HDN and HDS of different gas oils derived from Athabasca bitumen over phosphorus-doped NiMo/γ-Al2O3 carbides

A series of phosphorous-doped γ-Al2O3 supported Ni–Mo bimetallic carbide catalysts (PNiMo2C/Al2O3) with 0–4.5 wt.% Ni, 13 wt.% Mo and 2.5 wt.% P were synthesized and characterized by elemental analysis, pulsed CO chemisorption, surface area measurement, X-ray diffraction (XRD), near-edge X-ray absorption fine structure (NEXAFS), DRIFT spectroscopy of CO adsorption and H2 temperature programmed reduction. XRD indicated the formation of pure β-Mo2C phase in these catalysts, whereas the near edge X-ray absorption fine structure of C K-edge confirmed the formation of carbidic carbons. DRIFT spectra of adsorbed CO revealed that Ni or P addition to Mo2C/Al2O3 catalyst not only increases the number of surface Mo sites, but also promotes the reducibility of Mo. The partial sulfidation of Mo2C phase in the presence of H2S/H2 gas mixture at 370 °C was evidenced by DRIFTS of adsorbed CO. The HDN and HDS activities of these PNiMo2C/Al2O3 catalysts were performed in a trickle bed reactor using light gas oil (LGO) and heavy gas oil (HGO) derived from Athabasca bitumen at 8.8 MPa and compared with the unpromoted Mo carbide (Mo2C/Al2O3), P doped Mo carbide (PMo2C/Al2O3) and Ni promoted Mo carbide (NiMo2C/Al2O3). The P doped Ni–Mo bimetallic carbide catalysts showed enhanced HDN activity compared to the Mo2C/Al2O3, NiMo2C/Al2O3 and PMo2C/Al2O3 catalysts. The maximum N and S conversions, respectively, were obtained over PNiMo2C/Al2O3 and NiMo2C/Al2O3 catalysts containing 2.5 wt.% Ni.