Kinetic Study of the Effect of Phosphorus in the HDN of 5‐Tetrahydroquinoline Over Ni‐MoS/γ‐Al₂O₃ Catalysts

THE ROLE OF PHOSPHORUS ON THE STRUCTURE AND PERFORMANCE FOR HYDRODESULFURIZATION AND HYDROGENITROGENATION REACTIONS OF P‐CONTAINING Ni/AL2o3 CATALYSTS

“…Several explanations have been proposed to account for the improvement in activity in P, such as improved dispersion of the Mo and Ni(Co) activephases (2, 5, 7, 8, 10, 11, 19), a change in Mo dispersion and the coordinatively unsaturated Mo sites (6), influence of phosphates on the hydrogenolysis step (13), increased stacking of MoS2 and change of morphology (9,20,21), a modificatlon in the properties of the Mo and Co edge sites (22), changes in acidity (8, 23), formation of new sites associated with phosphate (13, 14,23) and partial formation of atype II NiMoS phase and an increase of the catalyst affinityfor quinoline (16). However, the idea moreextended in recent literature is that in addition to their dispersion and structural effects, phosphorous has also a direct influence on the active sites, and particularly in HDN reactions; for example, through sitesassociated with phosphates (15,25) or by direct replacement of some sulfide species by phosphldes like species (17). Relevant to this are the results recently reported on thiophene HDS over NiPSdA1203 catalysts (26) and on different supported NIPS3 and Ni2P catalysts (27) which exhibited thiophene HDS and especially quindine HDN activities comparable to those of commercial NiMoP/A1203 catalysts.…”