Extension of an Associated Lattice-Fluid Equation of State to CO2 + Ionic Liquid Systems

We describe an extension of the Associated Lattice-Fluid (ALP) Equation of State (EOS) for correlating/predicting the volumetric and phase behavior of CO2 + imidazolium-based ionic liquid (IL) systems over a wide range of temperatures and pressures. The EOS is based on the Guggenheim-Huggins-Miller lattice fluid partition function and includes a contribution for specific interactions between CO2 and CO2-philic functional groups in the IL. Although two adjustable parameters are incorporated in the model, these parameters do not depend on temperature or pressure. Furthermore, one of the parameters can be obtained via enthalpy of absorption measurements. The remaining parameter in the ALF EOS requires only one solubility isotherm for correlating/predicting both phase equilibrium and volumetric properties of CO2 + IL systems over a wide range of conditions.