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

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 Xray 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 H-2 compared to Ni0.3P/Al2O3, and the Ni0.3MoP/Al2O3 catalyst had the highest selectivity (83%) for bicyclohexyl (BCRX) 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. (c) 2007 Elsevier B.V. All rights reserved.