Comprehensive review of unique effects of water on ionic liquids and deep eutectic solvents observed in experimental and theoretical studies.

a b s t r a c t ePC-SAFT was used to investigate the density and gas solubilities in imidazolium-based ionic liquids (ILs) applying different modeling strategies. The ion-based strategy including a Debye-Hückel Helmholtzenergy term to represent the ionic interactions describes the experimental data best. For this strategy, the IL was considered to be completely dissociated into a cation and an anion. Each ion was modeled as non-spherical species exerting repulsive, dispersive, and Coulomb forces. A set of ePC-SAFT parameters for seven ions was obtained by fitting to reliable density data of pure ILs up to 1000 bar with a fitting error of 0.14% on average. The model can be used to quantitatively extrapolate the density of pure ILs at temperatures from 283 to 473 K and pressures up to 3000 bar. Moreover, this strategy allows predicting CO 2 solubilities in ILs between 293 and 450 K and up to 950 bar. Applying the same set of IL parameters, the much lower solubility of CH 4 compared to CO 2 can also be predicted with ePC-SAFT.

High cost and high energy penalty for CO uptake from flue gases are important obstacles in large-scale industrial applications, and developing efficient technology for CO capture from technical and economic points is crucial. Ionic liquids (ILs) show the potential for CO separation owing to their inherent advantages, and have been proposed as alternatives to overcome the drawbacks of conventional sorbents. Chemical modification of ILs to improve their performance in CO absorption has received more attention. Deep eutectic solvents (DESs) as a new generation of ILs are considered as more economical alternatives to cope with the deficiencies of high cost and high viscosity of conventional ILs. This Review discusses the potential of functionalized ILs and DESs as CO sorbents. Incorporation of CO -philic functional groups, such as amine, in cation and/or anion moiety of ILs can promot their absorption capacity. In general, the functionalization of the anion part of ILs is more effective than the cation part. DESs represent favorable solvent properties and are capable of capturing CO , but the research work is scarce and undeveloped compared to the studies conducted on ILs. It is possible to develop novel DESs with promising absorption capacity. However, more investigation needs to be carried out on the mechanism of CO sorption of DESs to clarify how these novel sorbents can be adjusted and fine-tuned to be best tailored as optimized media for CO capture.

To study the effect of water on the properties of choline chloride (ChCl)/urea mixtures (1:2 on a molar basis), the density and viscosity of ChCl/ urea (1:2) with water were measured at temperatures from 298.15 K to 333.15 K at atmospheric pressure, the CO 2 solubility in ChCl/urea (1:2) with water was determined at 308.2 K, 318.2 K, and 328.2 K and at pressures up to 4.5 MPa. The results show that the addition of water significantly decreases the viscosity of ChCl/urea (1:2), whereas the effects on their density and CO 2 solubility are much weaker. The CO 2 solubility in ChCl/urea (1:2) with water was represented with the Nonrandom-Two-Liquid Redlich−Kwong (NRTL-RK) model. The excess molar volume and excess molar activation energy were further determined. The CO 2 absorption enthalpy was calculated and dominated by the CO 2 dissolution enthalpy, and the magnitude of the CO 2 dissolution enthalpy decreases with the increase of water content.

In SAFT1-RPM approximations of CO2−H2O and CO2−H2O−NaCl systems, relevant to oil recovery and CO2 sequestration, CO2 is modeled as a molecule with three association sites, two sites of type O and one site of type C. H2O is modeled as a molecule with four association sites, two sites of type O and two sites of type H. The salt is modeled as a molecule composed of two charged, but nonassociating, spherical segments, of which one represents the cation and one represents the anion. For the CO2−H2O system, only one type of cross-association is assigned, i.e., between the site of type O in CO2 and the site of type H in H2O. Using temperature-dependent parameters, SAFT1-RPM is found to represent the density and equilibrium data for the CO2−H2O system, including the minimum H2O concentration in the CO2-rich phase in the y-P diagram. For the CO2−H2O−NaCl system, an additional binary interaction constant is used, the same for both CO2−Na+ and CO2−Cl- pairs, which is needed to correct the short-range interactions. SAFT1-RPM is also found to represent the equilibrium and density data for the CO2−H2O−NaCl system.

Sustainable and effective methods for biomass pretreatment and biomass cascade utilization are reviewed in this work.

Statistical associating fluid theory coupled with the restricted primitive model is extended to multivalent ions by relaxing the range of the square-well width parameter, which leads to a new dispersion term approximation and calls for a new set of salt and ion parameters. This new approximation, referred to as SAFT2, requires a single set of parameters derived from the salt (mean ionic) activity coefficients and liquid densities of single-salt solutions for five cations (Li(+), Na(+), K(+), Ca(2+), Mg(2+)), six anions (Cl(-), Br(-), I(-), NO(3)(-), SO(4)(-2), HCO(3)(-)), and 24 salts. These parameters, in turn, are shown to predict the osmotic coefficients for single salt + water solutions.

35 novel DESs are synthesized and screened in terms of their CO2 solubility and viscosity.