Isomer effect in the separation of octane and xylenes using the ionic liquid 1-ethyl-3-methylimidazolium bis{(trifluoromethyl)sulfonyl}amide

The liquid–liquid equilibria of three ternary systems comprising the aliphatic hydrocarbon octane, an aromatic hydrocarbon 1,n-(CH3)2C6H4 (where n takes the values 2, 3, or 4; that is, o-xylene, m-xylene, or p-xylene), and the ionic liquid 1-ethyl-3-methylimidazolium bis{(trifluoromethyl)sulfonyl}amide ([C2mim][NTf2]), were experimentally determined at 25 °C. The results show a more favourable distribution ratio towards the ionic liquid-rich phase for 1,2-(CH3)2C6H4 than for 1,3-(CH3)2C6H4 or 1,4-(CH3)2C6H4. Although selectivity values prove that it is feasible to separate the aliphatic and aromatic hydrocarbons by using [C2mim][NTf2] as solvent, no significant differences are observed in the selectivity among systems. Thus, the proposed ionic liquid does not look suitable to perform the separation of the different xylene isomers in a mixture. The experimental data were satisfactorily correlated by means of the classical ‘non-random two-liquid’ (NRTL) model.