HDN and HDS of model compounds and light gas oil derived from Athabasca bitumen using supported metal phosphide catalysts Original Research Article

Co0.4Ni2P and Ni0.3MoP catalysts, supported on Al2O3, fluorinated Al2O3 (Al2O3-F) and Mobil Catalytic Material (MCM-41), have been prepared from metal phosphate precursors by temperature-programmed reduction (TPR) to 1200 K. The catalysts have been characterized and their activity determined for the hydrodenitrogenation (HDN) of carbazole, the hydrodesulphurization (HDS) of 4,6-dimethyldibenzothiophene (4,6-DMDBT) and the HDN and HDS of a light gas oil (LGO) derived from Athabasca bitumen. The formation of metal phosphides after TPR was confirmed by both X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The acidity of the catalysts, as measured by n-propylamine uptake, was determined by the support acidity and increased in the order Al2O3 < Al2O3-F < MCM-41. Activity measurements using model compounds showed that increased support acidity led to increased cracked products. The Co0.4Ni2P/Al2O3 catalyst promoted the direct desulphurization of 4,6-DMDBT at 583 K and 3.0 MPa H2 compared to Ni2P/Al2O3, and the Ni0.3MoP/Al2O3 catalyst had the highest selectivity (83%) for bicyclohexyl (BCHX) among the catalysts tested for the HDN of carbazole at the same conditions. The Ni0.3MoP/Al2O3 also had the highest activity for both the HDN and HDS of LGO, compared to Co0.4Ni2P/Al2O3 and a conventional NiMoS/Al2O3 catalyst that also contained P. The low activity of the Co0.4Ni2P/Al2O3 catalyst was attributed to low metal dispersion, a high S uptake and the possible formation of less active phosphosulphide species such as NiPS3, on this catalyst.