改性Cu-Mn/SAPO-34催化剂在SCR脱硝反应中的特性研究

采用浸渍法制备了系列铜锰复合氧化物分子筛催化剂(Cu-Mn/SAPO-34),在固定床反应器上考察不同Cu/Mn质量比对分子筛催化剂选择催化还原NO的影响,利用XRD、NH_3-TPD、H_2-TPR、XPS等手段对催化剂进行了表征分析。结果表明,双金属改性的Cu-Mn/SAPO-34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Cu/Mn质量比为1∶4时,催化剂具有最宽的活性温度窗口,NO_x转化率在250℃已达到85.39%,在300-400℃转化率均达到96%以上,450℃时仍能达到90%。铜和锰物种高度分散于催化剂表面,未改变SAPO-34的晶体结构,且构成协同作用。Cu-Mn共同负载促进了Cu~(2+)向Cu~+的转变,增加了高价态Mn~(4+)和Mn~(3+)的比例,有利于提高低温活性,促进催化反应的进行。Cu-Mn/SAPO-34/1∶4具备丰富的酸性位、良好的氧化还原性能和抗SO_2/H_2O性能,该配比有助于催化剂的催化活性和稳定性的提高。

Performance of the modified Cu-Mn/SAPO-34 catalysts in the selective catalytic reduction of NOx by NH3

A series of Cu-Mn/SAPO-34 catalysts with different mass ratios of Cu to Mn were prepared by impregnation method. The influence of Cu and Mn loading on the denitrification performance was investigated in a fixed-bed reactor. XRD, NH₃-TPD, H₂-TPR, XPS were used to characterize and analyze the catalysts. The results show that the bimetallic modified Cu-Mn/SAPO-34 have excellent catalytic activity and broad active temperature window. Especially, the Cu-Mn/SAPO-34/1:4 catalyst with a Cu/Mn mass ratio of 1:4 has the widest active temperature window, its denitrification rates could reach 85.39% at 250℃, 96% at 300-400℃, and up to 90% at 450℃. Cu and Mn species are highly dispersed on the surface of the catalyst and do not change the crystal structure of SAPO-34. Co-doping of Cu and Mn promotes the transformation of Cu²⁺ to Cu⁺, increases the ratio of Mn⁴⁺ to Mn³⁺, improves the activity at low temperature and promotes the catalytic reaction. Cu-Mn/SAPO-34/1:4 catalyst has rich acid sites, good redox performance and resistance to SO₂ and H₂O, which can improve the activity and stability of the catalysts.