Thermodynamic modeling of hydrogen solubility in a series of ionic liquids

Abstract

In this study, the Perturbed Hard Sphere Chain Equation of State (PHSC EoS) has been employed to predict the hydrogen solubility in a series of ionic liquids. As ionic liquids have no vapor pressure and no critical parameters and as hydrogen is a light molecule which behaves like a perfect gas, simple cubic equations of state cannot be used for modeling of H2 + ionic liquid mixture. Three main parameters of non-cubic PHSC EoS, i.e. (r) the number of segments per molecule, (σ) the distance between two molecules at zero potential and (ε) well-depth of potential between two non-bonded units have been calculated by regression of the experimental Pressure-Volume-Temperature (PVT) data points. The hydrogen solubility decreases with increasing temperature in [BMIM][BF4], [BMIM][C8SO4], [EMIM][EtSO4], [MDEA][Cl], and [N4,1,1,1][Tf2N], but inverse temperature effect is observed in [BMIM], [BMPY], [EMIM] and [HMIM][Tf2N] as well as [BMIM][MeSO4]. The binary interaction parameter which has been obtained from fitting of the equation of state with experimental hydrogen absorption data shows both the usual and the opposite trend of temperature effect as well.