Effect of sulfiding pressure on the formation of the Ni site on Ni-Mo/Al2O3 and Ni-W/Al2O3

The effect of sulfiding pressure on the surface structure of Ni-Mo (or W)/Al2O3 was investigated in the range of 0.1 to 5.1 MPa by in-situ FT-IR/DRA of adsorbed NO. The distribution of the Ni site and Mo (or W) site on the surface of every catalyst examined was sensitive to the sulfiding pressure, In the Ni-Mo/Al2O3 catalyst, the intensity of the Mo site-band was weaker when the catalyst was sulfided at a pressure above 1.1 MPa than when sulfided at 0.1 MPa, while the Ni site-band was insensitive to the sulfiding pressure. On the other hand, in the Ni-W/Al2O3 catalyst, the W site-band could not be discriminated distinctly in the range of 0.1 to 5.1 MPa and the Ni site-band sensitively decreased with increasing the sulfiding pressure, Comparing the results with those of the physical mixture of Mo(or W)/Al2O3 and Ni/Al2O3, it was suggested that sulfiding induces the interaction between Ni and Mo in Ni-Mo/Al2O3 (or W in Ni-W/Al2O3), and that the interaction between Ni and Mo was promoted by higher pressure sulfiding above 1.1 MPa. (C) 1997 Elsevier Science B.V.