Extraction of nitrogen compounds from diesel fuel using imidazolium- and pyridinium-based ionic liquids: Experiments, COSMO-RS prediction and NRTL correlation

1-Ethyl-3-methylimidazolium ethyl sulfate ([EMIM][EtSO4]), 1-ethyl-3-methylpyridinium ethyl sulfate ([EMPY][EtSO4]) and 1-ethyl-3-methylimidazolium methanesulfonate ([EMIM][MeSO3]) ionic liquids were investigated to remove pyrrole, indoline, pyridine and quinoline nitrogen compounds from n-hexadecane. Twelve sets of ternary liquid–liquid equilibrium experiments were conducted at room temperature and atmospheric pressure with feed concentrations of nitrogen compounds ranging between 5 and 50 wt%. The ternary phase diagrams for all systems show positive slope, indicating that small amount of solvent is sufficient to remove the nitrogen compounds. Based on the values of distribution coefficient and selectivity, all three ionic liquids are potential solvents for removal of nitrogen compounds, but more effective in removing 5-membered compounds (pyrrole, indoline) than 6-membered compounds (pyridine and quinoline). COSMO-RS predictions of the ternary tie-lines were in good agreement with experimental results (RMSD < 5%). The experimental data were also correlated using the NRTL model with excellent agreement (RMSD < 1%).