Investigations of 1-(4-propylamino)-3-ethyl imidazolium tetrafluoroborate ionic liquid capturing CO2

Abstract

1-(4-propylamino)-3-ethyl imidazolium ([Paeim]+) Tetrafluoroborate([BF4]-) Ionic liquid (IL), capturing CO2, was explored systematically at B3LYP/6-311++G** and mp2/6-311++G** level. The stable geometries of ILs and capture products were optimized, the energies of these geometries were obtained and corrected by Zero-point-vibration-energy and basis set superposition error correction. The results show that the interactions between [Paeim]+and [BF4]-are mainly displayed as hydrogen bonds, but the interaction energies exceeds -328 kJ/mol. Further analysis found that the interactions are reinforced by charge dispersion and charge redistribution of ion-pair, and that electrostatic attraction contributes much to the interaction energies. This IL system capturing CO2belongs to the class of physical sorption with 1:1 molar absorption ratio, the absorption energy is nearly -18kJ/moland thus this IL may have low energy consumption when regenerated from IL-CO2.

Keywords

• ionic liquids
• CO2 capture
• physical sorption
• charge redistribution