CO2 capture by quenched quaternary ammonium ionic liquid-propanol mixtures assessed by Raman spectroscopy

Abstract The hydrophobic quaternary ammonium ionic liquid (IL), N-trimethyl-N-butylammonium bis (trifluoromethanesulfonyl) imide [N4111][TFSI] with a 2-propanol additive captures significant normal CO2 (nCO2) at room temperature and ambient pressure. The 2-propanol-based mixture promotes conductivity under the nCO2 circumstance. To investigate the conformational changes induced by nCO2 important for its storage ability, Raman spectroscopy measurements on quenched quaternary ammonium IL-propanol mixtures are systematically conducted. Through liquid nitrogen quenching, the Raman intensities indicating the repulsive molecular interaction between 2-propanol and nCO2 are clearly observed, and exhibit distinct nCO2 mixing. The quenched [N4111][TFSI]-propanol mixtures highlighted that the cation-anion interaction was modified by the 2-propanol additive. Freezing sites of nCO2 correspond to amount of the nCO2 capture.