Selective oxidation of styrene to benzaldehyde using soft BaFe2O4 synthesized by citrate gel combustion method

Abstract

BaFe2O4 spinel type catalyst is synthesized by a simple and inexpensive one-step citrate gel combustion method, the only method to synthesize soft ferrite other than the Pechini method reported earlier. The precursor and oxide are well characterized by various techniques such as thermogravimetry–differential thermal analysis, Fourier transform IR, X-ray diffraction, X-ray florescence and scanning electron microscopy. The SEM images confirm coralloid morphology of BaFe2O4 catalyst. BaFe2O4 catalyst shows high activity for styrene oxidation in the presence of H2O2 (30%) as an oxidant in acetone as solvent. Gas chromatography and mass spectroscopy analysis revealed that, conversion of styrene takes place selectively to benzaldehyde up to 88.5 mol% as major product with 39.9% yield. The optimization and effect of various reaction conditions on styrene conversion and product distribution were also studied. Ultrasonication exposes active sites on the surface of catalyst and breaks the hydrophobic cluster to make the reagent available. Better catalytic activity of BaFe2O4 is due to different site preference energies of individual ions which depend on the ionic size of barium (1.35 Å) and iron (0.67 Å), the size of interstices and temperature. The catalyst can be reused with marginal loss in activity.

Keywords

• Soft BaFe2O4
• Sol gel combustion
• Coralloid morphology
• Site preference energy