Correlations between oxygen activation and methane oxidation over Pd/γ-Al2O3 catalysts prepared by nitrite method

In this work the oxygen activation properties and methane oxidation activities of Pd/Al2O3 catalysts prepared by the nitrite-complex method are investigated. The effects of altering the preparation procedure and in-situ pre-treatments are considered. Based on the results, correlations between isotopic exchange and methane oxidation activities are drawn. Even if Pd/Al2O3 catalysts have typically a low activity in oxygen activation, it was found, that reductive in-situ pre-treatment of the catalyst significantly enhances the activity of oxygen activation studied by isotopic exchange and equilibration experiments. In addition, both equilibration and exchange take place on the pre-oxidized catalyst, whereas mainly equilibration occurs on the pre-reduced catalyst. The catalyst sample that was reduced prior to washing in the preparation stage showed to be most active in both cases, in isotopic oxygen exchange and in methane oxidation. The explanation to the enhanced activity is suggested to be originated from more easy reducibility of palladium.

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► Pd prepared by nitrite-method is very active in methane oxidation and O2 activation.
► Reduction stage in preparation and reduction prior experiment enhance Pd activity.
► Easy Pd reducibility and Pd–alumina interactions have connection to good activity.
► Carbonates formed due to CO2 production in CH4 oxidation may enhance O2 activation.