Transport properties and thermodynamic characterization of aqueous solutions of morpholinium - based ionic liquids

Abstract

In this work, the systematic studies of the physical and thermodynamic properties of two binary systems involving morpholinium-based ionic liquids, that is: N-ethyl-N-methyl-morpholinium acetate, [EMMOR][AcO] and N-ethyl-N-methylmorpholinium propionate, [EMMOR][Pro] with water are reported. Synthesis of new carboxylate - based ionic liquids (ILs) were performed in our laboratory and the structures were confirmed by nuclear magnetic resonance spectroscopy, NMR and elementary analysis. Basic thermophysical properties that is: the glass transition temperature, Tg,1 and heat capacity at glass transition temperature, ΔCp(g) were determined by the differential scanning calorimetry (DSC) technique. The measurements of density, ρ and dynamic viscosity, η over the entire concentration range at temperatures from (298.15 to 348.15) K with 5K intervals have been done at pressure p=100kPa. From experimental data, excess molar volumes, VE and dynamic viscosity deviations, Δη were calculated using Redlich - Kister equation. The mutual solubility of the tested ILs with water have been determined using dynamic method. The isothermal vapor − liquid phase equilibria, VLE have been measured by an ebulliometric method within temperature range from (328.15 to 368.15) K and pressure up to 100kPa. Phase equilibrium data have been correlated using the NRTL equation. The influence of the anion structure on the presented transport and thermodynamic properties is presented and discussed.