Abstract
A series of first-row-transition-metal ferrite magnetic nanoparticles (NPs) MFe2O4 [M = Mn2+ (1), Fe2+ (2), Co2+ (3), Ni2+ (4), Cu2+ (5) or Zn2+ (6)] were prepared by the co-precipitation method and characterized by Fourier transform infrared (FTIR) spectroscopy, powder X-ray diffraction (XRD), scanning electron microscope - energy dispersive X-ray spectrometry (SEM-EDS), vibrating sample magnetometer (VSM) and X-ray photoelectron spectroscopy (XPS). Those NPs were used as catalysts for the microwave-assisted oxidation of various alcohols in solvent-free medium. MnFe2O4 (1), CoFe2O4 (3) and CuFe2O4 (5) act as catalysts for the conversion of alcohols to the corresponding ketones or aldehydes with a yield range of 81 to 94% in 2 h at 120 °C using t-BuOOH as an oxidant. These catalysts can be readily isolated by using an external magnet and no significant loss of activity is observed when reused up to 10 consecutive runs. The effects of some parameters, such as temperature, time, type of oxidant and presence of organic radicals, on the oxidation reactions were also investigated. The presented literature overview highlights the advantages of our new 1–6 NPs catalytic systems in terms of efficiency and economy, mainly due the used microwave (MW) heating mode.
Highlights
Nanotechnology knowledge can be applied to improve catalytic organic transformations where a nanometer dimension of a catalyst can enhance its activity, mainly due its high surface area per mass
A type of monodispersed nanomaterials that has been widely explored are spinel ferrites, applied in the fields of information recording, magnetic fluids, drug delivery and in vivo magnetic imaging, due their electronic, optical, electrical, magnetic and catalytic properties, which are different from their bulk counterparts [1,2,3,4,5,6]
In the Fourier transform infrared (FTIR) spectra of 1–6 NPs, signals related to metal oxide vibrations are observed below 1000 cm−1
Summary
Nanotechnology knowledge can be applied to improve catalytic organic transformations where a nanometer dimension of a catalyst can enhance its activity, mainly due its high surface area per mass (specific surface area). A type of monodispersed nanomaterials that has been widely explored are spinel ferrites, applied in the fields of information recording, magnetic fluids, drug delivery and in vivo magnetic imaging, due their electronic, optical, electrical, magnetic and catalytic properties, which are different from their bulk counterparts [1,2,3,4,5,6]. These spinel ferrites, with the standard formula MFe2 O4 , where M is a divalent cation, such as Mn(II), Fe(II), Co(II), Ni(II), Cu(II) or Zn(II), can offer more interesting catalytic activities compared to the corresponding single component metal oxides [7,8,9,10,11,12]. In the search for more economic and eco-friendly alternatives, nano-sized spinel ferrites
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