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Available online xxxKeywords: Hydrogen Carbon dioxide Methanation Ruthenium on alumina Activation of the catalyst Stability a b s t r a c tThe methanation of carbon dioxide has been studied over 3% Ru/Al 2 O 3 and 20% Ni/Al 2 O 3 commercial catalysts. Experiments have been performed in diluted conditions in a flow catalytic reactor with a continuous IR detection of products. The data, reported here, confirm that 3% Ru/Al 2 O 3 is an excellent catalyst for CO 2 methanation (96% methane yield with no CO coproduction at 573 K at 15,000 h À1 GHSV in excess hydrogen). The performance is better than that of Ni/Al 2 O 3 catalyst. The reaction orders over both catalysts with respect to both hydrogen and CO 2 were determined over conditioned catalysts. A conditioning of the Ru/Al 2 O 3 catalyst by reactant gas stream was found to be needed and more effective than conditioning in hydrogen, possibly because water vapour formed during methanation reaction will react to remove chlorine impurities from catalyst surface Conditioned Ru/Al 2 O 3 catalyst was found to retain stable high activity after different shutdown and start-up procedures, thus being possibly applicable in intermittent conditions.

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Atomically dispersed gold supported on nanoscale ZnZrOx composite oxides was prepared and investigated in this work as a catalyst for the low-temperature ethanol dehydrogenation reactions. The composite ZnZrOx support disperses gold atomically and stabilizes it against growth much better than either of the neat oxides. Sequential ethanol conversion reactions to acetaldehyde and acetone take place on the Au/ZnZrOx catalysts within well-separated temperature windows over the range of tested temperatures (30-400 °C). ZnO modulates the acidity of the ZrO2 surface, and the extent of this was followed by isopropanol temperature-programmed desorption with online mass spectrometry (IPA-TPD/MS; and by diffuse reflectance UV-Vis-IR). Catalyst activity and selectivity were tested by temperature-programmed surface reaction (TPSR) and under steady-state reaction conditions. The work has demonstrated that ZnZrOx with optimized ZnO distribution preserves the active Au-Ox surface species under reaction conditions and suppresses undesired dehydration reactions. Addition of gold on the bare zirconia support passivates the acid sites catalyzing ethanol dehydration and introduces desired dehydrogenation sites at low temperatures (200 °C)