Synthesis, Characterization, and Catalytic Properties of Hollow γ-Fe2O3 Spheres toward Liquid-Phase Oxidation Using Hydrogen Peroxide

Hollow gamma-Fe2O3 nanospheres were synthesized using earboxylated polystyrene spheres as a core template by thermal treatment followed by calcination. The obtained material was characterized by FT-IR, N-2 adsorption desorption, TEM, XRD, and Fe K-edge XAFS measurements. The size of the hollow gamma-Fe2O3 nanospheres were about 400-500 nm, which was assembled from primary particles with a size of approximately 10-20 nm. The phase transition of the composed particles from magnetite (Fe3O4) to maghemite (gamma-Fe2O3) was identified after calcination in the presence of 02 at relatively low temperature. The hollow gamma-Fe2O3 acted as an efficient heterogeneous catalyst for the liquid-phase selective oxidation of 1-phenylethanol using hydrogen peroxide (H2O2) as an oxidant. It exhibited enhanced catalytic activity compared to its bulk counterpart and also showed higher selectivity than nanosized gamma-Fe2O3. Recovery of the hollow gamma-Fe2O3 nanospheres from the reaction mixture could be attained by applying an external permanent magnet, and the spent catalyst could be recycled without any appreciable loss of its inherent catalytic ability.