VLE measurements and modelling for binary systems of hydrogen or ethylene with methylcyclohexane

Abstract

High-pressure vapour-liquid equilibrium data were measured for binary systems involving methylcyclohexane and hydrogen or ethylene. The data are critical for supporting thermodynamic models necessary for predicting thermodynamic properties required in the design of extraction, separation, reactor and fluid handling equipment. Measurements were performed using the analytical isothermal method at three temperatures (333.15, 348.15, and 368.15) K, and pressures up to 11 MPa. The phase compositions were determined via capillary sampling and gas chromatographic analysis. The expanded uncertainties in temperature and pressure were 0.09 K and 0.002 MPa, respectively. For phase composition, the average relative expanded uncertainties in the liquid and vapor phases were 5 % and 0.2 % for the hydrogen system, and 3 % and 0.3 % for the ethylene system. The data were regressed using the Peng–Robinson equation of state in combination with either the classical van der Waals or the Wong–Sandler mixing rule, the latter coupled with the NRTL activity coefficient model. The van der Waals mixing rule was applied to the hydrogen system, while both mixing rules were evaluated for the ethylene system. Mixture critical points were estimated using a scaling law approach. The experimental data for both systems were thermodynamically consistent according to the Valderrama-Alvarez area test. The model adequately represented the data, particularly when a single set of temperature-dependent binary interaction parameters was applied across the temperature range.