Site-blocking effects of preadsorbed H on Pt(1 1 1) probed by 1,3-butadiene adsorption and reaction

Haibo Zhao, Lindsey A. Welch, Bruce E. Koel

Research output: Contribution to journalArticle

7 Scopus citations

Abstract

The influence of hydrogen coadsorption on hydrocarbon chemistry on transition metal surfaces is a key aspect to an improved understanding of catalytic selective hydrogenation. We have investigated the effects of H preadsorption on adsorption and reaction of 1,3-butadiene (H2C{double bond, long}CHCH{double bond, long}CH2, C4H6) on Pt(1 1 1) surfaces by using temperature-programmed desorption (TPD) and Auger electron spectroscopy (AES). Preadsorbed hydrogen adatoms decrease the amount of 1,3-butadiene chemisorbed on the surface and chemisorption is completely blocked by the hydrogen monolayer (saturation) coverage (θH = 0.92 ML). No hydrogenation products of reactions between coadsorbed H adatoms and 1,3-butadiene were observed to desorb in TPD experiments over the range of θH investigated (θH = 0.6-0.9 ML). This is in strong contrast to the copious evolution of ethane (CH3CH3, C2H6) from coadsorbed hydrogen and ethylene (CH2{double bond, long}CH2, C2H4) on Pt(1 1 1). Hydrogen adatoms effectively (in a 1:1 stoichiometry) remove sites from interaction with chemisorbed 1,3-butadiene, but do not affect adjacent sites. The adsorption energy of coadsorbed 1,3-butadiene is not affected by the presence of hydrogen on Pt(1 1 1). The chemisorbed 1,3-butadiene on hydrogen preadsorbed Pt(1 1 1) completely dehydrogenates to H2 and surface carbon upon heating without any molecular desorption detected, which is identical to that observed on clean Pt(1 1 1). In addition to revealing aspects of site blocking that should have broad implications for hydrogen coadsorption with hydrocarbon molecules on transition metal surfaces in general, these results also provide additional basic information on the surface science of selective catalytic hydrogenation of butadiene in butadiene-butene mixtures.

Original languageEnglish (US)
Pages (from-to)3355-3360
Number of pages6
JournalSurface Science
Volume603
Issue number23
DOIs
StatePublished - Dec 1 2009
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films
  • Materials Chemistry

Keywords

  • 1,3-Butadiene
  • CH
  • Coadsorption
  • H
  • Hydrogen
  • Hydrogenation
  • Pt(1 1 1)
  • TPD

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