Effect of water on the space-time yield of different supported cobalt catalysts during Fischer-Tropsch synthesis
2011 (English)In: Applied Catalysis A: General, ISSN 0926-860X, E-ISSN 1873-3875, Vol. 393, no 1-2, 109-121 p.Article in journal (Refereed) Published
The effect of partial pressure of water on the Fischer-Tropsch (FT) rate of six cobalt-based catalysts supported on three different carrier materials (gamma-Al2O3, alpha-Al2O3, TiO2) with varying Co particle sizes was investigated in a fixed-bed reactor by changing space velocity and by external water vapour addition. A typical catalyst pellet size (<100 mu m) for industrial slurry-bed FT reactors was used. Water was found to have a positive kinetic effect, at least up to moderate amounts, on the FT rate of all catalysts in the present study, including the gamma-Al2O3-supported catalyst with pores smaller than similar to 10 nm. The reason for the apparent negative effect on the space-time yield at a direct exposure of Co supported on narrowpore gamma-Al2O3 to high partial pressures of water is due to a rapid and extensive deactivation. This could be ascribed to formation of hard-to-reduce oxidized cobalt species. The choice of support material was found to have a major effect on the response to changes in partial pressure of water, both with respect to deactivation behaviour and kinetics. However, there is a minor Co-particle size effect on the magnitude of the kinetic effect of water, larger Co particles showing a more positive response. Different extents of mass transfer limitations and/or differences in fugacities of H-2, CO and water among the six catalysts could be ruled out as causes for the observed differences.
Place, publisher, year, edition, pages
2011. Vol. 393, no 1-2, 109-121 p.
Fischer-Tropsch, Cobalt, Water, Deactivation, Particle size, Microemulsion
IdentifiersURN: urn:nbn:se:kth:diva-31381DOI: 10.1016/j.apcata.2010.11.030ISI: 000287619400014ScopusID: 2-s2.0-78951475669OAI: oai:DiVA.org:kth-31381DiVA: diva2:403820
QC 201103152011-03-152011-03-142011-03-15Bibliographically approved