Preparation method of chlorpyrifos

Abstract

The invention provides a preparation method of chlorpyrifos, and relates to the field of chemical synthesis, and the preparation method comprises the following steps: adding 3, 5, 6-trichloropyridine-2-sodium alkoxide, a composite catalyst and distilled water into a reactor; after uniformly stirring, adding 0, 0-diethyl thiophosphoryl chloride to obtain a reaction solution, and adding ammonia water; raising the temperature to 45-55 DEG C, after the reaction is finished, transferring the reaction liquid to a suction filtration device for suction filtration, and separating out a filter cake containing a chlorpyrifos crude product and a mother solution; and washing the filter cake with water, and drying to obtain a chlorpyrifos active compound finished product. According to the preparation method disclosed by the invention, 0, 0-diethyl thiophosphoryl chloride and ammonia water are added at one time, so that the exposure risk of toxic substances is reduced; water is used as a solvent, ammonia water is used as an acid-binding agent, and the problems of organic solvent pollution and strong alkaline wastewater treatment are solved; by controlling the alkalescence environment and reaction conditions, side reaction is inhibited, and the yield and purity of the product both reach 99% or above.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of chemical synthesis, in particular to a preparation method of chlorpyrifos. BACKGROUND

[0002] Chlorpyrifos (chemical name: 0,0-diethyl-0-(3,5,6-trichloro-2-pyridyl) phosphorothioate) as a kind of high-efficiency, broad-spectrum organophosphorus pesticide, due to its characteristics of low residue and low resistance, is widely used in the field of agricultural pest control, and plays a key role in protecting crop yield and quality. With the expansion of global agricultural production scale and the improvement of quality and safety requirements of agricultural products, how to efficiently and environmentally synthesize chlorpyrifos has become an important research direction in the field of chemical synthesis. Currently, the mainstream method for synthesizing chlorpyrifos in industry is mainly organic solvent method and aqueous solvent method, but both methods have obvious defects. The organic solvent method usually uses organic solvents such as toluene as reaction medium, and prepares chlorpyrifos through condensation, vacuum distillation and other processes. However, the organic solvents used in this method have the characteristics of high toxicity and easy volatilization, not only exist safety hazards such as flammability and explosion in the production process, threatening the health of operators, but also cause serious air, soil and water pollution due to the volatilization and residue of organic solvents. In addition, the loss of organic solvents in the reaction process is large, and the recycling and disposal cost is high, which leads to a significant increase in production cost, and is also not conducive to environmental protection and sustainable development. Although the aqueous solvent method replaces water with organic solvents as reaction medium, it reduces toxicity and pollution to some extent, but also has many problems. The "one-pot method" in the traditional aqueous solvent method adds water, 3,5,6-trichloropyridin-2-ol sodium, catalyst and 0,0-diethyl thiophosphoryl chloride (ethyl chloride) into the reaction system at the same time. Since the materials cannot be fully dispersed in the initial stage, the ethyl chloride cannot fully contact with other reactants in the initial stage of the reaction, the reaction rate is slow, and the decomposition of ethyl chloride is caused, resulting in waste of raw materials and reduction of product yield. Another commonly used aqueous solvent method uses dropwise addition of ethyl chloride for reaction, although it can improve the reaction conditions to some extent, but the ethyl chloride is highly toxic, the operators are at high risk of exposure to toxic substances during the dropwise addition process, and the dropwise addition operation has strict requirements for equipment and process control, increasing the difficulty of safety production management. In addition, the existing aqueous solvent method generally uses strong alkaline substances such as sodium carbonate, potassium carbonate and sodium hydroxide as acid-binding agents, and the strong alkaline environment can accelerate the hydrolysis reaction of ethyl chloride and promote the decomposition of chlorpyrifos, resulting in a large number of side reactions, low product purity and yield, which is difficult to meet the demand of high-quality production, and the treatment of strong alkaline wastewater also brings great pressure to the environment.

[0003] In summary, the preparation method of chlorpyrifos in the prior art has complex operation method, environmental pollution in the preparation process, and low product yield. SUMMARY The present application aims to overcome the above technical deficiencies, and provide a method for preparing chlorpyrifos, to solve the technical problems of complex operation, low product quality and poor yield in the preparation process of chlorpyrifos in the prior art.

[0004] To achieve the above technical purpose, the technical scheme of the present application provides a method for preparing chlorpyrifos, comprising the following steps: S1, 3, 5, 6-trichloropyridin-2-ol sodium, composite catalyst and distilled water are added to the reactor; S2, after stirring uniformly, 0, 0-diethyl thiophosphoryl chloride is added to obtain a reaction solution, and ammonia water is added to adjust the pH value of the reaction solution to 9.5-10.5; S3, the temperature is increased to 45-55℃, after the reaction is completed (the reaction process is sampled at regular time, and the residual amount of raw material is detected by gas chromatography method, when the residual amount of 0, 0-diethyl thiophosphoryl chloride is ≤0.5%, the reaction is determined to be complete), the reaction liquid is transferred to a filtration device for filtration, and the filter cake containing chlorpyrifos crude product and the mother liquor are separated; S4, the filter cake containing chlorpyrifos crude product is washed with water and dried to obtain chlorpyrifos technical product.

[0005] Preferably, the composite catalyst in S1 is two or more of tetrabutylammonium bromide, tetrabutylammonium chloride, benzyltrimethylammonium chloride, benzyltriethylammonium chloride and 4-methylaminopyridine.

[0006] Preferably, the composite catalyst is a mixture of tetrabutylammonium bromide and 4-methylaminopyridine.

[0007] Preferably, the composite catalyst is a mixture of tetrabutylammonium bromide and 4-methylaminopyridine mixed in a mass ratio of 1:1.

[0008] Preferably, the mass ratio of 3, 5, 6-trichloropyridin-2-ol sodium, composite catalyst, distilled water and 0, 0-diethyl thiophosphoryl chloride is 1100-1200:25:4500-5000:1000-1062.

[0009] Preferably, the mass ratio of 3, 5, 6-trichloropyridin-2-ol sodium, composite catalyst, distilled water and 0, 0-diethyl thiophosphoryl chloride is 1200:25:5000:1062.

[0010] Preferably, the drying temperature in S4 is 60-80℃.

[0011] Preferably, the mass concentration of the ammonia water is 25-30% (too high concentration will volatilize quickly, which is not conducive to the experiment). The preparation method of the application first adds water in a reaction kettle, and then sequentially adds a composite catalyst and sodium 3,5,6-trichloropyridine-2-ol, stirs until the materials are uniformly dispersed, and forms a stable reaction system. After the system is uniformly dispersed, 0,0-diethyl phosphorochloridite is added at one time, and then ammonia water is slowly added dropwise to adjust the system to a weak alkaline environment. The reaction system is warmed to a suitable temperature and incubated for a period of time, during which stirring is maintained, and the reaction endpoint is determined by monitoring the residual raw materials. After the reaction is completed, the product is suction filtered, washed with water, and dried to obtain the chlorpyrifos technical product; the obtained solid is mixed with the next batch of raw materials for reuse, and part of the mother liquor is discharged regularly to prevent impurities from accumulating.

[0012] Compared with the prior art, the application has the following advantages: The preparation method of the chlorpyrifos adds 0,0-diethyl phosphorochloridite and ammonia water at one time, simplifies the operation process of the traditional dropwise process, reduces the exposure risk of toxic substances and the equipment requirements, uses water as the solvent and ammonia water as the acid-binding agent to avoid organic solvent pollution and strong alkaline wastewater treatment difficulties, and has outstanding environmental protection; by controlling the weak alkaline environment and the reaction conditions, the byproduct reaction is inhibited, and the product yield and purity are both above 99%; at the same time, the raw material ratio is optimized, the filter cake is recycled, the raw material waste and equipment investment are reduced, the production cost is effectively reduced, and the advantages of convenient operation, green environmental protection, high quality and high efficiency are combined. DETAILED DESCRIPTION

[0013] In order to make the purpose, technical scheme and advantages of the application clearer, the application will be further described in detail below with examples. It should be understood that the specific examples described herein are only used to explain the application and not to limit the application.

[0014] Example 1 The embodiment provides a preparation method of chlorpyrifos, which comprises the following steps: S1, sodium 3,5,6-trichloropyridine-2-ol, a composite catalyst (tetrabutylammonium bromide and tetrabutylammonium chloride are mixed in a mass ratio of 1:1) and distilled water are added to a reactor; S2, after stirring, 0,0-diethyl phosphorochloridite is added to obtain a reaction solution, and ammonia water is added to adjust the pH value of the reaction solution to 9.5; the mass ratio of sodium 3,5,6-trichloropyridine-2-ol, the composite catalyst, distilled water and 0,0-diethyl phosphorochloridite is 1100:25:4500:1000; the mass concentration of ammonia water is 25%; S3, the temperature is increased to 45℃, after the reaction is completed (during the reaction process, the raw material residual amount is detected by gas chromatography method, when the residual amount of 0,0-diethyl phosphorochloridite is ≤0.5%, the reaction is determined to be complete), the reaction liquid is transferred to a suction filtration device for suction filtration, and the filter cake containing the chlorpyrifos crude product and the mother liquor are separated; S4. The filter cake containing crude chlorpyrifos was washed with water and dried at 60°C for 12 hours to obtain the chlorpyrifos technical product. The yield of the chlorpyrifos technical product was 99%, and the purity was 99% (gas chromatography).

[0015] Example 2 This embodiment provides a method for preparing chlorpyrifos, including the following steps: S1. Add sodium 3,5,6-trichloropyridine-2-ol, a composite catalyst (a mixture of tetrabutylammonium bromide and 4-methylaminopyridine in a mass ratio of 1:1) and distilled water to the reactor; S2. After stirring evenly, add 0,0-diethylthiophosphoric acid chloride to obtain a reaction solution. Add ammonia water to adjust the pH of the reaction solution to 10,3,5,6-trichloropyridin-2-ol sodium, composite catalyst, distilled water and 0,0-diethylthiophosphoric acid chloride in a mass ratio of 1150:25:4800:1050, and the mass concentration of ammonia water is 27%. S3. Increase the temperature to 45℃. After the reaction is complete (samples are taken at regular intervals during the reaction, and the residual amount of raw materials is detected by gas chromatography. When the residual amount of 0,0-diethylthiophosphoric acid chloride is ≤0.5%, the reaction is considered complete), transfer the reaction solution to a vacuum filtration device for filtration to separate the filter cake and mother liquor containing crude chlorpyrifos. S4. The filter cake containing crude chlorpyrifos was washed with water and dried at 70°C for 11 hours to obtain the chlorpyrifos technical product. The yield of the chlorpyrifos technical product was 99.1%, and the purity was 99.2% (gas chromatography).

[0016] Example 3 This embodiment provides a method for preparing chlorpyrifos, including the following steps: S1. Add sodium 3,5,6-trichloropyridine-2-ol, the composite catalyst (a mixture of benzyltrimethylammonium chloride and benzyltriethylammonium chloride in a mass ratio of 1:1) and distilled water to the reactor; S2. After stirring evenly, add 0,0-diethylthiophosphoric acid chloride to obtain a reaction solution. Add ammonia water to adjust the pH of the reaction solution to 10.5. The mass ratio of sodium 3,5,6-trichloropyridin-2-ol, composite catalyst, distilled water and 0,0-diethylthiophosphoric acid chloride is 1200:25:5000:1062, and the mass concentration of ammonia water is 30%. S3. Increase the temperature to 45℃. After the reaction is complete (samples are taken at regular intervals during the reaction, and the residual amount of raw materials is detected by gas chromatography. When the residual amount of 0,0-diethylthiophosphoric acid chloride is ≤0.5%, the reaction is considered complete), transfer the reaction solution to a vacuum filtration device for filtration to separate the filter cake and mother liquor containing crude chlorpyrifos. S4. The filter cake containing crude chlorpyrifos was washed with water and dried at 80°C for 10 hours to obtain the chlorpyrifos technical product. The yield of the chlorpyrifos technical product was 99.2%, and the content was 99.4% (gas chromatography). Example 4 This embodiment provides a method for preparing chlorpyrifos, including the following steps: S1. Add sodium 3,5,6-trichloropyridine-2-ol, a composite catalyst (a mixture of tetrabutylammonium bromide and 4-methylaminopyridine in a mass ratio of 1:1) and distilled water to the reactor; S2. After stirring evenly, add 0,0-diethylthiophosphoric acid to obtain a reaction solution. Add ammonia water to adjust the pH of the reaction solution to 10,3,5,6-trichloropyridin-2-ol sodium, composite catalyst, distilled water and 0,0-diethylthiophosphoric acid in a mass ratio of 1200:25:5000:1062, and the mass concentration of ammonia water is 30%. S3. Increase the temperature to 50℃. After the reaction is complete (samples are taken at regular intervals during the reaction, and the residual amount of raw materials is detected by gas chromatography. When the residual amount of 0,0-diethylthiophosphoric acid chloride is ≤0.5%, the reaction is considered complete), transfer the reaction solution to a vacuum filtration device for filtration to separate the filter cake and mother liquor containing crude chlorpyrifos. S4. The filter cake containing crude chlorpyrifos was washed with water and dried at 80°C for 12 hours to obtain the finished chlorpyrifos technical product. The yield of the finished chlorpyrifos technical product was 99.4%, and the content was 99.6% (gas chromatography).

[0017] Example 5 This embodiment provides a method for preparing chlorpyrifos, including the following steps: S1. Add sodium 3,5,6-trichloropyridine-2-ol, a composite catalyst (a mixture of tetrabutylammonium bromide and 4-methylaminopyridine in a mass ratio of 1:1) and distilled water to the reactor; S2. After stirring evenly, add 0,0-diethylthiophosphoric acid to obtain a reaction solution. Add ammonia water to adjust the pH of the reaction solution to 10,3,5,6-trichloropyridin-2-ol sodium, composite catalyst, distilled water and 0,0-diethylthiophosphoric acid in a mass ratio of 1200:25:5000:1062, and the mass concentration of ammonia water is 30%. S3. Raise the temperature to 55℃. After the reaction is complete (samples are taken at regular intervals during the reaction, and the residual amount of raw materials is detected by gas chromatography. When the residual amount of 0,0-diethylthiophosphoric acid chloride is ≤0.5%, the reaction is considered complete), transfer the reaction solution to a vacuum filtration device for filtration to separate the filter cake and mother liquor containing crude chlorpyrifos. S4. The filter cake containing crude chlorpyrifos was washed with water and dried at 80°C for 12 hours to obtain the finished chlorpyrifos technical product. The yield of the finished chlorpyrifos technical product was 99.3%, and the content was 99.5% (gas chromatography).

[0018] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A process for the preparation of chlorpyrifos, characterized in that, The method comprises the following steps: S1, adding sodium 3,5,6-trichloropyridine-2-olate, a composite catalyst and distilled water into a reactor; S2, after stirring uniformly, adding 0,0-diethyl thiophosphoryl chloride to obtain a reaction solution, and adding ammonia water to adjust the pH value of the reaction solution to 9.5-10.5; S3, increasing the temperature to 45-55 DEG C, after the reaction is completed, transferring the reaction solution to a filtration device to perform filtration, and separating a filter cake containing a chlorpyrifos crude product and a mother liquor; S4, washing the filter cake containing the chlorpyrifos crude product with water, drying to obtain a chlorpyrifos technical product.

2. The process for preparing chlorpyrifos according to claim 1, characterized in that, The composite catalyst in S1 is two or more of tetrabutylammonium bromide, tetrabutylammonium chloride, benzyltrimethylammonium chloride, benzyltriethylammonium chloride and 4-methylaminopyridine.

3. The process for preparing chlorpyrifos according to claim 1, characterized by, The composite catalyst is a mixture of tetrabutylammonium bromide and 4-methylaminopyridine.

4. The process for preparing chlorpyrifos according to claim 1, characterized by, The composite catalyst is a mixture of tetrabutylammonium bromide and 4-methylaminopyridine mixed at a mass ratio of 1:

1.

5. The process for preparing chlorpyrifos according to claim 1, characterized by, The mass ratio of sodium 3,5,6-trichloropyridine-2-olate, the composite catalyst, distilled water and 0,0-diethyl thiophosphoryl chloride is 1100-1200:25:4500-5000:1000-1062.

6. The process for preparing chlorpyrifos according to claim 5, characterized by, The mass ratio of sodium 3,5,6-trichloropyridine-2-olate, the composite catalyst, distilled water and 0,0-diethyl thiophosphoryl chloride is 1200:25:5000:1062.

7. The process for preparing chlorpyrifos according to claim 1, characterized by, The drying temperature in S4 is 60-80 DEG C.

8. The process for preparing chlorpyrifos according to claim 1, characterized by, The mass concentration of the ammonia water is 25-30%. The mass concentration of the ammonia water is 25-30%.