Comparative study of the LLE of the quaternary and ternary systems involving benzene, n-octane, n-decane and the ionic liquid [BMpyr][NTf2]

• The ionic liquid BMpyrNTf2 was evaluated as solvent to extract benzene from alkanes.
• The quaternary system {octane + decane + benzene + BMpyrNTf2} was determined.
• A comparison of results for ternary and quaternary systems was performed.
• Experimental data were successfully correlated using the NRTL model.

In this work, the suitability of the ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, [BMpyr][NTf2], as an extraction agent to replace the traditional organic solvents in the separation of aromatic/aliphatic hydrocarbons was evaluated. Following this aim, the (liquid + liquid) equilibrium (LLE) of the quaternary system {n-octane (1) + n-decane (2) + benzene (3) + [BMpyr][NTf2] (4)} and its corresponding ternary systems {n-octane or n-decane (1) + benzene (2) + [BMpyr][NTf2] (3)} was determined at T = 298.15 K and at 101.3 kPa. Solute distribution ratio and selectivity were calculated from the experimental LLE values in order to evaluate the capability of this ionic liquid to accomplish the separation of benzene from its mixtures with n-octane and n-decane. A comparison of the results obtained from the LLE results of the ternary and quaternary systems was carried out. Finally, the experimental tie-lines compositions were correlated using the NRTL thermodynamic model.