An Experimental Study of the Heavy Hydrocarbon Impact on Phase Behavior of Hydrocarbon Mixtures

Abstract

Abstract It is of much interest to study an impact of heavy hydrocarbons on the phase behavior of hydrocarbon mixtures. Using a method of the precision adiabatic calorimetry the phase equilibria in quaternary mixtures of methane, propane, octane, and nonane have been studied. The phase diagrams for investigated mixtures have been plotted based on the experimental data. The phase transitions were localized by the finite discontinuities in temperature derivatives of the thermodynamic potentials. The heat capacity, internal energy, pressure, and temperature derivative of pressure at constant volume were measured in the range 170–320 K, up to 40 MPa. Quaternary mixtures as quasi-binary mixtures are presented. The first quasi-component of the quasi-binary mixture is a binary mixture with the constant methane/propane ratio. The second quasi-component of the quasi-binary mixture is a binary mixture of octane and nonane. Investigated hydrocarbon system is a combination of the simple hydrocarbon mixtures for the low concentration of octane and nonane. In the earlier papers we presented the simple hydrocarbon mixtures for the low concentration of octane, nonane, and decane, and quaternary mixtures of methane, propane, octane, and decane for the low concentration of octane and decane, which are a combination of the simple hydrocarbon mixtures for the low concentration of octane and decane. Our investigations show that quaternary hydrocarbon mixture for the low concentration of octane and nonane as well as the simple hydrocarbon mixtures for the low concentration of octane, nonane, and decane split into three phases, the octane-nonane-lean macrophase and the microphases formed by octane and nonane. Besides, the heavy components provoke a split of the liquid part of a quaternary mixture into two liquid phases, the octane-nonane-rich phase and the octane-nonane-lean phase.