SMB enantioseparation:: Process development, modeling, and operating conditions

The design of a simulated moving bed (SMB) pilot used for chiral drug separation is presented. On-line concentration measurements allow the observation of detailed concentration profiles along the SMB columns. Based on an extensive set of experimental data, an equivalent countercurrent model was derived. In this model, mass-transfer kinetics are described by linear driving-force models, while the equilibrium concentrations are given by modified competitive Langmuir isotherms. The isotherm parameters are estimated using a peak fitting procedure, which starts with initial values given by a simple retention-time method. The dispersion phenomena are estimated through the variation of the HETP with the fluid-phase velocity. The good agreement between the model and the real system is demonstrated by several cross-validation results corresponding to the separation of given racemic mixtures under various operating conditions. The model defines a zone of complete separation and allows optimal operating conditions to be selected.