SYNTHESIS AND CHARACTERIZATION OF NICKEL SULFIDE CATALYSTS

Nickel sulfide catalysts obtained. by homogeneous precipitation were p repared by varying the homogenization time and the sulfiding temperatu re. Structural characterization studies by transmission electron micro scopy and x-ray diffraction showed the formation of various metastable crystalline phases at low temperatures of sulfiding (Ni3S2, Ni3S4, Ni 7S6, Ni9S8, NiS2, NiS1.03, NiS), depending on the preparation conditio ns. NiS millerite appears to be the main phase for samples obtained af ter 4 h homogenization, changing to NiS1.03 phase after 36 h. Catalyti c tests of these samples for cyclohexanone hydrogenation showed that t he intrinsic activity is higher for the NiS1.03 phase. (C) 1998 Americ an Vacuum Society. [S0734-2101(98)01306-2].