1. A method for efficiently and environmentally synthesizing 2-chloro-4-fluorobenzoic acid is characterized by comprising the following steps:

adding 2-chloro-4-fluorotoluene and nitric acid solution into an autoclave, introducing oxygen into the autoclave, carrying out high-pressure reflux reaction, filtering reaction liquid after the reaction is finished, transferring the filtered solid into a recrystallization kettle for recrystallization, then filtering, and drying the solid to obtain the 2-chloro-4-fluorobenzoic acid.

2. The method for efficiently and environmentally synthesizing 2-chloro-4-fluorobenzoic acid according to claim 1, which is characterized by comprising the following steps: the concentration of the nitric acid solution was 30 wt%.

3. The method for efficiently and environmentally synthesizing 2-chloro-4-fluorobenzoic acid according to claim 1, which is characterized by comprising the following steps: the mass ratio of the 2-chloro-4-fluorotoluene to the nitric acid solution is 0.3: (2.2-2.3).

4. The method for efficiently and environmentally synthesizing 2-chloro-4-fluorobenzoic acid according to claim 1, which is characterized by comprising the following steps: the temperature of the high-pressure reflux reaction is 50-60 ℃, the pressure of the introduced oxygen is 2.1-2.5MPa, and the time is 2-3 h.

5. The method for efficiently and environmentally synthesizing 2-chloro-4-fluorobenzoic acid according to claim 1, which is characterized by comprising the following steps: the high-pressure kettle is also filled with a catalytic filler, and the catalytic filler is antimony modified cerium zirconium oxide.

6. The method for efficiently and environmentally synthesizing 2-chloro-4-fluorobenzoic acid according to claim 1, which is characterized by comprising the following steps: the preparation method of the antimony modified cerium-zirconium oxide comprises the following steps: dissolving antimony acetate, cerium nitrate, zirconium nitrate and citric acid in deionized water, stirring and mixing at room temperature, then drying, and finally calcining to obtain the antimony modified cerium-zirconium oxide.

7. The method for efficiently and environmentally synthesizing 2-chloro-4-fluorobenzoic acid according to claim 1, which is characterized by comprising the following steps: the molar ratio of the antimony acetate to the cerium nitrate to the zirconium nitrate to the citric acid is (0.08-0.12): 0.2:0.4:1.

8. The method for efficiently and environmentally synthesizing 2-chloro-4-fluorobenzoic acid according to claim 1, which is characterized by comprising the following steps: the rotating speed of the stirring and mixing is 1000-2000rpm, and the stirring and mixing time is 4-6 h.

9. The method for efficiently and environmentally synthesizing 2-chloro-4-fluorobenzoic acid according to claim 1, which is characterized by comprising the following steps: the drying temperature is 100-110 ℃, and the drying time is 10-20 h.

10. The method for efficiently and environmentally synthesizing 2-chloro-4-fluorobenzoic acid according to claim 1, which is characterized by comprising the following steps: the calcination treatment comprises the following steps: firstly, heating to 200 ℃ at the speed of 10 ℃/min, preserving heat for 1h, then heating to 500 ℃ at the speed of 3 ℃/min, and preserving heat for 3-5 h.

Background

The 2-chloro-4-fluorobenzoic acid is an important medicine, pesticide and liquid crystal intermediate, and has good market prospect. The liquid crystal display is a color display device with wide application at present, the fluorine-containing liquid crystal material is a TFT-LCD thin film transistor mode and is a high-end mainstream display material at present, and the fluorine organic material has the advantages of strong hydrophobicity, radiation protection, high temperature resistance and the like, so that the development of the liquid crystal material is led. 2-chloro-4-fluorobenzoic acid is also commonly used in the preparation of fluorine-containing pesticides. The fluorine-containing pesticide has the advantages of high selectivity, high adaptability and broad spectrum, high added value, low dosage, low cost, low toxicity, low residue and environmental friendliness. Fluorine-containing drugs have many excellent properties: firstly, can improve the activity of medicine, increase the fat-soluble, effectively strengthen the bioavailability of medicine molecule, secondly can improve the metabolic stability of medicine, make the medicine effect more lasting to reduce and take medicine number of times or dose, thirdly after the fluorine atom is introduced to the medicine, can discern the difference of target, thereby provide more effective accurate treatment.

Along with the rapid development of the fluorine chemical industry, the 2-chloro-4-fluorobenzoic acid has good application prospect and larger rising space. At present, the production process of 2-chloro-4-fluorobenzoic acid at home and abroad mainly adopts potassium permanganate for oxidation, and the improved process generates more three wastes and has low yield. Therefore, the development of green and environment-friendly oxidation technology is the development direction of the product in the future.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: aiming at the defects in the prior art, the method for efficiently and environmentally synthesizing the 2-chloro-4-fluorobenzoic acid is provided, nitric acid is adopted to replace potassium permanganate, oxygen is introduced to adjust the pressure of a reaction system, the nitric acid can be recycled and reused, no high-salt wastewater is discharged, the production cost is reduced, the method is more environmentally friendly, the oxygen can oxidize nitrogen oxides generated by the reaction into the nitric acid, the comprehensive utilization is realized, and the generation of three wastes is reduced.

In order to solve the technical problems, the technical scheme of the invention is as follows:

a method for efficiently and environmentally synthesizing 2-chloro-4-fluorobenzoic acid comprises the following steps:

adding 2-chloro-4-fluorotoluene and nitric acid solution into an autoclave, introducing oxygen into the autoclave, carrying out high-pressure reflux reaction, filtering reaction liquid after the reaction is finished, transferring the filtered solid into a recrystallization kettle for recrystallization, then filtering, and drying the solid to obtain the 2-chloro-4-fluorobenzoic acid.

Preferably, the nitric acid solution has a concentration of 30 wt%.

Preferably, in the above technical means, the mass ratio of the 2-chloro-4-fluorotoluene to the nitric acid solution is 0.3: (2.2-2.3).

Preferably, the high-pressure reflux reaction is carried out at 50-60 ℃ under the pressure of 2.1-2.5MPa for 2-3 h.

Preferably, the autoclave is further filled with a catalytic filler, and the catalytic filler is antimony-modified cerium-zirconium oxide.

Preferably, in the above technical solution, the preparation method of the antimony-modified cerium-zirconium oxide comprises: dissolving antimony acetate, cerium nitrate, zirconium nitrate and citric acid in deionized water, stirring and mixing at room temperature, then drying, and finally calcining to obtain the antimony modified cerium-zirconium oxide.

Preferably, in the technical scheme, the molar ratio of the antimony acetate, the cerium nitrate, the zirconium nitrate and the citric acid is (0.08-0.12): 0.2:0.4:1.

Preferably, the rotation speed of the stirring and mixing is 1000-2000rpm, and the stirring and mixing time is 4-6 h.

Preferably, the drying temperature is 100-110 ℃, and the drying time is 10-20 h.

Preferably, in the above technical solution, the calcination treatment is: firstly, heating to 200 ℃ at the speed of 10 ℃/min, preserving heat for 1h, then heating to 500 ℃ at the speed of 3 ℃/min, and preserving heat for 3-5 h.

Due to the adoption of the technical scheme, the invention has the beneficial effects that:

the invention adopts nitric acid to replace potassium permanganate, the nitric acid can be recycled, high-salt wastewater is not discharged, the production cost is reduced, and the method is more environment-friendly. The invention also introduces oxygen in the reaction, which can oxidize nitrogen oxides generated in the reaction into nitric acid for comprehensive utilization and reduce the generation of three wastes.

According to the invention, a certain amount of catalytic filler is added into the autoclave, the catalytic filler is antimony-doped cerium-zirconium oxide, and the strong interaction between antimony and cerium oxide greatly promotes the migration of active oxygen, so that the oxidation efficiency of nitrogen oxide is improved, and the generation of three wastes is reduced.

Detailed Description

The invention is further illustrated by the following examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention.

Example 1

Dissolving 0.8mol of antimony acetate, 2mol of cerium nitrate, 4mol of zirconium nitrate and 10mol of citric acid in 1000ml of deionized water, stirring and mixing for 4h at the rotating speed of 1000rpm at room temperature, then drying for 10h at 100 ℃, finally heating to 200 ℃ at the speed of 10 ℃/min, preserving heat for 1h, then heating to 500 ℃ at the speed of 3 ℃/min, and preserving heat for 3h to prepare antimony modified cerium-zirconium oxide;

adding 30g of 2-chloro-4-fluorotoluene, 220g of 30 wt% nitric acid solution and 5g of antimony-modified cerium-zirconium oxide into an autoclave, introducing oxygen into the autoclave at the oxygen pressure of 2.1MPa, carrying out high-pressure reflux reaction at 50 ℃ for 2 hours, filtering reaction liquid after the reaction is finished, transferring the filtered solid into a recrystallization kettle for recrystallization, filtering, and drying the solid to obtain the 2-chloro-4-fluorobenzoic acid.

Example 2

Dissolving 1.2mol of antimony acetate, 2mol of cerium nitrate, 4mol of zirconium nitrate and 10mol of citric acid in 1000ml of deionized water, stirring and mixing for 6h at the rotating speed of 2000rpm at room temperature, then drying for 20h at 110 ℃, finally heating to 200 ℃ at the speed of 10 ℃/min, preserving heat for 1h, then heating to 500 ℃ at the speed of 3 ℃/min, and preserving heat for 5h to prepare antimony modified cerium-zirconium oxide;

adding 2-chloro-4-fluorotoluene 30g, nitric acid solution 30g30 wt% and antimony-modified cerium-zirconium oxide 10g into an autoclave, introducing oxygen into the autoclave at the oxygen pressure of 2.5MPa, carrying out high-pressure reflux reaction at 60 ℃ for 3 hours, filtering the reaction liquid after the reaction is finished, transferring the filtered solid into a recrystallization kettle for recrystallization, filtering, and drying the solid to obtain the 2-chloro-4-fluorobenzoic acid.

Example 3

Dissolving 1mol of antimony acetate, 2mol of cerium nitrate, 4mol of zirconium nitrate and 10mol of citric acid in 1000ml of deionized water, stirring and mixing for 4.5h at the rotating speed of 1500rpm at room temperature, then drying for 12h at 100 ℃, finally heating to 200 ℃ at the speed of 10 ℃/min, preserving heat for 1h, then heating to 500 ℃ at the speed of 3 ℃/min, and preserving heat for 3.5h to prepare antimony modified cerium-zirconium oxide;

adding 2-chloro-4-fluorotoluene, 225g of 30 wt% nitric acid solution and 6g of antimony-modified cerium-zirconium oxide into an autoclave, introducing oxygen into the autoclave at the oxygen pressure of 2.2MPa, carrying out high-pressure reflux reaction at 50 ℃ for 2 hours, filtering reaction liquid after the reaction is finished, transferring the filtered solid into a recrystallization kettle for recrystallization, filtering, and drying the solid to obtain the 2-chloro-4-fluorobenzoic acid.

Example 4

Dissolving 0.9mol of antimony acetate, 2mol of cerium nitrate, 4mol of zirconium nitrate and 10mol of citric acid in 1000ml of deionized water, stirring and mixing for 56 hours at the rotating speed of 1000rpm at room temperature, then drying for 14 hours at 105 ℃, finally heating to 200 ℃ at the speed of 10 ℃/min, preserving heat for 1 hour, then heating to 500 ℃ at the speed of 3 ℃/min, and preserving heat for 4 hours to prepare antimony modified cerium-zirconium oxide;

adding 2-chloro-4-fluorotoluene 30g, nitric acid solution 30g30 wt% and antimony-modified cerium-zirconium oxide 7g into an autoclave, introducing oxygen into the autoclave at the oxygen pressure of 2.3MPa, carrying out high-pressure reflux reaction at 60 ℃ for 2 hours, filtering the reaction liquid after the reaction is finished, transferring the filtered solid into a recrystallization kettle for recrystallization, filtering, and drying the solid to obtain the 2-chloro-4-fluorobenzoic acid.

Example 5

Dissolving 1.1mol of antimony acetate, 2mol of cerium nitrate, 4mol of zirconium nitrate and 10mol of citric acid in 1000ml of deionized water, stirring and mixing for 5.5h at the rotating speed of 2000rpm at room temperature, then drying for 16h at 110 ℃, finally heating to 200 ℃ at the speed of 10 ℃/min, preserving heat for 1h, then heating to 500 ℃ at the speed of 3 ℃/min, and preserving heat for 3h to prepare antimony modified cerium-zirconium oxide;

adding 2-chloro-4-fluorotoluene, 220g of 30 wt% nitric acid solution and 8g of antimony-modified cerium-zirconium oxide into an autoclave, introducing oxygen into the autoclave at the oxygen pressure of 2.2MPa, carrying out high-pressure reflux reaction at 50 ℃ for 2.5 hours, filtering reaction liquid after the reaction is finished, transferring the filtered solid into a recrystallization kettle for recrystallization, filtering, and drying the solid to obtain the 2-chloro-4-fluorobenzoic acid.

Example 6

Dissolving 1mol of antimony acetate, 2mol of cerium nitrate, 4mol of zirconium nitrate and 10mol of citric acid in 1000ml of deionized water, stirring and mixing for 5 hours at the rotating speed of 1500rpm at room temperature, then drying for 18 hours at 105 ℃, finally heating to 200 ℃ at the speed of 10 ℃/min, preserving heat for 1 hour, then heating to 500 ℃ at the speed of 3 ℃/min, and preserving heat for 4 hours to prepare antimony modified cerium-zirconium oxide;

adding 2-chloro-4-fluorotoluene 30g, nitric acid solution 30g30 wt% and antimony-modified cerium-zirconium oxide 10g into an autoclave, introducing oxygen into the autoclave at the oxygen pressure of 2.5MPa, carrying out high-pressure reflux reaction at 60 ℃ for 3 hours, filtering the reaction liquid after the reaction is finished, transferring the filtered solid into a recrystallization kettle for recrystallization, filtering, and drying the solid to obtain the 2-chloro-4-fluorobenzoic acid.

Comparative example 1

Dissolving 2mol of cerium nitrate, 4mol of zirconium nitrate and 10mol of citric acid in 1000ml of deionized water, stirring and mixing for 5h at the rotating speed of 1500rpm at room temperature, then drying for 18h at 105 ℃, finally heating to 200 ℃ at the speed of 10 ℃/min, preserving heat for 1h, then heating to 500 ℃ at the speed of 3 ℃/min, and preserving heat for 4h to obtain cerium-zirconium oxide;

adding 2-chloro-4-fluorotoluene 30g, nitric acid solution 30g30 wt% and cerium-zirconium oxide 10g into an autoclave, introducing oxygen into the autoclave at the oxygen pressure of 2.5MPa, carrying out high-pressure reflux reaction at 60 ℃ for 3h, filtering the reaction solution after the reaction is finished, transferring the filtered solid into a recrystallization kettle for recrystallization, filtering, and drying the solid to obtain the 2-chloro-4-fluorobenzoic acid.

Comparative example 2

Adding 2-chloro-4-fluorotoluene 30g and nitric acid solution 30g and 30 wt% 230g into an autoclave, introducing oxygen into the autoclave at the oxygen pressure of 2.5MPa, carrying out high-pressure reflux reaction at 60 ℃ for 3h, filtering the reaction solution after the reaction is finished, transferring the filtered solid into a recrystallization kettle for recrystallization, filtering, and drying the solid to obtain the 2-chloro-4-fluorobenzoic acid.

The yields of the objective products obtained in the above examples and comparative examples are shown in table 1.

TABLE 1

From the above test results, it can be seen that the addition of the catalytic filler in the autoclave improves the yield of the product to a certain extent, mainly because the catalytic filler can effectively adsorb the nitrogen oxide produced by the reaction, and the nitrogen oxide is oxidized into nitric acid by oxygen, so as to promote the reaction to proceed to the right, accelerate the reaction efficiency, and especially the effect of the antimony-doped cerium-zirconium oxide is more obvious.

Further, it should be understood that various changes or modifications of the present invention may be made by those skilled in the art after reading the teaching of the present invention, and such equivalents may fall within the scope of the present invention as defined in the appended claims.