Solubilities of Carbon Dioxide and Oxygen in the Ionic Liquids Methyl Trioctyl Ammonium Bis (trifluoromethylsulfonyl) imide, 1-Butyl-3-Methyl Imidazolium Bis (trifluoromethylsulfonyl) imide, and 1-Butyl-3-Methyl Imidazolium Methyl Sulphate

International audienceIonic liquids (ILs) are being considered as solvents for gas absorption processes as they have the potential, in general, for improved efficiency of gas separations, as well as lower capital and operating costs compared to current commercial processes. In this study the solvent properties of ILs are investigated for use in the absorption of carbon dioxide (CO2) and oxygen (O2). The absorption of these gases in ILs was measured in a temperature range of 303.15 to 333.15 K and at pressures up to 1.5 MPa by gravimetric analysis. The ILs used were: methyl trioctyl ammonium bis (trifluoromethylsulfonyl) amide [MOA][Tf2N], 1-butyl-3-methyl imidazolium bis (trifluoromethylsulfonyl) amide [BMIM][Tf2N] and 1-butyl-3-methyl imidazolium methyl sulphate [BMIM][MeSO4]. The measurement technique employed in this study is fast, accurate, and requires small quantities of solvent. The results indicated that absorption of both gases increased with a decrease in operating temperature and an increase in pressure. [MOA][Tf2N] had the highest CO2 and O2 solubility. [BMIM][Tf2N] was determined to have the highest selectivity for CO2 absorption. [BMIM][MeSO4] achieved the lowest CO2 absorption with a moderate O2 absorption, revealing this IL to be the least desirable for CO2 and O2 absorption. Calculation of Henry’s law constants for both gases in all ILs at all isotherms confirmed the deductions made from absorption data analysis. The absorption data was modelled using the generic Redlich-Kwong cubic equation of state (RK-EOS) coupled with a group contribution method