CO₂ Capture at Room Temperature and Ambient Pressure: Isomer Effect in Room Temperature Ionic Liquid/Propanol Solutions

Abstract

A CO 2 capture system without supercritical CO 2 was optimized for mixtures of hydrophobic room temperature ionic liquids (RTILs) and propanol. We tested RTILs using bis(trifluoromethanesulfonyl)imide, TFSI- , anion and four quaternary ammonium cations, two quaternary phosphonium cations, and one imidazolium cation. The addition of 2-propanol into the RTILs clearly promoted the capture of normal CO 2 ( n CO 2 ) at ambient temperature and pressure. When combined with 2-propanol, the most efficient RTILs for n CO 2 capture were N -butyl- N , N , N -trimethylammonium TFSI- . This enhancement of n CO 2 capture was not observed in RTIL mixtures with 1-propanol or in propanol mixtures containing other phosphonium- and imidazolium-based RTILs. The torsion angle of TFSI- , which was calculated using density functional theory, is thought to be related to high n CO 2 capture efficiently.