Study On Morphology, Crystal Surface Control And Catalytic Performance Of Iron Oxide - Based Catalytic Materials

Recent years, with the rapid development of nanotechnology, the composition, morphology and size of solid catalysts can be controlled using buttom-up chemistry technology at nanometer level. Extensive studies over the past few decades have demonstrated that the particle size and morphology of catalyst on the nanometer scale profoundly affects its performance. This effect is more significant for the active facet of the selective exposure material. According to the controllable synthesis of morphology of heterogeneous catalysis nanomaterials, the active facet of the materials can be exposed selectively, which can substantially improves the catalytic activity, selectivity, and stability and became a research hotspot of the heterogeneous catalysis nanomaterials. α-Fe2O3nanomaterials is the most stability iron oxides, which has widely application value due to its low cost, environment friendly and high thermal stability characteristics. This paper focuses on controllable synthesis of the particle size and morphology of α-Fe2O3nano materials and its composite materials, the influence morphology of catalytic materials make on CO catalytic activity is also investigated.The shape-controllable α-Fe2O3nanomaterials were successfully synthesized by novel hydrothermal synthesis process. On this basis, CeO2/α-Fe2O3, Au/α-Fe2O3composite oxide catalysts are prepared through hydrothermal method and impregnation method respectively, and the composite catalysts were characterized by XRD, BET, H2-TPR, the catalytic activity of composite catalysts with CO oxidation was investigated on fixed-bed reactor. Through experiment, some conclusions are acquired.(1)The effect of precipitation temperature, NH2CONH2-FeCl3molar ratio, reaction temperature, reaction time, calcination temperature, heating rate for the morphology of catalyst materials are investigated in detail. The results shown that materials which precipitate at20℃possess best crystallinity; when NH2CONH2-FeCl3molar ratio is1.5and react at100℃for24h, the rod-like α-Fe2O3materials with good crystallinity was synthesized. In addition, calcination temperature and heating rate have effect on the morphology of catalyst, high calcination temperature result in sintering.(2) NH4H2PO4can substantially affect morphology of catalyst, which can improve the anisotropic grain growth of α-Fe2O3nano-structure through preferential adsorption. We synthesized the α-Fe2O3nanomaterials with ring, spherical, cube, and raft-like structure with the NH4H2PO4additive. The rod-like α-Fe2O3materials with exposure{110} facet were also successfully synthesized.(3) The catalytic activity of composite catalysts CeO2/α-Fe2O3, Au/α-Fe2O3with CO oxidation was investigated; the results showed that catalytic activity of catalysts substantially depend on the morphology.