Wej. Van Kooten et al., Hydrothermal deactivation of Ce-ZSM-5, Ce-beta, Ce-mordenite and Ce-Y zeolite deNOx catalysts, CATAL LETT, 63(3-4), 1999, pp. 227-231
The hydrothermal stability of Ce3+ zeolite catalysts used for selective cat
alytic reduction of NOx was investigated. Aging of Ce-ZSM-5, Ce-beta, Ce-mo
rdenite and Ce-Y catalysts consisted of steaming in 10 or 12 vol% water at
600 degrees C for 3-99 h. Ce-ZSM-5 (Si/Al ratios: Si/Al=17.1, 22.6 and 146.
6) and Ce-mordenite (Si/Al=6.4, IE=77.2%) showed fast deactivation. Ce-beta
(Si/Al=12, IE=68.4%) and Ce-Y (Si/Al=2.8, IE=122%) are significantly more
stable zeolite catalysts, Ce-beta being the most active of these two. Ce-be
ta and Ce-ZSM-5 catalysts - both having high initial activities - were char
acterized with Si-29-NMR and Al-27-NMR. Especially Ce-ZSM-5 showed an incre
ase of non-framework Al, meaning that the zeolite suffered from dealuminati
on.