A New Reaction Controlling the Composition of Oils: Hydrogenation of Aromatic Hydrocarbons

Abstract

Analysis of the composition of n-alkyl-substituted monocyclic compounds (n-alkylcyclohexanes, n-alkylcyclopentanes, and n-alkylbenzenes) of Tatarstan oils made it possible to prove that the composition of the oils was controlled by still another reaction, whose evidence has never before been identified in rocks: the hydrogenation reaction of aromatic hydrocarbons. It has been directly proven that n-alkylcyclohexanes of the oils were partially formed from n-alkylbenzenes of these oils. Therewith catalysts for the hydrogenation of aromatic hydrocarbons known in organic chemistry either are not present in any noticeable quantities in oils (as are platinum-group metals in the Earth’s crust) or are inactive in natural environments, and hence, it is not possible to indicate any natural catalyst for this reaction. Thus, the discovery of this reaction demonstrates the incompleteness of our understanding of the catalysts involved in the formation of the composition of oils. Literature data indicate that Tatarstan is not the only region in whose oils this reaction occurs. It is demonstrated that the oils should have occurred during their hydrogenation under conditions radically different from those that occurred during the formation of their main components (acid catalysts occurring during the first stage and absent during the second one). It follows that the hydrogenation reaction of aromatic hydrocarbons in Tatarstan oils operated during the later stages of their evolution, when the main composition of the oils had already been formed. It seems to be reasonable to assume that hydrogenation took place after the migration of oil from the source rock, i.e., this reaction operated either during oil migration routes or in the reservoir.