Sintering and carbidization under simulated high conversion on a cobalt-based Fischer-Tropsch catalyst; manganese oxide as a structural promotor
Luke M. van Koppen (TU Delft - RST/Fundamental Aspects of Materials and Energy, Eindhoven University of Technology)
A. I. Dugulan (TU Delft - RID/TS/Instrumenten groep)
G. Bezemer (Shell Global Solutions International B.V.)
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Abstract
The commercial application of cobalt-based Fischer-Tropsch synthesis (FTS) suffers from catalyst deactivation. One of the main deactivation mechanisms under industrial conditions is sintering. In this work, we explored the role of manganese oxide as a structural promoter against sintering in a carbon nanofiber supported cobalt model catalyst. We employed in situ Mössbauer emission spectroscopy to study cobalt sintering in synthesis gas as a function of the steam partial pressure, which mimics high CO conversion during FTS. Steam accelerates the sintering of non-promoted metallic cobalt particles. Model experiments point to a synergistic effect between carbon monoxide and steam on cobalt sintering. In the mangense-promoted case, sintering is significantly reduced, indicative of the structural stabilization of small cobalt particles by manganese oxide. Nevertheless, a fraction of cobalt particles in close interaction with manganese oxide carburized under these conditions, resulting in a lower catalytic activity.
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