Comparison of Iron Fischer-Tropsch Catalysts Using on-Line Gas Chromatography

摘要

When comparing catalysts on a spece-time-yield basis, the potassium-promoted iron-cobalt catalyst and the potassium-promoted iron catalyst are the most active. While the iron-manganese catalyst is quite active on a per gram of iron basis, on a per gram of catalyst basis it is only about 20% as active as the potassium-promoted precipitated iron catalyst. The fused iron catalyst is the least active of any catalyst studied, but this catalyst was reduced at 723 exp 0 K (vs 523 exp 0 K for the precipitated iron catalyst). This catalyst can be reduced at 623 exp 0 K in about ten hours, and considering the large effect of reduction temperature on carbiding rate, there is reason to believe the lower reduction temperature will result in a more active catalyst. While the fused iron, iron-cobalt-potassium, and iron-manganese catalysts showed little change in conversion after being placed on-stream, the precipitated iron catalysts, B and C, declined significantly during the first 12 hours and then stabilized. Olefin selectivity as measured by the propylene/propane ratio decreases with time on-stream, although the degree of polymerization changes little during the first 50 hours. The degree of polymerization decreased in the following order: fused iron > K-promoted ppt. Fe > ppt. Fe, Fe-Mn > Fe-Co-K. As far as maximizing gasoline yield is concerned, it appears the Fe-Mn catalyst is to be preferred not only because of the high C sub 5 -C sub 11 selectivity but also because the olefin content is the highest of any catalyst in this study. 15 figures, 3 tables. (ERA citation 08:023219)