Comparative studies of the CoMo/MgO, CoMo/Al₂O₃ and CoMo/MgOMgAl₂O₄ catalysts prepared by a urea-matrix combustion method

Three CoMo supported catalysts with different supports, Al ₂O₃, MgO and MgOMgAl₂O₄, were prepared by a urea matrix combustion method. The physicochemical properties of the catalysts were characterized by N₂ isothermal adsorption-desorption, powder X-ray diffraction (XRD) and temperature programmed reduction (TPR) techniques. The activity of these catalysts was evaluated in a fixed-bed high-pressure reactor using hydrodesulfurization of dibenzothiophene as a model reaction. The urea matrix combustion preparation method greatly favored the formation of highly dispersed Co- and Mo-oxo species on the support, which had significant influence on the hydrodesulfurization (HDS) activity. XRD analysis showed that MgO was more sensitive to the deposition of Co-O or Mo-O species than Al₂O₃ and MgAl₂O₄; the former might be potentially used as an indicator of the Co- and Mo-oxo species formation. Among these catalysts, CoMo/MgOMgAl₂O₄ exhibited a high HDS activity.