Synthesis of Pd Nanocatalysts on the Multilayered Polyelectrolyte Film in a Gas-Liquid-Solid Microreactor for Nitrobenzene Hydrogenation

The layer-by-layer (LbL) self-assembly technique has been widely used for the formation of the polyelectrolyte multilayers (PEMs) film via surface charge inversion. The use of the electrostatic interactions then allows for the precursor to be efficiently adsorbed within or on the surface of the film followed by the reduction to nanocatalyts. Therefore, such a promising measure is particularly useful for the development of the microreactor. In line with this idea, we developed a gas-liquid-solid (G-L-S) microreactor with Pd nanocatalysts synthesized on the multilayered (PSS-PAH)_n film for nitrobenzene hydrogenation in present study. To do this, the microreactor substrate was firstly modified by a mussel-inspired polydopamine (PDA) coating, which was able to improve the stability of the multilayered (PSS-PAH)_n film. After that, PdCl₄^2- complex ions were adsorbed on the prepared multilayered (PSS-PAH)_n film and reduced to Pd nanocatalysts by NaBH₄. The developed microreactor was then accessed by the conversion of nitrobenzene hydrogenation to aniline. Particular attention of this work was paid to the effect of the number of the PSS-PAH. The role of the pH value in the LbL self-assembly process was also explored. The experimental results showed that not only the utilization efficiency of the precursor but also the durability of the developed microreactor could be improved by using this method.

Keywords: layer-by-layer self-assembly; PDA; PSS-PAH; Gas-liquid-solid microreactor; Nitrobenzene hydrogenation