γ-Al2O3@Ni/FeOx egg-shell microspherical catalysts for continuous flow selective hydrogenation of functionalized nitroarenes

The catalytic reduction of nitroaromatic compounds to aromatic anilines is a widely employed route for producing high-value refined chemicals and large-scale commodities. Developing highly efficient catalysts represents a promising strategy to achieve continuous and selective hydrogenation of functionalized nitroarenes under flow conditions. In this work, γ-Al 2 O 3 @Ni/FeO x egg-shell microspherical catalysts featuring high atomic dispersion, high specific surface area, and tunable active sites are designed by strategically harnessing hydrotalcite-inspired characteristics, which integrates a Ni–FeO x interfacial synergy into an egg-shell architecture for continuous-flow selective hydrogenation. In the continuous flow selective hydrogenation of o -chloronitrobenzene, the γ-Al 2 O 3 @Ni/FeO x -3 egg-shell microspherical catalyst presents a turnover frequency (TOF) of 30.16 h −1 , substantially higher than those of γ-Al 2 O 3 @Ni and γ-Al 2 O 3 @FeO x . Compared with the uniform Ni 3 Fe 1 /Al 2 O 3 catalyst, the egg-shell catalyst also exhibits enhanced mass transfer efficiency. The egg-shell catalyst enables an increased presence of electron-rich Ni δ- sites and FeO x species rich in oxygen vacancies on the surface of γ-Al 2 O 3 microspheres. Due to the formation of Ni δ- -O v -Fe 2+ , the egg-shell catalyst exhibits remarkable H-spillover capability, significantly enhancing the selective hydrogenation of o -chloronitrobenzene to o -chloroaniline. The apparent activation energy of the γ-Al 2 O 3 @Ni/FeO x -3 catalyst is only 22.99 kJ mol −1 , much lower than those of other egg-shell catalysts, indicating the synergistic integration of metallic Ni sites and oxygen vacancies. In addition, the as-prepared γ-Al 2 O 3 @Ni/FeO x -3 egg-shell catalyst presents long-term stability over 80 h and broad substate scope. This work offers comprehensive guidance for the rational design of industrial egg-shell catalysts, as well as establishes a solid foundation for the continuous flow selective hydrogenation process, aimed at producing substituted anilines from functionalized nitroarenes.