Study on the adsorptive denitrification performance of MIL-101(Cr) and its theoretical calculation

The adsorptive denitrification performance of MIL-101(Cr)-0.5 toward pyridine, aniline or quinoline in simulated fuels with basic nitrogen content of 1732 μg/g was evaluated separately. Furthermore, the effects of adsorption temperature, adsorption time and adsorbent dosage on their adsorptive denitrification performance were systematically investigated. The experimental results demonstrated that under a fixed adsorbent dosage of 0.05 g and a simulated fuel volume of 10 mL, the optimal removal efficiency for aniline was achieved at 30 ℃ within 30 min, whereas higher temperatures and longer times (40 ℃ and 40 min) were required for effective removal of pyridine and quinoline. Density Functional Theory (DFT) calculations were conducted via Materials Studio (MS) software to study the adsorptive denitrification mechanism of MIL-101(Cr) toward these three basic nitrogen-containing compounds. The simulation calculation results revealed that the interaction between pyridine and MIL-101(Cr) primarily involved coordination adsorption. In contrast, the interaction between aniline or quinoline and MIL-101(Cr) proceeded mainly through coordination, with additional contributions from π-complexation and hydrogen bonding. The overall adsorption strength order is pyridine > aniline > quinoline. During the adsorption process, pyridine and quinoline transfer electrons to the MIL-101(Cr) surface through the H→C→N→Cr3+ pathway, while aniline transfers electrons to the MIL-101(Cr) surface through various pathways, including N→Cr3+, N→C→Cr3+ and N→H→O. Furthermore, adsorption kinetics studies indicated that the adsorption processes for all three basic nitrogen-containing compounds followed the quasi second order kinetic models. The experimental results on the effect of benzene on the adsorptive denitrification performance of MIL-101(Cr)-0.5 demonstrated that benzene exerted a more significant impact on the adsorption of aniline and quinoline. Finally, the adsorbent was regenerated using ethanol washing. It was found that MIL-101(Cr)-0.5 retained stable denitrification performance after two regeneration cycles.