STUDY ON THE REDUCTION BEHAVIOR OF ZIRCONIA SUPPORTED IRON-OXIDE CATALYSTS BY TEMPERATURE-PROGRAMMED REDUCTION COMBINED WITH IN-SITU MOSSBAUER-SPECTROSCOPY

The reduction properties of Fe2O3/ZrO2 catalysts with various Fe2O3 lo ading and the interactions between iron oxide and zirconia have been s tudied by using temperature-programmed reduction combined with in situ Mossbauer spectroscopy, This is shown that the intermediates formed d uring reduction depend strongly not only on the reduction temperature but also on the iron loading, Several iron species such as bulk phase alpha-Fe2O3, small alpha-Fe2O3 particles, and surface iron oxide speci es are found in the zirconia supported iron oxide catalysts, Reduction of the small alpha-Fe2O3 particles is easier than that of the bulk ph ase alpha-Fe2O3. In contrast, the surface iron oxide species are much more difficult to reduce because of their strong interactions with the support, The phenomena of partial oxidation of Fe2+ cations and Fe3O4 to Fe3+ cations in the reduction processes are observed. (C) 1996 Aca demic Press, Inc.