Seven gas oil (GO) cuts from the same atmospheric petroleum
residuum were obtained by molecular distillation at final temperatures
of 490.0 and 503.2 °C (medium GO), 522.5 and 549.5 °C (heavy
GO), and 583.7, 622.4, and 662.2 °C (extra heavy GO). The detailed
chemical composition of these samples was investigated using comprehensive
two-dimensional gas chromatography with time-of-flight mass spectrometry
(GC × GC–TOFMS) and electrospray ionization ultrahigh-resolution
and -accuracy Fourier transform ion cyclotron resonance mass spectrometry
(ESI FT-ICR MS). Many compound classes were identified by GC ×
GC–TOFMS, such as tri-, tetra-, and pentacyclic terpanes, steranes,
and secohopanes; several polycyclic aromatic hydrocarbons (PAHs),
such as fluorene, phenanthrene, pyrene, and benzo[g,h,i]perylene; sulfur compounds,
e.g., alkylbenzothiophenes, alkyldibenzothiophenes, and alkylbenzonaphthothiophenes;
and alkylphenols. With ESI FT-ICR MS in both the positive- and negative-ion
modes, many polar components that cannot be directly characterized
via GC were identified. These included quinolines, benzoacridines,
carbazoles, benzocarbazoles, thiophenequinolines, and also furanacridines
and trends in carbon number and unsaturation as measured by the double-bond
equivalent number (DBE) were monitored. Comprehensive characterization
of the chemical composition was therefore possible using these two
powerful and complementary techniques, enabling detailed monitoring
of the complex chemical composition of GO cuts and its variation as
a function of distillation temperatures.
