Friday, September 25, 2009

A sobriquet for asphaltene: “cholesterol of petroleum”

While cholesterol promotes clogging of arteries in biological systems, asphaltene can cause clogging of pipes in refining facilities and of pores and channels in geochemical systems such as underground rocks of oil-field reservoirs. Hence, the sobriquet “cholesterol of petroleum” for asphaltenes [1]. These are complex mixtures consisting of aromatic and heterocyclic compounds. Asphaltenes occur in crude oil along with saturated, unsaturated, and aromatic hydrocarbons and hetero-functionalized derivatives thereof.
The “19th-century definition” of asphaltenes, obtained as petroleum fractions, focuses on the solubility of asphaltene constituents in other organic solvents [1]: The asphaltene fraction comprises components that are soluble in toluene but insoluble in n-heptane or n-pentane.
To model and predict asphaltene properties such as as viscosity and aggregation [2] behavior and to optimize petroleum processing operations, a detailed molecular understanding of asphaltene is required. The “cholesterol-like” activity of asphaltene depends on intra- and extramolecular interactions of its molecular constituents.

Keywords: petrochemistry, thermodynamics of petroleum, nickname of petroleum fraction, analogy

[1] Celia Henry Arnaud: Digging Into AsphaltenesMass spectrometry uncovers chemical details of petroleum's most recalcitrant fraction. Chemical & Engineering News September 21, 2009, Volume 87, Number 38, pp. 12-17.
[2] Narve Aske, Harald Kallevik, Einar Eng Johnson and Johan Sjöblom: Asphaltene Aggregates from Crude Oil and Model Systems Studied by High-Pressure NIR Spectroscopy. Energy & Fuels 2002, 16, pp. 1287-1295. DOI: 10.1021/ef020065i.

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