多级孔磷酸硅铝分子筛的高效合成及催化应用研究

In the field of the synthesis and catalytic application of hierarchically porous aluminophosphate molecular sieves, their complex preparative procedure and high cost are the main bottlenecks that restrict the practical applications of hierarchically porous aluminophosphate molecular sieves. Nontemplated method is one of the feasible routes to overcome these limitations. Here we propose to take microwave synthesis, solventless synthesis, seed-assisted synthesis and mechanochemistry pretreatment as the tools for the green and highly efficient synthesis of three types of hierarchically porous silicoaluminophosphate molecular sieves catalysts (i.e. SAPO-5 nanosheets, hierarchically porous SAPO-11 and SAPO-34). The essential data on the design and preparation of hierarchically porous molecular sieves with high silicon contents can be obtained by studying the relationships between the properties of seeds and the textural parameters of molecular sieves, and that of the mechanochemistry pretreatment and the properties of silicon species. The properties of acid centers and pore structure of materials obtained will be fully characterized by several advanced technologies. The catalytic properties of above three types of catalysts prepared by different methods will be evaluated using alkylation, isomerization and methanol-to-hydrocarbons conversion as probe reactions. The relationships of the nanosheet thickness to catalytic selectivity and the mesopore structure to catalyst lifetime can be thoroughly explored based on catalytic results. The implementation of the proposed project can provide a fundamental understanding on design and synthesis of high-performance catalysts.

在多级孔磷酸铝分子筛的合成和催化应用领域，复杂的制备步骤和高昂的合成成本是限制其走向实际应用的主要瓶颈，而无模板法是解决该问题的可行的途径之一。本项目拟以磷酸硅铝分子筛为研究对象，以微波合成、无溶剂合成、晶种协助的合成及机械化学预处理为工具，开展三类多级孔磷酸硅铝分子筛催化材料，即SAPO-5分子筛纳米层、多级孔Pt/SAPO-11和SAPO-34分子筛的绿色高效合成。通过详细研究合成过程中晶种性质与分子筛织构参数间以及机械化学预处理与硅物种性质间的关联，为设计制备高硅取代量的多级孔分子筛提供基础数据。进一步通过各种表征手段研究这些催化材料的酸中心性质和孔结构。在此基础之上，通过比较不同方法合成的多级孔分子筛在烷基化、异构化和甲醇转化制烃反应中的催化性能，确立纳米层的厚度与选择性以及介孔的结构与寿命之间的关系，为设计高活性、高选择性和长寿命的催化材料提供基础数据和理论依据。

繁琐的制备步骤和高昂的成本是限制多级孔磷酸铝分子筛走向实际应用的主要障碍，无模板法是解决该问题的可行的途径之一。本项目主要开展了三类多级孔磷酸硅铝分子筛催化材料，即SAPO-5分子筛纳米层、多级孔SAPO-11和SAPO-34分子筛的绿色高效合成及催化应用方面的研究，并取得了下列成果。.1）通过改变低共熔混合物类型、微波加热功率、晶化温度和时间，考察了其对SAPO-5分子筛纳米层形貌的影响，提出了纳米层可能的生成机制。比较了离子热法和水热法合成的SAPO-5分子筛纳米层催化剂在苯与苯甲醇烷基化反应中的催化性能，发现前者由于具有更大的外表面积和更多的弱酸中心，因而催化性能更优。.2）分别研究了未处理晶种、酸刻蚀晶种和球磨晶种对无溶剂法合成的SAPO-11和SAPO-34分子筛织构参数的影响，提出了多级孔道可能的形成机制。.3）研究了不同晶种条件下、吗啉和二乙胺分别作为结构导向剂无溶剂合成的SAPO-34分子筛催化剂在甲醇制烯烃反应中的催化性能，揭示了这些催化材料的织构性质、酸性与其催化性能之间的关系，为高性能的甲醇制烯烃催化剂的设计指明了研究方向。