Study of Deep Eutectic Solvent on the Base Choline Chloride as Entrainer for the Separation Alcohol–Ester Systems

Choline chloride-based deep eutectic solvent (DES) was tested for the separation of azeotropic mixtures of ethanol–ethyl acetate, <i>n</i>-propanol–<i>n</i>-propyl acetate and <i>n</i>-butanol–<i>n</i>-butyl acetate via liquid–liquid extraction. The mixture of choline chloride with malonic acid with a molar ratio of 1:1 was used. Extraction experiments were conducted with the ternary mixture ethanol–ethyl acetate–DES at temperatures 293.15, 303.15, and 313.15 K and with ternary mixtures <i>n</i>-propanol–<i>n</i>-propyl acetate–DES and <i>n</i>-butanol–<i>n</i>-butyl acetate–DES at 293.15, 303.15, 313.15, and 323.15 K. Liquid–liquid tie-lines for studied systems were determined. The extraction performance of DES was characterized with solute distribution coefficients and values of selectively respectively to alcohol. The influence of the alkyl chain length of the alcohol and ester on the phase equilibria was investigated. Experimental data were fitted using the nonrandom two liquids model

Influence of pH Value and Ionic Liquids on the Solubility of l‑Alanine and l‑Glutamic Acid in Aqueous Solutions at 30 °C

The solubility of the amino acids l-alanine and l-glutamic acid and its sodium salt (sodium l-glutamate monohydrate) in aqueous solutions at 30 °C and atmospheric pressure was investigated in the pH range between 3 and 9 and in the presence of the ionic liquids (ILs) 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([bmim]­[OTf]) and choline dihydrogencitrate ([ch][dhcit]) at pH 7. The solubility of l-alanine and l-glutamic acid in the solutions without IL was measured by UV spectroscopy and with a gravimetrical method. In the presence of an IL HPLC-analysis was applied. The solid phases were characterized using Raman spectroscopy and powder X-ray diffraction to distinguish the amino acids from their salts. While the solubility of l-alanine did not depend on pH within the considered pH range, the solubility of l-glutamic acid strongly increased with increasing pH. Below pH 6.2 the solid phase was characterized to be l-glutamic acid, while sodium l-glutamate monohydrate was found to be the solid at pH higher than 6.2. It could be observed that the solubility of sodium l-glutamate monohydrate was comparatively high, and increased with increasing pH. Upon addition of the ILs under investigation ([bmim]­[OTf]) and [ch]­[dhcit]) the solubility of l-alanine and l-glutamic acid was decreased. Original PC-SAFT was applied to predict the solubility of l-alanine and l-glutamic acid (and its sodium salt) in water, with and without the ILs under consideration, at the experimental conditions with quantitative agreement to the experimental data

Separation Performance of BioRenewable Deep Eutectic Solvents

Deep eutectic solvents (DESs) have been regarded as promising cost-effective and environmentally benign alternatives to conventional volatile organic solvents. The screening and selection of the suitable solvent for separation is an important part of the process design. Limiting activity coefficients provide a useful tool for the optimal choice of the selective solvent. For the first time, activity coefficients at infinite dilution have been measured in DESs as a solvent for 23 solutes (aliphatic and aromatic hydrocarbons, alcohols, ketones, ethers, and esters). The DESs were constituted from choline chloride and glycerol in molar ratios of 1:1 and 1:2. The measurements were carried out with the help of gas–liquid chromatography in the temperature range 298–358 K. Using experimental results, selectivity of different separation cases was assessed. To verify the separation performance of DESs the perturbed-chain statistical associating fluid theory (PC-SAFT) was employed for the first time. This method appears to be powerful tool for screening of suitable precursors and evaluation of separation performance at temperatures relevant for practical applications. It has turned out that the separation performances of DESs are comparable to those of ionic liquids, but DESs are cheaper, because they are constituted from natural and renewable nontoxic bioresources