Dresden 2006 – scientific programme

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O: Oberflächenphysik

O 28: Surface reactions II

O 28.10: Talk

Tuesday, March 28, 2006, 18:00–18:15, WIL C207

EPOXIDATION OF ETHYLENE ON SILVER STUDIED BY HIGH-PRESSURE STM — •R. Reichelt, M. Rößler, S. Günther, and J. Wintterlin — Ludwig-Maximilians-Universität, Department Chemie, 81377 München, Germany

Using an improved high pressure scanning tunneling microscope (STM) we have investigated the epoxidation of ethylene on silver surfaces. The setup consists of a high-pressure cell (up to 1 bar) housing the STM that is attached to an ultra-high vacuum chamber and to a gas analysis system containing a mass spectrometer. In the STM cell catalytic reactions can be performed under pressure and temperature conditions close to those of industrial catalytic processes, both in batch and flow mode. In the UHV chamber single crystal surfaces are prepared under clean surface-science conditions, and standard surface science techniques are used for post-reaction analysis of the sample surface. It has been achieved to detect a reaction to give ethylene oxide at pressures of approximately 1 mbar and at temperatures around 500 K. Atomic resolution was obtained on an Ag(111) surface under epoxidation conditions. Several different surface structures were observed, suggesting that more than one species of oxygen is involved in this reaction.