Measurements, Correlations, and Predictions of Thermodynamic Properties of N-Octylisoquinolinium Thiocyanate Ionic Liquid and Its Aqueous Solutions

Abstract

N-Octylisoquinolinium thiocyanate, [C8iQuin][SCN], has been synthesized in our laboratory from [C8iQuin][Br] as a substrate. The compound was characterized using 1H-NMR, 13C-NMR, and elemental analysis. Karl Fisher titration was used to determine the water content. The density and viscosity of pure ionic liquid were determined over a wide temperature range from (288.15 to 348.15) K. The basic thermal properties of the pure IL have been measured using by means of a differential scanning microcalorimetry technique (DSC). Decomposition of the IL was detected by the simultaneous TG/DTA experiments. (Liquid + liquid) phase equilibria (LLE) have been measured for binary mixtures {[C8iQuin][SCN] (1) + water (2)} using a dynamic method at atmospheric pressure. The experiments have been done over a broad range of ionic liquid mole fraction, x1, and temperatures from 250 K to the boiling point of water. Experimental heat capacities and excess enthalpies were determined for {[C8iQuin][SCN] (1) + water (2)} binary mixtures for different IL mole fractions at a wide range of the temperature at ambient pressure. The influence of temperature and composition was assessed, and suitable equations were used to correlate the experimental data. The experimental results were compared with data for other ionic liquids available in the open literature.