AN FE-57 MOSSBAUER-SPECTROSCOPY AND EXAFS STUDY OF THE HYDROGEN PRETREATMENT OF TITANIA-SUPPORTED IRON-RUTHENIUM CATALYSTS

The changes in composition and structure which are induced in a titania-supported iron-ruthernium catalyst following treatment in hydrogen have been investigated in situ by57Fe Mössbauer spectroscopy and by EXAFS. The results show that ruthenium dioxide is readily reduced at temperatures below ca. 500°C to ca. 20 Å clusters of metallic ruthenium whilst α-Fe2O3 is partially reduced at 130°C to Fe2+ and Fe0. The Fe3+ which is formed by the reoxidation of Fe2+ under the reducing conditions at 500°C segregates to the interface of the bimetallic phase and the titania support. It is suggested that continued treatment at 700°C produces a high dispersion of iron which is coordinated to oxygen atoms of the support. The ca. 20 Å clusters of metallic ruthenium may be envisaged as being anchored to the support via iron-ruthenium bonds © 1990 J.C. Baltzer A.G. Scientific Publishing Company.