模板剂-异晶协同导向法合成高水热稳定性Al-IWR分子筛及其烷基化催化性能研究

Zeolites are widely used in catalysis, ion exchange, gas adsorption and separation. Organic templates and solid seeds are often used to direct the forming of zeolite frameworks. However, the relationship and/or interaction between templates and seeds, especially the heterogeneous seeds in the preparation of zeolites has attracted little attention. IWR-type zeolite has an interconnected 12×10×10-membered-ring three-dimensional channel system, which is believed to benefit the diffusion of substrate and product molecules in industrial catalysis processes, such as alkylation of aromatics. However, the practical application of IWR zeolites is retarded by the low framework hydrothermal stability, arising from the high reactivity of germanium and the easy hydrolysis of Ge-O bonds towards water or even moisture. In this proposal, we disclose a synergistic structure-directing effect between template and heterogeneous seeds in the synthesis of zeolites for the first time. By applying the so-called synergistic directing route, hydrothermally stable Al-IWR zeolites can be facilely obtained. Firstly, the effects of templates and aluminosilicate zeolites, which serve as heterogeneous seeds, on the zeolite products will be investigated by using the high throughput synthesis techniques. IWR zeolites with improved hydrothermal stability would be successfully produced, thus verifying the synergistic structure-directing action. Then the crystallization process will be investigated by characterizing a series of solid products obtained after crystallization of IWR zeolite for different periods with multiple techniques, purpose of which is to figure out the phase transformation process and the evolution of zeolitic building units. Computer simulations will also be applied to study the relationship between zeolite framework host and template guest molecules and carry out the non-bonding interaction energy calculation. By combining the detection of the crystallization process and the molecular simulation results, a mechanism of the synergistic interaction between template and heterogeneous seeds will be proposed. Finally the catalytic performance of IWR zeolites will be tested in the alkylation of aromatics with alcohols and olefins. A correlation between the catalytic performance and the porosity structure of zeolite framework will thus be established. The research on the synergistic effect between template and heterogeneous seeds herein would provide deep insight into the structure-directing effects in zeolite synthesis and mechanistic pathways in zeolite crystallization. This newly established synergistic directing route is expected to offer rational guidelines for the preparation of zeolite and shed light on the discovery of novel zeolites.

分子筛在吸附分离、离子交换和催化等领域有着广泛应用。作为两类具有结构导向功能的物质，模板剂和晶种，特别是异晶在分子筛制备中的相互作用很少受到关注。IWR分子筛独特的三维12×10×10元环孔道结构有利于催化反应中分子的扩散，然而低水热稳定性限制了其应用前景。本项目使用模板剂-异晶协同导向法制备高水热稳定性Al-IWR分子筛并研究其烷基化催化性能。首先，通过高通量合成技术筛选模板剂和作异晶的硅铝分子筛，制备IWR分子筛并提升其水热稳定性，证明两种导向剂的协同作用。然后，对晶化过程进行监测，找出分子筛物相及结构单元的演变规律，结合计算机模拟技术，提出模板剂与异晶的协同导向机制。最后，将Al-IWR分子筛用于芳烃烷基化反应中，探寻催化性能与孔道结构之间的关联。本项目的研究对于深入认识分子筛的结构导向机制和揭示晶化规律有重要意义，可为分子筛的制备提供理论指导，也为新结构分子筛的开发提供了新的思路。

分子筛新材料的创制和晶化机理的认识一直是分子筛研究领域的热点。本项目围绕分子筛合成中模板剂-异晶间的相互作用开展研究，并在此基础上作了一定的扩展和延伸。（1）利用模板剂和异晶间的协同导向作用，制备了具有高水热稳定性的Al-IWR分子筛，提出了模板剂和异晶分别导向生成部分结构单元、经重组生成目标分子筛的晶化机理；（2）通过改变异晶的加入量，实现了Al-IWR分子筛铝含量、酸性和孔结构的调控，Al-IWR分子筛在苯液相烷基化反应表现出应用潜能；（3）创制了一种新结构分子筛SCM-25，结构解析发现其具有尺寸可达29.9 Å的有序介孔超笼，有望用于大分子选择性催化转化；（4）使用非季铵型吡咯烷衍生物为模板剂制备了具有高水热稳定性的ITH分子筛，有效降低了合成成本。.本项目的研究揭示了模板剂和异晶协同导向的机制，丰富了分子筛催化材料设计合成的理论和方法，得到了数种具有应用潜能的分子筛新材料，有望推动工业催化的新发展。