Hydrogenation of Substituted Nitroaromatics on Non-Noble Metal Catalysts: Mechanistic Insights to Improve Selectivity
he mechanism of nitrobenzene hydrogenation on non-noble metals such as Ni is different from that previously reported on noble metals like Pt. The newly proposed pathway involves the initial dissociation of the two N-O bonds of nitrobenzene (Ph-NO2 → Ph-NO → Ph-N), leading to a partial oxidation of the catalyst surface, followed by two successive hydrogenation steps (Ph-N → Ph-NH → Ph-NH2) that finally produce the functionalized aniline. Due to the oxophylic nature of non-noble metals like Ni, Co or Cu, the hydrogenation of the Ph-N intermediate and the removal of O in the form of water become the most energy demanding steps of the process. The strength of the interaction of O, H and N with different metals, and the preferential mode of adsorption of nitroarenes on clean and partially oxidized systems obtained from DFT calculations, is used now to propose an efficient non-noble metal catalyst that optimizes activity and selectivity.
- This article is part of the themed collection: Reaction mechanisms in catalysis