Modeling solubility of CO2 gas in room temperature ionic liquids using the COSMOSAC-LANL model: a first principles study

In this paper we present a thermodynamic model for asymmetric solutions with a special emphasis on solute–solvent interactions. The new “COSMOSAC-LANL” activity coefficient model is rooted in first principles calculations based on the COSMO model where the microscopic information passes to the macroscopic world via a dielectric continuum solvation model followed by a post statistical thermodynamic treatment of self-consistent properties of the solute particle. To model the activity coefficient at infinite dilution for the binary mixtures, a 3-suffix Margules (3sM) function is introduced to model asymmetric interactions and, for the combinatorial term, the Staverman–Guggenheim (SG) form is used. The new “COSMOSAC-LANL” activity coefficient model has been used to calculate the solubility of CO2 in room temperature ionic liquids and to model the selectivity between CO2 and CH4 gases. We have shown improved solubility and selectivity prediction of CO2 and CH4 gas in room temperature ionic liquids using the ADF-COSMOSAC-2013 model with the new “LANL” activity coefficient model. The calculated values have been compared with experimental results where they are available.