Investigation of the differences in the DeNO(x) performance and hydrothermal stability of T zeolite catalysts modified with copper & iron

In this experiment, a highly crystalline T-type zeolite was rapidly synthesized by hydrothermal method within 24 h and its NH3-SCR catalytic performance after Cu2+or Fe3+modification was studied. The experimental results show that T-type molecular sieve is workable in industrial tail gas denitrification. The F-Fe-T series samples can maintain more than 80 % of the nitrogen oxide conversion rate in the range of 280–600 °C and the F-Cu-T catalyst could achieve more than 80 % at about 170 °C. At the same time, it was found that the zeolites modified by two metal ions had obvious differences in hydrothermal stability. The results suggested that the Fe-T catalyst can maintain excellent crystal structure and NH3-SCR catalytic activity even after hydrothermal aging at 800 °C for 6 h, but the skeleton structure of the Cu-T catalyst is completely destroyed. The main reason may be that a small amount of FeOx species with a low degree of agglomeration formed in the fresh Fe-T series catalysts, which interacted with the framework Al to form Fe-O-Al species and FeOx species were re-dispersed into isolated Fe3+species during hydrothermal aging, thus avoiding a large amount of hydrolysis of the framework Al. The framework Al of Cu-T series catalysts are hydrolysed during hydrothermal aging, which leads to the deactivation of the catalyst. In summary, T-type zeolites exhibit excellent catalytic activity after copper or iron ion exchange, but the Fe-T series catalysts have better hydrothermal stability.