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A single-bed and dual-bed catalyst system was studied to maximize H2 production from the combination of partial oxidation of CH4 and water gas shift reaction. In addition, the different types of catalysts, including Ni, Cu, Ni-Re, and Cu-Re supported on gadolinium-doped ceria (GDC) were investigated under different operating conditions of temperature (400–650 °C). Over Ni-based catalysts, methane can easily dissociate on a Ni surface to give hydrogen and carbon species. Then, carbon species react with lattice oxygen of ceria-based material to form CO. The addition of Re to Ni/GDC enhances CH4 dissociation on the Ni surface and increases oxygen storage capacity in the catalyst, thus promoting carbon elimination. In addition, the results showed that a dual-bed catalyst system exhibited catalytic activity better than a single-bed catalyst system. The dual-bed catalyst system, by the combination of 1%Re4%Ni/GDC as a partial oxidation catalyst and 1%Re4%Cu/GDC as a water gas shift catalyst, provided the highest CH4 conversion and H2 yield. An addition of Re onto Ni/GDC and Cu/GDC caused an increase in catalytic performance because Re addition could improve the catalyst reducibility and increase metal surface area, as more of their surface active sites are exposed to reactants. [ABSTRACT FROM AUTHOR]

Key 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. [ABSTRACT FROM AUTHOR]