The Determination Of Vapor-Liquid Equili-Brium Data For Methanol+Tert-Butylam INE And Study On Extractive Distillation

Methanol and tert-butylamine are commonly used as mixed solvents in pharmaceutical industry. They can’t be separated into their pure components through ordinary distillation because of their azeotropic problems. While the vapor-liquid equilibrium (VLE) data and the method of separation about this system are all not reported in the existing literatures. So the determination of VLE data for methanol+ tert-butylamine binary system and studying on the extractive distillation have extremely vital significance.The VLE data of methanol+tert-butylamine binary system is measured by using a modified Rose-Williams still at atmospheric pressure, the results show that the binary system exists a maximum boiling point azeotrope at the methanol mole fraction of 0.763 and the tert-butylamine mole fraction of 0.237, corresponding to the temperature of 340.28 K.The DMF and water are selected as the extraction solvents for azeotropic mixture of methanol+tert-butylamine by experience screening. The VLE data of methanol+tert-butylamine+DMF/water ternary systems are measured at atmospheric pressure when the ratios of solvent are 1:2,1:1,2:1, respectively. The restults show that when the DMF or water are added into the azeotropic mixture, the azeotropic phenomenon of the methanol+tert-butylamine binary system disappears, the relative volatility of terf-butylamine to methanol near the azeotropic composition is greater than 1, and these values are proportional to change with the ratio of solvent. These restults indicate that the DMF and water are feasible as extractants of methanol+terf-butylamine binary system. The extraction efficiency of water is better than DMF at the same ratio of solvent. Besides, the VLE data of tert-butylamine+DMF/water binary systems are measured at atmospheric pressure, and it provides basic data for the prediction of the VLE data for ternary systems.Using the Herington method to check the thermodynamics consistency with all the binary experimental data, and correlating the VLE data of methanol+tert-butylamine, tert-butylamine+DMF/water by using the Wilson, NRTL and UNIQUAC models. The results show that all the binary experimental data meet the thermodynamics consistency and these experimental data are reliable. The binary interaction parameters about the three models for methanol+ tert-butylamine, tert-butylamine+DMF/water binary systems are obtained by the thermodynamic model correlation and the associated values are in agreement with the experiment values. The VLE data of methanol+tert-butylamine+DMF ternary system are predicted by the parameters of the Wilson and NRTL models, and the predicted data are compared with the experimental data, proving that the predicted deviations of the NRTL model are less than the Wilson model.The continuous extractive distillation experiment is carried out at atmospheric pressure with the DMF and water as the extractants of methanol+tert-butylamine system, which the extractive distillation column has thirty theoretical plates, and its diameter is twenty millimeters. Studying the effects of the feed location and reflux ratio on the separation efficiency. The results show that when the extractant is DMF, the azeotropic mixture can be separated into high purity components, on condition that the ratio of solvent is 2:1, the feed location of raw material is at the 21st theoretical plate, and the ratio of reflux is nine, when the extractant is water, the azeotropic mixture also can be separated into high purity components, on condition that the ratio of solvent is 1:1, the feed location of raw material is at the 16th theoretical plate, and the ratio of reflux is seven. Above the two kinds of operating conditions, the mass fraction of tert-butylamine at the top of the distillation column are greater than 99% and at the bottom of distillation column are less than 1%.