Percorrer por autor "Neves, Catarina M.S.S."
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- Analysis of the isomerism effect on the mutual solubilities of bis(trifluoromethylsulfonyl)imide-based ionic liquids with waterPublication . Martins, Mónia A.R.; Neves, Catarina M.S.S.; Kurnia, Kiki A.; Santos, Luís M.N.B.F.; Freire, Mara G.; Pinho, Simão; Coutinho, João A.P.The knowledge of the liquid-liquid equilibria (LLE) between ionic liquids (ILs) and water is of utmost importance for environmental monitoring, process design and optimization. Therefore, in this work, the mutual solubilities with water, for the ILs combining the 1-methylimidazolium, [C(1)im](+); 1-ethylimidazolium, [C(2)im](+); 1-ethyl-3-propylimidazolium, [C(2)C(3)im](+); and 1-butyl-2,3-dimethylimidazolium, [C(4)C(1)C(1)im](+) cations with the bis(trifluoromethylsulfonyl)imide anion, were determined and compared with the isomers of the symmetric 1,3-dialkylimidazolium bis(trifluoromethylsulfonyl)imide ([C(n)C(n)im][NTf2], with n=1-3) and of the asymmetric 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C(n)C(1)im][NTf2], with n = 2-5) series of ILs. The results obtained provide a broad picture of the impact of the IL cation structural isomerism, including the number of alkyl side chains at the cation, on the water-IL mutual solubilities. Despite the hydrophobic behaviour associated to the [NTf2](-) anion, the results show a significant solubility of water in the IL-rich phase, while the solubility of ILs in the water-rich phase is much lower. The thermodynamic properties of solution indicate that the solubility of ILs in water is entropically driven and highly influenced by the cation size. Using the results obtained here in addition to literature data, a correlation between the solubility of [NTf2]-based ILs in water and their molar volume, for a large range of cations, is proposed. The COnductor like Screening MOdel for Real Solvents (COSMO-RS) was also used to estimate the LLE of the investigated systems and proved to be a useful predictive tool for the a priori screening of ILs aiming at finding suitable candidates before extensive experimental measurements.
- Densities, viscosities and derived thermophysical properties of water-saturated imidazolium-based ionic liquidsPublication . Martins, Mónia A.R.; Neves, Catarina M.S.S.; Kurnia, Kiki A.; Carvalho, Pedro J.; Rocha, Marisa A.A.; Santos, Luís M.N.B.F.; Pinho, Simão; Freire, Mara G.In order to evaluate the impact of the alkyl side chain length and symmetry of the cation on the thermophysical properties of water-saturated ionic liquids (ILs), densities and viscosities as a function of temperature were measured at atmospheric pressure and in the (298.15 to 363.15) K temperature range, for systems containing two series of bis(trifluoromethylsulfonyl)imide-based compounds: the symmetric [C n C n im][NTf2] (with n = 1-8 and 10) and asymmetric [C n C1im][NTf2] (with n = 2-5, 7, 9 and 11) ILs. For water-saturated ILs, the density decreases with the increase of the alkyl side chain length while the viscosity increases with the size of the aliphatic tails. The saturation water solubility in each IL was further estimated with a reasonable agreement based on the densities of water-saturated ILs, further confirming that for the ILs investigated the volumetric mixing properties of ILs and water follow a near ideal behaviour. The water-saturated symmetric ILs generally present lower densities and viscosities than their asymmetric counterparts. From the experimental data, the isobaric thermal expansion coefficient and energy barrier were also estimated. A close correlation between the difference in the energy barrier values between the water-saturated and pure ILs and the water content in each IL was found, supporting that the decrease in the viscosity of ILs in presence of water is directly related with the decrease of the energy barrier.
- Impact of the cation symmetry on the mutual solubilities between water and imidazolium-based ionic liquidsPublication . Martins, Mónia A.R.; Neves, Catarina M.S.S.; Kurnia, Kiki A.; Luís, Andreia; Santos, Luís M.N.B.F.; Freire, Mara G.; Pinho, Simão; Coutinho, João A.P.Aiming at the evaluation of the impact of the ionic liquids (ILs) cation symmetry on their phase behaviour, in this work, novel mutual solubilities with water of the symmetric series of [C(n)C(n)im][NTf2] (with n=1-5) were determined and compared with their isomeric forms of the asymmetric [C(n)C(1)im][NTf2] group. While the solubility of isomeric ILs in water was found to be similar, the solubility of water in ILs follows the same trend up to a maximum cation alkyl side chain length. For n >= 4 in [C(n)C(n)im][NTf2] the solubility of water in the asymmetric ILs is slightly higher than that observed in the symmetric counterparts. The thermodynamic properties of solution and solvation derived from the experimental solubility data of ILs in water at infinite dilution, namely the Gibbs energy, enthalpy and entropy were used to evaluate the cation symmetry effect on the ILs solvation. It is shown that the solubility of ILs in water is entropically driven and highly influenced by the cation size. Accordingly, it was found that the ILs solubility in water of both symmetric and asymmetric series depends on their molecular volume. Based on these findings, a linear correlation between the logarithm of the solubility of ILs in water and their molar volume is here proposed for the [NTf2]-based ILs at a fixed temperature.
- Measurement and PC-SAFT modeling of solid-liquid equilibrium of deep eutectic solvents of quaternary ammonium chlorides and carboxylic acidsPublication . Pontes, Paula V.A.; Crespo, Emanuel A.; Martins, Mónia A.R.; Silva, Liliana P.; Neves, Catarina M.S.S.; Maximo, Guilherme J.; Hubinger, Miriam Dupas; Batista, Eduardo A.C.; Pinho, Simão; Coutinho, João A.P.; Sadowski, Gabrielle; Held, ChristophIn this study the solid-liquid equilibria (SLE) of 15 binary mixtures composed of one of three different symmetrical quaternary ammonium chlorides and one of five different fatty acids were measured. The experimental data obtained showed extreme negative deviations to ideality causing large melting-temperature depressions (up to 300 K) that are characteristic for deep eutectic systems. The experimental data revealed that cross-interactions between quaternary ammonium salt and fatty acid increase with increasing alkyl chain length of the quaternary ammonium chloride and with increasing chain length of the carboxylic acid. The pronounced decrease of melting temperatures in these deep eutectic systems is mainly caused by strong hydrogen-bonding interactions, and thermodynamic modeling required an approach that takes hydrogen bonding into account. Thus, the measured phase diagrams were modeled with perturbed-chain statistical associating fluid theory based on the classical molecular homonuclear approach. The model showed very good agreement with the experimental data using a semi-predictive modeling approach, in which binary interaction parameters between quaternary ammonium chloride and carboxylic acid correlated with chain length of the components. This supports the experimental findings on the phase behavior and interactions present in these systems and it allows estimating eutectic points of such highly non-ideal mixtures.
- Solid + liquid equilibria and molecular structure studies of binary mixtures for nitrate ester's stabilizers: Measurement and modelingPublication . Chelouche, Salim; Trache, Djalal; Neves, Catarina M.S.S.; Pinho, Simão; Khimeche, Kamel; Benziane, MokhtarSolid-liquid equilibria (SLE) data for two binary organic mixtures of N-(2-methoxyethyl)-p-nitroaniline+Nethyl- 4-nitroaniline (S1) and N-(2-ethanol)-p-nitroaniline+N-ethyl-4-nitroaniline (S2) have been measured using differential scanning calorimeter to build the corresponding solid-liquid phase diagrams. The quality of the SLE data has been checked by consistency tests, presenting good quality factors for both systems. Simple eutectic behavior has been observed for these systems with the presence of a solid-solid transition for S2. The SLE data have been correlated by means of Wilson, NRTL, and UNIQUAC equations. The used models calculate the equilibrium temperatures very satisfactorily. The best modeling results were obtained using the Wilson equation with a root mean square deviation between experimental and calculated values for S1 and S2 of 1.15 and 1.99, respectively. The Wilson, NRTL, and UNIQUAC equations have also been used to compute excess thermodynamic functions viz. excess Gibbs energy, enthalpy, and entropy. The obtained results demonstrated a moderate positive deviation to ideality for S1, and a strong positive deviation for S2, unveiling the nature of the interactions between the compounds forming each mixture. In addition, microstructural studies have been carried out by FTIR, XRD and optical microscopy. Weak molecular interactions have been shown for the eutectic compositions. Jackson’s roughness parameter was calculated and found to be greater than 2, suggesting the faceted morphology with irregular structures.
- 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.