R. Palcheva

NiMo/γ-Al2O3 Catalysts from Ni Heteropolyoxomolybdate and Effect of Alumina Modification by B, Co, or Ni

A hydrotreating NiMo/γ-Al2O3 catalyst (12 wt% Mo and 1.1 wt% Ni) was prepared by impregnation of the support with the Anderson-type heteropolyoxomolybdate (NH4)4Ni(OH)6Mo6O18. Before impregnation of the support, it was modified with an aqueous solution of H3BO3, Co(NO3)2, or Ni(NO3)2. The catalysts were investigated using N2 adsorption, O2 chemisorption, X-ray diffraction, UV-Vis spectroscopy, Fourier transform infrared spectroscopy, temperature-programmed reduction, temperature-programmed desorption, and X-ray photoelectron spectroscopy. The addition of Co, Ni, or B influenced the Al2O3 phase composition and gave increased catalytic activity for 1-benzothiophene hydrodesulfurization (HDS). X-ray photoelectron spectroscopy confirmed that the prior loading of Ni, Co or B increased the degree of sulfidation of the NiMo/γ-Al2O3 catalysts. The highest HDS activity was observed with the NiMo/γ-Al2O3 catalyst with prior loaded Ni.

The effect of nickel on the component state and HDS activity of alumina-supported heteropolytungstates

Hydrotreating Ni heteropolytungstate catalysts have been prepared by impregnation of γ-Al2O3-alumina with solutions of H3PW12O40 acid and its Ni salt. The nickel content is varied by adding Ni(NO3)2 salt. The calcined samples are characterized by BET, IR, TPR, and XPS techniques. The catalytic activity is tested for HDS of thiophene. It is shown that the initial heteropolyanion, its lacunary analog, and nickel substituted heteropolyanion are present on the surface as a result of the interaction between the active component and the alumina support. The mixed NiWS phase formed after sulfidation determines the HDS activity of the catalysts.

Hydrodesulfurization activities of NiMo catalysts supported on mechanochemically prepared Al-Ce mixed oxides

Abstract Al2O3-CeO2 supports containing 1-10 wt% Ce were prepared mechanochemically by milling aluminum and/or cerium nitrates with NH4HCO3. Heteropolymolybdate, (NH4)4NiMo6O24, was used as the precursor of the Ni and Mo to prepare NiMo6/Al2O3-CeO2 components in catalysts by impregnation method. The physicochemical properties of the catalysts were determined using chemical analysis, X-ray diffraction, temperature-programmed H2 reduction, temperature-programmed NH3 desorption, X-ray photoelectron spectroscopy (XPS), and the Brunauer-Emmett-Teller method. The catalyst acidity decreased with increasing Ce concentration in the support. XPS showed that the NiS/MoS ratio decreased two-fold for the Ce-modified alumina support. NiMo6/Al2O3, which had the highest acidity, showed the highest activity in hydrodesulfurization of 1-benzothiophene (normalized per weight of catalyst). The concentration of surface MoOxSy species (which is equal to the concentration of Mo5+) gradually decreased to zero for catalysts with Ce concentrations ( 10 wt%. However, the activities of all the catalysts prepared mechanochemically from Al2O3 and Al2O3-CeO2 supports significantly exceeded that of a reference NiMo6/Al2O3 catalyst prepared by impregnation method using the same precursor and with the same composition.