Synthesis And Catalystic Properities Of MNSIO₃ And MNCO₃ Core-Shell Structure

MnSiO3 is an environment friendly catalyst, core-shell structured MnSiO3 has larger specific surface area and better permeability compared with MnSiO3 without a core-shell structure, and showed promising application in sewage treatment. Cerium usually showed excellent chemical and physical properties due to its special electronic structure, it is of great importance to improve the catalyst activity by dopping appropriate amount of cerium in core-shell structured MnSiO3 catalyst. Mn2O3 is widely used in such fields as catalyst materials, magnetic functional materials, electrode materials, etc., and is usually obtained through calcination of MnCO3. The preparation of MnCO3 with a specific structure is an important step to get Mn2O3 with outstanding performance.The study and results of this paper mainly include the following aspects:1. Preparation and characterization of SiO2/MnSiO3 core-shell structureCore-shell structured SiO2/MnSiO3 were prepared via hydrothermal process, with manganese acetate tetrahydrate as source of manganese, silica microspheres as templates, adding ammonia to make the solution alkaline. The impact factors such as the silica size, mixing mode of reactants, molar ratio of raw materials, reaction time, reaction temperature, pH, etc., on the morphology and structure of the products were investigated.2. Preparation and characterization of Ce-doped SiO2/MnSiO3 core-shell structreCe-doped SiO2/MnSiO3 core-shell structure was prepared via hydrothermal process, with cerium nitrate as cerium source, manganese acetate tetrahydrate as manganese source, silica microspheres as templates, adding ammonia to make the solution alkaline. And the products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectrometer (EDS), specific surface area analyzer (BET), temperature programmed reduction (H2-TPR).3. Catalytic performance evaluation of Ce-doped SiO2/MnSiO3Catalytic activity of Ce-doped SiO2/MnSiO3 were evaluated through the experiment in catalyzing potassium permanganate oxidation of trace phenol in water, and Ultraviolet-visible spectrophotometry was used to measure the content of residual phenol in waste water. Effect of reaction time, Cerium doping concentration, catalyst structure and dosage of catalyst on conversion of phenol was also discussed. Phenol conversion increased with the extension of time; Cerium doping can improve the catalyst activity, the optimum concentration of dopant is 3 mol%. Catalyst with hollowsphere structure has higher activity than the core-shell structured catalyst. Within a certain range, the phenol degradation rate rises with the increase of catalyst dosing.4. Preparation and characterization of SiO2/MnCO3 core-shell nanosphereSiO2/MnCO3 core-shell nanospheres were prepared via hydrothermal process, with manganese acetate tetrahydrate and urea as reactants, SiO2 as templates. Comprehensive thermal analyzer (TG-DSC), X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), specific surface area analyzer (BET) were applied to characterize the products. The effect of urea concentration and dosage of silica templates on morphologies of the products were studied.