Phase behaviour of 1-methyl-3-octylimidazolium bis[trifluoromethylsulfonyl]imide with thiophene and aliphatic hydrocarbons: The influence of n-alkane chain length

This paper reports the results of a new experimental study on the capacity of an ionic liquid to extract a sulfur compound from its mixtures with aliphatic hydrocarbons. With this aim, liquid + liquid equilibrium data of ternary systems containing 1-methyl-3-octyl-imidazolium bis(trifluoromethylsulfonyl)-imide (C₈mim]NTf₂]), thiophene and n-hexane, n-heptane or n-hexadecane have been determined at T = 298.15 K. All systems showed high solubility of thiophene in the ionic liquid and low solubility of the ionic liquid in the n-alkane. The solute distribution coefficient decreases and the selectivity increases as the chain length of n-alkane increases. Both parameters are higher than unity in most of the cases. The experimental results have been correlated using NRTL activity coefficient model, and large deviations from experimental data have been found at high concentrations of thiophene with the heaviest hydrocarbons.