等离子体协同纳米催化脱除NOx及实现PM低温燃烧的机理研究

The simultaneous reduction of NOx and PM through non-thermal plasma （NTP）assisted catalyst is considered to be one of the most promising technologies in diesel exhaust after-treatment.Compared with conventional catalysts,nano-catalysts（NC） with high specific surface area can increase the contact area between reactants and the catalyst,in order to achieve high NOx and PM reduction.The mechanism research on NOx reduction and PM low-temperature combustion with non-thermal plasma assisted nano-catalytic technology were investigated,and the effect on NOx reduction with NTP energy density,the composition of the nano-catalyst and temperature were analyzed to explore the relation between NTP and low temperature active of catalyst.The chemical mechanism of NOx reaction in the micro-region of nano-catalyst was explored combined with the numerical simulation of NTP treatment by the Chemkin software.By using quantitative descriptive analysis method,the change laws of the particle size distribution,component changes and the microstructure of nano-catalyst were described.Combined with thermogravimetric analysis (TGA),the effects of NTP-NC system on the PM physical and chemical characteristics were analyzed to evaluate the performance of PM low temperature combustion.The reaction model of NOx and PM reduction by NTP-NC system was established to reveal the catalytic mechanism of the NTP-NC system for NOx reduction and the mechanism of PM low temperature combustion, which provides the theoretical basis for simultaneous control of NOx and PM reduction.

等离子体（NTP）协同催化技术具有同时脱除NOx和PM的技术优点，被认为是柴油机后处理领域最有潜力的技术之一。与传统催化剂相比，纳米催化剂（NC）具有较高的比表面积和催化活性，可强化与反应物接触，从而高效催化脱除NOx和PM排放。本课题通过NTP协同NC脱除NOx及实现PM低温燃烧的机理研究，分析NTP能量密度、NC活性成分和温度对脱除NOx的作用机理，探寻NTP对NC低温活性的影响机制；结合Chemkin软件对NTP处理NOx的中间过程数值模拟，探寻NOx在NC微反应区内的化学机理；定量描述PM粒径分布、组分变化以及微观结构的变化规律，分析NTP-NC系统对PM理化性能的影响因素，结合TGA分析方法，评价PM低温燃烧性能；建立NTP-NC系统作用NOx和PM的反应模型，揭示NTP-NC系统脱除NOx的催化机制及实现PM低温燃烧的作用机理，为同时控制NOx和PM排放的技术发展提供理论基础。

本项目对等离子体协同纳米催化脱除NOx及实现PM低温燃烧的机理进行了深入研究。首先，利用正交试验法制备了一系列以碱土金属为主要活性组分的纳米催化剂，并结合综合测试技术对催化剂的微观形貌、化学组分、晶相结构和催化活性进行了分析，揭示了不同活性组分对催化剂理化性能差异的原因。然后，通过发动机台架试验平台，系统研究了排气温度、能量密度、发动机负荷和催化剂组分对脱除柴油机有害排放的影响规律，通过对等离子体发生器的优化控制，实现了协同纳米催化技术有效脱除NOx和PM排放，并详细分析了影响该技术作用效果的关键因素。在此基础上，利用MOUDI系统对等离子体技术作用前后的PM进行有效提取，通过SEM和EDS测试技术对PM的微观形貌和化学成分差异进行了比较分析，结合GC-MS技术对PM中SOF化学组分进行了详细分析，从微观机制上解释了等离子体降低PM排放的原因。采用TGA热分析技术，详细分析了等离子体作用前后PM起燃温度的变化规律，揭示了等离子体技术实现PM低温燃烧的作用机理。另外，本项目也在催化剂涂覆方式和活性组分与柴油机排气参数的匹配上开展了探索研究，取得了一些进展。总之，通过本青年基金研究，一定程度了揭示了等离子体协同纳米催化技术脱除柴油机NOx排放的作用机制，基本实现了PM低温燃烧，为丰富柴油机超低排放控制新技术提供了试验和理论依据。