Equimolar carbon dioxide absorption by ether functionalized imidazolium ionic liquids

Abstract

A series [C3Omim][X] of imidazolium cation-based ILs, with ether functional group on the alkyl side-chain have been synthesized and structure of the materials were confirmed by various techniques like 1H, 13C NMR spectroscopy, MS-ESI, FTIR spectroscopy and EA. More specifically, the influence of changing the anion with same cation is carried out. The absorption capacity of CO 2 for ILs were evaluated at 30 and 50 °C at ambient pressure (0-1.6 bar). Ether functionalized ILs shows significantly high absorption capacity for CO2. In general, the CO 2 absorption capacity of ILs increased with a rise in pressure and decreased when temperature was raised. The obtained results showed that absorption capacity reached about 0.9 mol CO 2 per mol of IL at 30 °C. The most probable mechanism of interaction of CO 2 with ILs were investigated using FTIR spectroscopy, 13C NMR spectroscopy and result shows that the absorption of CO 2 in ether functionalized ILs is a chemical process. The CO 2 absorption results and detailed study indicates the predominance of 1:1 mechanism, where the CO 2 reacts with one IL to form a carbamic acid. The CO 2 absorption capacity of ILs for different anions follows the trend: BF4 < DCA < PF6 < TfO < Tf2N. Moreover, the as-synthesized ILs is selective, thermally stable, long life operational and can be recycled at a temperature of 70 °C or under vacuum and can be used repeatedly.