Preparation And Stabilization Of Highly Active Palladium Nanoparticles Inside Mesoporous Silica

Nanoparticles have been widely studied in different areas including optics, electrics and magnetics due to their unique size-related properties. As compared to their bulk counterparts, nanostructured materials show different structures and surface atomic configurations, making themselves highly competitive in a variety of realistic applications such as environment protection, energy conservation, and catalysis. However, nanomaterials are also well known for their unstability as a result of the increased surface energy, which makes the stabilization of nanomaterialsanine vitable and emergent task before a full exploitation of the potential of nanomaterials.In this thesis, the main goals are to design simple and effective method to prepare controllable Pd nanoparticles and to grap Pd nanoparticles in the pore of MCM-41.(1) We report a simple and environmentally-benign method for the synthesis of Pd nanoclusters through a continuous etching process. At the existence of L-methionine, newly-formed Pd nanoparticles (larger than50nm) will gradually reduce their size, finally resulting in the formation of tiny nanoclusters with a diameter around1.4nm. A following sol-gel process can encapsulate these highly-active nanoclusters into a silica matrix. These Pd nanoclusters are proved to be promising for a catalytic Suzuki reaction.Due to the composite structure of nanoclusters and silica, the Pd@SiO2catalysts show integrated merits including good catalytic activity, high stability and notable cyclability.(2) Using the interaction between CTAB and noble metal ions, the precious metal ions successfully introduced to the pore of MCM-41, Pd/MCM-41composite materials were prepared. When Pd/MCM-41catalyst Suzuki coupling reaction, the results show that the catalytic performance is excellent, which TOF value of5min was around98.25mm-1and catalytic activity after five circulation has not significantly reduced.In addition, the materials were characterized by XRD, FT-IR, Uv-vis, BET and TEM technologies. The effects of different metal percursor, solvent agent, concentration of surfactant and calcination situation on the morphology of the material were also investigated.