Abstract
Ni/SiO 2 catalysts were prepared by wetness impregnation method (INi) and by a new two-step method (ENien 2.5/600+INi 2.5). The two-step method consists of formation of chemical glue, “nickel nuclei”, having strong metal support interaction with SiO 2 and preparation of the “nickel reservoir” which has weak interaction with support. The nucleation and growth behaviors of such Ni/SiO 2 catalysts in the preparation stage were continuously monitored by in situ EXAFS spectroscopy. The in situ EXAFS spectra of INi catalyst began to change after 320°C and bulk NiO like structure was formed at 500°C heat treatment. The Ni/SiO 2 prepared with the two-step method had larger coordination number of Ni with silica support in the initial stage of in situ monitoring than that of INi catalyst, which showed the coexistence of Ni nuclei and Ni reservoir. The ENien 2.5/600+INi 2.5 had smaller particles of Ni compared with INi after high temperature calcination. The formation of small Ni particles could be attributed to the strong ion-support interaction of nickel nuclei with nickel reservoir in ENien 2.5/600+INi 2.5 catalyst. Slight particle growth occurred after 370°C calcination in Ni/SiO 2 prepared by two-step method.
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