The Preparation Of Hydrotalcite Supported Nanocrystalline Palladium Catalysts And Their Catalytic Mechanism For Suzuki Cross-Coupling Reaction

In this paper, hydrotalcite supported with different morphology of nanocrystalline palladium catalysts were prepared and their catalytic properties and mechanism for suzuki cross-coupling reaction were studied.Palladium, a precious metal catalyst, has been widely used as a variety of catalytic organic coupling reactions with good efficiency and selectivity. Layered double hydroxides (LDHs), a family of multifunctional lamellar clays, are existed as a form of natural minerals, moreover, the hydrotalcite surface area is big and moderately-priced. With Mg2Al-NO3LDH as a precursor, PdCl42--LDH has successfully synthesized by ion exchange method. On this basis, hydrotalcite supported nanocrystalline palladium catalyst was prepared by reduction reaction, with modulated matter ratio, reaction time and temperature. The supramolecular structure and chemical composition of the resulting materials were confirmed by XRD, FT-IR and elemental analysis. TEM and HRTEM were employed to study the detailed morphology. These have been obtained for hydrotalcite supported nanocubes and nanorods palladium catalyst. Load obtained hydrotalcite nanocube and nanorod palladium catalyst, in which the nanocube crystals of palladium is exposed (100) plane, while for nanorod crystal palladium is mainly exposed the crystal (100) face of side surface and (111) face of the top.TEM shows that hydrotalcites can disperse well for those supported nanocrystalline palladium, and can be acted as a good carrier for dispersion. Moreover, hydrotalcite can provide a basic alkaline environment for the catalytic reaction due to the alkaline property of hydrotalcite. In this thesis, preliminary study of the catalysis for Suzuki cross-coupling reaction under different reaction state was investigated. Furthermore, heterogeneous catalytic mechanism was discussed for the Suzuki coupling reaction at the surface of nanocrystalline palladium, determined by X-ray photoelectron spectroscopy (XPS). In the experiment showed that the catalyst prepared with a relatively high catalytic activity, and the catalytic reaction is a heterogeneous catalysis. And X-ray photoelectron spectroscopy (XPS) on the Suzuki coupling reaction at the surface of nanocrystalline palladium heterogeneous catalytic mechanism was also discussed, and possible mechanism was also raised.