Deep extractive denitrogenation with Cu‐based ionic liquids and mechanistic insights

Abstract A major challenge in the extractive denitrogenation (EDN) of fuel oils lies in achieving high nitrogen removal efficiency with minimal extractant usage. To address this, a series of Cu‐based ionic liquids (ILs) ([Bmim]Cl/CuCl 2 ‐ X ) with different cation‐to‐anion ratios were synthesized and characterized. The cation‐to‐anion ratio was found to be crucial in determining the predominant anions present in the ILs. Among the synthesized Cu‐based ILs, [Bmim]Cl/CuCl 2 ‐1 exhibited outstanding EDN performance, achieving 100% nitrogen removal with minimal ionic liquid consumption. The anion [CuCl 3 ] − was identified as playing a key role in the EDN process, where the unoccupied orbitals of Cu and the chloridion in [CuCl 3 ] − facilitate effective coordination with nitrogen atoms in organic nitrogen compounds. This coordination forms Lewis acid–base interactions, which are essential for deep EDN. The study not only introduces an efficient Cu‐based ionic liquid but also provides insights into optimizing ionic liquid design for better extraction performance.