Coupling reaction and crystallization processes

Often crystallization is used at the end of a reaction-separation process chain to finally produce the solid product. However exploiting its inherent high selectivity at an earlier stage offers advantages. For example, the direct integration of crystallization within a synthesis reaction chain can benefit from circumventing reaction equilibria constraints, increasing selectivity, simplifying downstream processing and providing the target compound straightly as a solid product with desired solid-state properties. Within the last years, several processes combining a reactive and a crystallization step were studied in our group; two examples are presented below.

Racemization and Crystallization

Coupling selective crystallization with racemization of the unwanted enantiomer enables significant increases in yields of enantiomer separation processes. An example investigated refers to a complete chiral inversion of an amino acid enantiomer by coupling preferential crystallization with enzymatic racemization in a continuous process mode. It is based on utilization of fluidized bed crystallizers applied for separation of racemic mixtures of two amino acids and an API compound in previous studies. The technology allows for producing both enantiomer crystals simultaneously at high purity, narrow crystal size distribution and significant productivity, and the processability of systems with needle-shaped crystals [1-4]. Coupling it with an upstream racemization in a fixed-bed reactor has been shown to enable a robust enantioselective crystallization and a high driving force for racemization (see Figure below). Based on detailed process modeling and rational design experimental validation of the full process was performed successfully at pilot-plant scale disclosing remarkable continuous chiral inversion rates of ~25 g/L/h and enantiomer purities >98% [5].

 

 

 

 

 

 

 

[1]    Gänsch, J., Huskova, N., Kerst, K., Temmel, E., Lorenz, H., Mangold, M., Janiga, G., Seidel-Morgenstern, A.: Continuous enantioselective crystallization of chiral compounds in coupled fluidized beds. Chem. Eng. J. 422 (2021) 129627

[2] Bhandari, S., Carneiro, T., Lorenz, H., Seidel-Morgenstern, A.: Shortcut model for batch preferential crystallization coupled with racemization for conglomerate-forming chiral systems. Cryst. Growth Des. 22 (2022), pp. 4094–4104

[3] Huskova, N., Gänsch, J., Mangold, M., Lorenz, H., & Seidel-Morgenstern, A.: Improving results of a continuous fluidized bed process for the separation of enantiomers by applying mathematical optimization. Comp. Aided Chem. Eng. 52 (2023), pp. 1391-1396

[4] Gänsch, J., Gamm, I., Seidel-Morgenstern, A., Lorenz, H.: Applicability of fluidized bed crystallization for separation of enantiomers forming needle-shaped crystals. Submitted

[5]    Gänsch, J., Oliynyk, K., Potharaju, S., Seidel-Morgenstern, A., Lorenz, H.: Continuous chiral inversion by coupling enzymatic racemization with enantioselective fluidized bed crystallization. Ind. Eng. Chem. Res. 63 (2024), pp. 18525–18535

 

Reactive absorption and crystallization

The “CODA – Carbon-negative sODA ash plant” project, granted from the BMBF, is devoted to develop a completely new process concept for production of sodium carbonate, i.e. to replacing the classical Solvay-process that uses fossile carbon from CaCO₃, natural gas & coal as energy inputs and emits CO₂, NH₃, and solid and liquid waste streams as well. The new process concept is illustrated in the Figure below. It is based on usage of natural halite brine, CO₂ from air and renewable energy in a process combination of 1) electrolysis for generation of a NaOH solution (not studied in the project), 2) reactive absorption of CO₂ to convert the latter in a sodium carbonate solution and 3) crystallization to generate the desired dense soda ash product. As a result, in a completely electrified process, soda ash, hydrogen and chlorine (or HCl) and CO₂ depleted air are produced. Within the project, after detailed studies of the CO₂ absorption process [1-4], several strategies for direct coupling CO₂ absorption with crystallization of the Na₂CO₃ hydrate phases to produce soda ash in a continuous process mode were developed. Process modelling comprised a production rate of 1000 t/d soda ash; successful basic experimental validation was performed in a small pilot-scale. Publication of the final results is in progress.

[1]    Ghaffari, S., Gutierrez, M. F., Seidel-Morgenstern, A., Lorenz, H. and Schulze, P.: Sodium hydroxide-based CO2 direct air capture for soda ash production – Fundamentals for process engineering. Ind. Eng. Chem. Res. 62 (2023), pp. 7566–7579

[2]    Gutierrez, M., Schulze, P., Seidel-Morgenstern, A., Lorenz, H: Parametric study of the reactive absorption of CO2 for soda ash production. Comp. Aided Chem. Eng. 52 (2023), pp. 2935-2940

[3]    Vhora, K., Janiga, G., Lorenz, H., Seidel-Morgenstern, A., Gutierrez, M. F., Schulze, P.:
Comparative study of droplet diameter distribution: Insights from experimental imaging and CFD simulations. Appl. Sci., 14 (2024) 1824

[4]    Gutierrez, M.F., Vhora, K., Ghaffari, S., Janiga, G., Seidel-Morgenstern, A., Lorenz, H. and Schulze, P.: Experimental study and modeling of a droplet CO2 absorber for the carbon-negative soda ash production. Chem. Eng. Sci., accepted

 

Further publications

Tenberg, V., Schultheis, A., Rihko-Struckmann, L., Sundmacher, K. and Lorenz, H.: Purification of ε-caprolactam monomers via crystallization from a depolymerization reaction mixture – Fundamentals and potential separation strategies. Chem. Ing. Tech., accepted

Tenberg, V., Sadeghi, M., Schultheis, A., Joshi, M., Stein, M., Lorenz, H.: Aqueous solution and solid-state behavior of L-homophenylalanine: Experiment, modelling, and DFT calculations. RSC Adv. 14 (2024), pp. 10580–10589

Intaraboonrod, K., Harriehausen, I., Carneiro, T., Seidel-Morgenstern, A., Lorenz, H. & Flood, A.: Temperature cycling induced deracemization of DL-asparagine monohydrate with immobilized amino acid racemase. Cryst. Growth Des. 21 (2021) pp. 306–313

Intaraboonrod, K., Seidel-Morgenstern, A., Lorenz, H. & Flood, A.: Efficient conversion of threonine to allo-threonine using immobilized amino acid racemase and temperature cycles. Cryst. Growth Des. 21 (2021), pp. 5641–5650

Albis, A., Jiménez, Y.P., Graber, T.A., Lorenz. H.: Reactive crystallization kinetics of K2SO4 from picromerite-based MgSO4 and KCl. Crystals 11 (2021), 1558

Tortora, C., Mai, C., Cascella, F., Mauksch, M., Seidel-Morgenstern, A., Lorenz, H., Tsogoeva, S. B.: Speeding up Viedma Deracemization through water catalyzed and reactant self-catalyzed racemization. ChemPhysChem 21 (2020), pp. 1775–1787

Carneiro, T., Wrzosek, K., Bettenbrock, K., Lorenz, H., Seidel-Morgenstern, A.: Immobilization of an amino acid racemase for application in crystallization-based chiral resolutions of asparagine monohydrate. Eng Life Sci. 20 (2020) pp. 550–561