Studies on styrene selective oxidation over iron-based catalysts: Reaction parameters effects

• Mesoporous MnFe is active for styrene oxidation with outstanding reusability along 72 h.
• Catalyst screening, effect of temperature and efficiency of the H2O2 were deeply studied.
• Synergistic effect of Fe with Co and Mn promoters to produce benzaldehyde and styrene oxide.
• Using acetone, good performances due to oxidation of MnFe2O4 phase.
• Partial loss of catalyst structure of CoFe showed by Raman and ATR-FTIR.

Iron-based hydrotalcite catalysts such as MnFe, CoFe, CeFe, NiFe and MgFe as well as their single monoxides were screened for selective oxidation of styrene to obtain benzaldehyde and styrene epoxide. The catalysts were characterized by X-ray diffraction, ATR-FTIR and Raman spectroscopy, chemical analyses, scanning electron microscopy coupled to EDX and N2 adsorption–desorption measurements, before and after the catalytic evaluation. The influence of the reaction conditions such as temperature, reactant compositions as well as the presence of solvents was also evaluated. Best performances were reached by MnFe due to the presence of α-Fe2O3 and γ-Fe2O3 phases together with the stable MnFe2O4 one. These species allowed reaching 17% of styrene conversion and selectively produced benzaldehyde and styrene epoxide, after 72 h of reaction. Under these conditions, MnFe can be recycled by 3 times with a very low deactivation rate due to the partial loss of catalyst structure, after being characterized by Raman and ATR-FTIR.