Measurement of key critical parameters for binary mixture of carbon dioxide (CO2) + dimethyl ether (DME) and modification of the CO2 + hydrocarbon (HC) prediction model

Abstract

The critical parameters of carbon dioxide (CO₂) + dimethyl ether binary mixture, including critical temperature and pressure, have been determined by variable-volume view-cell method in this study. The critical point is determined by observing the disappearance and reappearance of the vapor-liquid meniscus at the center of the sapphire viewport. The extended uncertainties of mixture composition, critical temperature, and critical pressure are less than 0.00023, 0.5 K, 0.03 MPa (k = 2, 0.95 confidence level), respectively. The experimental results are compared with predictions from the Peng-Robinson equation of state, the Modified Extended Chueh–Prausnitz (MECP) method, the Helmholtz energy equation of state, as well as with relevant data available in the literature. In addition, the Redlich-Kister equations are employed to correlate the experimental data, demonstrating excellent agreement with the average absolute relative deviation of 0.370 % for critical temperature and 0.252 % for critical pressure. Finally, the empirical coefficients of the MECP method are refined through correlating with experimental data of CO₂ + hydrocarbon mixture, thereby enhancing prediction accuracy for the critical properties of such mixture.