Nuclear gamma ray resonance observation of the activation process in Raney iron and Urushibara iron catalysts

Abstract

The phases that form when Raney iron and Urushibara iron catalysts are activated have been studied utilizing 57Fe nuclear gamma ray resonance. For Raney iron catalysts four phases are observed in the activated catalyst; residual aluminum-depleted Raney alloy, Fe(OH)2, [alpha]-Fe and Fe3O4. The relative proportions of phases present is a sensitive function of leaching temperature and time. For Raney iron catalysts, and for Urushibara iron catalysts prepared using aluminum, no alloying of aluminum into the activated phases is observable. For Urushibara iron catalysts prepared using zinc, there is considerable alloying of iron and zinc. Evidence is presented to show that when the catalyst is generated at low temperatures Fe(OH)2 is a precursor phase for metallic Fe in Raney Iron. A similar situation seems to exist for the Urushi-bara catalyst prepared using aluminum. The alloying behavior of the iron catalysts can be understood on the basis of the nature of the intermediate phase. The large amounts of Fe3O4 present in Raney iron prepared at elevated temperatures raises some questions concerning the catalytically active phases in such materials.