A Calorimetric Study of Phase Behavior of the Methane-Propane-Nonane System

Abstract

Abstract The recent results of the accurate calorimetric measurements of phase equilibria internary mixtures of methane, propane, and nonane have been presented. The heat capacity, internal energy, pressure, and temperature derivative of pressure at constant volume were measured in the range 160 – 340 K, up to 30 MPa. The phase transitions were localized by the finite discontinuities in temperature derivatives of the thermodynamic potentials. The phase diagrams for ternary mixtures of methane, propane, and nonane have been plotted based on the experimental data. These data are supplemented with the earlier measurements of two ternary hydrocarbon systems for the low concentration of octane and decane. Our investigations show that hydrocarbon mixture for the low concentration of nonane as well as the hydrocarbon mixtures for the low concentration of octane and decane split into two phases, the nonane-lean macrophase and the microphase formed by nonane. Besides, nonane provokes a split of the liquid part of a ternary mixture into two liquid phases, the nonane-rich phase and the nonane-lean phase.