Separation of N2O and CO2 using Room-Temperature Ionic Liquid [bmim][Ac

Abstract

We have developed a ternary equation of state (EOS) model for the N2O/CO2/1-butyl-3-methylimidazolium acetate ([bmim][Ac]) system in order to understand the separation of N2O and CO2 using room-temperature ionic liquids (RTILs). The present model is based on a generic RK (Redlich-Kwong) EOS, with empirical interaction parameters for each binary system. The interaction parameters have been determined using our measured VLE (vapor-liquid-equilibrium) data for N2O/[bmim][Ac] and literature data for CO2/[bmim][Ac] and N2O/CO2. The binary EOS model for the N2O/[bmim][Ac] system correctly predicted the liquid-liquid phase separation found in VLLE experiments. The validity of the ternary EOS model has been checked by conducting VLE experiments for the N2O/CO2/[bmim][Ac] system over a temperature range from 296 to 313 K. With this EOS model, solubility (VLE) behavior has been calculated for various (T, P, and feed compositions) conditions. Over a range of N2O/CO2 feed ratios, the N2O/CO2 gas selectivity [α N 2 O/CO 2 = (y N 2 O /x N 2 O )/(y CO 2 /x CO 2 )] increases by at least 5 orders of magnitude when adding [bmim][Ac] (α = 1 × 102 to 1 × 107), compared with the absence of the ionic liquid (α = 0.96 to 0.98). The addition of [bmim][Ac] may provide a practical means of separating CO2 and N2O. Supplemental materials are available for this article. Go to the publisher's online edition of Separation Science and Technology to view the free supplemental file.