Optimisation de la cristallisation d'un sel diastéréoisomère lors d'une résolution optique en réacteur fermé, et développement d'un mode de cristallisation continu

Abstract : The R enantiomer (target enantiomer) of the racemic mixture of an organic molecule is isolated by a preferential crystallization of the salt it forms by association with the enantiomerically pur acid R-acetyl(L)valine. The S enantiomer (counter enantiomer) may somehow also crystallize under the form a R-acetyl(L)valinate salt. Solubilities of the two salts are measured by cooling crystallizations in a batch reactor, carried out for various stoechiometric conditions. The interpretation and the modelisation of the experimental data gathered lead to the maximisation of the quantity of R enantiomer crystallized as a pur salt in a batch reactor by cooling crystallization to a given temperature. This temperature is then increased : the filtration duration of the crystals, always exhibiting the shape of needles, is thus advantageously decreased. A further decrease is made possible by applying a temperature cooling profile that promotes the growth of crystals. Finally, the enhancement of the filterability of crystals is correlated to an increase of the elongation factor of crystals. The crystallization is then transposed to a continuous operating mode : reactants are injected separately in a continuous stirred tank reactor. With a view to match the results of the optimized batch reactor, the residence time and the R-acetyl(L)valine concentration are adjusted : a better productivity is then obtained, though filterability remains lower. The elongation factor is slightly increased by implementing two continous stirred tank in serie. The complete range of possible enhancements of crystals morphology by such cascades could be further studied for such needle-like crystals
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Lionel Lerond. Optimisation de la cristallisation d'un sel diastéréoisomère lors d'une résolution optique en réacteur fermé, et développement d'un mode de cristallisation continu. Autre. Institut National Polytechnique de Lorraine, 2008. Français. ⟨NNT : 2008INPL092N⟩. ⟨tel-01753009⟩

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