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1656632 
Journal Article 
Deposition of iron from iron-carbonyl onto a working Co-based Fischer-Tropsch catalyst: The serendipitous discovery of a direct probe for diffusion limitation 
de Jong, KP; Post, MFM; Knoester, A 
1998 
1 
Studies in surface science and catalysis
ISSN: 0167-2991 
STUDIES IN SURFACE SCIENCE AND CATALYSIS 
119 
119-124 
WOS:000076939000018 
During fixed-bed pilot plant runs to test silica-supported cobalt-based Fischer Tropsch catalysts deposition of iron from iron carbonyl was encountered due to some contamination of the carbon monoxide feed gas. From analysis of the used catalysts it turned out that the iron (1-2 %m/m) had been deposited preferentially at the center of the 1.4 mm-sized particles. Furthermore, from transmission electron microscopy it appeared that iron had reacted with silica to form iron hydro-silicates, thus not deteriorating the catalytic performance. The iron distribution over the individual particles is concluded to reflect the intraparticle CO profile originating from diffusion limitation during catalysis. Deposition of iron from Fe(CO), during Fischer Tropsch catalysis can be considered as a probe for diffusion limitation and is a direct experimental evidence for the existence of concentration gradients in catalyst particles according to the classic Thiele-Wheeler concept.