The effect of nickel and phosphorus on activity of alumina-supported molybdenum catalysts in simultaneous hydrodesulfurization (HDS) of thiophene and hydrodenitrogenation (HDN) of pyridine was studied. The introduction of nickel into molybdenum-containing catalysts promotes strongly HDS of the alumina-supported nickel-molybdenum catalyst while the increase in HDN activity is less pronounced. The synergistic effect in pyridine HDN is explained as the consequence of synergism in HDS. The weak promoting effect of phosphorus was observed for NiMo/Al2O3 catalyst containing 1 wt% of phosphorus. Above this concentration, both HDS and HDN activities decrease again. HDS activity of P-modified NiMo/Al2O3 samples was similar to that of the commercial NiMo/Al2O3 Shell catalyst. However, the HDN selectivity in pyridine reaction was higher for commercial catalyst which is explained by exceptionally higher dispersion of nickel on this catalyst.
