Phase equilibria in supercritical propane systems for separation of continuous oil mixtures

Experimental and calculated phase equilibria are reported for two systems containing propane and petroleum-derived oil mixtures near 400 K and pressures to 55 bar; these conditions are close to critical. In the first system, the oil is rich in saturated hydrocarbons; in the second system, the oil is rich in aromatic hydrocarbons. For both oils, number-average molecular weights are in the range 300-350. Solubilities in two equilibrium phases, measured with a flow-cell apparatus, are correlated with the perturbed-hard-chain equation of state wherein the composition of the heavy hydrocarbon is described by a continuous distribution function. A simple procedure is proposed to derive a molecular-weight distribution from boiling-point data.