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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 32, Number 5
BKCSDE 32(5)
May 20, 2011 

Hydrogenation of Phenylacetylene to Styrene on Pre-CxHy- and C-Covered Cu(111) Single Crystal Catalysts
Youngku Sohn*, Wei Wei, John M. White,b
Hydrogenation, Temperature-programmed desorption, Phenylacetylene, Styrene
Thermal hydrogenation of phenylacetylene (PA, C8H6) to styrene (C8H8) on pre-CxHy- and C-covered Cu(111) single crystal substrates has been studied using temperature-programmed desorption (TPD) mass spectrometry. Chemisorbed PA with an acetylene group has been proved to be associated with hydrogen of pre-adsorbed CxHy to form styrene (104 amu) on Cu surface. For the parent (PA) mass (102 amu) TPD profile, the TPD peaks at 360 K and 410 K are assigned to chemisorbed vertically aligned PA and flat-lying cross-bridged PA, respectively (J. Phys. Chem. C 2007, 111, 5101). The relative I360K/I410K TPD ratio dramatically increases with increasing pre-adsorbed CxHy before dosing PA, while the ratio does not increase for pre-C-covered surface. For PA on pre-CxHy-covered Cu(111) surface, styrene desorption is enhanced relative to the parent PA desorption, while styrene formation is dramatically quenched on pre-C-covered (lack of adsorbed hydrogen nearby) surface. It appears that only cross-bridged PA associates with adsorbed hydrogen to form styrene that promptly desorbs at 410 K, while vertically aligned PA is less likely to participate in forming styrene.
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