Isobaric Vapor-Liquid Equilibrium for Acetone + Methanol + Phosphate Ionic Liquids Xiaochun Chen, † Bin Yang, † Ahmed A. Abdeltawab, ‡ Salem S. Al-Deyab, ‡ Guangren Yu,* ,† and Xingyue Yong* ,† † Beijing Key Laboratory of Membrane Science and Technology & College of Chemical Engineering, Beijing University of Chemical Technology, Beijing 100029, P. R. China ‡ Petrochemicals Research Chair, College of Science, King Saud University, Riyadh 11451, Saudi Arabia * S Supporting Information ABSTRACT: Isobaric vapor-liquid equilibrium (VLE) at atmospheric pressure (101.3 kPa) for the binary systems of acetone + methanol, acetone + phosphate ionic liquids (ILs), and methanol + phosphate ILs, and for the ternary system of acetone + methanol + phosphate ILs are measured using a circulation VLE still. The phosphate ILs include 1,3-dimethylimidazolium 1,3-dimethylimidazolium dime- thylphosphate ([MMIM][DMP]), 1-ethyl-3-methylimidazolium diethylphosphate ([EMIM][DEP]), and 1-butyl-3-methylimidazolium dibutylphosphate ([BMIM]- [DBP]). The addition of these phosphate ILs to the azeotropic acetone + methanol system results in a salting-out effect on acetone and makes the azeotropic point disappear. The relative volatility α 12 of acetone over methanol increases with increasing molar fraction of ILs. The equilibrium data were well fitted by the electrolyte nonrandom two-liquid model (e-NRTL). Compared with some reported ILs previously such as pyridinium hexafluorophosphate, imidazolium trifluoromethane sulfonate and imidazolium dicyanamide, such imidazolium phosphate ILs are fluorine-free, are prepared more simply with lower cost, and make the azeotropic point disappear at less added amount of ILs. This work shows that such phosphate ILs are a class of potential solvents to separate azeotropic acetone + methanol system. ■ INTRODUCTION Acetone and methanol are a typical azeotropic system in chemical industries such as furfural production and Fischer-Tropsch process. 1,2 For such an azeotropic system, simple distillation usually does not work, and some special distillation technologies such as azeotropic distillation, 3 pressure swing distillation 4,5 and extractive distillation 6,7 are needed. Among these methods, extractive distillation is preferred. Typically, ethylamine was used as entrainer for the separation of the azeotropic system of acetone + methanol. 8 However, the volatility and corrosion of ethylamine limits its industrial application; therefore an alternative to such an unfavorable entrainer is desired. Recently, ionic liquids (ILs) have received much more attention as entrainers used in extractive distillation after they were first studied by Arlt et al. for their unique properties. 9 As “designer green solvents”, ILs have three advantages compared with some traditional entrainers: (i) they can be easily added to the reflux stream because of low melting points (typically below 373 K); (ii) their great solubility for inorganic, organic, and polymeric materials makes them have a higher salting-out effect with higher concentration of electrolyte; (iii) ILs can be regenerated after removing some volatile compounds from ILs by distillations such as flash distillation due to the negligible vapor pressure of ILs. Also, they have some other advantages such as higher thermal stability and less susceptibility to corrosion. 10 Phase equilibrium data are necessary to study using ILs as entrainers in extractive distillation separation for azeotropic systems. Isothermal phase equilibrium data were determined for acetone + methanol + ILs (e.g., N-butyl-pyridinium hexafluor- ophosphate, [bpy][PF 6 ]; 11 1-ethyl-3-methylimidazolium hydro- gen sulfate, [EMIM][HSO 4 ]; 12 1-ethyl-3-methylimidazolium Received: August 7, 2014 Accepted: December 30, 2014 Figure 1. Structure of phosphate-based ILs. Article pubs.acs.org/jced © XXXX American Chemical Society A DOI: 10.1021/je5007373 J. Chem. Eng. Data XXXX, XXX, XXX-XXX