Phase Equilibria for extraction processes with designer solvents

Abstract

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.