MRI in chemical engineering

• MRT in der chemischen Verfahrenstechnik

Benders, Stefan; Blümich, Bernhard (Thesis advisor); Liauw, Marcel (Thesis advisor)

Aachen (2019)
Dissertation / PhD Thesis

Dissertation, RWTH Aachen University, 2019

Abstract

Magnetic Resonance based techniques such as Magnetic Resonance Imaging (MRI) offer many advantages to investigate systems in chemical engineering. In contrast to methods relying on e.g. optical properties, MRI provides an unique way to gain insights into systems utilizing a wealth of parameters to obtain additional information or contrast. This work demonstrates the potential of MRI in chemical engineering and the necessity to adapt the methodology to the application. Materials as well as dynamic systems are investigated employing techniques tailored to the application. On the material side, liquid distributions within the pore network of monolith reactors and Metal-Organic-Framework crystals are visualized. In both materials, the homogeneity of the liquid distribution within the pores is crucial to the efficiency in their corresponding application. The influence of different parameters such as loading and additives on the homogeneity is investigated with MRI. If spin density does not provide sufficient contrast, other parameters e.g. relaxation rates can be used. In this context, reaction sensitive relaxation agents are employed to visualize a reaction in the tail of a rising bubble. Furthermore, a fast chemical shift imaging sequence is implemented to reveal temperature gradients during sample heating. The sensitivity to motion enables NMR to investigate mass transport. The influence of microstructures on the mass transfer and liquid-wall interactions within a microfluidic reactor is investigated. Therefore, a 3D flow pulse sequence is developed, which enables the calculation of complex measures such as the shear rate. Furthermore, dynamics within operating electrochemical cells in magnetic fields are measured. The flow is caused by the Lorentz force and displays high dynamics. The influence of concentration, current and electrode material are evaluated.