Interaction of water-gas shift species with chromia-promoted magnetite
The interactions of H/sub 2/, H/sub 2/O, CO, and CO/sub 2/ were studied with respect to the mechanism of water-gas shift over chromia-promoted magnetite. Areas of study were pair-sites as adsorption sites. H/sub 2//H>O coadsorption and oxygen transfer between CO and CO/sub 2/. Adsorption on pair-sites consisting of adjacent, dissimilar atoms does not follow the Langmuir isotherm. Monte Carlo simulations and simple statistical arguments were used to study the number of available sites as a function of coverage. The deviations from the Langmuir isotherm cannot be observed unless surface coverages are measured with an uncertainty less than about 8% of the saturation coverage. The adsorption of H/sub 2//H/sub 2/O mixtures on chromia-promoted magnetite at 637 K was investigated. Data were collected volumetrically at constant H/sub 2/:H/sub 2/O ratios and fit to Langmuir-type adsorption isotherms. For a given H/sub 2/ partial pressure, a lower extent of H/sub 2/ adsorption was observed at a higher H/sub 2/O partial pressure, indicating that competition for adsorption sites occurred. At a constant H/sub 2/:H/sub 2/O ratio, the H/sub 2/ coverage as a function of H/sub 2/ partial pressure passed through a maximum, indicating that H/sub 2/ is dissociatively adsorbed. Equilibrium rates of adsorption/desorption and interconversion of CO and CO/sub 2/ were studied using isotopically labelled species. The interconversion of CO and CO/sub 2/ over chromia-promoted magnetite at 627 K occurs through an adsorbed intermediate. A kinetic model using rate constants calculated from the isotopic exchange data was found to be in good agreement with the water-gas shift rate.
- Research Organization:
- Wisconsin Univ., Madison (USA)
- OSTI ID:
- 7180586
- Country of Publication:
- United States
- Language:
- English
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Use of H/sub 2//H/sub 2/O gas mixtures to study adsorption on chromia-promoted magnetite at water-gas shift temperatures
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Related Subjects
010408* -- Coal
Lignite
& Peat-- C1 Processes-- (1987-)
ADSORPTION
ADSORPTION ISOTHERMS
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON MONOXIDE
CARBON OXIDES
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHROMIUM COMPOUNDS
CHROMIUM OXIDES
DESORPTION
ELEMENTS
HYDROGEN
IRON COMPOUNDS
IRON ORES
IRON OXIDES
ISOTHERMS
ISOTOPIC EXCHANGE
KINETICS
MAGNETITE
MASS TRANSFER
MATHEMATICAL MODELS
MINERALS
NONMETALS
ORES
OXIDE MINERALS
OXIDES
OXYGEN
OXYGEN COMPOUNDS
PRESSURE DEPENDENCE
REACTION KINETICS
SHIFT PROCESSES
SORPTION
SORPTIVE PROPERTIES
STEAM
SURFACE PROPERTIES
TRANSITION ELEMENT COMPOUNDS
WATER GAS PROCESSES