Promoted cobalt silica gel catalysts for Fischer-Tropsch synthesis
Date
2013
Authors
Ming, H.
Editors
Kobayashi, Y.
Suzuki, H.
Suzuki, H.
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Book chapter
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Source details - Title: Cobalt: occurrence, uses and properties, 2013 / Kobayashi, Y., Suzuki, H. (ed./s), Ch.2, pp.61-100
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Abstract
Cobalt (Co) silica gel catalysts for Fischer–Tropsch (F-T) synthesis were prepared by introducing ionic species such as Al, Fe, and rare earth (RE) elements onto the surface of silica gel followed by the addition of Co species on to the modified surface. The F-T activity of the prepared catalysts was studied to compare their catalytic performance during F-T reaction. The surface and interfacial characteristics of the catalysts were further investigated systematically by various analytical techniques. Experiment results showed that physiochemical characteristics of the ionic species incorporated into the semiconducting matrix, silica gel, can play a significant role in determining the speciation of the Co loaded so that the overall catalytic performance including activity and selectivity of the F-T catalyst is affected. Among the ionic species used for preparing the Co F-T catalyst, the catalyst with praseodymium (Pr) impregnated on the surface of the silica gel exhibited good F-T activity and favorable product distribution. The results showed that Pr added onto the surface of the silica gel readily substitutes silicon atoms in tetrahedral coordination to form a negatively charged centre in the lattice of silica surface. The majority of Co on the surface of the Pr promoted silica gel were mixtures of Co oxide, silicate or hydrosilicate species which can be reduced to metallic phase during activation. The reduced Co species were well dispersed on the surface of the silica gel which indicates that it can uptake more hydrogen than the unpromoted Co silica gel catalyst in their activated form at temperatures below 300 ˚C. It is concluded that high reducibility in Co species in the catalyst, good interfacial property between metallic Co phase and the surface of the silica gel, and excellent promoting function of Pr make the Pr promoted Co silica gel catalyst performs best among all.
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Copyright 2013 Nova Science Publishers