New Process Of Acetochlor Preparation In Methylene Method

Acetochlor is the largest use of a kind of amide herbicides at present. So far, most manufacturers produce acetochlor in ether method which is an old technology. However, ether method has some disadvantages such as low purity of the produced acetochlor; high cost; abundant wastes output; and so on. Compared to the old method, Methylene method has obvious superiority in acetochlor production. The purity of acetochlor which produced in methylene method can reach 95% under mild process conditions. Moreover, methylene method shows less damage to the environment for its small wastes output. Now the environmental situation is increasingly serious, thus, Methylene method has drawn more and more attention.Methylene method was applied to the synthesis of acetochlor in our work. At first, under the catalysis and depolymerization of organic alcohol amine sulphur compounds, paraformaldehyde and MEA generated Homogeneous liquid. Methylene imine was obtained after dehydration formaldehyde off in high vacuum. With rectification, methylene imine was then reacted with chloroacetic chloride to get tertiary amine. The tertiary amine could generate acetochlor when temperature not exceeding 30℃ with excess alcohol. The hydrogen chloride produced in the reaction can be removed by liquid ammonia in circulation absorption. The high purity acetochlor was finally obtained after washing and water evaporating with purity of 95% and yield of 92%.The parameters which can influence the reaction were analyzed and optimized under laboratory conditions to get optimum technology. In this optimum technology, the addition of selective catalyst was 1% weight of aniline in imidization synthesis; the mole ratio of paraformaldehyde and aniline was 1.6:1; 3h for dehydration; 100-105℃ for reaction; nitrogen protection was adopted in later period of imine synthesis to ensure the minimum decomposition of imine. In the synthesis process of tertiary amine, dropwise add was employed in the addition of methylene imine to chloroacetyl chloride, and the optimum mole ratio was 1:1.05. With the mole ratio between tertiary amine and alcohol was 1:4 and temperature not exceeding 30℃,6h was sufficient for reaction process. Then, the optimum technology in lab was applied in industrial-scale production and successfully transferred to methylene method-acetochlor project with 4800t/a, and was verified in the production process. With tank reactor and film evaporator, the methylene imine produced in industrial-scale production can get approximate level to the methylene imine synthesized under lab conditions. Compared to the old technology, acetochlor per ton could save up to 2130 Yuan in methylene method.