A united chemical thermodynamic model, that is, the COSMO-UNIFAC model, was first proposed to predict the phase equilibrium of multicomponent systems in which the UNIFAC model parameters are missing. This model combines the advantages of the UNIFAC model (accurate prediction) and the COSMO-based models (a priori prediction). The predicted vapor−liquid equilibrium results by the COSMO-UNIFAC model were compared with experimental data from the literature and this work, confirming that it can provide a moderate quantitative prediction even if the UNIFAC model parameters are missing.
Ionic liquids (ILs) have been proposed to simultaneously capture a variety of condensable gases for the first time. The hydrophobic IL [EMIM][Tf 2 N] was selected as a suitable absorbent screened by the COSMO-RS (conductor-like screening model for real solvents) model, which in combination with the quantum chemistry calculation provided some theoretical insight into mechanisms with respect to condensable gas capture. Considering the simultaneous capture of volatile organic compounds (VOCs) and water, we selected benzene, toluene, and pxylene (BTX) as three kinds of VOC representatives, measured the vapor− liquid equilibrium (VLE) of BTX + [EMIM][Tf 2 N] mixture systems, and compared them with the predicted results by the UNIFAC−Lei model. The experiment of capturing condensable gases with [EMIM][Tf 2 N] as the absorbent was conducted. Furthermore, the conceptual design of continuous processes with [EMIM][Tf 2 N] and the conventional benchmark solvent triethylene glycol as absorbents at the industrial scale was performed using a rigorous equilibrium stage model with the UNIFAC− Lei model parameter input. It reveals that condensable gas capture with an IL belongs to a typical process intensification technology in chemical engineering.
In
this work, a priori COSMO-SAC model was combined
with the original UNIFAC model, and thus the new COSMO-SAC-UNIFAC
thermodynamic model with a strong predictive power for fluid phase
equilibrium (VLE, LLE) was proposed. By this means the group binary
parameter matrix of original UNIFAC model was extended by introducing
the new 648 vacant parameter pairs for 51 main functional groups for
the conventional substances in this work. Moreover, the combined thermodynamic model was first
applied to process simulation on gas drying with ionic liquids (ILs).
To verify the reliability of the COSMO-SAC-UNIFAC model, the predictive
values were directly compared with experimental data coming from this
work, our previous work, and literature. The moderately accurate predictions
of the COSMO-SAC-UNIFAC model demonstrate the high potential applicability
of this new model, especially for numerous systems with missing parameters
including ILs, which are normally encountered in the original UNIFAC
model.
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