Liquid-liquid equilibrium studies on the removal of naphthalene / 2-methylnaphthalene / dibenzothiophene from model oil using ionic liquids

Liquid-liquid extraction, has been used as an alternative method, for the dearomatization and desulfurization of a model oil using ionic liquids (ILs). The most recent work employs six ILs of high selectivity to aromatic and sulfur-containing compounds in ternary liquid-liquid equilibrium (LLE) systems. The best three ILs from the LLE ternary systems were used in a model multicomponent systems. The ILs were selected as extractive solvents for the extraction of naphthalene (N), 2-methylnaphthalene (2MN) and dibenzothiophene (DBT) from 1,3-diisopropylbenzene (1,3DIPB) in the ternary LLE data. Ternary mixtures of {IL (1) + N, or 2MN, or DBT (2) + 1,3DIPB (3)} and multicomponent mixtures {IL + N + 2MN + DBT + 1,3DIPB} were investigated at temperature T = 313.15 K and pressure 101 kPa. For this reason, the imidazolium-, pyridinium- and morpholinium-based ILs were selected: 1-ethyl-3-methylimidazolium dicyanamide, [EMIM][DCA], 1-allyl-3-methylimidazolium dicyanamide, [AMIM][DCA], 1‑butyl‑3-methylimidazolium tiocyanate, [BMIM][SCN], 1‑butyl‑4-methylpyridinium dicyanamide, [B4MPy][DCA], N-(2-hydroxyethyl)pyridinium tricyanomethanide, [Py2OH][TCM] and (3-hydroxypropyl)-1-methylmorpholinium dicyanamide, [NC3OHMMOR][DCA]. The suitability of the ILs as extractive solvents has been evaluated in terms of solute distribution ratio and selectivity. All the ILs showed high selectivity in the extraction of N, 2MN and DBT from 1,3DIPB in ternary and multicomponent systems. All LLE experimental data were correlated with the NRTL model. The highest extraction efficiency of N, 2MN and DBT in LLE data was observed for [B4MPy][DCA] (22.3 wt%, 36.8 wt% and 45.5 wt%, respectively). Much higher extraction efficiency was obtained in extraction of N, 2MN and DBT from the model oil stream in a single extraction stage (2IL:1 M.Str., m/m) and in two-stage extraction (2IL:1 M.Str., m/m). The extraction efficiency of N, 2MN and DBT from the model oil stream (2IL:1 M.Str., m/m) was 71.1 wt%, 80.4 wt% and 76.4 wt%, with [BMIM][SCN], or 69.3 wt%, 86.4 wt% and 82.9 wt% with [B4MPy][DCA], or 69.2 wt%, 69.4 wt% and 69.0 wt% with [AMIM][DCA], respectively in two-stage extraction.