution, which was crystallized and filtered to give 2.3g of 2-methyl-3-bromobenzoic acid, 12.4g of 2-bromo-6-methylbenzoic acid and 24.3g of 3-bromo-1, 2-phthalic acid, respectively, and a filtrate. The filtrate was evaporated to dryness to obtain 4.2g of distillation residue, the amount of which was decreased by 90.2%. The final implementation effect is as follows: the yield of 2-methyl-3-bromobenzoic acid was 39.4%, the yield of 2-bromo-6-methylbenzoic acid was 21.3%, the yield of 3-bromo-1, 2-phthalic acid was 36.7%, and the total yield of the three was 97.3%.

Example 20

40g of 3-fluoro-1, 2-xylene (general formula (V), R ═ F) and 300g of an aqueous acetic acid solution having a water mass fraction of 0.8% were charged into an oxidation reactor, the method comprises the steps of taking a mixture of metal salt (a mixture of cobalt acetate and manganese acetate in a molar ratio of 1: 1) and 40 wt% of hydrobromic acid in a molar ratio of 0.25:1 as a catalyst, wherein the total concentration of cobalt and manganese in a reaction solution is 1.42 wt%, continuously introducing air to react at the reaction temperature of 148 ℃ and the reaction pressure of 0.9MPa for 150 minutes, monitoring to obtain the conversion rate of the 3-fluoro-1, 2-dimethylbenzene of 96.5%, stopping reaction to obtain a reaction liquid, crystallizing and filtering the reaction liquid to obtain a filtrate and a filter cake, washing the filter cake with acetic acid, and drying to obtain 20.6g of 2-methyl-3-bromobenzoic acid solid. The filtrate was distilled to recover the solvent acetic acid to give 42.7g of a black viscous residue, to the residue was added 282.7g of an aqueous nitric acid solution containing 28.9% by mass of nitric acid, and the mixture was reacted at 160 ℃ and 1.5MPa for 0.5 hour to give a reaction solution, which was crystallized and filtered to give 2.2g of 2-methyl-3-fluorobenzoic acid, 11.9g of 2-fluoro-6-methylbenzoic acid and 18.4g of 3-fluoro-1, 2-phthalic acid, and a filtrate, respectively. The filtrate was evaporated to dryness to obtain 1.6g of distillation residue, the amount of which was decreased by 95.5%. The final implementation effect is as follows: the yield of 2-methyl-3-fluorobenzoic acid was 42.9%, the yield of 2-fluoro-6-methylbenzoic acid was 23.9%, the yield of 3-fluoro-1, 2-phthalic acid was 31.0%, and the total yield of the three was 97.8%.

Example 21

4-Nitro-1, 2-xylene (formula (VI), R ═ NO) is charged to the oxidation reactor₂) The method comprises the following steps of taking 230g of an acetic acid aqueous solution with the water mass fraction of 0.5%, taking a mixture of metal salt (a mixture of cobalt acetate and manganese acetate in a molar ratio of 3: 2) and 40 wt% of hydrobromic acid in a molar ratio of 2.15:1 as a catalyst, enabling the concentration of the total concentration of cobalt and manganese elements in a reaction solution to be 1.94 wt%, continuously introducing air at a reaction temperature of 142 ℃ and a reaction pressure of 1.0MPa for reaction, monitoring the conversion rate of 4-nitro-1, 2-xylene to be 96.3% after the reaction time is 210 minutes, stopping the reaction to obtain a reaction solution, crystallizing and filtering the reaction solution to obtain a filtrate and a filter cake, washing the filter cake with acetic acid, and drying to obtain 37.6g of 2-methyl-4-nitrobenzoic acid solid. Distilling the filtrate to recover the solventAcetic acid was added to give 81.1g of a black viscous residue, 243.4g of an aqueous nitric acid solution containing 57.8% by mass of nitric acid was added to the residue to react at 155 ℃ and 1.2MPa for 6 hours to obtain a reaction solution, and the reaction solution was crystallized and filtered to obtain 2-methyl-4-nitrobenzoic acid (g), 2-methyl-5-nitrobenzoic acid (g), and 4-nitro-1, 2-phthalic acid (g), 4.2g of which was obtained, and a filtrate, respectively. The filtrate was evaporated to dryness to obtain 5.4g of distillation residue, the amount of which was reduced by 93.4%. The final implementation effect is as follows: the yield of 2-methyl-4-nitrobenzoic acid was 38.7%, the yield of 2-methyl-5-nitrobenzoic acid was 20.8%, the yield of 4-nitro-1, 2-phthalic acid was 37.7%, and the total yield of the three was 97.2%.

Example 22

An oxidation reactor was charged with 110g of 4-chloro-1, 2-xylene (general formula (VI), R ═ Cl), 220g of an aqueous acetic acid solution having a water mass fraction of 0.1%, taking a mixture of metal salt (a mixture of cobalt acetate and manganese acetate in a molar ratio of 1: 3) and 40 wt% of hydrobromic acid in a molar ratio of 1.8:1 as a catalyst, wherein the total concentration of cobalt and manganese elements in a reaction solution is 2.00 wt%, continuously introducing air to react at the reaction temperature of 191 ℃ and the reaction pressure of 1.6MPa for 60 minutes, the conversion of 4-chloro-1, 2-xylene obtained by monitoring was 98.0%, the reaction was stopped to obtain a reaction solution, the reaction solution was crystallized and filtered to obtain a filtrate and a filter cake, and the filter cake was washed with acetic acid and dried to obtain 52.3g of a 2-methyl-4-chlorobenzoic acid solid. The filtrate was distilled to recover the solvent acetic acid to give 92.6g of a black viscous residue, 185.3g of an aqueous nitric acid solution containing 65.0% by mass of nitric acid was added to the residue, and the mixture was reacted at 145 ℃ and 1.0MPa for 8 hours to give a reaction solution, which was crystallized and filtered to give 6.1g of 2-methyl-4-chlorobenzoic acid, 32.7g of 2-methyl-5-chlorobenzoic acid and 46.4g of 4-chloro-1, 2-phthalic acid, and a filtrate, respectively. The filtrate was evaporated to dryness to obtain 5.8g of distillation residue, the amount of which was reduced by 93.8%. The final implementation effect is as follows: the yield of 2-methyl-4-chlorobenzoic acid was 43.8%, the yield of 2-methyl-5-chlorobenzoic acid was 24.5%, the yield of 4-chloro-1, 2-phthalic acid was 29.5%, and the total yield of the three was 97.9%.

Example 23

80g of 4-bromo-1, 2-xylene (general formula (VI) and R ═ Br) and 240g of an aqueous acetic acid solution having a water mass fraction of 2.4% were charged into an oxidation reactor, taking a mixture of metal salt (a mixture of cobalt acetate and manganese acetate in a molar ratio of 2: 1) and 40 wt% of hydrobromic acid in a molar ratio of 1.6:1 as a catalyst, wherein the total concentration of cobalt and manganese elements in a reaction solution is 1.89 wt%, continuously introducing air to react at the reaction temperature of 178 ℃ and the reaction pressure of 1.2MPa for 90 minutes, the conversion rate of 4-bromo-1, 2-xylene obtained by monitoring was 97.5%, the reaction was stopped to obtain a reaction solution, the reaction solution was crystallized and filtered to obtain a filtrate and a filter cake, and the filter cake was washed with acetic acid and dried to obtain 35.4g of a solid 2-methyl-4-bromobenzoic acid. The filtrate was distilled to recover the solvent acetic acid to give 64.9g of a black viscous residue, 259.6g of an aqueous nitric acid solution containing 47.5% by mass of nitric acid was added to the residue, and the mixture was reacted at 138 ℃ and 0.9MPa for 3 hours to give a reaction solution, which was crystallized and filtered to give 4.1g of 2-methyl-4-bromobenzoic acid, 21.9g of 2-methyl-5-bromobenzoic acid and 33.5g of 4-bromo-1, 2-phthalic acid, and a filtrate, respectively. The filtrate was evaporated to dryness to obtain 3.9g of distillation residue, the amount of which was reduced by 94.0%. The final implementation effect is as follows: the yield of 2-methyl-4-bromobenzoic acid was 42.5%, the yield of 2-methyl-5-bromobenzoic acid was 23.6%, the yield of 4-bromo-1, 2-phthalic acid was 31.7%, and the total yield of the three was 97.7%.

Example 24

60g of 4-fluoro-1, 2-xylene (general formula (VI), R ═ F) and 260g of an aqueous solution of acetic acid having a water mass fraction of 2.5% were charged into an oxidation reactor, the method comprises the steps of taking a mixture of metal salt (a mixture of cobalt acetate and manganese acetate in a molar ratio of 1: 2) and 40 wt% of hydrobromic acid in a molar ratio of 3.2:1 as a catalyst, wherein the total concentration of cobalt and manganese in a reaction solution is 1.75 wt%, continuously introducing air to react at the reaction temperature of 205 ℃ and the reaction pressure of 2.2MPa for 30 minutes, the conversion of 4-fluoro-1, 2-xylene obtained by monitoring was 98.4%, the reaction was stopped to obtain a reaction solution, the reaction solution was crystallized and filtered to obtain a filtrate and a filter cake, and the filter cake was washed with acetic acid and dried to obtain 30.1g of a 2-methyl-4-fluorobenzoic acid solid. The filtrate was distilled to recover the solvent acetic acid to give 50.8g of a black viscous residue, 254.0g of an aqueous nitric acid solution containing 38.6% by mass of nitric acid was added to the residue, and the mixture was reacted at 125 ℃ and 0.35MPa for 7 hours to give a reaction solution, which was crystallized and filtered to give 3.6g of 2-methyl-4-fluorobenzoic acid, 19.0g of 2-methyl-5-fluorobenzoic acid and 24.3g of 4-fluoro-1, 2-phthalic acid, and a filtrate, respectively. The filtrate was evaporated to dryness to obtain 4.0g of distillation residue, the amount of which was decreased by 92.2%. The final implementation effect is as follows: the yield of 2-methyl-4-fluorobenzoic acid was 45.2%, the yield of 2-methyl-5-fluorobenzoic acid was 25.4%, the yield of 4-fluoro-1, 2-phthalic acid was 27.3%, and the total yield of the three was 98.0%.