(676c) Digital Design Framework for the Continuous Crystallization of Diphenhydramine
AIChE Annual Meeting
Thursday, November 17, 2022 - 4:31pm to 5:00pm
In this work, we demonstrate the application of combined model-free quality-by-control (mfQbC) and a model-based digital design approach for the design and optimization of crystallization of Diphenhydramine (DPH). DPH is an anti-histamine commonly found in Benadryl. While the continuous synthesis of DPH has been studied by multiple research groups in the past ten years, research literature lacks information on continuous crystallization development with modeling for the compound.1â4 The PAT-based mfQbC framework implementation reduces both the number of experiments and time needed to design crystallization processes, but often results in sub-optimal crystallization design. However, we can augment the mfQbC results to guide model-based digital design, by identifying key mechanisms to be included in the model and providing high quality data for parameter estimation, which would reduce the overall crystallization development time and lead to an optimal design.5
Under the mfQBC approach, initial solvent screening experiments were conducted to guide solvent selection and gain information about the meta-stable zone width (MSZW). Preliminary batch experiments provided valuable insights about the initial parameter estimation and crystallization mechanisms for model selection and discrimination. Continuous crystallization process alternatives were screened and evaluated according to the suspension ability and degree of fouling of each configuration, in addition to product size and variability. The crystallizer configurations evaluated in this study include mixed suspension-mixed product removal (MSMPR) and continuous oscillatory baffled crystallizer (COBC). Initial parameter estimation estimates were validated in the selected configuration, and improved estimates were used for model development. Under mbQbC framework, a population balance-based model is developed for selected configuration and is used to run the simulation studies. With the selection of best crystallization system for the compound and model development in place, robust-optimization studies have been performed to identify optimal trajectories and design parameters in the design space of the system. The optimal conditions were experimentally validated to complete the cycle of designing a robust continuous crystallization system for Diphenhydramine.
Funding for this paper was made possible by the United States Food and Drug Administration.
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