稀土CeO2改性介孔材料的可控合成及其脱硝性能研究

Nitrogen oxides (NOx) are the main pollutants that cause acid rain, photochemical smog and ozone layer destruction, and ammonia selective catalytic reduction (NH3-SCR) is a widely used technique for NOx reduction currently. Considering the abundant rare earth resources in our country and its excellent performance in NOx catalysis elimination, the CexM1-xOy mesoporous catalysts with different pore sizes are fabricated by the template method based on the basic catalytic principle and material structure of SCR denitration. We will study systematically the influence of pore sizes on the particle size, dispersion, chemical valence and surface acidity of active ingredient, and correlate them with the activity of catalytic denitrification, N2 selectivity, water and sulfur resistance to clarify the structure-activity relationship. Finally, we attempt to use some in-situ characterization techniques to study the changes of gaseous reactant molecules and the state of intermediate species, identify reactive center and finally the synergistic effect of catalyst structure and active component in catalytic reaction process are clarified. Through the implementation of this project, it is expected to provide theoretical basis and technical support for designing new efficient NH3-SCR denitration catalysts, deepening understanding of the catalyst structure and anti-poisoning mechanism.

氮氧化物（NOx）是造成酸雨、光化学烟雾和臭氧层破坏的主要污染物，氨选择性催化还原法（NH3-SCR）是目前NOx消除的主流手段。本项目基于我国丰富的稀土资源及其在NOx催化消除方面的优异性能，从SCR脱硝基本催化原理和材料结构出发，采用模板法设计合成不同孔径尺寸的CexM1-xOy介孔催化剂，系统研究催化剂孔径尺寸对活性组分的粒径、分散度、化学价态、表面酸性等的影响，并将它们和催化脱硝的活性、N2选择性、抗水耐硫性等关联来明晰构效关系；在此基础上，借助多种原位表征手段深入研究催化脱硝反应气体的吸脱附状况和中间物种的状态，确立反应活性中心，最终阐明催化剂结构和活性组分在催化脱硝过程中的协同效应。该项目实施将为设计新型高效NH3-SCR脱硝催化剂、加深对催化剂结构和抗中毒机理的认识提供理论依据和技术支持。

氮氧化物（NOx）排放带来的环境问题已成为制约我国经济社会发展的重要瓶颈，氨选择性催化还原（NH3-SCR）技术是目前NOx消除的主流手段。铈基材料因其多变的价态（Ce4+/Ce3+）和优异的氧化还原性能而受到研究者的关注，同时介孔结构具有比表面积大，孔径尺寸可调和空间限域等特点，本项目采用不同方法合成了多种改性铈基复合脱硝催化剂并研究了其化学组分调变和结构调变（介孔结构、限域空间）对催化剂物理化学性质和脱硝性能的影响规律，并提出可能的反应机理。主要研究结果如下：（1）铈基脱硝催化剂的表面酸性质是影响催化剂脱硝性能的关键因素，这主要是因为其可促进NH3的吸附，同时抑制SO2的吸附。因此，通过调变催化剂的制备方法在催化剂表面引入更多的酸性位既可以提高铈基催化剂的NO转化率同时改善催化剂的抗硫性能；（2）硫酸氢铵（ABS）可以在Fe2O3催化剂表面达到动态平衡，削弱ABS对催化剂的毒害，并以此结论为基础，制备了具有工业应用潜力的低温FeMnCeAl脱硝催化剂；（3）结构调变可改变ABS对催化剂脱硝性质的影响，大尺寸的限域空间可以显著增强催化剂的抗SO2性能；（4）介孔催化剂表面沉积的ABS在较低的温度下分解后转变为金属硫酸盐，由于硫酸金属盐物质的强诱导作用，催化剂表面的酸性和氧化还原性质均得到显著改善，也可以有效地促进了NH3-SCR催化反应活性。