The Effect Of Several Ionic Liquids On Vapor-liquid Equilibrium For Methanol-Methyl Ethyl Ketone System And Computer Simulation Of Extractive Distillation

Methanol and methyl ethyl ketone (MEK), important raw material in industrial synthesis, can form azeotrope when mixed. In recent years, the research of ionic liquids (ILs) as entrainers for extractive distillation is becoming more and more prevalent. ILs serving as entrainers can bring many advantages, such as high selectivity, small solvent ratio, good operability. In this paper, suitable ILs was picked out for methanol-MEK system,vapor-liquid equilibrium (VLE) data was measured, effect of ILs was analyzed,applicability of several models to systems containing ILs was investigated,and extractive distillation using ILs as entrainers was simulated by computer.Specific work as follow:1. The selectivity and capacity at infinite dilution of 19 ILs in separation of methanol-MEK system were calculated by UNIFAC model. The result showed that anions of ILs have more prominent influence on selectivity and capacity.The order of separation ability in term of anions is as follows: [NTf2] > [PF6] >[OTf] > [BF4] > [SCN] > [DMP]. Enhancement factor of relative volatility was defined and calculated. According to that, ILs [EMIM][NTf2],[BMIM][NTf2] and [HMIM][NTf2] have good separation ability for methanol-MEK system. And VLE for ternary system containing ILs was predicted by UNIFAC model.2. Isobaric VLE data for three ternary systems of methanol - MEK -[EMIM][NTf2], methanol - MEK - [BMIM][NTf2] and methanol - MEK -[HMIM][NTf2] was measured at 101.3 kPa. The results showed that ILs exerted a notable salting-in effect on system and decreased the activity coefficient of MEK, thus enhanced the relative volatility of methanol to MEK.Azeotrope can be easily elimilated when the mole fraction of IL in the liquid phase is more than 0.05. The salt effect of ILs follows this order:[HMIM][NTf2] > [BMIM][NTf2] > [EMIM][NTf2].3. Four activity coefficient models including Wilson, NRTL, UNIQUAC and e-NRTL were used to correlate VLE data of methanol-MEK-IL ternary system. Wilson, NRTL and UNIQUAC can reproduce the experimental data with a small deviation less than 2%, which means Wilson, NRTL and UNIQUAC have good applicability to the system containing ILs. e-NRTL was supposed not to be used for system containing ILs due to the large deviation.In addition, UNIFAC model seems more accurate when ILs' content in system is low.4. Extractive distillation process using ILs as entrainers to separate methanol and MEK was simulated by Aspen Plus. Products with good quality were obtained and the parameters of equipments and process were optimized.The extractive effect of ILs follows the order: [HMIM][NTf2] >[BMIM][NTf2] > [EMIM][NTf2]. Compared with extractive distillation using diethyl ketone, many advantages were found in extractive distillation using ILs. Vapor-liquid distribution and tempareture distribution in the column were studied and sensitive plate was located.