Nanomagnet-Supported Partially Brominated Manganese-Porphyrin as a Promising Catalyst for the Selective Heterogeneous Oxidation of Hydrocarbons and Sulfides in Water

A novel, magnetically recoverable porphyrin catalyst has been prepared by the coordinative anchoring of the [Mn(Br2TPP)OAc] complex on silica-coated magnetic nanoparticles (Fe3O4@SiO2, SMNP) through an amine functionality. The heterogeneous catalyst was characterized by powder X-ray diffraction, transmision electron microscopy, scanning electron microscopy, and FTIR spectroscopy. The catalyst loading on the magnetic support was determined by thermogravimetric (TG) analysis and inductively coupled plasma atomic emission spectroscopy. The catalyst nanoparticles were estimated to have a diameter of less than 10 nm. The TG curve demonstrated that the nanocatalyst was thermally stable up to almost 350 degrees C, exhibiting high thermostability. The epoxidation of olefins and the oxidation of saturated hydrocarbons to the corresponding ketones as well as sulfides to sulfones in an aqueous solution of tetra-n-butylammonium peroxomonosulfate (n-Bu4NHSO5, TBAOX) were efficiently enhanced with excellent selectivity under the influence of the magnetically separable catalyst. Sulfoxides could also be selectively produced in a mixture of water and ethanol, which makes the title methodology a good alternative for both sulfoxide and sulfone production. The separation and recycling of the catalyst and the byproduct of the oxidant were simple, effective, and economic in this clean oxidation method. FTIR and leaching experiments after seven successive cycles showed that the catalyst was very strongly anchored to the SMNP support.