Viscosities of 2-hydroxy ethylammonium formate ionic liquid from 0.1 MPa to 40 MPa: Measurement and modelling

Abstract

This work extended the measurements of dynamic viscosities of 2-hydroxy ethylammonium formate (2-HEAF) ionic liquid to high-pressure. The dynamic viscosities were measured in (298.15–328.15) K range and pressures from (0.1 to 40) MPa with the uncertainties within ±(0.85–5.3) mPa s. The experimental data were correlated/predicted using a two-parameter empirical equation as well as semi-theoretical model based on the rough-hard-sphere theory (RHS) with the average absolute relative deviation of 1.14% and 2.18%, respectively. The RHS model used two molecular parameters as well as the liquid densities, for which the values were estimated from perturbed hard-sphere equation of state. The experimental results have also been compared with those coming from the previously reported molecular dynamics results. Additionally, molecular dynamics results allowed a nanoscopic level analysis of the main features controlling viscosity in terms of hydrogen bonding properties and changes with temperature and pressure.