Synthesis,Characterization And Application Of Porous Organic Polymers As Metallocene Catalyst Support

Porous organic polymers?POPs?have received a staggering degree of attention in various areas including heterogenenous catalysis,absorption and separation,owing to their huge surface area,tunable pore size distribution,high dydrothermal and mechanical stability,flexible synthetic strategy,and readily modifiable functionality.In this dissertation,design,synthesis and characterization of functionalized porous organic polymer support were conducted on a commercialization-oriented basis of metallocne catalst.The metallocene/MAO@POP catalysts were prepared,and were evaluated by ethylene polymerization,and the produced polymers also were characterized.In the end,the principal of the synthesis of POP is extended to organic/inorganic composite support.This dissertation consists of following parts:1.Functional porous organic polymers?POPs?{poly?2-hydroxyethylmethylacrylate-co-divinylbenzene?[P?HEMA-co-DVB?]} with different pore structure and morphology were prepared via a dispersion polymerization strategy.The effects of different solvent type,different ethanol/H₂O volume ratio in the mixture solvent,and?HEMA?/DVB molar ratio on specific surface area and porosity were investigated.Non Local Density Functional Theory?NLDFT?simulation based on nitrogen sorption porosimetry and scanning electron microscopy?SEM?were used to study the pore structure and morphology of the prepared P?HEMA-co-DVB?particles.The results showed a trend that P?HEMA-co-DVB?particles with higher specific surface area and lower average pore diameter were obtained in ethanol/deionized water mixture solvents with better thermodynamic compatibility,however,when different types of solvents were used,higher average pore diameter?14.5 nm?and total pore volume?0.923 cm3/g?were achieved in a good thermodynamic compatible solvent-ethyl acetate.The HEMA functional comonomer could also be a good pore-adjuster,and a shift of pore size distribution to the right was observed when increasing HEMA/DVB molar ratio from 1:4 to 1:1.The SEM results showed that the surface morphology and aggregating form of the prepared POPs can vary dramatically according to different solvents and HEMA content.Furthermore,the prepared functional P?HEMA-co-DVB?particles exhibited good thermal stability with well-preserved pore structure.That provides a feasible route to preparation of functionalized PDVB particles with controllable pore structure and particle morphology.In the ethylene homopolymerization evaluation of supported metallocene catalysts,these nanoporous polymers support reveal better catalytic activity compared with silica,which exhibits great potentials for future application in polyolefin catalysis industry.2.Poly?2-hydroxyethylmethylacrylate-co-divinylbenzene?[P?HEMA-co-DVB?]particles were prepared by using metal oxide as a particle-forming template.The effects of Fe₃O₄/monomer mass ratio,sonification of Fe₃O₄ nano-beads aggregates,and other types of metal oxide template on pore structure and morphology were investigated.The results showed the metal oxide could be a good particle-forming template to obtain suitable particle morphology and pore structure of the P?HEMA-co-DVB?.A shift of pore size distribution to the right or increase of pore size abundance of the prepared P?HEMA-co-DVB?particles was observed when increasing the Fe₃O₄/monomer ratio from 0 to 7%,and the specific surface area?SSA?and the total pore volume?PV?of the prepared P?HEMA-co-DVB?particles increased dramatically with 248 g/m2 of SSA and 0.394 g/ml of PV,when 1.5 wt%Fe₃O₄/monomer was added.The SSA and PV of the final P?HEMA-co-DVB?also increased dramatically after sonification of the Fe₃O₄ nano-beads aggregates,however,the bulk density of the support decreased.Larger PV?0.488 cm3/g?and average pore diameter?12.1 nm?of the prepared P?HEMA-co-DVB?particles were obtained with a relatively high HEMA content.That provides a feasible route to prepare functional POP supports with controllable pore structure and particle morphology.In the ethylene homopolymerization evaluation of supported metallocene catalysts,compared to the conventional silica support,these nanoporous polymeric support shows better catalytic activity and great potentials for commercialization.3.POP-supported Metallocene catalysts were prepared using P?HEMA-co-DVB?samples,and the produced polymers were characterized.The results showed that the pore size and pore size distribution of the supported metallocene catalysts are mainly depended on the prepared POP supports.Generally,the higher the SSA of support is,the higher the SSA of the supported metallocene catalyst,vice versa.Compared to silica support,the POP supports provide a much closer analogue to the environment prevailing in homogeneneous polymerization,and the molecular weight distribution of prepared PE is generally narrower.Pore structure of the supported metallocene or the POP support could influence the molecular weight dramatically,with POP supports prepared in a similar condition,the smaller the pore size of the POP supports or the metallocene catalysts are,the higher the molecular weight of the preduced PE,due to the effect on the diffusion velocity of the comonomer or chain transfer agent,etc.The molecular structure and properties?molecular weight/molecular weight distribution?TREF and DSC results?of the produced PE could be influenced by the pore structure of the POP supports or the supported metallocene catalysts,although those properties are manily depended on the metallocene complexes supported on the POP support.The SEM exhibited that the morphologies of the prepared PE vary consisting of fila and beads.4.Functionalized POP supports were prepared choosing different functional comonomers.The results showed that the pore structure,morphology and bulk density of prepared POP supports changed dramatically due to the solubility parameter differences of the chosen fuctional comonomer and the used solvent system with the produced POP supports.General speaking,highly porous POP supports with relatively high bulk density could be obtained using thermodynamic compatible solvents and comonomers.Functionalized POP supports with reanoable pore sturcutre and bulk density were prepared in dual or triple comonomers,such as HPMA-DVB,HEMA-DVB-St,HEMA-DVB-VBC,etc.Therefore,based on the principle of the design and synthesis of functionalized POP supports,POP supports with SSA,PV and bulk density suitable for industrial application for metallocene catalyst could be obtained.5.Organic/inorganic composite supports were prepared based on above-mentioned synthesis strategy.The results showed that the prepared organic/inorganic composite supports obtained bad porosity and morphology,and low bulk density when hydrophobic inorganic materials,such as hydrophobic TiO₂ and TS 610 SiO₂,were used.While hydrophilic inorganic materials,such as hydrophilic TiO₂ and montmorillonite?MMT?were used,the prepared organic/inorganic composite supports obtained good porosity and morphology,and relatively high bulk density.