Chain growth in the Fischer-Tropsch synthesis
Methanation and hydrocarbon synthesis from CO and H/sub 2/ was studied using 10 wt% Ni/Al/sub 2/O/sub 3/ and 10 wt% Fe/Al/sub 2/O/sub 3/ catalysts at 1 atm. Transient responses to the switches between various feed mixtures, especially isotopically labeled feeds, to a gradientless microreactor were used to obtain information on the amounts and reactivities of intermediates on and in the catalysts. On Ni/Al/sub 2/O/sub 3/, about 0.5 monolayer of adsorbed CO and smaller amounts of C are present during reaction. Infrared and CO/D/sub 2/ suggest that significant amounts of CH/sub x/ (x = 1-3) are not present. Chain growth experiments with /sup 13/CO/H/sub 2/ indicate that the hydrocarbons are formed primarily from C, but the results also indicate that the process is not fully understood. All steps in methanation and chain growth appear to be fast, except for the limiting steps CO ..-->.. C and C ..-->.. CH. On Fe/Al/sub 2/O/sub 3/, methanation and chain growth occur via CH, with all steps except the initial conversion of CH apparently being fast. Bulk iron carbides and an inactive form of carbon, different from C on Ni/Al/sub 2/O/sub 3/, do not participate significantly. The CH deactivates slowly with time on stream; only a small portion produces most of the products after 2 h on stream. Other work concerned H/sub 2/ chemisorption on various supported metal catalysts. Using TPD, an unusual spike was found after low temperature adsorption on Ru/SiO/sub 2/. The activated adsorption of H/sub 2/ on Fe/SiO/sub 2/, Fe/Al/sub 2/O/sub 3/, Ni/AlO/sub 3/, and Rh/TiO/sub 2/ was compared. It was suggested that, by analogy to titania-supported metals, the origin of the activation barrier may lie in a decoration phenomenon. It was proposed that SiO/sub x/ and AlO/sub x/ species may have been derived from small amounts of support which dissolved in the impregnating solution.
- Research Organization:
- Connecticut Univ., Storrs (USA)
- OSTI ID:
- 6715135
- Country of Publication:
- United States
- Language:
- English
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ACTIVATION ENERGY
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
CARBON 13
CARBON COMPOUNDS
CARBON ISOTOPES
CARBON MONOXIDE
CARBON OXIDES
CATALYST SUPPORTS
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHEMISORPTION
COMPARATIVE EVALUATIONS
DESORPTION
DEUTERIUM
ELEMENTS
ENERGY
EVEN-ODD NUCLEI
FISCHER-TROPSCH SYNTHESIS
HYDROCARBONS
HYDROGEN
HYDROGEN ISOTOPES
IRON
ISOTOPES
KINETICS
LABELLED COMPOUNDS
LIGHT NUCLEI
METALS
METHANATION
MINERALS
MOLECULAR WEIGHT
NICKEL
NONMETALS
NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PLATINUM METALS
REACTION INTERMEDIATES
REACTION KINETICS
RHODIUM
RUTHENIUM
SEPARATION PROCESSES
SILICA
SILICON COMPOUNDS
SILICON OXIDES
SORPTION
STABLE ISOTOPES
TEMPERATURE DEPENDENCE
TITANIUM COMPOUNDS
TITANIUM OXIDES
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS