High-pressure phase behaviour of carbon dioxide + methylcyclopentane binary system

The vapour – liquid critical curve of the carbon dioxide (CO₂) + methylcyclopentane (MCP) binary system is reported. Isothermal vapour–liquid equilibrium (VLE) data as well as the density of the liquid phase were also measured at five temperatures (323.15–383.15 K) and pressures up to 130 bar using the “AnTVisVarCap” method, as systematised by Dohrn and co-workers. The newly determined isothermal data are compared with the limited literature data available, which are critically reviewed and analysed. It is important to note that, in the three existing studies reporting carbon dioxide solubilities in methylcyclopentane, the reported purities of the components are either unspecified or differ significantly, potentially contributing to discrepancies in the data. Both the new and literature datasets were correlated using the General Equation of State (GEOS), Peng–Robinson (PR), Predictive Peng–Robinson ‘78 (PPR78), and Soave–Redlich–Kwong (SRK) equations of state, employing various modelling strategies. The effect of the critical properties and acentric factors of the pure components on the phase behaviour of the binary system was also examined and found to be negligible. Additionally, comparisons were made with analogous CO₂ binary systems incorporating n-hexane (nH) and cyclohexane (CH) as the second component, representing the corresponding n-alkane and structural isomer of methylcyclopentane, respectively.