A comparison of hydrothermal aging effects on NH3-SCR of NOx over Cu-SSZ-13 and Cu-SAPO-34 catalysts

A comparison of hydrothermal aging effects on NH3-SCR of NOx over Cu-SSZ-13 and Cu-SAPO-34 catalysts

Type	Journal Article
Author	Di Wang
Author	Yasser Jangjou
URL	http://www.sciencedirect.com/science/article/pii/S092633731400633X
Volume	165
Pages	438-445
Publication	Applied Catalysis B: Environmental
Date	April 2015
Abstract	Reports comparison of the impacts of hydrothermal aging on the selective catalytic reduction (SCR) performance of both Cu-SSZ-13 and Cu-SAPO-34. Upon 750 °C hydrothermal aging for 16 h, the NO conversions on both materials were somewhat maintained, however, a significant difference appeared after hydrothermal aging at 800 °C. The Cu-SSZ-13 sample resulted in remarkably lower NO conversions at all temperatures tested while the Cu-SAPO-34 still maintained its high SCR activity. In fact, the NO conversions at low temperatures (below 350 °C) over Cu-SAPO-34 were even enhanced upon high temperature treatment, suggesting an increase in active sites, which is possibly due to a post solid state ion exchange process driven by high temperatures. Consistently, for the Cu-SAPO-34 sample, NH3-TPD results suggest an increase in Lewis acid sites after hydrothermal aging at 750 and 800 °C as compared with the fresh one. However, for the Cu-SSZ-13 sample, DRIFTs characterization results suggest a decrease in acid sites (Brønsted and Lewis), and a significant reduction in the amount of exchanged Cu2+ sites upon aging at 800 °C, leading to a drastically decreased SCR activity.