The effect of phosphorus on hydrotreating property of NiMo/γ-Al2O3 nitride catalyst

γ-Al2O3 supported P-doped nickel molybdenum (NiMo) nitride hydrotreating catalysts with 12 wt.% of Mo, 3 wt.% Ni and 0–2.5 wt.% P were synthesized by means of temperature-programmed reaction, and characterized by BET surface area analysis, elemental analysis, CO uptake titration, DRIFT study of adsorbed CO, temperature-programmed oxidation (TPO), temperature-programmed reduction (TPR) and temperature-programmed desorption (TPD) of NH3. The activity of the nitride catalysts was studied in a trickle-bed reactor operated at 8.8 MPa and 385 °C in the hydrodenitrogenation (HDN) and hydrodesulfurization (HDS) of heavy gas oil (HGO) derived from Athabasca bitumen. The CO uptakes measurement showed that P addition to NiMo nitride improves the dispersion. DRIFT spectra of CO adsorption evidenced that the number of Mo2+ sites on the surface of NiMo nitride increases with increasing P concentration and reaches optimum with 2.0 wt.% of P. TPD of NH3 indicated an increase of strong acid sites and also strengthening of moderate acid sites in NiMo nitride on P doping. All the nitride catalysts have suffered partial sulfidation during initial period of hydrotreating of HGO. HDN activity of NiMo nitride was promoted greatly by the phosphorus content, reached a maximum with P content of 1.6 wt.%. An increased acidity of P-doped NiMo nitrides accelerated C–N bond breaking and thus enhanced the HDN activity. No significant change was observed in HDS of HGO over NiMo/Al2O3 nitride catalyst on P doping.

The synthesized P-doped γ-Al2O3 supported nickel molybdenum (NiMo) nitride catalysts were characterized, and tested for HDN and HDS of heavy gas oil (HGO) derived from Athabasca bitumen at industrial conditions.Figure optionsDownload as PowerPoint slide