Abstract:

The Ni(NO3)2/NaY and NiO/NaY dispersed systems were studied by XRD,EXAFS, and TPR methods. It has been found that Ni(NO3)2 is more readily dispersed on NaY than NiO. The dispersion threshold of NiO on NaY has been determined by XRD quanitative phase analysis, and it amounts only to 2% of the close packed monolayer capacity. Before the dispersion threshold NiO on the zeolite exists as the dispersed NiO phase and small NiO crystallites outside the zeolite cage. The dispersed NiO phase is more difficult to reduce than the small NiO crystallites. As the NiO content in the sample is increased above the dispersion threshold, the small NiO crystallites outside the zeolite cage grow into larger crystallites detectable by XRD.

Key words: Ni(NO3)2/NaY, NiO/NaY, Dispersion threshold, Dispersion state, EXAFS, TPR