氢气协同H2-SCR反应中原位产生氨还原NOx的研究

The emission regulation of NOx has become more and more stringent and there are some problems to be solved for the catalytic reduction of NOx emitted from diesel engine at low temperatures. In this project, multi-functional catalyst will be designed, on which the formed N atoms by the dissociation of NO will combine with the H atoms by the dissociation of hydrogen to form ammonia. The in-situ formed ammonia will reduce NOx together with hydrogen. The cooperation of selective catalytic reduction of NOx by hydrogen (H2-SCR) and ammonia (NH3-SCR) can result in the improved selectivity to N2 and H2 as well as the wide activity temperature window. Based on the catalytic performance evaluation and the structure characterization, the interaction among the different metals in the multi-functional catalyst and the roles of the active sites for the H2-SCR and NH3-SCR of NOx will be elucidated. In-situ Fourier Transform Infrared spectroscopy (FT-IR) study coupled with the steady-state isotopic transient kinetic analysis and density functional theory (DFT) calculations will be used to investigate the reaction mechanisms of H2-SCR and NH3-SCR of NOx, providing the fundamental understanding for this novel technique route. This project will promote the research in the catalytic removal of NOx emitted from diesel engine with important academic and social significance.

鉴于NOx排放标准日趋严格和柴油车排放NOx低温催化控制技术存在的问题，本项目拟通过多功能催化剂的设计，在氢气选择性催化还原NOx(H2-SCR)的同时，使NO离解生成的N与H2离解产生的H结合生成NH3或NH4+，实现氢气协同原位产生的NH3高效还原NOx的新技术路线。H2-SCR和NH3-SCR协同还原NOx，不但提高N2和氢气的选择性，而且拓宽活性温度窗口。通过对催化剂的综合性能评价和结构表征，揭示催化剂各组份的相互作用及其与H2-SCR和NH3-SCR的内在联系；并结合原位红外(FT-IR)研究、稳态同位素瞬变动力学分析和基于密度泛函理论(DFT)的分子模拟，阐明多功能催化剂上H2-SCR和NH3-SCR协同进行的反应机理，为氢气协同H2-SCR反应中原位产生的氨还原NOx的新技术路线提供科学依据。本项目对实现柴油车排放NOx的污染控制，具有重要的科学价值与社会意义。

NOx作为一种典型的致霾污染物，其污染控制日益引起人们关注。本项目对氢气选择性催化还原NOx(H2-SCR)以及氢气协同原位产生的NH3还原NOx（NH3-SCR）开展研究，并按照计划顺利完成。设计合成了Pd-Mn/TiO2-Al2O3、Pt-WO3/TiO2以及Pt-MoO3/TiO2等催化剂，研究了其对H2-SCR的性能及其影响因素，发现上述催化剂对H2-SCR具有良好的催化活性。借助N2吸附、XRD、XPS、H2-TPR、NOx-TPD、XANES等手段对催化剂的微观结构进行了分析表征，明确了催化剂的结构和性能的构效关系。借助原位漫反射红外光谱(DRIFTS)技术，揭示了在H2-SCR的同时，原位产生的NH3也参与NOx的还原反应，从而使催化剂显示出良好的脱硝性能。构筑的Mn-Ce-Ti、V-Ce-Ti和WO3/MnZr等催化剂对NH3-SCR具有良好的脱硝性能，双（或多）金属间的协同效应使催化剂的氧化-还原性及表面酸性提高，从而促进了NH3-SCR反应的进行。通过DRIFTS研究，揭示了NH3-SCR反应中涉及的反应中间体及反应路径，提出了NH3-SCR脱硝的反应机理。本项目的实施，对NOx的污染控制具有重要的科学价值与社会意义。