Front Velocity Modeling Approach to Column Chromatographic Characterization and Evaluation of Ketamine Enantiomers Separation with Simulated Moving Bed

摘要

Simulated Moving Bed (SMB) is an efficient compounds separation process that operates in a continuous regime and works in a countercurrent flow of solid phase. Among several applications, this process has excelled in petrochemical resolution and especially nowadays in the separation of enantiomers from racemic mixtures, which are considered difficult to separate. In this work, the new Front Velocity approach to model an SMB process was proposed. To describe the mass transfer that occurs in the chromatographic process, the front velocity approach considers that convection is the dominant phase in the solute transport along the chromatographic column. "Front Velocity" is a discrete model (steps) where flow rate determines the advancing of liquid phase through the column. The steps are advancing liquid phase and mass transfer between the liquid and solid phases, the latter in the same time interval. Thus, the experimental volumetric flow is used for discretization of the control volumes moving along the porous column with the same velocity as the liquid phase. The mass transfer was represented by two different kinetic mechanisms without (linear type) and with maximum adsorption capacity (Langmuir type). The proposed approach was studied theoretically and evaluated by comparison with experimental data of ketamine anesthetic separation in SMB. The results were also compared with the simulation model using dispersive equilibrium. In the chromatographic column characterization step the new approach was associated with R2W inverse tool to determine the lumped mass transfer parameters using only the experimental residence time of each enantiomer in the high performance liquid chromatography (HPLC) column. In the second step the mass transfer kinetic equations developed in the approach were applied in each column of the SMB process together with the values determined in the characterization of the chromatographic column, to perform the continuous separation process. The simulation results show good agreement between the modeling proposal and pulse experiments used to characterize the column in enantiomeric separation of ketamine over time. The simulations of the SMB separation show a discrepancy with the experimental data in the early cycles, but after these initial cycles, the model has good correlation with the experimental data. According to the study conducted the proposed approach proved to be a potential tool for prediction of the chromatographic behavior of a sample in a pulse experiment and to simulate the compounds separation in an SMB process despite small differences shown in the first SMB work cycles. Furthermore, the model equations can be easily implemented and applied in the analysis of the process, as it requires a small number of parameters and consists of ordinary differential equations.