Asphaltenes petroleum charge

Bitumens from archaeological asphalts were glassy black pitches that acquired electrical charges when broken into small pieces. They were nearly insoluble in petroleum ether or n-pentane—the classical criterion for the presence of asphaltenes. Because asphaltenes can be formed by oxidizing hot petroleum residues, indications that they were also the end-products of weathering seemed reasonable. 

The charge-transfer nature of donor-acceptor properties of petroleum asphaltenes can influence the processing of petroleum. 

Free radicals or charge transfer Although the ESR spectra of coals and coal derivatives generally are attributed to free radicals, the possibility of charge-transfer interactions, particularly in the cases of coal (19) and coal- (13, 20) and petroleum-derived asphaltenes (21, 22), has been considered. ESR studies have shown that, while charge-transfer interactions may be important in petroleum asphaltenes (21, 22), their role as binding forces in coal-derived asphaltenes is a relatively minor one if existent at all (13). The evidence for these conclusions is based on variable-temperature ESR studies and ESR intensity additivity studies. 

Electrostatic Properties in Nonaqueous Media. Although suspensions most commonly comprise particles dispersed in aqueous media, the petroleum industry contains many examples of particles dispersed in nonaqueous media. Examples include precipitated asphaltenes in oil (see Chapter 8) and mineral solids dispersed in diluted froth in oil sands processing (see Chapter 13). Particles can be electrostatically stabilized in nonaqueous media, although the charging mechanism is different (7, 34). In a recent review Morrison (34) emphasized that many models are... 

The precise mechanism of asphaltene association has not been conclusively established, but hydrogen bonding (66, 95, 96) and the formation of charge-transfer complexes (66) have been cited as the causative mechanisms. Evidence exists that asphaltenes participate in such complexes (97, 98), but the exact chemical or physical manner in which they would form in petroleum is still open to discussion. Intermolecular hydrogen-bonding could also be involved in asphaltene association and may have a significant effect on observed molecular weights (95). 

Jarvie, D. j., Morelos, A., Sassen, R., Chenet, P.-Y. Brame, j. W. 2002. Hydrocarbon charge assessment, Gulf of Mexico rates of oil/gas generation from source roeks and oil asphaltenes. American Association of Petroleum Geologists 2002 Annual Convention, Abstract. 

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