Experimental determination and theoretical modeling of the vapor–liquid equilibrium and densities of the binary system butan-2-ol + tetrahydro-2H-pyran

Isobaric vapor–liquid equilibrium (VLE) data have been measured for the binary system butan-2-ol + tetrahydro-2H-pyran at 50, 75, and 94 kPa and over the temperature range from 339 to 370 K using a vapor–liquid equilibrium still with circulation of both phases. Mixing volumes were also determined at 298.15 K and atmospheric pressure with a vibrating tube densimeter. According to experimental results, the zeotropic mixture exhibits slight positive deviation from ideal behavior over the experimental range. The excess molar volumes (v˜E) of the system are positive over the whole mole fraction range. The VLE data of the binary mixture satisfy the Fredenlund's consistency test and were well-correlated by the Wohl, nonrandom two-liquid (NRTL), Wilson, and universal quasichemical (UNIQUAC) equations for all of the measured isobars. The v˜E, in turn, were satisfactorily correlated using a second order Redlich–Kister equation.The theoretical modeling of the measured VLE and v˜E data has been carried out using the polar perturbed chain statistical association fluid theory (PPC-SAFT) equation of state. In this molecular based approach, butan-2-ol was described as a polar auto-associating molecule, while tetrahydro-2H-pyran is treated as polar molecule. Molecular interactions between these two components have been approximated in terms of a hetero-association theory. It is demonstrated that a common set of parameters is able to simultaneously reproduce with good agreement both phase equilibrium and excess molar volumes measurements.