Facile synthesis of CuCr2O4 spinel nanoparticles: a recyclable heterogeneous catalyst for the one pot hydroxylation of benzene

Abstract

A facile hydrothermal synthesis method is developed to prepare CuCr₂O₄ spinel nanoparticle catalysts with sizes between 25–50 nm. A detailed characterization of the material was carried out by XRD, ICP-AES, XPS, EXAFS, SEM, TEM, and TGA. XRD revealed the formation of a CuCr₂O₄ spinel phase and TEM showed the that particles size was 20–50 nm. The catalyst was highly active for the selective oxidation of benzene to phenol with H₂O₂. The influence of reaction parameters such as temperature, solvent, substrate to oxidant molar ratio, reaction time, etc. were investigated in detail. The reusability of the catalyst was tested by conducting the same experiments with the spent catalyst and it was found that the catalyst did not show any significant activity loss, even after 5 reuses. A benzene conversion of 72.5% with 94% phenol selectivity was achieved over this catalyst at 80 °C. However, significant H₂O₂ decomposition occurs on the catalyst, necessitating its usage in five-fold excess.