Effect of the divalent metal and the activation temperature of NiMoW and CoMoW on the dibenzothiophene hydrodesulfurization reaction

alpha and beta trimetallic mixed oxides were obtained from phi(y) layered phase precursors with (NH4)H1.4Ni2.3O(OH)(MoO4)(1.4)(WO4)(0.6) and (NH4)H2Co2O(OH)(MoO4)(1.6)(WO4)(0.4) formulas by calcination at temperatures as low as 673 K. At this temperature, phase transition was confirmed by (TGA and DSC) thermal analysis. Oxides were activated ex-situ under a H2S/H-2 (15%, v/v) mixture at two temperatures: 673 K and 798 K, to obtain metal sulfides phases, which were active catalysts in the hydrodesulfurization reaction of dibenzothiophene. The effect of the (Ni, Co) promoter and the activation temperature were studied to know the behavior and adequate activation conditions. X-ray photoelectron spectroscopy (XPS) and hydrogen temperature-programmed reduction (H-2-TPR) provided useful information about the oxidation states of the metallic species in the mixed oxides, which were related to the catalytic activity in the hydrotreating reaction. Sulfided catalysts were also characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) for understanding their textural and morphological differences. Additional characterization was carried out using BET surface area and elemental analysis. All catalysts were tested in the hydrodesulfurization (HDS) of dibenzothiophene (DBT) at 593 K and 5.5 MPa. The best catalytic behavior was obtained using Ni as promoter, activated at 798 K. Nickel catalysts were more hydrogenating than cobalt catalysts. (C) 2013 Elsevier B.V. All rights reserved.