Colloidal nanometric particles of nickel deposited on gamma-alumina: characteristics and catalytic properties

The present paper deals with supported nanoparticles of metallic nickel pre pared by impregnation of an organometallic colloidal precursor (NiRC comple x) on gamma-alumina. The obtained supported materials (NiRCS complex) were characterized by STEM, EELS, XRD and TGA and tested in the hydrogenation re action of benzene and styrene both in the gas and liquid phases. EELS and S TEM studies showed that the metallic nickel nanoparticles of the NiRC precu rsor were well dispersed (1-3 nm) on the support, without size variation du ring the impregnation step. However, particle growth in NiRCS was observed in samples used after reaction tests. On the other hand, TGA experiments sh owed that the nickel phase was inserted in an organic matrix which remained in the supported material after impregnation. This organic matrix should b e partly removed or totally decomposed by washing with an appropriate solve nt or thermal treatment above about 250 degrees C under N-2, H-2 or air atm osphere respectively. The supported nickel particles were active in the gas phase hydrogenation of benzene in the temperature range of 150-200 degrees C and their activity was enhanced by partial removal of the organic matrix with an organic solvent (e.g. ethanol) or by its total thermal decompositi on. They were also found very active in the gas phase hydrogenation of styr ene at room temperature. Finally, the supported nickel particles exhibited good hydrogen reservoir properties in organic solvent media. (C) 1999 Kluwe r Academic Publishers.