Computer-aided molecular design of optimal sustainable solvent for liquid-liquid extraction

Abstract

The selection of suitable solvents for chemical separation processes has been a challenging task as substantial amount of time and resources are required. Computer-aided molecular design (CAMD) has facilitated the search for novel solvents by providing a more efficient and systematic pathway to synthesize optimal solvents. Solvent properties such as selectivity and capacity often exhibit opposed behavior which are known as antagonistic properties. The antagonistic properties of solvent are addressed where the major highlight of this work is that a compromise between selectivity and capacity can be achieved by introducing mixture design. Hildebrand solubility parameters are introduced as screening criteria to determine the potential molecular building blocks, which possess the desired functionality and properties of solvent. UNIFAC group contribution method is implemented for the prediction of liquid-phase activity coefficient, which is equivalent to inverse of the mole fraction solubility. The increasing attention on sustainability aspects is also addressed by introducing safety and health (SE) parameters as design criteria, where index-based approach is implemented to quantify these parameters. Analytical hierarchy process (AHP) is then introduced to deal with the subjectivity in defining relative importance of these SE parameters. The mixture design problem is formulated along with SE parameters as a multi-objective optimization model where an integrated Bi-Level AHP optimization model is introduced to solve this model. A case study on the extraction of 1,2-dichloroethane from cyclohexane is studied to implement the developed CAMD framework in the search of optimal solvent for liquid-liquid extraction process.