STRUCTURAL CHARACTERISTICS AND CATALYTIC PERFORMANCE OF NICKEL-CATALYSTS FOR SELECTIVE HYDROGENATION OF 1,6-HEXANEDINITRILE

Several nickel catalysts have been characterized on the basis of their Brunauer-Emmett-Teller (BET) surface areas, X-ray diffraction, X-ray photoelectron spectra, field-emission scanning electron microscopy and temperature-programmed reduction properties. The catalysts were used for the heterogeneous hydrogenation of 1,6-hexanedinitrile at 443 K and atmospheric pressure, with no ammonia in the feed. Highly reduced nickel with a low BET area is obtained above 498 K. XPS and field-emission scanning electron micrographs of reduced catalysts revealed the appearance of incipiently reduced nickel on top of NiO crystals at 463-473 K. This structure is responsible for the high hydrogenation activity: however, only 100% selectivities toward 6-aminohexanenitrile were obtained by reduction at temperatures as high as 623-673 K. It seems that a specific arrangement of nickel atoms is required to obtain selective catalysts.