新型功能化离子液体的设计及其对合成碳酸二苯酯的催化性能研究

The transesterification of dimethyl carbonate and phenol to synthesize diphenyl carbonate (DPC) is considered to be a clean route. This route is a two-step process consisting of the first-step transesterification reaction and the second-step disproportionation reaction of methyl phenyl carbonate (MPC). The disproportionation of MPC is a key step to produce DPC in this route, and it is found that the reaction can not process thoroughly for the most part, greatly restricting the generation of target product DPC. Thus, the intensive study on the disproportionation of MPC is very important. Ionic liquids (ILs) show good catalytic activities in the transesterification reaction, but currently the problems of separation between the product and catalysts need to be urgently solved. Moreover, the catalysts have not been reported yet to catalyze MPC disproportionation reaction. This work will design and synthesize series of novel functionalized Lewis acid triazolium based ILs, and then they are immobilized on SBA-15 as heterogeneous catalysts, which are used to catalyze the disproportionation reaction of MPC. The novel catalysts will not only greatly decrease the amount of ILs, but also avoid the loss of ILs and have the advantages of easy separation, recovery and recyclability. The relationship between the structural property and catalytic performance of the catalysts will be systematically studied, and the reaction mechanism is also investigated. This work will provide a new research idea for realizing the green and efficient synthesis of DPC.

碳酸二甲酯与苯酚酯交换是合成碳酸二苯酯（DPC）的一条清洁路线，该路线分为酯交换和歧化两个反应步骤，其中第二步甲基苯基碳酸酯（MPC）歧化反应作为该路线合成DPC的关键步骤，研究发现大都不能进行彻底，极大地制约了目标产物DPC的生成。因此，对其进行深入研究非常重要。离子液体催化剂在酯交换反应中显示较好的催化活性，但与产物分离困难的问题目前亟需解决，而且催化第二步MPC歧化反应的研究尚未报道。本课题拟设计合成系列不同类型的功能化Lewis酸唑类离子液体，并将这些离子液体通过化学键嫁接固载到SBA-15，发挥均相催化剂多相化的优势，用于催化歧化反应。该类新型催化剂不仅能大大减少离子液体的用量，而且可以避免离子液体的流失，还具有易分离回收和循环利用的优点。本项目将系统研究催化剂结构与催化性能的构效关系，阐明反应机理，为实现DPC的绿色高效合成提供新的思路。

碳酸二苯酯（DPC）是一种重要的环保有机碳酸酯，广泛应用于医药、农药和高分子材料等领域，特别是合成工程塑料聚碳酸酯（PC）的主要原料。本项目围绕DPC的绿色高效合成开展深入研究，合成了系列羟基、羧基、氨基等不同活性基团功能化的咪唑基离子液体催化剂，并将这些离子液体杂化嫁接固载到SBA-15，用于催化MPC歧化反应合成DPC，显示较高的催化活性、容易分离和较优越的稳定性，不仅能大大减少离子液体的用量，而且可以避免离子液体的流失。离子液体的结构特点对催化性能影响很大，羟基功能化的SBA-15-IL-OH显示较好的催化性能，且具有较大的TOF值，明显高于文献报道的多相催化剂；同时发现不同烷基链长度的离子液体和不同阴离子结构的离子液体也显著影响催化性能，增加链长其活性明显降低，Br-阴离子功能化的离子液体具有较好的催化性能，并通过原位红外表征技术和DFT理论计算阐明催化作用机理。另外，针对目前市场上没有高纯度的原料MPC出售，增加探究了新型Pb-Mg薄纳米片、Pb-Bi/SBA-15催化剂用于合成MPC的研究内容，结果显示催化剂具有较高的产物选择性，易于从反应体系中分离回收，具有较好的重复使用性能，可分离提纯得到高纯度的MPC，解决了对第二步MPC歧化反应研究所需的原料问题。