Synthesis of ionic liquids and their use for extracting nitrogen compounds from gas oil feeds towards diesel fuel production

Seventeen ionic liquids (ILs), containing imidazole (7) and quaternary ammonium groups (10), were tested in the removal of nitrogen compounds present in the gas oil feed for diesel fuel production. A model mixture composed by quinoline, indole, and carbazole in hexadecane/toluene was used to run experiments with a Feed/IL ratio of 20/1 and 30 °C. In general, the synthesized ILs presented higher removals of indole and carbazole than of quinoline. Additionally, when the carbon number of the carboxylate counterpart of the quaternary ammonium ILs increased, the carbazole removal increased. Further experiments using model mixtures that contained also benzothiophene and benzothiophene and aniline, showed that none of these added compounds affected the ILs solubility for indole and carbazole under the same experimental conditions. Experiments carried out in a batch setup using straight run gas oil (SRGO) proved that only triethylmethylammonium butyrate and triethylmethylammonium acetate of all the ILs selected, presented good nitrogen removal capabilities and adequate chemical stabilities at the experimental conditions used. Therefore, they were chosen for a dynamic study that showed that a 30% organic nitrogen extraction could be attained when 200 and 170 mL per gram of material had passed before a regeneration process was required.