Extraction of Organic Compounds

Abstract

The separation of organic mixtures into groups of components of similar chemical type was one of the earliest applications of solvent extraction. In this chapter the term solvent is used to define the extractant phase that may contain either an extractant in a diluent or an organic compound that can itself act as an extractant. Using this technique, a solvent that preferentially dissolves aromatic compounds can be used to remove aromatics from kerosene to produce a better quality fuel. In the same way, solvent extraction can be used to produce high-purity aromatic extracts from catalytic reformates, aromatics that are essentially raw materials in the production of products such as polystyrene, nylon, and Terylene. These features have made solvent extraction a standard technique in the oil-refining and petrochemical industries. The extraction of organic compounds, however, is not confined to these industries. Other examples in this chapter include the production of pharmaceuticals and environmental processes. In these applications, solvent extraction constitutes an extraction stage during which an organic phase is in contact with an aqueous phase or another immiscible organic phase. The extract is then recovered by distillation or washing with an aqueous or organic phase. Using new solvents and having a better understanding of the chemistry involved in more specific interactions, solvent extraction has become a very interesting separation technique for high-value organic chemicals (e.g., amino acids). Furthermore, liquid extraction using two phases with very high water concentration has found applications for the separations of proteins.