NATURE OF ACTIVE COMPONENT IN A FE2O3-MOO3 CATALYST .I. STUDY ON CATALYST REDUCTION AND OXIDATION

The reduction of a catalyst based on Fe2O3MoO3 with N2 H2 and N2 NH3 as reducing mixtures has been studied by a thermogravimetric method. At the same time the products formed have been analyzed by IR and X-ray powder-diffraction techniques. The initial catalyst contains ferric molybdate, which is the first that is reduced (to ferrous molybdate), and molybdic anhydride, which is reduced to MoO2. Thermal treatments of the catalyst at a temperature higher than 600 °C in air flow can lead to irreversible phenomena, such as sintering. Oxidations, following a reduction, must be carried out at T > 450 °C to ensure a total reoxidation of ferrous molybdate, and with an oxidizing mixture containing a low percentage of O2 (e.g., 5%) in nitrogen, to avoid catalyst decomposition due to local overheating. The reoxidation rate is higher than the rate of reduction. The behavior of ferric molybdate during reduction suggests that the combined iron oxide of the catalyst plays a determining role in the oxidation processes of organic molecules carried out in the presence of catalysts based on Fe2O3MoO3. © 1969.