The influence of an exothermic reaction on the spatial distribution of the liquid phase in a trickle bed reactor: Direct evidence provided by NMR imaging

Characterization and modelling of a maldistributed Trickle Bed Reactor

“…In return the transfer efficiency (heat and mass) is rather low, and hydrodynamics are very sensitive to the quality of distribution at the top of the catalyst bed. Poor fluid distribution, called maldistribution, is suspected in industrial reactors when transversal deviations of temperature or hot spots are measured on thermowells embedded in the catalytic bed . However, dissociating fluid maldistribution from defaults of catalyst loading is almost impossible to figure out, and resulting flow heterogeneities are not well understood yet.…”

“…One first and straightforward way to study quality of distribution and hydrodynamics inside Trickle Bed Reactors (TBRs) consists of using representative mockups to characterize the flow inside a bed of solid particles. To do that, many experimental methods are usable and are reported in the literature including flux collectors, wire mesh tomography, nuclear magnetic resonance, electrical tomography, X‐ray, and γ‐ray computed tomography . Experimental methods are very useful to characterize the flow inside fixed bed reactors and to compare the quality of fluid distributions, but those still have inherent defaults.…”

Experimental Evaluation of Distributor Technologies for Trickle-Bed Reactors

“…When coupled with highly exothermal reactions, gas and liquid maldistribution may be amplified by the fast drying of the catalyst and may possibly lead to local hot spots. 2,3 Poor flow distribution generated by distributor technologies can be partially corrected by optimized layers of grading materials, with specific packing particles being able to enhance phase radial distribution. 4−6 Unfortunately, this corrective approach is often not sufficient, with the catalyst bed having in any case few transverse mixing properties.…”

“…Otherwise, channeling may appear, causing a significant loss in catalyst activity and an earlier catalyst deactivation. When coupled with highly exothermal reactions, gas and liquid maldistribution may be amplified by the fast drying of the catalyst and may possibly lead to local hot spots. , …”

In Situ Monitoring of Heterogeneous Catalytic Hydrogenation via 129Xe NMR Spectroscopy and Proton MRI

“…Magnetic resonance methods, that is, nuclear magnetic resonance spectroscopy (NMR) and magnetic resonance imaging (MRI), are powerful instruments to do so. Because of their noninvasive nature, NMR and MRI can be used for operando studies of catalytic reactions; , for instance, these techniques can be successfully used for obtaining spatially resolved conversion information − and velocity distributions − for catalytic reactors, for monitoring the process of catalyst preparation, − and even for temperature measurements. NMR thermometry of working catalytic reactors is based on the temperature dependence of the properties that can be measured by NMR, such as the chemical shift, , the NMR signal width, or the NMR signal intensity. , It either utilizes external substances with temperature-sensitive NMR properties (such as ethylene glycol in a capsule , ), or relies on the properties of the NMR signals of the catalysts (e.g., 27 Al NMR spectroscopy of alumina , ) or the reactants themselves.…”