The adsorption of Athabasca and Cold Lake C 7 -asphaltenes on stainless steel (304L), iron, and aluminum powders was measured using UV-vis spectrophotometry. The effects of resins, temperature, and n-heptane-to-toluene ratio were also investigated. In all cases, Langmuir (type I) isotherms were observed, indicating that asphaltenes saturated the available surface area for adsorption. The saturation adsorptions of the asphaltenes on metals (0.25-2.7 mg/m 2 ) were of the same order of magnitude as adsorption of asphaltenes on minerals. The saturation adsorptions were less than the monolayer surface coverage observed on water-in-hydrocarbon emulsion interfaces, indicating that there are a limited number of adsorption sites on the metals. Higher molar saturation adsorptions were observed for resins and low molar mass asphaltenes, suggesting that adsorption was limited by the morphology of the metal surface. In general, higher mass saturation adsorptions were observed when asphaltenes self-associated to greater extents and consequently larger molecules adsorbed on the surface.

The Peng-Robinson equation of state (EoS) was adapted using group contribution methods to model asphaltene precipitation from solutions of toluene and an n-alkane and from n-alkane diluted bitumens. A liquid-liquid equilibrium was assumed between a primary liquid phase and a second dense asphaltene phase. Bitumen was characterized in terms of solubility fractions: saturates, aromatics, resins, and asphaltenes. Critical properties of the saturates, aromatics, and resins were determined that fit their measured densities and compared well with existing critical property correlations. The saturate and aromatic critical properties were also tuned to fit asphaltene precipitation data from solutions of the saturate and toluene or the aromatic and heptane. Asphaltenes were divided into fractions of different molar masses using a gamma distribution function. EoS parameters for asphaltenes were determined that fit the measured densities, fit precipitation data for mixtures of asphaltenes, toluene, and heptane, and compared well with existing critical property correlations. The model successfully fitted and predicted the onset and amount of precipitation over a broad range of compositions, temperatures from 0 to 100 °C, and pressures up to 7 MPa. The model results were within the error of the measurements except for high dilutions with n-pentane.