The phase behavior of Athabasca bitumen + toluene + water ternary mixtures

Accurate descriptions of the phase behavior and thermophysical properties of unconventional hydrocarbon resource + water mixtures are of great interest for their production, transport and refining. In this work, the phase behavior of ternary mixtures of Athabasca bitumen + toluene + water in the temperature range 473.2 to 573.5 K and pressure range 2.5 to 12.6 MPa are elucidated. Pressure–composition phase diagrams, solubility data for water in the hydrocarbon-rich phase, and the density of the water-saturated hydrocarbon phase are reported. Toluene + water binary exhibits Type IIIa phase behavior, where the toluene rich phase becomes critically identical with the vapor phase in the presence of a subcritical water-rich liquid phase. The Athabasca bitumen + water pseudo binary exhibits Type IIIb phase behavior, where the water-rich liquid phase becomes critically identical with the vapor phase in the presence of a subcritical bitumen-rich phase. As toluene is added to the bitumen + water mixture, there is a transition in the order of liquid–vapor criticality. Further, the hydrocarbon-rich liquid phase becomes less dense than the water-rich liquid phase as toluene is added to the mixture. The boundary for the inversion of the phase density for mixtures of Athabasca bitumen + toluene + water is evaluated as a function of toluene composition, and these and other key features of the phase behavior and phase properties discussed.