Recyclable Ligand-free Heterogeneous Mesoporous Polymer-based Pd Catalysts For Heck Coupling Reaction In Aqueous Media

A new mesoporous polymer-based material integrated with quaternaryammonium phase transfer agent is ifrstly synthesized by a micelle-templated method，and then loaded with Pd which is stabilized by the quaternary ammonium salt. Thecatalysts possess the ordered mesostructure, uniform mesopores (3-7nm), highsurface areas (250-3802m/g)，functional phase transfer agent groups (8.5-13.0wt%),and well dispersed Pd nanoparticles (5-10nm). The ligand-free mesoporous Pdcatalysts are highly active in the Heck coupling of bromobenzene and styrenederivatives to give trans-stilbene in high yields, without the need to exclude air andusing water as a solvent. The catalyst samples exhibit high stability and can be reusedat least12times without any additional activation treatment.3-mercaptopropy1-functionalized silicas have been used as selective trapping agents toprobe the involvement of leached palladium species during the Heck couplingreaction. This method，together with hot infiltration proves the negligible leaching ofPd. The comparison of the catalytic performance with other mesoporous Pd catalystson silica, carbon, and resins are also given. The high activity and stability for thepresent catalyst is possibly related to the quaternary ammonium group, well dispersedPd nanoparticles and uniform mesopores.The thesis is composed of two chapters. The first chapter is a literature review,including the synthesis and applying of mesoporous material，the research progress ofpalladium catalyst when it is used in coupling reaction.The second chapter presents synthesis of a new type of quaternary ammoniumsalt-ifmctionalized palladium-containing mesoporous carbon silica catalysts. Thequaternary ammonium salt-functionalized organic-inorganic ordered mesoporous hybrid carbon-silica materials were synthesized via a surfactant-templating method byusing soluble phenolic resins and tetraethyl orthosilicate (TEOS) as carbon andInorganic silica precursors using Octadecyldimethyl(3-trimethoxysiIylpropyl) ammo?nium chloride as organic silica and the triblockcopolymer PI23as astructure-directing agent,ethanol as solvent.Small-angle XRD, TEM and N2sorptionresults reveal that the catalysts have the ordered2-D hexagonal mesostructure, highsurface areas (-3002m/g), large pore volumes (?0.483cm/g), uniform pore sizes(?4.7nm). And the nanoparticles are highly dispersed in the mesoporous carbon-silicawall.Then the catalyst is applied to the coupling reaction of bromobenzene andstyrene in water medium and exhibits a high yield of trans-stilbene of?88%.Compared with other kind of Silicon or carbon-based catalyst, it exhibits a verydistinct advantage.