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

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 degrees C. However, significant H2O2 decomposition occurs on the catalyst, necessitating its usage in five-fold excess.