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)3Ni(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.