Overview of High-Temperature Fischer−Tropsch Gasoline and Diesel Quality

Abstract

As stricter environmental legislative requirements are enforced and the availability of quality crude oil reduces, traditional crude oil refining is continuously being optimized to produce fuels of appropriate quality. Consequently, increasing operating costs put pressure on refining margins, and it remains a challenge to convert all refinery streams into products with acceptable qualities at a reasonable return. Furthermore, energy security and energy diversification together with high crude oil prices have spurred an increased focus on the manufacturing of synthetic fuels and chemicals from gas, coal, and other sources. Fischer−Tropsch (FT), a synthetic technology practiced by Sasol, is a prominent alternative route for the production of synthetic fuels and chemicals. Sasol, in South Africa, uses the high-temperature Fischer−Tropsch (HTFT) process with coal as feedstock to produce a range of synthetic fuels, which includes liquid petroleum gas (LPG), gasoline, kerosene, diesel, heating fuels, and chemicals. The South African production facility at Secunda represents the largest commercial facility of this type in the world. FT fuels are characterized by their very consistent quality. These fuels contain extremely low sulfur levels (<5 ppm), low levels of nitrogen-containing compounds, low polynuclear aromatics, olefins, oxygenates, and in the case of diesel, mostly linear hydrocarbons with a low degree of branching. These fuels can significantly contribute to meeting future energy security and demands. For more than 50 years, nearly 50% of South Africa’s densely populated inland area has been supplied with gasoline and diesel from the Sasol Fischer−Tropsch plants. This paper presents an overview of the current properties of Sasol HTFT synthetic gasoline and diesel.