Modeling the viscosity of pure imidazolium-based ionic liquids using SAFT-VR-Mie EoS

Abstract

In this work, three models, namely frictional theory (FT), free-volume theory (FVT) and modified Yarranton–Satyro (MYS), have been coupled with SAFT-VR-Mie equation of state for the first time to accurately estimate viscosity of following ionic liquids: 1-alkyl-3-methylimidazolium tetrafluoroborate, [Cn-mim][BF4]; 1-alkyl-3-methylimidazolium hexafluoroborate, [Cn-mim][PF6]; 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [Cn-mim][Tf2N]. For this purpose, the density of each component was calculated by using the optimized parameters in SAFT-VR Mie equation of state. Furthermore, the adjustable parameters of GSAFT-Cubic EoS were estimated for some of IBILs to comprise the ability of these models. Using experimental viscosity data, the constants of the mentioned viscosity models are correlated. Finally, by comparing the obtained AAD for each IBILs, it can be seen that the viscosity is not properly and satisfactorily calculated with the FT model while the performance of the MYS model is better than the FVT and FT models. Also the result showed that the MYS coupled with SAFT-VR Mie calculate the viscosity with appropriate accuracy. Therefore, this approach might be particularly useful in modeling viscosity of IBILs.