Solubilities of the Gaseous and Liquid Solutes and Their Thermodynamics of Solubilization in the Novel Room-Temperature Ionic Liquids at Infinite Dilution by Gas Chromatography

The solubilities of C 2 H 4 and CO 2 and the interactions of polar and nonpolar solutes with the novel ionic liquids (ILs) 1-butyronitrile-3-methylimidazolium bis(trifluoromethylsulfonyl) imidate (CpMIm[NTf 2 ]), 1-butyronitrile-2,3-dimethylimidazolium bis(trifluoromethylsulfonyl) imidate (CpMMIm[NTf 2 ]), 1-butyronitrile-3-methylimidazolium dicyanamide (CpMIm[N(CN) 2 ]), 1-butyronitrile-2,3-dimethylimidazolium dicyanamide (CpMMIm[N(CN) 2 ]), 1-butyl-3-methylimidazolium palmitate (BMIm[ n -C 16 H 33 COO]), and 1-butyl-3-methylimidazolium stearate (BMIm[ n -C 18 H 35 COO]) were studied by gas chromatography at infinite dilution at T = (303.15, 313.15, 323.15, and 333.15) K. Henry's law constant k H of C 2 H 4 and CO 2 gas, infinite dilution activity coefficient γ ∞, molar enthalpies of solution Δ sol H ∞, and partial molar excess enthalpies of solution Δ H E∞ and of Gibbs energies Δ G E∞ were determined for polar and nonpolar solutes in these novel ILs. Compared with the 1,3-dialkylimidazolium ILs, cyano functional group substitution on the alkyl chain results in a remarkable decrease of the interactions of hydrocarbons. BMIm[ n -C 16 H 31 OO] and BMIm[ n -C 18 H 35 OO] demonstrate strong solubilization for both polar and nonpolar solutes. Straight lines of ln V g versus 1/ T and ln γ ∞ versus 1/ T were obtained for the majority of solutes in the temperature range. BMIm[NTf 2 ] and 1-octyl-3-methylimidazolium tetrafluoroborate (OMIm[BF 4 ]) show much better solubility for thiophene and are better solvents for the separations of thiophene from hydrocarbons.