High-Pressure Phase Equilibria Measurements of the Carbon Dioxide + Cycloheptane Binary System

Abstract

The phase behavior of the carbon dioxide + cycloheptane binary system for which no literature data are available has been examined at temperatures ranging from (292.6 to 372.8) K. Saturation pressures, ranging from (23.9 to 154.8) bar, were acquired by a synthetic and visual method. In concrete terms, an adjustable volume high-pressure cell was utilized to measure bubble and dew point pressures by visual detection of phase transitions at constant overall composition. A total of 11 different mixtures with mole fractions of carbon dioxide ranging from (0.20 to 0.96) were prepared and a total of 99 experimental points were reported. The experimental results obtained in this work reveal the absence of liquid-liquid immiscibility in the studied temperature range and make it possible to conclude that the vapor-liquid critical line of the binary system is continuous and uninterrupted between the two pure compounds. Experimental data were correlated with the Peng-Robinson equation of state and classical Van der Waals mixing rules with temperaturedependent binary interaction parameters. They were also compared to the PPR78 model, an entirely predictive group contribution method in which the kij depends on temperature.