NiMo catalysts supported on Al, Nb, Ti or Zr-containing MCM-41 for dibenzothiophene hydrodesulfurization

xMCM-41 materials (x = Al, Nb, Ti or Zr) with nominal x loading of 0.5 mmol/g were prepared by chemical grafting of Al₂O₃, Nb₂O₅, TiO₂ and ZrO₂ precursors and used as supports for NiMo/xMCM-41 catalysts. Small-angle XRD characterization of supports showed typical patterns of solids with hexagonal arrangement of mesopores. After the deposition of Ni and Mo oxide species on the supports a decrease in their long-range pore arrangement was observed. Nevertheless, the prepared NiMo catalysts possessed high specific surface areas and pore volumes. Powder XRD patterns showed the formation of the MoO₃ crystalline phase in the NiMo/MCM-41 reference. This phase was not detected in the catalysts supported on xMCM-41 materials. An increase in the dispersion of MoO₃ species with the incorporation of alumina, niobia, titania and zirconia in the MCM-41 support was due to the stronger interaction of Mo and Ni oxide species with xMCM-41 materials (H₂-TPR and UV–vis DRS). Surface modification of the MCM-41 with different metal oxides increased the dibenzothiophene conversion and pseudo first-order rate constants. This effect was more evident for the NiMo/TiMCM-41 catalyst. Selectivity of the catalysts (product distributions) was also affected by the incorporation of Al-, Zr-, Ti- and Nb-oxide species in the support.