When the smallest are the most efficient: Colloidal methods for the development of a Ni-based catalyst, selective in m-dinitrobenzene hydrogenation

Monodispersed Ni NPs (from 2 to 14 nm, as confirmed by high resolution transmission electron microscopy) were prepared via colloidal methods using poly-N-vinyl-2-pyrrolidone (PVP) as stabilizer and tested as catalysts in the m-dinitrobenzene multi-phase hydrogenation. Antipathetic structure sensitivity, i.e. a 6-fold higher turnover frequency over larger Ni NPs, has been established. The selectivity to the target m-nitroaniline (m-NAN) was size independent over Ni NPs as per, probably, due to the traces of PVP remaining on the Ni surface. Supporting the monodispersed (2 nm) Ni NPs on activated carbon fibers (ACF) and removing traces of PVP rendered a highly selective Ni2/ACF catalyst allowing up to 95% yield of m-NAN. Two-sites Langmuir-Hinshelwood kinetic model was applied to rationalize the results obtained and found to be consistent with the experimental kinetic data.