title: Effect of surfactants on interfacial films and stability of water-in-oil emulsions stabilized by asphaltenes.
abstract: The effect of additives on asphaltene interfacial films and emulsion stability was analyzed through the change in film properties. Surface pressure isotherms were measured at 23°C for model interfaces between aqueous surfactant solutions and asphaltenes dissolved in toluene and heptane-toluene mixtures. Compressibility, crumpling film ratio and surface pressure were determined from the surface pressure isotherms. The stability of water-in-oil emulsions was determined for the same systems based on the proportion of unresolved emulsified water after repeated treatment involving heating at 60°C and centrifugation. Experimental variables included concentration of asphaltenes (5 and 10 kg/m(3)), concentration and type of surfactant (Aerosol OT, nonylphenol ethoxylates, polypropylene oxide block-copolymer, dodecylbenzene sulfonic acids, dodecylbenzene sulfonic acid-polymer blend, diisopropyl naphthalene sulfonic acid, and sodium naphthenate) and aging time (from 10 min to 4 h). Additives were found to have two opposing effects on film properties and emulsion stability: (1) decreasing or eliminating the crumpling ratio which destabilized emulsions and (2) decreasing interfacial tension which enhanced emulsion stability. A stability parameter was defined to include both the crumpling ratio and interfacial tension and provided a consistent correlation for the percent residual emulsified water.
authors.affiliation: Chemical & Petroleum Engineering, University of Calgary, 2500 University Drive NW, Calgary, Alberta, Canada T2N 1N4.
authors.forename: D P
authors.initials: DP
authors.lastname: Ortiz
authors.forename: E N
authors.initials: EN
authors.lastname: Baydak
authors.forename: H W
authors.initials: HW
authors.lastname: Yarranton
mesh_terms: D004655:Emulsions / Q000737:chemistry; D006841:Hydrocarbons, Aromatic / Q000737:chemistry*; D008567:Membranes, Artificial; D015394:Molecular Structure; D009821:Oils / Q000737:chemistry*; D013499:Surface Properties; D013501:Surface-Active Agents / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
chemical_list: D004655:Emulsions; D006841:Hydrocarbons, Aromatic; D008567:Membranes, Artificial; D009821:Oils; D013501:Surface-Active Agents; D014867:Water