Hydrodesulfurization NiMo catalysts supported on Co, Ni and B modified Al2O3 from Anderson heteropolymolybdates

Recent catalysts of hydrodesulfurization (HDS) reaction consist of CoMo and NiMo phase supported on gamma-Al2O3 support. The support was modified with cobalt nitrate, nickel nitrate, or boric acid and high loadings of Anderson type heteropolyoxomolybdate (NH4)3[Ni(OH)6Mo6O18].7H2O were deposited. Surface area (SBET) and sulfide phase dispersion of the catalysts were determined by N2 physisorption and O2 chemisorption, respectively. Samples were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, infrared and UV-Vis spectrometry, and temperature programmed reduction. The activity of catalyst was measured in HDS of 1-benzothiophene. The preliminary incorporation of Co, Ni and B into the support increased the HDS activity of the deposited NiMo phase. IR and UV-Vis DR data revealed the partial decomposition of the initial Anderson type NiMo complex with a formation of new surface compounds, including heteropolymolybdates and separated polymeric oxomolybdenum compounds. X-ray photoelectron spectroscopy showed that the degree of Mo sulfidation is the smallest for the catalysts prepared over unmodified alumina and boron-modified alumina. The highest degree of sulfidation was found for the catalysts supported over Co-and Ni-modified alumina. The nickel-modified alumina increased the HDS activity and dispersion of the NiMo phase the most, which was associated with the formation of the largest number of active sites.