Stacked Catalytic Membrane Microreactor for Nitrobenzene Hydrogenation

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.