The ionic liquid 1-ethyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate as alternative extractant for BTEX separation

Abstract

Previously, we proved that the ionic liquid (IL) 1-ethyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate ([emim][FAP]) is a promising candidate for natural gas sweetening. The reason is that the absorption capacity for CO2 is high, the selectivity for CO2/CH4 is good, and the IL shows low affinity for light hydrocarbons (CH4, C2H6, C3H8 and C4H10). In this study, capability of this IL for the extraction of aromatics from aliphatic+aromatic mixtures via liquid–liquid extraction is evaluated. Therefore, the solubilities of the liquid aliphatic hydrocarbons (hexane, heptane) and the liquid aromatic compounds (benzene, toluene, ethylbenzene, o-xylene (=BTEX)) in [emim][FAP] have been measured at different temperatures. The ternary liquid–liquid equilibrium (LLE) data for the ternary systems {hexane+benzene+[emim][FAP]}, {heptane+toluene+[emim][FAP]}, {octane+ethylbenzene+[emim][FAP]} and {octane+o-xylene+[emim][FAP]} have been measured at T/K=293.15 and atmospheric pressure. The solute distribution coefficient and selectivity have been calculated and analyzed. The influence of the chain length (both in the hydrocarbon and in the aromatic) has been studied. Moreover, in order to properly evaluate the capability of this IL for BTEX recovery, the experimental data have been compared with available data in literature. Finally, the experimentally determined LLE data have been correlated using the NRTL model. It was found that the studied IL show distribution coefficient and selectivities compared to other ILs.