Catalytic properties of nickel molybdenum sulphide supported on zirconia

Zirconia has been investigated as a support material for Mo and NiMo sulphide catalysts. Thiophene HDS studies (1 atm, 400°C) reveal that the ZrO₂-supported Mo catalysts are twice as active as the corresponding Mo/Al₂O₃ catalysts. The promoting effect brought by nickel, however, is much smaller than expected in comparison with alumina supported catalysts; the use of zirconia induces higher hydrogenation selectivity. It is suggested that the promoter ions interact with both the Mo sulphide slab and the zirconia carrier, which results in a change in properties of the mixed catalytic sites.

The increased selectivity towards hydrogenation may be an important advantage when dealing with hydrodenitrogenation processes. Indeed, in catalytic tests carried out at 70 atm, 350°C, 2,6-diethylaniline reacts more rapidly over zirconia catalysts ; similarly, the hydrogenation route is well developed in the complex reaction scheme of quinoline. However the inhibiting effect of quinoline (or 1,2,3,4-tetrahydroquinoline) upon the reactivity of alkylanilines is as strong on zirconia supported as on alumina supported catalysts.

Nevertheless, the beneficial effect of the zirconia carrier is observed in the HDN of the less reactive phenanthridine molecule (140 atm, 340°C), and also in the HDN of real feed in a pilot test.