Stacked Catalytic Membrane Microreactor for Nitrobenzene Hydrogenation

Abstract

In the present study, a novel stacked catalytic membrane microreactor assembled by microfluidic sheets and gaspermeable membranes was developed for gas−liquid−solid multiphase catalytic reactions. The developed microreactor consisted of multilayered perforated microchannels for supplying liquid reactants and perforated microchambers for supplying gas reactants, which were separated by poly(dimethylsiloxane) membranes with coated catalysts. Gas and liquid reactants flowed through their independent passageways layer by layer. Gas reactants bidirectionally permeated through the gas-permeable membrane to the catalyst layer, improving the gas utilization. Catalyst layers were prepared and immobilized on the membranes through layer-by-layer self-assembly and in situ reduction technology. Unlike other stacked microreactors, the integration of microchannels, microchambers, and membranes into one unit circumvented flow maldistribution, low durability, and low throughput of the microreactor. Furthermore, the scale-up of the membrane microreactor could be easily realized by increasing the number of microfluidic sheets and membranes. The catalytic performance was evaluated by nitrobenzene hydrogenation over palladium nanocatalyst. Results showed that the stacked catalytic membrane microreactor enabled a stable and efficient operation for 50 h. As the number of stacked layers was increased, the durability was continuously increased. The conversion was increased with increasing hydrogen flow rate or decreasing nitrobenzene flow rate. In addition, the increased inlet nitrobenzene concentration led to more serious catalyst deactivation, which decreased the conversion. In general, the stacked catalytic membrane microreactor developed in this study creates a new approach to design membrane microreactors for multiphase catalytic reactions.

Preparation of a Catalyst Layer by Layer-by-Layer Self-Assembly for Plate-Type Catalytic Membrane Microreactors

“…Compared to the results shown in Figure 5d, the Pd nanoparticles hardly changed after reaction, which might ensure the PDA/PEMs/Pd catalyst layer with higher catalytic activity and stability. This result is consistent with our previous work, 26 in which the double modification yielded the best performance. In general, the composite coating of the PDA/ PEMs on the PDMS membrane is a promising candidate for preparing the catalytic membrane, which can produce more aniline.…”

“…These results demonstrate the superiority of dual modification of the PDMS membrane by the PDA and PEMs, which has not been touched by the previous works. 15,25,26 Furthermore, how the flow rates and the initial nitrobenzene concentration affected the microreactor perform- ance was also investigated. With the nitrobenzene flow rate increased, the residence time decreased, which caused the nitrobenzene conversion to decline.…”

“…In the previous studies, , it has been demonstrated that the catalyst layers could be successfully prepared on the gas-permeable membranes of hollow fiber and nylon membrane by using the LbL self-assembly technology. Although this method has also been used to prepare a catalyst layer on the PDMS membrane for a stacked catalytic membrane microreactor, the main focus of this work was to demonstrate the superiority of the stacked design of the catalytic membrane microreactor. How the modification of the PDMS membrane by the LbL self-assembly technology affects the prepared catalyst layer and catalytic performance remains unclear.…”

Tuning Two‐Electron Oxygen‐Reduction Pathways for H2O2 Electrosynthesis via Engineering Atomically Dispersed Single Metal Site Catalysts

“…Also, flow designs are critical to continuously supplying reactants (i.e., O 2 ) to the active sites and removing products (i.e., H 2 O 2 ) from the electrodes. [ 217,218 ] For a flow‐by electrolyzer ( Figure a), the electrolyte continuously flows over the catalyst surface, which flushes away H 2 O 2 and regenerates the active sites, thus improving the efficiency. [ 219 ] Comparatively, in a flow‐through configuration, the electrolyte directly passes through the porous 3D electrodes (Figure 11b), 219 introducing convection to accelerate the diffusion process and enhance the active site utilization.…”

Porous Membrane Reactors for Liquid-Phase Heterogeneous Catalysis

“…The membrane configuration affects the membrane area per unit volume and is a key factor in determining the loading of the active components in the catalytic membrane. , The existing membrane configurations are mainly divided into flat-sheet membranes, , tubular membranes, , hollow-fiber membranes, , and nanofiber membranes. − Compared with flat-sheet and tubular membranes, hollow-fiber membranes of the same volume have higher surface areas, which can increase the loading of metal particles. Chen et al prepared Pd/hollow-fiber ceramic catalytic membranes using hollow-fiber ceramic membranes as the carrier.…”