Kavli Affiliate: Omar M. Yaghi
| First 5 Authors: Nanette N. Jarenwattananon, Stefan Gloeggler, Trenton Otto, Arek Melkonian, William Morris
| Summary:
Over 85% of all chemical industry products are made using catalysts, with the
overwhelming majority of these employing heterogeneous catalysts functioning at
the gas-solid interface. Consequently, optimizing catalytic reactor design
attracts much effort. Such optimization relies on heat transfer and fluid
dynamics modeling coupled to surface reaction kinetics. The complexity of these
systems demands many approximations, which can only be tested with experimental
observations of quantities such as temperature, pressure, concentrations, flow
rates, etc. One essential measurement is a map of the spatial variation in
temperature throughout the catalyst bed. We present here the first non-invasive
maps of gas temperatures in catalyst-filled reactors, including high spatial
resolution maps in microreactors enabled by parahydrogen. The thermal maps
reveal energy flux patterns whose length scale correlates with the catalyst
packing. By exploiting the motional averaging under a weak applied
magnetic-field gradient, the nuclear magnetic resonance (NMR) linewidths are
inversely proportional to temperature. Measurements during the hydrogenation of
propylene in reactors packed with metal nanoparticles and metal-organic
framework catalysts yield temperature coefficients of ~0.1 Hz/K, and
temperature error <4%. Temperature sensitivity increases with gradient
strength, enabling tuning of precision.
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