Separation Process Optimization Of Acephate

Acephate,commonly known as orthene. Its chemical name is O,S-dimethyl-N-ac-etyl-phoramidothioate, with forbidden of O,S-dimethyl-phoramidothioate, acephate, as the ideal substitute of O,S-dimethyl-phoramidothioate, it will have a great demand in the future. However,the existing separation technology of acephate is not entirely satisfied because of high cost,poor product quality, long recovery process of acetic acid.Weighting the advantages and disadvantages of the existing separation technology,considering the existing acephate synthesis and separation processes at the same time,a new separation of acetic ac id by vacuum distillation was presented in this paper. This method is easy to operate and avoid the problems of equipment corrosion. Solvent recycling is easy because of using a single solvent, this method not only got high purity(97%)and yield(94%)of products, but also reduced less waste water.In this paper, a new separation process was proposed, which was separate aetic acid under high vacuum from the reaction liquid which had separated most of aephate crystallization. First, We found that the best vacuum distillation time was 1.5h, temperature was 50℃-55 ℃. When temperature was 50 ℃,separation of acetic acid reached 60.71%, with a purity of 97.87%,yield of acephate was 77.95%, However when the temperature is 55 ℃,separate amount of acetic acid was 71.98%, with purity of 96.36%, acephate yield was 84.06 %.Further, acephate were recrystallized with 1,2-dichloromethane. Washed four times under the condition of dichloromethane: acephate was 1: 4, then,the yield of recrystallization can reach 65.25%, with purity of 97.30% When the concentration of acephate was 55%.Secondly, 1,2-dichloromethane,which was from recrystallization, was applied to the extraction operation, it was suggest that the best ratio of dissolvent and solution was 0.4: 1 and the extraction stages was 5. At the same time, distribution curve of O,O-dimethyl-N-acetyl-phoramidothioate was: Y = 3.90 X + 0.06, the distribution curve of acephate was: Y = 5.13X2-2.65 X + 0.4. In the other hand, calculation result showed that :in order to make the concentrate of O,O-dimethyl-N-acetyl-phoramidoth-ioate was 0.001 in the residual phase, the optimized ratio of dissolvent and solution was 0.4, the optimized extraction stages was 4, the extraction rate of O,O-dimethyl-N-acetyl-phoramidothioate is 99.37%, the concentration of O,O-dimethyl-N-acetyl-phoramidothioate in the residual phase was 19.48%, extraction rate of acephate is 67.25%.Finally, in the reverse extraction process, the best ratio of water and solution was0.4: 1and the extraction stages was 6, the extraction rate of acephate could reach more than 99%. The distribution curve of O,O-dimethyl-N-acetyl-phoramidothioate was: Y = 0.1937X-0.0022, the distribution curve of acephate was: Y =-0.603X2 + 0.907 X + 0.092.Otherwise, Calculation result showed that when the raw material methacholine amine concentration of acephate was 20.12% in the raw material, in order to make the concentrate of acephate was 0.001 in the residual phase, the best ratio of water and solution was0.5: 1and the extraction stage s was 4.What we did the study of the various parts of acephate separation process will have a great help to optimize this process and industrial application.