Experimental solubility and density studies on aqueous solutions of quaternary ammonium halides, and thermodynamic modelling for melting enthalpy estimations

Abstract

Aiming to extend the yet limited knowledge on phase equilibria and physical-chemical properties of quaternary alkylammonium halides and their aqueous binary systems, the solubilities of ten salts in water were measured in this work in the temperature range between 293.2 K and 348.2 K along with their densities. The PC-SAFT equation of state was then applied in the description of density as well as water activity coefficients data. The modelling results describe very satisfactorily the experimental data, and the non-associating parameters follow welldefined trends with the molecular weight of the alkylammonium halides. These parameters were applied in the prediction of the solubility data with unsatisfactory results, with mole fraction average absolute deviation (AAD = 0.018), deteriorating with increasing alkyl chain length. However, refitting the binary interaction parameter a much better description is obtained (AAD = 0.0045). COSMO-RS was also applied for the solubility prediction (AAD = 0.025), with poorer results for the chloride salts. After, the melting enthalpies of the quaternary alkylammonium halides were estimated using the PC-SAFT equation, which in spite of their uncertainty, are possibly the best option to perform solid-liquid equilibrium analysis of utmost importance when designing and screening new deep eutectic mixtures based on these compounds.

Cocrystal Formation in Choline Chloride Deep Eutectic Solvents

“…The estimation was made based on the SLE data of ten binary eutectic mixtures containing ChCl with various ionic salts and assuming an ideal solution behavior of ChCl in the liquid solutions, i.e., γ ChCl = 1. Vilas-Boas et al used ChCl water solubility data and the PC-SAFT or COSMO-RS models to estimate the melting enthalpy of ChCl as Δ h m = 7.67 kJ mol –1 , assuming the melting temperature estimated in Fernandez et al In both studies, the systems were assumed to be of the simple eutectic type without accounting for the solid–solid transition of ChCl.…”

Extensive characterization of choline chloride and its solid–liquid equilibrium with water

“…The solubility of the aqueous solutions of choline chloride with salt mole fractions within the range of 0.486–0.515 was carried out by the isothermal shake-flask method, which is described in detail in previous studies by our group. 35,54,55 A small excess amount of choline chloride was added in a sealed glass flask containing around 50 ml of water. The flask was placed in an isothermal bath equipped with an external temperature Pt100 sensor (±0.1 K).…”

“…[32][33][34] Triolo and co-authors 33 proposed ''the first water-in-salt (WiS) natural deep eutectic solvent (NADES), hereinafter indicated as aquoline, a mixture of choline chloride (ChCl) and water with a molar ratio of 1 : 3.33 00 without considering adequately the solid-liquid phase diagram (SLPD) of the choline chloride + water mixture. Although the authors used the available solid-liquid equilibrium (SLE) information, 32,35 those data covered only part of the SLPD of this important mixture. Moreover, as we discussed elsewhere, 18 to name a certain proportion (1 : 3.33) of two compounds as a new substance (aquoline 33 ) is not adequate.…”

New Screening Protocol for Effective Green Solvents Selection of Benzamide, Salicylamide and Ethenzamide

“…The possibility of carrying out ab initio predictions directly from the molecular structure is very appealing [ 90 ]. Unfortunately, COSMO-RS formalism despite relying on chemical intuition, often fails in determining solubility [ 93 , 128 , 129 , 130 , 131 ] and other physicochemical properties [ 132 , 133 , 134 , 135 ]. Probably in most cases, the major explanation is the insufficient precision of available default parameterization [ 128 , 136 ], which on the other hand, in many cases provides quite an accurate match with measured values [ 56 , 90 , 91 , 137 ].…”