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Titolo:
Molecular mechanisms of propyne oxidation on the Pt(111) surface: In situ soft X-ray studies in pressures of oxygen
Autore:
Gabelnick, AM; Burnett, DJ; Gland, JL; Fischer, DA;
Indirizzi:
Univ Michigan, Dept Chem, Ann Arbor, MI 48109 USA Univ Michigan Ann ArborMI USA 48109 , Dept Chem, Ann Arbor, MI 48109 USA Univ Michigan, Dept Chem Engn, Ann Arbor, MI 48109 USA Univ Michigan Ann Arbor MI USA 48109 t Chem Engn, Ann Arbor, MI 48109 USA Natl Inst Stand & Technol, Gaithersburg, MD 20899 USA Natl Inst Stand & Technol Gaithersburg MD USA 20899 ersburg, MD 20899 USA
Titolo Testata:
JOURNAL OF PHYSICAL CHEMISTRY B
fascicolo: 32, volume: 105, anno: 2001,
pagine: 7748 - 7754
SICI:
1520-6106(20010816)105:32<7748:MMOPOO>2.0.ZU;2-I
Fonte:
ISI
Lingua:
ENG
Soggetto:
TEMPERATURE-PROGRAMMED DESORPTION; ABSORPTION FINE-STRUCTURE; CATALYTIC-OXIDATION; HYDROCARBONS; COMBUSTION; PALLADIUM; ACETYLENE; PLATINUM; ETHYLENE; ALKENES;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
24
Recensione:
Indirizzi per estratti:
Indirizzo: Gland, JL Univ Michigan, Dept Chem, Ann Arbor, MI 48109 USA Univ MichiganAnn Arbor MI USA 48109 m, Ann Arbor, MI 48109 USA
Citazione:
A.M. Gabelnick et al., "Molecular mechanisms of propyne oxidation on the Pt(111) surface: In situ soft X-ray studies in pressures of oxygen", J PHYS CH B, 105(32), 2001, pp. 7748-7754

Abstract

Oxidation of preadsorbed propyne has been characterized on the Pt(111) surface in oxygen at pressures up to 0.009 Torr using fluorescence yield ultrasoft X-ray adsorption methods above the carbon K edge. A combination of temperature-programmed reaction spectroscopy (TPRS) and temperature-programmedfluorescence yield near edge spectroscopy (TP-FYNES) experiments indicating that similar oxidation pathways occur both for coadsorbed oxygen and pressures of oxygen. Soft X-ray spectroscopy indicates that propyne's pi systemadsorbs nearly parallel to this surface with a saturation coverage of 1.45x 10(15) C atoms/cm(2). Oxidation of small propyne coverages with coadsorbed oxygen results in simultaneous CO2 and H2O peaks at 320 and 420 K, as seen in TPRS. Oxidation of higher propyne coverages with coadsorbed oxygen results in a broad oxidation peak over the 350-420 K temperature range. Oxidation of a saturated propyne monolayer in oxygen pressures (TP-FYNES) results in a rapid decrease in carbon coverage over the same temperature range, suggesting similar mechanisms. Isothermal oxidation in oxygen atmospheres indicates that propyne oxidation is first-order in propyne coverage and has an activation energy of 17 kcal/mol for high coverages. Deviations from first-order behavior suggest that a second process may become important at lower coverages in oxygen atmospheres. Regardless of coverage and initial conditions, both TPRS and TP-FYNES indicate oxydehydrogenation and skeletal oxidation occur simultaneously and the oxidation proceeds with a fixed C3H4 stoichiometry. Taken together, these results give a molecular picture of propyne oxidation on the Pt(111) surface.

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Documento generato il 06/04/20 alle ore 02:03:13