A New Type of Aromatic Petroleum Hydrocarbons: Phenyl-Substituted Tri- and Tetracycloaromatics

Analysis of the composition of crude oils from four oil and gas basins by gas chromatography–mass spectrometry has shown that aromatic compounds bearing a phenyl substituent are as typical of oils as the well-known phenanthrenes and chrysenes. Thus, biphenyls are the first member of the series of compounds of this structural type. Unsubstituted and alkyl substituted phenylnaphthalenes, terphenyls, phenylphenanthrenes, and naphthylnaphthalenes have been identified; the smallest set of components of this type (only phenylnaphthalenes) is in Volga–Urals oils. Unlike the case of dispersed organic matter (OM), the main components in oils are alkyl substituted compounds, which can have as long substituents as C 10 alkyls in some cases. The proportion of unsubstituted compounds is small. In all the oils, thermodynamically more stable isomers predominate. The phenylnaphthalene content is close to the content of chrysenes, the proportion of which is about an order of magnitude lower than that of phenanthrenes. In one of the samples, phenylnaphthalenes are about in the same amount as phenanthrenes. The total concentration of terphenyls, phenylphenanthrenes, and naphthylnaphthalenes is usually much lower than the concentration of phenylnaphthalenes. To date, the use of phenyl substituted aromatic compounds in geochemistry has been limited to oil–oil and oil–OM correlations. Studying compounds of this type is important both for more detailed characterization of the composition of aromatic compounds of crude oil and for understanding the processes of oil generation in different environments.