Density measurements of homogeneous phase fluid mixtures comprising CO2/propanol and CO2/butanol binary systems and correlation with PC-SAFT equation of state

Abstract

Given that supercritical CO₂–alcohol mixtures are often encountered in natural gas, oil, and petroleum industries, the properties of binary CO₂/alcohol mixtures are essential for chemical process design, and their prediction is important. Equations of state (EoSs) are powerful tools for estimating physical properties and can be used to determine those of CO₂/alcohol binary mixtures if molecular association is considered, i.e., the examination of the CO₂–alcohol association from the EoS perspective improves property estimation. Herein, the densities of homogeneous phase fluid mixtures comprising CO₂/1-propanol, CO₂/2-propanol, and CO₂/1-butanol binary systems, which are greatly affected by mixing, were measured using a high-pressure vibration-type density meter equipped with a circulation pump and variable-volume viewing cell. Homogeneity was ensured by observing the fluid through the viewing window of the variable-volume cell. Measurements were carried out at temperatures of 313–353 K, CO₂ contents of 0–80 mol%, and pressures of up to 20 MPa, and the obtained data were correlated using the considering association between CO₂ and alcohol-perturbed chain-statistical associating fluid theory (CACA-PC-SAFT) EoS. The mixture density correlation was affected by the estimation accuracy of the pure-alcohol density. Therefore, the pure-alcohol density was correlated using the PC-SAFT EoS, and the pure-alcohol parameters were determined. The mixture density was effectively correlated using the CACA-PC-SAFT EoS based on these parameters. Furthermore, we determined the dependence of the obtained mixing parameters on temperature and alcohol species, revealing that mixing parameters could be predicted by combining experimental or quantum chemical information on alcohols or CO₂ and alcohols.