In the production of sulfonylurea herbicides, 2-amino-4,6-dimethoxypyrimidine is an important intermediate in its synthesis, and there are many varieties of herbicides made of it, such as nicosulfuron, Bensulfuron-methyl, pyrazosulfuron-methyl, rimsulfuron-methyl, alumsulfuron-methyl, ethisulfuron-methyl, thiasulfuron-methyl, etc.
Analysis of post-treatment process of intermediates of sulfonylurea herbicides
At present, in the mainstream preparation method of ADMP, the process route using malononitrile as raw material has been focused on all the time. In the step of aromatization and ring closure reaction, a solvent-free method is adopted. The obtained crude product is distilled under high vacuum, and then an organic solvent is introduced as a dispersant. Crystallization and granulation are carried out to obtain pure products. This solution is low in cost and simple in operation, and has played a practical role in promoting the industrialization of existing processes. The selection of dispersants is concentrated on common organic solvents such as toluene and xylene. However, the following disadvantages still exist in the process of industrialization:
① Increase production cost.
The dispersant has a certain solubility to the product, causing product loss, and at the same time, it needs to be recycled and used mechanically, resulting in operating costs.
② There are potential safety hazards. During the filtration and drying process of toluene-based organic solvents, due to factors such as their own flammability and low flash point, there are hidden dangers such as inducing fires;
③ There are certain environmental pressure problems.
Due to the large amount of toluene dispersant, it will volatilize and leak during use (such as product filtration, dispersant recovery and mother liquor treatment, etc.), increasing the impact of volatile organic compounds (VOC, volatile organic compounds) on the factory Environmental pollution affects the health of workers.
The barrel-cone reaction, filtration and drying multifunctional machine developed by Wuxi ZhangHua has multiple functions in one machine. It can complete various operations such as reaction, extraction and crystallization, filtration, repeated filtration, washing, and drying in one machine, and directly obtain the finished product. The unique advantages meet the post-treatment process requirements of simple operation, zero pollution, high yield and high quality to obtain pure 2-amino-4,6-dimethoxypyrimidine.
Process flow of sulfonylurea herbicide intermediate post-treatment special reaction filtration washing and drying multifunctional equipment
1. Stirring reaction: This machine has a barrel-cone structure, which can heat or cool the material in the machine for constant temperature and timing reaction; add pure water and stabilizer to the product obtained after distillation and cooling, and heat it to 75 ° C ~ 95 ° C Melt, then slowly cool down to 30°C~50°C while stirring
2. Pressure filtration or vacuum filtration: After the reaction is completed, filter the filtrate through pressure filtration or vacuum suction filtration. In the filtration stage, due to the good adhesion between the ribbon and the filter medium and the scraping effect, the material can be kept in the thin layer of filter cake Filtration under the best conditions, high filtration efficiency;
3. Can be washed and filtered multiple times: After filtering and drying the material, you can add washing liquid, and perform multiple automatic reactions and mixing with the material in the machine before washing, and then filter and dry after washing and filtering meet the washing requirements.
4. Vacuum drying and discharging: After the material is filtered and dried, the material is heated at the same time in the jacket of the drying section, the hollow shaft and the spiral belt, and the vacuum is vacuumed at the top to dry the material in vacuum and low temperature, and it is automatically sealed after drying. Discharge. After the filter cake is dried, the pure product of 2-amino-4,6-dimethoxypyrimidine is obtained in the form of white crystals.
The multi-functional equipment for the purification of sulfonylurea herbicide intermediates, reaction, filtration, washing and drying improves the production effect of ADMP by improving the equipment structure and optimizing the process flow. Material loss is greatly reduced.
Moreover, it is especially suitable for such toxic or flammable and explosive operations that require particularly high sealing requirements, and has almost no impact on the workers' bodies and the surrounding environment.