Abstract: The α-Fe_2O_3/NaY zeolite samples were prepared by impregnating NaY zeolite with ammonium ferrioxalate solution and calcining at high temperature. The maximum dispersion amount of α-Fe_2O_3 on NaY zeolite measured with XRD quantitative phase analysis is 0.060 gα-Fe_2O_3/gNaY, which is only 5.5% of the monolayer capacity of α-Fe_2O_3 on NaY according to a close-packed monolayer model. For the first time positron lifetime spectroscopy has been used to detect the dispersion amount of oxide on zeolite. The maximum dispersion amount of α-Fe_2O_3 obtained is fully consistent with that obtained from XRD phase analysis. TPR spectra of the samples show that the reduction of α-Fe_2O_3 on the zeolite consists of two steps, α-Fe_2O_3 is first reduced to Fe_2O_3 at low temperature and then to the metal at higher temperature. Both reduction reactions are ingibited by the strong interaction of the dispersed α-Fe_2O_3 phase with the zeolite.

Key words: α-Fe₂O₃, NaY zeolite, XRD, Positron lifetime spectroscopy