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O: Oberflächenphysik

O 15: Postersitzung (Adsorption an Oberfl
ächen, Epitaxie und Wachstum, Organische Dünnschichten, Oxide und Isolatoren, Rastersondentechniken, Zeitaufgelöste Spektroskopie, Methoden)

O 15.53: Poster

Freitag, 4. März 2005, 17:00–20:00, Poster TU D

Effect of support and additives on properties of molybdena-based catalysts. — •Renata Tokarz-Sobieraj and Malgorzata Witko — Institute of Catalysis and Surface Chemistry, PAS, ul. Niezapominajek 8, 30 239 Kraków, Poland

Molybdenum oxide-based catalysts are active and selective in many reactions of very different types e.g. selective oxidation, oxidative dehydrogenation. The catalytic properties of such catalysts strongly depend on acid-base properties of catalysts surfaces, which determine the strength of surface-substrate interactions and facilitate the desorption of products from the surface. Experiment shows that acid-base properties of an oxide catalyst can be controlled by the introduction of additives or usage of different supports. In the present work, the effect of additives (K, Ni, Cr, Pt) and effect of the support (SiO2, Al2O3, TiO2, MgO) on the electronic and geometric structures is discussed by means of quantum chemical calculations based on the density functional theory (DFT), using cluster model. Theoretical data shows that substitution of molybdenum atom(s) in the cluster by additive atoms or atoms from different supports changes the local electronic state and, what follows, the local reactivity of different surface oxygen sites (Mo=O and Mo-O-X) that are present at the catalyst surface. The results of calculations are compared with the experimental findings.