Correlation of phase equilibria and liquid densities for gases with ionic liquids

We describe a method for correlating and estimating gas solubilities and liquid densities of ionic liquids based on a corresponding-states form for direct correlation function integrals (DCFIs) from fluctuation solution theory, as previously applied to nonionic systems. A quantitative description is obtained for the volumetric behavior of pure liquids at elevated pressures. Solubilities and partial molar volumes are given over wide ranges of conditions using only pure component information and a binary parameter for hydrogen, carbon monoxide, oxygen and methane in the ionic liquids 1-butyl-3-methyl-imidazolium hexafluorophosphate, [bmim][PF6], and 1-hexyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide, [hmim][Tf2N]. Comparisons are made with other literature treatments and a predictive approach is described.