Novos Processos de Separação para o Fracionamento e Purificação de Terpenos

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Liquefying flavonoids with terpenoids through deep eutectic solvent formation

Publication . Teixeira, Gabriel; Abranches, Dinis O.; Silva, Liliana P.; Vilas-Boas, Sérgio M.; Pinho, Simão; Ferreira, Ana I.M.C. Lobo; Santos, Luís M.N.B.F.; Ferreira, Olga; Coutinho, João A.P.

The formation of deep eutectic solvents (DES) is tied to negative deviations to ideality caused by the establishment of stronger interactions in the mixture than in the pure DES precursors. This work tested thymol and menthol as hydrogen bond donors when combined with different flavonoids. Negative deviations from ideality were observed upon mixing thymol with either flavone or flavanone, two parent flavonoids that only have hydrogen bond acceptor (HBA) groups, thus forming non-ionic DES (Type V). On the other hand, the menthol systems with the same compounds generally showed positive deviations from ideality. That was also the case with the mixtures containing the more complex hydroxylated flavonoid, hesperetin, which resulted in positive deviations when mixed with either thymol or menthol. COSMO-RS successfully predicted the behavior of the solid-liquid phase diagram of the studied systems, allowing for evaluation of the impact of the different contributions to the intermolecular interactions, and proving to be a good tool for the design of DES.

2022Journal article

Open access

Ionic liquids as entrainers for terpenes fractionation and other relevant separation problems

Publication . Vilas-Boas, Sérgio M.; Teixeira, Gabriel; Rosini, Sabrina Barbosa; Martins, Mónia A.R.; Gaschi, Priscilla S.; Coutinho, João A.P.; Ferreira, Olga; Pinho, Simão

This work discusses the potential of two phosphonium-based ionic liquids (ILs), [P6,6,6,14]Cl and [P6,6,6,14][(C8H17)2PO2], and one methylimidazolium-based IL, [C4mim][OAc], as entrainers in the fractionation of terpene mixtures, in the desulfurization and denitrification of fuel oils, and in the separation of aromatics from aliphatic hydrocarbons. To this aim, the activity coefficients at infinite dilution of 45 solutes were obtained by gas-chromatography in the temperature range (333.15–458.15) K. Selectivities and capacities were calculated showing that [P6,6,6,14]Cl is adequate for the fractionation of (−)-menthone/L-(−)-menthol mixture, being also a suitable option for the deterpenation of citrus essential oil, and the removal of thiophene and pyridine from aliphatic hydrocarbons. To complement the experimental measurements COSMO-RS model was tested, demonstrating good potential to screen separation agents and give insights for several important separation problems, including the removal of contaminants from fuels and the isolation, fractionation and purification of terpenes mixtures.

2021Journal article

Open access

IN PRESS - Solvent screening for the purification of monoterpenoids by countercurrent and centrifugal partition chromatography

Publication . Vilas‐Boas, Sérgio M.; Coutinho, João A.P.; Pinho, Simão; Ferreira, Olga

Countercurrent chromatography (CCC) and centrifugal partition chromatography (CPC) are efficient techniques to purify terpenoids from essential oils. These methods require suitable solvent systems for the partition between the two immiscible liquid phases. In this study, using the analytical shake-flask method, we measured the partition coefficients of three model monoterpenoids, namely carvone, eucalyptol and thymol, in 11 biphasic solvent systems, at 298.2 K. Moreover, the predictive COSMO-RS model was applied to represent the partition coefficients of data measured in this work and retrieved from the literature, the liquid–liquid equilibrium (LLE) data of three solvent families suitable for CCC/CPC separations (i.e., Arizona, Modified Arizona and Green Arizona) and the solute's partition coefficients in the three solvent families. RESULTS: The partition coefficients obtained for thymol and eucalyptol are the first partition data available in the literature. The obtained root mean square deviations (RMSDs) between the experimental and predicted partition coefficients (log basis) varied between 0.28 and 0.49. For LLE, RMSDs of 0.040 and 0.048 were achieved for the Arizona and Green Arizona families, respectively. CONCLUSION: The predictive COSMO-RS model describes the monoterpenoid partition coefficients and the LLE data of the solvent families well. The most favorable solvent systems to perform the separations were identified, showing that systems with low and intermediate-to-low polarities are the most promising options for separating the selected monoterpenoids from their natural matrices by CCC/CPC techniques.

2024Journal article

Restricted access

Infinite dilution activity coefficients in the smectic and isotropic phases of Tetrafluoroborate-based ionic liquids

Publication . Martins, Mónia A.R.; Vilas-Boas, Sérgio M.; Cordova, Isabella Weber; Carvalho, Pedro J.; Domańska, Urszula; Ferreira, Olga; Coutinho, João A.P.; Pinho, Simão

Inverse gas chromatography was used to obtain the activity coefficients at infinite dilution (γ13∞) of several organic solutes and water in the thermotropic ionic liquid crystal phases of both [C12mim][BF4] and [C14mim][BF4] and their isotropic phases. In the smectic to isotropic transition, a change in the linear representation of the natural logarithm of γ13∞ with the reciprocal temperature was observed for [C14mim][BF4], and was more evident for alkanes, alkylbenzenes, esters, and alcohols, that can be related to structural modifications of the stationary phase. Results are interpreted in terms of the enthalpic and entropic contributions of solute-IL interactions. Selectivities and capacities of important separation problems, such as octane/benzene and cyclohexane/benzene, were calculated and compared with literature values for separating agents such as N-methyl-2-pyrrolidinone, sulfolane, and ionic liquids presenting the [BF4]- anion combined with several imidazolium-based cations. It is shown that to achieve maximum separation efficiency, imidazolium cations with short alkyl chain lengths such as [C2mim][BF4] should be used, whereas high capacities require larger alkyl chain lengths.

2021Journal article

Open access

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

Publication . Ferreira, Ana I.M.C. Lobo; Vilas-Boas, Sérgio M.; Silva, Rodrigo M.A.; Martins, Mónia A.R.; Abranches, Dinis O.; Paz, Filipe A. Almeida; Ferreira, Olga; Pinho, Simão; Santos, Luís M.N.B.F.; Coutinho, João A.P.

The importance of choline chloride (ChCl) is recognized due to its widespread use in the formulation of deep eutectic solvents. The controlled addition of water in deep eutectic solvents has been proposed to overcome some of the major drawbacks of these solvents, namely their high hygroscopicities and viscosities. Recently, aqueous solutions of ChCl at specific mole ratios have been presented as a novel, low viscous deep eutectic solvent. Nevertheless, these proposals are suggested without any information about the solid–liquid phase diagram of this system or the deviations from the thermodynamic ideality of its precursors. This work contributes significantly to this matter as the phase behavior of pure ChCl and (ChCl + H2 O) binary mixtures was investigated by calorimetric and analytical techniques. The thermal behavior and stability of ChCl were studied by polarized light optical microscopy and differential scanning calorimetry, confirming the existence of a solid–solid transition at 352.2 0.6 K. Additionally, heat capacity measurements of pure ChCl (covering both ChCl solid phases) and aqueous solutions of ChCl (xChCl o 0.4) were performed using a heat-flow differential scanning microcalorimeter or a high- precision heat capacity drop calorimeter, allowing the estimation of a heat capacity change of (ChCl) E 39.3 10 J K 1 mol 1 , between the hypothetical liquid and the observed crystalline phase at 298.15 K. The solid–liquid phase diagram of the ChCl + water mixture was investigated in the whole concentration range by differential scanning calorimetry and the analytical shake-flask method. The phase diagram obtained for the mixture shows an eutectic temperature of 204 K, at a mole fraction of choline chloride close to xChCl = 0.2, and a shift of the solid–solid transition of ChCl–water mixtures of 10 K below the value observed for pure choline chloride, suggesting the appearance of a new crystalline structure of ChCl in the presence of water, as confirmed by X-ray diffraction. The liquid phase presents significant negative deviations to ideality for water while COSMO-RS predicts a near ideal behaviour for ChCl.

2022Journal article

Open access