Unsupported Ni‐mo Sulfide Catalysts: Relation Between the HDS and Hydrogenation Activities and Some Structural Properties

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Abstract
A series of unsupported sulfide catalysts containing nickel and molybdenum (with variable atomic ratio a Ni/Ni + Mo) was prepared using a variant of the H.S.P. method which promotes an “intimate contact” between the metallic ions. These catalysts show good activities in the dibenzothiophene hydrodesulfurization (under atmospheric or high pressure) and in the biphenyl hydrogenation. For the two reactions, the maximum of synergy is observed for a about 0.7.X‐ray diffraction shows that for a < 0.3, only the MoS2 type phase is detected (before and after catalytic test). For higher values of a, nickel sulfide initially present under the NiS2 and NiSβ phases form, is converted into the Ni3S2 phase by catalytic working.The variations, in terms of a, of the specific area, of the stoichiometric ratio S/Ni + Mo' of the c parameter of the MoS2 type phase, of the TPR spectra shape, show the existence of a mixed phase “Mo ‐ Ni ‐ S” of the same crystallo‐graphic type than MoS2. The presence of this phase would induce an increase of the HDS and hydrogenation properties of the catalyst without explaining the position of the synergy maximum.