Gas to liquid refinery. Exterior of the PetroSA GTL (Gas to Liquids) Refinery, Mossel Bay, Western Cape, South Africa. GTL is a process used to convert natural gas, or other gas hydrocarbons, in to liquid hydrocarbon fuels such as gasoline or diesel. This refinery was commissioned in 1992 as the world's first GTL refinery and remains the third largest GTL refinery among the five now operating worldwide (as of 2016). The refinery converts natural methane-rich gas into ultra-clean low-sulphur, low-aromatic synthetic fuels and high value products. The final products include unleaded petrol, kerosene (paraffin), diesel, propane, liquid oxygen and nitrogen, distillates, eco-fuels, process oils and alcohols.