Synthesis and characterization of nickel, cobalt and iron raney catalysts prepared by mechanical alloying and alkaline leaching

Raney Ni, Co and Fe catalysts have been produced by mechanical alloying (MA) of elemental powder mixtures followed by leaching in aqueous alkaline solutions, with the resulting product being a fine and highly porous solid. The precursor alloys were prepared from Al₅₀Ni₅₀, Al₆₅Ni₃₅, Al₅₀Co₅₀, Al₆₀Co₄₀, Al₄₀Fe₆₀ and Al₅₀Fe₅₀ (at. pct.) elemental mixtures. X-ray diffraction revealed that Al₃Ni₂, AlNi, AlCo and AlFe intermetallic phases were produced by MA. After leaching, the phases present in the materials changed mainly from Al₃Ni₂ to Ni and NiO; from AlCo to fcc Co and CoO; from AlFe to Fe₂O₃ and bcc Fe. Only the AlNi phase was not leached to any significant degree. The catalysts produced in this way had specific surface areas in the range 70 to 140 m²/g. In the case of the nickel catalyst derived from the Al₃Ni₂ intermetallic produced by MA, electron spin resonance measurements indicated a peculiar behavior which may be explained by a large fraction of Ni atoms occupying grain boundary sites.