| The separation of the mixture is important in chemical industries. Liquid mixture with azeotropic phenomenon cannot be separated by conventional distillation, as a result, especial distillations are needed to separate the azeotrope.In this paper, the characteristics of extraction distillation, selection of extractive solvent, the effect and advantages of mixed solvent were summarized. On the basis of modified UNIFAC model, a program was prepared with MATLAB software for the choice of extractant and investigation on conditions such as temperature and solvent ratio. With this program, three azeotropic systems– acetone and methanol, methyl and acetate, benzene and cyclohexane were studied. The result showed that adding extractant can improve relative volatility to a great extent, and for most of azeotropic systems,relative volatilities increased with increasing solvent ratio and decreasing temperature.In this paper, the effect of mixed solvent on relative volatility of key-component of the azeotrope was studied too. The result showed: for benzene-cyclohexane azeotropic system, if DMF+NMP or NMP+DMSO were used as extraction agents respectively, in a wide range of concentration, the separation performance of mixed solvents were better than single-solvent, and the composition of mixed solvent existed a best value, according to which, the mixed solvent had the best separation performance,The relative volatility values calculated were consistent with the literature ones, which showed that the results of the procedures were feasible and reliable. |
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