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

Abstract

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.