负载型纳米聚苯胺的可控合成及其稳定的Pickering乳液烯烃催化氧化性能研究

Olefin oxidation plays an important role in the development of drug intermediates. The traditional method for olefin oxidation often results in severe environmental pollution. Polyaniline, on the other hand, is a new and efficient polymer catalyst for olefin oxidation. However, several issues with bulk polyaniline catalyst remain to be solved, including the low catalytic efficiency, poor selectivity towards target product, difficulty in catalyst recycling, limitation of mass transportation of substrate to the catalyst/oxidant surface and the indistinctive oxidation mechanism of olefins, etc. To address these issues, it is proposed in this project to catalytic oxidation of olefins in Pickering emulsion stabilized by heterogeneous supported nano-polyaniline. The heterogeneous supported nano-polyaniline is facilely constructed by in-situ/polymer gel induced polymerization method with clay minerals and polymer cavity structure material as support. The supported nano-polyaniline stabilized Pickering emulsion olefin catalytic oxidation system has the following advantages: 1) the unique properties inherent in Pickering emulsions will ensure a large active area, the separation of the product from the reactants and the fast and simple procedures employed for demulsifying/re-emulsifying during the olefin catalytic oxidation process; 2) the in-situ/polymer gel induced polymerization will avoid the peeling off the supported nano-polyaniline and the use of surfactants in the synthesis process; 3) the olefin catalytic oxidation scope of the supported nano-polyaniline can be extended and the stability of the Pickering emulsion can be adjustable by taking advantage of the unique doping mechanism of polyaniline; 4) the supports are economically accessible materials, which essentially make the Pickering emulsion-based olefin catalytic oxidation system technically simple and thus practically applicable. Furthermore, the olefin catalytic oxidation activity of the supported nano-polyaniline stabilized Pickering emulsion catalytic system are investigated systematically, including the influence of polyaniline content/doped state, support structure and the stability of Pickering emulsion to reveal the synergistic olefin catalytic oxidation relationship among polyaniline, support and Pickering emulsion and the olefin catalytic oxidation mechanism of the supported nano-polyaniline Pickering emulsion catalytic oxidation system. This work will provide theoretical and scientific foundation for the construction of novel and efficient supported nano-polyaniline stabilized Pickering emulsion olefin catalytic oxidation system and the study of the olefin catalytic oxidation mechanism of polyaniline based catalyst.

烯烃氧化在药物中间体开发中发挥重要作用，传统的氧化方法存在严重环境污染问题。聚苯胺是烯烃氧化的一种新型且有效的催化剂，但本体聚苯胺催化氧化烯烃存在催化效率低、对目标产物的选择性差、催化剂回收利用困难、烯烃与催化剂传质困难、催化氧化机理不清楚等问题。针对上述存在的问题，本项目拟结合Pickering乳液固有特性、聚合物化学改性技术和聚苯胺独特的掺杂机制，以丰富的纳米粘土矿物和聚合物腔体结构材料为载体，原位/聚合物凝胶诱导聚合制备负载型纳米聚苯胺，并以此为固体乳化剂，构建Pickering乳液型烯烃催化氧化体系。通过考察聚苯胺含量/掺杂态、载体结构和Pickering乳液稳定性与烯烃催化氧化性能之间的关系，揭示其协同催化氧化规律和阐明其稳定的Pickering乳液烯烃催化氧化机理。本项目将为新型高效的负载型纳米聚苯胺Pickering乳液烯烃催化氧化体系及其烯烃催化氧化机理的研究提供理论基础。

烯烃氧化在药物中间体开发中发挥重要作用。针对本体聚苯胺催化氧化烯烃普遍存在的问题，本项目以丰富的粘土纳米管和聚合物腔体结构材料为载体，原位/聚合物凝胶诱导聚合制备负载型纳米聚苯胺。通过掺杂酸种类、酸度、载体、温度调节负载聚苯胺的氧化还原态、掺杂度和聚苯胺量。结果表明：掺杂酸为盐酸、酸度为 1 M、载体为多孔纳米棒、0oC下制备的负载型聚苯胺为翠绿亚胺盐、掺杂度较高（39.2%）、聚苯胺含量为48.5%；掺杂酸为磷酸、酸度为 1 M、载体为埃洛石纳米管、室温下制备的负载型聚苯胺偏醌式结构、掺杂度较低（26.6%）、聚苯胺含量为51.8%。以上述制备的负载型聚苯胺作为固体乳化剂，构建Pickering乳液。结果表明：当掺杂酸为盐酸，酸度为1 M下制备的负载型聚苯胺和2:1水/油比下制备的Pickering乳液较稳定，乳液液滴约为14.35um。系统地考察了上述构建的负载型聚苯胺稳定的Pickering乳液的烯烃热/光催化氧化性能。结果表明：最佳的催化剂为PH/1 M/2.04-HCl 和PTH/0.5/1%-HCl；最佳的反应条件为2:1水/油体积比、无溶剂、24 h (PH/1 M/2.04-HCl)、48 h (PTH/0.5/1%-HCl) 、紫外光 (PTH/0.5/1%-HCl)，催化活性与负载聚苯胺的掺杂度和Pickering 乳液稳定性呈正相关。在此最佳催化剂和反应条件下，环己烯转化率分别为98.17%和97.62%，主氧化产物选择性分别为99.50% （环己二醇，热催化）和95.64% （4,4’-联环己烯醇，光催化）。根据上述结果，提出此催化体系高效的烯烃氧化活性源自负载聚苯胺的可逆氧化还原反应和聚苯胺/结晶TiO2的异质结结构可催化分解H2O2产生活性种和Pickering乳液催化体系的协同作用。本项目将为负载型聚苯胺稳定的Pickering乳液烯烃催化氧化机理的研究提供理论基础。