The influence of ceria and other rare earth promoters on palladium-based methane combustion catalysts

In this work we investigate the effect of ceria and other rare earths (La, Pr, Tb) on Pd–PdO transformation, which is strongly related to the catalytic activity of Pd-based catalysts for the combustion of methane at high temperature. Also the behavior of Pd on ZrO2 and on yttria-stabilized zirconia is considered for comparison. The catalysts are characterized by XRD and BET surface area measurements. Pd–PdO transformation is studied by means of temperature programmed oxidation measurements and thermogravimetric analysis. Temperature programmed combustion experiments have been carried out in order to compare catalytic activity of different catalysts. The results show that rare earth oxides promote the onset of Pd re-oxidation upon cooling, that for ceria doped sample is reflected in an improvement in the catalytic activity.

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► A decoupling of onset and rate of Pd oxidation is reported.
► Among the investigated rare earth dopants, ceria is the only one that promotes both onset and rate of Pd oxidation.
► The contemporary presence of both anticipated onset and higher rate of Pd oxidation is necessary for an improvement of methane combustion activity upon cooling.