Thermodynamic modeling of solubility of hydrogen sulfide in ionic liquids using Peng Robinson-Two State equation of state

Abstract

In this work, a simple association equations of state, namely Peng Robinson-Two state (PR-TS) association model is applied to model the PVT behavior of pure ionic liquids and solubility of H2S in 12 various imidazolium-based ionic liquids. This equation of state consists of two terms, the Peng-Robinson (PR) equation of state as cubic term for non-specific energy contribution and two-state association model (TSAM) for association energy contribution. First, to obtain the parameters of the PR-TS EoS for pure components, the experimental liquid density of different pure ionic liquids at various temperatures and pressures are correlated and the percent absolute average deviation between the calculated and experimental densities of ionic liquids is about 0.24%. For pure H2S two association schemes are considered as in the presence or not of association behavior. Then, the parameters of the model for these two schemes are correlated by simultaneously optimization of vapor pressure and liquid density data. Following successful application of the model for the pure components the PR-TS EoS is applied to predict the vapor-liquid equilibrium (VLE) of the several H2S + IL binary mixtures with this assumption that in binary mixtures present cross-association or self-association interaction. For binary systems in first approach only one interaction parameter is used and in second approach two binary interaction parameters are applied. The results of the VLE calculation of the H2S + IL systems show that the best accuracy with AAD = 3.40% is obtained when H2S is considered as non-association component and is used two binary interaction parameters for modeling the binary systems. In overall, the results of the present model for pure and binary systems comprise H2S and ILs are in very good agreement with experiments.