Separation of Carbon Dioxide and Sulfur Dioxide Using Room-Temperature Ionic Liquid [bmim][MeSO4]

A ternary equation of state (EOS) model for the CO2/SO2/l-butyl-3-methylimidazolium methyl sulfate ([bmim][MeSO4]) system has been developed in order to gain further our understanding of capturing and enhanced gaseous selectivity of industrial flue gases containing CO2 and SO2 using room-temperature ionic liquids. The present model is based on a generic Redlich-Kwong (RK) EOS. The empirical binary interaction parameters have been determined using our measured vapor-liquid-equilibrium (VLE) data for SO2/[bmim][MeSO4] and literature data for CO2/[bmim][MeSO4] and CO2/SO2. The validity of the present EOS has been checked by conducting ternary VLE experiments for the present system. With this EOS, an isothermal ternary phase diagram and solubility (VLE) behaviors have been calculated for various (T, P, and feed compositions) conditions. The addition of the [bmim][MeSO4] for small and equimolar CO2/SO2 mole ratios significantly increased the selectivity. For large CO2/SO2 mole ratios, the selectivity was high for even a small addition of ionic liquid and in certain cases showed a maximum selectivity due to preferential chemical absorption of SO2. The enhancement in CO2/SO2 selectivity using [bmim][MeSO4] was significantly higher than using 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([hmim][Tf2N]) from our previous work and may make the simultaneous capture and separation of these acid gases practical.