PVT and Thermal-Pressure Coefficient Measurements and Derived Thermodynamic Properties of 2-Propanol in the Critical and Supercritical Regions

Abstract

PVT properties and the thermal-pressure coefficient, $\gamma_{\text{V}} = \left( {\partial P/\partial T} \right)_{\text{V}}$, of 2-propanol have been simultaneously measured in the near- and supercritical regions using high-temperature and high-pressure nearly constant-volume piezo-calorimeter. Measurements were made along 9 liquid and 3 vapor isochores between (234.3 and 697.69) kg·m⁻³ and at temperatures from (317.17 to 522.36) K at pressures up to 6.05 MPa. For each measured isochore ($\rho$), the values of phase transition temperature ($T_{S}$) and pressure ($P_{S}$) at the liquid–gas phase equilibrium curve have been determined using the isochoric $P - T$ break point and thermal-pressure coefficient abruptness techniques. The measured saturated liquid ($\rho^{\prime}_{S}$) and vapor ($\rho^{\prime\prime}_{S}$) densities near the critical point and thermal-pressure coefficient abruptness disappearance were used to estimate the values of the critical parameters ($T_{C}$ = 508.72 K, $P_{C}$ = 4.840 MPa, and $\rho_{C}$ = 268.82 kg·m⁻³) of 2-propanol. The expanded uncertainty of the pressure ($P$), density ($\rho$), and thermal-pressure coefficient ($\gamma_{\text{V}}$) measurements at the 95 % confidence level with a coverage factor of k = 2 are estimated to be 0.05 %, 0.16 %, and 1.5 %, respectively. Scaling-type critical anomaly of the asymptotic behavior of thermal-pressure coefficient in the immediate vicinity of the critical point was experimentally observed. The measured pressures ($PVT$) and thermal-pressure coefficients ($\gamma_{\text{V}} VT$) have been used to calculate of the other key thermodynamic properties such as internal pressure ($P_{\text{int}}$), enthalpy ($\Delta H_{vap}$) and entropy ($\Delta S_{vap}$) of vaporization, saturation ($C_{\text{sat}}$), isobaric ($C_{\text{P}}$), and isochoric ($C_{\text{V}}$) heat capacities.