FischerTropsch

Fischer–Tropsch synthesis is a set of chemical reactions that convert synthesis gas, a mixture of carbon monoxide and hydrogen, into a broad range of hydrocarbons. It was developed by Franz Fischer and Hans Tropsch in the 1920s in Germany and has since underpinned coal- and gas-to-liquids technologies. The process remains a focal point in the development of alternative liquid fuels and depends on catalytic conversion of syngas into longer-chain hydrocarbons.

Syngas can be produced from a variety of feedstocks, including coal, natural gas, or biomass, and is processed over catalysts such as iron, cobalt, or, less commonly, ruthenium. Conditions are typically high temperature and high pressure, with temperatures ranging roughly from 150 to 350 C and pressures from 1 to 20 megapascals. Iron catalysts can operate with lower H2/CO ratios and promote the water-gas shift reaction, while cobalt catalysts generally favor the growth of longer hydrocarbon chains and paraffinic products. The overall reaction is highly exothermic and requires careful heat management.

The products of Fischer–Tropsch synthesis span a wide range, from methane to long-chain paraffins and waxes. The product slate can be directed toward gasoline, diesel, jet fuel, or waxes, depending on catalyst choice and operating conditions. Because the mixture often needs upgrading, downstream hydrocracking, hydroisomerization, and refinery blending are common to meet fuel specifications.

Industrial significance and challenges: Fischer–Tropsch technologies are used in coal- and gas-to-liquids plants worldwide, most notably by Sasol in South Africa and various GTL projects. Benefits include the ability to convert abundant feedstocks into cleaner, sulfur-free fuels, but challenges include catalyst deactivation from coking and sulfur poisoning, energy intensity, and CO2 emissions without carbon capture. Advances in catalysts and reactor design continue to improve selectivity and efficiency.