Browsing by Author "Costa, Mariana C."
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- Deterpenation of citrus essential oil via extractive distillation using imidazolium-based ionic liquids as entrainersPublication . Vilas-Boas, Miguel; Batista, Fábio R.M.; Dias, Rafael M.; Coutinho, João A.P.; Ferreira, Olga; Costa, Mariana C.; Pinho, SimãoThe deterpenation of citrus essential oils (CEO) is crucial in many industries to promote the stability and preserve the organoleptic properties of the final product, improving considerably the oxygenated fraction purity. Methods: Two imidazolium ionic liquids (ILs), [C4mim][OAc] and [C4mim]Cl, were applied as novel separation agents in a deterpenation process constituted by an extractive distillation column and a flash separator unit, aiming to remove hydrocarbon terpenes from the essential oil. The CEO was modeled as a mixture of the commonly found limonene (monoterpene) and linalool (monoterpenoid). To support the process simulation, isobaric vapor-liquid equilibrium measurements were conducted for the binary limonene/linalool and ternary limonene/linalool/IL mixtures at 5 kPa, and the data were successfully correlated with the NRTL model. Significant findings: The simulation results demonstrate that [C4mim]Cl improved the purity of linalool in the final product. Moreover, both [C4mim]Cl and [C4mim][OAc] reduced the required stages in the distillation column to obtain a terpeneless CEO with a certain purity, [C4mim]Cl being the most effective option.
- Flash point of binary and ternary monoterpene mixtures: experimental and modelingPublication . Vilas-Boas, Sérgio M.; Nascimento, Debora C. do; Dias, Rafael M.; Rozo, Gabriel H.; Neto, Antonio M.B.; Ferreira, Olga; Pinho, Simão; Costa, Mariana C.The flash point (FP) of pure or mixtures of flammable substances is an important indicator in designing fire risk mitigation and prevention measures in the chemical and oil industry. Although FP data of fuel constituents and blends are often found in the literature, studies addressing other flammable mixtures, such as essential oils (EOs) and their constituents (terpenes and terpenoids), are scarce. EOs are aromatic, volatile liquid mixtures extracted from plant matrices that present diverse biological properties and find numerous applications in the food, pharmaceutical, cosmetic, and fragrance industries. In this work, experimental FP measurements of binary and ternary mixtures of four structurally diverse monoterpenes (carvone, eucalyptol, limonene, and linalool), widely found in different EO profiles, were carried out. Besides, the Liaw-UNIFAC model and the COSMO-RS model were used to calculate the FP data of the studied mixtures, resulting in global root-mean-square deviations (RMSD) of 2.0 K and 0.7 K, respectively. Both models deliver better predictions than the ideal approach (RMSD = 2.4 K) for the studied systems, demonstrating the importance of considering nonideal effects when estimating the FP data of terpene mixtures. These results provide essential information for accurate process safety and fire risk assessment in the EO industry.
- Octanol–water partition coefficients and aqueous solubility data of monoterpenoids: experimental, modeling, and environmental distributionPublication . Vilas-Boas, Sérgio M.; Costa, Mariana C.; Coutinho, João A.P.; Ferreira, Olga; Pinho, SimãoTerpenes and terpenoids encompass one of the most extensive and valuable classes of secondary metabolites. Their ten-carbon-containing oxygenated representatives, monoterpenoids, are the main components of plant essential oils, being widely exploited in the cosmetic, pharmaceutical, and food industrial areas. Due to its widespread use, it is crucial to investigate their environmental distribution. Thus, new water solubility data were obtained for six monoterpenoids ((1R)-(+)-camphor, (S)-(+)-carvone, eucalyptol, (1R)- (−)-fenchone, L-(−)-menthol, and (−)-menthone) at 298.2 and 313.2 K. Furthermore, octanol−water partition coefficients of 12 monoterpenoids (the six mentioned above plus carvacrol, (±)-β-citronellol, eugenol, geraniol, linalool, and thymol) were measured at 298.2 K. The COSMO-RS thermodynamic model and other more empirical approaches were evaluated for the description of the solubilities and partition coefficients, showing reliable predictions. Lastly, the distribution of the monoterpenoids in the different environmental compartments was assessed through an intuitive two-dimensional chemical space diagram based on the physicochemical equilibrium information reported.
- Surface crystallization of ionic liquid crystalsPublication . Martins, Mónia A.R.; Carvalho, Pedro J.; Alves, Douglas; Dariva, Cláudio; Costa, Mariana C.; Ferreira, Rute A.S.; André, Paulo S.; Morgado, Pedro; Pinho, Simão; Filipe, Eduardo J.M.; Coutinho, João A.P.The evidence for surface crystallization in ionic liquids is scarce. The existing reports seem to be contradictory as for its driving forces, since in the two compounds investigated in the literature, the contribution of coloumbic and van der Waals forces is very different. In this work 1-dodecyl-3- methylimidazolium tetrafluoroborate was studied and its surface crystallization characterized by surface tension, ellipsometry and optical microscopy. The results obtained seem to reconcile previous observations, and it was further shown, using the same techniques, that this phenomenon is prevalent in other ionic liquids. MD simulation results illustrate the different possibilities of organization, providing reasonable models to rationalize the experimental observations.