(228f) Sans Characterization Of Emulsion Film Thickness And Composition Of Asphaltene-Stabilized Emulsions

Asphaltenes constitute the most chemically complex and poorly understood molecular species in heavy oils. They are known to self assemble at the nanoscale to form molecular aggregates whose surface activity is responsible for precipitation, deposition, stabilization of emulsions, and other production and processing difficulties. Small angle neutron scattering (SANS) is a powerful tool for probing the nanostructural properties of asphaltenic aggregates and films. Here, we report the use of SANS to elucidate the film thickness and film composition of water-in-oil emulsions in which the film is comprised of asphaltenes and solvent. By selectively deuterating both the external oil phase as well as the discrete water phase, we are able to definitively assign film thickness and film scattering length density in such a way as to uniquely determine film composition. We have verified this composition and thickness by independently measuring asphaltene film mass gravimetrically in emulsions for which we have measured drop size distribution and total water content. The typical film thickness in asphaltene emulsions is approximately 80-150 Å (8-15 nm). The composition of the film is typically 20-50% (w/w) asphaltene, with the remainder comprised of solvent. We have determined that asphaltene density typically determines emulsion stability, as measured in independent tests. Finally, we report here the impact of adding acidic asphaltenic mimics, specifically anthracene carboxylic acid, on film thickness and density.