Catalytic membrane microreactor with Pd/γ-Al2O3 coated PDMS film modified by dopamine for hydrogenation of nitrobenzene

• A catalytic membrane microreactor was developed for hydrogenation of nitrobenzene.
• Catalytic membrane was formed by coating catalysts on PDMS film modified with polydopamine.
• The developed microreactor yielded better performance and stability.
• Parametric study was also performed to optimize the microreactor design and operation.

Conventional gas–liquid–solid reactors usually face the gaseous reactant transport issues in association with the interface and liquid phase to immobilized solid catalysts. To resolve this problem, a catalytic membrane microreactor (CMMR) with the catalytic membrane formed by coating the catalysts on a thin PDMS film modified by dopamine was developed in this study, which not only eliminated the issues in the conventional gas–liquid–solid reactors but also provided a large surface-area-to-volume ratio to enhance the mass transport. The performance of the developed CMMR was evaluated by hydrogenation of nitrobenzene. It was found that the nitrobenzene conversion and operation stability was greatly improved by the CMMR as a result of enhanced mass transport of hydrogen. Parametric study was also performed in this work to explore how the operation conditions and reactor design affected the performance. It was shown that low liquid flow rate and high gas flow rate benefited for the improvement in the nitrobenzene conversion due to the increased residence time and hydrogen permeation rate through the membrane. The results on the effect of the inlet nitrobenzene concentration showed that an increase in the inlet nitrobenzene concentration increased the aniline concentration because of enhanced catalytic reaction rate but lowered the nitrobenzene conversion because of the overloaded liquid reactant. Besides, it was also shown that thinner membrane could enhance the hydrogen permeation through the membrane, thereby yielding higher nitrobenzene conversion. This study fully demonstrates the feasibility and superiority of the developed CMMR for the gas–liquid–solid reaction system.