Extractive denitrogenation of shale oil using imidazolium ionic liquids

The potential applications of shale oil as a substitute energy source are adversely influenced due to its high nitrogen content. In this work, four imidazolium ionic liquids (ILs), i.e., 1-butyl-3-methylimidazolium chloride ([Bmim]Cl), 1-butyl-3-methylimidazolium acetate ([Bmim]Ac), 1-butyl-3-methylimidazolium acetate/ZnAc2 ([Bmim]Ac/ZnAc2) and 1-butyl-3-methylimidazolium chloride/ZnAc2 ([Bmim]Cl/ZnAc2), were used to extract the basic nitrides and neutral nitrides from shale oil. The influence of extraction time, temperature, properties of N-compounds, ILs structure, mass ratio of IL/oil, multiple cycles of denitrogenation, physical mixing of ILs and ILs recyclability on extractive denitrogenation was systematically investigated. The denitrogenation performance of all ILs was determined and investigated from micro-level view with σ-profile. It was observed that, ILs composed of anions with weaker HB acceptor capacity, have the higher N-extraction efficiency to the neutral nitrogen compounds with weaker HB acceptor capacity. More than 96% N-extraction efficiency was achieved at the end of a single extraction cycle for time < 10 min under 40 °C and 1 : 1 of IL: oil (w/w), especially 100% N-extraction efficiency was realized for carbazole and indole. The N-extraction efficiency up to 60.1% and 53.7% for real shale oil was realized by [Bmim]Ac and [Bmim]Ac/ZnAc2, respectively, which are about 10% better than other non-hydrodenitrogenation technologies. Moreover, [Bmim]Ac and [Bmim]Ac/ZnAc2 exhibited almost the same extractive denitrogenation performance after regeneration. This work has developed a new approach to lessen the nitrogen content of shale oil effectively and economically. [Display omitted]