Selective Extraction of Neutral Nitrogen-Containing Compounds from Straight-Run Diesel Feed Using Polymer-Supported Ionic Liquid Moieties

The extraction of trace polar compounds, among them neutral nitrogen-containing compounds (N-compounds), has received much attention from refiners because of their inhibiting effect on the hydrodesulfurization (HDS) process. Recently, we have shown that chloride-based ionic liquids (ILs) can selectively extract N-compounds from straight-run diesel feeds. However, the measurable solubility of ILs in hydrocarbon fuel is not a desired outcome of the process. Thus, the covalent binding of ILs moieties on polymers was studied. Starting from Merrifield resin, three resins were prepared with imidazolium, pyridinium, and triethylammonium chloride functionality. The resins were evaluated using a synthetic solution with dibenzothiophene and carbazole as model compounds, and a high selectivity for N-compounds was found. Imidazolium and pyridinium resins were then further evaluated using straight-run diesel feed containing 13400 ppm S and 105 ppm N. The selectivity toward N-compounds was comparable to the selectivity observed with ILs. Moreover, the resins could be easily regenerated using a protic solvent like methanol.