Synthetic Liquid Fuel

combustible liquids produced synthetically and used in internal combustion engines. Synthetic liquid fuels are prepared from a mixture of CO and H₂ obtained from natural gas and coal; the process is carried out at elevated temperatures and pressures in the presence of such catalysts as Ni, Co, and Fe (Fischer-Tropsch process). Depending on the conditions of the process, the synthetic fuel will contain different amounts of paraffins and olefins, mostly of normal structure.

Synthetic fuels were first obtained in significant quantities in Germany during World War II to compensate for a shortage of petroleum. The synthesis was carried out at a temperature of 170°-200°C and a pressure of 0.1–1 meganewton per sq m (1–10 atmospheres) with a cobalt-based catalyst. The process yielded gasoline (kogasin I) with an octane number of 40–55, high-quality diesel fuel (kogasin II) with a cetane number of 80–100, and solid paraffin. It was found that the addition of 0.8 milliliter of tetraethyllead per liter of gasoline increased the octane number from 55 to 74. A synthesis with an iron-based catalyst was carried out at a temperature of 220°C and higher and a pressure of 1–3 meganewtons per sq m (10–30 atmospheres). The gasoline obtained under these conditions contained 60–70 percent olefins with normal and branched structures; the octane number was 75–78.

The production of synthetic liquid fuel from CO and H₂ has not undergone subsequent development because of the high cost of the process and the low efficiency of the catalysts. High-octane antiknock additives, however, are produced synthetically. These additives include isooctane, obtained by the catalytic alkylation of isobutane with butylènes, and polymer gasoline, a product of the catalytic polymerization of propane-propylene fractions.