Abstract
Commercial Ni(Co)Mo/gamma-Al2O3 catalysts were modified by the addition of Pd and Ru in order to enhance their hydrogenation function as required for the simultaneous elimination of sulfur, nitrogen and aromatics from a gasoil. The ternary catalysts were prepared by wet impregnation of the commercial samples with Ru and Pd salt solutions. The oxide precursors were characterized by S-BET, TPR, XRD, XPS and IR of adsorbed pyridine. The catalysts were tested in their sulfided forms to evaluate their activity in the hydrodesulfurization (HDS) of dibenzothiophene (DBT) and in the hydrotreating (HDT) of a straight run gas oil (SRGO; 0.11, 0.55 and 1.16 wt% of S). Catalyst screening in the HDS of DBT showed that: (i) the presence of isolated RuS2 phases located on the catalyst surface contributed to overall catalytic activity and improved the catalyst hydrogenation function, (ii) catalyst doping with Ru was more effective than its doping with Pd, (iii) maximum activity was obtained at a Ru loading of 0.5 wt%, (iv) the NiMo catalyst formulation was more effective than its CoMo counterpart, and (v) a life test (87 h) performed on the 0.5%Ru/NiMo catalyst showed that this catalyst was less prone to deactivation than the NiMo reference sample. In the hydrotreatment of a SRGO (S = 0.55 wt%), the sulfide 0.5%Ru/NiMo/Al2O3 catalyst proved to be more active in the HDS and HDA reactions than a commercial NiMo/Al2O3 one. (C) 2008 Elsevier B.V. All rights reserved.