Nb2O5 as Heterogeneous Catalysts for the Selective Oxidation of Geraniol

Abstract

Catalytic application of niobium catalysts is presented in this work. The regioselective oxidation of geraniol was studied over niobium catalysts using hydrogen peroxide (H2O2) as oxidant in the absence of any organic solvent. The catalysts studied were crystalline Nb2O5 bulk, a mixed oxide of Nb2O5/SiO2 (N-S) and Nb2O5/SiO2 mesoporous (N-M). The catalysts were characterized by nitrogen adsorption– desorption isotherms at 77 K, X-ray diffraction (XRD) and UV-Vis. High selectivity to the allylic C=C double bond was observed in all catalysts studied. However, for Nb-M and N-S the selectivity to epoxide decreases with the conversion, contrary to observed for Nb2O5 bulk. The differences in selectivity may be due to different routes for the activation of oxidant over the metallic center. This work proposes a useful application of Nb2O5 commercially available in selective organic reactions. Keywords: Niobium catalysts, Green chemistry, Regioselectivity, Epoxidation, Geraniol, Hydrogen peroxide.