Integrated investigation for extractive denitrogenation of fuel oils with Eco-friendly Piperazine-Based ionic liquids

It is of great significance to develop sustainable denitrogenation technology due to the presence of nitrogen compounds in fuel oils which have serious impact on its quality. To avoid the problems of incomplete denitrogenation and harsh operating conditions associated with conventional hydrodenitrogenation (HDN) process. The extractive denitrogenation method was adopted with ionic liquids-based (ILs-based) materials as extractants in this work. Through an overall review comparison revealed that ILs-based extractants consisting of conventional imidazole-based cations and fluorine-containing anions were toxic and hazardous to the environment. Therefore, four eco-friendly piperazine-based ionic liquids (Pi-based ILs) were synthesized as denitrogenation extractants by one-step method. The performance of the synthesized IL extractants in removing pyrrole from oil was evaluated by removal efficiency (RE). The polarity of each molecule in the system and the interaction between ILs and pyrrole were also analyzed. The conformational relationship between the denitrogenation performance and the structure of the ILs was revealed. The results showed that eco-friendly 1-methyl-piperazine lactate ([C1Pi][Lac]) exhibited the highest RE among the four Pi-based ILs, with the RE of 95.90 % for pyrrole under the optimal denitrogenation conditions: mIL: moil = 1, extraction temperature of 298.15 K, extraction time of 30 min, and standing time of 15 min. Then, the denitrogenation process was visual explored by the molecular dynamics (MD) simulation. In addition, [C1Pi][Lac] was regenerated and reused, which showed that the eco-friendly [C1Pi][Lac] could be completely regenerated and reused well. This study laid a solid foundation for the development of eco-friendly and sustainable denitrogenation process.