Methane combustion over Pd/γ-Al2O3 and Pd-VOx/γ-Al2O3 catalysts Original Research Article

In this paper, we have investigated the methane combustion reaction over Pd-VOx/γ-Al2O3 catalysts of varying vanadium loadings, and have compared the results with those obtained over Pd/γ-Al2O3 catalysts. Previously, calcined samples were tested under slightly reducing conditions, the binary samples being much less active than the monometallic one. The decrease in activity correlates well with the increase in vanadium loading. For previously reduced samples tested under similar conditions, the initial activity was lower for Pd/γ-Al2O3 and higher for the binary catalysts. The samples were characterized by CH4-temperature programmed reduction (TPR), hydrogen chemisorption and transmission electron microscopy (TEM). On the basis of the available information, it is concluded that reconstruction of palladium, an essential requirement to form an oxidized phase, which is active for methane combustion, is inhibited by the presence of a VOx monolayer.