(535e) Coalescence Inhibition through Asphaltene Adsorption

Asphaltenes are complex polar components of heavy oils and are only marginally stable in organic solvents. Because of this marginal solubility, they have a propensity to adsorb onto oil/water interfaces to form viscoelastic layers. This can result in a strong stabilization of water-in-oil emulsions that cause difficulties in refining operations. In this paper we examine the coalescence process of water droplets in the presence of asphaltenes using a newly developed instrument where the thickness of thin, draining films can be measured in space and time. Using this instrument, thin film thickness, internal droplet pressure and coalescence times can be measured. These results are further compared against measurements of the interfacial shear viscoelasticity of asphaltene-laden interfaces. In addition to asphaltene concentration in a model hydrocarbon (toluene is used), the aging times of the interface was varied. As expected, both asphaltene concentration and aging time are found to strongly affect coalescence dynamics. In addition to reporting on water droplet coalescence dynamics, we found that contact of water against asphaltene/toluene solutions induced the production of a remarkable â??microemulsionâ? where micron-sized water droplets, stabilized by asphaltenes, spontaneously appeared.