A Statistical Examination of the Effect of Composition on the Freezing Points of Hydro-Carbon Mixtures.

Abstract : A series of three statistically designed experiments was run to study the effect of composition on the freezing point of model hydrocarbon fuels. For each experiment, regression equations were derived to describe the effect of composition on freezing point for various mixtures of n-alkanes and other hydrocarbons. These experiments showed that the higher n-alkanes and the interactions among them play an important role in freezing point. The n-alkanes C-16, C-15, and C-14 (in that order) had a strong positive effect (raised the freezing point). The n-alkanes C-12 and C-13 also had strong effects, with C-12 and C-13 in combination showing strong negative effects. However, the magnitude and direction (positive or negative) of the C-12 and C-13 effects (individually and in combination) were greatly dependent on the concentration of C-16. In general C-12 and C-13 individually had a positive effect when the C-16 mole fraction as small (less than 1.67 mol-%) but a negative effect in the presence of higher C-16 concentrations. The n-alkanes C-10 and C-11 had negligible effects. These behaviors were consistent with the results of previous NRL studies.