铁矿石催化剂在磁场作用下的低温SCR脱硝机理研究

Low-temperature selective catalytic reduction (SCR) of NOx with iron-ore as catalysts is one of the most effective methods for NOx removal from flue gas. It can reduce re-pollution, save energy and reduce cost in De-NOx processes, and represents the future trend in SCR of NOx. In this project, we will combine low temperature SCR of NOx with magnetic fluidization and exploit the synergies between magnetic fields and iron-ore catalysts for better De-NOx. First, by enhancing the reactant absorption rate of iron-ore catalysts and promoting the formation of free bases and active complexes using external magnetic field, we aim at depressing the activation energy and reaction temperature of SCR of NOx with iron-ore catalysts and thus achieving high efficiency of low-temperature SCR of NOx. Moreover, we also investigate methods to prevent or slow deactivation of iron-ore catalysts and thus extend the catalyst life. Second, we will explore the construction of an experimental facility that can be used for online measurement during the whole process of low-temperature SCR of NOx with iron-ore catalysts. Via approaches from diffuse reflectance infrared fourier transform spectroscopy (DRIFTS）that can capture the formation of transitory substance in the SCR of NOx, such as free base and active complex, the reaction path of low-temperature SCR of NOx with iron-ore catalysts will be found. Finally, we will investigate the mechanism of low-temperature SCR of NOx with iron-ore catalysts under the effects of magnetic fields by theories from quantum chemistry and transportation theory on mass transfer. Our study will demonstrate the potential of iron-ore as highly efficient catalysts in De-NOx that are inexpensive, nontoxic, and can be used in low temperatures, thus lays the foundation of successful applications of the technology of low-temperature SCR of NOx with iron-ore catalysts under the effects of magnetic fields.

铁矿石催化剂的低温SCR脱硝可节约能源、降低成本、减轻二次污染，是SCR脱硝的发展方向。本项目将与磁流化床催化脱硝技术相结合，发挥铁矿石催化剂与磁场的协同作用，用外加磁场强化铁矿石催化剂对反应物的吸附、促进自由基和活化络合物的生成，降低铁矿石作催化剂的脱硝反应活化能和脱硝反应温度，取得低温SCR脱硝反应的高效率，并探索抑制铁矿石催化剂失活的方法，提高铁矿石催化剂的使用寿命。同时，搭建适合进行在线测量的原位实验系统，对铁矿石催化剂低温SCR脱硝进行全过程在线测量，对自由基、活化络合物等SCR脱硝反应中出现的中间产物进行实验辨识，揭示铁矿石催化剂的低温SCR脱硝反应路径，并运用量子化学、输运理论等研究铁矿石催化剂在磁场作用下的低温SCR脱硝机理，使铁矿石成为低温、廉价、无毒、高效的脱硝催化剂，为铁矿石催化剂在磁场作用下的低温SCR脱硝的成功应用打下基础。

铁矿石催化剂的低温SCR脱硝可节约能源、降低成本、减轻二次污染，是SCR脱硝的发展方向。本项目对铁矿石低温SCR脱硝催化剂及其在磁场作用下的特性开展研究。研究了纳米γFe2O3、掺杂改性赤铁矿、锰铁矿、菱铁矿等低温SCR脱硝催化剂的制备和提高这些铁基催化剂低温SCR脱硝活性与抗硫性的方法以及磁场强化铁基催化剂低温SCR脱硝的机理。得到如下主要研究结果。.纳米γFe2O3催化剂表面存在L酸位和B酸位，NH3主要吸附到L酸位形成吸附态的NH3，并有部分NH3吸附到B酸位生成NH4+；O2的存在促进L酸位上的NH3发生脱氢反应生成NH2，且促进NO在催化剂表面吸附，并将其氧化生成硝酸盐和吸附态的NO2。.菱铁矿催化剂具有发达的孔隙结构、较大的比表面积，具有多种L酸位，故在150~300℃内的脱硝效率高于95%。此外，其主要成分γFe2O3不易吸附亚硫酸盐，故抗硫性能较佳。掺杂Ce之后比表面积更大，表面酸性更高，使其在30000h-1的高空速下，催化脱硝效率也大于90%，而且抗硫性更好。.由Ma550℃铁矿石与Fe2O3的混合物构成的催化剂用作流化床床料时，在0.008T磁场下，在220℃脱硝效率超过92%。这是由于磁场抑制流化床中的“气泡”，实现床层中良好的气固接触，促进气态反应物与催化剂颗粒之间的热质传递；同时，磁场影响Fe离子外层不饱和轨道d电子的自旋运动，使得Fe基催化剂在形成中间活化自由基过程中的电子转移能力增强，强化活化过程。.围绕上述研究在国内外核心刊物发表论文17篇，其中5篇被SCI收录，13篇被EI收录。参加国际学术会议作口头报告4篇，参加全国性学术会议并做报告9篇。申请国家发明专利并获公开5项。培养博士生4名，其中1人毕业并获博士学位，培养硕士生10人，其中6人毕业并获硕士学位。在本项目研究基础上，开发出改性菱铁矿低温SCR脱硝催化剂并得到江苏省环保厅资助开展改性菱铁矿低温SCR脱硝催化剂的工业应用研究，有望近期将此催化剂应用到工业炉窑的革新改造中，为我国的环保事业作贡献。