Investigation of external mass transfer in micropacked bed reactors

Preparation of Pd/Al2O3/Nickel Microfoam Catalysts by Electrodeposition for Hydrogenation in a Micropacked Bed Reactor

“…The reaction temperature, pressure, AMS initial concentration, and gas flow rate were set as 30 °C, 0.6 MPa, 10 wt %, and 20 mL·min –1 , respectively. This hydrogenation is an extremely fast reaction, which enables a fully mass transfer limited regime to be reached even at moderate temperature and pressure. , Assuming a plug flow model, the apparent rate of reaction ( r a ) can be determined by the integration of a steady state mass balance over the whole catalyst. , The apparent rate can be expressed in terms of the AMS conversion and the liquid flow rate, as shown in eq . , where χ AMS and m Pd refer to the AMS conversion and the mass of the active component Pd, respectively. The overall gas–liquid–solid external mass transfer coefficient ( k ov ) can be measured through the hydrogen balance between the gas phase and the catalyst layer, which is given in eq . where , , V L , η, and r ( ) refer to the hydrogen concentration at equilibrium, the hydrogen concentration at the catalyst surface, the liquid volume, the effectiveness factor, and the intrinsic reaction rate, respectively.…”

Reactor Selection for Upgrading Hemicelluloses: Conventional and Miniaturised Reactors for Hydrogenations

“…Micro packed-bed reactors with particles of a few micrometres provide very fast mass transfer and nearly plug flow behaviour that make them an excellent tool to access intrinsic kinetic data [120,[128][129][130][131][132][133], although radial mass transfer may negatively affect the obtained data as has been recently discussed by Moulijn et al [134]. For the near future, Ranade et al [122] as well as Hommes et al [135] attested micro packed bed reactors also several application areas, especially in the production of specialties and pharmaceuticals due to the above-discussed features, which excellently meet the needs of hydrogenations, oxidations, or fluorinations.…”

Investigation of Effective Interfacial Area in Micropacked Bed Reactors

“…For gas–liquid–solid reactions with fast intrinsic kinetics, the overall reaction rates are generally limited by the external mass transfer rate when the internal mass transfer limitation is eliminated. , The external mass transfer relates to reactant transport across the phase boundaries of gas–liquid and liquid–solid for multiphase reaction systems . The gas–liquid mass transfer is the first step for the external mass transfer process, and it has a significant influence on the global external mass transfer rate. , For the gas–liquid process, an automated platform for mass transfer measurement has been developed , and the obtained gas–liquid volumetric mass transfer coefficients ( k L a ) were in the range of 0.12–0.39 s –1 for glass beads (125–425 μm) and 0.047–0.38 s –1 for foam packing (81–309 μm) in μPBRs. The values of k L a are about 1–2 orders of magnitude larger than those of conventional TBRs (0.0004–0.015 s –1 ). , Previously, we measured the external mass transfer rates by the hydrogenation of α-methylstyrene over the Pd/glass bead catalyst in μPBRs and analyzed the contribution of gas–liquid mass transfer on the external overall mass transfer.…”

“…The gas–liquid mass transfer is the first step for the external mass transfer process, and it has a significant influence on the global external mass transfer rate. , For the gas–liquid process, an automated platform for mass transfer measurement has been developed , and the obtained gas–liquid volumetric mass transfer coefficients ( k L a ) were in the range of 0.12–0.39 s –1 for glass beads (125–425 μm) and 0.047–0.38 s –1 for foam packing (81–309 μm) in μPBRs. The values of k L a are about 1–2 orders of magnitude larger than those of conventional TBRs (0.0004–0.015 s –1 ). , Previously, we measured the external mass transfer rates by the hydrogenation of α-methylstyrene over the Pd/glass bead catalyst in μPBRs and analyzed the contribution of gas–liquid mass transfer on the external overall mass transfer. The values of the external overall volumetric mass transfer coefficient (( ka ) OV ) of the μPBRs ranged from 0.15 to 2.76 s –1 while k L a ranged from 0.16 to 0.34 s –1 , indicating that the gas–liquid mass transfer coefficient remarkably influences the external mass transfer process.…”