Direct In Situ Investigation of Milling Reactions Using Combined X‐ray Diffraction and Raman Spectroscopy

Abstract

The combination of two analytical methods including time‐resolved in situ X‐ray diffraction (XRD) and Raman spectroscopy provides a new opportunity for a detailed analysis of the key mechanisms of milling reactions. To prove the general applicability of our setup, we investigated the mechanochemical synthesis of four archetypical model compounds, ranging from 3D frameworks through layered structures to organic molecular compounds. The reaction mechanism for each model compound could be elucidated. The results clearly show the unique advantage of the combination of XRD and Raman spectroscopy because of the different information content and dynamic range of both individual methods. The specific combination allows to study milling processes comprehensively on the level of the molecular and crystalline structures and thus obtaining reliable data for mechanistic studies.

The effect of ball mass on the mechanochemical transformation of a single-component organic system: anhydrous caffeine

“…For each experiment, 300 mg of pure anhydrous caffeine powder was used. Samples were loaded into Perspex milling vessels (internal volume 14.5 mL), which have been previously demonstrated to be suitable for in situ X-ray diffraction experiments [15,16,19,46]. Jars were generated in line with the engineering specifications in [47].…”

“…These issues prompted the rapid development of techniques to probe mechanochemical reactions in situ and in real time. To date, this has been performed using X-ray powder diffraction at synchrotron sources, laboratory-based Raman spectroscopy, or a simultaneous combination of the two [3,[15][16][17][18][19]. In situ, real-time monitoring has proven a great advantage to identifying processes and control parameters in mechanochemistry.…”

Metal Phosphonates and Phosphinates

“…These do not include any MPs, but the SynRAC could easily find employment for this class of materials as well. Section 3.2 has already suggested that in situ studies can be very informative for mechanochemical syntheses [56][57][58][59]97]. The two techniques used in each of the in situ studies reported so far were XRD and Raman spectroscopy, which allow the reaction to be monitored at both molecular and crystalline levels [97].…”

“…Section 3.2 has already suggested that in situ studies can be very informative for mechanochemical syntheses [56][57][58][59]97]. The two techniques used in each of the in situ studies reported so far were XRD and Raman spectroscopy, which allow the reaction to be monitored at both molecular and crystalline levels [97]. Traditionally, the vessel used in the milling/grinding process would be lined with an abrasion-resistant material, and would contain the grinding media, which is often constructed from steel, ceramic, and other suitable materials.…”

Oscillatory combustion of propene during in situ mechanical activation of solid catalysts

“…On changing of the reactant feed composition, a change in the surface of Cr 2 O 3 under strongly oxidizing and reducing conditions was reflected by reproducible changes in CO and CO 2 product ratios. So far, the possibilities of in situ analysis during milling reactions are scarce, allowing to obtain only very little information on processes taking place during the milling, especially on the surface of the material being milled [30][31][32]. Ex situ XRD analysis showed no change in the oxidation state of the catalyst ( Supporting Information, Fig.…”