温和条件萘直接羟基化制备萘酚介孔分子筛催化剂的研究

The coal reserves of China is the largest in the world, and naphthalene is one of the main products in coal chemical industry. The hydroxylation products of naphthalene, 1-naphthol and 2-naphthol, are both important chemical products and intermediates. But there are many shortcomings such as complex process, environmental pollution and so on in the industrial production of naphthol. Thus the direct hydroxylation of naphthalene to naphthol has a very important research value...Hydrogen peroxide is considered the most promising oxidant because the process is simple, green, and economic. The key in the direct hydroxylation of naphthalene to naphthol with hydrogen peroxide is the development of catalysts.Because of the larger size of naphthalene molecules, traditional microporous molecular sieves can not be used as a catalyst carrier in this reaction. Increasing attention has been paid to mesoporous molecular sieves, mainly due to their regularly ordered pore arrangements, very narrow and adjustable pore-size distributions in the range of 2-10 nm or larger, high surface areas and relatively high thermal stabilities, which could be widely used in the field of catalysis, sorption and separation. Some heteroatoms such as iron, vanadium, titanium, cobalt and copper doped into mesoporous molecular sieves showed good catalytic performance in oxidation of the aromatic, but poor hydrothermal stability of mesoporous materials limits their industrial applications. The reaction under mild conditions can improve the catalyst life, energy conservation, production safety and especially enhance the catalyst performance...This project is planned to devolop mesoporous catalysts with high activity in the hydroxylation of naphthalene to naphthol with hydrogen peroxide as oxidant under mild conditions by means of the research on the composition, structure, pore size, surface properties and morphology of different mesoporous molecular sieve. The relationship of these properties with catalytic performance will also be explored, and finally we will establish a basis for industrial applications.

萘是煤化工主要产品之一，其羟基化产物1-萘酚及2-萘酚是重要的化工产品及中间体。目前萘酚工业生产存在工艺复杂、三废多和环境污染等缺点。萘过氧化氢直接羟基化制备萘酚可以克服这些缺点，且原子经济性高。由于萘的分子直径较大，传统微孔分子筛不能作为其羟基化反应催化剂载体。介孔分子筛具有规则的孔道结构、较大的孔径、极高的比表面积，其在催化领域具有良好的应用前景。多种杂原子掺杂介孔分子筛在芳烃选择氧化反应中表现出良好的催化性能，但介孔材料水热稳定性差限制了其工业应用。温和条件反应不仅能够提高催化剂使用寿命，同时节能减排，生产安全性高，关键在于提高催化剂性能。本项目拟通过对不同介孔分子筛组成、结构、孔径、表面性质及形貌的调控研究，开发温和条件下在萘过氧化氢羟基化制备萘酚反应中性能优异的催化剂，同时探求组成、结构、形貌与其催化性能之间关系的一般规律，为其工业应用建立基础。

萘选择氧化产物如α-萘酚广泛应用于医药、农药、染料、香料制造、手性催化剂合成等方面。传统合成方法需多步反应，选择性较差，污染物排放多。寻求价格低廉、性能优良、条件温和的新催化剂并探求高效、无污染的萘羟基化新工艺具有重要的研究价值。多相催化剂研究关键在于：1）活性位及载体种类筛选、载体性质影响、活性位位置及二者之间相互作用研究；2）合成具有不同孔径、形貌载体，将活性位固载于载体不同位置；3）催化反应条件、反应动力学、催化剂稳定性研究等。本项目对于萘羟基化反应就以上内容展开研究。.主要成果有：.1）分析方法：针对萘氧化反应体系建立了以邻苯二甲醚为内标、气相色谱分析产物的方法，各组分分析相关系数均达到0.99以上；.2）载体及活性位筛选：考虑萘分子直径较大，本项目选择以介孔分子筛为载体。活性位研究表明钒、铁、锰作为活性中心具有较好的催化性能：钒作为活性位转化率达到32.2 %，选择性最高75.83 %；.3）活性位调控研究：通过理论分析设计并通过一步自组装将催化活性位负载于不同介孔分子筛不同位置，如过渡金属氧化物单层分散到介孔孔道中；活性位固载于介孔表面等，表面活性位数量的增加能够提升催化性能；.4）载体影响研究：调控不同类型介孔分子筛形貌、尺度并研究对催化性能影响，成功合成出不同过渡金属修饰并作为活性位的管、球状纳米反应器，同时对其合成机理进行分析研究，提高了催化剂性能；.5）催化剂稳定性研究：采用活性位嵌入分子筛骨架、载体表面锚定等方法提高稳定性，例如通过卟啉锰金属配合物与表面氨功能化的MCM-41作用将锰固定于载体表面，催化研究表明萘转化率>30%、萘酚选择性>75%，催化剂重复使用5次以上性能下降较少；.6）光催化氧化研究：光催化具有环保、节能、低成本等突出特点。项目通过形貌、性质调变并以不同元素修饰后得到具有可见光响应的蓝色、灰色及黑色二氧化钛。光催化氧化苯制苯酚反应结果表明苯转化率最高可达72.3%，苯酚选择性最高为85.1%。