Phase Equilibria and Volumetric Properties of (1-Ethyl-3-Methylimidazolium Ethylsulfate + Alcohol or Water) Binary Systems

Abstract

Solid–liquid and liquid–liquid phase equilibria in binary mixtures that contain a room-temperature ionic liquid and an alcohol, or water—namely, 1-ethyl-3-methylimidazolium ethylsulfate, [EMIM][EtSO4] with an alcohol (1-octanol, or 1-decanol, or 1-undecanol, or 1-dodecanol) and water have been measured at normal pressure by a dynamic method from 250 to 350 K. By increasing the alkyl chain length of an alcohol, the upper critical solution temperature, UCST, increased (changing from 1-undecanol to 1-dodecanol). Complete miscibility was observed for the systems ([EMIM][EtSO4]+methanol, or ethanol, or 1-propanol, or 1-butanol, 1-pentanol, or 1-hexanol, or 1-heptanol, or 1-octanol, or 1-nonanol, -or 1-decanol and water) at the temperature 298.15 K. Densities and excess molar volumes, VmE, have been determined for [EMIM][EtSO4] with either 1-propanol, or 1-butanol, or 1-pentanol, or 1-hexanol, or 1-heptanol, or 1-octanol, or 1-nonanol, or 1-decanol at 298.15 K and ambient pressure. These systems exhibit negative or positive molar excess volumes. Our experimental VmE data were used for the description of HmE for the chosen systems of [EMIM][EtSO4] with the alcohols under study. The simple Prigogine-Flory-Paterson (PFP) model has given slightly worse results than the Flory-Benson-Treszczanowicz (FBT) model. Negative excess molar volumes observed for 1-propanol and 1-butanol are attributed to hydrogen bonding between the short chain alcohols and ionic liquid, and high packing effects. The FBT model overestimates the self-association of the alcohols in the solutions under study and shifts the calculated curves to higher mole fraction of the alcohol. For each system and for chosen number of the Redlich-Kister parameters, Ar, the partial molar volumes, V1E and V2E, are presented.