Controlled synthesis of α- and γ-Fe2O3 nanoparticles via thermolysis of PVA gels and studies on α-Fe2O3 catalyzed styrene epoxidation

Fe2O3 nanoparticles with diameters in the 7-18 nm range have been synthesized via thermolysis of polyvinyl alcohol (PVA) gels prepared under alkaline pH by adding Fe3+ ions into warm aqueous solutions of PVA. While calcinations at 400 °C, 500 °C and 600 °C give γ-Fe2O3 as the pure product, α-Fe2O3 is obtained by heating the gel at 700 °C. It is found that the calcination temperature has a pronounced effect on the nature of the oxide produced but has little effect on particle size. The resultant Fe2O3 nanomaterials are ferromagnetic with moderate coercivities. Preliminary investigations suggest that hematite (α-Fe2O3) nanoparticles effectively catalyze the epoxidation of styrene with tert-butyl hydroperoxide (TBHP) as the terminal oxidant.