On the selectivity of cobalt-based Fischer-Tropsch catalysts: Evidence for a common precursor for methane and long-chain hydrocarbons
2010 (English)In: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 274, no 1, 84-98 p.Article in journal (Refereed) Published
A total of 36 cobalt-based supported catalysts were investigated in the Fischer-Tropsch reaction at industrially relevant process conditions: 483 K, 20 bar, molar H-2/CO ratio = 2.1, pellet size: 53-90 mu m. The effect of adding water vapour to the feed was investigated for 20 of the catalysts, and a H-2/CO ratio of 1.0 was used for a few catalysts. The catalysts differed in support material, Co loading, promoters, Cl content, Co particle size (larger than similar to 6 nm), morphology, degree of reduction and preparation technique and showed a large variation in selectivity. For each set of process conditions, a linear relationship seems to exist between the selectivity to methane (and other light products) and C5+ indicating a common precursor, i.e. a common monomer pool, for all hydrocarbon products. A high selectivity to C5+ is mainly an effect of a high intrinsic chain-growth probability and unlikely to be a result of an enhanced cc-olefin readsorption. The universal effect of external water addition on the hydrocarbon selectivities is limited to a decrease in the methane selectivity. A small proportion of the catalysts developed "pure methanation" sites upon exposure to high partial pressures of water.
Place, publisher, year, edition, pages
2010. Vol. 274, no 1, 84-98 p.
Fischer-Tropsch, Cobalt, Selectivity, ASF, Alpha value, Methane, Water, H-2/CO ratio
IdentifiersURN: urn:nbn:se:kth:diva-26827DOI: 10.1016/j.jcat.2010.06.007ISI: 000281320700008ScopusID: 2-s2.0-77955585587OAI: oai:DiVA.org:kth-26827DiVA: diva2:375159
QC 201012072010-12-072010-11-292013-07-19Bibliographically approved