Liquid-Liquid equilibria in extractive desulfurization of model diesel fuels: Ternary systems of n-paraffins (C12, C14 or C16), thiophene, and methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquids

ABSTRACT The continuing imperative to reduce sulfur oxide emissions from transportation fuels has intensified the search for efficient desulfurization strategies. In this work, a comprehensive thermodynamic investigation of extractive desulfurization was conducted using model diesel systems composed of n -dodecane, n -tetradecane, or n -hexadecane in the presence of a homologous series of methylimidazolium bis(trifluoromethylsulfonyl)imide ([Cₙmim][NTf₂]) ionic liquids. Liquid-liquid equilibrium (LLE) data for ternary mixtures containing thiophene were determined experimentally at 313.15 K and 101.3 kPa. The extraction performance was assessed through distribution ratios and selectivity values, with systematic evaluation of the effect of alkyl chain length in both the paraffinic solvent and ionic liquid cation. The experimental data were accurately correlated using the Non-Random Two-Liquid (NRTL) model, yielding excellent agreement with minimal root-mean-square deviations. The resulting ternary phase diagrams revealed high extraction efficiency, with distribution ratios between 2.20 and 3.39 and selectivity values in the range of 66-264. These findings demonstrate the promising potential of [Cₙmim][NTf₂] ionic liquids as tunable, thermodynamically favorable solvents for deep extractive desulfurization of hydrocarbon fuels.