理论计算研究NH3-SCR分子筛催化剂中Brønsted酸性位的作用

氨气选择性还原（NH3-SCR）是目前消除柴油机排放NOx的主流技术。金属Cu负载的分子筛催化剂具有优异的NH3-SCR活性和应用前景。分子筛催化剂中的B酸位对NH3-SCR反应有重要影响，但其作用的微观机理尚不明确。本项目拟以Cu/SSZ-13分子筛为基础，采用计算化学方法研究NH3-SCR分子筛催化剂消除NOx过程中微观反应机理，重点考察分子筛B酸位在NH3-SCR反应中的作用。发展同时包含Cu金属位和B酸位的更接近真实反应条件的复杂分子筛计算模型，研究NH3-SCR过程中NO2/NO反应物比例效应、失活物种NH4NO3的形成和转化、考察B酸位与金属Cu位点的作用差异及不同位点之间的协同效应等，为实现合理调控催化剂结构及优化设计反应体系提供理论依据。

The selective catalytic reduction of nitrogen oxides (NOx) by NH3 (NH3–SCR) is a key technology to control NOx emissions from diesel engine. A small-pore Cu-exchanged zeolites with high NH3–SCR activity are promising for this purpose. The presence of Brønsted acid sites in zeolites has an important effect on the NH3-SCR reaction, but their mechanistic role remains unclear. In this project, I will use computational approaches to study the reaction mechanism of NH3–SCR of NOx over Cu-based zeolites with emphasis on the role of Brønsted acid sites (BASs). I will develop computational zeolite models containing both Cu sites and BASs to better represent the catalyst structure under realistic conditions and then investigate the effect of NO2/NO ratio, the formation and decomposition of deactivating NH4NO3 species during NH3-SCR reaction. The reactivity of Cu sites and BAS as well as their synergetic effect will be explored to build the complete reaction network of NH3-SCR. The obtained knowledge will provide fundamental basis for the rational control and design of efficient NH3-SCR systems.