Effect of cerium on the transformation and reactivity of hematite in a reducing atmosphere

Abstract

As is well known, cerium compounds are widely used as promoters in iron-potassium catalysts for the dehydrogenation of alkylaromatic and olefinic hydrocarbons. To determine the mechanism and role of cerium oxide in formation of catalytically active phases (potrassium ferrites), we must first study the effect of cerium on transformation and reactivity of iron oxide, which comprises 50 to 80% of the catalyst and participates in ferrite formation. In this work, the thermal behavior of cerium oxalate and the Fe2O3-CeO2 model system, the main components in the production of iron-potassium catalysts, is examined by X-ray diffraction, thermal analysis, particle size distribution analysis, low-temperature nitrogen adsorption, and temperature-programmed hydrogen reduction under heating in air. It is shown that cerianite exhibits greater lability than hematite. It is established that introducing cerium into hematite improves the reactivity of the Fe2O3-CeO2 system, and the partial reduction of Fe2O3 takes place upon its heating. The results from this work will be used in developing new iron-potassium catalysts with enhanced catalytic activity in the dehydrogenation of isoamilenes into isoprene.