Viscosity modeling for ionic liquid solutions by Eyring-Wilson equation

Abstract

A semi-theoretical model based on the classical Eyring’s mixture viscosity equation and the Wilson activity coefficient equation is presented for correlating the viscosity of ionic liquids with solvent systems. The accuracy of the proposed model was verified by comparing calculated and experimental viscosity values from literatures for 49mixtures with total 1560 data points. The results show that the equation similar to the Wilson activity coefficient equation can be well applied to describe the non-ideal term in the Eyring’s mixture viscosity equation. The model has a relatively simple mathematical form and can be easily incorporated into process simulation software

Viscosity of binary mixtures of 1-ethyl-3-methylimidazolium tetrafluoroborate ionic liquid with four organic solvents

“…In this paper, the one-parameter Grunberg-Nissan and Fang and He [5] and two-parameter three-body McAllister [10], Eyring-UNIQUAC [11], Eyring-NRTL [12] and Eyring-Wilson [6,13] models were used for the viscosity calculation. The common idea of these models, except GrunbergNissan, is that the classical thermodynamics can be extended to viscous flow behaviour of the liquid mixture by assuming equivalence between the Gibbs energy of activation for flow and the equilibrium Gibbs energy of mixing [11].…”

“…This model is rational only when the molecular volumes of two substances are very close. But for size-asymmetric mixtures containing small and large molecules, as happen in the mixtures of organic solvents with ionic liquids, generally more complicated multi-parameter equations should be considered [4,6,7,42].…”

“…By the application of the Wilson equation based on the local composition concept to represent the excess Gibbs energy [6,13], viscosity of binary mixtures containing ILs can be expressed as: …”

“…The literature of the last years indicates some empirical or semi-empirical viscosity models which have been applied to correlate IL-cosolvent mixtures [2][3][4][5][6][7][8][9]. Among these, the models based on Eyring's absolute rate theory and activity coefficient model has firm fundamental basis that can offer better results than the frequently used mixing rules, as Grunberg-Nissan [4][5][6][7][8].…”

“…The models tested in this work include the three body McAllister [10], Eyring-UNIQUAC [11], Eyring-NRTL [12] and Eyring-Wilson [6,13] models. In addition, we tested also the equation developed by Fang and He [5] with one parameter, which offer the advantage of being used when limited experimental results are available.…”