Density and Viscosity Modeling of Three Deep Eutectic Solvents Using a Volume-Shifted Cubic Equation of State Coupled with the Friction Theory

Abstract

In this work, a three-parameter viscosity model based on the friction theory (FT) and coupled with a cubic equation of state was developed to correlate and predict the dynamic viscosity of deep eutectic solvents (DESs). The present viscosity model was derived from an existing six-parameter FT-based viscosity model, which was previously applied to pure ionic liquids. By focusing on the most dominant dragging forces affecting the viscosity of DESs, we were able to safely reduce the number of model parameters without a significant loss of model accuracy. The use of a volume-shifted cubic EoS (Soave−Redlich−Kwong or Peng−Robinson) served also to obtain improved density estimations of the DESs under study. The resulting modeling approach was successfully validated during the correlation of experimental dynamic viscosities and mass densities of three archetypal DESs (choline chloride-based DESs): reline, ethaline, and glyceline within a temperature range varying from 283.15 to 373.15 K and at pressures from 1 to 1000 bar. The average absolute relative deviations yielded by the present thermodynamic model varied from 0.27 to 0.93% for the density modeling and from 2.25 to 4.29% for the viscosity modeling of the three DESs.

Modified Free-Volume Theory for the Viscosity Modeling of Ionic Liquids and Deep Eutectic Solvents

“…However, this approach requires a priori knowledge of the experimental densities of ILs in order to obtain the best possible superposition of the viscosity data using a power-law scaling potential in terms of temperature and density. To the best of our knowledge, only three modeling attempts have been so far published dealing with the dynamic viscosity of DESs as a function of temperature and pressure. ,, In fact, the very same authors who measured the high-pressure viscosities of three archetypal ChCl-based DESs, namely, Crespo et al, also modeled their own experimental viscosities using the FVT approach coupled with the PC-SAFT EoS. Just recently, Macı́as-Salinas and Pereda-Cruz along with Macı́as-Salinas and Romero-Rueda, reported on two viscosity models for the three aforementioned DESs using the entropy scaling and the friction theory approaches, respectively.…”