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 (NaClO 3) crystals in isothermal conditions. The results demonstrate that high intensity, low frequency ultrasound can achieve efficient grinding of enantiomorphous NaClO 3 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 on 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, further increase in the enantiomeric excess was hindered after prolonged times of ultrasonication. This ensues probably due to the absence of crystal sizeinduced 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.

Crystallization is an important and widely used separation technique in the chemical and pharmaceutical industry. Control of the final particle properties is of great importance for these industries. The application of ultrasound in these crystallization processes, also referred to as sonocrystallization, has shown to impact nucleation, crystal growth and fragmentation. As a result this technology has potential to control the final particle size, shape and polymorphic form.This review provides a comprehensive overview of the recent advances in sonocrystallization. It reviews the observed effects of ultrasound on the different stages of the crystallization process. Recent insights in the mechanism behind these effects are discussed as well. Finally, guidelines for the operating conditions, such as ultrasonic frequency, power, type of cavitation bubbles, time window and moment of application are formulated.

Rapid cooling and microwave heating substantially speed up temperature cycling-enhanced deracemization, while limiting the concomitant side reactions. During fast cooling, secondary nucleation is shown to enable deracemization.

In this study, we report on experiments designed to deconvolute the particle breakage kinetics and mechanism from the parallel phenomena (growth-dissolution, agglomeration) in attrition

We investigate the existence of specific/nonthermal microwave effects for the dehydration reaction of xylose to furfural in the presence of NaCl. Such effects are reported for sugars dehydration reactions in several literature reports. To this end, we adopted three approaches that compare microwave‐assisted experiments with a) conventional heating experiments from the literature; b) simulated conventional heating experiments using microwave‐irradiated silicon carbide (SiC) vials; and at c) different power levels but the same temperature by using forced cooling. No significant differences in the reaction kinetics are observed using any of these methods. However, microwave heating still proves advantageous as it requires 30 % less forward power compared to conventional heating (SiC vial) to achieve the same furfural yield at a laboratory scale.