A system for the design of an optimum liquid-liquid extractant molecule

Abstract The design of an extractant molecule for use in liquid-liquid extraction, traditionally a combinatorial optimization problem, has been solved using continuous optimization. The UNIFAC model was used as the basis for all calculation. A computer system was developed which employs a three-step procedure. First, the error in the liquid-liquid equilibrium relations resulting from the specification of a target separation criteria is minimized. Second, the molecule produced is used as a starting point to optimize up to seven separation criteria to obtain the theoretical extractant molecule which satisfies the equilibrium relations. Third, this molecule is used to generate alternative extractant molecules which contain integer group values only. Numeric molecular structure constraints were developed which maintain the feasibility of molecules and set limits on boiling point and molecular weight. The system was tested on several separation problems and has suggested extractants as good or better than ones currently in use.