双金属Ce-Mn/ZSM-5催化剂的制备及NH3-SCR脱硝性能研究

采用浸渍法制备了铈锰复合氧化物分子筛催化剂(Ce-Mn/ZSM-5),在固定床反应器上考察不同Ce/Mn质量比对分子筛催化剂选择催化还原NO的影响,利用XRD、TEM、NH_3-TPD、H_2-TPR、in-situ DRIFTS等手段对催化剂进行了表征分析。结果表明,双金属改性的Ce-Mn/ZSM-5催化剂在NH_3-SCR反应中表现出较为优异的催化活性,具有较宽的活性温度窗口。当Ce/Mn质量比为0.4时,催化剂具有最佳的脱硝效率,在265-465℃脱硝率均可达到80%以上,在370℃时,NO的转化率最高可达97.28%。锰和铈物种高度分散于催化剂表面,未改变ZSM-5的晶体结构,且构成协同作用。0.4Ce-Mn/ZSM-5具备丰富的酸性位、良好的氧化还原性能,该配比有助于催化剂的催化活性和稳定性的提高,在NH_3-SCR反应过程同时遵循E-R机理和L-H机理。

Study on the preparation and catalytic performance of bimetallic Ce-Mn/ZSM-5 catalyst for selective catalytic reduction of nitric oxide by NH3

A series of Ce-Mn/ZSM-5 catalyst with different mass ratios of Ce and Mn was prepared by impregnation method, and the influence of Ce loading on denitrification performance was investigated in a fixed-bed reactor. XRD, TEM, NH₃-TPD, H₂-TPR, in-situ DRIFTS were used to characterize the catalysts. The results show that the bimetallic Ce-Mn/ZSM-5 have a broad active temperature window. Especially, the catalyst with Ce/Mn mass ratio of 0.4 has the best denitrification efficiency, and the denitrification rate can be higher than 80% between 266 and 465℃,and up to 97.28% at 370℃.Manganese and cerium species can be well dispersed on the surface of the support without changing the crystal structure of ZSM-5.0.4Ce-Mn/ZSM-5 catalyst has abundant acidic sites, good redox performance. There are both E-R mechanism and L-H mechanism in NH₃-SCR reaction.