基于小孔分子筛的NH3-SCR催化剂构筑及其抗硫中毒机理研究

The selective catalytic reduction with NH3 (NH3-SCR) is one of the most promising technologies for NOx emission control from automotive exhaust. Cu-SSZ-13 catalysts with chabazite structure (CHA) have attracted much attention due to their high NH3-SCR activity and good hydrothermal stability. However, in actual application, SCR catalysts readily undergo sulfur poisoning. In this study, based on quantum chemical DFT calculations combined with experimental characterization methods, sulfur poisoning can be solved by multipath synergy, such as decreasing the co-adsorption of SO2 and NH3, inhabiting the inversion of SO2 to SO3, increasing the interaction between matal and zeolite. All possible mechanisms of sulfur poisoning are firstly proposed and discussed in order to illustrate micro-dynamic of sulfur poisoning at the electronic level, the structure-activity relationship of the catalysts is revealed. These studies are expected to establish the gas-solid catalytic model of small molecular adsorption, co-adsorption, desorption and dissociation at the surface of catalysts, moreover. Finally, the relationship between the micro-parameters of reaction kinetics and the macro-evaluable properties of catalysts can be obtained to provide the basic theoretical clues for filtration, modification of the Cu-SSZ-13 catalyst and design of the new supported catalysts.

NH3选择性催化还原反应(NH3-SCR)是目前最有效的机动车尾气NOx净化技术之一。具有菱沸石(CHA)结构的Cu-SSZ-13分子筛催化剂在较宽的温度区间表现了更高的活性和水热稳定性，但在实际应用中也存在催化剂硫中毒失活的问题。本项目采用量子化学理论计算和实验表征相结合的方法，通过降低SO2和NH3的共吸附，抑制SO2/SO3的转化，增加金属活性组分与分子筛的相互作用等多路径协同解决分子筛催化剂的硫中毒问题。建立催化剂硫中毒的微观机制，在电子水平上阐明硫中毒问题的微观原因，阐明催化剂的活性组分和含量等主要因素与催化剂抗硫中毒性能的构效关系；阐明反应体系中小分子在催化剂表面上的吸附、共吸附、解离和脱附的微观特性；建立反应微观参量与催化剂宏观可评价性能的关系，为小孔Cu-SSZ-13分子筛催化剂的筛选和改性，以及有针对性地设计新型催化剂，提供基本的理论依据。

CHA分子筛催化剂因其优异的催化活性和水热稳定性，在柴油机尾气脱硝领域得到广泛应用。然而，这类催化剂在催化活性、抗硫中毒等方面还面临巨大挑战，影响其催化性能的电子效应和结构效应目前还不是很清楚。本项目基于密度泛函理论，系统的研究了催化剂的Si/Al比、活性组分等因素对其性质及催化性能的影响，并在此基础上研究了催化剂的抗硫中毒性能。在理论计算的基础上，制备了一系列的催化剂用于NO脱硝性能评价。采用理论与并与实验方法相结合，为实际应用中催化剂的制备提供理论依据。