Synergy of Rh Nanoparticles With Fe3O4 for Efficient Selective Catalytic Transfer Hydrogenation of Nitrostyrenes Using Stoichiometric Hydrazine Hydrate

Abstract

ABSTRACTHydrazine hydrate as a hydrogen source has a good effect on nitro reduction, but overuse has environmental toxicity and is prone to over‐hydrogenation, resulting in low selectivity. Herein, we report a magnetically separable Rh/Fe3O4 (1.26 wt%) catalyst containing an optimal Rh content that can completely convert 3‐nitrostyrene to 3‐vinylaniline (> 99% selectivity) using a stoichiometric molar ratio of hydrazine hydrate (‐NO2:N2H4·H2O = 1:1.5). This is due to the synergy between Rh and Fe3O4 and the natural selectivity of N2H4·H2O for nitro. The synergy can reduce the activation energy of the reaction (36.6 kJ/mol), increasing the reduction rate of nitro group and avoiding the combination of active hydrogen species (H*) to H2 as well as the hydrogenation of N2H4 to NH3. Moreover, the active H* produced by N2H4·H2O is different from that produced by H2, and excess dose of N2H4 will inevitably yield H2 thus decline the selectivity.