A study of heavy oil fractions by Fourier-transform near-infrared Raman spectroscopy

Oil fractions with a boiling-point step size of 20°C (300 to 560°C) for six different crude oils of Western Siberia have been studied by Fourier-transform Raman and Fourier-transform IR spectroscopy. Weak bands have been more clearly revealed, previously noninterpreted bands have been attributed, and corrections to the published assignment of their characteristic Raman bands have been made. The capabilities and the informative value of the method have been shown, as applied to the determination of nitrogen heterocycles and the ratios between mono-, bi-, tri-, and polycyclic aromatic hydrocarbons or between CH2 and CH3 groups. The true band envelopes of polycyclic aromatic hydrocarbons have been found with the use of corrected difference Fourier-transform Raman spectroscopy at different temperature increments, and the tendency toward their approach to the Raman band envelopes of disordered carbon (in particular, for the case of sedimentary rocks) has been shown. A complementary application of Fourier-transform Raman and Fourier-transform near-infrared absorption spectroscopy to the monitoring of industrial streams and processes in the near-infrared region through integrated fiber-optic networks has been suggested.