Densities, Viscosities, and Electrical Conductivities of Pure Anhydrous Reline and Its Mixtures with Water in the Temperature Range (293.15 to 338.15) K
Abstract:Density (ρ), dynamic viscosity (η), and electrical conductivity (κ) of the deep eutectic solvent (DES) reline, composed of choline chloride (ChCl) and urea in a 1:2 molar ratio, and its mixtures with water, covering the entire miscibility range, were studied at T = (293.15 to 338.15) K. Compared to many previous studies, reline purity was significantly improved by using ultrapure urea and ChCl recrystallized from ethanol. For the investigated DES samples the mass fraction of residual water was <0.00035. This a… Show more
“…The experimental data were taken from a recent study by Agieienko and Buchner. 72 The MD simulations are in close agreement with the experiments. This is a strong indication that the computed self-diffusion coefficients (Figure 4) are accurate.…”
Deep eutectic solvents (DESs) are a new generation of
green solvents,
which are considered an environmentally friendly alternative to ionic
liquids and volatile organic compounds. The addition of controlled
amounts of water to DESs has a significant effect on their microscopic
structure and thus on their thermodynamic and transport properties.
In this way, DESs can be modified, leading to solvents with improved
characteristics. In this work, molecular dynamics (MD) simulations
are performed to obtain a better understanding of the relation between
the microscopic structure, molecular interactions, and thermophysical
properties of aqueous reline and ethaline solutions at temperatures
ranging from 303.15 to 363.15 K. For both reline and ethaline solutions,
the hydrogen bond (HB) networks disappear with increasing mass fraction
of water, and the intensity of radial distribution function (RDF)
peaks decreases. For a mass fraction of water of 40%, most of the
HBs between the compounds of reline and ethaline are broken, and DESs
are fully dissolved in water. Consequently, a monotonic decrease in
viscosities and an increase in self-diffusion coefficients are observed.
Ionic conductivities show a nonmonotonic behavior with increasing
water content. Up to 60% water mass fraction, the ionic conductivities
increase with increasing water content. A further increase in the
mass fraction of water decreases conductivities. For all studied systems,
the HB network and the peaks of RDFs show relatively small changes
for water mass fractions below 5% and beyond 40%. The MD results show
that viscosities decrease with temperature, while diffusivities and
ionic conductivities increase. The effect of the temperature on the
structure of DES–water mixtures is negligible.
“…The experimental data were taken from a recent study by Agieienko and Buchner. 72 The MD simulations are in close agreement with the experiments. This is a strong indication that the computed self-diffusion coefficients (Figure 4) are accurate.…”
Deep eutectic solvents (DESs) are a new generation of
green solvents,
which are considered an environmentally friendly alternative to ionic
liquids and volatile organic compounds. The addition of controlled
amounts of water to DESs has a significant effect on their microscopic
structure and thus on their thermodynamic and transport properties.
In this way, DESs can be modified, leading to solvents with improved
characteristics. In this work, molecular dynamics (MD) simulations
are performed to obtain a better understanding of the relation between
the microscopic structure, molecular interactions, and thermophysical
properties of aqueous reline and ethaline solutions at temperatures
ranging from 303.15 to 363.15 K. For both reline and ethaline solutions,
the hydrogen bond (HB) networks disappear with increasing mass fraction
of water, and the intensity of radial distribution function (RDF)
peaks decreases. For a mass fraction of water of 40%, most of the
HBs between the compounds of reline and ethaline are broken, and DESs
are fully dissolved in water. Consequently, a monotonic decrease in
viscosities and an increase in self-diffusion coefficients are observed.
Ionic conductivities show a nonmonotonic behavior with increasing
water content. Up to 60% water mass fraction, the ionic conductivities
increase with increasing water content. A further increase in the
mass fraction of water decreases conductivities. For all studied systems,
the HB network and the peaks of RDFs show relatively small changes
for water mass fractions below 5% and beyond 40%. The MD results show
that viscosities decrease with temperature, while diffusivities and
ionic conductivities increase. The effect of the temperature on the
structure of DES–water mixtures is negligible.
“…For ChCl:U, linewidth corrections were derived from interpolated viscosities reported at 298.15 K by Agieienko and Buchner. 34 We experimentally verified their data, as well as other datasets, 49,50 at two ChCl:U-water dilutions (Fig. S7 and S10).…”
supporting
confidence: 62%
“…FWHM of ChCl:U was corrected with viscosity data from Agieienko and Buchner. 34 35 Cl NMR spectroscopy has been used before to investigate H-bonding and Clbinding in a multitude of systems, with Clchemical shift, linewidth and relaxation time characterising ion dynamics. [35][36][37][38][39][40][41][42][43] Twenty samples of ChCl:U and ChCl:G were prepared at several dilutions, up to 98 wt% H2O (experimental details in the ESI) †.…”
The Deep Eutectic Solvents (DESs) choline chloride:urea (xChCl = 0.33) and choline chloride:glycolic acid (xChCl = 0.5) were studied using viscosity-corrected 35Cl NMR and MD simulations to probe the role of chloride as a function of water content.
“…On the other hand, the refractive index shows almost constant values with increasing volume % of EtOH in the hybrid solvent. Similar findings have been reported in the literature [ 31 , 41 , 42 ]. Fig.…”
Deep eutectic solvents (DESs) have high viscosities, but known to be mitigated by addition of suitable co-solvent. The effect of such co-solvent on the extraction efficiency of the hybrid solvent is hardly known. This study examined the effect of ethanol on three choline chloride-based DESs (glyceline, reline, and ethaline) by mixing each in turn with ethanol in various volume proportions. The hybrid solvents were evaluated for the extraction of benzene from n-hexane. Pseudo-ternary liquid–liquid equilibrium data were obtained using the refractive index method at 303 K and 1 atm for the systems, n-hexane (1) + benzene (2) + hybrid solvent (glyceline/ethanol, ethaline/ethanol, reline/ethanol) (3), and used to evaluate distribution coefficient (D) and selectivity (S). Furthermore, the physicochemical properties of the hybrid solvents were also determined. The results indicate increase in selectivity with increasing ethanol addition up to 50% and decrease with further addition. All hybrid solvents with 50% ethanol outperform sulfolane and are suitable replacement for same as green and sustainable extractant for aromatics from aliphatics. The glyceline + 50% ethanol emerged the overall best with 49.73% elevation in selectivity and 41.15% reduction in viscosity relative to the neat glyceline. The finding of this study is expected to fillip the drive for paradigm shift in petrochemical industries.
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