Liquid Phase Nitration of Benzene to Nitrobenzene Using a Mesoporous MoO3/Nb2O5 Nanocatalyst

Abstract

This work reports the synthesis of a mesoporous MoO₃/Nb₂O₅ catalyst by a facile co-precipitation method for the liquid phase nitration of benzene to nitrobenzene, which is a vital industrial reaction. Pristine Nb₂O₅ and MoO₃/Nb₂O₅ nanocatalysts were characterized using various techniques, including powder XRD, N₂ adsorption-desorption, Raman, SEM/TEM, pyridine FT-IR, and XPS. The MoO₃/Nb₂O₅ catalyst (10 wt% MoO₃ with respect to Nb₂O₅) showed uniform dispersion of Mo and Nb species, higher amount of oxygen vacancies, and more Brønsted acid sites, resulting in a 90% yield of nitrobenzene. In contrast, only 35 and 58% yields were obtained in the case of commercial Nb₂O₅ and nanosized Nb₂O₅, respectively. The liquid phase nitration of benzene was carried out using commercial 65% HNO₃ as a nitrating agent without sulfuric acid. The mesoporous MoO₃/Nb₂O₅ catalyst is structurally stable, as confirmed by the characterization of the spent catalyst. However, a gradual decrease in the yield of nitrobenzene was observed, which could be due to the leaching of MoO₃ species from the catalyst surface.