Regular Solution Model for Asphaltene Precipitation from Bitumens and Solvents

A regular solution theory liquid-liquid equilibrium model was developed to predict asphaltene precipitation from Western Canadian bitumens. The input parameters for the model are the mole fraction, molar volume, and solubility parameters for each component. Bitumens were divided into four main pseudo-components corresponding to SARA fractions: saturates, aromatics, resins, and asphaltenes. Asphaltenes were divided into fractions of different associated molar mass based on a Schultz-Zimm molar mass distribution. Asphaltene self-association was accounted for through the average molar mass of the distribution. The molar volumes and solubility parameters of the pseudo-components were calculated using solubility, density, and molar mass measurements. The model successfully predicted the effect of solvent type and associated molar mass on asphaltene precipitation for model oil and n-alkane systems. The model also predicted the onset and amount of asphaltene precipitation from bitumens.

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