Continuous scalable Grignard reagent formation: Process intensification and improved selectivity in non-homogeneous packed beds of magnesium turnings

Thumbnail Image

Files

Dissertation_EvaDeitmann.pdf (53.91 MB)

Date

2024-06-18

Authors

Deitmann, Eva Pauline

Journal Title

Journal ISSN

Volume Title

Publication Type

Dissertation

DOI

https://doi.org/10.18725/OPARU-53072

Published in

Abstract

Grignard reagents are organometallic halides that are important in synthetic chemistry due to their ability to form carbon-carbon bonds with electrophilic substrates in the subsequent Grignard reaction. However, the formation of Grignard reagents presents several challenges, including variable incubation periods, high exothermicity, potentially excessive side product formation and its sensitivity to oxygen and moisture. Due to these challenges, Grignard reagent formation has the potential to benefit from flow chemistry and a continuous production process. The aim of this dissertation is to enhance the benefits of a continuous synthesis process for the formation of Grignard reagents and to expand the utilization to increase the process safety, improve the product quality and achieve scalability for production flexibility. To evaluate the potential of infrared spectroscopy as a process analytical technique for the identification and quantification of Grignard reagents, a literature review was conducted on the specific absorption bands of Grignard reagents and existing application examples. Based on the obtained findings, infrared spectroscopy was used in the further course of the work, e.g., to perform residence time distribution measurements. Narrow residence time distributions in non-homogeneous, randomly packed beds of non-uniform, non-spherical magnesium turnings can be obtained by decreasing the size of the magnesium turnings and increasing the packing density. The residence time distributions were also found to be significantly affected by the influence of the pump-induced flow behavior. By using oscillatory flow rates instead of pulsation-free pumps in non-reacting magnesium beds, backmixing is minimized and Bodenstein numbers were increased by 25 % for fine magnesium turnings and 70 % for coarse magnesium turnings. The pump-induced effect on the residence time distribution is also evident in the Grignard reagent selectivity. Side product formation, such as Wurtz coupling, diminishes the Grignard reagent selectivity and the product quality and therefore must be reduced. The Grignard reagent selectivity can be improved by increasing the available magnesium surface area, by choosing a packed bed tubular flow reactor instead of a semi-batch reactor and by thoughtfully selecting a suitable pump system to match the characteristics of the magnesium packing. Furthermore, by using a scale-up approach from semi-batch type syntheses to continuous lab and pilot scale syntheses, it is shown that a continuous production process has the potential to improve the selectivity of Grignard reagents in general, independent of the degree of affinity to Wurtz coupling. By using a modular reactor system at pilot scale for the synthesis of phenylmagnesium bromide, the reactor volume can be scaled to the required throughputs and necessary residence times, allowing flexibility of production without loss of selectivity. The results obtained contribute to the continuous synthesis of reactive intermediates, to the improvement of the Grignard reagent selectivity, to the targeted control of process conditions through the identification of the relevant process parameters and to the scalability of a solid/liquid reaction.

Description

Faculties

Fakultät für Naturwissenschaften

Institutions

Institut für Chemieingenieurwesen

Citation

DFG Project uulm

EU Project THU

Other projects THU

License

Lizenz B (ohne Print-on-Demand)
https://oparu.uni-ulm.de/xmlui/licenseB_opod_v1

Is version of

Has version

Supplement to

Supplemented by

Has erratum

Erratum to

Has Part

E. Deitmann, M. Maskos, G. Menges-Flanagan and D. Ziegenbalg; Impact of residence time distributions in reacting magnesium packed beds on Grignard reagent formation - pump-induced flow behaviour in non-reacting magnesium beds (part 1); React. Chem. Eng., 2023, 8, 2606-2619, https://doi.org/10.1039/D3RE00190C
 E. Deitmann, M. Maskos, G. Menges-Flanagan and D. Ziegenbalg; Impact of residence time distributions in reacting magnesium packed beds on Grignard reagent formation - selectivity of Grignard reagent formation (part 2); React. Chem. Eng., 2023, 8, 2717-2728, https://doi.org/10.1039/D3RE00191A
 E. Deitmann, K. Dahms, M. Maskos, D. Ziegenbalg and G. Menges-Flanagan; Selectivity of Grignard Reagent Formation: From Semibatch to Continuous Lab and Pilot Scale; Org. Process Res. Dev., 2023, 27, 12, 2345-2354, https://doi.org/10.1021/acs.oprd.3c00305
 E. Deitmann, G. Menges-Flanagan and D. Ziegenbalg; Infrared Spectroscopy as Process Analytics to Identify and Quantify Grignard Reagents; Organometallics, 2024, 43, 3, 219-226, https://doi.org/10.1021/acs.organomet.3c00441

Part of

DOI external

DOI external

Institutions

Periodical

Degree Program

DFG Project THU

item.page.thu.projectEU

item.page.thu.projectOther

Series

Keywords

Organometallic reagent, Residence time distribution, Process intensification, Selectivity, Packed bed, Magnesium, Infrarotspektroskopie, Reagierende Strömung, Grignard reagents, Infrared spectroscopy, Flow chemistry, DDC 540 / Chemistry & allied sciences