Ethylene Oxidation Mechanisms and Intermediates: In Situ Soft X-Ray Studies of Ethylene Oxidation on the Pt(111) Surface

Published

March 10, 2005

Author(s)

D J. Burnett, A M. Gabelnick, J L. Gland, Daniel A. Fischer

Abstract

In situ studies of ethylene oxidation on Pt(111) have been performed using a powerful combination of fluorescence yield soft x-ray methods for temperatures up to 600 K and oxygen pressures up to 1.3 Pa. Absolute carbon coverages have been determined both in steady state and dynamic catalytic conditions on the Pt(111) surface. Fluorescence yield near-edge spectroscopy (FYNES) and temperature-programmed fluorescence yield near-edge spectroscopy (TP-FYNES) experiments above the carbon K edge were used to identify the structure and bonding of the dominant surface species during oxidation. TP-FYNES experiments of preadsorbed ethylene monolayers in oxygen pressures up to 1.3 Pa indicate a stable intermediate is formed over the 300 K to 340 K temperature range. By comparing the C-H s* resonance at the magic angle with the intensity in the carbon continuum, the stoichiometry of this intermediate can be determined explicitly. Based on calibration with known C:H stoichiometries, the intermediate has a C2H3 stoichiometry for oxygen pressures up to 1.3 Pa, indicating oxydehydrogenation occurs before skeletal oxidation. FYNES spectra at normal and glancing intermediates were performed to characterize the structure and bonding of this intermediate, using FYNES spectra of ethylene, ethylidyne, and acetylene as reference standards. This procedure indicates the oxidation intermediate is tri-s vinyl. Thus, oxidation of ethylene proceeds through a vinyl intermediate with oxydehydrogenation preceding skeletal oxidation.

Citation

Journal of Physical Chemistry B

Volume

109

Pub Type

Journals

Keywords

ethylene, intermediates, oxidation, platinum, soft x-ray, surface science

Citation

Burnett, D. , Gabelnick, A. , Gland, J. and Fischer, D. (2005), Ethylene Oxidation Mechanisms and Intermediates: In Situ Soft X-Ray Studies of Ethylene Oxidation on the Pt(111) Surface, Journal of Physical Chemistry B (Accessed December 22, 2024)