An In-Situ Synchrotron X-ray Diffraction Tomography Study of Crystallization and Preferred Crystal Orientation in a Stirred Reactor

Abstract

A new tomographic technique, based on synchrotron X-ray diffraction, has been used to chart polymorphic content and crystallite alignment inside a model pharmaceutical reactor. This reveals complex behavior according to crystallite shape/size characteristics; in particular, stirring induces pronounced crystal zonation marked by a boundary “alignment band” in which the crystallites adopt a “stand on edge” orientation.

An investigation of crystallite alignment and polymorphic interaction of glutamic acid using an in situ synchrotron X-ray diffraction tomographic technique

“…Experiments were conducted with pure phase and mixed a/b-polymorphs using 53-75 mm crystallites, stirred at a range of speeds. The previous results [5] show clear zonation of the bpolymorph; that is, the crystallites remain in the lower part of the vessel at the lowest stirring speeds. This material then rises up the vessel, becoming more diffuse, with an increase in stirring speed.…”

“…Data were collected at an angle of 4.61. Crystallite size and stirring speed experiments were conducted using suspensions of glutamic acid in ethanol; the a-form was obtained from BDH, and the b-form was re-crystallised from this form under appropriate conditions [5]. Different size ranges were obtained by sieving, and these were verified using particle size analysis.…”

“…There have been previous in situ diffraction studies using scaleddown crystallisation reactors [3,4]. Jacques et al [5] have described a novel in situ synchrotron technique, namely tomographic energy-dispersive diffraction imaging (TEDDI), which is capable of monitoring the crystallisation and mixing of glutamic acid polymorphic crystallites in a model pharmaceutical reactor.…”

“…The results have revealed behaviour associated with parameters such as crystallite size, stirring speed, preferred orientation, and crystallisation regimes. In our previous paper [5] we described results for the bpolymorph, but here we illustrate examples from the apolymorph and mixed systems of both forms. We can show the effects of crystallite size, and also examine the results of experiments conducted with a higher resolution of scan points.…”

Space-Resolved Profiling Relevant in Heterogeneous Catalysis

“…Two diffraction methods have been reported, namely X-ray diffraction (XRD) [78][79][80][81] and energy-dispersive X-ray diffraction tomography (EXDT) or alternatively called tomographic energy dispersive diffraction imaging (TEDDI) [82][83][84][85][86], where the former uses monochromatic X-ray while the latter makes use of polychromatic X-ray radiation. Despite the fact that diffraction itself does not give element-specific information, a recent study demonstrated its capability to monitor spatial distribution of specific chemical phases by recording diffraction and fluorescence signals simultaneously, and the distribution and composition of metal oxide species in CoMo/c-Al 2 O 3 catalyst have been elucidated [87].…”