CO2膨胀的溶胶－凝胶过程构筑催化剂或载体的孔结构及其应用

催化剂或其载体的孔结构对催化剂的活性和反应的选择性有显著影响，构筑特定孔结构的材料在化工、能源等工业中具有关键意义。本项目针对常用催化剂载体或催化剂，如SiO2和Al2O3等，提出高压/超临界CO2膨胀的溶胶－凝胶新过程，使得凝胶粒子和孔结构发生变化，从而调节、获取具有特定孔结构，特别是双介孔分布结构的催化剂或催化剂载体。为此，本项目建立高压CO2膨胀的溶胶－凝胶－超临界干燥过程装置，系统探讨温度、压力、前驱体浓度、pH值、模板剂(量和种类)等对材料的孔径、孔容和比表面积等的影响；实验和理论研究体系的膨胀行为，结合膨胀行为探讨介孔形成的机理；应用超临界流体负载方法制备合适催化剂，研究不同孔结构催化剂对包括乙烯聚合等催化反应效果的影响。通过该项目的实施，希望展示一种绿色、非常规的溶胶－凝胶体系，为多孔材料特别是双/多介孔催化剂的构筑提供新思路和新平台。因此，开展本项目研究具有理论和应用价值。

The pore structure of catalysts/catalyst carrers including pore volume, pore size, and specific surface area properties has prominent effect on the catalytic activity and product selectivity in typical catalytic reactions. Construction of materials with specical hierarchical pores therefore plays a key role on the chemical, energy and other industries. This project, for some common mesoporous materials such as SiO2 and Al2O3, proposes a new system, namely, high-pressure /supercritical CO2-expanded sol-gel system, for adjusting the pore structure of materials, particularly, preparing bimodal mesoporous materials for catalysts and catalyst carriers because the expansion can rearrange the particles of the gel. On line with this, the main content of the projcet will include the establishment of a sol-gel-supercritical drying apparatus for systematic study of the effect of the temperature, pressure, concentration of precursors, pH value and the amount and type of the templates used on the final mesoporous materials. The project will theoretically and experimentally investigate the volume expansion thermodynamic behavior of the CO2-expanded systems, and the pore formation mechanism. Finally, the project will also focus on the application of the prepared catalysts, including the supercritical fluid loading of catalyst components into the as-prepared mesoporous silica to form Philip Cr catalyst for ethylene polymerization and the evaluation of the catalysts. From the implementation of the project, hope to highlight the difference between this new and green sol-gel process and the conventional sol-gel process to provide a new platform of preparing mesoporous materials, particularly, the bimodal/mutimodal mesoporous materials for high quality catalysts and other applications. Therefore, this project is of significant in both theorectical study and practical application.