Silica aerogel supported catalysts for Fischer-Tropsch synthesis

Cobalt catalysts supported on silica acrogel have been prepared using sol-gel chemistry followed by drying under supercritical ethanol conditions. Three different loadings of cobalt were synthesized: 2, 6, and 10% by weight. Transmission electron micrographs indicate that the metallic cobalt exists as discrete particles 50-70 nm in diameter for the 2 and 6% loadings. The 10% catalyst shows long needles of cobalt. BET and BJH measurements indicate that the catalysts retain the silica aerogel properties of high surface area (similar to800 m(2)/g), large pore volume (similar to5 cm(3)/g), and an average pore diameter in the mesoporous regime (similar to25 nm). The catalysts were evaluated for Fischer-Tropsch activity in a laboratory-scale packed bed reactor. All three catalysts were active with the 10% Co catalyst achieving more than 20% CO conversion which corresponds to a rate of 1.53 g CO per g-cat per hour. The catalysts were selective for the C10+ hydrocarbons with more than 50% of the carbon contained within this fraction. A significant portion of the C-9-C-15 hydrocarbon product was observed as l-olefins which reflects the enhanced mass transport within the very porous aerogel support. (C) 2004 Elsevier B.V. All rights reserved.