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Teses de Mestrado ESTiG

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Browsing Teses de Mestrado ESTiG by Author "Abdelhak, Alilat"

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  • PEGs in the fractionation of terpenes from lemon essential oil
    Publication . Abdelhak, Alilat; Ferreira, Olga; Pinho, Simão; Martins, Mónia A.R.; Boudina, Mohamed
    The main objective of this work is to study the potential use of polyethylene glycol 400 (PEG400) as a mass separation agent in the fractionation of terpenes that compose several essential oils, including citrus oils. Both terpenes and their oxygenated derivatives (terpenoids) are common ingredients in fragrances, pharmaceuticals, food additives, polymers, biofuels and fine-chemical products. Though limited information exists on the application of PEGs for this purpose, these polymers are also already used in the cosmetics and pharmaceutical areas. To achieve this, the infinite dilution activity coefficients of 38 solutes (water, alkanes, cycloalkanes, ketones, ethers, cyclic ethers, esters, alcohols, and 16 terpenes and terpenoids) were measured in polyethylene glycol 400 by inverse gas chromatography in the interval of 60°C to 120 °C. This technique is very useful and cost-effective to do a preliminary solvent screening, allowing the calculation of several separation parameters such as selectivities, capacities and solvent performance indices (Qij), which are key values to design a separation process. In general, alkanes, cycloalkanes, hydrocarbon terpenes and terpenoids presented the highest activity coefficients, with positive deviations to ideality. On the other hand, water and most alcohols with less than 4 carbon atoms presented activity coefficients lower than 1. Among the binary mixtures of terpenes studied (limonene + carvone, limonene + linalool, menthone + menthol, borneol + camphor, -pinene + -pinene, α-pinene + limonene, and pcymene + limonene), satisfactory results were obtained only for the mixtures limonene + linalool and limonene + carvone, with Qij of 1.5 and 2.4, respectively. For the remaining ones, the low capacities of the solutes resulted in Qij lower than 1. As expected, the separation of mixtures containing two hydrocarbon terpenes is the most difficult. Nevertheless, for the mixtures -pinene/-pinene and p-cymene/limonene, satisfactory selectivities of 1.3 were obtained. Future studies with PEGs of different molecular weights or end chains may allow to modulate the polarity and improve the solubility of both terpenes and terpenoids in the solvent.
    2024Master thesis Restricted access Show more