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Spatially Resolved Characterization of the Gas Propagator in Monolithic Structured Catalysts Using NMR Diffusiometry |
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| Authors: | Mojtaba Mirdrikvand Jan Ilsemann Jorg Thöming Wolfgang Dreher |
| Affiliation: | 1. University of Bremen, Department of Chemistry, In vivo MR Group, Bremen, Germany;2. University of Bremen, Institute of Applied and Physical Chemistry, Department of Chemistry, Bremen, Germany;3. University of Bremen, Center of Environmental Research and Sustainable Technology (UFT), Bremen, Germany |
| Abstract: | Gas diffusivity measurements in opaque porous media were performed using nuclear magnetic resonance. An optimized pulsed‐field gradient stimulated echo method with free volume selection was used to investigate the propagator of thermally polarized methane gas within commercial monolithic catalyst supports. Since signal losses due to T2 relaxation were minimized by using a short echo time, diffusion processes could be characterized by the measured propagator functions and effective diffusion coefficients were determined for a broad range of observation times and in different spatial directions. The study of this noninvasive characterization of gas diffusion found a clear effect of the monolith type and its pore size and coating on the effective gas diffusion coefficient and the apparent tortuosity for a given observation time. |
| Keywords: | Diffusion Heterogeneous catalysis Propagator Thermally polarized gas Tortuosity |