Influence of temperature on thermophysical properties of ammonium ionic liquids with N-methyl-2-pyrrolidone

To address the molecular interactions between ionic liquids (ILs) such as trimethylammonium acetate [(CH3)3NH][CH3COO] (TMAA), trimethylammonium hydrogen sulphate [(CH3)3NH][HSO4] (TMAS), trimethylammonium dihydrogen phosphate [(CH3)3NH][H2PO4] (TMAP) and triethylammonium dihydrogen phosphate [(CH3CH2)3NH][H2PO4] (TEAP) with N-methyl-2-pyrrolidone (NMP), density (ρ), ultrasonic sound velocity (u) and viscosity (η) measurements have been performed across the entire concentration range and the wide temperature range from 298.15 to 313.15 K in steps of 5 K under ambient pressure. Further, on the basis of the measured properties, excess volumes (VE), isentropic compressibility deviations (Δκs) and viscosity deviations (Δη) were obtained for all these systems under the same experimental conditions. The results are correlated by the Redlich–Kister type equation. The results are also analysed on anion dependent phenomena and temperature influence on measured and derived properties of ILs with NMP mixtures. A qualitative analysis of molecular interactions between ILs and NMP is discussed in terms of the ion-dipole, ion-pair interactions, and hydrogen bonding.

► We report densities, sound velocities and viscosities for NMP with ionic liquids.
► We have predicted VE, ΔKs and Δη from measured ρ, u and η, respectively.
► Redlich–Kister polynomial was used to correlate the results.
► We have synthesized the new ammonium based ILs.
► The intermolecular interactions were analysed on the basis of derived properties.