Catalytic aerobic oxidation of 5-hydroxymethylfurfural into 2,5-diformylfuran over VO2+ and Cu2+ immobilized on amino-functionalized core–shell magnetic Fe3O4@SiO2

Abstract

Amino modified Fe₃O₄@SiO₂ (Fe₃O₄@SiO₂–NH₂) was used to immobilize Cu²⁺ and VO²⁺ for preparing Fe₃O₄@SiO₂–NH₂–Cu²⁺ and Fe₃O₄@SiO₂–NH₂–VO²⁺ catalysts. Various technologies had been used for the characteristics of catalysts, such as XRD, XPS, FT-IR, SEM, TEM and VSM. The catalytic performance of Fe₃O₄@SiO₂–NH₂–VO²⁺ in HMF oxidation could be significantly enhanced by the use of Fe₃O₄@SiO₂–NH₂–Cu²⁺ as the co-catalysts. The type of reaction solvents showed a great influence on the oxidation of HMF. The highest HMF conversion reached up to 98.7% at 110 °C in toluene with an optimal 2,5-diformylfuran yield of 85.5%. Moreover, the Fe₃O₄@SiO₂–NH₂–Cu²⁺ and Fe₃O₄@SiO₂–NH₂–VO²⁺ catalyst exhibited great stability and could be readily applied in the next recycle after magnetic separation.