Insight into Fructose Dehydration over Lewis Acid α‐Cu2P2O7 Catalyst

Abstract

AbstractKey information on direct conversion of fructose into 5‐hydroxymethylfurfural (5‐HMF) over Lewis acid sites was investigated by combining experimental and computational studies. A series of alpha‐copper pyrophosphate (α‐Cu2P2O7) was synthesized and used as a heterogeneous catalyst model for bifunctional acid‐catalyzed fructose dehydration under hot compressed water at mild temperature. Structural and phase transformations of the catalyst samples were systematically characterized by in situ X‐ray absorption spectroscopy (in situ XAS), X‐ray powder diffraction (XRD) and Transmission electron microscopy (TEM). The type of acidic site was verified by in situ pyridine‐adsorbed Fourier‐transform infrared spectroscopy (in situ Py‐FTIR). Results revealed that calcination temperature greatly impacted microstructure, acid strength, and activity of the α‐Cu2P2O7 catalysts. Lewis acid sites showed the main activity on α‐Cu2P2O7 catalyst surfaces. Catalytic performance was strongly dependent on reaction temperature and reaction time. Under optimal reaction condition, the calcined sample at 900 °C exhibited the best catalytic performance with 5‐HMF production yield of 42.0%. Results from density functional theory (DFT) revealed that fructose dehydration over α‐Cu2P2O7 catalyst was enhanced by increasing reaction thermodynamics via Lewis acid sites.