Effect of Hydrothermal Aging with C2H4 on Selective Catalytic Reduction of NOx over Cu/SSZ-13 catalysts

Yu-Ren  Chen, Chemical Engineering Department at UVA

NOx emissions control using selective catalytic reduction (NH3-SCR) over Cu/SSZ13 catalysts  has been well studied. These catalysts are currently commercially used and have proved relatively durable. However, they do still deactivate with time in use. Hydrothermal aging and sulfur poisoning are well known phenomena. Expanding on these, in thus study, hydrothermal aging in the presence of ethylene was investigated. Cu/SSZ-13 catalysts ware hydrothermally aged at 600 °C for 25 h and 50 h with and without C2H4 added to the entering gas mixture. Hydrothermal aging led to a decrease in catalyst oxidation ability, but in the presence of ethylene, less oxidation reactivity was lost. Since at high temperature, NH3 oxidation can be significant, this greater oxidation reactivity leads to decreased SCR conversions under NH3:NO ratios of 1. These results suggest a difference in the trends in copper site changes during the aging protocols. H2-TPR and DRIFTS were used to test this hypothesis.