Catagenesis and composition of petroleum: origin of n-alkanes and isoalkanes in petroleum crudes

Journal Article · Tue Sep 01 00:00:00 EDT 1987 · Geochim. Cosmochim. Acta; (United States)

DOI:https://doi.org/10.1016/0016-7037(87)90296-1· OSTI ID:5212424

Kissin, Y V

Distribution of n-alkanes and isoalkanes in ca. 50 petroleum crudes have been examined by the gas chromatography. Molar distributions of n-alkanes with respect to their c atom numbers in the majority of crudes follow the exponential law, which signifies a random, chemical nature of n-alkane-generating processes occurring in the catagenesis stage of petroleum maturation. Similar distributions of n-alkanes were found in the products of mild thermolysis of heavy n-alkanes. Isoalkanes represent a major, 10-25%, petroleum component. The principal types of isoalkanes in crudes are monomethyl-branched, with the branches randomly positioned in the chains, and dimethyl-branched with one of the methyl groups predominantly in the second position in the chains. Thermolysis studies of individual n-alkanes, alkanoic acids, and esters in the presence of various minerals provided an explanation of the n-alkane and isoalkane distributions. Selected heavy n-alkanes are initially formed in decarboxylation reactions of heavy n-alkanoic acids and esters. Extensive thermocracking produces mixtures of lighter n-alkanes and ..cap alpha..-olefins. The olefins, in the presence of acidic clays, are converted in cationic reactions into mixtures of predominantly mono- and dimethyl-branched isoalkanes.

• Research Organization: Gulf Research and Development Co., Pittsburgh, PA (USA)
• OSTI ID: 5212424
• Journal Information: Geochim. Cosmochim. Acta; (United States), Journal Name: Geochim. Cosmochim. Acta; (United States) Vol. 51:9; ISSN GCACA
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
023000* -- Petroleum-- Properties & Composition
58 GEOSCIENCES
580400 -- Geochemistry-- (-1989)
ALKANES
CATAGENESIS
CHEMICAL ANALYSIS
CHEMICAL COMPOSITION
CHEMISTRY
CHROMATOGRAPHY
ENERGY SOURCES
FOSSIL FUELS
FUELS
GAS CHROMATOGRAPHY
GEOCHEMISTRY
HYDROCARBONS
MATURATION
MOLECULAR STRUCTURE
ORGANIC COMPOUNDS
PETROLEUM
SEPARATION PROCESSES
STRUCTURAL CHEMICAL ANALYSIS