The role of rare earth oxides as promoters and stabilizers in combustion catalysts

Rare earth oxides (REO) have been increasingly investigated in the last years as potential co-catalysts in several commercial applications. The major role would be that of improved activity and selectivity, and increase in thermal stability of catalytic materials. As a contribution to this area, we have been investigating in the last few years a number of issues concerning the preparation and characterization of ceria, praseodymia and terbia-containing materials with regard to their application as redox and combustion catalysts. Some of these issues will be reviewed here, with special focus on the catalytic properties and structural characterization of catalytic materials obtained by using REO as promoters. Specifically, in this paper the role of REO (CeO2, Tb4O7 and Pr6O11) as stabilizers and promoters in Pd-based catalysts is investigated. Particular attention is paid to their effects on the catalytic combustion of methane and on the dynamics of Pd-PdO transformation. Characterization of supports by in situ XRD, surface area measurements and TPR is also presented.