基于铈基催化剂的烧结烟气低温协同脱硝脱二噁英机理研究

A large amount of NOx and PCDD/Fs exists in iron ore sintering process. For the general sintering waste gas, its temperature is lower, and it contains SO2, H2O and fly ash, which seriously restrict the effective removal of sintering pollutants. We develop the ceria-based bifunctional catalysts to explore the way of denitration collaborative PCDD/Fs removal at low temperature. According to the emission characteristics of sintering waste gas, the project will combine ceria (CeO2) with graphene and mesoporous structure to build mesoporous ceria-graphene composite oxide catalysts for higher catalytic activity and stronger H2O/SO2 resistance. Furthermore, the project will deeply research the reactive processes at gas-solid interface by using in-situ analysis and advanced characterization methods, and solve the scientific problem: one is to reveal the catalytic removal of two kinds of pollutants synergy or inhibition; the second is to make clear the characteristics of waste gas pollutants poisoning mechanism and the thoughts of improved poisoning resistance. The performance of the catalysts for low-temperature deNOx and PCDD/Fs removal was also studied by using the sintering cup experiment to simulate the sintering waste gas condition. The expected results are to provide theoretical foundation and technical support for controlling of NOx and PCDD/Fs emission simultaneously.

烧结烟气中含有大量的氮氧化物（NOx）和二噁英（PCDD/Fs）等大气污染物。由于烧结烟气温度较低，且含有SO2、H2O和粉尘等，严重制约烧结污染物的有效脱除。本项目拟建立低温铈基双功能催化体系，探索低温催化还原NOx并同时氧化二噁英的途径。针对烧结烟气的特点，将二氧化铈（CeO2）与石墨烯、介孔结构相结合，制备抗水抗硫性能优异的介孔CeO2-石墨烯复合氧化物催化剂；采用原位分析方法和先进表征手段研究反应气-固界面过程，揭示催化脱除两种污染物的协同作用机理，从分子原子水平上明确烟气特征污染物的中毒机制，进一步指导抗中毒催化剂的设计和再生；利用烧结杯实验模拟烧结烟气工况，研究催化剂低温脱硝脱二噁英性能，评价其工业化应用前景，为实现烧结烟气高效协同脱除NOx和二噁英提供理论依据和技术支撑。

烧结烟气中含有NOx、SO2、PCDD/Fs等污染物。近年来，随着钢铁行业超低排放要求逐步实施，烧结烟气多污染物协同净化已成为钢铁企业亟待解决的关键科学问题之一。烧结烟气温度低、成分复杂、污染物种类多，传统催化剂难以实现低温条件下多污染物协同减排。本项目针对烧结烟气特点，设计开发了一种低温协同脱硝脱二噁英的介孔铈基催化剂，并开展了烧结杯中试试验，系统评估了该催化剂的应用前景。主要研究内容如下：.研究了Ce-V催化剂的宏观调控及载体提高催化性能机理。在水热法制备过程中，对Ce-V(2.5)催化剂晶粒的生长方向进行调控，得到了纳米形貌催化剂。引入TiO2载体可以显著提高催化剂的活性，催化机理表明，反应物首先通过亲核取代垂直吸附于催化剂表面，然后被活性组分Ce活化，活化后的二噁英分子再被Ce4+→Ce3+释放的活性氧氧化分解。.研究了氧化石墨烯改性对提高Ce-V-Ti催化剂低温活性的机理。氧化石墨烯修饰后的Ce-V-Ti催化剂比表面积增大，表面形态改变，活性物质分散性提高。添加质量分数0.7%的GO-4氧化石墨烯对Ce-V-Ti催化剂的活性提升效果最优。微量的氧化石墨烯通过强化催化剂吸附能力和氧化能力，改变吸附模式，高效提高铈基催化剂低温降解活性。.探明了催化剂中毒失活机理。稀土元素Ce可抑制硫酸盐的形成，氧化性石墨烯有利于NH4HSO4分解，因此Ce(15)-V(2.5)-Ti/GO(0.7)催化剂表现出更好的抗硫中毒性。氧化性石墨烯修饰后，催化剂微观结构中出现了Ti5O9新相，增加了催化剂中氧空位的数量，有利于提升催化剂的脱硝性能。实验室研究表明：150℃条件下，Ce(15)-V(2.5)-Ti/GO(0.7)催化剂降解二噁英的效率达到77%，协同脱硝效率达到80%以上。.烧结杯中试试验结果表明：烧结烟气150℃时，Ce(15)-V(2.5)-Ti/GO(0.7)催化剂稳定运行后，二噁英减排率为63.2%，NOx减排率为72.0%。研究结果将为该催化剂的工业化应用提供技术支撑。