Low viscosity amino acid ionic liquids with asymmetric tetraalkylammonium cations for fast absorption of CO2

Abstract

Fifteen novel amino acid ionic liquids (AAILs) were prepared by the combination of several tetraalkylammonium cations with four amino acid anions ([Gly], [L-Ala], [β-Ala] and [Val]).The asymmetry of the tetraalkylammonium cations is shown to have a significant influence on the viscosity of the ionic liquids composed of amino acid anions, especially for the four triethylbutylammonium ([N2224])-based ionic liquids that have viscosities of lower than 60 mPa s, with the lowest being only 29 mPa s. The low viscosity tetraalkylammonium-based AAILs are further demonstrated to improve apparently the reaction and mass transfer rates of CO2 in the ionic liquids.