Characterization of Algerian Hassi-Messaoud asphaltene structure using Raman spectrometry and X-ray diffraction

Asphaltenes derived from Algerian oil wells were characterized by Raman spectrometry to investigate their molecular structures in solid-state. The aromatic sheet diameter (La) was estimated using the integrated intensities of the G and the D1 mode, along with the Tuinstra equation [Tuinstra F, Koenig JL. J Chem Phys 1970;53:1126]. The values obtained for three Algerian Hassi-Messaoud asphaltene samples are on the same order as the literature values and also consistent with the X-ray diffraction results. The Raman spectra corresponding to the G and the D bands can be fitted with Gaussian, Lorentzian, and Gaussian/Lorentzian hybrid functions in a self-consistent manner. A three peak fitting procedure found that the Gaussian/Lorentzian hybrid function with G being Gaussian and D Lorentzian is the best combination. Incorporation of the X-ray data on the height of the crystallite, Lc, gives rise to an estimate of eight asphaltene molecules in each asphaltene aggregate.