Highly active sulfided CoMo catalysts supported on (ZrO2-TiO2)/Al2O3 ternary oxides

(ZrO2-TiO2)/Al2O3 ternary oxide at 20 mol% Al2O3 (80% ZrO2-TiO2, in turn at 40-60 mol ratio) prepared by controlled co-precipitation (by urea thermal decomposition) of zirconium (ZrOCl2·8H2O) and titanium (TiCl4) chlorides over a ground alumina substrate constitutes a promising material to be used as carrier of sulfided hydrodesulfurization (HDS) catalysts. After calcining (at 500 °C), the ternary oxide presented textural properties (Sg = 387 m2 g−1, Vp = 0.74 ml g−1, mean pore diameter = 7.6 nm) suitable to its utilization as carrier of catalysts applied in the oil-derived middle distillates HDS. As determined by temperature programmed-reduction and Raman and UV-vis spectroscopies ZrO2-TiO2 deposition over alumina substrate resulted in decreased proportion of Mo6+ species in tetrahedral coordination on the oxidic impregnated material. As those species constitute hardly reducible precursors, their diminished concentration could be reflected in enhanced amount of Mo species susceptible of activation by sulfiding (H2S/H2 at 400 °C) over our ternary carrier. Limiting the concentration of zirconia-titania (at 40-60 mol ratio) to 20 mol% in the mixed oxides support allowed the preparation of highly active promoted (by cobalt, at Co/(Co + Mo) = 0.3) MoS2 phase (at 2.8 atoms/nm2), that formulation showing excellent properties in hydrodesulfurization (HDS) of both dibenzothiophene and highly-refractory 4,6-dimethyl-dibenzothiophene. Due to alike yields to various HDS products over CoMo/(ZrO2-TiO2)/Al2O3 and the corresponding Al2O3-supported formulation, presence of similar actives sites over those catalysts was strongly suggested. It seemed that enhanced concentration of octahedral Mo6+ over the oxidic impregnated precursor with (ZrO2-TiO2)/Al2O3 ternary carrier resulted, after sulfiding, in increased amount of MoS2 phase that could be efficiently promoted by cobalt.