Study on enantioseparation of α-cyclopentyl-mandelic acid enantiomers using continuous liquid-liquid extraction in centrifugal contactor separators: Experiments and modeling

Multistage enantioselective liquid-liquid extraction (ELLE) of α­-cyclopentyl-mandelic acid (α-CPMA) enantiomers using hydroxyethyl-β-cyclodextrin (HE-β-CD) as extractant was studied in a cascade of centrifugal contactor separators (CCSs). Performance of the separation process was evaluated by enantiomeric excess (ee) and yield (Y). A multistage equilibrium model was established to predict and optimize the process. The influence of important factors on the multistage separation process, including the extract phase/washing phase ratio (W/O), the concentration of chiral selector, and the pH value of aqueous phase were investigated by experiments and modeling. It was found that the experimental results were in good agreement with the model predictions. The optimal conditions for symmetric separation involves a W/O ratio of 0.5, W/F ratio of 6, pH of 2.5, HE-β-CD concentration of 0.05 mol/L at 5 °C, where eeextract, eeraffinate, Yextract and Yraffinate can reach up to 39%, 35%, 65% and 71%, respectively. By modeling and optimization, the minimum number of stages was evaluated at 66 and 84 for eeeq > 97% and eeeq > 99% (eeeq represents equal enantiomeric excess).