Ionic Liquid Immobilized Nickel(0) Nanoparticles as Stable and Highly Efficient Catalysts for Selective Hydrogenation in the Aqueous Phase

Nickel nanoparticles (NPs) well-dispersed in the aqueous phase were conveniently prepared by reducing nickel(II) salt with hydrazine in the presence of the functionalized ionic liquid 1-(3-aminopropyl)-2,3-dimethylimidazolium bromide. UV/Vis spectroscopy, elemental analysis, thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS) show the presence of a weak interaction of the functionalized ionic liquid with NiII and Ni0 complexes. The face-centered cubic structure of the Ni0 NPs was confirmed by X-ray diffraction (XRD) characterization. Transmission electron microscopy (TEM) images reveal that smaller Ni0 particles of approximately 6–7 nm average diameter assemble to give larger, blackberry-shaped particles with an average diameter of around 35 nm. The Ni NPs were employed as highly efficient catalysts for the selective hydrogenation of CC double bonds in the aqueous phase under mild reaction conditions (40–90 °C at 1.0–3.0 MPa), and the Ni0 nanocatalysts in the aqueous phase are stable enough to be reused at least seven times without significant loss of catalytic activity during subsequent reuse cycles.