Comparison of P-containing γ-Al2O3 supported Ni-Mo bimetallic carbide, nitride and sulfide catalysts for HDN and HDS of gas oils derived from Athabasca bitumen

Phosphorus containing γ-Al2O3 supported bimetallic Ni-Mo carbide, nitride and sulfide catalysts have been synthesized from an oxide precursor containing 12.73 wt.% Mo, 2.54 wt.% Ni and 2.38 wt.% P and characterized by elemental analysis, pulsed CO chemisorption, surface area measurements, X-ray diffraction, temperature-programmed reduction and DRIFT spectroscopy of CO adsorption. DRIFT spectroscopy of adsorbed CO on activated catalysts showed that carbide and nitride catalysts have surface exposed sites of Moø+ (0 < ø < 3) and Moδ+ (0 < δ < 2) sites respectively, and these sites are susceptible to sulfidation with H2S/H2 mixture at 370 °C. The hydrodenitrogenation (HDN) and hydrodesulfurization (HDS) activities of the bimetallic Ni-Mo carbide, nitride and sulfide catalysts were compared against commercial Ni-Mo/Al2O3 catalyst in a trickle bed reactor using light gas oil and heavy gas oil derived from Athabasca bitumen in the temperature range 340–370 and 375–400 °C respectively at 8.8 MPa. The gradual transformation of Ni-Mo carbide and nitride phases into Ni-Mo sulfide phases was observed during precoking period, and the formed Ni-Mo sulfide phases enhanced the HDN and HDS activities of carbide and nitride catalysts. The γ-Al2O3 supported Ni-Mo bimetallic sulfide catalyst was found to be more active for HDN and HDS of light gas oil and heavy gas oil than the corresponding carbide and nitride catalysts on the basis of unit weight.