Modeling Asphaltene Precipitation by n-Alkanes from Heavy Oils and Bitumens Using Cubic-Plus-Association Equation of State

We apply a cubic-plus-association equation of state to study the asphaltene precipitation from n-alkane diluted model solutions (asphalteneþtoluene), and heavy oils and bitumens. Heavy oils and bitumens are characterized in terms of saturates, aromatics/resins, and asphaltenes; n-alkanes are treated independently. The asphaltene precipitation is modeled as liquid-liquid phase equilibrium. The self-association between asphaltene molecules and the cross-association between asphaltene and aromatics/resins (or toluene) molecules are explicitly taken into account. There is no self-association between aromatics/resins (or toluene) molecules. Our model contains only one adjustable parameter, the cross-association energy between asphaltene and aromatics/resins (or toluene) molecules, which depends on the types of asphaltene and n-alkane, and possibly temperature but is independent of pressure and concentration.We successfully predict the amount of asphaltene precipitation over a broad range of compositions, temperatures, and pressures for n-alkane diluted model solutions, heavy oils, and bitumens.