Hydrogen temperature-programmed desorption (H[sub 2] TPD) of supported platinum catalysts

Journal Article · Fri Oct 01 04:00:00 EDT 1993 · Journal of Catalysis; (United States)

DOI:https://doi.org/10.1006/jcat.1993.1285· OSTI ID:5155855

Miller, J T; Meyers, B L; Modica, F S; Lane, G S ^[1]; Vaarkamp, M ^[2]; Koningsberger, D C ^[3]

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1. AMOCO Research Center, Naperville, IL (United States)
2. Eindhoven Univ. of Technology (Netherlands)
3. Utrecht Univ. (Netherlands)

Hydrogen temperature-programmed desorption (TPD) of supported platinum catalysts, Pt/K-LTL, Pt/H-LTL, Pt/K-MAZ, Pt/H-MAZ, Pt/[gamma]-Al[sub 2]O[sub 3], and Pt/SiO[sub 2], was performed after hydrogen reduction at 300, 450, or 650[degrees]C. For all catalysts, reversible desorption of chemisorbed hydrogen occurred at approximately 175[degrees]C. In addition to chemisorbed H[sub 2], at least three peaks corresponding to higher temperature, irreversibly desorbed H[sub 2] were observed and assigned to spillover hydrogen. The quantity of spillover hydrogen is related to the number of support hydroxyl groups and the maximum reduction temperature of the catalyst. It is suggested that the irreversibility of the spillover hydrogen results from dehydroxylation of the support at high temperature. The structure of Pt/K-LTL and Pt/H-LTL catalysts has been examined by EXAFS following reduction at 300, 450, and 600[degrees]C. After low-temperature reduction, it is proposed that a layer of spillover hydrogen is present between the platinum particle and the support. The distance between the platinum and the support (oxide) surface is ca. 2.6-2.7[angstrom]. During high-temperature reduction, or during TPD, the interfacial hydrogen is irreversibly lost, and the platinum-oxygen distance decreases to 2.2 [angstrom]. The catalysts' turnover frequency (TOF) for propane hydrogenolysis was dependent on both the reduction temperature and the type of support. Platinum on acidic supports and reduced at the lowest temperature displayed the highest TOF. Qualitatively, the catalysts' hydrogenolysis activity increased with increasing amounts of spillover hydrogens. 34 refs., 15 figs., 4 tabs.

• OSTI ID: 5155855
• Journal Information: Journal of Catalysis; (United States), Journal Name: Journal of Catalysis; (United States) Journal Issue: 2 Vol. 143:2; 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
ALKANES
CATALYST SUPPORTS
CATALYTIC EFFECTS
CHEMICAL REACTIONS
COMPLEXES
DESORPTION
ELEMENTS
HYDROCARBONS
HYDROGEN
HYDROGENATION
NONMETALS
ORGANIC COMPOUNDS
PLATINUM COMPLEXES
PROPANE
SORPTION
SORPTIVE PROPERTIES
SPECTROSCOPY
SURFACE PROPERTIES
TEMPERATURE DEPENDENCE
TRANSITION ELEMENT COMPLEXES
X-RAY SPECTROSCOPY