REACTIVITY AND MECHANISM OF CATALYTIC METHANE CONVERSION OVER CERIA-ZIRCONIA SUPPORTED METAL/METAL OXIDE CATALYSTS
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Methane, the major component of natural gas, is vastly available on Earth, but is not used effectively. Methane conversion using heterogeneous catalysts, such as CZ supported metal/metal oxide materials, provides a promising solution to the challenge. The synthesis-structure relationship for such catalyst materials was revealed by thorough characterization of NiO/CZ catalysts synthesized differently. The structural properties are further related to methane dry reforming performances, suggesting that the Ni speciation and the oxygen storage capacity are the key factors shaping the deactivation behavior. Understanding methane activation over NiO/CZ catalysts provides important insights for rational catalyst design and was carried out using in-situ FTIR spectroscopy. Using a novel data analysis algorithm based on non-linear regression fitting, the evolution of different surface species is deconvoluted to elucidate the surface reaction pathways during methane activation, showing that different reactivity can be achieved by fine tuning the nature of active sites and reaction conditions. The selective oxidation of methane to methanol was realized over MOx/CZ (M=Ni, Cu, Fe) catalysts. The strong LAS concentration controls the formation of methoxy intermediates during methane activation, which in turn governs the selectivity towards methanol. Taken together, these examples reveal how systematic investigations of catalysts provide design principles for catalytic methane conversions.