Kinetic investigation into the chemoselective hydrogenation of α,β-unsaturated carbonyl compounds catalyzed by Ni(0) nanoparticles

A series of Ni(0) nanocatalysts was prepared from a Ni(COD)2 complex in the presence of different stabilizers (hexadecylamine, polyvinylpyrrolidone (PVP), PVP/triphenylphosphine, octanoic acid and stearic acid) for their evaluation in the selective hydrogenation reaction of α,β-unsaturated carbonyl compounds by H2 under mild reaction conditions, i.e., low H2 pressure, temperature and catalyst loading. All nanocatalysts were active in reducing only the CC bond and this chemoselectivity was attributed to the reduced nature of the Ni-NPs surface. Moreover, the hydrogenation reaction rate appeared to be sensitive to ligand type, with the carboxylic acid-stabilized systems showing the best performances. A full kinetic investigation into the t-chalcone chemoselective reduction of the CC bond, with the best catalyst (Ni-octanoic acid) revealed that the rate-determining step is the hydrogenation of the adsorbed substrate on the NPs surface, following a Horiuti–Polanyi type of mechanism. Regarding sustainable chemistry concerns, the best catalyst could be reused up to 10 times without significant loss of activity.