Phase Equilibria for extraction processes with designer solvents

In recent years, there has been an increasing concern about the effects of toxic chemicals in the environment. In response to this concern, there is a growing impetus to develop chemical manufacturing processes which can reduce or eliminate the use or generation of hazardous substances. Within this aspect of green chemistry, in this Thesis, Ionic Liquids (ILs) and Deep Eutectic Solvents (DESs) have been tested as greener alternatives in different chemical processes. In a first stage, the capability of using ILs as solvents for citrus essential oil deterpenation by liquid-liquid extraction was investigated. The liquid-liquid equilibria of ternary systems limonene + linalool + IL were determined. Results were analysed in terms of the solute distribution ratio and selectivity, allowing to draw conclusions about the influence of the structure of the ILs in these thermodynamic parameters. Experimental data were correlated by means of the NRTL and UNIQUAC equations. To evaluate the capability of some ILs to act as surfactants in Enhanced Oil Recovery, two of these salts showing surfactant behaviour were tested. Liquid-liquid equilibria of ternary systems water + IL + ndodecane were determined. Winsor Type III systems were found, and the interfacial tensions between phases were measured to prove the ability of these salts to reduce the water – oil interfacial tension. Physical and transport properties of the phases involved, such as density and viscosity, were also experimentally measured. In a last stage, an introductory study on the processing of lignocellulosic biomass with DESs was carried out. Different renewable DESs were prepared from hydrogen bond donor and hydrogen bond acceptor starting materials. Solubility tests of pine wood and wheat straw in these solvents were carried out. From the thermodynamic studies that were carried out in this Thesis, it turns out that designer solvents can be used to develop greener and/or more efficient chemical processes

Improved concentration of citrus essential oil by solvent extraction with acetate ionic liquids

© 2014. This is the accepted manuscript of the following article: Lago, S., Rodríguez, H., Arce, A., & Soto, A. (2014). Improved concentration of citrus essential oil by solvent extraction with acetate ionic liquids. Fluid Phase Equilibria, 361, 37-44. doi: 10.1016/j.fluid.2013.10.036Citrus essential oils have numerous applications in multiple sectors, including food, drink and personal care industries. Although mainly constituted by terpenes, the appealing characteristics of citrus essential oils are due to oxyterpenes and other derived oxygenated compounds. In fact, the presence of terpenes in the essential oil may lead to instability or loss of quality. Therefore, concentration of the oil in its oxyterpene compounds by removal of terpenes is desirable. The techniques currently in use for deterpenation of essential oils present a series of issues. In the search for better deterpenation processes, here the use of ionic liquids as solvents in liquid-liquid extraction is explored. In particular, the ionic liquids 1-ethyl-3-methylimidazolium acetate and 1-butyl-3-methylimidazolium acetate are investigated for their extraction of oxyterpene from a modelled citrus essential oil composed of limonene (terpene) and linalool (oxyterpene). The choice of the ionic liquids, in addition to other complementary characteristics, was based on a rationale of potential interactions that can be created preferentially with the linalool. The results show a great performance of these acetate-based ionic liquids, as compared to any other ionic or molecular solvent tested to date, for the concentration in oxyterpenes of the citrus essential oilThe authors acknowledge the Ministry of Economy and Competitiveness of Spain for financial support through project CQT2012-33359 (including European Regional Development Fund advanced funding), and through the Ramón y Cajal programme (H.R.)S