PVA-encapsulated Palladium Nanoparticles: Eco-friendly and Highly Selective Catalyst for Hydrogenation of Nitrobenzene in Aqueous Medium

Graphical PVA-encapsulated Pd nanoparticles were synthesized in water medium and applied in the hydrogenation of nitrobenzene under mild conditions. They exhibit excellent catalytic perfor-mance for the eco-friendly production of aniline. In aqueous medium without any other additives, palladium (Pd) nanoparticles with water-soluble polyvinyl alcohol (PVA) as stabilizer were synthesized for the catalytic hydrogenation of nitrobenzene. Under the optimum experimental conditions, the nitrobenzene conversion and the selectivity for aniline were 99.3 % and 100 %, respectively. Comprehensive characterization methods, including TEM, UV/Vis, confocal laser scanning microscopy (CLSM), XRD and XPS allowed a better understanding of the role of PVA aggregates and the properties of Pd nanoparticles. The nitrobenzene conversion exceeded 80 % even after 6 cycles without any treatment of the catalyst. A mechanism about the hydrogenation of nitrobenzene catalyzed by Pd/PVA system was proposed. The Pd/PVA catalyst also exhibited excellent activity and selectivity, particularly to ortho -fluoronitrobenzene and ortho -nitrotoluene. This research can provide a reference for the environmentally friendly catalysis for hydrogenation of nitrobenzene and other substituted nitrobenzene compounds.