Tricyclic terpenoid derivatives from chemical degradation reactions of asphaltenes

Abstract

Asphaltenes from the Athabasca and Nigerian tar sands were chemically degraded by reducing metal reaction to yield, in each case, non-asphaltenes material (“maltene-I”) that afforded a homologous series of long-chain n-paraffins maximizing at n-C 24 and n-C 26 and featuring a slight even-odd preference. An unusual cycloalkanes distribution pattern characterised by a preponderance of tricyclic terpanes and virtual exclusion of the pentacyclic hopanes was evident from a gas chromatography-mass spectrometric study of the hydrocarbons fraction. The alkanes probably belong to the remnants of the “original oil” which had been retained within the asphaltene matrix and protected from the secondary alteration processes that occurred in the reservoir. There are good prospects that the alkane occurrence may be applied to solve geochemical correlations problems involving highly altered oils and for studying petroleum migration patterns.