Propylene Oxidation Mechanisms and Intermediates Using In-Situ Soft X-Ray Fluorescence Methods on the Pt(111) Surface

Published

January 1, 2000

Author(s)

A M. Gabelnick, A T. Capitano, S M. Kane, J L. Gland, Daniel A. Fischer

Abstract

The oxidation of propylene on the Pt(111) surface has been characterized in oxygen pressures up to 0.02 torr using fluorescence yield near -edge spectroscopy (FYNES) and temperature programmed fluorescence yield near-edge spectroscopy (TP-FYNES) above the carbon K edge. During oxidation of adsorbed propylene, a stable intermediate was observed and characterized using both of these soft X-ray methods. Total carbon concentration measured in the carbon continuum as a function of temperature clearly indicates an intermediate is formed in the 300 K temperature range. By comparing the intensity of the C-H ς* resonance at the magic angle with the intensity in the carbon continuum, the stoichiometry of this intermediate can be determined. Based on calibration of this intensity ratio with molecular propylene (C₃H₆) and propylidyne (C₃H₅), the intermediate has a stoichiometry of C₃H₅ in agreement with our previous TPRS studies. A set of normal and glancing FYNES spectra above the carbon K edge of the adsorbed intermediate was used to characterize the bonding and structure of the intermediate. Spectra of known coverages of adsorbed propylene and propylidyne were obtained during the same sequence to serve as standards. The spectra of di-s propylene, propylidyne, and the intermediate were fit as a group with consistent energies and widths of all primary features. Based on this procedure, the intermediate is 1,1,2-tri sigma-1-methylvinyl. The stoichiomometry and stability range of the 1-methylvinyl intermediate formed in oxygen pressures up to 0.02 torr is identical to the stoichiometry and stability of the same intermediate formed during oxidation of preadsorbed propylene by excess coadsorbed atomic oxygen.

Citation

Journal of the American Chemical Society

Volume

122

Issue

No. 1

Pub Type

Journals

Keywords

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

Citation

Gabelnick, A. , Capitano, A. , Kane, S. , Gland, J. and Fischer, D. (2000), Propylene Oxidation Mechanisms and Intermediates Using In-Situ Soft X-Ray Fluorescence Methods on the Pt(111) Surface, Journal of the American Chemical Society (Accessed December 2, 2024)