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About GTL

Sasol’s gas-to-liquids (GTL) technology is a proven alternative solution to harness Canada’s clean, abundant natural gas resources to produce high-quality transportation fuels and petrochemical feedstocks in a cost-efficient and environmentally conscious way.

What is GTL?

GTL technology converts natural gas into high-quality liquid petroleum products including diesel and naphtha. A GTL facility has integrated value chain opportunities and synergies with upstream and chemicals industries.

GTL diesel is cleaner burning than conventional diesel, with virtually no sulphur or aromatic compounds. Life cycle greenhouse gas emissions are comparable to, or somewhat less than, conventional fuels. The low sulphur content and high cetane number of GTL diesel also make it a desirable blending component with conventional petroleum products.

For a visual demonstration of how cleanly GTL diesel burns compared to conventional diesel, click here.

GTL Production Process

The GTL production process is based on Sasol’s Proprietary Conversion Technology that is comprised of a set of chemical reactions used to produce higher valued products from coal, natural gas or biomass. This technology has been in successful commercial use for more than 50 years.

Natural gas is a mixture of hydrocarbons and other gases including nitrogen, carbon dioxide and sulphur compounds. In the GTL production process, raw natural gas is first purified in a hydrogenation reactor and a washing system. The purified feed gas is then pre-treated by saturation with process water and preheating.

Once the natural gas is pre-treated, the GTL conversion process consists of three main steps:
1. Natural gas reforming: converts lean natural gas (largely methane) mixed together with oxygen into synthesis gas, also known as syn-gas (a mixture of hydrogen and carbon monoxide).
2. Proprietary technology: converts syn-gas into a broad range hydrocarbon stream, also called waxy synfuel. This conversion step is the heart of the GTL process.
3. Product upgrading: upgrades waxy synfuel into high quality synthetic products, such as GTL diesel, GTL naphtha, and, if desired, jet fuel and other high-value products.

GTL-process-chart_Nov15

Natural Gas Reforming

  • Syn-gas for the GTL production process can be produced through various technologies that require mostly steam and air or oxygen.
  • During the reforming process, the hydrocarbon molecules in the natural gas are broken down and stripped of their hydrogen atoms.
  • The carbon atoms together with oxygen (introduced as steam, air or as pure gas) form carbon monoxide molecules.
  • The resulting gas, called synthesis gas or syn-gas, consists of hydrogen, carbon monoxide and carbon dioxide. It is then ready for Sasol’s Proprietary Conversion Process.

Sasol’s Proprietary Conversion Process

  • The purified syn-gas is sent to a slurry phase synthesis reactor.
  • The temperature, pressure and catalyst (cobalt or iron) determine whether a light or waxy synfuel is produced.
  • Through a catalytic chemical process, hydrogen and carbon monoxide – under heat and pressure and with the aid of cobalt or iron-based catalysts – yield linear hydrocarbons, oxygenated hydrocarbons and reaction water.
  • Hydrocarbons from the liquid fuel synthesis reactor are cooled successively in a product recovery plant until most components become liquefied.

Product Separation and Upgrade

  • The liquid products are separated in the final upgrading unit, which often also involves mild hydrocracking to convert higher molecular weight waxes and lubes to naphtha, diesel and liquefied petroleum gas.
  • Since sulphur and other impurities are removed prior to the synthesis of the liquid fuel, the resulting diesel is clear and burns more cleanly than petroleum-derived fuels.