Thermal Plasma-processed Natural Hydroxyapatite-MnO۲ Nanoparticles as a Reusable and Green Heterogeneous Catalyst for Aerobic Oxidation of Benzylic Alkyl Arenes and Alcohols

In the present work, we have reported the in situ oxidation of manganese (II) acetate to MnO۲ nanoparticles through the thermal plasma carbonized natural hydroxyapatite (MnO۲/TP-NHAp) as a neoteric sustainable method. Interestingly, the thermal plasma-processed surface of the NHAp shows a great ability for oxidation of the manganese (II) without need of any external oxidizing agents. The catalyst was characterized by X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), thermogravimetric analysis (TGA), flame atomic absorption spectroscopy (FAAS), Fourier transform infrared (FT-IR), scanning electronic microscopy (SEM), and energy dispersive spectroscopy (EDS). The catalytic activity of MnO۲/TP-NHAp was investigated in the selective aerobic oxidation of alcohols and benzylic alkyl arenes at ۸۰ °C in toluene under an atmospheric pressure of air as a source of oxidant. Since the catalyst can be easily recovered and reused at least for four consecutive cycles without losing significant activity and selectivity, it showed admirable potential in reusable catalysis.

Keywords:

Natural hydroxyapatite , Thermal plasma-processed , Heterogeneous catalyst , Aerobic oxidation , MnO۲ nanoparticle