Simulation And Optimization Of O,S-Dimethyl Phosphorpamidothioate Intergration Flowsheet

O,S-dimethyl phosphoramidothioate is a very important compound which is used as intermediate in pesticides such as acephate and chlorine methamidophos. At present, the way of production O,S-dimethyl phosphoramidothioate is discontinuous isomerization with catalyzer of dimethyl sulfate in high conversion, the yield of the product commonly reaches 82% and the purity of product can only be 72%. Therefore it results in wasting raw materials and complexing to purify continuous products such as acephate and chlorine methamidophos, then influences the final qualities of the production and increases the operating costs.Having looked up of a great amount of technical literature both domestic and foreign, and under the direction of the theory of reaction engineering and chemical thermodynamics, the process of isomerizing O,O-dimethyl phosphoramidothioate is analyzed, the main reasons to decline isomerization's selectivity is the consecutive side reaction of product O,S-dimethyl phosphoramidothioate. The kinetic models of isomerization are amended and the parameters of the models are estimated. The results show that the activation energy of side reaction is higher than main reaction; Considering the heat decomposability of organic phosphorus compounds, the decomposed velocity of O,S-dimethyl phosphoramidothioate is mensurated and the effction of low pressure is studied. The thermal decomposed reaction is first-order reaction and the low pressure is not evidence to influence the thermolysis. The purity of the O,S-dimethyl phosphoramidothioate product can reach 87% with using wiped film molecular distillation to separate, about 97% unreacted O,S-dimethyl phosphoramidothioate can be recycled.From process system engineering and green process engineering, the continuous isomerization-molecular distillation green integration flowsheet is proposed. The mathematic models for tubular reactor, mixing and separators are established with reasonable simplification, the influences by which the process's parameters have effects on the performance of flow sheet are exactly and fully analyzed. At last on the basis of stable simulation, the optimization model is established. The infeasible path method based on successive quadratic programming algorithms used to carry out the optimized model which the target function is maximum of the product yield and the recovery of unreacted materials. The results are beneficial discussed.The integration flowsheet can improve the utilization ratio, reduce by-product and make the follow-up purifying process easy, it has vital significance in saving resource and protecting environment.