Room temperature selective conversion of aniline to azoxybenzene over an amorphous niobium oxyhydroxide supported on δ-FeOOH.

Abstract

In this work, catalysts for the oxidation of aniline into azoxybenzene were prepared by combining δ-FeOOH nanoparticles with 0, 2.5, 5, and 10 wt.% niobium oxyhydroxides by a simple co-precipitation method. The niobium oxyhydroxide actively changed the chemical and textural properties of δ-FeOOH, as verified by XRD, Mössbauer spectroscopy, N2 adsorption-desorption measurements, and TEM images. Therefore, the catalytic performance of δ-FeOOH to convert aniline into azoxybenzene in the presence of hydrogen peroxide was significantly improved. The catalytic activity and selectivity changed with the Nb content in the composite. The effect of different reaction parameters like solvent type, H2O2 volume, and reaction time has been studied in detail. The catalyst with 10 wt.% Nb was the most efficient among the evaluated catalysts, showing 100% conversion of aniline with 80.2% selectivity to azoxybenzene when propanol was used as solvent at 25 °C. Moreover, the catalyst 10 wt.% Nb exhibited good stability and could be reused for various cycles without significant loss of catalytic activity.