Vapor pressures and vapor phase compositions of choline chloride urea and choline chloride ethylene glycol deep eutectic solvents from molecular simulation

Abstract

Despite the widespread acknowledgment that deep eutectic solvents (DESs) have negligible vapor pressures, very few studies in which the vapor pressures of these solvents are measured or computed are available. Similarly, the vapor phase composition is known for only a few DESs. In this study, for the first time, the vapor pressures and vapor phase compositions of choline chloride urea (ChClU) and choline chloride ethylene glycol (ChClEg) DESs are computed using Monte Carlo simulations. The partial pressures of the DES components were obtained from liquid and vapor phase excess Gibbs energies, computed using thermodynamic integration. The enthalpies of vaporization were computed from the obtained vapor pressures, and the results were in reasonable agreement with the few available experimental data in the literature. It was found that the vapor phases of both DESs were dominated by the most volatile component (hydrogen bond donor, HBD, i.e., urea or ethylene glycol), i.e., 100% HBD in ChClEg and 88%-93% HBD in ChClU. Higher vapor pressures were observed for ChClEg compared to ChClU due to the higher volatility of ethylene glycol compared to urea. The influence of the liquid composition of the DESs on the computed properties was studied by considering different mole fractions (i.e., 0.6, 0.67, and 0.75) of the HBD. Except for the partial pressure of ethylene glycol in ChClEg, all the computed partial pressures and enthalpies of vaporization showed insensitivity toward the liquid composition. The activity coefficient of ethylene glycol in ChClEg was computed at different liquid phase mole fractions, showing negative deviations from Raoult's law.

Solubilities and Transport Properties of CO2, Oxalic Acid, and Formic Acid in Mixed Solvents Composed of Deep Eutectic Solvents, Methanol, and Propylene Carbonate

“…The charges of choline chloride were scaled by a factor of 0.8 and 0.9 in reline and ethaline, respectively. 55 , 56 This implementation yields accurate predictions for various thermophysical properties of DES as shown by Perkins et al, 55 , 56 Salehi et al, 24 and Celebi et al 26 , 27 , 57 The Lennard-Jones interaction parameters between unlike species were computed using the Lorentz–Berthelot combining rules. 58 All force field parameters and the functional forms of the bonded and nonbonded terms used in this study are available in the Supporting Information .…”

“…The DES were modeled using the GAFF 53 force field consistently with our previous studies. 21 , 24 , 26 , 27 , 54 For choline, urea, and ethylene glycol, 1–4 interactions were scaled by a factor of 0.5 for both Lennard-Jones and Coulombic interactions. The charges of choline chloride were scaled by a factor of 0.8 and 0.9 in reline and ethaline, respectively.…”

Simulation of deep eutectic solvents: Progress to promises

“…Ferreira et al followed a similar procedure to calculate Δ H vap values for CCPro in separate work 143 . In general, while experimentally measured vapor pressures of DESs are quite close to the vapor pressures of their respective pure HBDs, 140 MD simulations have provided evidence that some proportion of the HBA components should be present in the gas phase of DESs 144 …”

Solvent Organization around Methane Dissolved in Archetypal Reline and Ethaline Deep Eutectic Solvents as Revealed by AIMD Investigation

“…Both reline and ethaline DESs exhibit good methane capturing ability . Another study performed by the same group employed MC simulations to compute the vapor phase compositions and vapor pressures of reline and ethaline . This study showed that HBD in both the DESs dominates the vapor phase, suggesting the volatile nature of HBD .…”

“…Another study performed by the same group employed MC simulations to compute the vapor phase compositions and vapor pressures of reline and ethaline . This study showed that HBD in both the DESs dominates the vapor phase, suggesting the volatile nature of HBD . Vlugt and co-workers performed molecular dynamics (MD) simulations to predict solubility parameters, enthalpy of vaporization, and vapor phase composition for various [Ch]­[Cl]-based DESs .…”