Mixed-metal oxides of the Ni-Ce-O type are excellent catalysts for the production of hydrogen through ethanol steam reforming. They have lower cost and a higher catalytic activity than Rh/CeO2. The steam reforming of ethanol on different types of Ni-Ce-O catalysts was studied using in situ X-ray diffraction (XRD), operando diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and mass spectroscopy (MS) with a focus on the structural characterization of the catalysts, chemical identification of the reaction pathway and understanding of the interaction between the Ni and CeO2 components.  Under reaction conditions, the active Ni-Ce-O catalysts contain small particles of nickel dispersed on partially reduced ceria. Ethoxy, acetate, carbonate and hydroxyl species are identified by DRIFTS as surface intermediates that appear during the reaction process.  The oxidation of ethoxy to acetate and the decomposition of acetate are two key steps in the steam reforming process.  The CeO2 component facilitates the oxidation of ethoxy to acetate below 350 �C.  Above 350 �C, the Ni metal catalyzes dissociation of C-C bond in acetate to form carbonate and methyl, something that the CeO2 is not able to do.  The Ce(III) sites produced by the reduction of ceria in ethanol help to dissociate water forming the surface hydroxyl groups, which react with the methyl groups to produce CO2 and inhibited the methyl groups progress to CH4.  Post-reaction transmission electron microscopy (TEM) images of the Ni-Ce-O catalyst reveal two types of carbon configurations: encapsulating carbon and filamentous carbon.  A water-rich atmosphere favors formation of carbon filaments, which do not deactivate the catalyst. Our studies indicate that the metal and oxide phases in a Ni-Ce-O catalyst have specific roles in ethanol steam reforming and both phases should be considered when optimizing catalytic performance.

Steam reforming of ethanol on Ni-Ce-O catalysts: Reaction pathway and interaction between Ni and the CeO<sub>2</sub> components

248th National Meeting (2014)

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Steam reforming of ethanol on Ni-Ce-O catalysts: Reaction pathway and interaction between Ni and the CeO2 components

Steam reforming of ethanol on Ni-Ce-O catalysts: Reaction pathway and interaction between Ni and the CeO₂ components