高效双活性中心钌催化剂的设计制备及其温和条件下氨合成性能研究

The current industrial ammonia synthesis is one of the most energy consuming process in the chemical industry. The most effective way to decrease energy consumption is to develop a high efficiency catalyst and then synthesis ammonia under mild condition. The current industrial catalysts show low ammonia synthesis activities at low temperature and low pressure because the catalytic peformances are inhibited by the the scaling relation between the activation barrier for the dissociation and the bonding energy of all the intermediates. In this project, C/Ru/CeO2 composite catalyst, which contains two distinct metal–support interfaces, would be prepared using ruthenium as the active metal. Then two active sites (CeO2-Ru site and Ru-C sites) would be created because the differences in the interfaces for the composite catalyst. These sites can play a part in the different processes during ammonia synthesis, such as the dissociation of hydrogen and nitrogen, the formation and desorption of ammonia synthesis, etc. Consequently, the scaling relations among the adsorption and transition-state energies of intermediates may be broken. The critical factors for the preparation of C/Ru/CeO2 composite catalyst would be studied. The relationships among the composition, structure and catalytic performance would be investigated. The mechanism of promoters also would be discussed. Then an efficient catalyst, which could be used in ammonia synthesis under mild condition, would be prepared. The obtained results not only can provide valuable guildines for the preparation of an efficient catalyst with double active sites, but also are significant in energy saving in industrial ammonia synthesis process.

合成氨工业是最耗能的化工过程之一，开发出高性能催化剂并实现在温和条件下合成氨是降低其能耗最有效途径。现有工业催化剂受制于氨合成中反应能垒与反应物种吸附能之间的限制关系，难以实现在温和条件下高效合成氨。本项目拟以钌金属为活性组分，利用不同界面上活性位的性质差异，在Ru金属上创建出两种不同活性位（CeO2-Ru活性位和Ru-C活性位），以满足N2和H2的活化、反应产物的生成与脱附等不同需求，打破反应能垒与吸附能之间的限制关系，从而制备出具有两种不同金属-载体界面的双活性中心C/Ru/CeO2复合催化剂。将深入研究其制备过程的关键因素和调控规律，揭示催化剂组成-结构-性能间的构效关系和助剂促进催化剂性能的作用机制，最终开发出适用于温和条件合成氨的高性能催化剂。这不仅对发展“双活性中心”催化剂的制备方法提供思路和理论指导，而且对合成氨工业的节能降耗具有重要的实际意义。