【摘要】 低温NH3-SCR脱除NOx是一种有潜力的烟气脱硝技术。综述了低温NH3-SCR脱硝催化剂的研究现状,重点介绍了锰基催化剂、钒基催化剂,以及其他金属氧化物基催化剂的研究状况,阐述了制备方法、催化剂载体,以及以不同金属改性对催化剂脱硝活性的影响。其中具备高比表面积、良好非晶态结构的低温NH3-SCR催化剂都有良好的低温脱硝活性。以CeO2改性锰(MnOx)基催化剂为例,探讨了低温NH3-SCR脱硝催化剂的脱硝机理。反应气体(NH3、NO和O2)在催化剂表面的吸附在低温NH3-SCR脱除NOx中发挥了重要作用。CeO2改性锰基催化剂催化NH3-SCR反应过程中涉及ER机理和LH机理,并且NH2与气态NO发生反应生成亚硝胺(NH2NO),进一步分解为N2和H2O是关键步骤。就燃煤烟气中水蒸气(H2O)和SO2在低温条件下对低温NH3-SCR脱硝催化剂的失活机制进行了阐述。烟气中的水蒸气与反应气体的竞争性吸附能够导致催化剂脱硝活性的降低。水蒸气(H2O)和SO2共同存在对低温NH3-SCR催化剂脱硝活性的影响表现为两者共同作用。烟气中水和SO2存在时生成的硫酸盐沉积在催化剂表面,并导致催化剂失活。更多还原

【Abstract】 The present paper is aimed to give a summary and commentary on the research advances for low-temperature NH3-SCR catalysts,such as the selective catalytic reduction(SCR) of NOx with NH3 at low temperature.The catalysts mentioned above usually serve as a promising technique for NOx removal from the flue gases.When preparing this paper,we have searched through the comprehensive literatures dedicated to the field of low-temperature NH3-SCR catalysts.An outstanding example in this way is MnOx-based catalysts,VOx-based catalysts,another kind,as we mentioned about,and some other metal oxide-based catalysts.These catalysts with high surface area and well amorphous structure all display high catalytic activities for low-temperature SCR of NOx with NH3.The study of the mechanism and impact of SCR of NOx with NH3 at low temperature on CeO2 modified MnOx-based catalysts indicates that the adsorption of NH3,O2 and NOx for the catalysts play an important role in the low-temperature catalytic series along with SCR of NOx with NH3.The SCR reaction of NOx and NH3 to the CeO2 modified MnOx-based catalysts also prove to carry on the ER mechansm and LH mechanism.Research activities in this way indicate that preparing methods of catalysts,the catalyst support,and the modified metal oxide may all have strong impact on the catalytic activities for low-temperature SCR of NOx with NH3.The reaction of NH2— and gas NO,and then the composed NH2NO all tend to further decompose to give N2 and H2O and then resulted in a typical SCR mechanism reported for CeO2 modified MnOx-based catalysts.In this paper,we have also made a discussion over the deactivation mechanism of low-temperature NH3-SCR catalysts due to their reaction to water vapor and sulfur dioxide in the flue gases.The competitive adsorption of the water vapor with the reaction gases on the surface of the catalysts tends to decrease the catalytic function of the low-temperature catalysts.And,water vapor and sulfur dioxide in the flue gases may have a combined effect on the catalytic activity of the low-temperature catalysts.Besides,the resulted sulfates with the presence of water vapor and sulfur dioxide are likely to deposit on the surface of the catalysts and result in the deactivation of the low-temperature NH3-SCR catalysts.Future research tendency in the above-said key areas will surely bring great benefits to the development of such catalysts.更多还原