TPR and NO adsorption studies of Mo, CoMo and NiMo catalysts supported on Al_2O_3-TiO_2 mixed oxides

摘要

The effect of the support composition on the surface structure of Mo, CoMo and NiMo catalysts supported on TiO_2-Al_2O_3 mixed oxides was characterizd by TPR and FT-IR spectroscopy of adsorbed NO. The incorporation of titania led essentially to an increase in the fraction of easily reduced octahedral polymeric Mo species, this being more pronounced for the promoted catalyst series. Differences in reducibility between the Ni-and Co-promoted catalysts were observed only for the rich-titania based catalysts, From the NO adsroption results, lower extenss of sulfidation for both Mo and promoter (Co or Ni) were observed in the intermediate-titania based catalysts. Possible corrleation between the NO adsorption results and those previously found for HDS activity are discussed.