Magnetically recoverable MFe12O19 nanoparticles as efficient and environmentally benign catalysts for gram-scale selective oxidation of olefins

Abstract

Catalytic oxidation is an efficient route for synthesizing oxygenated compounds such as epoxides and aldehydes. However, developing cost-effective, environmentally friendly and selective gram-scale catalysts, in full agreement with circular economy and green chemistry principles, remains a significant challenge. Herein, we report on MFe12O19 magnetic nanoparticles (MNPs) as a novel, magnetically recoverable and selective catalyst for the oxidation of olefins. Three different MFe12O19 (M = Cu, Sn and Sr) MNPs were synthesized using the coprecipitation method and characterized by XRD, FTIR, Raman, XPS, SEM-EDX, TEM, BET, zeta potential and 57Fe M & ouml;ssbauer spectroscopy. XRD analysis demonstrates that the patterns of SnFe12O19 and CuFe12O19 are totally different from those of the magnetoplumbite hexaferrite structure due to the confirmed coexistence by Rietveld refinements of SnO2-Fe2O3 and CuFe2O4-Fe2O3 as composite structures, respectively. In good agreement, Raman studies exclusively confirms the coexistence of MOx-Fe2O3 as a composite structure in MFe12O19, due to the presence of alpha-Fe2O3 and gamma-Fe2O3 as intermediate phases during the formation process of the hexaferrite structure. Moreover, the XPS and M & ouml;ssbauer results are consistent with the experimental evidence and spectroscopic characterizations. Subsequently, the catalytic activity of the as-synthesized MNPs was evaluated for the oxidation of styrene as a model olefinic substrate. Among the as-prepared MFe12O19 MNPs, the composite structure CuFe2O4-Fe2O3 in CuFe12O19 effectively enhances catalytic activity, selectivity and reusability due to the synergistic catalytic effect within a single magnetically recoverable nanostructure. Overall, MFe12O19 MNPs present a facile and greener approach using magnetically recyclable hexaferrites for selective catalytic oxidation reactions.