Carbon deposition from propylene on polycrystalline and single crystal iron
In a study of Fischer-Tropsch catalyst poisoning, experiments showed that the rate of carbon deposition from propylene on polycrystalline iron foil or single crystal iron surfaces went through a maximum at approx. 600/sup 0/C. Carbon formation from propylene occurred only in the presence of hydrogen, increased with increasing hydrogen partial pressure, and was independent of propylene partial pressure. No gasification of carbon by hydrogen occurred up to 530/sup 0/C. Iron was always distributed throughout the carbon, presumably as iron carbide. An analysis of the data suggested that below 600/sup 0/C, carbon formed via monocarbon fragments and iron carbide intermediates, and that on fresh surfaces, the reaction which had an activation energy of 36 kcal/mole, was rate-limited by the migration of carbon from iron carbide through the bulk ..cap alpha..-iron. As the deposition of carbon proceeds, encapsulation builds up, iron carbide accumulates on the surface, and the reaction changes to an iron carbide-catalyzed production of carbon as the rate-determining step of a reaction whose apparent activation energy is 21 kcal/mole. Above 600/sup 0/C, the activation energies for fresh and used iron become negative and the rate-controlling step is apparently the surface reaction.
- Research Organization:
- Norges Tek. Hoegsk., Trondheim
- OSTI ID:
- 6318491
- Journal Information:
- J. Catal.; (United States), Journal Name: J. Catal.; (United States) Vol. 62:1; ISSN JCTLA
- Country of Publication:
- United States
- Language:
- English
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10 SYNTHETIC FUELS
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201 -- Chemical & Physicochemical Properties
ACTIVATION ENERGY
ALKENES
CARBIDES
CARBON
CARBON COMPOUNDS
CATALYSTS
CATALYTIC EFFECTS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CRYSTAL STRUCTURE
DATA
DATA ANALYSIS
DEPOSITION
ELEMENTS
ENCAPSULATION
ENERGY
EXPERIMENTAL DATA
FISCHER-TROPSCH SYNTHESIS
FOILS
HIGH TEMPERATURE
HYDROCARBONS
HYDROGEN
INFORMATION
IRON
IRON CARBIDES
IRON COMPOUNDS
KINETICS
METALS
NONMETALS
NUMERICAL DATA
ORGANIC COMPOUNDS
PARTIAL PRESSURE
POISONING
PRESSURE DEPENDENCE
PROPYLENE
REACTION INTERMEDIATES
REACTION KINETICS
SURFACES
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS