Separation of Carbon Dioxide and Sulfur Dioxide Gases Using Room-Temperature Ionic Liquid [hmim][Tf_2N]

摘要

To understand capturing and/or enhanced gaseous selectivity of industrial flue gases containing CO_2 and SO_2 using room-temperature ionic liquids, we have developed a ternary equation of state (EOS) model for a CO_2/SO_2/1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([hmim][Tf_2N]) system. The present model is based on a generic RK (Redlich-Kwong) EOS, with empirical binary interaction parameters of each binary system. These interaction parameters have been determined using our measured VLE (vapor-liquid-equilibrium) data for SO_2/[hmim][Tf_2N] and CO_2/[hmim][Tf_2N] and literature data for CO_2/SO_2. The validity of the present EOS has been checked by conducting ternary VLE experiments for the present system. With this EOS, isothermal ternary phase diagrams and solubility (VLE) behaviors have been calculated for various (T, P, and feed compositions) conditions. For large and equimolar CO_2/ SO_2 mole ratios, the gaseous selectivity is nearly independent of the amount of the ionic liquid addition. However, for small CO_2/SO_2 mole ratios the addition of the ionic liquid significantly increases the selectivity. The strong absorption of CO_2 and SO_2 in this ionic liquid may be practical for the simultaneous capture of these acid gases.