ON THE PROPERTIES OF SILICA-SUPPORTED BIMETALLIC FE-CU CATALYSTS .2. REACTIVITY IN THE FISCHER-TROPSCH SYNTHESIS

The catalytic performance of bimetallic FeCu catalysts in the Fischer-Tropsch reaction has been investigated. The results show that due to a higher degree of iron reduction the bimetallic copper-rich FeCu catalysts exhibit a higher activity than the monometallic iron catalysts. At high copper levels the activity (as was expected) strongly decreases. It is argued that under Fischer-Tropsch conditions the surfaces of the bimetallic particles consist of iron-iron carbide islets explaining that the effect of copper on the selectivity (increased production of methane, carbon dioxide, and paraffins instead of olefins) becomes apparent only at high copper contents (above 60 at.%). Carburization studies under more severe conditions show that growth of filamentary carbon proceeds not only on the monometallic iron particles but also on the iron-iron carbide islets present in the surface of the bimetallic particles, thus explaining the formation of very thin whiskers. © 1990.