Solvent properties of functionalized ionic liquids for CO2 absorption

onic liqs. can be used as solvents for gas absorption operations in order to improve the process economy and general efficiency of gas sepns. This work investigates solvent properties of ionic liqs. and compares them to amine solns. used for absorption of carbon dioxide (CO2). The CO2 soly. into six different room temp. ionic liqs. (RTILs) was measured at temps. between 298-343 K and pressures up to about 1 MPa. The RTILs used were: [bmim]+[BF4]-, [bmim]+[DCA]-, and four imidazolium-based ionic liqs. paired with [DCA] and [BF4], in which the cation was functionalized with either a primary, tertiary amine or a hydroxyl group. The d., viscosity and surface tension of the studied RTILs were measured at temps. ranging from 293-363 K. The results showed that CO2 absorption behavior was affected by the functionalized chains appended to the RTILs cation. A chem. enhancement of the CO2 absorption was obsd. when functionalized RTILs were used as absorption solvents. It was possible to increase the ionic liq. volumetric gas load almost threefold by attaching functional groups to the ionic liq., whereas for the traditional amine solns. the max. gas load is stoichiometrically limited.