Kinetic investigation on the chemoselective hydrogenation of α,β-unsaturated carbonyl compounds catalyzed by Ni(0) nanoparticles
A series of Ni(0) nanocatalysts was prepared from 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 reducing only the C=C 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 on the t-chalcone chemoselective reduction of the C=C 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 mechanism type. Regarding sustainable chemistry concerns, the best catalyst could be reused up to 10 times without significant loss of activity.