Effect of Dispersant on Asphaltene Suspension Dynamics: Aggregation and Sedimentation

Abstract

When oil is mixed with light alkanes, asphaltenes can precipitate out of oil solutions in a multistep process that involves the formation of nano-and colloidal scale particles, the aggregation of asphaltene colloids, and their eventual sedimentation. Amphiphilic dispersants can greatly affect this process. The mechanism of the dispersant action in colloidal asphaltene suspensions in heptane has been shown through previous work to be due in part to a reduction in the size of the colloidal asphaltene particles with the addition of dispersant. However, previous studies of the sedimentation behavior have also revealed evidence of aggregation processes in the colloidal asphaltenes in heptane that has yet to be investigated fully. We investigate the effect of dispersants on this aggregation behavior through the use of dynamic light scattering, showing that both the amount of dispersant as well as the amount of heptane dilution can affect the onset and extent of aggregation in colloidal asphaltene suspensions. The light scattering results match well with those obtained through the macroscopic sedimentation experiments.

Use of Asphaltene Stabilizers for the Production of Very Low Sulphur Fuel Oil

“…Dispersing additives are used as stabilizers for marine fuels-these are surfactants (both anionic and non-anionic) added to fuels in small quantities, usually no more than 0.1-0.25%, and soluble in them [34][35][36]. These additives change the structure and properties of the formed insoluble associates; similar to natural resins, they have an affinity for polar asphaltene molecules.…”