Relation of solids fraction in cold jet fuel waxes to molecular species present in the whole fuel

Waxes (n-alkanes) that precipitate in chilled distillate fuel have various levels of solids content, the balance being made up of entrained liquid. Assessing the mass fraction of that entrained liquid is the subject of this paper. Such liquid-loaded precipitate might better be described as a gel. It is not surprising that such gels entrain liquid. Like protein gels for example, these fuel wax precipitate gels may have significant secondary structure that can incorporate the liquid. Relating this secondary structure to the structure of the primary (n-alkane) monomers (and surrounding species they will call solvent) would be a major achievement, because by considering the voids in that secondary structure as filled by liquid fuel, the liquid mass fraction of the precipitate could be obtained. Such theory is not available, and even if it were, it would have to be verified against established experiment. What is offered here is a new approach to the liquid mass fraction, based primarily on macroscopic density but in turn related to concepts such as molecular volume. This paper makes hybridized use of the established experiments and can be used with them to estimate liquid mass fractions, but simultaneously lays foundation for more advanced theory. Two techniquesmore » have been offered to determine the liquid fraction of a given precipitate, both of which involve a tag on the liquid portion. The first one used a noncrystallizing (i.e., not joining in solid solution) component of the fuel (indigenous hydrocarbon) as the tag indicated by gas chromatograph (GC) data. The other method used a more elaborate chromaphoric molecule (spectrophotometrically measured) as the tag, introduced as a dye to the initial fuel sample.« less