NMR Relaxometry and Diffusometry Studies for Investigating Heterogeneous Catalysis
The work described in this thesis mainly concerns the development and implementation of nuclear magnetic resonance (NMR) methods to provide quantitative information on chemical conversion within a novel NMR compatible trickle-bed reactor (TBR). Techniques to map the distribution of chemical species within a catalyst bed were implemented under non-steady state and steady state conditions.
Batch reactions were carried out to benchmark a simple aromatic hydrogenation reaction (styrene) and more complex reactions, such as aromatic nitrile hydrogenations (benzonitrile and phthalonitrile) over a Pd/Al2O3 catalyst. These were subsequently tested in the continuous flow TBR under near-ambient conditions. Batch reactions revealed information on the inter- particle chemical kinetics, conversion, and selectivity for the desired reactions.
Non-spatially resolved and spatially resolved 2D NMR relaxation and diffusion correlations along with spectroscopic techniques were used to extract intra-particle chemical kinetics both under non-steady state and steady state conditions. These were compared with chemical compositions retrieved from the outlet of the TBR.
The Modified Total Generalised Variation (MTGV) regularisation technique was developed to improve the resolution of 2D NMR correlations and verified against a more established technique. Compressed sensing was also implemented to increase temporal resolution of 2D spectroscopic methods.
This work improves the understanding of catalytic reactors and contributes to the advancement of magnetic resonance to investigate complex, multi-component reactions relevant to the agricultural and chemical industry.
Engineering and Physical Sciences Research Council (2073044)