反应过程银催化剂表界面动态结构的原位研究

Silver is a widely-used industrial catalyst for the ethylene epoxidation. In a reaction, driven by temperature or pressure, the atoms of silver are moving on the surface, which were observed recently by the newly-developed tools. However, it is unclear how this dynamic surface influences the performance of catalysts. In this project we proposed to use the newly-developed electron microscopes (in situ TEM and SEM) to directly track the change of surface structure of silver catalysts in a reaction and to reveal the relationship between the dynamic structures and the performance of catalysts. Firstly, The law dominating the dynamic structures will be analyzed and the mechanism will be discovered. By coupling the mass spectrometer with the in situ reactor of electron microscopes, the component of flux after the reaction will be quantified. The relationship between the dynamic structure of catalysts with the reaction efficiency and selectivity will be disclosed. Based on these findings, an ideal model of structured catalyst will be proposed for ethylene epoxidation. The ideal model will be evaluated by in situ experiments and computer simulation. Catalysts with different structures are synthesized and loaded into supports. The influence of these structures on the selectivity and efficiency will be evaluated in a microreactors. The optimal structure of silver catalyst for the ethylene epoxidation will be identified. This study would help to build up the relationship between the dynamic structures and the property of catalysts and provide a guidance to develop highly efficient silver catalysts.

在反应过程中，受温度和压力影响，催化剂表面原子会发生运动迁移，晶面重整等，这些动态结构对反应路径和效率的影响是一个未知的问题。人们通常采用反应前的静态结构与反应过程中的性能进行关联，构建时空尺度错位的催化剂构效关系，为催化剂开发和反应过程研究带来很多不确定性。在本项目中，拟采用近年来开发的原位电镜技术，在乙烯环氧化反应条件下，原位记录银催化剂表面结构的动态变化过程，总结其变化规律，分析其控制机制；通过在反应过程中量化反应产物，揭示催化剂结构的动态变化对反应过程的影响规律，提出基于动态结构的理想催化剂模型，通过原位电镜实验和计算机模拟技术，验证催化剂模型。利用微型反应器研究不同结构的银颗粒对乙烯环氧化反应选择性及活性的影响，提出基于动态结构的催化剂新型构效关系，为高效负载型催化剂的开发和研制提供理论指导。

本项目以材料表界面动态结构调控与应用为研究主线，发现了反应和传递对银颗粒形貌的调控规律，采用原位电镜等技术揭示了界面浓度场对银催化剂结构的调控机制，探索了界面浓度场和表面能对颗粒稳态生长过程的影响，建立了不同形貌银催化剂可控规模化制备方法，与中石化燕山分院合作开发高选择性银催化剂。将电解水工艺与乙烯环氧化工艺结合，发展了乙烯环氧化的原位电催化新工艺，获得了环氧乙烷和乙二醇等产物，初步证实了该工艺的可行性。进一步将表界面反应-传递研究拓展到其它反应体系，建立双氧水直接合成电化学工艺，发展了外场强化传质的锂负极保护策略。研究工作获得2019年中国化工学会科学技术奖“基础研究成果奖一等奖”，项目主持人获得2019年日本化学工学会“亚洲杰出科研工作者和工程师奖”和2021年，第八届侯德榜化工科学技术奖“创新奖”等。在国内外期刊发表文章18篇，其中SCI收录15篇。申请发明专利4项。培养博士生3名，硕士生7名。