The influence of preparation and doping on the reducibility of hematite by hydrogen

Samples of hematite and of hematite doped with 1 at% lithium and 1 at% vanadium are prepared by the hot kerosene drying technique. The doped samples are also prepared by an impregnation method. The various samples are used to study the reduction with hydrogen to form iron. The results indicate that the rates of reduction are strongly influenced by the particle size of the initial samples and by the repartition of the additive in the bulk and surface layer of the hematite particles. It has been shown that both additives can retard the rate of reduction. The lithium exerts its maximum influence when present in solid solution and vanadium when concentrated in the surface layer. The importance of a careful preparation of samples to be used for reduction studies, is stressed.