Measurement and PC-SAFT modeling of solid-liquid equilibrium of deep eutectic solvents of quaternary ammonium chlorides and carboxylic acids

et al. 2018

Ind. Eng. Chem. Res.

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Aiming at providing an extensive characterization of the solid−liquid equilibria (SLE) of deep eutectic solvents (DESs), the phase diagrams of nine eutectic mixtures composed of choline chloride ([Ch]Cl) and (poly)carboxylic acids, commonly reported in the literature as DESs, were measured experimentally. Contrarily to the behavior reported for eutectic mixtures composed of [Ch]Cl (hydrogen-bond acceptor, HBA) and monofunctional hydrogen-bond donors (HBD) such as fatty acids and fatty alcohols, which have recently been shown to be almost ideal mixtures, a significant decrease of the melting temperature, at the eutectic point, was observed for most of the systems studied. This melting temperature depression was attributed to a pronounced nonideality of the liquid phase induced by the strong hydrogen-bond interactions between the two mixture components. Perturbed-chain statistical associating fluid theory (PC-SAFT) was used to describe these interactions physically. PC-SAFT allowed accurately modeling the experimental phase diagrams over the entire concentration and temperature ranges. Depending on the kind of mixture, up to two temperature-independent binary interaction parameters between HBA and HBD were applied. The PC-SAFT approach was used to provide trustworthy information on the nonideality of the liquid phase (expressed as the activity coefficients of HBA and HBD) as well as to estimate the eutectic points coordinates. The experimental data along with the modeling results allowed us to infer about the importance of the HBD's chemical structure on the formation of [Ch]Cl-based DESs.

Section: Industrial and Engineering Chemistry Researchsupporting

confidence: 81%

The Role of Polyfunctionality in the Formation of [Ch]Cl-Carboxylic Acid-Based Deep Eutectic Solvents

Crespo

et al. 2018

Ind. Eng. Chem. Res.

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“…The results obtained show that the binary systems composed of [Ch]Cl and fatty acids, although commonly reported as examples of type III DESs, exhibit an almost ideal behavior, showing only slight positive deviations from the ideal behavior more evident in the fatty acid solubility curve, as depicted in Figure 2. The absence of negative deviations to ideality is 7 are no longer observed.…”

Section: Resultsmentioning

confidence: 94%

“…In our previous work, 7 the formation of DESs composed of symmetrical tetraalkylammonium chlorides and fatty acids was reported, but the different chemical structure of [Ch]Cl and the presence of one additional hydroxyl group in the DES moiety can significantly influence the interactions between the DES constituents. Therefore, in this work, the solid−liquid phase diagrams of eight different eutectic mixtures formed by choline chloride and fatty alcohols or fatty acids are reported.…”

Section: Introductionmentioning

confidence: 99%

Characterization and Modeling of the Liquid Phase of Deep Eutectic Solvents Based on Fatty Acids/Alcohols and Choline Chloride

Crespo

et al. 2017

Ind. Eng. Chem. Res.

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The solid−liquid equilibria phase diagrams of eight eutectic systems formed by choline chloride and fatty acids, or fatty alcohols, were measured to characterize the nonideality of the liquid phase of these systems, commonly reported in the literature as examples of type III deep eutectic solvents (DESs), and to evaluate the best modeling approaches to their description. Most of these systems are shown to present only slight deviations from ideal behavior, resulting from a fine balance of the hydrogen bonding between the hydroxyl/carboxylic groups with the chloride anion and the interactions present in the pure compounds. The phase diagrams measured were modeled with an associative equation of state (EoS) and a g E model. As an EoS, the perturbed-chain statistical associating fluid theory (PC-SAFT) was used, and this model was able to accurately describe the experimental data and to provide reliable estimates of the eutectic points using just a single binary temperature-dependent interaction parameter that often correlates with the acid/alcohol chain length. The performance of PC-SAFT was further compared with the g E model, a non-random two-liquid model (NRTL), and was found to provide a better description of the experimental data, especially for the more nonideal systems. Ultimately, the data gathered, and the molecular modeling, allowed the discussion of the behavior of fatty acids or fatty alcohols as hydrogen bond donors in choline chloride-based DESs.

“…Recently there has been a growing interest for ionic liquid mixtures [11,12]. Not only does the use of mixtures of ionic liquids increases their designer capability, it also allows for the reduction of the melting point of some ionic solids, allowing the preparation of eutectic ionic liquids from ionic solids.…”

Section: Introductionmentioning

confidence: 99%

Can cholinium chloride form eutectic solvents with organic chloride-based salts?

Abranches

et al. 2019

Fluid Phase Equilibria

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The high melting point of a large number of organic salts with potential ionic liquid-like properties, hinders their applicability as solvents. Considering the success of cholinium chloride on lowering the melting temperature of several substances and its success on forming deep eutectic solvents, this work studies its mixing with organic chlorides to lower their melting points producing eutectic ionic liquids. The solid-liquid phase diagrams for binary mixtures composed of cholinium chloride and ten organic halides were experimentally measured. Surprisingly, cholinium chloride presented, for all these systems, significant positive deviations from ideal liquid behaviour that restricted its ability to lower the melting points of these mixtures. Only for mixtures with ammonium chloride, tetramethylammonium chloride, bis(2-hydroxyethyl)dimethylammonium chloride or cholinium bromide was cholinium chloride able to significantly lower the melting point of the mixture, but without reaching values close to room temperature (298 K). For a better understanding of the results obtained, the solid-liquid phase diagrams of four alkylammonium chloride-based mixtures were experimentally assessed and used to show that these compounds are better than cholinium chloride at inducing negative deviations from ideality, leading to greater melting point depressions.