Thermodynamic properties of DBN-based ionic liquids and their binary mixtures with primary alcohols

Abstract

Two novel azole-based ionic liquids, including [HDBN][Im] and [HDBN][Tri], prepared from 1,5-diazabicyclo [4.3.0] non-5-ene (DBN) with imidazole (Im) or 1,2,4-triazole (Triz) were synthesized. The density and viscosity of the pure ionic liquids and their binary mixtures with methanol, ethanol, isopropanol and n-butanol were measured at temperature ranging from T= (298.15 to 313.15) K. The molecular volume, standard entropy, thermal expansion coefficients and lattice energy of pure ionic liquids were deduced from the experimental density results. The temperature dependence of the viscosity was fitted well by Vogel-Fulcher-Tammann equation and fluidity equation. The estimated values of the activation energy Eη for viscous flow was obtained by Arrhenius empirical equation. Activation thermodynamic functions for viscous flow including ΔG≠, ΔH≠, ΔU≠ and ΔS≠ of [HDBN][Im] and [HDBN][Tri] were calculated by Eyring viscosity equation. And the relationship between the dynamic viscosity and the molar conductivity of ILs was discussed in terms of Waldenʹs rule. In addition, excess molar volumes VE, viscosity deviations Δη, relative viscosity ηr, excess viscosity ηE and the excess Gibbs energy of activation for viscous flow ΔG*E for the ILs + alcohol binary mixtures were also obtained from experimental data of densities ρ and viscosities η of mixtures and fitted to the Redlich-Kister equation.