Fabrication Of Catalytic Materials Based On Core/Shell Microspheres

Hollow micro-/nanostructures possess a lot of characteristics such as low density, high surface-to-volume ratio, and low coefficients of thermal expansion and refractive index that make them attractive for catalyst support. Progress in synthesis of hollow particles has provided opportunities for their widespread use in catalysis. While core/shell microspheres are used as templates, hollow structure materials are endowed with not only novel structure, but also new properties and functionalities. The observed high activities of hollow particles are most readily attributed to the high surface areas of the materials, compared to dense spheres of similar size, because their open hollow structure enables both the outer and inner surfaces of the catalyst to come into contact with the reactants, yielding added benefits for the catalytic process. Rattle-type hollow particles with functional cores are frequently used as catalysts. The shell is believed to stabilize the nanoparticle core through the prevention of their coalescence and provide void space for the organic transformation on the nanoparticle, thus enhancing the catalytic erformance. Success in synthetic strategies for hollow structures has inspired multiple variations that continue to drive the rapid evolution of the field.In chapter two, we synthesized macroporous materials with movable catalytic function spheres inside. First, the monodispersed silica spheres were decorated with palladium nanoparticles. Then the polystyrene shells formed on the surface of silica spheres via emulsion polymerization. Finally using silica-palladium / polystyrene core/shell spheres as templates, we obtained macroporous silica materials with movable silica-palladium spheres inside. Besides we investigated the catalytic property of the macroporous materials. We believe that the special structures of the catalyst materials are significative.In chapter three, we synthesized rattle-type hollow particles with functional cores inside. First, we prepared silica/zirconia/polystyrene core/shell spheres via dispersion polymerization. Then the ammonium tungstates were introduced into the zirconia lamellas. Finally we coated the silica/zirconia-ammonium tungstate/polystyrene core/shell spheres with silica shell and obtained rattle-type hollow particles with silica/zirconia-tungsten oxide cores inside. Further more we investigated the catalytic property of the rattle-type hollow materials. The rattle-type hollow catalyst materials have special advantages and potential applications.In summary, using core/shell spheres as templates, we synthesized catalyst support structure with movable catalytic spheres inside and investigated the catalytic property, which will provide novel platform and challenges in the development of catalyst materials with new structure and property.