MgO-supported platinum-tungsten catalysts prepared from organometallic precursors: Platinum clusters isolated in dispersed tungsten

Journal Article · Fri Nov 01 04:00:00 EST 1996 · Journal of Catalysis

DOI:https://doi.org/10.1006/jcat.1996.0357· OSTI ID:486371

Alexeev, O; Gates, B C ^[1]; Shelef, M ^[2]

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1. Univ. of California, Davis, CA (United States)
2. Ford Motor Co., Dearborn, MI (United States)

MgO-supported Pt and Pt-W catalysts were prepared from organometallic precursors and characterized to determine how the nature of the precursors and the treatment conditions affected the Pt-W interactions and the catalytic activity for toluene hydrogenation. Samples were prepared from (Pt[W(CO){sub 3}(C{sub 5}H{sub 5})]{sub 2}(PhCN){sub 2}) (Ph=phenyl) and from [PtCl{sub 2}(PhCN){sub 2}] + [W(CO){sub 6}] and characterized by infrared spectroscopy, extended X-ray absorption fine structure (EXAFS) spectroscopy, transmission electron microscopy (TEM), and chemisorption of H{sub 2}, CO, and O{sub 2}. The samples were treated in H{sub 2} at 400{degrees}C prior to most of the characterizations. Incorporation of W reduced the chemisorption of CO and of H{sub 2}, with the reduction in chemisorption being greater for the catalyst prepared from (Pt[W(CO){sub 3}(C{sub 5}H{sub 5})]{sub 2}(PhCN){sub 2}) than for the catalyst prepared from the combination of monometallic precursors. EXAFS spectra measured at both the Pt L{sub II} edge and the W L{sub III} edge showed substantial Pt-W contributions for the former catalyst (but not the latter), with a Pt-W coordination number of about 2 and an average Pt-W distance of 2.71 {Angstrom}. TEM and EXAFS results indicate that interactions between Pt and W cations in the sample made from (Pt[W(CO){sub 3}(C{sub 5}H{sub 5})]{sub 2}(PhCN){sub 2}) maintained the Pt in a highly dispersed form, with supported Pt clusters being smaller than about 10 {Angstrom}. The catalyst prepared from the bimetallic cluster was more than an order of magnitude less active for toluene hydrogenation at 1 atm and 60{degrees}C than the catalyst prepared from the two monometallic precursors; the comparison indicates that the W acted like an isolated dispersed support, with its influence on the catalysis maximized by its proximity to the Pt. 62 refs., 6 figs., 13 tabs.

• Research Organization: Brookhaven National Laboratory (BNL), Upton, NY
• DOE Contract Number: FG05-89ER45384; AC02-76CH00016
• OSTI ID: 486371
• Journal Information: Journal of Catalysis, Journal Name: Journal of Catalysis Journal Issue: 1 Vol. 164; ISSN JCTLA5; ISSN 0021-9517
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
40 CHEMISTRY
ABSORPTION SPECTROSCOPY
CARBON MONOXIDE
CATALYST SUPPORTS
CATALYSTS
CATALYTIC EFFECTS
CHEMISORPTION
HETEROGENEOUS CATALYSIS
HYDROGEN
HYDROGENATION
ORGANOMETALLIC COMPOUNDS
OXYGEN
PLATINUM
REDUCTION
SORPTIVE PROPERTIES
TOLUENE
TRANSMISSION ELECTRON MICROSCOPY
TUNGSTEN
X-RAY SPECTROSCOPY