| Popis: |
Iron oxide-based catalysts supported on titania and zirconia have been investigated as alternatives for the currently used bulk iron oxide dehydrogenation catalysts. The present study focuses on titania-supported catalysts. Catalyst samples were prepared by pore-volume impregnation of commercially available pre-shaped support bodies with solutions of various iron precursor compounds. Transmission electron microscopy (TEM) and temperature-programmed reduction (TPR) revealed that the best microscopic distribution is achieved with ammonium iron citrate. X-ray diffraction (XRD) showed a difference between the investigated supports: on rutile TiO2, iron was present as hematite (Fe2O3), whereas on anatase, pseudobrookite (Fe2TiO5) was formed. When testing the catalytic activity in but-1-ene dehydrogenation, rapid deactivation was observed which could not be prevented by using a catalyst containing potassium. Without potassium, deactivation is attributed to the formation of ilmenite, FeTiO3. With potassium, the iron oxide phase reacts with both potassium and TiO2, which diminishes the activity which initially was present in catalysts without potassium. When a more inert support is used, viz. ZrO2, no solid state reaction is observed, and a stable catalyst is obtained. |
