Water accelerated activity of Ru NPs in sequential hydrogenation of nitrobenzene to cyclohexylamine

It is difficult to balance the two separate and connected reaction steps in the sequential hydrogenation of nitrobenzene (NB) to cyclohexylamine (CHA) via only tuning the active sites. In this work, we optimize the activity of supported Ru NPs in the one-pot NB hydrogenation to CHA by tuning the surface hydrophobicity of the catalysts and by investigating the solvation effect. The Ru supported on hydrophobic mesoporous silicas is more active than that on hydrophilic mesoporous silicas, which may be attributed to the enrichment effect of the former one for hydrophobic NB. Furthermore, the activity of Ru is significantly promoted with the addition of H 2 O in the reaction system. Systematic studies suggest that the water promotion effect is mainly related with the decreased adsorption strength of NB on Ru surface and the water accelerated H* transfer during the NB hydrogenation process. Our primary results suggest that the modification of the surface properties of the catalysts and the deeper understanding of the solvation effect play an important role in one-pot cascade reactions.