Ionic liquid immobilized nickel(0) nanoparticles as stable and highly efficient catalysts for selective hydrogenation in the aqueous phase

Abstract

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 spectros-copy, elemental analysis, thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS) show the presence of a weak interaction of the functionalized ionic liquid with Ni11 and Ni 0 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 C=C 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. © 2010 Wiley-VCH Verlag GmbH © Co. KGaA, Weinheim.