Synergistic effect of Ru-Ni nanoparticles supported on mesoporous carbon black for highly selective hydrogenation of nitrobenzene to aniline in aqueous phase

Nitroaromatic hydrocarbons are commonly converted into aromatic amines using high-pressure hydrogen (H₂) in organic solvents over heterogeneous catalysts. However, this method often poses cost challenges and potential risks. Consequently, the careful selection of the reaction medium, hydrogen sources, and efficient catalysts is essential for optimizing production. In this study, a novel mesoporous carbon black-supported nanoscale nickel catalyst, promoted by ruthenium (labeled as Ru-Ni/CB), was developed to reduce nitrobenzene to aniline in an aqueous medium. The results show that the immiscibility of nitrobenzene with water leads to low efficiency when using a 10 wt% Ni/CB catalyst. However, the introduction of a small quantity of Ru, along with specific alcohols, enhances the catalytic reaction by creating a well-miscible ternary phase. A 10 wt% Ru₁-Ni₉/CB catalyst exhibits exceptional catalytic performance for the hydrogenation of nitrobenzene using both external and endogenous hydrogen. The optimal catalytic coupling effect is achieved through the dehydrogenation of isopropanol and the in-situ hydrogenation of nitrobenzene at 240 °C for 2 h, resulting in a 99.0 % conversion of nitrobenzene and a 99.6 % selectivity for aniline. The apparent activation energies for the two tandem reactions are 39.9 and 82.4 kJ/mol, respectively. Furthermore, this catalyst demonstrates superior catalytic performance when compared to many reference catalysts. This study highlights a significant synergistic effect of the Ru-Ni/CB catalyst in nitrobenzene hydrogenation, showcasing high activity, selectivity, and stability.