Cu-exchanged Al-rich SSZ-13 zeolite from organotemplate-free synthesis as NH3-SCR catalyst: Effects of Na+ ions on the activity and hydrothermal stability
Zhao, Z. and Yu, R. and Zhao, R. and Shi, C. and Gies, H. and Xiao, F.-S. and De Vos, D. and Yokoi, T. and Bao, X. and Kolb, U. and Feyen, M. and McGuire, R. and Maurer, S. and Moini, A. and Müller, U. and Zhang, W.
APPLIED CATALYSIS B: ENVIRONMENTAL
Volume: 217 Pages: 421-428
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 °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. 27Al and 1H MAS NMR spectra indicate that residual Na+ can stabilize the framework Al in Al-rich SSZ-13 zeolite. UV-Vis-NIR and H2-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 °C after 750 and 800 °C hydrothermal aging, and shows promising practical applications. © 2017 Elsevier B.V.