Effect of phosphorus on the hydrodesulfurization and hydrodenitrogenation performance of presulfided NiMo/Al2O3 catalyst

Phosphorus promoted presulfided NiMo/Al2O3 catalysts were prepared by successive incipient wetness impregnation and characterized by XRD, N2-physisorption, TPR and HRTEM. The effect of phosphorus on the hydrodesulfurization (HDS) hydrodenitrogenation (HDN) performance of the presulfided NiMo/Al2O3 catalyst was investigated. The results indicate that the main active phase is type II MoS2 or Ni-Mo-S phase because of their weak interaction with the support. The incorporation of phosphorus in the catalyst enhances the dispersion of MoS2 particles by increasing the stacking number and reducing the slab length. Phosphorus has no influence on the metal-sulfur bonding energies in the Ni-Mo-S phases and bulk MoS2, but it increases the proportion of Ni-Mo-S phases in the metal sulfides. NiMoP-1.2 catalyst (containing 1.2% phosphorus) exhibits high hydrogenation (HYD) selectivity in the HDS of dibenzothiophene (DBT) and high HDN ratio of quinoline, which can be attributed to its high dispersion of the active phase. The HYD activity in HDS and HDN ratio on NiMoP-1.8 catalyst with excess phosphorus (1.8%) is declined due to the aggregation of MoS2 particles and the decrease of the catalyst surface area.