10. Products from Fischer-Tropsch Plants.
(3) Diesel oil. This fraction commonly called “Kogasin” ranging from 150 to 325° C was used either as fuel or raw material for chemical synthesis.
Diesel fuel was prepared by blending FT product with certain low cetane stocks (coal tar, brown coal tar, residueum) to give a 40-45 cetane diesel fuel. According to the season, a lower or higher pourpoint was required. This was obtained by cutting the fractions at various points.
|
Summer |
Winter |
|
|
Diesel fuel |
150°-320° C |
150°-250° C |
|
Cloud point |
-6° C |
-26° C |
|
Pour point |
-12° C |
-34° C |
The FT oil was blended in varying ratios with the taroils according to the required cetane number.
A tar oil of 20 cetane, blended with 100 cetane kogasin, required the following percentage of kogasin:
|
For a 30 cetane blend |
10% |
|
For an 83 cetane blend |
60% |
|
The diesel fraction contains |
10-15% olefines |
|
MP operation gives a slightly better diesel fuel than LP operation. |
|
The olefins boiling in the diesel or kogasin range are of great value as charging stock to certain syntheses. The preferred compound is the dolefine (terminal double bond). In general, the C9-C11 olefines were used for polymerization to synthetic lube oil. The olefine content could be increased by a mild thermal cracking to 60-70% olefins. It was hoped, that the “Kreislauf” operation would produce this concentration in one step.
The C11-C17 olefines were used in the oxosynthesis. (See Section 7 of this report.) here again it was hoped that the Kreislauf would produce fractions sufficiently rich in olefins to be fed directly to the synthesis without previous concentration.