Catalytic oxidation of aromatic amines to azoxy compounds over a Cu–CeO2 catalyst using H2O2 as an oxidant

Abstract

We have prepared Cu-nanoparticles supported on nanocrystalline CeO₂ by a one pot hydrothermal method using cetyltrimethylammonium bromide (CTAB) surfactant. The prepared catalyst was characterised by XRD, SEM, TEM, XPS, TPR, EXAFS, BET-surface area and UV-Vis spectroscopy. This prepared catalyst was highly active for the selective oxidation of aromatic amines to corresponding N-oxides with very high yield. It was observed that 5–10 nm Cu-nanoparticles supported on 20–40 nm CeO₂ nanoparticles was formed when Cu loading was 3.8 wt%. 3.8 wt% Cu was the optimum loading to give maximum catalytic activity and above 3.8 wt% Cu loading due to the formation of agglomerated Cu species, catalytic activity decreases. The 3.8% Cu–CeO₂ catalyst showed 95% aniline conversion and 92% selectivity towards azoxybenzene formation using H₂O₂ as an oxidising agent. The effect of different reaction parameters like temperature, reaction time, substrates and H₂O₂ mole ratio were investigated in detail.