Heterogeneous catalytic oxidation of pyridines to N-oxides under mild conditions using tungsten-loaded TiO2

Abstract

The heterogeneous catalytic oxidation of pyridines to pyridine N-oxides has been studied using tungsten-loaded TiO2 as the catalyst and hydrogen peroxide as the green oxidant. The catalysts were synthesized by a simple impregnation technique and characterized by X-ray powder diffraction, Raman spectroscopy, transmission electron microscopy, energy dispersion X-ray spectroscopy, X-ray photoelectron spectroscopy. The catalytic performances of the catalysts were evaluated by the N-oxidation of pyridines with 30 wt% H2O2 solution as an environmentally friendly oxidant at room temperature. These processes serve as an efficient method to prepare a variety of pyridine-N-oxides in modest to high yields, and the pyridine N-oxides could be easily separated from the heterogeneous catalytic system. This study will provide a useful strategy for preparation of heterocyclic N-oxides in the mild condition.