Enhanced CO2 Adsorption and Separation in Ionic-Liquid-Impregnated Mesoporous Silica MCM-41: A Molecular Simulation Study

摘要

Separation of CO2 from gas mixtures is of importance in CO2 capture from flue gas and in natural gas sweetening. In this paper, we have conducted grand canonical Monte Carlo (GCMG) simulations to study the adsorption of CO2, N-2, and CH4 and separation of their binary mixtures in mesoporous silica MCM-41 modified by incorporation of the pyrrolidinium-based ionic liquid 1-methyl-1-butyl-pyrrolidinium bis(trifluoromethanesulfonyl)imide ([C4PYR](+)[TF2N](-)) at two different loadings: similar to 21 and 42% by weight, hereinafter referred to as MCM-41-IL1 and MCM-41-IL2, respectively. Although MCM-41-IL1 showed significantly higher adsorption of pure CO2 than pristine MCM-41, the amounts of pure N-2 and CH4 adsorbed on MCM-41-IL1 were only slightly higher. Molecular dynamics simulation of pure CO2 in ionic liquid-loaded MCM-41 models revealed that CO2 molecules prefer locations near the pore walls as well as in the pore interior around ionic liquid molecules. GCMC simulations of gas mixture adsorption (CO2/N-2 and CO2/CH4) showed that CO2 adsorption is highest in MCM-41-IL1 and least in pure MCM-41. The CO2/N-2 and CO2/CH4 selectivities at 298.15 K and 1 bar followed the trend MCM-41-IL2 MCM-41-IL1 MCM-41 with values for MCM-41-IL2 almost twice those for pure MCM-41. Thus, modifying the mesopores of MCM-41 with ionic liquid can result in significant enhancement in CO2 adsorption and selectivity.