Fuel Processing Technology, Vol.100, 55-62, 2012
Effects of anions on absorption capacity of carbon dioxide in acid functionalized ionic liquids
A series [Cmmim][X] of imidazolium cation-based ILs, with acid functional group on the alkyl side-chain has been synthesized and characterized by various techniques like H-1, C-13 NMR, MS-ESI, FTIR and EA. The absorption capacity of CO2 for various ILs was investigated at 30 and 50 degrees C at ambient pressure (0-1.6 bar). Specifically, the remarkable effect of different anions on CO2 absorption capacity has been evaluated with same cation. Acid functionalized ILs show significantly high absorption capacity for CO2. The CO2 absorption capacity of ILs increased with a rise in pressure and decreased when temperature was raised. Results showed that absorption capacity reached about 1.0 mol CO2 per mol of IL at 30 degrees C. The most probable mechanism of interaction of CO2 with ILs was investigated using FTIR and C-13 NMR and result shows that the absorption of CO2 in ether functionalized ILs is a chemical process. The CO2 absorption results and detailed study indicate the predominance of 1:1 mechanism, where the CO2 reacts with one IL to form carbamic acid. The CO2 absorption capacity of ILs for different anions follows the trend: BF4