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10. Products from Fischer-Tropsch Plants.

(4) Wax. Waxes are the highest boiling product from FT operations. It was for that reason that MP operations became of interest, since they yield somewhat more wax. The wax is obtained as bottom product in the distillation of primary products and by extraction of the catalyst (intermediate regeneration).

The waxes contain practically no olefins. Wax from MP operation has considerably less Isoparaffins compared with LP wax (less than 50% versus 40%). This is an important property, when the wax is to be used for oxidation to fatty acid, since the soaps derived from these acids were found to have superior odor. It is also of importance in the manufacture of lube oil by cracking and Al Cl₃ polymerization, straight chains being preferred. The wax is usually fractionated, with the lower melting part going to cracking (for lube oil synthesis) and the high melting point waxes (100° C) being sold as premium products.

Considerable work was done on the structure of FT waxes. An attempt was made to isolate pure compounds from the hard waxes by fractional crystallization in different solvents. The wax, a product obtained by extraction of spent catalyst from LP operation, was analyzed and the various fractions checked for melting point, molecular weight and other properties.

The following data were given:

It was found that the synthesis produced all alipathic paraffins from C₁ up to C₇₅. The “Hard Wax” included the range from C₂₅ to C₇₅. Indications were that some still longer chains were present. These higher fractions were hard brittle products which could not be scratched with a finger nail.

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