Berlin 2008 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 55: Poster Session III - MA 141/144 (Methods: Atomic and Electronic Structure; Particles and Clusters; Heterogeneous Catalysis; Semiconductor Substrates: Epitaxy and Growth+Adsorption+Clean Surfaces+Solid-Liquid Interfaces; Oxides and Insulators: Solid-Liquid Interfaces+Epitaxy and Growth; Phase Transitions; Metal Substrates: Adsorption of Inorganic Molecules+Epitaxy and Growth; Surface Chemical Reactions; Bimetallic Nanosystems: Tuning Physical and Chemical Properties; Oxides and insulators: Adsorption; Organic, polymeric, biomolecular films; etc.)
O 55.21: Poster
Mittwoch, 27. Februar 2008, 18:30–19:30, Poster F
The chemical state of iron during N2O decomposition over iron modified zeolites ZSM-5: A high-pressure XPS study — •Karifala Dumbuya1, Saiprasath Gopalakrishnan2, Wilhelm Schwieger2, J. Michael Gottfried1, and Hans-Peter Steinrück1 — 1Universität Erlangen-Nürnberg, Lehrstuhl für Physikalische Chemie II — 2Universität Erlangen-Nürnberg, Lehrstuhl für Chemi-sche Reaktionstechnik
Iron containing ZSM-5 zeolites are employed as catalysts for the abatement of N2O in waste gases and in partial oxidation reactions with N2O as the oxidant. The chemical state of the active Fe centers during reaction is unknown; however, it has been speculated that an α-Fe(II) species is the active site.1 NaOH-treatment increases the activity, which has been attributed to the alteration of the Fe centers.2 We have studied commercial ZSM-5 (as-supplied and NaOH-treated) using XPS and in-situ XPS during N2O exposure (pressure ≤ 1 mbar). No Fe was found in the surface region of the commercial ZSM-5 before or after ion-exchange with NaOH, contrary to ICP-AES results. As expected, significant amounts of Fe (mainly in the +2 and +3 oxidation states) were detectable with XPS, following Fe doping of both catalysts. The Fe content in the surface region of the NaOH-modified ZSM-5 did not change with temperature (300-650 K), while the as-supplied sample showed Fe segregation in this temperature range. Details about the electronic state of Fe in the Fe doped, NaOH-modified catalyst in the presence of N2O (5*10−8 - 1 mbar) will be discussed. [1] Dubkov et al., J. Catal. 207 (2002) 341. [2] Groen et al., J. Catal. 243 (2006) 212.