多孔沸石的合成、成型及孔结构与机械强度的研究

Hierarchical porous zeolites are materials obtained by introducing mesopores into conventional microporous zeolites, and they are widely used in the catalytic conversions of large molecules. In the past, a larger number of studies of hierarchical porous zeolites were carried out, and thus their synthetic methods have been basically perfected. However, in industry hierarchical porous zeolites in pellet form are required. The pore structure of the shaped zeolite pellets is different from that of powdered zeolite, and a sufficiently high mechanical strength is also required for the shaped zeolite pellets. Therefore, this project will focus on the synthesis and shaping of hierarchical porous zeolites, as well as the pore structure and mechanical strength of the shaped zeolite pellets. Experimental examination and theoretical analysis are used to systematically study the low-cost, clean synthesis of hierarchical porous zeolites, to study the shaping of hierarchical porous zeolites, to clarify the relationship between the pellet strength and the pellet density, pore structure, and the relationship between the pellet strength and the synthesis, shaping of hierarchical porous zeolites, to explain the damaging effect of shaping on the mesopore structure, to develop a shaping theory of hierarchical porous zeolites, and to propose a related optimum approach to improve the zeolite pellet properties during their preparation process. This project is different from the conventional studies of hierarchical porous zeolites, and is also different from the studies of catalytic chemistry. It will aim to the catalyst mechanics, and its theoretical innovation is to gain a scientific understanding of the pore structure and mechanical strength of the shaped zeolite pellets, which can offer the theoretical basis for the commercial production and application of hierarchical porous zeolites.

多级孔沸石是在传统微孔沸石晶体中引入介孔而成的多级孔道沸石材料，在大分子催化转化方面有着广泛应用。随着多级孔沸石研究的不断推进，其合成方法已基本成熟。然而，工业应用需要多级孔沸石成型体，其孔结构不同于粉体，而且力学性能极其重要。因此，本项目提出多级孔沸石合成、成型、孔结构、机械强度等工程基础问题研究。采用实验和理论分析相结合的方法，研究多级孔沸石的低成本清洁合成过程，研究多级孔沸石粉体的成型过程，阐明成型体机械强度与颗粒密度、孔结构等之间的关系以及与多级孔沸石合成、成型过程之间的关系，揭示成型对介孔结构的微观破环作用，建立多级孔沸石的成型理论，提出多级孔沸石成型体的优化制备方案等。本项目不同于传统多级孔沸石研究，也不同于催化化学研究，具有鲜明特色。本项目主体内容属于催化剂力学问题，其成果理论创新主要表现在对多级孔沸石成型体的孔结构与机械强度等形成科学认识，以便为多级孔沸石的工业生产及应用提供理论依据。

对于粉末催化材料，成型是其实现工业应用的重要步骤之一。本项目针对这一问题，开展了实验与理论研究，获得了基础性认识。.在多级孔沸石合成的基础上，研究了多级孔沸石的挤条等成型过程。结合实验与表征结果，理论分析了多级孔沸石的成型机理。结果表明，多级孔沸石成型体具有脆性材料的典型特性，其机械强度数据的离散性质能够很好地服从Weibull统计分布。多级孔沸石成型体的微孔主要来源于沸石晶粒本身，而介孔更多地由颗粒堆积而产生。此外，研究还表明，通过优化成型工艺条件，在保持孔结构等性质不变的前提下提高多级孔沸石成型体的机械性能是完全可行的，这对于多级孔沸石实现工业应用具有重要意义。.研究了粘结剂种类、粘结剂含量、胶溶剂含量和挤条转速等成型工艺条件对多级孔ZSM-5沸石成型体催化剂的影响。结果表明，拟薄水铝石作为成型粘结剂，既能保证成型体催化剂继承ZSM-5沸石的优良孔道结构，而且能够获得可靠的机械性能；当33 wt%拟薄水铝石含量、13 wt%硝酸含量、50 r/min挤条转速时，ZSM-5沸石成型体表现为最佳机械性能。此外，还研究了干燥和焙烧等热处理过程对多级孔ZSM-5沸石成型体催化剂机械性能的影响，并利用响应面方法论建立了干燥和焙烧过程中的数学模型，探讨了过程影响机理，解释了机械性能提高的原因，并根据数学模型提出优化方案。.项目研究成果主要表现在多级孔沸石成型过程和成型体机械性能方面的理论创新，在一定程度上为多级孔沸石成型体催化剂的设计和生产提供了理论依据，为多级孔沸石成型体催化剂工业应用操作参数的优化提供了可靠指导。项目执行期间，课题组已在AIChE Journal、Industrial & Engineering Chemistry Research、Chemical Engineering Journal、Journal of Catalysis等期刊上发表SCI收录论文25篇，申请国家发明专利7件，授权国家发明专利3件，培养博士研究生2名和硕士研究生5名，圆满完成了原定研究内容以及各项任务指标等。