Thermal Behaviour of Metallic TWC. Evaluation of the Structural and Performance Properties

The aim of this work was to combine different surface analytical techniques to study the effect of thermal/hydrothermal aging on the surface micro-structure and catalytic efficiency of the metallic Kemira three-way catalysts, which contained different stabilizers (Si, Zr, La, Ba and their mixtures) as additives. One commercial ceramic and one commercial metallic catalyst were also tested and analyzed as a comparison.

In summary, it can be stated that the performance of catalysts cannot be predicted solely on the basis of some separate properties i.e. BET area, noble metal dispersion or crystal sizes of the washcoat components. The results of different analyses (XRD, XPS, SEM/STEM and chemisorption) must be combined in order to fully understand the catalyst characteristics. However, the best performance was obtained with the samples with small crystals of both Pt and CeO₂ dispersed in an amorphous alumina. At high aging temperatures, the crystal growth of all components takes place. The different stabilizers have different effects on each catalyst component. Their preferential sequence is presented in the following examination.