Chemoselective Hydrogenation of 4-Nitrostyrene to 4-Aminostyrene by Highly Efficient TiO2 Supported Ni3Sn2 Alloy Catalyst

Ni3Sn2 alloy catalysts supported on various metal oxides (TiO2, Al2O3, ZrO2, SnO2, and CeO2) were successfully prepared by simple hydrothermal method and then applied to the hydrogenation of 4-nitrostyrene under H2 3.0 MPa at 423 K. All the supported catalysts hydrogenated the nitro group more preferentially than the olefin group from the initial reaction stages, showing 100% chemoselectivities towards the desired 4-aminostyrene. This may be attributed to σ-interaction between the oxygen lone pairs in the nitro group and Sn atoms in Ni3Sn2 alloy. By prolonging the reaction times, the 4-aminostyrene yields increased and finally reached the maximum yields. Among the catalysts, Ni3Sn2/TiO2 alloy catalyst showed the highest catalytic activity with remarkably high chemoselectivity towards 4-aminostyrene. The conversion and chemoselectivity were 100% and 79%, respectively, at a reaction time of only 2.5 h. From the physical and chemical characterization of the supported catalysts, it was clear that the catalytic activity was correlated with H2 uptake. The application of the best catalyst for the hydrogenation of a wide variety of substituted nitroarenes resulted in the chemoselective formation of the corresponding aminoarenes.