Browsing by Author "Schaeffer, Nicolas"
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- Greener terpene-terpene eutectic mixtures as hydrophobic solventsPublication . Martins, Mónia A.R.; Silva, Liliana P.; Schaeffer, Nicolas; Abranches, Dinis O.; Maximo, Guilherme J.; Pinho, Simão; Coutinho, João A.P.Natural products can be the basis for the development of green solvents, relevant for the advancement of new, more sustainable processes and products. In this work, 10 binary mixtures constituted by terpenes are prepared and characterized. Their solid−liquid phase diagrams show that room-temperature solvents can be prepared from solid terpenes in a wide composition range. These diagrams are accurately described by the conductor-like screening model for real solvents, showing it to be a useful predictive tool for the design of novel natural solvents. At the eutectic point, these mixtures possess low viscosities, densities lower than water, and high boiling temperatures. The low water solubility in the eutectic solvents together with its negligible impact on the properties measured is a strong indicator of the hydrophobic character of these mixtures. The tunable character of these mixtures is demonstrated by studying the solvatochromic parameters in the entire concentration region, the properties of the final solvents being tuned by simply varying the mole fraction of the terpenes. The high potential of this tunable character is shown in the selective extraction of dyes from their aqueous solutions. This work is expected to devise new insights concerning these solvents as well as to boost their application in green industrial processes.
- Phenolic hydrogen bond donors in the formation of non-ionic deep eutectic solvents: The quest for type v desPublication . Abranches, Dinis O.; Martins, Mónia A.R.; Silva, Liliana P.; Schaeffer, Nicolas; Pinho, Simão; Coutinho, João A.P.Mixtures of non-ionic compounds have been reported as DES but most are just ideal mixtures. In the thymol-menthol system, an abnormal strong interaction was identified stemming from the acidity difference of the phenolic and aliphatic hydroxyl groups. This type of interaction is found to be the key to prepare non-ionic DES, that may be classified as type V.
- The role of charge transfer in the formation of type i deep eutectic solvent-analogous ionic liquid mixturesPublication . Abranches, Dinis O.; Schaeffer, Nicolas; Silva, Liliana P.; Martins, Mónia A.R.; Pinho, Simão; Coutinho, João A.P.It was recently shown that tetramethylammonium chloride presented negative deviations to ideality when mixed with tetraethylammonium chloride or tetrapropylammonium chloride, leading to a strong decrease of the melting points of these salt mixtures, in a behavior akin to that observed in the formation of deep eutectic solvents. To better rationalize this unexpected melting point depression between two structurally similar compounds devoid of dominant hydrogen bonding capability, new solid–liquid equilibria data for tetramethylammonium-based systems were measured and analyzed in this work. Molecular dynamics was used to show that the strong negative deviations from ideality presented by these systems arise from a synergetic share of the chloride ions. A transfer of chloride ions seems to occur from the bigger cation in the mixture (which possesses a more disperse charge) to the smaller cation (tetramethylammonium), resembling the formation of metal–chloride complexes in type I deep eutectic solvents. This rearrangement of the charged species leads to an energetic stabilization of both components in the mixture, inducing the negative deviations to the ideality observed. The conclusions presented herein emphasize the often-neglected contribution of charge delocalization in deep eutectic solvents formation and its applicability toward the design of new ionic liquid mixtures.
- Sustainable hydrophobic terpene-based eutectic solvents for the extraction and separation of metalsPublication . Schaeffer, Nicolas; Martins, Mónia A.R.; Neves, Catarina M.S.S.; Pinho, Simão; Coutinho, João A.P.Sustainable hydrophobic eutectic solvents, composed of low-priced and biodegradable terpenes and fatty acids, were used for the extraction and separation of Cu(ii) from other transition metals in mildly acidic solutions. Multiple parameters were evaluated for metal extraction and the hydrophobic eutectic solvent was successfully recovered and reused.