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Abstract
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The
production of diesel fuel via catalytic hydrocracking of Fischer - Tropsch
(FT) wax is one of the most promising industrial processes for the near
future. Large amounts of valuable, high quality diesel fuel with cetane
numbers >75, low nitrogen, sulfur and aromatic contents can be produced
from this process. The gas chromatographic analysis of the feedstock and the
diesel fuel is of high importance, since the composition of both determines
the diesel selectivity and quality. However, the analysis is very challenging
due to the high final boiling point of waxes and the complex mixture of n -
and iso - paraffins, olefins and oxygenates. Furthermore, the high
concentration of linear and branched paraffins in the diesel fuels makes a
proper separation difficult during analysis. To overcome these challenges,
tailor - made 1D and 2D gas chromatographic (GC) methods were combined and
applied for the analysis.
Different
hydrocracking feedstocks such as FT wax and vacuum gas oil (VGO) were
analyzed using 1D and 2D GC techniques in order to demonstrate the influence
of their composition on the diesel properties. Comprehensive analysis of the
final diesel product was performed using GC×GC - FID and GC×GC - MS
techniques. While the VGO contains a mixture of aromatics and linear,
branched or cyclic hydrocarbons, it was found that the FT waxes mainly
contain linear paraffins, and that no aromatic or cyclic (naphthenic)
compounds were present. Thus, hydro - cracking of the FT waxes leads to
diesel fuel with a high cetane number that mainly is deter - mined by the
ratio of iso - /n - paraffins and extremely low aromatic content.
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