Hydrogen temperature-programmed desorptions in platinum caltalysts: Decomposition and isotopic exchange by spillover hydrogen of chemisorbed ammonia

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

DOI:https://doi.org/10.1006/jcat.1996.0062· OSTI ID:263769

Miller, J T; Meyers, B L; Barr, M K ^[1]

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1. AMOCO Research Center, Naperville, IL (United States); and others

H{sub 2}-TPD of Pt/alumina catalysts display multiple hydrogen desorptions. In addition to chemisorbed hydrogen (Peak I) at approximately 175{degrees}C, there is a small hydrogen desorption (Peak II) at about 250{degrees}C and a large, irreversible hydrogen desorption (Peak III) at 450{degrees}C. The quantity of hydrogen associated with Peak III decreases with increasing precalcination temperature of the alumina. It is shown that the hydrogen from Peak III is caused by decomposition of ammonia chemisorbed on acid sites of the alumina, which are introduced during the catalyst`s preparation. In the presence of Pt, the chemisorbed ammonia undergoes isotopic exchange with D{sub 2} by a spillover hydrogen process, even in mixtures where chemisorbed ammonia and Pt are located on separate support particles. Although spillover hydrogen species affect deuterium exchange of ammonium ions, they do not contribute to the catalytic activity of platinum for neopentane hydrogenolysis or isomerization. 50 refs., 9 figs., 5 tabs.

• OSTI ID: 263769
• Journal Information: Journal of Catalysis, Journal Name: Journal of Catalysis Journal Issue: 1 Vol. 159; ISSN 0021-9517; ISSN JCTLA5
• Country of Publication: United States
• Language: English

Related Subjects

40 CHEMISTRY
ALUMINIUM OXIDES
AMMONIA
CATALYST SUPPORTS
CATALYSTS
CATALYTIC EFFECTS
CHEMISORPTION
DESORPTION
DEUTERIUM
HYDROGEN
HYDROGENATION
ISOMERIZATION
ISOTOPIC EXCHANGE
PENTANE
PLATINUM
SORPTIVE PROPERTIES
TEMPERATURE DEPENDENCE