Implementierung von prozessanalytischen Methoden im Rahmen der Photochemie

Rößler, Martin; Liauw, Marcel A. (Thesis advisor); Wöll, Dominik (Thesis advisor)

Aachen : RWTH Aachen University (2023)
Dissertation / PhD Thesis

Dissertation, RWTH Aachen University, 2023

Abstract

Photochemistry sets a valuable tool in the portfolio of modern organic chemistry. Besides the extensive research on innovative reaction systems and photocatalysts, the investigation of the underlying reaction kinetics is essential for a further process intensification. In this context, process analytical technologies (Prozessanalysentechnik (PAT)) provide a great potential for the real-time monitoring of photochemical reactions and in consequence, for the acquisition of kinetic and mechanistic data. To support the continuous development within this field, this work describes a general method for the implementation of PAT and furthermore demonstrates its application to representative model systems. To conduct reproducible and efficient photochemical reactions, the innovative photoreactor platform PhotoFlexys was newly developed and qualified by means of representative modelsystems. Based on its modularity, the PhotoFlexys not only provides the implementation of various process conditions like the irradiation wavelength or irradiation intensity but also combines reactions under batch, multi-batch and continuous flow conditions within one device. The characterisation of the reactor platform is carried out based on temperature measurements, chemical actinometry as well as on methods to locally resolve the irradiation intensities. Based on four representative model systems, the superior performance of the developed reactor platform compared to further research-based and commercially available photoreactors is demonstrated by means of a significant reduction in reaction times. Based on the PhotoFlexys reactor platform, a general methodology for the implementation of PAT for photochemical reactions was developed. In this context, a new expansion module for the PhotoFlexys reactor platform allows the simultaneous irradiation and real-time monitoring by up to two in-situ analytical methods. In this context, three model systems using mIR-,Raman- and UV/Vis-spectroscopy were evaluated. This approach unlocks valuable kinetic and mechanistic insights like wavelength dependences, transport limitations or the degradation of the photocatalyst. Furthermore, the ease of the transferability of PAT from an in-situ analyser to an inline monitoring tool for continuous processing was demonstrated. Using the developed PhotoFlexys reactor platform and the PAT-based reaction monitoring, the controlled with riboflavin as a metal-free photocatalyst was investigated. The evaluation did not only confirm the potential of riboflavin as a metal-free photocatalysts but also discloses its degradation during the polymerisation. This observation led to the identification of lumichrome as the main degradation product and the so far unknown catalytic activity of alloxazines for the controlled photopolymerisation.

Institutions

• Department of Chemistry [150000]
• Technical Chemistry Teaching and Research Area [154220]