Use of a green and cheap ionic liquid to purify gasoline octane boosters

This work demonstrates the ability of the ionic liquid 1-ethyl-3-methylimidazolium ethylsulfate ([emim][EtSO4]) to act as an extraction solvent for liquid–liquid extraction and as an azeotrope breaker for extractive distillation, to separate the azeotropic mixture ethyl tert-butyl ether (ETBE) + ethanol, thus purifying the tertiary ether, which is the most used additive to improve the octane index of gasolines. To assess the suitability of [emim][EtSO4] to perform the mentioned separation, the liquid–liquid equilibrium (LLE) at 298.1 K and the isobaric vapour–liquid equilibrium (VLE) at 101.3 kPa have been determined for the ternary system ETBE + ethanol + [emim][EtSO4]. The separation sequence for the extractive distillation has been obtained from the residue curve map and checked by simulation. The equilibrium data have been adequately correlated by means of the NRTL equation, thus facilitating their computerized treatment.