Abstract

Separation of enantiomers is a major concern in pharmaceutical industries due to the different therapeutic activities exhibited by the enantiomers. Preferential crystallization is an attractive means to separate the conglomerate-forming enantiomers. In this work, a simulation study is presented for a proposed novel preferential crystallization configuration that involves coupled plug flow crystallizers (PFCs). The PFCs are coupled through liquid phase exchange which helps the enrichment of the preferred enantiomer in the liquid phase. A set of coupled population balance equations (PBEs) are used to describe the evolution of the crystal size distribution (CSD) in the PFCs. The PBEs and the relevant mass balance equations are solved using the high-resolution finite-volume method. The simulation results predict that the proposed configuration has higher productivity compared to the currently used crystallization configurations while maintaining the same level of purity. Moreover, the effect of process variables, such as the extent of liquid phase change and the location of the PFC where liquid phase exchange occurs, are studied. The insights obtained from this simulation study will be useful in design, development, and optimization of such novel crystallization platforms.

Highlights

  • Chiral molecules or enantiomers are ubiquitous in biological systems and are of great interest to pharmaceutical, food and agrochemical industries

  • These are coupled mixed suspension mixed product removal (CPC-MSMPR) tanks [15,36], coupled preferential crystallizer (CPC) configuration that runs in batch mode [37,38] and coupled preferential crystallizer with dissolution of the counter enantiomer in one tank (CPC-D) [14]

  • The comparison of the yields obtained for single plug flow crystallizers (PFCs) and coupled PFC configurations suggest that coupling through liquid phase exchange can be beneficial in achieving higher yield

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Summary

Introduction

Chiral molecules or enantiomers are ubiquitous in biological systems and are of great interest to pharmaceutical, food and agrochemical industries. It has been shown that such a process can be applied in a continuous mixed suspension mixed product removal (MSMPR)-type configuration [16] Such combinations of solution racemization and crystallization are termed deracemization processes. Novel crystallizer configurations based on PFC through innovative process design has been proposed for the continuous separation of the conglomerate-forming enantiomers. This novel configuration involves two PFCs coupled through solid free liquid phase exchange and the crystallization of the enantiomers takes place in two crystallizers separately. Effect of various operating conditions such as amount and location of liquid exchange and seed mass has been presented as well

Available Coupled Preferential Crystallizer Configurations
Proposed Coupled PFC Configuration
Model Development
Results and Discussion
Product CSD in Coupled PFC Configuration
Comparison of Productivity and Yield
Effect of Liquid Phase Exchange Location
Effect of the Amount of Liquid Phase Exchange
Effect of Seed Mass
Conclusions
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