Abstract
The study of asphaltene colloidal properties is motivated by their propensity to aggregate, flocculate, precipitate, adsorb onto interfaces and, hence, pose considerable challenges for the petroleum industry. Asphaltenes are defined as the toluene (or benzene) soluble, yet n‐heptane (or n‐pentane) insoluble, portion of crude oil. The “solubility class” definition of asphaltenes generates a broad distribution of molecular structures that vary greatly among crude sources. Asphaltenes are generally characterized by fused ring aromaticity, small aliphatic side chains, and polar heteroatom‐containing functional groups (e.g., carboxylic acids, carbonyl, phenol, pyrroles, and pyridines) capable of donating or accepting protons inter‐ and intra‐molecularly. Molar H/C ratios between 1.0–1.2 and N, S, and O content of a few weight percent suggest that the asphaltene backbone mostly contains fused aromatic carbon interspersed with occasional polar functional groups. The most plausible mechanisms of asphaltene aggregation involve dispersion interactions between aromatic rings, polar and hydrogen bonding interactions between heteroatoms, and other charge transfer interactions. Understanding asphaltene chemistry and the fundamental mechanisms of colloid formation has been the driving force behind much petroleum research of the last half‐century.
Published Version
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