Extraction of aromatic nitrogen compounds from heptane using quinolinium and isoquinolinium based ionic liquids

In the present work, the ionic liquids: N-hexylisoquinolinium thiocyanate, [HiQuin][SCN], N-octylisoquinolinium thiocyanate, [OiQuin][SCN], N-hexylisoquinolinium bis{trifuoro-methylsulfonyl}imide, [HiQuin][NTf2] and N-octylquinolinium bis{trifuoromethyl-sulfonyl}imide, [OQuin][NTf2] have been investigated as a solvent for the separation of aromatic nitrogen compounds from heptane. Ternary (liquid + liquid) phase equilibria have been determined for the following systems: {[HiQuin][SCN], or [[OiQuin][SCN], or [HiQuin][NTf2], or [OQuin][NTf2] + pyridine + heptane} and for {[OiQuin][SCN}] + 3-methylpyridine + heptane} at temperature T = 298.15 K at atmospheric pressure. The influence of ionic liquid structure on the separation of aromatic nitrogen compounds from heptane was determined. High solubility of aromatic nitrogen compounds and particular complete immiscibility of heptane with the tested ionic liquids were observed. The experimental data were correlated using the NRTL equation, and the binary interaction parameters have been reported. The phase equilibria diagrams for the ternary mixtures including the experimental and calculated tie-lines have been presented. The values of selectivity and solute distribution ratios have been calculated based on experimental results and were compared to the literature data for other ionic liquids.