(437e) Multi-Scale Gibbs-Helmholtz Constrained (GHC) Equation of State Investigation of Ionic Liquid (1-butyl-3-methylimidazolium hexafluorophosphate) and Water

Abstract

Room temperature ionic liquids (RTILs) have been the subject of intense research for a number of years because of their wide ranging industrial applications¹. The lack of experimental physical property data for RTILs and the presence of ions has severely hindered the use of traditional equations of state (EOS) in modeling RTILs and mixtures involving RTILs.  

In this talk, the multi-scale Gibbs-Helmholtz Constrained (GHC) EOS is used to capture the non-ideal properties of RTILs and mixtures involving RTILs by incorporating molecular level internal energies of departure, U^D, from Monte Carlo simulation in the description of fluids in the bulk. More specifically, internal energies of departure of pure RTILs obtained from  a priori Gibbs Ensemble Monte Carlo (GEMC) simulations are stored in look-up tables, internal energies of mixtures are estimated using a linear mixing rule, and the bulk fluid energy parameter for the GHC equation is estimated using a novel up-scaling equation. To illustrate the versatility of the multi-scale GHC framework, the behavior of 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF₆) ² and water is studied. It is shown that the GHC equation accurately predicts liquid BMIM-PF₆densities and phase equilibrium at pressures typically found in industry applications and validated using experimental data where available.   

1) Plechkova, N. V, & Seddon, K. R. (2008). Applications of ionic liquids in the chemical industry. Chem. Soc. Rev., 37(1), 123–150. http://doi.org/10.1039/B006677J

2) Shah, J. K., & Maginn, E. J. (2005). Monte Carlo Simulations of Gas Solubility in the Ionic Liquid 1-n-Butyl-3-methylimidazolium Hexafluorophosphate. The Journal of Physical Chemistry B, 109(20), 10395–10405. http://doi.org/10.1021/jp0442089