The spread of products produced via Fischer-Tropsch synthesis is influenced by many variables: temperature, feed gas composition, pressure, catalyst type and promoters. Known metals for Fischer-Tropsch catalysis are iron, cobalt, ruthenium, and nickel. Ruthenium has reserves too low for commercial applications and as a result is expensive. Nickel is good for methanation and methane reforming, but iron and cobalt catalysts are the focus of most research for improving catalysts for Fischer-Tropsch synthesis reactions.
Critical objectives for creating more efficient catalysts are improving the useful life, activity and stability of the catalyst so that it may be reused with minimal additional catalyst input. Other general requirements for improving catalysts are high selectivity for desirable products (e.g., low methane and high C5+) and mechanical robustness (e.g., the optimal particle size and density).
Iron-based Fischer-Tropsch Synthesis Catalyst
Iron-based catalysts produce more olefins and oxygenates than cobalt-based catalysts. Iron is also considered more versatile with regards to determining the H2/CO ratio, operational temperatures, pressures and product selectivity. Iron-based Fischer-Tropsch synthesis is able to produce light hydrocarbons for the fuel and chemical industry and heavier hydrocarbons (C35+) for the wax market. Compared to the other metals suitable for Fischer-Tropsch synthesis reactions, iron is a cheap raw material and is on average 250 times less expensive than cobalt. While iron is believed to be more tolerant of poisoning (e.g., sulfur in the synthesis gas), the disadvantage is the iron catalyst can deactivate quickly requiring additional catalyst input.
Synfuels China’s carefully structured iron catalyst (named SynFT-I) for its medium temperature (275°C) slurry-bed Fischer-Tropsch synthesis process has record-breaking hydrocarbon productivity and very low methane selectivity (less than 3% by weight). These iron-based catalysts have high activity and high selectivity for C5+, greater than 92% and frequently more than 96%. The catalyst is easily separated from any waxes and is able to produce 1,200 tons of high quality C3+ products per ton of catalyst utilized.
The highly active nature of SynFT-I lowers the required solid catalyst charge in the slurry-bed reactor. Productivity is high at 1.00 - 1.40 grams product per gram of catalyst per hour. The proprietary Fischer-Tropsch process has a high oil production capability of 7,000 – 10,000 barrels of oil per barrel of catalyst. Superior byproducts include high quality synthetic crudes with very low oxygenates, especially acids. The iron-based catalyst used in the medium temperature slurry-bed Fischer-Tropsch synthesis process has high attrition resistance and is easy to integrate with both coal and gas processes.