Experimental measurement and modelling with Aspen Plus® of the phase behaviour of supercritical CO2 + (n-dodecane + 1-decanol + 3,7-dimethyl-1-octanol)

• Different phase behaviour exhibited by close-boiling compounds.
• Accurate representation of binary phase equilibrium data with RK-ASPEN model.
• Good prediction of low solute concentration multi-component phase equilibrium.
• Solute–solute interaction parameters required for increased model prediction accuracy.
• Separation analysis indicates SFE of close-boiling compounds is possible.

Experimental phase equilibrium data for the systems CO2 + n-dodecane, CO2 + 1-decanol and CO2 + 3,7-dimethyl-1-octanol were used to determine values for binary interaction parameters for use in the RK-ASPEN thermodynamic model in Aspen Plus®. Bubble and dew point data of the mixtures CO2 + (n-dodecane + 1-decanol), CO2 + (n-dodecane + 3,7-dimethyl-1-octanol), CO2 + (1-decanol + 3,7-dimethyl-1-octanol) and CO2 + (n-dodecane + 1-decanol + 3,7-dimethyl-1-octanol) were measured experimentally in a static synthetic view cell, and compared to the data predicted by the RK-ASPEN model. The model predicted the phase equilibrium data reasonably well in the low solute concentration region; significant deviation of model predictions from experimental data occurred in the mixture critical and high solute concentration regions due to the exclusion of solute–solute interaction parameters in the model. Distribution coefficients and separation factors were determined for the multi-component mixture and separation of the alkane from the alcohol mixture with a supercritical fluid extraction process was found to be possible.

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