Three Ni-MO/Al 0 NiO (2.8%) and MO&~; catalysts were prepared, containing similar amounts of components, ~13.5%), by simultaneous impregnation of the active varyind the nature of the solubilizing agent (ammonia, citric acid and phosphoric acid). The catalysts were characterized with respect to texture (surface area and pore volume), presence of crystalline phases (XRD), distribution of active components (EPMA) and nature of the active phases (DRS). Catalytic activity was measured using thiophene hydrogenolysis as a model reaction. A commercial Ni-Mo catalyst of similar composition was characterized by the same methods.
The catalyst prepared in the phosphoric acid medium (catalyst P) had a significantly lower surface area. In phosphorus-ccntaining catalysts there was a marked tendency of this element to be deposited on the external region of the catalyst extrudates. The DRS spectra showed that MO was present predominantly as polymolybdate species in all cases. In the industrial catalyst (catalyst I) the presence of nickel spine1 was clearly observed. Catalyst P had an absorption minimum in the visible region displaced to higher wavelength compared to the catalysts prepared in ammonia (catalyst A) and citric acid (catalyst C) media. The observed order of activity was P ) C > A > I.