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 sigma-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 degrees 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. (C) 2020, Institute of Process Engineering, Chinese Academy of Sciences. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co., Ltd.