Berlin 2001 – wissenschaftliches Programm
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MO: Molekülphysik
MO 3: Reactive and Energy Transfer Processes
MO 3.6: Vortrag
Montag, 2. April 2001, 17:00–17:15, H1058
Reaction mechanism for the oxidation of free silver dimers — •Jan Hagen1, Liana D. Socaciu1, Ueli Heiz2, Thorsten M. Bernhardt1, Thomas Leisner1, and Ludger Wöste1 — 1Freie Universität Berlin, Institut für Experimentalphysik, Arnimallee 14, D-14195 Berlin, Germany — 2Ecole Polytechnique Federale de Lausanne, Institut de Physique Experimentale, CH-1015 Lausanne, Switzerland
Small dispersed silver particles exhibit unique properties in the heterogeneous catalysis such as the epoxidation of ethylene to ethylene oxide and the partial oxidation of methanol to formaldehyde. Since it was shown that silver has the ability to activate O2 in these reactions it is important to investigate the chemical properties of silver. We study the kinetics of the interaction of Ag2+ with O2 in the gas phase under multi-collision conditions at various temperatures. A new experimental scheme is employed, which consists of an octopole ion trap of variable temperature inserted into a tandem quadrupole mass spectrometer. From the time evolution of the reactant and product molecule concentrations at different temperatures the corresponding reaction mechanism is extracted. Surprisingly, the product Ag2O+ is detected, which is formed after molecular adsorption and dissociation of O2. We can clearly identify Ag2O2+ as an intermediate in this reaction. In addition, absolute rate coefficients and activation energies for the molecular adsorption of O2 onto Ag2+ are presented.