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

Thesis/Dissertation · Sat Jan 01 04:00:00 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
• Country of Publication: United States
• Language: English

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10 SYNTHETIC FUELS
ALCOHOLS
ALKALI METAL COMPOUNDS
ALKENES
CARBIDES
CARBON COMPOUNDS
CATALYSTS
CATALYTIC EFFECTS
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HYDROCARBONS
HYDROXY COMPOUNDS
IRON CARBIDES
IRON COMPOUNDS
IRON NITRIDES
KINETICS
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MOESSBAUER SPECTROMETERS
MOLECULAR WEIGHT
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OXIDE MINERALS
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POTASSIUM NITRIDES
PRESSURE EFFECTS
REACTION KINETICS
SCATTERING
SILICA
SILICON COMPOUNDS
SILICON OXIDES
SPECTROMETERS
TRANSITION ELEMENT COMPOUNDS
X-RAY DIFFRACTION
YIELDS