Adsorptive Denitrogenation of Model Fuel with CuCl-Loaded Adsorbents: Contribution of Π-Complexation and Direct Interaction between Adsorbates and Cuprous Ions

Removing nitrogen-containing compounds (NCCs) from fuel is very important to protect the environment and catalysts in various processes, including hydrodesulfurization. In this study, the adsorptive denitrogenation (ADN) of quinolines (such as quinoline, 1,2,3,4-tetrahydoquinoline, and decahydroquinoline) was studied in a systematic way using a CuCl-loaded metal-organic framework (here MIL-100(Cr)) and activated carbon in order to understand ADN quantitatively. In this study, it was found that CuCl was effective for ADN via π-complexation and direct interaction, and the important role of Cu(I) in ADN could be defined. Quinolines with aromaticity could interact with Cu(I), mainly via π-complexation. However, quinolines without aromaticity interacted with Cu(I) through direct interaction (or basic N-Cu(I)). This direct interaction was only meaningful when there was no aromaticity in the NCCs; the ADN efficiency via direct interaction was relatively low (around 30% of π-complexation between the simple aromatic ring and Cu(I)). An aromatic ring containing nitrogen was more effective (by around 50%) than a simple aromatic ring (without nitrogen) in π-complexation.