节点文献
聚吡咯负载Salen配合物催化CO2与环氧环己烷共聚反应的研究
【作者】 吴静；
【作者基本信息】 昆明理工大学 ， 化学工程（专业学位）， 2016， 硕士
【摘要】 CO2是一种丰富廉价的自然资源,将其与环氧化合物共聚反应生成具有可降解性的高分子是一种环保的绿色过程。参与CO2与环氧化合物共聚反应的催化体系有很多。其中,Salen催化剂对空气和水分具有良好的稳定性以及良好的催化性能而在近几年成为研究热点。但均相Salen催化剂又面临着产物与催化剂难以分离、催化剂易残留等问题。所以,对Salen催化剂通过合理的负载化是实现均相催化剂转变成非均相催化剂的关键。聚吡咯(PPy)作为一种导电高分子聚合物因其制备简单、环境友好已被广泛研究。本文描述了PPy-Cr(Ⅲ)(salen)Cl的制备及表征,并将其用于催化CO2与CHO共聚反应的研究。主要研究内容如下：1.通过快速离心聚合法一步合成了多种形貌纳米结构的PPy并制备了负载型PPy-Cr(Ⅲ)(salen)Cl催化剂。采用红外光谱仪(FT-IR)、X寸线-衍射(XRD)、X射线光电子能谱(XPS)、化学元素分析仪(ICP-MS))、扫描电镜(SEM)、透射电镜(TEM)对载体以及负载型催化剂进行了表征,研究表明Cr(Ⅲ)(salen)Cl成功的负载于PPy上2.对负载型催化剂PPy-Cr(Ⅲ)(salen)Cl用于催化CO2与环氧环己烷的共聚反应进行了分析。主要对CO2与CHO的共聚产物进行了红外光谱(FT-IR)、紫外吸收光谱(UV)和核磁共振光谱仪(NMR)分析。研究了催化剂用量、反应温度、反应时间、反应压力、酸掺杂种类、载体形貌等条件对共聚反应中催化活性、产物分子量等方面的影响。并对各种影响因素进行了优化,将非均相PPy-Cr(Ⅲ)(salen)Cl与均相Cr(Ⅲ)(salen)Cl所制备的共聚产物进行了催化剂残留量对比分析。得到最佳反应条件为：CHO 5ml, m (PPy-Cr(Ⅲ)(salen)Cl)=0.0564 g,m(PPNCl)=0.0282 g,温度80℃,时间1 Oh,压力5 MPa。产物的分子量达到最大9.8×103g·mol-1,TON=4812, PDI=1.19。3. 采用TG.DCS对不同条件下制备的产物热稳定性进行分析,结果发现随着催化剂用量的逐渐增大,催化活性会逐渐增加,分子量也逐渐变大,分子量分布较窄,一定程度上有利于共聚产物热稳定性的提高。而当催化剂的用量继续增加时,由于催化剂过量反而降低了反应速率,使得聚合物的分子量和热稳定性又都有所下降。纳米线形状的PPy负载Cr(Ⅲ)(salen)Cl催化的共聚产物初始降解温度和最大降解速率温度最高,分别达到了293℃和320℃。颗粒的PPy负载Cr(Ⅲ)(salen)Cl催化的共聚产物初始降解温度和最大降解速率温度分别为275℃和291℃。而杆状的PPy负载Cr(Ⅲ)(salen)Cl催化的共聚产物初始降解温度和最大降解速率温度相对较低,分别为262℃和275℃。4.通过1H NMR图谱和13C NMR图谱对不同条件下制备的共聚产物进行了聚合物选择性、产物选择性、碳酸酯单元含量以及立体结构的分析,研究了酸掺杂条件以及助催化剂对产物立体结构的影响,分析结果表明,四种酸(盐酸、硫酸、硝酸、手性樟脑磺酸)掺杂条件下制备的共聚产物聚合物选择性分别为97.1%、96.5%、96.6%和98.7%。产物的选择性达到99%以上,只有硝酸掺杂条件下制备的产物其选择性相对较低为97.8%,同时,盐酸和硫酸掺杂条件下参与的共聚反应几乎专一性的生成聚合物,产物的碳酸酯单元含量分别达到99.6%和99.1%。另外,盐酸、硫酸、硝酸和樟脑磺酸掺杂PPy-Cr(Ⅲ)(salen)Cl催化的产物其间同立构和全同立构比分别为1：0.43、1：0.7、1：0.86、1：0.56。5.研究了助催化剂对CO2/CHO共聚产物立构规整度的影响,发现在没有助催化剂存在时,产物选择性为94.31%,碳酸酯单元含量为80.33%,间同立构和全同立构比值为1：0.97。当加入N-甲基咪唑(N-MeIm)或者4-二甲氨基吡啶(DMAP)助催化剂时,得到的产物选择性从94.31%分别提高到了98.20%和99.25%,碳酸酯单元含量也从80.33%分别提高到了92.72%和95.04%,间同立构和全同立构比也逐渐变大。当采用大位阻的离子型胺盐双(三苯基膦)氯化铵([PPN]C1)作为助催化剂时,可以得到选择性高达99.64%,碳酸酯高于99%的聚合物,同时产物的立构规整度也更高。
【Abstract】 Carbon dioxide(CO2) is the cheapest and most abundant raw material source of carbon. Utilization of CO2 to produce biodegradable aliphatic polycarbonate represents a promising green polymerization process to fix CO2. Among many catalytic systems, (salen)MX, which is developed in recent years, is a macrocyclic ligand metal complex. The homogeneous (salen)MX catalyst has the advantages of low sensitivity to water and air, mild reaction conditions. However, the most of homogeneous (salen)MX catalyst systems suffer from the problems associated with catalyst/polymer separation and catalyst residues. Therefore, the organic metal complex supported on a polymer compound is a good idea to convert homogeneous catalyst into heterogeneous catalyst. Polypyrrole (PPy) which is a conducting polymer has been widely investigated due to its easy preparation, environmental stability and high electrical conductivity. This paper describes the synthetic and structural characterization of the PPy-Cr(Ⅲ)(salen)Cl. The catalyst was prepared for alternating copolymerization of cyclohexene oxide (CHO) and carbon dioxide (CO2). And the effect of copolymerization conditions were studied.1. A variety of polypyrrole nanofibers were synthesized through the centrifugation. As a catalyst carrier, polypyrrole supported Cr(Ⅲ)(salen)Cl have been reported in this paper. The supported catalysts were characterized by FTIR, XRD, XPS, ICP-MS, SEM and TEM. After the study, we concluded that the homogeneous Cr(Ⅲ)(salen)Cl is successfully supported on the PPy.2. The reaction of PPy-Cr(Ⅲ)(salen)Cl for alternating copolymerization of CHO with CO2 have been studied. The copolymerization products were characterized by FTIR, UV and NMR. The reaction conditions of the mass of catalyst, the reaction temperature, the reaction pressure, the reaction time and the doping different acids for the catalytic activity and the molecular weight of the copolymerization have been analyzed. The optimum condations are: CHO 5ml, m(PPy-Cr(Ⅲ)(salen)Cl)=0.0564 g, m(PPNCl)=0.0286 g, T=80 ℃, t=10 h, P=5 MPa。TON=4812, Mn= 9.8×103g·mol-1, PDI=1.19.3. The thermal stability of the products were characterized by Gel Permeation Chromatography (GPC), Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC). We concluded that with the increase of the mass of catalyst, the catalytic activity can reach the maximum, the molecular weight will become large and the thermal stability can be improved. If we continue to increase the amount of the mass of catalyst, the molecular weight and the thermal stability of the products will decline. Futher, the thermi-decomposing temperature and maximum weight-loss temperatures of copolymer using PPy(nanowire shape)-Cr(Ⅲ)(salen)Cl are 275 ℃ and 320 ℃, other copolymer using PPy(particle morphology)-Cr(Ⅲ)(salen)Cl catalyst are 275 ℃and 291 ℃, copolymer using PPy(rod-shaped)-Cr(Ⅲ)(salen)Cl catalyst are 262 ℃and 275 ℃.4. The polymer selectivity, product selectivity and carbonate bond unit content of the copolymer have been analyzed by ~1HNMR and 13C NMR. And the conditions of doping different acids and cocatalyst for the three-dimensional structure of the copolymerization have been studied. The results of the product for four doping acids(HCl, H2SO4, HNO4 chiral camphor sulfonic acid) have shown that the polymer selectivity were 97.1%,96.5%, 96.6% and 98.7% respectively and the product selectivity almost reach 99% except the HNO4(97.8%). Moreover, with the introduction of the HC1 or H2SO4, the carbonate bond unit content of the copolymer were 99.6% and 99.1%. In addition, the ratio of isotactic and syndiotactic were 1:0.43,1:0.7,1:0.86 and 1:0.56 respectively in products catalyzed by by PPy-Cr(Ⅲ)(salen)Cl doped with HC1, H2SO4, HNO4 and chiral camphor sulfonic acid.5. The effect of cocatalysts for the copolymerizations sterepregularity of CO2 with CHO have been studied. Without the presence of cocatalyst, the product selectivity was 94.31%, the carbonate bond unit content was 80.33% and the ratio of isotactic and syndiotactic was 1:0.97. When adding the cocatalyst N-Melm or DMAP, the product selectivity was improved from 94.31% to 98.20% and 99.25% respectively, the carbonate bond unit content was improved from 80.33% and 92.72% or 95.04% respectively, the ratio of isotactic and syndiotactic increase gradually. When adding the cocatalyst PPNC1, the product selectivity reached 99.64%. the carbonate bond unit content was higher than 99% and the copolymerizations sterepregularity was more better than the product without cocatalyst.