Surfactant Promoted Synthesis of CuCr2O4 Spinel Nanoparticles: A Recyclable Catalyst for One-Pot Synthesis of Acetophenone from Ethylbenzene

We report a facile hydrothermal synthesis method to prepare CuCr2O4 spinel catalyst nanoparticles 20−60 nm in size, mediated by cationic surfactant cetyltrimethylammonium bromide. Detailed characterization of the material was carried out by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, and inductively coupled plasma–atomic emission spectroscopy (ICP-AES). XRD analysis revealed the formation of a CuCr2O4 spinel phase and TEM analysis showed that the particle size was 20−60 nm. The catalyst was highly active for selective oxidation of ethylbenzene to acetophenone with H2O2. The influence of reaction parameters such as temperature, substrate-to-oxidant molar ratio, reaction time, etc. were investigated in detail. The reusability of the catalyst was tested by conducting same experiments with the spent catalyst, and it was found that the catalyst did not show any significant activity loss, even after five cycles of reuse. An ethylbenzene conversion of 68.5% with 78% acetophenone selectivity was achieved over this catalyst at a temperature of 70 °C. However, significant H2O2 decomposition takes place on the catalyst, necessitating its usage in 5-fold excess.