In this paper, a quick and direct method has been developed for the quantitative estimation of
total aromatics and saturates in a vacuum gas oil (VGO) fractions boiling range (370−560 °C),
using 1H NMR spectroscopic techniques. The method is based on the estimation of the average
alkyl chain length of substituents on aromatics and the relative group molecular weight of
aromatics and saturates. The total aromatics are estimated from the derived equation, which
takes into account the relative distribution of CH
n
(n = 0, 1, 2, 3) groups of aromatics substituents
and saturates. The exact assignment of aromatics substituents of α-CH
n
(n = 1, 2, 3) has been
performed by the application of 1H/13C multipulse NMR techniques, such as DEPT-135 and 2D
HSQC (edited) (heteronuclear single quantum coherence). The results obtained for several VGO
samples from different sources have been in close agreement with those from the open
chromatography method (ASTM D-2549-91) and the thin-layer chromatography−flame ionization
detection (TLC−FID) method (IP-469).