| In recent years,organic small molecule catalysis has been emerging with rapid development in the catalysis research field.2,2,6,6-tetramethylpiperidine-l-oxyl(TEMPO):as a small molecular catalyst for selective transformation of alcohols to aldehydes/ketones under mild conditions,has attracted widespread attention.However,as a small molecular catalyst,it has some issues on the difficulties of recovery in organic synthesis.Polymers have abundant functional groups,and can easily be modified and functionalized,thus makes them ideal candidates for versatile carriers.Immobilization of TEMPO onto polymers has great advantages in separation,as well as improvement of catalyst stability.Based on this,in this thesis,different strategies of TEMPO immobilization on polymer microspheres,linear polymer and microporous membrane have been developed,the linkage stability,catalytic activity,catalytic reaction mechanism of polymer supported TEMPOs,as well as potential applications have been systematically investigated.The main contents of this thesis are as follows:(1)Immobilization of TEMPO on cross-linked polystyrene microspheres was performed,affording PS-O-TEMPO and PS-im-Cn-TEMPO(n = 4,6,10)catalyst with ether and imidazolium bridging,respectively.It was found that imidazolium bridging could result in higher TEMPO loading,better thermal stability and amphiphilicity,as compared to ether bridging.When used in batch reactors for benzyl alcohol oxidation,PS-im-Cn-TEMPO(n = 4,6,10)showed very good recoverable catalytic performance,with more than 95%after 30 cycles.When PS-im-C6-TEMPO was packed in a fixed bed reactor,it maintained good catalytic activity after 55 h at 10 ?,though the TEMPO loading decreased slightly.(2)A pH-responsive linear amphiphilic polymer-supported TEMPO catalyst(PES-im-TEMPO)was prepared by anchoring TEMPO onto chloromethyl poly(ether sulfone)(CMPES)bridged by imidazole groups.PES-im-TEMPO was not soluble in either water or CH2Cl2,but it could be well-dispersed in CH2Cl2 and self-assembled into nanoaggregates with uniform size.When used in Anelli oxidation system,magnetic stirring can make these nanoparticles spontaneously be absorbed on biphasic interface to stabilize water-in-oil(W/O)Pickering emulsion and prevent droplets coalescence,leading to prominent improve on reaction rate.Compared with free TEMPO,the catalytic rate of PES-im-TEMPO was increased by 1.4 times.(3)A novel pH-responsive SPAEK-C10-TEMPO catalyst was prepared through one-step immobilization of BrC10-TEMPO onto poly(aryl ether ketone)(PAEK)bearing benzimidazole in side chain.The catalyst was applied to the Anelli oxidation system to form a stable Pickering emulsion,and complete conversion of benzyl alcohol could be achieved within 90 s(selectivity>99%).Compared with free TEMPO,the catalytic efficiency was increased by 1.6 times.(4)TEMPO-immobilized amphiphilic diblock copolymers were prepared through RAFT polymerization and subsequent oxidation.The polymers were blended with PVDF to prepare catalytic membranes via phase inversion method,which were further assembled in membrane reactors to perform the catalytic oxidation of alcohols.Through the composition regulation of TMPM,DMA and MMA,catalytic activities of these polymers were evaluated in Anelli oxidation system.Among which,P(TMA-co-DMA-b-MMA)-1 could make benzyl alcohol completely converted into benzaldehyde within 15 s.Furthermore,the effects of blend ratios and other factors on the membrane structure and catalytic performance of the blend catalytic membranes in membrane reactor were investigated. |
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