Elements of
Chemical Reaction Engineering
6th Edition



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Essentials of
Chemical Reaction Engineering
Second Edition

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Chapter 1: Mole Balances

Fischer-Tropsch Reaction

The Fischer-Tropsch reaction is used to convert the synthesis of gas into hydrocarbons. The reaction can be written in a simplified form as follows:

CO + 2H2 ----> -CH2- + H2O

This reaction was discovered in the 1920's and has been used by Sasol for the production of liquid fuels and chemicals from synthesis gas for over forty years. The hydrocarbons are synthesized by a chain growth process, with the length of the chain dependent on the catalyst selectivity and reaction conditions.

Two types of Fischer-Tropsch conversion steps have been developed and operated by Sasol. One makes use of the Slurry Phase Reactor to produce waxes and distillate fuels, while the other uses the Advanced Synthol Reactor mainly to produce light olefins and gasoline fractions.

Preheated synthesis gas is fed to the bottom of the reactor, where it is distributed into the slurry consisting of liquid wax and catalyst particles. As the gas bubbles upwards through the slurry, it diffuses into the slurry and is converted into more wax by the Fischer-Tropsch reaction. The heat given off by the reaction is removed using cooling coils inside the Slurry Phase Reactor that generate steam. The product wax is separated from the slurry containing the catalyst particles in a proprietary process. The lighter, more volatile fractions leave in a gas stream from the top of the reactor. The gas stream is cooled to recover the lighter cuts and water. The hydrocarbon streams are sent to the product upgrading unit, while the water stream is treated in the water recovery unit.


 

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