Construction And Catalytic Application Research Of The Lamellar Niobium Based Nano-composite Materials

In this paper, KNb3O8was synthesized through polymerized complex method. HNb3O8nanosheet (e-HNb3O8) was prepared by exfoliation and aggregation from layered HNb3O8, which was obtained by protonated KNb3O8.The nanosheets sol was used to obtain exfoliation-restacking TiO2/Nb3O8and ZrO2/Nb3O8nano-composites samples by compositing with transition metal oxide sol TiO2and ZrO2, respectively. One can get superacid SO42--TiO2/Nb3O8material after dipping the ZrO2/Nb3O8nano-composites into sulfuric acid solution. The as-prepared samples were characterized by means of HRTEM, EDS, XRD, LRS, FT-IR, NH3-TPD and other physical and chemical testing means. The catalytic activity of the as-prepared samples were investigated through degradation for methylene blue and selective nitration of toluene, respectively.The research results revealed that HNb3O8prepared by PC method possess lamellar morphology. The XRD peaks of HNb3O8are shifted to the small angle, which could be caused by the interlayer hydrated proton. The samples retained some laminate structure, but the crystallinity of the samples decreased significantly after exfoliation-aggregation. TiO2/Nb3O8and ZrO2/Nb3O8nano-composites samples not only maintain the original structures of the nanosheets, but also present anatase TiO2crystals and tetragonal phase of ZrO2crystals on its surface.The degradation rate of Methylene Blue over the as-prepared samples show that the KNb3O8and its modified samples are all have good photocatalytic performance. With the interlayer ions (H+or K+) changes, the photocatalytic properties of the samples are changed little. Because TiO2surface almost has no acidity and the methylene blue is alkaline, TiO2adsorption properties for degradation was poor. Therefore, the photocatalytic performance of TiO2is also poor. However, the photocatalytic performance of TiO/Nb3O8and e-HNb3O8are dramatically increased, because they have higher specific surface area and the adsorbing capacity are also enhanced.The catalytic activity for toluene nitration over the as-prepared samples show that the KNb3O8and its modified samples are all have good acid catalytic performance. The acid catalytic properties of the samples are changed little after H+exchanged with interlayer K+. It may be due to the narrow interlayer gallery of HNb3O8, which made the reactant molecules inhibited to contact with the interlayer proton active sites. However, the e-HNb3O8and its modified samples are all have good acid catalytic performance, because they have higher specific surface area, acid amount and acid strength.