Synthesis and Characterization of Nickel, Cobalt and Iron Raney Catalysts Prepared by Mechanical Alloying and Alkaline Leaching

摘要

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 Al_(50)Ni_(50), Al_(656)Ni_(35), Al_(50)Co_(50), Al_(60)Co_(40), Al_(40)Fe_(60) and Al_(50)Fe_(50) (at. pct.) elemental mixtures. X-ray diffraction revealed that Al_3Ni_2, AlNi, AlCo and AlFe intermetallic phases were produced by MA. After leaching, the phases present in the materials changed mainly from Al_3Ni_2 to Ni and NiO; from AlCo to fcc Co and CoO; from AlFe to Fe_2O_3 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 m~2/g. In the case of the nickel catalyst derived from the Al_3Ni_2 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.