Preparation Of Titanium-Silicon Hollow Microspheres And Its Catalytic Activity

Recently, hollow microspheres are becoming more and more interesting in a broad research field because of their low density, high surface areas, excellent stability and permeability.In this paper, sol-gel/emulsion method is employed to synthesize serial materials with a hollow structure, such as pure silica, P-silica and Ti-silica hollow spheres, taking kerosene and Span-80 as oil phase, the mixture solution of silicon source, deionized water and relevant acid as water phase. Besides, the influences of preparation conditions on the products were studied in detail. Several kinds of characterization methods were used to observe the morphology of the products, such as, polarized light microscope, scanning electron microscopy, N2 adsorption isotherm and X-ray diffraction. Moreover, the catalytic activity of Ti-silica hollow microspheres was explored, which were synthetized via sol-gel/emulsion method and impregnation method, respectively.The silica hollow microspheres were prepared by sol-gel/emulsion method, taking tetraethylorthosilicate as silicon source, nitric acid as catalyst. The fine dispersibility and hollow structure can be proved by polarized light microscope and scanning electron microscopy, in addition, N2 adsorption isotherm and small-angle X-ray diffraction demonstrate the disordered mesoporous in the shell of sample.The doping phosphorus silica hollow microspheres with disordered mesoporous in the shells were prepared by sol-gel/emulsion method, using the same emulsion system described in the second chapter, except that the nitric acid was changed to phosphoric acid. The full-angle X-ray diffraction proves the existence of the 3P2O5·5SiO2 crystalline. The possible reason is that some chemical reactions take place during the hydrolysis-condensation process of tetraethylorthosilicate in the phosphoric acid environment. The silica hollow microspheres were prepared by sol-gel/emulsion method, using the same emulsion system described in the previous chapter, taking water glass as silicon source. The ununiform particle size distribution and the shell with disordered mesoporous are proved via the characterization.Titanium-silica hollow microspheres were synthetized by sol-gel/emulsion method(sample 1) and impregnation method(sample 2) respectively, using tetraethylorthosilicate as silicon source, titanium oxynitrate as titanium source, and the characterization of the structure and being form of titanium were carried out. The catalytic activity of titanium-silica hollow microspheres was investigated by the epoxidation reaction of cyclohexene taking tert-butyl hydroperoxide as oxidant, and the result shows that catalytic activity of titanium-silica hollow microspheres using sol-gel/emulsion method is much better. The large gaps of catalytic activity between of them can be explained by the difference of titanium's being form, with quadridentate titanium dispersed highly in the sample 1 and titanium dioxide even anatase in the sample 2.