双活性位Pd/小孔分子筛消除柴油车NOx和Soot的双功能机理及协同效应

柴油车国VI标准的实施和高效发动机尾气温度的下降，使其两大主要污染物NOx和Soot面临低温净化的挑战。本项目在研究被动NOx吸附剂（PNA）解决低温NOx排放的基础上，提出将Pd/小孔分子筛PNA负载到颗粒物过滤器（DPF）上，同时催化Soot燃烧，即“PNA on Filter”新技术，一体化消除冷启动NOx和Soot。本项目将在SSZ-13等小孔分子筛上构建含量最大化的孤立Pd离子和高分散的PdOx两种活性物种，采用实时、原位和瞬态实验，动力学测试和DFT计算等研究被动NOx吸/脱附和催化Soot燃烧的活性位和机理，以及反应条件下两种Pd物种的存在状态及相互转化规律，揭示双活性位Pd/小孔分子筛的双功能协同效应，满足消除柴油车NOx和Soot对低温活性提高的共性需求。该技术将为日益严格排放法规的实施和更高效发动机的推广应用铺平道路，也是国家实施打赢雾霾攻坚战行动计划的强力技术支撑。

The implementation of the China VI standard and the lower exhaust temperature for highly efficient engines in the future for diesel vehicles make the purification of nitrogen oxides (NOx) and soot particulates, two major pollutants of diesel exhausts, face new challenges. Based on passive NOx adsorbers (PNA) to control NOx emission at low temperature, this project proposes a novel technology “PNA on Filter”, i.e., loading Pd/small-pore zeolite PNA onto diesel particulate filter (DPF), where soot is catalytically combusted simultaneously, to remove NOx and soot integrally during cold start. In this project, two kinds of active Pd species on small-pore zeolites (for instance, SSZ-13), isolated Pd ions with maximum contents and highly dispersed PdOx, will be constructed. The active sites and mechanisms of NOx adsorption/desorption and catalytic soot combustion, as well as the existence state and mutual conversion rule of the dual Pd species under reaction conditions, will be investigated by means of real-time, in situ and operando experiments, transition state techniques, kinetic measurement and DFT theoretical calculation, in order to reveal the synergism of dual functions for Pd/small-pore zeolites with dual active sites, thus addressing the common needs of removal of NOx and soot from diesel vehicles for the improvement of activity at low temperatures. This will pave the way for the implementation of increasingly stringent emission regulations and the extensive application of highly efficient engines and will be a strongly technical support for the national action plan to win the battle against haze.