Efficient removal of basic heterocyclic nitrogen compounds from fuel oils by functionalized acidic ionic liquids: Extraction experiment and interaction exploration

It is a crucial procedure for eliminating nitrogen compounds from the fuel processing industry. Novel acidic ionic liquids (ILs) with functional groups can enhance the separation process, making it more effective and selective. In this study, two SO3H-functionalized tetramethylguanidine (TMG)-based ILs, namely [TMGPS]HSO4 and [TMGPS]H2PO4, were utilized as extractants to eliminate two common basic heterocyclic nitrogen compounds, pyridine and quinoline, from fuel oils. [TMG]HSO4 was used as a reference to examine and confirm the impact of functional sites on the removal of basic pyridine and quinoline. The extraction efficiency (EE) for the adopted ILs was measured, and their performance was analyzed. The results revealed that [TMGPS]HSO4 had a higher EE value than [TMGPS]H2PO4 under optimal conditions. Additionally, the EE values for pyridine and quinoline using [TMGPS]HSO4 were 99.56 % and 94.36 %, respectively. The polarity relationship during the extraction process was also investigated. Furthermore, the hydrogen bond interaction and acid-base coordination of functionalized acidic ILs with basic pyridine and quinoline were validated. These findings demonstrate the successful development of functional ILs for efficiently eliminating typical heterocyclic base nitrogen compounds from fuel oils.