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Reactions of Chlorobenzene on the Pt (111) Surface: A Temperature Programmed Reaction and Fluorescence Yield Near Edge Spectroscopy Study

Published

Author(s)

B M. Haines, G E. Mitchell, Daniel A. Fischer, J L. Gland

Abstract

The surface reactions of chlorobenzene on Pt(111) have been studied using temperature programmed reaction spectroscopy (TPRS) and fluorescence yield near edge spectroscopy (FYNES). Thermal hydrodechlorination, dehydrogenation and rehydrogenation result in the formation of HCl, benzene, and H2 when chlorobenzene is heated on platinum. The chlorobenzene monolayer adsorbs on the Pt(111) surface with the plane of the ring at a 45 angle from the surface as indicated by FYNES. Multilayer desorption is observed at 163 K, and the monolayer partially desorbs at 196 K. The remaining chlorobenzene undergoes dechlorination via two reaction channels at 270 K and at 420 K as shown by TPRS. Quantitative comparison of the TPRS integrated peak areas for these two channels yields a 3 ( 0.2):2 ( 0.2) (270 K: 420 K) ratio indicating that 3/5ths of chlorobenzene is dechlorinated at 270 K. The stoichiometric information from the temperature programmed-FYNES is consistent with the presence of a stable cyclohexadiene intermediate formed above 250 K, coadsorbed in a 3:2 ratio with molecular chlorobenzene. The remaining molecular chlorobenzene is dechlorinated in the 420 K range to form additional adsorbed cyclohexadiene. Most of this cyclohexadiene undergoes stepwise dehydrogenation with the loss of the first hydrogen at 470 K. The remaining three hydrogens are removed from 500 K to 800 K. A small fraction of the cyclohexadiene is rehydrogenated to form benzene at approximately 470 K.
Citation
Journal of Physical Chemistry B

Keywords

chlorobenzene, hydrodechlorination, NEXAFS

Citation

Haines, B. , Mitchell, G. , Fischer, D. and Gland, J. (2021), Reactions of Chlorobenzene on the Pt (111) Surface: A Temperature Programmed Reaction and Fluorescence Yield Near Edge Spectroscopy Study, Journal of Physical Chemistry B (Accessed May 18, 2024)

Issues

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Created October 12, 2021