Oxidation Reduction Behavior of Iron-Bearing Olivines (Fe_xMg_(1-x))_2SiO_4 Used as Catalysts for Biomass Gasification

摘要

Natural iron-bearing olivines (Fe_xMg_(1-x))_2SiO_4 have been recognized as one of the most promising tar-cracking catalytic materials for fluidized bed biomass gasification to produce syngas (H_2 + CO).Iron present in the olivine significantly influences its catalytic activity.However,the Fe°-active phase cannot be obtained by the reduction of olivine under the catalyst working conditions.A better understanding of olivine's behavior in oxidizing-reducing conditions is crucial for control of its catalytic properties.In this paper,we have demonstrated how the oxidation of iron-bearing olivines leads to the formation of reducible iron oxides dispersed in the iron-depleted olivine matrix.The choice of oxidation-reduction conditions permits us to control the amount of iron extracted from the olivine structure.The mechanism of the oxidation-reduction behavior of a natural olivine has been studied by ~(57)Fe Mossbauer spectroscopy,X-ray diffraction (XRD),scanning electron microscopy (SEM),and temperature-programmed reduction (TPR).