Adsorption and desorption behavior of n-butane and isobutane on Pt(111) and Sn/Pt(111) surface alloys

Journal Article · Sat Jan 01 00:00:00 EST 1994 · Langmuir; (United States)

DOI:https://doi.org/10.1021/la00013a025· OSTI ID:5195321

Xu, C; Koel, B E ^[1]; Paffett, M T ^[2]

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1. Univ. of Southern California, Los Angeles, CA (United States)
2. Los Alamos National Lab., NM (United States)

The adsorption/desorption behavior of n-butane and isobutane on Pt(111) and the p(2[times]2) Sn/Pr(111) and ([radical]3[times] [radical]3)R30[degrees] Sn/Pt(111) surface alloys has been examine using a combination of adsorption kinetics measurements utilizing a collimated molecular beam and temperature programmed desorption (TPD) mass spectroscopy. Initial sticking probabilities for both molecules on Pt(111) and the surface alloys at temperatures below the monolayer desorption threshold are essentially unity (S[sub 0] [>=] 0.95). The monolayer saturation coverages of n-butane and isobutane were also independent of the amount of Sn in the surface layer. The desorption activation energies measured by TPD for the monolayer states of both n-butane and isobutane progressively decrease by 5-8 kJ/mol compared to Pt(111) as the surface concentration of Sn increases from 0.25 to 0.33 atom fraction in the respective surface alloys. The decrease in the desorption activation energy scales linearly with the Sn concentration. No thermal decomposition of either molecule on any surface occurred during TPD measurements. Molecular interactions probed by adsorption and desorption of saturated C[sub 4] hydrocarbons are not influenced as strongly by the presence of Sn in the Pt(111) surface as previously observed for unsaturated molecules, such as ethylene and isobutylene. 30 refs., 9 figs.

• OSTI ID: 5195321
• Journal Information: Langmuir; (United States), Vol. 10:1; ISSN 0743-7463
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
2-METHYLPROPANE
ADSORPTION
DESORPTION
BUTANE
CHEMICAL ACTIVATION
MASS SPECTROSCOPY
PLATINUM
PLATINUM ALLOYS
PROBABILITY
TIN ALLOYS
ULTRAHIGH VACUUM
ALKANES
ALLOYS
ELEMENTS
HYDROCARBONS
METALS
ORGANIC COMPOUNDS
PLATINUM METAL ALLOYS
PLATINUM METALS
SORPTION
SPECTROSCOPY
TRANSITION ELEMENTS
020400* - Petroleum- Processing
400201 - Chemical & Physicochemical Properties
400102 - Chemical & Spectral Procedures