Effects of hydrothermal aging on NH3-SCR reaction over Cu/zeolites

The effects of hydrothermal treatment on model Cu/zeolite catalysts were investigated to better understand the nature of Cu species for the selective catalytic reduction of NOx by NH3. After hydrothermal aging at 800 °C for 16 h, the NOx reduction performance of Cu-ZSM-5 and Cu-beta was significantly reduced at low temperatures, while that of Cu-SSZ-13 was not affected. When the zeolite framework aluminum species were probed using solid state 27Al MASNMR, significant reduction in the intensities of the tetrahedral aluminum peak intensity was observed for Cu-ZSM-5 and Cu-beta, although no increase in the intensities of the octahedral aluminum peak was detected. When the redox behavior of Cu species was examined using H2-TPR, it was found that Cu2+ could be reduced to Cu+ and to Cu0 for Cu-ZSM-5 and Cu-beta catalysts, while Cu2+ could be reduced only to Cu+ in Cu-SSZ-13. After hydrothermal aging, CuO and Cu-aluminate species were found to form in Cu-ZSM-5 and Cu-beta, while little changes were observed for Cu-SSZ-13.

After hydrothermal aging at 800 °C for 16 h, the NOx reduction performance of Cu-ZSM-5, Cu-beta and Cu-Y were significantly reduced, while that of Cu-SSZ-13 was not affected.Figure optionsDownload high-quality image (133 K)Download as PowerPoint slideHighlights
► Hydrothermal aging does not affect the NH3-SCR performance of Cu-SSZ-13.
► Low temperature SCR activity of Cu-ZSM-5 and Cu-beta significantly reduced by hydrothermal aging.
► CuO and Cu-aluminate species formed in Cu-ZSM-5 and Cu-beta during hydrothermal treatment.
► No structural changes were observed for Cu-SSZ-13.