Study on the improvement of ultra-low temperature performance and adsorption mechanism of Mn and Ce based denitrification catalysts by"NO2 SCR"
The catalysts supported by Mn7Fe4Ce9Ox/AlOx and Mn3Fe1Ce6Ox/AlOx prepared by co-precipitation method were first evaluated by standard SCR mechanism reaction under 7777 h-1 intake condition.The catalytic activity of the two catalysts was only about 10%at 60℃.Then,the concentration ratio of NO2/NOx in intake air was increased under the same conditions,and the concentration ratio of NO2/NOx in intake air was 0,14.3%,28.6%,42.8%,57%,71.4%,85.7%and 100%.The results show that the denitrification efficiency of Mn3Fe1Ce6Ox/AlOx catalyst can be 64%at 60℃,which is about 58%higher than that of the first evaluation.Experimental and theoretical calculations show that Mn3Fe1Ce6Ox/AlOx catalyst has larger specific surface area and stronger adsorption and activation of NO2,which improves the efficiency of NO2 fast SCR mechanism reaction.At the same time,the in situ infrared test found that the adsorption mode of Mn3Fe1Ce6Ox/AlOx catalyst changed significantly when the concentration ratio of NO2/NOx increased,and the E-R and L-H mechanism mainly adsorbed by NH3 changed to the E-R and L-H mechanism mainly adsorbed by NO2.The change of adsorption mechanism may be the key factor to improve the performance of catalyst at ultra-low temperature.This work provides a promising strategy for exploring efficient and economical denitrification of NH3-SCR,as well as experience for ultra-low temperature flue gas treatment and guidance for new flue gas treatment processes.
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