改性Fe2O3/AC催化剂烧结烟气低温SCR脱硝活性优化机理

Low-temperature selective catalytic reduction (SCR) of NOx with Fe2O3/AC as catalysts is one of the most effective methods for NOx removal from sintering flue gas. It can reduce re-pollution and reduce cost in De-NOx processes. At present, however, Fe2O3/AC catalysts which are used as NOx removal from sintering flue gas need to further improve the activity of low-temperature SCR of NOx and poison resistance. In this project, microwave is introduced to prepare modified Fe2O3/AC catalysts, and one or more additives are also added into Fe2O3/AC catalysts in order to improve the activity of low-temperature SCR of NOx. The effect of preparation process parameters and operation parameters on the activity of low-temperature SCR of NOx for sintering flue gas will be deeply investigated. At the same time, the optimization mechanism of low-temperature SCR of NOx with modified Fe2O3/AC catalysts will be analyzed. Then, the internal relations between activity of low-temperature SCR of NOx and those parameters will be revealed. The adsorption/desorption capacity of NO and NH3 over modified Fe2O3/AC catalysts is also investigated and the intermediate products will be also studied in order to study the mechanism of low-temperature SCR of NOx. Finally, the optimization mechanism how microwave and different additives improve the low-temperature SCR of NOx and poison resistance with modified Fe2O3/AC catalysts will be put forward. Moreover, the methods to prevent or slow deactivation of modified Fe2O3/AC catalysts will be investigated and thus extend the catalyst life. The purpose of this project is to obtain the detailed knowledge of low-temperature SCR of NOx for modified Fe2O3/AC catalysts and to look for the methods which can improve its activity of low-temperature SCR of NOx and poison resistance. So it can provide a scientific basis for optimizing formula for reference of applicable departments.

活性焦担载Fe2O3催化剂烧结烟气低温SCR脱硝可降低成本、减少二次污染。但目前，将其用于烧结烟气低温SCR脱硝还需要进一步提高其低温脱硝活性和抗硫抗水性能。本项目将微波技术引入到催化剂的制备过程，同时添加一种或多种助剂对活性焦担载Fe2O3催化剂进行改性，深入研究其制备过程参数及运行参数对烧结烟气低温脱硝活性的影响规律，分析其优化脱硝反应机理，确定其低温脱硝性能与各参数之间的内在关系。探究改性的活性焦担载Fe2O3催化剂NO和NH3脱吸附特性及瞬态反应表面吸附的中间产物，确定其低温脱硝反应机理，揭示微波参数及助剂优化其低温脱硝性能的主要机理，并探索抑制其失活的机理及方法。通过该项目研究，掌握多种因素影响改性的活性焦担载Fe2O3催化剂脱硝性能的优化机理及抗硫抗水机理，寻求提高活性焦担载Fe2O3催化剂低温脱硝活性和抗硫抗水性能的方法，为应用部门筛选优良的低温催化剂提供实验依据和理论指导。

活性焦担载铁基催化剂用于烧结烟气低温SCR脱硝存在脱硝活性低和抗中毒性能差的问题。本项目采用多种实验技术结合密度泛函理论，首先，研究了制备工艺对活性焦担载铁基催化剂低温脱硝活性的影响，获得了最佳的制备工艺参数。明确了气体分子在不同晶型铁氧化物表面的吸附行为、脱硝反应路径以及决速步骤，发现了中间体双齿配位硝酸盐的存在不利于脱硝反应进行。从理论上揭示了NO2存在的“快速-SCR”反应的NOx转化率比标准SCR反应快的根本原因。其次，提出采用过渡金属或稀土金属（Mn、Ce、Cr等）掺杂改性活性焦担载铁基催化剂，催化剂的比表面积增大，表面吸附氧及酸位点数量增加，还原性能增强。尤其，掺杂的金属原子与铁原子产生协同作用，可以提高对气体分子的吸附能力，降低NO氧化反应的能垒，促进活性焦担载铁基催化剂表面NO2的生成，从而使催化剂在120~240℃脱硝活性显著提高。此外，掺杂的金属原子增加了SO2在自身和Fe位点的氧化势垒，酸位点优先酸化或抑制催化剂表面上SO3的生成，均可以使活性焦担载铁基催化剂抗中毒性能得以提升。最后，为了明确载体对铁基脱硝催化剂活性的影响，采用水浴加热-燃烧法制备了有机碳材料作为助溶剂的铁基脱硝催化剂。通过Cu改性后，由于Cu-Fe双金属的协同效应使Cu位点和Fe位点对气体分子的吸附能力提高，促进了SCR脱硝反应的进行，因此催化剂获得了优异的脱硝活性。尤其，Cu的引入抑制了铁基催化剂表面SO2氧化，使形成硫酸铵盐的前驱体SO3缺乏，催化剂抗硫性能明显提升。基于对活性焦担载铁基催化剂低温脱硝性能及抗中毒性能的研究成果，为铁基催化剂脱硝效率的提高、抗中毒性能的增强以及催化剂的设计提供了科学依据。