Selective oxidation of styrene to benzaldehyde with H₂O₂ as oxidant on Mg-Fe spinel complex oxide catalysts was studied. Non-stoichiometric Mg-Fe spinel complex oxides are more active than pure MgFe₂O₄ spinel for the reaction. The yield reaches 20% on the former catalysts. Substituting Al³⁺ for Fe³⁺ in the non-stoichiometric Mg-Fe spinel complex oxide, the activity of the catalyst enhances and the highest yield is 33.4%. It is revealed that the non-stoichiometric Mg-Fe and Mg-Fe-Al spinel complex oxide catalysts are composed of nano-sized ferrite spinel and α-Fe₂O₃ crystallites by XRD, TEM and TPR techniques. The existence of nano-sized α-Fe₂O₃ crystallites in the non-stoichiometric Mg-Fe spinel complex oxide catalysts is also responsible for the enhanced catalytic activity besides the defect structure in them.

Key words: selective oxidation of styrene, benzaldehyde, Mg-Fe spinel complex oxide