The sulphided state of nickel molybdenum catalysts supported on zirconia and aluminates

Characterization of the sulphided Ni-MoS(2) state supported on various carriers (aluminates, zirconia) has been undertaken in order to study the influence of the carrier on the genesis of the promoted active phase, refered to as the "NiMos" phase. The influence of the sulphidation temperature on the stability of nickel associated in that phase has also been explored. The basis of comparison is a classical Ni-MoS(2)-alumina catalyst. In all these systems nickel interacts with molybdenum sulphide (decoration like position) but the "NiMoS" phase appears less stable on zirconia. On these aluminate and zirconia carriers, the charge transfer from nickel to molybdenum sulphide, as evidenced by the shifts of the active IR band of adsorbed carbon monoxide, has been found to be weaker than on the alumina supported catalyst. Such a carrier effect has been correlated with thiophene HDS activity results and discussed in terms of morphological effects as revealed by HREM.