Dichlorophenoxyacetic acid is an important raw material for organic synthesis, which is widely used in the fields of pesticides, pharmaceuticals and dyes. A manufacturing method of dichlorophenoxyacetic acid will be introduced below.
I. Raw materials and equipment
1. Raw materials: phenol, chloroacetic acid, sodium hydroxide, hydrochloric acid.
2. Equipment: reactor, stirrer, thermometer, condenser, dispensing funnel, centrifuge and so on.
2. Manufacturing steps
1. Add phenol and appropriate amount of water in the reactor and stir well.
2. Slowly add sodium hydroxide solution under stirring and adjust pH to alkaline environment.
3. Slowly add chloroacetic acid dropwise, keep the reaction temperature at 40-50°C. Carbon dioxide gas will be generated during the reaction, which needs to be discharged through condenser.
4. At the end of the reaction, adjust the pH with hydrochloric acid to acidic and precipitate dichlorophenoxyacetic acid.
5. The precipitate is separated by centrifugation and washed clean with ethanol to obtain the crude product of dichlorophenoxyacetic acid.
6. The crude product was recrystallized to obtain the finished product of dichlorophenoxyacetic acid with high purity.
3. Precautions
1. Phenol and chloroacetic acid are both highly irritating chemicals, protective gear is required during operation to avoid direct contact.
2. Appropriate stirring speed and reaction temperature need to be maintained during the reaction to ensure the smooth progress of the reaction.
3. Adjust the pH value slowly to avoid over-acidic or over-alkaline corrosion of the equipment.
4. The centrifugal separation needs to control the rotational speed and time to avoid excessive load on the equipment.
Four, yield and purity
The yield of this manufacturing method is generally between 80-90%, and the purity can reach more than 98%. The specific yield and purity will be affected by the quality of raw materials, operating conditions and other factors.
V. Safety and environmental protection
1. Safety needs to be paid attention to during operation to avoid accidents such as spilling of raw materials or gas leakage.
2. Waste needs to be handled properly to avoid pollution to the environment. Waste can be converted into harmless substances through neutralization, oxidation and other treatment methods.
VI. Optimization and improvement
In order to further improve the yield and purity of dichlorophenoxyacetic acid, the following measures can be taken:
1. Optimize the raw material ratio and operating conditions to improve the selectivity and efficiency of the reaction.
2. Adopt new type of reaction equipment and technology, such as microwave reaction, ultrasonic reaction, etc., to improve the speed and homogeneity of the reaction.
3. Enhance the treatment and recycling of waste to reduce the production cost and environmental pollution.
All in all, the manufacturing method of dichlorophenoxyacetic acid needs to be selected and optimized according to specific production conditions and requirements, in order to improve production efficiency and economic benefits, and also pay attention to safety and environmental protection and other requirements.
