Attrition-enhanced deracemization of NaClO3: comparison between ultrasonic and abrasive grinding

Christos Xiouras, Jasper Van Aeken, Joris Panis, Joop H. Ter Horst, Tom Van Gerven, Georgios D. Stefanidis

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Abstract

Ultrasound-enhanced grinding is a more practical alternative to glass bead-enhanced grinding for performing attrition-enhanced deracemization at large scale or in continuous flow. In this work, both ultrasound-enhanced grinding (41.2 kHz) and glass bead-enhanced grinding were applied to induce Viedma deracemization of sodium chlorate (NaClO3) crystals in isothermal conditions. The results demonstrate that high intensity, low frequency ultrasound can achieve efficient grinding of enantiomorphous NaClO3 crystals, producing small crystal size and narrow size distribution, both being highly desirable final product properties. Monitoring the width of the crystal size distribution reveals its crucial role and offers further insight into the underlying phenomena in the deracemization process. Compared to glass bead-enhanced grinding, ultrasound-enhanced grinding resulted in faster crystal size reduction and rapid initial deracemization. However, a further increase in the enantiomeric excess was hindered after prolonged times of ultrasonication. This ensues probably due to the absence of crystal size-induced solubility gradients, owing to the existence of close to monodispersed sized crystals after the initial stage in the ultrasound-enhanced grinding process. We show that this can be overcome by combining (a) ultrasound with glass beads or (b) ultrasound with seeding, both of which led to enantiopurity.

Original languageEnglish
Pages (from-to)5476-5484
Number of pages9
JournalCrystal Growth and Design
Volume15
Issue number11
Early online date22 Oct 2015
DOIs
Publication statusPublished - 4 Nov 2015

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Keywords

  • ultrasound-enhanced grinding
  • glass-bead enhanced grinding
  • crystal size distribution
  • deracemization

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