Phase behavior of carbon dioxide + 2,4-dimethylpentane binary system at high pressures

Abstract

The phase behavior of the branched alkane 2,4-dimethyl pentane (2,4-DMP) and carbon dioxide (CO2) binary mixture that has no published data, to the best of our knowledge, was studied. The liquid–vapor critical line was determined up to 121.4 bar and 422.35 K, as well as vapor–liquid equilibrium (VLE) data at different constant temperatures (323.15, 343.15, 363.15, and 383.15) K and pressures between (10.4 and 120.4) bar. Phase behavior investigation was carried out in a high-pressures (HP) cell fitted with a pair of sapphire windows, one acting as a piston, hence volume up to 60 cm3, utilizing a static-analytical approach with phases sampling by the so called ROLSI valves (rapid online sample injectors) connected to a gas chromatograph (GC) for composition determination. The isothermal and critical data points for the carbon dioxide + 2,4-dimethylpentane binary mixture were modeled with the cubic equations of state (EoSs), i.e., Soave–Redlich–Kwong (SRK), Peng–Robinson (PR), and General Equation of State (GEOS), in combination with van der Waals mixing rules (one- and two-parameter conventional mixing rules, 1PCMR and 2PCMR). The calculations demonstrated that the selected models are capable of correctly reproducing the phase behavior of the mixture under study.