双功能GO基催化剂的可控设计及其Pickering界面催化苯羟基化的性能研究

Production of phenol by direct hydroxylation of benzene with hydrogen peroxide (H2O2) as oxidant is considered as an alternative green process. However, low selectivity of phenol and ineffective usage of H2O2 are still the main hinders for its industrial application. Design highly reactive catalyst with multifunctional purpose, is the key to resolving above problems. This proposal mainly focuses on the design and preparation of Pickering emulsions with high performance on interfacial catalysis, and make controllable functionalization on GO based materials according to the reaction conditions. The related investigation includes as follows: (1) Through the design and construction of amphipathic properties of GO based materials by covalent modification with hydrophilic molecular, exploring controllable preparation of Pickering emulsion (oil in water as the type of emulsion) with stable catalysis properties, and obtaining bifunctional “microreactor” based on above GO based materials with high reactivity in the reaction of direct hydroxylation of benzene. (2) Through investigating the intrinsic relations between the surface structure of GO based material and interfacial catalysis performance on the biphase of benzene and H2O2 aqueous,searching for the influence between hydrophilic and hydrophobic properties of GO based material and the adsorption and diffusion behavior of the reactants and products on GO surface, and deducing the reactive center and related reaction mechanism, and thus providing new insight into the relationship between the structure of GO based catalyst and phenol selectivity.

以过氧化氢（H2O2）为氧化剂，苯直接羟基化生成苯酚具有过程绿色的特点，然而该体系存在产物选择性及H2O2利用率较低的难题。多功能、高效催化剂的设计制备是解决上述问题的关键。本项目拟利用氧化石墨烯（GO）材料表面特有的“两亲性”，制备具有高效界面催化活性的Pickering乳液体系，并根据反应需要对GO材料进行可控功能化。项目的重点在于：（1）通过对GO材料表面进行亲疏水性的共价键调变，可控制备性能稳定的水包油（O/W）型Pickering乳液，获得具有高选择性催化苯羟基化的GO基双功能“微反应器”；（2）研究GO基材料表面结构与界面催化“苯/ H2O2水溶液”两相体系的内在关系，以及GO基材料的亲疏水性对反应物和产物的在催化剂表面的吸附、扩散行为的影响规律，分析反应中的活性中心及相关反应机理，揭示GO基催化剂的表面结构与苯酚选择性的构效关系，为高性能GO基催化剂的设计制备提供理论依据。

苯酚是重要的有机化工原料，其工业化生产主要采用步骤多且污染大的异丙苯法。以过氧化氢（H2O2）为氧化剂，苯直接羟基化生成苯酚具有过程绿色的特点，然而该体系存在产物选择性及H2O2利用率较低的难题。同时，由于反应物苯和H2O2水溶液互不相溶，通常需要向反应体系中加入毒性较大的乙腈溶剂。因而，如何避免有机溶剂的使用，是本反应实现绿色化要解决的另一问题。多功能、高效催化剂体系的设计制备是解决上述问题的关键。本项目针对上述问题，通过利用氧化石墨烯（GO）材料表面特有的“两亲性”，不加入有机溶剂和表面活性剂，制备出具有界面催化活性的Pickering乳液催化体系，并根据反应需要对GO材料表面进行还原及掺杂改性，同时针对非负载型GO基Pickering乳液催化体系存在催化活性较低且高温易破乳的问题，在其表面负载了钒、铁、锰等非贵金属氧化物，并尝试光辅助GO基Pickering乳液催化苯羟基化反应，主要取得了如下结果：（1）通过研究活性碳材料表面含氧官能团数量及种类对羟胺催化氧化体系的影响，为GO基材料表面的“双功能”调变打下基础；（2）通过化学氧化、还原法，制备并调变了GO材料及其表面的亲疏水性，发明了一种电化学法制备还原态GO的简易方法；（3）经优化制备了室温下性能稳定的水包油（O/W）型GO基Pickering乳液（油水体积比为0.8，GO浓度大于等于6mg/ml）。受此启发的两个关于有机硅乳液制备的发明已获授权；（4）经水热法制备的FeOx/rGO催化剂，通过加入GO制得具有催化苯羟基化的双功能Pickering乳液催化体系，该“微反应器”在无搅拌无有机溶剂的条件下，室温反应可获得约为6.0%的苯酚收率。以上结果将为推动苯直接羟基化制苯酚的技术进步做出贡献。共发表期刊论文3篇，申请发明专利3篇。