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The main objective of this studywas to provide novel insightsinto the mechanism of asphalteneaggregation in toluene/heptane (Heptol) solutions and the effect ofalkylphenols on asphaltene dispersion through the integration of advancedexperimental and modeling methods. High-resolution transmission electronmicroscope (HRTEM) images revealed that the onset of asphaltene flocculationoccurs near a toluene/heptane volume ratio of 70:30 and that flocculatesare well below 1 μm in size. To assess the impact of alkylphenolson asphaltene aggregation, octylphenol (OP) and dodecylphenol (DP)were evaluated by impedance analysis based on their ability to delaytheprecipitation onset and to reduce the size of nonflocculated asphalteneaggregates in 80:20 toluene/heptane solutions. Although a longer dispersantchain length did not affect the precipitation onset, it reduced thesize of the aggregates. Molecular dynamics simulations were then performedto understand the mechanism of interaction between a model asphalteneand OP in heptane. OP molecules saturated the H-bonding sites of asphaltenesand prevented them from interacting laterally between themselves.This explained why OP favored the formation of flocculates with filamentaryrather than globular structures, which were clearly observed by HRTEM.Although OP proved to be an effective dispersant, its effectivenesswas hindered by its self-association and the fact that it interactedat the periphery of asphaltenes, leaving their aromatic cores uncovered. [ABSTRACT FROM AUTHOR]