Influence of hydrogen pretreatment on the structure of the metal-support interface in Pt/zeolite catalysts

Journal Article · Wed Dec 01 04:00:00 EST 1993 · Journal of Catalysis; (United States)

DOI:https://doi.org/10.1006/jcat.1993.1357· OSTI ID:5258403

Vaarkamp, M ^[1]; Modica, F S; Miller, J T ^[2]; Koningsberger, D C ^[3]

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1. Eindhoven Univ. of Technology, Eindhoven (Netherlands)
2. Amoco Oil Company, Naperville, IL (United States)
3. Utrecht Univ., Utrecht (Netherlands)

Platinum supported on H-LTL, K-LTL, and H-MAZ was reduced at temperatures from 573 to 873 K and the structure of the metal-support interface was determined by EXAFS. In all samples, the platinum was highly dispersed, with metal particle sizes from 5-11 atoms. After low temperature reduction (LTR, 573 K), the distance between the platinum atoms and the oxide atoms of the support (Pt-O distance) is 2.7 [angstrom], which is significantly longer than the Pt-O distance of 2.2 [angstrom] observed after high temperature reduction (HTR, 873 K). At intermediate reduction temperatures both the long and the short Pt-O distances are observed. The shortening of the Pt-O distance, combined with the decrease in both the Debye-Waller factor and the inner potential shift, implies a stronger interaction between the platinum atoms and the oxide support. A structural model is proposed wherein the longer Pt-O distance results from the presence of hydrogen in the interfacial layer between the metal particle and the support. During high temperature reduction, the hydrogen is released from the interface, leaving platinum in direct contact with the support. The shortening of the Pt-O interfacial distance is accompanied by a decrease in the hydrogen chemisorption capacity, and may additionally be related to changes in the catalytic properties. 41 refs., 11 figs., 5 tabs.

• OSTI ID: 5258403
• Journal Information: Journal of Catalysis; (United States), Journal Name: Journal of Catalysis; (United States) Vol. 144:2; ISSN 0021-9517; ISSN JCTLA5
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
CATALYST SUPPORTS
ELEMENTS
INORGANIC ION EXCHANGERS
ION EXCHANGE MATERIALS
MATERIALS
METALS
MINERALS
PLATINUM
PLATINUM METALS
SILICATE MINERALS
SPECTROSCOPY
STRUCTURAL CHEMICAL ANALYSIS
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE
TEMPERATURE RANGE 0400-1000 K
TRANSITION ELEMENTS
X-RAY SPECTROSCOPY
ZEOLITES