Molecular Simulation Study of the Solubility, Diffusivity and Permselectivity of Pure and Binary Mixtures of CO2 and CH4 in the Ionic Liquid 1-n-Butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide

Abstract

The knowledge of the mixture solubility and diffusivity of gases in ionic liquids (ILs) is critical for the design of supported ionic liquid membranes (SILMs). Because mixed gas solubilities and diffusivities in ILs are much more difficult to measure than pure gas properties, pure gas solubility and diffusivity data are typically used along with an ideal solubility/diffusivity assumption to estimate permselectivities. It is not clear, however, if the ideal solubility and diffusivity assumptions are valid. In this work, molecular dynamics (MD) and Gibbs ensemble Monte Carlo (GEMC) simulations were used to compute the diffusion selectivity and solubility selectivity of CO2 and CH4 in the IL 1-n-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C4mim]+[Tf2N]−), along with the pure gas solubilities and diffusivities, in order to test the ideal permselectivity assumption. Pure gas solubilities of CO2 and CH4 in [C4mim]+[Tf2N]− at 333 K and pressures ranging from 1 to 100 bar were found to be in exc...