Solubility of Carbon Dioxide in Five Promising Ionic Liquids

According to many environmental aspects, the use of ionic liquids as potential solvents for CO2 capture and natural gas sweetening processes has gained much attention from many researchers in recent years. This research experimentally determines the solubility of CO2 in five ionic liquids: triethylsulfonium bis(trifluoromethylsulfonyl)imide ([S222][Tf2N]), diethylmethyl(2-methoxyethyl)ammonium bis(trifluoromethyl sulfonyl)imide ([deme][Tf2N]), 1-propyl-3-methylimidazolium bis(trifluoro methylsulfonyl) imide ([pmim] [Tf2N]), 1-allyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([amim][Tf2N]), and 1-butyl-4-methyl pyridinium tetrafluoroborate ([4mbp][BF4]) at (313.15, 323.15 and 333.15 K) and pressures up to 20 bar using a gravimetric microbalance. The solubility of CO2 diminished in the following sequence: [deme][Tf2N]> [pmim][Tf2N] > [amim][Tf2N] > [S222][Tf2N] > [4mbp][BF4]. The solubility of CO2 in these ionic liquids increased as temperature decreased. Four studied ionic liquids, [deme][Tf2N], [pmim][Tf2N], [amim][Tf2N], [S222][Tf2N] are deemed promising because of high CO2 solubility with a physical absorption when compared to [hmim][Tf2N]. These physical solvents have lower solubility than [bmim][Ac] which exhibited a strong chemical absorption and the reported formation of a chemical complex. Henry’s law constants for the investigated ionic liquids were derived.