Phase equilibrium data and thermodynamic modeling of the system propane + NMP + methanol at high pressures

This work reports phase equilibrium data at high pressures for the binary and ternary systems formed by propane + n-methyl-2-pyrrolidone (NMP) + methanol. Phase equilibrium measurements were performed in a high-pressure variable-volume view cell, following the static synthetic method for obtaining the experimental bubble and dew points transition data in the temperature range of 363–393 K, pressures up to 16 MPa and overall molar fraction of the lighter component varying from 0.1 to 0.998. For the systems investigated, vapor–liquid (VLE), liquid–liquid (LLE) and vapor–liquid–liquid (VLLE) phase transitions were visually recorded. Results show that the systems investigated present UCST (upper critical solution temperature) phase transition curves with an UCEP (upper critical end point) at a temperature higher than the propane critical temperature. The experimental data were modeled using the Peng–Robinson equation of state with the Wong–Sandler and the classical quadratic mixing rules, affording a satisfactory representation of the experimental data.