Production of a Full Range of Synthetic Paraffin Wax Products Based on the Fischer-Tropsch Process and Consecutive Modification Technologies

Publication Summary

The Fischer-Tropsch (FT) process allows the conversion of synthesis gas, i.e. a mix of CO and H2, to a variety of paraffin hydrocarbons with chain lengths between C1 and C100+. The molecules above C17 are solid paraffin waxes and have the advantage to be virtually free of aromatics, sulphur and nitrogen compounds. This paper shows that combinations of known and emerging fractionation and modification technologies allow the production of a vast range of paraffin wax products which cover virtually all current petroleum wax applications. Moreover these technologies open up possibilities for tailor made products with new properties.

Country	Germany
Language	English (South Africa)
Related Person(s)	(AUTHOR)  Dr Thorsten Butz (AUTHOR)  Mr John Beigley (ATTORNEY)  Madelein Kleyn
Copyright	Copyright Reserved. © Sasol Wax GmbH, Germany, 2007 and Sasol Chemical Industries Limited, South Africa, 2007

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Production of a Full Range of Synthetic Paraffin Wax Products Based on the Fischer- Tropsch Process and Consecutive Modification Technologies

Dr. Thorsten Butz, Sasol Wax GmbH, Hamburg, Germany

John Beigley, Sasol Wax (South Africa), Sasolburg

Abstract The Fischer$Tropsch (FT) process allows the conversion of synthesis gas, i.e. a mix of CO and H₂, to a variety of paraffin hydrocarbons with chain lengths between C₁ and C₁₀₀₊. The molecules above C₁₇ are solid paraffin waxes and have the advantage to be virtually free of aromatics, sulphur and nitrogen compounds. This paper shows that combinations of known and emerging fractionation and modification technologies allow the production of a vast range of paraffin wax products which cover virtually all current petroleum wax applications. Moreover these technologies open up possibilities for tailor made products with new properties.
1 Introduction - FT-Wax Production The FT$process was developed in 1925 by F. Fischer and H. Tropsch. Because of changing conditions and requirements over the last eight decades a variety of production processes have been developed as documented by the publication of Steynberg and Dry ¹.

The overall processes, whereby synthesis gas, derived from coal, gas or biomass is converted to wax and further hydrotreated to produce middle distillate products and lubricant base oils are known as the coal to liquids (CTL)-, gas to liquids (GTL)-, or biomass to liquids (BTL) processes. Alternatively, defined wax fractions can be cut from the raw FT product and after optional processing steps be utilized as valuable waxes. The first step of the process is the generation of synthesis gas (CO/H₂) by the partially oxidizing gasification of coal or other carbonaceous materials such as biomass or the reforming of natural gas.
In the exothermic FT$process one mole of CO reacts with two moles of H₂ to yield a hydrocarbon chain extension ($CH₂$). The oxygen from the CO is released as product water: CO + 2H₂ → $CH₂ $ + H₂O
:H = $165 kJ/mol
The reaction implies a H₂/CO ratio of at least 2 for the synthesis of the hydrocarbons. When the ratio is lower it can be adjusted in the reactor with the catalytic Water$Gas Shift (WGS) reaction:

CO + H₂O → CO₂ + H₂
:H = $42 kJ/mol
When catalysts with WGS activity are used the water produced in the reaction can react with CO to form additional H₂. In this case a minimal H₂/CO ratio of 0.5 is required and the oxygen from the CO is released as CO₂:
2CO + H₂ → $ CH₂ $ + CO₂
:H = $204 kJ/mol

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The ability to remove sulphur contents by conventional desulphurizing processes in the gas phase prevents poisoning of the FT$catalyst and ensures that final products are sulphur free. The reaction yields mainly aliphatic straight$chain hydrocarbons (C_xH_y). Besides these straight$chain hydrocarbons, branched hydrocarbons,...

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