Density, Viscosity, and Speed of Sound of Pure and Binary Mixtures of Ionic Liquids Based on Sulfonium and Imidazolium Cations and Bis(trifluoromethylsulfonyl)imide Anion with 1-Propanol

Abstract

We present densities, viscosities, and speed of sound of pure and binary mixtures of three ionic liquids, triethylsulfonium bis(trifluoromethylsulfonyl)imide, [Et3S][TFSI], 1-allyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [Amim][TFSI], and 1,3-dihydroxyimidazolium bis(trifluoromethylsulfonyl)imide, [(OH)2Im][TFSI], with 1-propanol from (293.15 to 343.15) K at 0.1 MPa. We also include densities, viscosities, and speed of sound of pure ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide for validation. Densities and speed of sound are measured using a vibrating tube densimeter while viscosities are from a pellet microviscometer. The density and viscosity of pure ionic liquids are correlated by means of the Gardas and Coutinho and Vogel–Tammann–Fulcher equations, respectively. From the speed of sound measurements, we obtain isentropic compressibility, speed of sound deviation, and isentropic compressibility deviation for mixtures of ionic liquids and 1- propanol. Excess molar volumes and viscosity deviations are calculated from the experimental data. The excess molar volumes for the binary mixtures with [Et3S][TFSI] and [Amim][TFSI] present positive and negative deviations from ideality while those for the binary mixture with [(OH)2Im][TFSI] exhibit only negative deviations. Viscosity deviations for [Et3S][TFSI] + 1-propanol, [Amim][TFSI] + 1-propanol, and [(OH)2Im][TFSI] + 1-propanol are negative over the entire temperature range. The speed of sound deviations are positive and negative for the binary mixtures of 1-propanol with [Et3S][TFSI] and [Amim][TFSI], whereas those for the mixture with [(OH)2Im][TFSI] are negative.