The objective of this work was to investigate the mechanism of the inhibition of aggregation of petroleum asphaltenes using new ionic liquids (IL). The ionic liquids conjugate a good solubility in nonpolar environment with strong electron donor-acceptor properties. In this study, 1-propyl boronic acid-3-alkylimidazolium bromides and 1-propenyl-3-alkylimidazolium bromides were tested. A lateral chain containing either the boronic acid or the propenyl moiety was substituted for the classical 1-methyl-3-alkylimidazolium bromide. The boronic acid is a weak acid but a very efficient Lewis acid. It was demonstrated that the presence of the boronic acid moiety enhances interactions between asphaltenes and ionic liquids and limits considerably asphaltene aggregation. The length of the side alkyl chain of the ionic liquid is an important parameter also. The minimum length of eight carbons was necessary to obtain sterical stabilization of IL-asphaltene complexes.

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The objective of this work was to separate and study a least stable fraction of Hassi−Messaoud asphaltenes that flocculate during oil transport and storage. The unstable fraction was studied by consecutive fractioning with solvents differing in polarity. A correlation between structural parameters of asphaltenes and the flocculation onset was established. It was demonstrated that the spontaneously flocculating part of asphaltenes is composed of relatively small molecules that are less aromatic and contain more heteroatoms than more stable asphaltenes. The length of the side aliphatic chain was shown to be an important parameter influencing the flocculation onset.

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Polar fractions of Hassi-Messaoud asphaltenes were obtained by two different extraction/precipitation procedures. Properties of these fractions were studied using elemental analysis, LDI-TOF mass spectroscopy, and solid state 13 C NMR. The aggregation and the flocculation onset of polar fractions were determined. It was demonstrated that the most polar fraction of asphaltenes that is soluble in highly polar solvents, such as N-methyl pyrrolidone and nonsoluble in mildly polar or nonpolar solvents is composed of small molecules, containing a high oxygen ratio. This fraction plays an important role in asphaltene aggregate formation. The understanding of this role would be helpful for designing new antiflocculation agents.

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