不同分子筛负载锰铈催化剂的低温NH3-SCR脱硝性能

摘要

With various zeolites such as β, ZSM-5 and USY as the support, a series of Mn-Ce catalysts were prepared by impregnation method and characterized by XRD, BET, NH3-TPD, H2-TPR and XPS;their catalytic performance in the NH3-SCR of NOx at low temperature was investigated. The results show that all these catalysts are highly active in the NH3-SCR reaction at low temperature; especially, over the Mn-Ce/USY catalyst, the conversion of NOx reaches 90% at 107 ℃. After loaded of manganese and cerium, the specific surface area and pore volume of supported catalysts are decreased. Amorphous MnOx as the active component and crystalline CeO2 are detected on the surface of ZSM-5 zeolite. The weak acid sites on the catalyst surface probably play an important role in the NH3-SCR at low temperature. Meanwhile, a high atomic ratio of Mn4+/Mn3+ and concentration of adsorbed oxygen may also promote the NH3-SCR reaction at low temperature.%分别以β、ZSM-5和USY分子筛为载体,采用浸渍法制备了锰铈催化剂,对其低温NH3-SCR反应性能进行了评价,并采用XRD、BET、NH3-TPD、H2-TPR以及XPS对催化剂进行了表征。结果表明,三种分子筛负载的锰铈催化剂均具有较好的低温NH3-SCR反应活性,其中,Mn-Ce/USY的催化性能最好,在107℃时NOx 转化率可达到90%。负载锰铈后催化剂的比表面积和孔体积均有所下降；活性组分MnOx 主要以无定型态分布于催化剂表面,且在ZSM-5上检测到聚集的CeO2。催化剂表面弱酸对低温NH3-SCR反应起主要作用,催化剂表面上活性组分的表面浓度和氧化态明显不同,较高的Mn4+/Mn3+原子比和吸附氧表面浓度对提高催化剂的低温NH3-SCR反应活性有利。