Study On The Separation Of Binary Azeotropic Mixture By Extractive Distillation

The separation of azeotropes and close-boiling mixtures is often faced in the pharmaceutical and special chemical industries and the mixtures can’t be separated by ordinary distillation. This can be overcome by the process of extractive distillation and the products can be directly got by the process of extractive distillation. Acetone-tetrahydrofuran mixture, n-hexane-tetrahydrofuran mixture, n-hexane-ethyl acetate mixture, ethanol-ethyl acetate mixture and benzene-cyclohexane mixture all can form binary minimum azeotropes. The separation of these mixtures is studied in this paper to get a widely used method that extractive distillation can be used to separate new azeotropes and close-boiling mixtures.For the separation of these mixtures, firstly, according to the dielectric constant to screen alternative solvent, residue curve map and vapor-liquid equilibrium were drawn to determine the solvent used in extractive distillation of each mixture. Butyl ether was chosen as the solvent to separate acetone-tetrahydrofuran mixture; N-methyl pyrrolidone was chosen as the solvent to separate n-hexane-tetrahydrofuran mixture; N-methyl pyrrolidone was chosen as the solvent to separate n-hexane-ethyl acetate mixture; dimethyl sulfoxide was chosen as the solvent to separate ethanol-ethyl acetate mixture; dimethyl sulfoxide was chosen as the solvent to separate benzene-cyclohexane. Then Aspen Plus was used to simulate the process of extractive distillation with the determined solvent of each mixture and the simulation parameters were optimized. At last, the experiments of extractive distillation with the determined solvent and the optimized simulation parameters of each mixture were done and the mixtures were separated successfully, the composition of the products can get99%wt or more.A widely used method of extractive distillation used in the separation of new azeotrope mixtures was got through the successfully separation of these mixtures, that is firstly according to the dielectric constant to screen alternative solvent, residue curve map and vapor-liquid equilibrium were drawn to determine the solvent used in extractive distillation, and then Aspen Plus was used to simulate the process of extractive distillation with the determined solvent. Using this method, not only can reduce the amount of the experiments, but also a lot of time can be saved.