Nanoclusters of Cu(II) supported on nanocrystalline W(VI) oxide: a potential catalyst for single-step conversion of cyclohexane to adipic acid

A facile hydrothermal synthesis method is developed to prepare Cu(II) nanoclusters supported on a nanocrystalline W(VI) oxide catalyst with sizes between 35 and 65 nm. Detailed characterization of the material was carried out by XRD, XPS, SEM, TEM, STEM-mapping, Raman, FTIR, TGA, UV-visible spectroscopy and ICP-AES. The catalyst was highly active for selective oxidation of cyclohexane to adipic acid with H2O2. The influence of reaction parameters such as temperature, substrate to oxidant molar ratio, reaction time, etc. was 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 4 reuses. A cyclohexane conversion of 75% with 88% adipic acid selectivity was achieved over this catalyst at 70 degrees C temperature.