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Enantiomers separation by simulated moving bed chromatography. Non-instantaneous equilibrium at the solid-fluid
D C Azevedo1, L S Pais, A E Rodrigues
1Laboratory of Separation and Reaction Engineering, School of Engineering, University of Porto Rua dos Bragas, Portugal.
Journal of Chromatography. A
|February 16, 2000
Summary
Simulated Moving Bed (SMB) technology is crucial for pharmaceutical separations. This study shows that non-equilibrium adsorption kinetics significantly impact SMB unit performance, affecting product purity and recovery.
Area of Science:
- Chemical Engineering
- Separation Science
- Pharmaceutical Technology
Background:
- Simulated Moving Bed (SMB) technology, initially for petrochemicals, is increasingly vital in pharmaceutical fine chemical separations.
- Traditional SMB design often assumes instantaneous equilibrium at the solid-fluid interface, potentially leading to inaccuracies.
Purpose of the Study:
- To model, simulate, and design a SMB plant for binary chiral mixture separation.
- To investigate the impact of non-equilibrium adsorption kinetics on SMB performance.
Main Methods:
- Utilized the equivalent true moving bed (TMB) model with axial dispersion for fluid flow and plug flow for solid-phase flow.
- Incorporated first-order kinetics of adsorption, considering linear, Langmuir, and modified Langmuir equilibria.
- Described intraparticle diffusion using a linear driving force (LDF) approximation.
Main Results:
- Simulation results demonstrated that equilibrium is not always reached at the adsorbent surface under specific conditions.
- Non-equilibrium effects led to different product purities and recoveries compared to equilibrium-assumption predictions.
- Overlooking non-equilibrium kinetics can result in improper SMB unit design using standard methods.
Conclusions:
- First-order adsorption kinetics significantly influence SMB performance in chiral separations.
- Accurate SMB design requires accounting for non-equilibrium adsorption phenomena.
- The study highlights the limitations of equilibrium-based assumptions in SMB process design for pharmaceuticals.