SYNTHESIS OF NEW FE-CO BASED METAL OXIDE COMPOSITE-MATERIALS - APPLICATION TO THE FISCHER-TROPSCH SYNTHESIS/

An original synthesis of cobalt-iron alloy/cobalt doped magnetite cata lysts (spinel structure) has been developed, in which cobalt and iron are obtained in the metallic stale without any reducing treatment, The chemical phenomena occurring during the preparation, based upon the c oprecipitation of the hydroxides in a boiling basic medium, are detail ed. By heating under argon, the composition of the metallic phase can be controlled within the range ((Co0.8Fe0.20)-Fe-0) to ((Co0.95Fe0.050 )-Fe-0). X-ray diffraction, thermogravimetric analyses, and X-pay phot oelectron spectroscopy experiments lead to the characterization of the crystalline phases and their location in the bulk and at the surface of the catalysts. The catalytic behavior of these composites in the hy drogenation of carbon monoxide is studied, No reducing treatment is ne cessary for them to be active for the Fischer-Tropsch synthesis. Moreo ver, an efficient treatment for protecting the spinel phase against re duction and subsequent carburization is established, The ability of su ch catalysts to produce C-2-C-4 olefins is also discussed. (C) 1998 Ac ademic Press.