Sarah Mross

• Nuclear magnetic resonance (NMR) spectroscopy is a versatile analytical technique that enables noninvasive, quantitative measurements of chemical processes and transport phenomena without calibration. In chemical engineering, three practical barriers have so far restricted its wider use: prohibitively long measurement times, insufficient sensitivity of low-gyromagnetic-ratio nuclei such as 13C NMR, and the difficulty of performing quantitative analysis under continuous-flow. This dissertation addresses all three barriers by combining targeted applications and methodological developments, with a particular focus on paramagnetic relaxation enhancement (PRE) as a strategy for improving sensitivity and accelerating measurements. The first part investigates the chemical reactivity of hydrogen sulfide (H2S) in aqueous amine solutions relevant to industrial sour~gas treatment. Quantitative 1H and 13C NMR spectroscopy demonstrate that H2S leads to protonation of the amines without forming additional reaction products. These results provide experimental validation for assumptions commonly used in thermodynamic models for the design and simulation of sour gas reactive absorption processes. The second part addresses the determination of self-diffusion coefficients of synthetic fuels by pulsed-field-gradient (PFG) NMR spectroscopy over a broad temperature range. The resulting dataset serves as valuable input for the development of an entropy-scaling approach, thereby enhancing predictive capabilities for mass transport properties. The third part focuses on overcoming limitations of benchtop NMR spectroscopy under continuous-flow conditions. Although compact instruments are attractive for process monitoring, the low sensitivity of 13C nuclei and insufficient polarization build-up restrict their applicability at high flow rates for quantitative analysis. Introducing PRE via a synthesized immobilized PRE agent, enables quantitative 13C NMR measurements of mixtures at high flow rates by significantly reducing the spin-lattice relaxation time T1. Finally, a novel concept for accelerating NMR experiments is introduced. By spatially decoupling PRE from the detection region and shuttling the sample during the inter-scan delay, rapid polarization buildup is achieved under stagnant measurement conditions. This strategy reduces 13C NMR measurement times by one order of magnitude while maintaining spectral quality and quantitative accuracy. Together, these contributions advance NMR spectroscopy as a practical tool for chemical engineering, enabling faster measurements, more reliable quantitative analysis, and improved experimental data for the modeling and monitoring of industrial processes.