HIGH-PRESSURE VAPOR-LIQUID-EQUILIBRIA IN THE PROPANE-1-PROPANOL SYSTEM

High-pressure isothermal vapor liquid equilibrium data were measured for the propane-1-propanol system at 81.6, 105.2, and 120. 1-degrees-C in a static equilibrium cell with liquid-phase sampling by a piston-driven sampling rod and homogenizing the sample with a static jet mixer. The vapor phase was sampled by releasing it into an evacuated manifold, and the gas chromatograph was calibrated with a new variable volumetric device. Satisfactory modeling was achieved with the combined method (Wichterle, 1978b) using the UNIQUAC equation with equations of state: the group contribution EOS (Skjold-Jorgenson, 1986), Peng-Robinson EOS (Peng Robinson, 1976) or the two-parameter Virial EOS. Differences between the measured and calculated vapor-phase mole fractions, however, were significant for the lower-pressure regions of the 81.6 and 120. 1-degrees-C isotherms. UNIQUAC parameters a(ij), hitherto unavailable, with fairly strong temperature dependence in the 81.6 to 120. 1-degrees-C range are proposed for the system. The covariance matrix indicated a significant correlation among the parameters. The classical mixing rule interaction parameters, delta(ij), required for the original Peng-Robinson EOS in the combined method were obtained using the direct method ( Wichterle, 1978a) and were temperature-independent for the isotherms for which the propane was supercritical. The possibility of propane/1-propanol immiscibility was theoretically examined according to the criteria of Baker et al. (1982). The plots of Gibbs energy of mixing vs. phase mole fractions did not indicate liquid-phase splitting, but the inferences are EOS-dependent and must await visual confirmation. Our earlier vapor-phase thermodynamic consistency test (1991a) indicated the data for all three data sets not to be inconsistent.