Effect of Water on the Density, Viscosity, and CO₂ Solubility in Choline Chloride/Urea

Abstract

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.

Carbon Dioxide Capture with Ionic Liquids and Deep Eutectic Solvents: A New Generation of Sorbents

“…Moreover, the addition of water to DES mixtures significantly decreases the density . Interestingly, the introduction of an aromatic group in HBDs (e.g., phenol, o ‐cresol) also decreases the density of DESs; the density of the DESs with o ‐cresol is lower than those with phenol.…”

“…For example, the viscosity of a water‐saturated ChCl–oxalic acid system at 293.15 K was 200 times lower than in the case of the dried sample. By increasing the amount of water, the viscosity of DESs decreased …”

A Thermodynamic Study of Aqueous 1‐Allyl‐3‐Methylimidazolium Formate Ionic Liquid as a Tailored Sorbent for Carbon Dioxide Separation

“…For the aqueous system studied in the experimental work, it was assumed that the vapor pressures of [Amim][HCOO] and H 2 O were negligible. As described in our previous work, the water content in the vapor phase is very low and can be neglected for the CO 2 –H 2 O systems under investigation. In fact, the strong interaction between H 2 O and [Amim][HCOO] further decreases the content of water in the vapor pressure.…”

“…The setup used to measure the gas solubility in a solvent is illustrated in our previous work . The apparatus consisted of a gas reservoir, an equilibrium cell, a magnetic stirrer, and two pressure transducers.…”

“…This is crucial, as water is one of the main impurities in CO 2 streams. Moreover, the viscosity of ILs is generally high relative to that of organic solvents, and water is often used as a co‐solvent to decrease the viscosity of ILs . Another option is to synthesize ILs with low viscosity.…”