Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT), a physically based model that accounts for different molecular interactions explicitly, was applied to describe for the first time the phase behavior of deep eutectic solvents (DESs) with CO2 at temperatures from 298.15 to 318.15 K and pressures up to 2 MPa. DESs are mixtures of two solid compounds, a hydrogen bond donor (HBD) and a hydrogen bond acceptor (HBA), which form liquids upon mixing with melting points far below that of the individual compounds. In this work, the HBD is lactic acid and the HBAs are tetramethylammonium chloride, tetraethylammonium chloride, and tetrabutylammonium chloride. Two different modeling strategies were considered for the PC-SAFT modeling. In the first strategy, the so-called pseudo-pure component approach, a DES was considered as a pseudo-pure compound, and its pure-component parameters were obtained by fitting to pure DES density data. In the second strategy, the so-called individual-component approach, a DES was considered to consist of two individual components (HBA and HBD), and the pure-component parameters of the HBA and HBD were obtained by fitting to the density of aqueous solutions containing only the individual compounds of the DES. In order to model vapor-liquid equilibria (VLE) of DES + CO2 systems, binary interaction parameters were adjusted to experimental data from the literature and to new data measured in this work. It was concluded that the individual-component strategy allows quantitative prediction of the phase behavior of DES + CO2 systems containing those HBD:HBA molar ratios that were not used for k(ij) fitting. In contrast, applying the pseudo-pure component strategy required DES-composition specific k(ij) parameters.
The solubility of CO2 in
hydrophobic deep eutectic solvents
(DESs) has been measured for the first time. Six different hydrophobic
DESs are studied in the temperature range from 298 to 323 K and at
CO2 pressures up to 2 MPa. The results are evaluated by
comparing the solubility data with existing hydrophilic DESs and currently
applied physical solvents and fluorinated ionic liquids. The DESs
are prepared by mixing decanoic acid with a quaternary ammonium salt
with different halide anions and alkyl chain lengths. The measured
CO2 solubilities are similar to those found in renowned
fluorinated ILs, while the heats of CO2 absorption are
in the range of nonpolar solvents. The presented DESs show good potential
to be used as CO2 capture agents.
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