Activity of Fe2O3 with a high index facet for bituminous coal chemical looping combustion: a theoretical and experimental study

Abstract

In this work, the reactivities of Fe₂O₃(104) and Fe₂O₃(001) at different oxidation states, as well as the regeneration properties, were comparatively studied theoretically and experimentally. Firstly, interactions between a bituminous coal model molecule and the perfect and reduced Fe₂O₃(104) and Fe₂O₃(001) surfaces under different temperatures were investigated by molecular dynamics. The results proved that the perfect and reduced Fe₂O₃(104) surfaces can effectively promote the adsorption of fuel molecules on the OC surface. Further, deep redox properties of Fe₂O₃(104) and Fe₂O₃(001) were studied by density functional theory calculations, which suggests that oxygen transport initiated from Fe₂O₃(104) occurs more easily than from Fe₂O₃(001), which will favor the combustion of coal. Moreover, Al₂O₃-supported Fe₂O₃(104) was synthesized via morphological-control to perform bituminous coal CLC experiments in a thermogravimetric analyzer (TGA). The comparison between reaction of Fe₂O₃(104)/Al₂O₃ and bituminous coal and reaction of bituminous coal and the referenced Fe₂O₃/Al₂O₃ which was prepared by the traditional impregnation method verified that the former shows a higher fuel conversion and less carbon residue. The regeneration of Fe₂O₃(104)/Al₂O₃ was characterized by XRD and SEM. The high miller index surface iron oxide OC is shown to be efficient and rewarding for use in CLC of solid fuel.