富氧条件下甲烷选择催化还原氮氧化物反应研究

Nitrogen oxides (NOx), a major air pollutant, are critical to the environment and human health. The selective catalytic reduction is the most effective method for NOx elimination. With the worldwide increase of gas boilers and engines fueled by natural gas, the advantages of selective reduction of NOx with methane (CH4-SCR) have become prominent. However, the high stability of CH4 and the complexity of the reaction process seriously hindered the CH4-SCR study. Therefore, we propose this project: Bimetallic zeolites catalysts for CH4-SCR will be prepared by solid-state metalation, organometallic chemistry grafting, and metal encapsulation, which can introduce metal components accurately. Combined by post-treatments, the state of bimetal components will be controlled as desired. Consequently, the synergic effects of different active centers on the as-prepared catalysts would be promoted, as well as the catalytic performances. The metals which own excellent NO oxidation performances (such as Ru, Co, Cr) and can activate CH4 easily (such as In, Mo), and the zeolites which own high thermal and hydrothermal stability (e.g. MFI, CHA, BEA) will be favored. Then the catalytic performances of the catalysts would be evaluated systematically. The real catalytic active centers and key reaction intermediates will be illuminated by in situ IR, in situ UV-Vis and in situ Raman, combined with the pulse-experiment design and the stepwise reaction kinetics study. Subsequently, the mechanism of CH4-SCR reaction would be clarified, which can promote the development of high performance CH4-SCR catalysts.

氮氧化物（NOx）是一种主要的大气污染物，严重危害环境及人类健康。选择催化还原方法是目前最有效的NOx消除方法。随着燃气汽车及燃气锅炉的普及，以甲烷为还原剂选择还原NOx（CH4-SCR）的优势日益凸显，但甲烷的高稳定性和反应历程的复杂性严重阻碍了CH4-SCR的研究。基于此，我们提出本课题的研究：以分子筛为载体，选取钌、钴、铬等NO氧化性能优异的金属和铟、钼等CH4活化金属为活性组分，通过固态金属离子取代、金属有机反应等金属精准引入方法制备双金属-分子筛催化剂，结合不同条件的后处理，实现对引入组分的精确调控，从而促进催化剂不同活性中心之间的协同作用，提高其催化性能；通过原位红外、原位紫外和原位拉曼以及脉冲实验设计，结合分步反应动力学研究和催化性能评价结果，获取反应的真实活性中心和关键中间物种，从而明确反应机理，优化开发高性能CH4-SCR催化剂，为其工业化应用提供理论支持和实验参考。

氮氧化物（NOx）是主要的大气污染物之一，严重危害环境及人类健康。选择催化还原是目前最有效的NOx净化方法。随着燃气汽车及燃气锅炉的普及，以甲烷为还原剂选择催化还原NOx（CH4-SCR）的优势日益凸显，但甲烷的高稳定性和反应历程的复杂性严重阻碍了CH4-SCR的研究。本项目围绕CH4-SCR开展研究，目标是制备多活性中心协同的高活性双金属-分子筛催化剂，获悉其CH4-SCR反应机理，以优化指导高性能催化剂设计。. 通过项目的研究，我们制备出了具有高活性、选择性和稳定性的Cr,In和Ru,In负载的H-SSZ-13催化剂，优化后的0.5%Cr-2%In/H-SSZ-13和0.5%Ru-2%In/H-SSZ-13催化剂在550℃、空速60000h-1条件下，NO转化率超过90%，N2选择性接近100%，并表现出优异的稳定性。通过DRIFTS、TPSR、脉冲实验等方法，结合反应动力学，详细探究了0.5%Ru-2%In/H-SSZ-13催化剂上的CH4-SCR反应机理，发现Ru、In、载体B酸位分别是NO氧化为NO2、中间物种NxOy形成和促进CH4吸附的活性中心，硝基烷烃CH3ONO和CH3NO是重要的反应中间体，多中心协同是其高活性的主要原因。在此基础上，结合应用需求，设计制备出成本更低且环境友好的双金属Ga-Ce/H-ZSM-5催化剂，优化后的4%Ga-2%Ce/H-ZSM-5催化剂在550℃、空速60000h-1条件下，NO转化率高达95%，N2选择性接近100%，同时亦具有优异的稳定性，反应150小时后，转化率仍可达90%，展示出潜在的工业应用前景；其反应机理研究表明：Ce位点可以促进NO氧化为NO2，Ga位点有利于NO生成N2O并促进CH4活化为CO；CO、NO+、N2O和CN/NCO是反应中的四种重要中间体物种，并首次发现N2O是关键含氮中间产物，反应体系不仅存在传统的CH4-SCR过程（CN-/NCO-+NO+→N2+CO/CO2），而且还涉及CO催化还原NO反应（N2O+CO→N2+CO2&NCO+NO→N2+CO2）。. 在项目研究过程中，我们发表SCI论文4篇，会议论文2篇，申请专利2项，其中授权1项，培养博士后1名、毕业博士生和硕士生各3名，博士生在读1名，顺利完成了项目既定的研究目标。