Experimental determination of viscosity for the binary mixtures of the ether-functionalized ionic liquids [C22O1IM][TfO] with monohydric alcohols

Abstract

In order to apply ionic liquids in various fields, it is necessary to understand their physical and chemical properties. Viscosity, in particular, is an important parameter of multicomponent solutions and plays a decisive role in mass transfer, heat transfer and fluid flow in industrial process. In this work, the ether-functionalized ionic liquid [C22O1IM][TfO] was synthesized and characterized by 1H NMR, 13C NMR, ESI mass spectrometry and elemental analysis. The viscosity of the binary mixture of ionic liquid [C22O1IM][TfO] with ethanol, 1-propanol and 2-propanol in the full concentration range of T = (288.15–318.15) K were measured. The relationships between the viscosity of the binary system and concentration and temperature were investigated. By Vogel–Tamman–Fulcher (VTF) equation and Arrhenius equation, the temperature dependences of the viscosities for the binary system were described and the VTF equation showed better correlation for the binary system. The viscosity deviation that expresses the difference between the actual value and the ideal value of the mixture viscosity, Δη, was calculated. At the same time, the Gibbs energy of activation for viscous flow of the relative viscosity for the mixture, ΔG≠r, was also calculated based on the relative viscosity, ηr, and ΔG≠r is negative that is consistent with the results of, Δη, it means that the interaction between ions becomes weak due to the solvation. The viscosity deviation, Δη, and the Gibbs energy of activation for viscous flow of the relative viscosity for the mixture, ΔG≠r, could be well fitted by the Redlich–Kister equation. In addition, the related entropies and enthalpies were also calculated and discussed.