Composition-property relations for jet and diesel fuels of variable boiling range

Simple linear relations between properties and composition are developed for jet and diesel fuels of different boiling ranges. Composition is defined in terms of two parameters readily determined by 13C n.m.r. spectroscopy, namely Cn, the fraction of n-alkyl carbon, and Car, the fraction of aromatic carbon. The boiling distribution of the fuels is defined, using gas chromatography, in terms of two parameters, T10 and T90, the temperatures at which 10 and 90 wt% of the fuel has vaporized. Relations of the form P = a1Cn + a2Car + Σ biTi + k, where P is the property value and a1, a2, biand k are constants determined by multiple linear regression, are valid for jet fuels with initial boiling points in the range 150–190°C and final boiling points in the range 230–250°C, and for diesel fuels with initial and final boiling point ranges of 190–230°C and 320–370°C respectively. Properties investigated include smoke point, aromatics content, hydrogen content, density and freezing point for jet fuels, and cloud point, pour point, aniline point, hydrogen content, density, cetane index and cetane number for diesel fuels. Except for the low-temperature properties (jet fuel freezing point and diesel fuel cloud and pour points), an even simpler model of the form previously developed for jet and diesel fuels of fixed boiling range, viz. P = a1Cn + a2Car + k are also adequate.