Study on surface morphology and crystal structure of precipitated iron catalysts of FTS for reduction conditions

摘要

The precipitated iron catalyst was prepared by co-precipitation. The surface morphology of catalyst was investigated under different reduction conditions by SEM(S-250, USA). Under H2-reductuion, the surface morphology of catalyst had the obvious changes, which the diameter reduced, adhered together, came into being wads considered as a group. But the surface morphology of catalyst had not almost change under CO-reduction. The crystal structure of catalyst was studied under different reduction conditions by XRD (Rigaku D/max, Japanese). It was found that the catalyst was reduced thoroughly with H2, but it wasn't with CO. The contents of catalyst consisted of Quartz-SiO2 ￡?Hermatite-Fe2O3 and Fe2O3-Iron Oxide. Before the reduction process of the catalyst, the phases of the catalyst were Hematite (Fe2O3), Potassium Iron Oxide (K6Fe2O6), Iron Silicon Oxide (Fe2.35Si0.65O4), etc. The crystal structure of catalyst converted into the metallic phase with H2 reduction. However, most of the iron converted into Iron Oxide (Fe3O4) with CO-reduction. And the predominant phase in a sample of mature catalyst is χ-Fe5C2, which is the active phase in the FTS.