Solubility of Ionic Liquid [Bmim]Ac in Supercritical CO2 Containing Different Cosolvents

The solubility of the ionic liquid (IL) 1-butyl-3-methylimidazolium acetate ([Bmim]Ac) in supercritical carbon dioxide (scCO(2)) with cosolvents, including ethanol, acetone, dimethyl sulfoxide (DMSO), and acetonitrile, was determined at 40, 50, and 60 degrees C and with a pressure up to 15.0 MPa. The results showed that the addition of cosolvents has a significant effect on the solubility of [Bmim]Ac in scCO(2). The ability of different cosolvents to enhance the solubility of [Bmim]Ac in scCO(2) is in the following order: ethanol > DMSO > acetone > acetonitrile. The solubility of [Bmim]Ac in the scCO(2)/cosolvent mixture increased dramatically as the cosolvent concentration exceeded 20.0 mol %. The effect of the temperature on the solubility is more complicated. The solubility of [Bmim]Ac in scCO(2)/cosolvent increased slowly when using ethanol as the cosolvent, decreased slowly when using acetone or acetonitrile as the cosolvent, and increased first and then decreased when using DMSO as the cosolvent as the temperature increased from 40 to 60 degrees C. Moreover, the values of solubility increased as the pressure increased from 8 to 15 MPa. The increased tendency in the high pressure area is more obvious. The maximum solubility is 3.66 x 10(-2) mol %, which can be obtained when using 26.0 mol % ethanol at 60 degrees C, 14.55 MPa, and the minimum solubility is 1.89 x 10(-4) mol %, which can be obtained when using 10.5 mol % DMSO at 40 degrees C, 9.93 MPa. The modified Christal equation was used to correlate the solubility data, and the average absolute relative deviations are in the range of 4.36-14.35%. The maximum correlation accuracy is obtained when using ethanol as the cosolvent, and the minimum value for the system is obtained when using DMSO as the cosolvent.