What are the effects of processing conditions on the interfacial viscoelasticity of asphaltene interfaces?

Stable crude/water emulsions that form during processing result in the formation of the rag layer, which is a major detriment to petroleum processing. The stability of the rag layer is determined by drop resistance to coalescence. Interfacial asphaltenes and other surface active components create viscoelastic interfaces that inhibit coalescence, resulting in stable rag layers. Although, there have been efforts into studying asphaltene interfaces, there are still many open questions regarding their behavior. In particular, the formation pathway of the asphaltene interface on final interfacial elasticity.

We have examined how large amplitude dilatational strains change the interfacial shear viscoelasticity of asphaltene interfaces. We see changes in viscoelastic moduli that depends on how the interface was formed: adsorption, larger single compression, or multistep small compressions. Interfaces that adsorb show larger viscoelastic moduli than single step compression interfaces, but smaller values than multistep compression. Small interfacial expansions result in minimal changes of the interface, but large expansions significantly disrupt surface structure creating weak interfaces. These results shed important light on how processing of these interfaces may affect rag layers.