沸石成型催化剂内多级孔道结构与传质-反应过程的离散建模及优化研究

Understanding multiscale mass transfer and its influence on catalytic performance of the catalyst pellets formed by hierarchical zeolite powders, as well as optimizing the complex hierarchical pore structure in these catalyst pellets, are the key studies in the industrial application of such hierarchical zeolite catalysts, because these studies not only are able to guide the rational design of hierarchical zeolite catalysts, but also are helpful to predict the relationship between catalytic performance and reaction conditions. In this proposal, an important reaction in the industry, alkylation of benzene with ethene, is taken as a model reaction, and the catalyst pellets formed by hierarchical ZSM-5 zeolite powders are regarded as model catalysts. Combing the discrete modeling approach with the experimental methods and technologies, including controlled synthesis of zeolites, material characterization, reaction kinetics, as well as adsorption equilibrium and kinetics, a discrete model describing multiscale mass transfer and reaction in the catalyst pellet is built and validated. With this discrete model, the complex structure-function relation between hierarchical pore structure and catalytic performance of the catalyst pellet is analyzed and quantified, and then the hierarchical pore structure is optimized to largely enhance the overall performance of the catalyst. This project can provide theoretical guidance, new modeling tool, and innovative optimization method for the research and development of hierarchical zeolite catalysts with high performance for industrial use, also gives an effective approach that the catalyst performance can be enhanced by optimally designing pore structure to the development of other porous catalysts.

理解多级孔道沸石催化剂成型颗粒内多尺度结构上的传质过程及其对催化反应性能的影响规律，优化其中复杂的多级孔道结构，既能用于指导多级孔道沸石催化剂的理性设计，又有助于预测催化性能对反应条件的依赖关系，是多级孔道沸石催化剂工业应用中的关键研究。本项目拟以具有重要工业意义的苯和乙烯烷基化为模型反应，以多级孔道ZSM-5沸石成型颗粒为模型催化剂，采用离散建模方法结合沸石可控制备方法、多种现代表征技术、反应动力学实验以及吸附平衡和吸附动力学实验，建立并验证沸石成型颗粒内多个尺度上传质-反应过程的离散模型，解析并量化多级孔道结构与催化性能之间复杂的结构性能关系，优化设计多级孔道结构以大幅度提升催化剂性能。这一研究将为高性能多级孔道沸石催化剂的工业开发提供理论指导，以及新的模型工具和优化方法，也可为其他多孔催化剂的开发提供一条通过优化设计孔道结构提升催化性能的有效途径。

工业成型催化剂中往往存在很强的扩散限制，致使催化剂性能大幅度降低。本项目针对成型催化剂，特别是多级孔道沸石成型催化剂，建立描述成型催化剂内传质-反应过程的数学模型，应用该模型认识多尺度结构与催化剂性能之间的构-效关系，最后设计优化成型催化剂的孔道和表界面结构以大幅度提升催化剂的性能。取得的重要进展和结果如下：. （1）建立了工业成型催化剂的连续数学模型，利用该模型认识了成型催化剂内多尺度传质-反应过程，发现介孔/大孔中的扩散阻力很多时候和微孔中的扩散阻力同等重要；. （2）建立了工业成型催化剂的离散数学模型，利用该模型研究了堵孔对催化剂性能的影响，发现焦炭/液体堵孔的影响十分重要，而目前的研究很少关注该现象；. （3）设计优化了典型工业反应体系中成型催化剂的孔道和表界面结构，在实验中制备了能大幅度消除孔道和表界面传质阻力的沸石催化材料。. 本项目共发表SCI收录论文9篇，申请中国发明专利2件，培养研究生6人。本项目可以为工业成型催化剂的开发提供一些数学模型工具和理论指导。