Release Time:2019-03-12  Hits:

Indexed by: Journal Article

Date of Publication: 2017-11-15

Journal: APPLIED CATALYSIS B-ENVIRONMENTAL

Included Journals: EI、SCIE

Volume: 217

Page Number: 421-428

ISSN: 0926-3373

Key Words: NH3-SCR; Cu-SSZ-13 catalyst; Organotemplate-free synthesis of SSZ-13; Na+ effect; Hydrothermal stability

Abstract: The relatively low activity at lower temperatures and high cost of SSZ-13 zeolite from organotemplate synthesis are two of major problems of presently commercialized Cu-SSZ-13 catalysts for NH3-SCR reaction. Cu-exchanged Al-rich SSZ-13 catalysts with Si/Al=4 from organotemplate-free synthesis have been prepared, and show superior NH3-SCR performance with NO conversions above 85% at wide-temperature window ranging from 150 to 650 degrees C. Cu-Na-SSZ-13 catalysts with varied amount of residual Na+ were prepared by partial ion-exchange of as-prepared Al-rich Na-SSZ-13, and it's found that Cu-Na-SSZ-13 catalyst with moderate Na+ content can improve both the low-temperature activity and its hydrothermal stability. Al-27 and H-1 MAS NMR spectra indicate that residual Na+ can stabilize the framework Al in Al-rich SSZ-13 zeolite. UV-Vis-NIR and H-2-TPR spectra demonstrate that Na+ co-cations enhance the reducibility of Cu2+, whereas too much amount of Na+ may result in the formation of CuOx, during the hydrothermal treatment, and further decrease the hydrothermal stability of Cu-Na-SSZ-13 catalyst. The optimized organotemplate-free Cu-Na-SSZ-13 with 2.7 wt% Cu and 1.7 wt% Na exhibits almost the same NO conversions as the commercial high-silica Cu-SSZ-13 catalyst at 150-550 degrees C after 750 and 800 degrees C hydrothermal aging, and shows promising practical applications. (C) 2017 Elsevier B.V. All rights reserved.