A new stable inorganic bonded Lewis acid catalyst ((FeCl2)2-SiO3) was synthesized and applied for the liquid-phase catalytic nitration of benzene with NO2 to nitrobenzene in the presence of molecular oxygen. The results demonstrate that the inorganic bonded 10% (FeCl2)2-SiO3 catalyst showed excellent catalytic performance with 98.5% benzene conversion and 99.6% selectivity to nitrobenzene at 50 °C. Moreover, the catalyst maintained a high nitrobenzene yield after five cycles of reuse without significant deactivation. Characterization by XRD, XPS, UV–vis, FT-IR, and SEM consistently confirmed the successful bonding of FeCl3 onto the silica support. Theoretical calculations further confirm that the Si–O–FeCl2 sites in (FeCl2)2-SiO3 serve as the active catalytic sites in the nitration. A possible reaction mechanism for the nitration process was proposed. Oxygen promotes the activation of NO2, while the Lewis acid sites contribute to the stabilization of NO3–. This synergy facilitates the formation of a stable electrophilic reagent, thereby significantly enhancing the reaction efficiency. This work provides a mild, efficient, safe, and eco-friendly approach for highly selective preparation of nitrobenzene with promising potential for industrial application.
Zhao et al. (Mon,) studied this question.