Investigation of External Mass Transfer in a Micropacked Bed Reactor with a Pd/Al₂O₃/Nickel Foam

Abstract

External mass transfer performance of micropacked bed reactors (μPBRs) with Pd/Al 2 O 3 /nickel foam catalysts is investigated by the hydrogenation of α-methylstyrene (AMS). The external mass transfer limitation region for AMS hydrogenation can be determined by means of the apparent activation energy and internal effectiveness factor. Parametric studies for external mass transfer are conducted by varying temperatures, operating pressures, liquid viscosities, gas and liquid superficial velocities, and pore diameters of foam packing. The external volumetric mass transfer coefficients [(ka) OV ] of μPBRs with the Pd/Al 2 O 3 /nickel foam range from 0.06 to 0.71 s −1 . An empirical correlation of (ka) OV is developed. Based on the gas−liquid−solid process analysis, the external mass transfer of μPBRs with the Pd/Al 2 O 3 /nickel foam is limited by liquid−solid mass transfer under the experimental conditions. Moreover, μPBRs with the Pd/Al 2 O 3 /nickel foam exhibit the best energy efficiency in comparison with that of other multiphase reactors.

External Mass Transfer Performance Studies in a Micropacked Bed Reactor with Pd/PDA/Nickel Foam

“…As shown in Figure a, ( ka ) OV decreased as the system pressure increased. Similar phenomena have been observed in microstructure falling film reactors, milli-channel packed bed reactors with large particles, laser-sintered structured reactors, and μPBRs with Pd/Al 2 O 3 /foam packing . Lower gas superficial velocities at higher pressures may lead to a decrease of the gas–liquid interaction and interfacial area ( a ), which reduces the external mass transfer coefficient.…”

“…Detailed preparation processes of the Pd/Al 2 O 3 /nickel foam catalyst can be found in our previous work. 24 For PDA coating, the method of impregnation was applied. 2 g•L −1 dopamine solution was prepared by dissolving 0.2 g of dopamine hydrochloride in 0.01 mol/L aqueous Tris buffer solution (10 mmol•L −1 , pH = 8.5).…”

“…Similar phenomena have been observed in microstructure falling film reactors, 31 milli-channel packed bed reactors with large particles, 6 lasersintered structured reactors, 37 and μPBRs with Pd/Al 2 O 3 / foam packing. 24 Lower gas superficial velocities at higher pressures may lead to a decrease of the gas−liquid interaction and interfacial area (a), which reduces the external mass transfer coefficient. A similar phenomenon was also observed in the study of the external mass transfer performance of a laser-sintered structured reactor by Vernuccio et al 37 Figure 7b demonstrates the variation of (ka) OV with gas and liquid superficial velocities.…”

“…ED for nickel foam catalyst in μPBRs had a higher mass transfer performance for the nitrobenzene hydrogenation reaction compared to the CS method. Based on our previous work, it was found that the ( ka ) OV and energy efficiency (the ratio of mass transfer to energy dissipation) of μPBRs with Pd/Al 2 O 3 /nickel foam prepared by ED ranged from 0.06 to 0.71 s –1 and from 3.6 to 165 m 3 /(kW·s) at low fluid superficial velocity, respectively. Energy efficiency is 1 to 3 orders of magnitude larger than that of conventional TBRs.…”

Efficient and continuous furfural hydrogenation to furfuryl alcohol in a micropacked bed reactor

“…In gas-liquid-solid catalytic hydrogenation reactions, the external diffusion process entails two steps: hydrogen dissolved in furfural solution and furfural solution with hydrogen transferred to solid catalyst surface processes. 28,51 To investigate the intrinsic kinetics, the effect of external diffusion resistances should be ignored. The effect of external diffusion can be eliminated when the average reaction rate is not varied with the increase of liquid superficial velocities at the same liquid residence times.…”