Selective Extraction and Identification of Neutral Nitrogen Compounds Contained in Straight-Run Diesel Feed Using Chloride Based Ionic Liquid

Extraction of neutral nitrogen-containing compounds (N-compounds) has been investigated with chloride based ionic liquids (ILs) with varying cation classes (imidazolium, pyridinium). ILs were first discriminated by their mutual solubility of ILs and model fuel. Low solubility of 1-butyl-3-methylimidazolinium chloride (BMImCl) and 1-octylpyridinium chloride (OcPyCl) in the model fuel was observed. The ILs were then evaluated using a synthetic solution with dibenzothiophene and carbazole as model compounds, and a high selectivity for N-compounds was found. BMImCl and OcPyCl were then evaluated using straight-run diesel feed, containing 13 400 ppm S and 105 ppm N. An extraction of up to 50% of the N-compounds was obtained in one step whereas the sulfur concentration reduction was only 5%. Both ILs can be regenerated using small amount of water. Extracted compounds could be then extracted using toluene. The major constituents were identified by GC-MS. Analysis of the extracted compounds emphasized the selectivity of the extraction process. Furthermore, refractory sulfur-containing compounds (S-compounds) and polyaromatics were also identified in the extract.