Thermodynamics Research Center / ThermoML | Journal of Chemical and Engineering Data

ABSTRACT

Three ionic liquids (ILs) (1-ethyl-3-methylimidazolium bromide [EMIM]Br, 1ethyl-3-methylimidazolium chloride [EMIM]Cl and 1-ethyl-3-methylimidazolium acetate [EMIM][Ac]) were used for the separation of the ethyl acetate + methanol azeotropic mixture. The vapor-liquid equilibrium (VLE) data of Ethyl Acetate + Methanol azeotropic mixtures containing ILs were measured at 101.3kPa. The three ILs show significant salting-out effects on ethyl acetate. The azeotropic point of the ethyl acetate + methanol azeotropic system is eliminated when mole content of IL reaches a special value. The separation abilities of the three ILs follow the order [EMIM][Ac] > [EMIM]Cl> [EMIM]Br. The experimental data are correlated well by the nonrandom two-liquid (NRTL) model. 1. INTRODUCTION Ethyl acetate and methanol are vital chemical raw materials. The mixture of ethyl acetate and methanol is common in fine chemical industry and pharmaceutical process such as the production process of gastrodine, Gliclazide, and Cafotaxime sodium. In order to reduce environmental pollution and recycle resource, it is necessary to separate them from their mixture. However, ethyl acetate and methanol can form a minimum azeotrope.1 It is impossible to obtain their pure products by common distillation. Some special distillation methods have been utilized to separate the close-boiling or azeotropic mixtures, such as extractive distillation, azeotropic distillation and pressure swing distillation.2-6 Extractive distillation is widely used because of its advantages of flexible selection of entrainers, simple operation and high separation ability.7,8 In extractive distillation, the key point is to select a suitable entrainer.9 Traditional entrainers (organic solvents and solid salts) have a lot of defects, such as solvent loss, difficulty in recovering, high energy consumption and equipment corrosion. At present, ionic liquids (ILs) have been increasingly studied as entrainers in extractive distillation because of their negligible vapor pressure, high selectivity, wide liquid temperature range and good thermal and chemical stability.10-15 The vapor-liquid equilibrium (VLE) behavior of methanol + ethyl acetate containing traditional entrainer (organic solvent or solid salt) have been studied for design and development of the extractive distillation process.16-18 It can be seen from the VLE data of methanol + ethyl acetate containing chloroform, that the azeotropic phenomena of the ethyl acetate-methanol binary mixture and the chloroform-methanol binary mixture were eliminated in the ternary system.16 The separation effect of calcium chloride on the methanol-ethyl acetate binary mixture was reported by Ohe et al.17 The relative volatility of ethyl acetate to methanol was increased due to the formation of CaCl2*6CH3OH, but the azeotropic phenomenon of the ethyl acetate-methanol mixture wasn't completely eliminated in the manuscript. However, there are very few reports on the use of ILs as entrainers to separate the ethyl acetate-methanol binary azeotropic system up to now. The separation effects of two phosphate-based ILs (1-ethyl-3methylimidazolium diethylphosphate [EMIM][DEP] and 1-butyl-3methylimidazolium dibutylphosphate [BMIM][DBP]) on the binary system have been investigated by this research group.19 The two ILs showed the better separation ability