A new approach in the evaluation of the support effect for NiMo hydrodesulfurization catalysts

To evaluate the intrinsic effect of some supports (gamma-Al(2)O(3), SiO(2), TiO(2), ZrO(2)) on the activity of hydrodesulfurization (HDS) catalysts, NiMo catalysts were prepared by adding nickel acetylacetonate (Ni(acac)(2)) to supported molybdenum sulfide. The catalysts were characterized by X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy and then tested in HDS of thiophene and 4,6-dimethyldibenzothiophene (4,6-DMDBT). This preparation method allowed obtaining well-promoted catalysts. A higher percentage (69-80%) of NiMoS phase was observed by XPS for these catalysts than for traditional co-impregnated catalysts (60%). In addition, the catalytic activity measured with those promoted systems was improved especially for TiO(2) and ZrO(2) supported NiMoS catalysts. By combining characterizations, geometrical model and catalytic activities, apparent HDS activities per NiMoS site were evaluated on each support. The high quality of NiMoS sites suggests that Type-II sites have been formed on silica. (C) 2011 Elsevier B.V. All rights reserved.