CrossRef enabled

PAC Archives

Archive →

Pure Appl. Chem., 2012, Vol. 84, No. 3, pp. 765-777

Published online 2011-10-31

Aerobic oxidation of 5-hydroxymethylfurfural to 2,5-diformylfuran on supported vanadium oxide catalysts: Structural effect and reaction mechanism*

Junfang Nie and Haichao Liu*

National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Stable and Unstable Species, College of Chemistry and Molecular Engineering, Green Chemistry Center, Peking University, Beijing 100871, China

Abstract: The structure–activity relationship and reaction mechanism for selective oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-diformylfuran (DFF) in toluene were studied on vanadium oxide domains on TiO2, Al2O3, Nb2O5, ZrO2, and MgO and with a wide range of VOx surface densities. The structures of these catalysts were characterized by X-ray diffraction (XRD), diffuse reflectance UV–vis spectroscopy (UV–vis DRS), and Raman spectroscopy, and their reducibility was probed by H2-temperature programmed reduction. The structures of the VOx domains evolved from monovanadate to polyvanadate structures with increasing the VOx surface densities, and finally to crystalline V2O5 clusters at surface densities above one-monolayer capacity. Within one-monolayer capacity, higher VOx surface densities and more reducible supports led to higher reducibility and reactivity of the VOx domains. The support surfaces covered with polyvanadates and V2O5 clusters and the supports with acidity favored the formation of DFF. The correlation between the reducibility and reactivity, together with the kinetic studies, suggests that the HMF oxidation to DFF proceeds via the redox mechanism involving the V5+/V4+ redox cycles and the reoxidation of V4+ to V5+ by O2 as the rate-determining step. These results may provide guidance for the design of more efficient catalysts for the HMF oxidation to synthesize DFF.
*Pure Appl. Chem. 84, 411–860 (2012). A collection of invited papers for the IUPAC project 2008-016-1-300 “Chlorine-free Synthesis for Green Chemistry”.