An efficient environmentally friendly CuFe2O4/SiO2 catalyst for vanillyl mandelic acid oxidation in water under atmospheric pressure and a mechanism study

Abstract

With the aim of the green production of vanillin, a highly efficient environmentally friendly oxidation system was introduced to oxidize vanillyl mandelic acid (VMA) with a porous CuFe₂O₄/SiO₂ component nano-catalyst in aqueous solution under atmospheric pressure. The N₂ adsorption–desorption pattern indicated that CuFe₂O₄/SiO₂ possessed a much higher specific surface area (49.98 m² g⁻¹) than that of CuFe₂O₄ (5.02 m² g⁻¹), which further indicated that the SiO₂ substrate restrained the aggregation of CuFe₂O₄ nanoparticles. The conversion for VMA and selectivity for vanillin reached 98% and 96%, respectively, under atmospheric pressure. The excellent catalytic performance was attributed to the synergistic effect of the catalytic capacity of CuFe₂O₄ and the adsorption capacity for the reactant of SiO₂. Simultaneously, the effect of different reaction conditions for catalyst activity and selectivity were investigated. Furthermore, the probable mechanism of VMA oxidation was investigated by in situ ATR-FTIR, H₂-TPR, XPS and ¹H NMR. More importantly, the decarboxylation was verified to proceed in basic conditions rather than in conventional acidic conditions.