Identification of a weak adsorption state of carbon monoxide on highly dispersed, alumina-supported platinum
Temperature-programmed desorption of CO from 0.1 wt % platinum/alumina (Pt/Al/sub 2/O/sub 3/) was measured as a thin wafer of the material was heated in vacuum. At a Pt dispersion of 100% (CO/Pt = 0.92), a relatively tall, narrow CO desorption peak was obtained at low temperatures (355 K at 0.93 K s/sup -1/) followed by a low, broad desorption band extending to 750 K. As the Pt dispersion decreased to 80% (CO/Pt = 0.70) and then 70% (CO/Pt = 0.64) as a result of pretreatment in O/sub 2/ and H/sub 2/, the fraction of CO that desorbed in the low-temperature peak decreased and the fraction of CO that desorbed in the broad desorption band increased. At Pt dispersions below 40%, only a broad desorption band was obtained, a result which is in agreement with data reported by others. The low-temperature peak is interpreted as desorption of CO from very small Pt particles (< 20 atoms, < 1.1 nm) supported on transitional Al/sub 2/O/sub 3/. The broad desorption band is interpreted as CO desorption from larger Pt particles. Results from experiments performed at different heating rates indicate that the enthalpy of CO adsorption in the state that corresponds to the low-temperature peak is 74 +- 4 kJ mol/sup -1/, an adsorption energy which is lower than energies obtained from measurements of CO desorption from Pt single crystal surfaces. 5 figures.
- Research Organization:
- General Motors Research Labs., Warren, MI
- OSTI ID:
- 5862780
- Journal Information:
- J. Catal.; (United States), Vol. 81:2
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
10 SYNTHETIC FUELS
CARBON MONOXIDE
CHEMISORPTION
DESORPTION
PLATINUM
SORPTIVE PROPERTIES
ALUMINIUM OXIDES
CATALYST SUPPORTS
CATALYSTS
ENTHALPY
EXPERIMENTAL DATA
HEATING RATE
HIGH TEMPERATURE
HYDROGENATION
MASS SPECTRA
MEDIUM TEMPERATURE
OXIDATION
QUANTITY RATIO
STRUCTURAL CHEMICAL ANALYSIS
TEMPERATURE DEPENDENCE
ALUMINIUM COMPOUNDS
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
CHEMICAL REACTIONS
DATA
ELEMENTS
INFORMATION
METALS
NUMERICAL DATA
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
PLATINUM METALS
SEPARATION PROCESSES
SORPTION
SPECTRA
SURFACE PROPERTIES
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENTS
400201* - Chemical & Physicochemical Properties
090121 - Hydrocarbon Fuels- Chemical Synthesis- (1976-1989)