温敏聚合物负载钯催化剂的制备及其催化性能

Preparation of palladium catalyst supported by thermo-responsive polymer and its catalytic performance

以N-异丙基丙烯酰胺(NIPAAm)和4-乙烯基三苯基膦(DPPS)为单体,偶氮二异丁腈(AIBN)为引发剂,通过溶液自由基聚合制备温敏聚合物P(NIPAAm-co-DPPS);然后将醋酸钯引入到P(NIPAAm-co-DPPS),并加入NaBH_4还原,可得到温敏聚合物负载钯催化剂P(NIPAAm-co-DPPS)Pd(0)。通过调控NIPAAm与DPPS的摩尔投料比,可得到一系列不同转变温度的温敏聚合物;利用~1H NMR、^(31)P NMR、GPC对温敏聚合物的结构进行表征,利用^(31)P NMR、XRD和TEM对所得催化剂进行表征,并通过TG对Pd含量进行分析;以水相中对硝基苯酚(4-NP)的还原为模型反应,研究温度、催化剂用量以及循环使用次数对催化性能的影响。结果表明:P(NIPAAm-co-DPPS)Pd(0)中Pd纳米粒子具有良好的分散性且含量为2.8 wt%;当温度低于其转变温度时该催化剂具有较高的催化活性,转化率较高,且在循环使用10次后,转化率仍保持在98%,而当温度高于其转变温度时转化率显著降低。

Thermo-responsive polymers P(NIPAAm-co-DPPS)were synthesized with solution free-radical copolymerization by using N-isopropylacrylamide(NIPAAm)and 4-vinyltriphenylphosphine(DPPS)as monomers and azodiisobutyronitrile(AIBN)as an initiator.Then,palladium acetate was introduced into P(NIPAAm-co-DPPS)and reduced by NaBH4 to obtain thermo-responsive polymer supported by palladium catalyst P(NIPAAm-co-DPPS)Pd(0).A series of thermo-responsive polymers with different transformation temperatures were obtained by adjusting the molar ratio of NIPAAm and DPPS.The thermo-responsive polymers were well characterized by 1H NMR,31P NMR and GPC;the catalyst was characterized by 31P NMR,XRD and TEM,and the content of Pd was analyzed by TG.The reduction of p-nitrophenol(4-NP)in the aqueous phase was used as a model reaction to study the effects of temperature,catalyst dosage and cycle number on catalytic performance.The results showed that the Pd nanoparticles in P(NIPAAm-co-DPPS)Pd(0)had good dispersity and the content was 2.8 wt%;when the temperature was below its transformation temperature,the catalyst had high catalytic activity,and the conversion rate was high.Besides,the conversion rate still remained at 98%after 10 cycles,but it decreased significantly when the temperature was above its transformation temperature.