Correlation and prediction of dense fluid transport coefficients. IX. Ionic liquids

The aim of this paper is to examine the application of a hard-sphere scheme to the correlation and prediction of the viscosity and thermal conductivity of ionic liquids. Ionic liquids present an excellent case, because of their high viscosity. It was found that, regardless of the fact that the scheme had to be extended by orders of magnitude, it was still an excellent scheme for the correlation and prediction of the properties of these liquids; this fact is attributed to its theoretical basis. A database of 461 viscosity and 170 thermal-conductivity measurements for 19 ionic liquids was considered. The average absolute deviation was 2.31 % for the viscosity and 3.15 % for the thermal conductivity, while the expanded uncertainty at the 95 % confidence level was 4.6 % and 6.3 %, respectively. Moreover, if the thermal-conductivity roughness factor is allowed to be temperature dependent, then the average absolute deviation was reduced to 0.91 % for the thermal conductivity, and the expanded uncertainty at the 95 % confidence level to 1.82 %. As the scheme requires knowledge of the density, 1070 measurements of density were employed to derive a Tait-type equation for every ionic liquid considered.