Coal was first directly liquefied in the early twentieth century.
In 1925, Franz Fischer and Hans Tropsch pioneered a new, indirect method, which bears their names even today – Fischer-Tropsch synthesis.
This process uses synthesis gas – a mixture of carbon monoxide and hydrogen – as the feedstock gas. Synthesis gas can be produced from coal or natural gas (and also from oil fractions such as heavy oil).
After a simple purification process, synthesis gas is completely sulphur-free. Consequently, the fuels produced by Fischer-Tropsch synthesis are also completely free from sulfuric impurities.
As a result of high crude oil and natural gas prices, coal is becoming increasingly important as a raw material in synthesis gas plants. As such, The Linde Group is constructing a gas purification pilot plant in China for Shell.
These plants are an important building block for future CTL (coal-to-liquids) fuel projects.
