Multistage enantioselective reactive extraction of terbutaline enantiomers by hydrophobic phase transfer: Experiment and modeling

摘要

Terbutaline (TBTL) sulfate is hardly dissolved in organic solution, which made the enantioselective extraction of TBTL enantiomers by hydrophilic chiral extractant nearly impossible. In this paper, a phase transfer agent, sodium tetraphenylborate (NaTPB) was added to the multistage extraction system. TBTL cationic distributes in the organic phase through formation of an ion pair complex with NaTPB, which made the extraction of TBTL enantiomers possible and significantly improved the capacity of this process. TBTL enantiomers were separate by a fractional reactive extraction process performed on a cascade of centrifugal contactor separators (CCSs), where hydroxylpropyl-beta-cyclodextrin and 1-octanol were employed as the chiral selector and organic solvent, respectively. A mathematical model based on equilibrium and mass balance analysis of the process was established. Model predictions agreed well with experimental results. Conditions for symmetric separation are optimized by this model and the optimal conditions are proposed at O/W of 0.6, O/F of 4, NaTPB concentration of 0.03 mol/L, HP-beta-CD concentration of 0.1 mol/L, pH of 7 and temperature of 278 K. By modeling and optimization, the minimum stage number was 88 and 98 for ee(eq) 98% and ee(eq) 99%.