Nickel nanoparticles inserted in tBuONa matrix deposited on alumina - PartII - Thermal treatment and nickel content effects on their stabilty and catalytitic activity

Nanoparticles (1 nm-3 nm) of metallic nickel supported on alumina (4.3% Ni- 17.9% Ni w/w) were prepared from a colloidal precursor inserted in an organ ic matrix. Their structural and stability properties have been studied by X -Ray Diffraction (XRD), Electron Paramagnetic Resonance (EPR) and Thermal G ravimetric Analysis (TGA). Benzene hydrogenation at atmospheric pressure in the temperature range of 75 degreesC-200 degreesC was used as a test react ion of their catalytic capability. The thermal stability of the particles d epended on the nature of the reactive atmosphere. Thus, a growth in size (u p to around 20 nm) is observed under H-2 flow at 350 degreesC or during ben zene hydrogenation but not under air flow at 300 degreesC. The growth may b e due to the coalescence of the metal particles during the heating and deco mposition of the stabilizing organic matrix. Under oxidative atmosphere, st able nickel oxide particles, firmly attached to the support, are formed. Th e catalysts pre-treated under H-2/350 degreesC were active and stable in be nzene hydrogenation. The observed activities depended on the reaction condi tions and nickel composition. (C) 2001 Kluwer Academic Publishers.