Silica supported iron catalysts for the Fischer-Tropsch synthesis: catalyst characterization and promoter effects

Thesis/Dissertation · Sat Jan 01 00:00:00 EST 1983

OSTI ID:6347031

Yeh, E B

The objective of this research is to study the nitrogen effect on silica supported iron catalyst in the Fischer-Tropsch synthesis and to compare the effect with potassium promotion. Four silica supported catalysts were utilized in the Fischer-Tropsch process at pressures of 1, 7.8 and 14 atmospheres, and at 250/sup 0/C. The catalysts used were reduced iron (Fe-carbide), reduced and nitrided iron (Fe-nitride), potassium-promoted reduced iron (Fe-K-carbide) and potassium-promoted reduced and nitrided iron (Fe-K-nitride). Both Fe-carbide and Fe-nitride catalysts were characterized using x-ray diffraction and Moessbauer spectroscopy. No obvious changes in particle size after 12 hours of nitridation at 490/sup 0/C were observed. In the first 3 hours of reaction in the syngas environment, the Fe-nitride catalyst became increasingly iron rich, indicating that the nitrogen atoms removed by reduction were not simultaneously replaced by carbon atoms. Moessbauer spectroscopy and reaction studies showed that the Fe-nitride catalyst became stable after 18 and 25 hours, respectively, in the syngas environment. Synthesis reactions indicated that Fe-carbide catalysts was more active at lower pressures and less active at higher pressures than Fe-nitride. Moreover, it was found that potassium promoted catalysts were less active than catalysts without potassium. Both Fe-nitride and potassium promoted catalysts showed higher olefin selectivities, higher water-gas shift activity, lower alcohol yields and larger proportion of higher molecular weight products than their unpromoted counterparts. From the product distribution of Fe-nitride and potassium promoted catalyst, it is concluded that nitrogen and potassium have a similar promoting function on the Fischer-Tropsch reactions and that an additive effect is observed in Fe-K-nitride catalyst.

• OSTI ID: 6347031
• Resource Relation: Other Information: Thesis (Ph. D.)
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
10 SYNTHETIC FUELS
FISCHER-TROPSCH SYNTHESIS
CATALYSTS
IRON CARBIDES
CATALYTIC EFFECTS
IRON NITRIDES
POTASSIUM CARBIDES
POTASSIUM NITRIDES
ALCOHOLS
ALKENES
CHEMICAL COMPOSITION
CHEMICAL REACTION KINETICS
CHEMICAL REACTION YIELD
HYDROCARBONS
MOESSBAUER SPECTROMETERS
MOLECULAR WEIGHT
NITROGEN
PRESSURE EFFECTS
SILICA
X-RAY DIFFRACTION
ALKALI METAL COMPOUNDS
CARBIDES
CARBON COMPOUNDS
CHALCOGENIDES
CHEMICAL REACTIONS
COHERENT SCATTERING
DIFFRACTION
ELEMENTS
GAMMA SPECTROMETERS
HYDROXY COMPOUNDS
IRON COMPOUNDS
KINETICS
MEASURING INSTRUMENTS
MINERALS
NITRIDES
NITROGEN COMPOUNDS
NONMETALS
ORGANIC COMPOUNDS
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PNICTIDES
POTASSIUM COMPOUNDS
REACTION KINETICS
SCATTERING
SILICON COMPOUNDS
SILICON OXIDES
SPECTROMETERS
TRANSITION ELEMENT COMPOUNDS
YIELDS
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090121 - Hydrocarbon Fuels- Chemical Synthesis- (1976-1989)