Tuning the selectivity of nitrobenzene hydrogenation over Pd/CeO2 catalysts for azoxybenzene synthesis under solvent-free conditions

Precise control of selectivity in nitrobenzene hydrogenation is a long-standing challenge, especially under solvent-free conditions. The PdOx is the key species for enhancing H2 dissociation and nitrobenzene conversion. Here, we report that tuning the proportion of PdOx deposited on CeO2 with regulating methods of different preparation methods, CeO2 shape-selectivity and modifying Pd particle sizes could effectively tailor the selectivity of nitrobenzene hydrogenation. With calcination temperature of 450 degrees C, the Pd/CeO2-4.72 nm catalyst exhibited a satisfying azoxybenzene yield of 70.4% under solvent-free conditions. This work opens a new window for the stable and effective synthesis of intermediates in organic reactions.