Redox behaviour and catalytic properties of Ce0.5Zr0.5O2-supported palladium catalysts

Ce0.5Zr0.5O2-supported palladium catalysts were prepared and used for CO and methane oxidation. The redox behaviour of these catalysts was investigated by using H-2-TPR and CO-TPR. The shape and temperature of TPR peaks depend on the nature of reducing agent. Two peaks (alpha(1) and gamma) were observed when H-2 was used as reducing agent for the fresh catalyst, while three peaks (alpha', beta' and gamma') were observed when CO was used as a reducing agent. The addition of a noble metal effectively promotes the reduction of Ce0.5Zr0.5O2 support, which is attributed to hydrogen spillover. After re-oxidation treatments, the PdO reduction process splits into two peaks (alpha(1) and alpha(2)). On the basis of the catalytic activity and CO-TPR results, the activity of CO oxidation is related to the finely dispersed PdO, while the activity of methane oxidation is related to the large PdO particles. (C) 1999 Elsevier Science B.V. All rights reserved.