Selective oxidation of benzyl alcohol to benzaldehyde with H2O2 in water on epichlorohydrin-modified Fe3O4 microspheres

Abstract

Epichlorohydrin (ECH)-modified Fe₃O₄ microspheres were prepared in ethylene glycol by either in situ or post-synthetic modification and characterized via XRD, SEM, FTIR and VSM techniques. Modification by ECH was found to significantly enhance the catalytic activity of Fe₃O₄ microspheres in the selective oxidation of benzyl alcohol to benzaldehyde with H₂O₂ (yield: 8% vs. 34% before and after modification by ECH, respectively). Fe₃O₄ microspheres were magnetically recoverable and reusable at least five times without loss of catalytic activity and selectivity after being rejuvenated by a combined activation procedure comprising NaBH₄ reduction and ECH modification. Theoretical and experimental investigations confirmed that the ECH-modification promoted the adsorption and decomposition of H₂O₂ on Fe₃O₄ microspheres via hydrogen bonding and facilitated the formation of hydroxyl radicals by increasing the collision frequency between H₂O₂ and Fe₃O₄ by about 10 orders of magnitude, which contributed to much better catalytic activity of ECH-modified Fe₃O₄ microspheres.