Enhanced CO₂ Separation Selectivity in Oligo(ethylene glycol) Functionalized Room-Temperature Ionic Liquids

Abstract

Novel imidazolium-based room-temperature ionic liquids (RTILs) with one, two, or three oligo(ethylene glycol) substituents were synthesized. Solubilities and ideal solubility selectivities of CO2, N2, and CH4 at low pressure (1 atm) in these RTILs were determined using a pressure decay technique. Comparison to corresponding alkyl analogues of these RTILs reveals similar levels of CO2 solubility but lower solubilities of N2 and CH4. As a consequence, RTILs with oligo(ethylene glycol) substituents were observed to have 30−75% higher ideal solubility selectivities for CO2/N2 and CO2/CH4.