In situ iron-57 Mössbauer spectroscopic investigations of the effect of titania surface area on the reducibility of titania-supported iron oxide

Iron-57 Mössbauer spectroscopy has been used to monitor the reducibility in hydrogen of iron oxides supported on titania of differing surface areas. The results show that although Fe³⁺ in the iron oxide supported on low surface area titania (11 m²g^?1) is not amenable to facile reduction at low temperatures, complete reduction to metallic iron is achieved by treatment at 600°C. The data also show that the extent of reduction at elevated temperatures exceeds that which is obtained on similar silica- and alumina-supported systems. Fe³⁺ in iron oxide supported on higher surface area titania (50 m²g^?1 and 240 m²g^?1) is partially reduced in hydrogen at 235°C to Fe²⁺ but fails to attain complete reduction to the metallic state following treatment at 600°C. The results are related to the different dispersions of iron oxide which can be attained on titania of differing surface area and the consequent interactions between the support and the supported phases.