Direct production of 2,5-diformylfuran from fructose catalysed by Mo-based composite oxides in static air

A series of MxMoyOd composite oxides (M = Ca, Mn, Fe, Co, Ni, Cu, Zn, Y, Bi, Zr, La or Ce) was synthesized and used for the one-pot direct conversion of fructose to 2,5-diformylfuran (DFF) using atmospheric air as the oxidant. Among these materials, ZrxMoyO delta exhibited the best catalytic performance. Hence, the effects of the Zr/Mo molar ratio and calcination temperature on catalytic performance were investigated in detail and the reaction conditions were also optimized. The highest performing catalyst, Zr1Mo2O delta, produced a DFF yield of 61 % along with the complete conversion of fructose under the optimized reaction conditions. More importantly, this material also exhibited good recycling stability and could be reused five times without a noticeable loss of activity. These ZrxMoyO delta catalysts were characterized using multiple techniques. Zirconium oxide was found to interact strongly with molybdenum oxide species via the formation of Zr(MoO4)(2), thus producing a large number of surface chemisorbed oxygen species. The close linear correlation between DFF yield and surface chemisorbed oxygen confirmed that these oxygen species were the primary active sites for the oxidation reaction.