Platinum-tin catalysts supported on silica highly selective for n-hexane dehydrogenation

Journal Article · Sat Feb 01 04:00:00 EST 1997 · Journal of Catalysis

DOI:https://doi.org/10.1006/jcat.1997.1497· OSTI ID:518339

Llorca, J; Homs, N; Sales, J; Piscina, P.R. de la ^[1]

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1. Universitate de Barcelona (Spain); and others

Silica-supported Pt-Sn catalysts were prepared by two-step impregnation from [PtCl{sub 2}(PPh{sub 3}){sub 2}] and SnCl{sub 2} solutions of appropriate concentrations to yield Pt/Sn atomic ratios ranging from 0.2 to 5.0. In these systems, the presence of true Pt-Sn alloys was confirmed by X-ray diffraction, transmission electron microscopy, energy dispersive X-ray analysis and electron nanodiffraction. Pt and PtSn alloy phases were found on catalysts with Pt/Sn > 1, PtSn alloy alone on the catalyst with Pt/Sn = 1 and PtSn and PtSn{sub 2} alloys, together with Sn in the catalysts with Pt/Sn < 1. All these catalysts were tested in the skeletal reactions of n-hexane at 753 K and atmospheric pressure. The selectivity of Pt changed significantly when alloyed with tin. For Sn-rich compositions a segregation of tin toward the catalyst surface was shown by photoelectron spectroscopy, and high hydrogenolysis selectivity and fast deactivation were observed. In contrast, Pt-rich catalysts, in which a well defined PtSn alloy was observed, were much more stable and exhibited high selectivity to dehydrogenation reaction while maintaining low conversions to benzene and hydrogenolysis products. This selectivity pattern can be interpreted in terms of a change in adsorption properties due to differences in the number of adjacent Pt atoms required for the various reaction pathways. 24 refs., 11 figs., 3 tabs.

• OSTI ID: 518339
• Journal Information: Journal of Catalysis, Journal Name: Journal of Catalysis Journal Issue: 1 Vol. 166; ISSN 0021-9517; ISSN JCTLA5
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
40 CHEMISTRY
CATALYST SUPPORTS
CATALYSTS
CATALYTIC EFFECTS
CATALYTIC REFORMING
CHEMICAL REACTION YIELD
DEHYDROGENATION
ELECTRON DIFFRACTION
HEXANE
PHOTOELECTRON SPECTROSCOPY
PLATINUM
PLATINUM ALLOYS
SILICA
TIN
TIN ALLOYS
TRANSMISSION ELECTRON MICROSCOPY
X-RAY DIFFRACTION
X-RAY SPECTROSCOPY