Characterization of iron alloy Fischer-Tropsch catalysts
The characterization of iron alloy Fischer-Tropsch catalysts including Fe/Si0/sub 2/, 4Fe:Ni:Si0/sub 2/, Ni/Si0/sub 2/, Co/Si0/sub 2/, and 4Fe:Co/Si0/sub 2/, at various times in the synthesis was carried out by X-ray diffraction (XRD), Moessbauer spectroscopy (MES), temperature-programed reduction (TPR), and temperature programed carburization (TPC). Alloy formation was verified for 4Fe:Ni/SiO/sub 2/ and 4Fe:Co/SiO/sub 2/. The reductions proceeded stepwise from the initial oxide through intermediate oxides to the metallic state, and support interactions and alloying effects were observed. All of the catalysts readily carburized, and various coking regimes were identified at higher temperatures. Nickel enhanced the rate of iron carbide formation. TPC in a 3H/sub 2//CO mixture showed that the presence of hydrogen increased the rates of coking and carbide formation for all iron-containing catalysts. Based on these results, a mechanism is proposed for the Fischer-Tropsch synthesis which assumes that the active reaction site is an equilateral metal triplet on a close packed metal surface.
- OSTI ID:
- 6528129
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
10 SYNTHETIC FUELS
ALLOYS
CARBURIZATION
CATALYSTS
CATALYTIC EFFECTS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
COBALT ALLOYS
FISCHER-TROPSCH SYNTHESIS
HARDENING
IRON ALLOYS
KINETICS
NICKEL ALLOYS
REACTION INTERMEDIATES
REACTION KINETICS
REDUCTION
STRUCTURAL CHEMICAL ANALYSIS
SURFACE HARDENING
SURFACE TREATMENTS
SURFACES
TEMPERATURE EFFECTS