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This study investigates thermal aging induced effects on the surface properties of model and commercial automotive catalysts for Natural Gas Vehicles, by means of X-ray photoelectron spectroscopy and infrared spectroscopy of chemisorbed CO as a probe molecule for noble metals. Post-combustion catalysts for this application are essentially composed of palladium containing low amounts of rhodium and additives to improve the oxygen storage properties. The aging procedure involved exposing the catalysts to an oxidizing atmosphere containing air and 10 vol.% H 2 O at 980• C for 4 h in order to simulate surface changes which may occur under usual three-way operating conditions. It was found that sintering processes led to a significant loss of Pd concentration on model and commercial catalysts. Regarding Rh, diffusion processes into alumina also take place, which are partially inhibited on model catalysts when Rh interacts with Pd. Greater stabilization of Rh species is suggested on commercial catalysts in the presence of oxygen storage materials.

Catalysts H 2000Oxide Foams for the Synthesis of High-Surface-Area Vanadium Nitride Catalysts.-Nanocrystalline (6-8 nm) VN with a high specific surface area (80-190 m 2 /g) is synthesized by temperature-programmed reduction using a high-volume V2O5 foam as precursor. The foam-derived VN exhibits significantly improved catalytic performance in the non-oxidative dehydrogenation of propane compared with VN synthesized by the conventional nitridation route. -(KRAWIEC, P.; DE COLA, P. L.; GLAESER, R.; WEITKAMP, J.; WEIDENTHALER, C.; KASKEL*, S.; Adv. Mater. (Weinheim, Ger.) 18 (2006) 4, 505-508; Inst. Anorg.