Extractive denitrogenation of model oils with tetraalkyl substituted pyridinium based ionic liquids

• Synthesis of two polysubstituted pyridinium based-ionic liquids.
• Physical properties of the pure ionic liquids measured at several temperatures.
• LLE data for ternary mixtures {heptane + nitrogen compound + IL}.
• Selectivity S and distribution ratio β values higher than 1.

The emission of sulfur and nitrogen oxides to the atmosphere caused by the presence of heterocyclic sulfur and nitrogen compounds present in fuel oils, is one of the main environmental issues worldwide and the major contributor for acid rain and global warming. In this work, the ability of two tetraalkyl substituted pyridinium-based ionic liquids as solvents for the denitrogentation of model fuels by liquid extraction was tested. For that purpose, the liquid–liquid equilibrium data for {heptane + pyrrole, pyridine + ionic liquid} ternary mixtures were experimentally determined at T = 298 K and at atmospheric pressure. The selected designed and synthesized ionic liquids were derived from the 1-butyl-3,5-dimethyl-2-pentylpyridinium [1B3M5M2PPy] cation, incorporating dicyanamide [N(CN)2] and bis(trifluoromethylsulfonyl) imide [NTf2] anions. The extraction power of these ionic liquids was evaluated in terms of selectivity and solute distribution ratio, which showed that heterocyclic nitrogen compounds are better extracted by the ionic liquid derived from dicyanamide anion than by that based on bis(trifluoromethylsulfonyl) imide. In any case, the obtained results using these ILs are very promising and they greatly improve the results achieved so far using other ILs.The new ionic liquid [1B3M5M2PPy][N(CN)2] was synthetized for the first time in this work and its physical properties (density, speed of sound, refractive index, viscosity) were measured at atmospheric pressure from T = (298.15 to 343.15) K. The decomposition temperature, thermal expansion coefficient, isentropic compressibility, and molar refraction for the pure ionic liquid were also calculated.