Highly dispersed MgO-supported model Pd-Mo catalysts prepared from bimetallic clusters

Journal Article · Thu May 04 04:00:00 EDT 1995 · Journal of Physical Chemistry

DOI:https://doi.org/10.1021/j100018a026· OSTI ID:50479

Kawi, S; 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)

In attempts to prepare highly dispersed supported palladium catalysts stabilized by molybdenum, an organometallic precursor with Pd-Mo bonds, [Pd{sub 2}Mo{sub 2}(Cp){sub 2}(CO){sub 6}(PPh{sub 3}){sub 2}], was adsorbed on MgO. The precursor was adsorbed intact, as shown by infrared spectroscopy. For comparison, other samples were prepared from an organopalladium precursor, [PdCl{sub 2}(PhCN){sub 2}], and from a mixture of [PdCl{sub 2}(PhCN){sub 2}] + [Mo(CO){sub 6}]. Each supported sample was treated in H{sub 2} at various temperatures to form metallic palladium. The palladium dispersions were characterized by chemisorption of H{sub 2}, CO, and O{sub 2}; transmission electron microscopy; temperature-programmed desorption of adsorbed CO; and extended X-ray absorption fine structure (EXAFS) spectroscopy, both at the Pd K edge and the Mo K edge. The data show that the presence of molybdenum in the bimetallic precursor helped to maintain the palladium in a highly dispersed form, with the supported clusters being smaller than about 10 A, in average diameter. These clusters have a low capacity for chemisorption of hydrogen and of CO. They are stabilized by the oxophilic molybdenum, which exists preferentially at the interface between the palladium clusters and the metal oxide support. 28 refs., 9 figs., 7 tabs.

• Research Organization: Brookhaven National Laboratory (BNL), Upton, NY
• DOE Contract Number: FG05-89ER45384; AC02-76CH00016
• OSTI ID: 50479
• Journal Information: Journal of Physical Chemistry, Journal Name: Journal of Physical Chemistry Journal Issue: 18 Vol. 99; ISSN JPCHAX; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
40 CHEMISTRY
ADSORPTION
BIMETALS
CARBON MONOXIDE
CATALYST SUPPORTS
CATALYSTS
CHEMISORPTION
EXPERIMENTAL DATA
HYDROGEN
INFRARED SPECTRA
MAGNESIUM OXIDES
MOLYBDENUM COMPOUNDS
ORGANOMETALLIC COMPOUNDS
OXYGEN
PALLADIUM COMPOUNDS
STRUCTURAL CHEMICAL ANALYSIS
SYNTHESIS