CO2 + n-dodecane + 3,7-dimethyl-1-octanol: High pressure experimental phase equilibria data and thermodynamic modelling

- New ternary high pressure VLE data for CO2 + n-dodecane + 3,7-dimethyl-1-octanol.
- Enhanced solubility in the high-nC12 region presents as a pinched two-phase band.
- Relative solubility increases with bulk solvent-free 3,7-dimethyl-1-octanol content.
- RK-ASPEN enabled a %AADP of 3.1% coupled with good qualitative correlations.

New high pressure VLE data for the ternary mixture CO2 + n-dodecane (nC12) + 3,7-dimethyl-1-octanol (37DM1O) are presented. A static apparatus with online analysis was used to measure phase compositions at 35, 55 and 75 °C, and pressures between 68 and 157 bar. In the high-nC12 region the mixture displayed enhanced solubility, presenting as a pinched two phase band and s-shaped liquid phase curves. Relative solubility, an indicator of fractionation sharpness, increased with 37DM1O content and the 75:25 nC12:37DM1O mixture cannot be separated using CO2. RK-ASPEN, SR-POLAR, PR-BM and PC-SAFT models were evaluated for their ability to correlate these data. RK-ASPEN and PC-SAFT models provided the best and worst correlation of equilibrium pressures with respective percentage average absolute deviations of 3.1% and 8.5%. RK-ASPEN model was impressive in its ability to capture the co-solubility pinch seen for the 75:25 nC12:37DM1O mixture and the resultant s-shaped liquid phase complexity.

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