Fluid phase behavior of asymmetric synthetic mixture plus gas: Experimental and modeling studies

This study investigates the high-pressure phase behavior of synthetic systems formed by the blending of a ternary heavy liquid mixture: 2,2,4,4,6,8,8 heptamethylnonane + dodecylcyclohexane + o-terphenyl - with light gas mixtures. Two different gas mixtures were examined: methane + ethane + propane and methane + ethane + propane + carbon dioxide. Five global compositions were studied for the first gas+liquid system and seven for the second, with temperatures ranging from T = 293.15 K to 373.15 K and pressures up to p = 70 MPa. One hundred and eighteen pressure transitions were measured, including fluid-fluid and solid-fluid transitions. The Peng-Robinson equation of state, with the fully predictive mixing rule PPR78, was used to predict the observed fluid-fluid transitions, showing qualitatively good agreement with experiments.