Phase Behavior of Mixtures of Bitumen and n ‑Butane

The phase behavior of bitumen and n-butane mixtures was investigated at temperatures from 20 to 230°C and pressures from 2 to 10 MPa. The measurements included saturation pressures, compositions at the onset of the second liquid phase, and the compositions and masses of the light n-butane-rich and heavy “pitch” phases in the liquid-liquid region. The phase compositions were measured in terms of the n-butane, maltenes, and C5-asphaltenes (pentane insolubles) contents. The bitumen component yields were reported as the mass of the component in the pitch phase divided by the mass of bitumen in the feed. The onsets, yields, and phase compositions were insensitive to temperature and pressure except possibly at 2 MPa and 20°C. The phase boundary data were used to construct pressure-composition diagrams. The phase compositions were used to construct a ternary diagram from which equilibrium constants were determined. The equilibrium constants were correlated to the feed n-butane content and used in a flash calcula...