In-situ Moessbauer Spectroscopy of Supported Iron Fischer-Tropsch Catalysts During Activation

Journal Article · Tue Apr 26 04:00:00 EDT 2005 · AIP Conference Proceedings

DOI:https://doi.org/10.1063/1.1923633· OSTI ID:20722165

Motjope, Thato R; Dlamini, Thulani H ^[1]

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1. Sasol Technology, 1 Klasie Havenga Avenue, Sasolburg, 1947 (South Africa)

The behavior of Fe based catalysts supported on ZrO2, SiO2, {gamma}-Al2O3, CeO2 and TiO2 during calcination, reduction and FT synthesis have been studied via in situ Moessbauer spectroscopy. It was found that the type of metal support interaction i.e. surface migration or bulk diffusion during calcination was dependant on the type of support used. Surface migration of Fe3+ during calcination was dominant for ZrO2, CeO2 and {gamma}-Al2O3 and this resulted in the sintering of {alpha}-Fe2O3 crystallites. Whereas bulk diffusion was observed mainly for the catalysts prepared using SiO2 and TiO2, causing a stabilization of the small crystallites of Fe3+ that interacted strongly with the support. Upon reduction, the large crystallites of {alpha}-Fe2O3 were found to reduce readily compared to the small crystallites of Fe3+, except for the catalyst prepared using {gamma}-Al2O3, as a support, where the presence of Al3+ resulted in the formation of spinel like species with the formula (Fe{sup 3+}{sub 2-x}Al{sup 3+}{sub x}Fe{sup 2+})O{sub 4} which are resistant to reduction. Upon exposure to synthesis gas, it was found that catalysts supported on ZrO2 and CeO2 carburized readily resulting in the formation of circa 80% {chi}-Fe2.5C. From this study it was observed that {gamma}-Al2O3 is not the preferred support for Fe based FT catalysts, as it forms the least amount of Fe carbides during FT synthesis.

• OSTI ID: 20722165
• Journal Information: AIP Conference Proceedings, Journal Name: AIP Conference Proceedings Journal Issue: 1 Vol. 765; ISSN APCPCS; ISSN 0094-243X
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM OXIDES
CALCINATION
CATALYSIS
CATALYSTS
CERIUM OXIDES
DIFFUSION
FISCHER-TROPSCH SYNTHESIS
HEAT TREATMENTS
IRON CARBIDES
IRON IONS
IRON-ALPHA
MOESSBAUER EFFECT
REDUCTION
SILICON OXIDES
SINTERING
SPINELS
SYNTHESIS GAS
TITANIUM OXIDES
ZIRCONIUM OXIDES