Abstract:

 A series of NiO/γ-Al_2O_3 catalysts were prepared by sol-gel method. The effects of the methods of preparation, the nickel content and the calcined temperature on the structure and existing forms of nickel species of NiO/γ-Al_2O_3 catalysts were investigated using XRD, XPS and TPR. The results suggested that the interaction between NiO and γ-Al_2O_3 affected the oxidic nickel speies. Nickel oxide was found to appear in the catalysts in three forms, as "free", "dispersed" and "fixed" oxides. The occurrence of the fixed form of the oxide in the catalysts was connected with the formation of nickel aluminate. The effect of the reaction of these different nickel species on the performance of the catalysts was dicussed. For the catalysts prepared by sol-gel method, after calcined at higher temperature, nickel species present as a spinel-like structure solid solution, which could re- strain nickel loss and sintering and improve the thermal stability of catalysts.

Key words: Sol-gel method, NiO/γ-Al2O3, Ni species, Interction between NiO and γ-Al2O3