Thermophysical properties of N-phenyl-N-ethanol ammonium carboxylate based ionic liquids: Measurements, correlations and COSMO-RS study

摘要

In this work, a series of four protic ionic liquids were synthesized by an exothermic neutralization process between N-phenyl-N-ethanolamine and stoichiometric quantity of different acids, namely, propionic acid, butyric acid, pentanoic acid and hexanoic acid. After characterization by H-1 NMR and C-13 NMR spectroscopic methods, density (rho), speed of sound (u), viscosity (eta) and conductivity (sigma) of neat ionic liquids have been measured 293.15 to 343.15 K and the refractive index (n(D)) was measured only at 303.15 K. The density and refractive index data were correlated by Gardas-Coutinho model and Lorentz-Lorenz mathematical equation, respectively, whereas viscosity and electrical conductivity were estimated by Vogel-Tammann-Fulcher (VTF) equation. Further experimental data used to calculate several derived thermodynamic properties such as thermal expansion coefficient (alpha), isentropic compressibility (beta(s)), molar volume (V-m), standard entropy (S degrees), intermolecular free length (L-f), molar refraction (R-m) and free volume (f(v)). The decomposition temperature (T-d) of synthesized ILs was investigated using TGA analysis. Finally, Conductor-like Screening Model for Real Solvents (COSMO-RS) computational method was also studied to understand the structural variations of the ionic liquids. (C) 2017 Elsevier B.V. All rights reserved.