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

• Published in: Langmuir 1994-01, Vol.10 (1), p.166-171
• Main Authors: Xu, Chen, Koel, Bruce E, Paffett, Mark T
• Format: Article
• Language: English
• Subjects: 02 PETROLEUM; 020400 - Petroleum- Processing; 2-METHYLPROPANE; 400102 - Chemical & Spectral Procedures; 400201 - Chemical & Physicochemical Properties; ADSORPTION; ALKANES; ALLOYS; BUTANE; CHEMICAL ACTIVATION; Chemistry; DESORPTION; ELEMENTS; Exact sciences and technology; General and physical chemistry; HYDROCARBONS; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; MASS SPECTROSCOPY; METALS; ORGANIC COMPOUNDS; PLATINUM; PLATINUM ALLOYS; PLATINUM METAL ALLOYS; PLATINUM METALS; PROBABILITY; Solid-gas interface; SORPTION; SPECTROSCOPY; Surface physical chemistry; TIN ALLOYS; TRANSITION ELEMENTS; ULTRAHIGH VACUUM
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/la00013a025

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.