Adsorption and desorption of hydrogen and carbon monoxide were studied on alumina-supported iridium catalysts
The adsorption and desorption of hydrogen and carbon monoxide were studied on alumina-supported iridium catalysts which were examined by a scanning transmission electron microscope (STEM). The metal particle size and number of particles per area of catalyst increased with increasing metal loading. The particles were approx. 10 A. in diameter, cubo-octahedral shaped, and approx. 80-90% disperse. The STEM electron beam caused negligible damage to the samples. Hydrogen adsorption measurements showed that the hydrogen-iridium atom ratio was 1.2:1-1.3:1 and increased with decreasing metal loading. Temperature-programed desorption showed four types of adsorbed hydrogen desorbing at -90/sup 0/C (I), 15/sup 0/C (IV), 115/sup 0/C (II), and 245/sup 0/C (III). Types II and IV desorb from single atom sites and Types I and III from multiple atom sites. Type I is in rapid equilibrium with the gas phase. All desorption processes appear to be first order. Carbon monoxide adsorbed nondissociatively at 25/sup 0/C with approx. 0.7:1 CO/Ir atom ratio. It adsorbed primarily in linear forms at low coverage, but a bridged form appeared at high coverage.
- OSTI ID:
- 6200165
- Resource Relation:
- Other Information: Thesis (Ph.D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
CARBON MONOXIDE
ADSORPTION
DESORPTION
CATALYSTS
MICROSTRUCTURE
SORPTIVE PROPERTIES
HYDROGEN
ATOMS
CATALYST SUPPORTS
EXPERIMENTAL DATA
IRIDIUM
LOADING
PARTICLE SIZE
TRANSMISSION ELECTRON MICROSCOPY
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
CRYSTAL STRUCTURE
DATA
ELECTRON MICROSCOPY
ELEMENTS
INFORMATION
MATERIALS HANDLING
METALS
MICROSCOPY
NONMETALS
NUMERICAL DATA
OXIDES
OXYGEN COMPOUNDS
PLATINUM METALS
SIZE
SORPTION
SURFACE PROPERTIES
TRANSITION ELEMENTS
400201* - Chemical & Physicochemical Properties
400301 - Organic Chemistry- Chemical & Physicochemical Properties- (-1987)