Activity and selectivity of iron Fischer-Tropsch catalysts in a stirred tank slurry reactor
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Four catalysts prepared by two catalyst manufacturers (UCI and Ruhrchemie) were tested in a stirred tank slurry reactor to determine their performance during Fischer-Tropsch synthesis. Precipitated iron was used as the active metal, and Cu, K and SiO2were used as promoters. The amounts of promoters (in parts per weight per 100 parts of iron) in these four catalysts were as follows: SiO2= 4.1-25; K = 1.1-8.7 and Cu = 1.4-7.5. Total BET surface area varied between 136 and 290 m2/g. The Ruhrchemie and two of the UCI's catalysts (runs SA-3391 and SA-2052) had low deactivation rates, whereas the UCI catalyst with low silica content (run SA-1532) deactivated more rapidly. The intrinsic activity of the low silica catalyst, measured by apparent first order reaction rate constant, was the lowest, whereas the Ruhrchemie catalyst had the highest activity (per gram of iron basis). Activity of the Ruhrchemie catalyst was higher after the CO pretreatment, than after the hydrogen reduction. The low silica catalyst favored production of high molecular weight products. Methane selectivity in run SA-1532 was only 2.2-2.4 wt%, and that of gaseous (C2- C4) hydrocarbons 10-11 wt%. The extent of secondary reactions (1-olefin hydrogenation, isomerization and/or readsorption) was low on this catalyst. In general, hydrocarbon and olefin selectivities of the Ruhrchemie and the other two UCI catalysts were similar. Methane selectivity in tests with these three catalysts varied between 4.1 and 4.7 wt%, during the first 360 h of testing. 1997 Elsevier Science B.V. All rights reserved.
