Gas chromatography-mass spectrometry
Heavy crude oils
Springer Online Journal Archives 1860-2000
Chemistry and Pharmacology
Summary Various atmospheric residues of crude oil [Boscan (Venezuela), Maya (Mexico), Kirkouk (Iraq), Safanyia (Saudi Arabia), Arabian Light (Algeria)] have been analyzed by GC/MS coupling after “transalkylation”. The transalkylation of atmospheric residues from the aromatic matrix to a light aromatic acceptor was performed after optimization of the reaction, using an acidic catalyst/light aromatic acceptor couple: AlBr3 slightly hydrated/benzene. The reaction time was about four hours and the temperature 60°C. These conditions allow the best compromise between a maximal transfer of alkyl chains and their minimal degradation, which is necessary in an analytical study. The results presented here demonstrate that heavy oil residues from different sources give qualitatively similar GC chromatograms, and that only the amounts of phenylalkanes obtained after transalkylation may vary. Under these conditions, the transfer yields of alkyl chains (defined as the mass of alkylated light aromatics obtained from 100g of oil fraction treated) are significantly different and are thus proposed as a new characteristic of heavy crude oil fractions and of petroleum residues. A thorough quantiative study of the phenyl alkanes identified indicates that in every residue, the amount of compounds containing ramified alkyl chains is constant, whereas linear alkyl chain amounts were observed to vary. Yields of diphenylalkanes are quite different for each residue. This result suggests that the reticulation of the aromatic matrix is a function of the nature of the oil residue.
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