SELECTIVE CATALYTIC REDUCTION OF NO WITH PROPENE OVER CUMFI ZEOLITES - DEPENDENCE ON SI AL RATIO AND COPPER LOADING/

Selective catalytic reduction of nitrogen oxide by propene in an oxidi sing atmosphere was studied on several CuMFI catalysts with different Si/Al ratios (11 less than or equal to Si/Al less than or equal to 100 ) and different copper loadings (between 0 and 5.5 wt-%). From the res ults it was observed that the influence of zeolite Si/Al ratio on CuMF I catalytic activity for NO SCR by propene is dependent on the catalys t copper loading. Furthermore, the effect of catalyst copper loading o n catalytic performance depended on the catalyst Si/Al ratio. The resu lts also demonstrated that CuMFI catalysts with different Si/Al ratios and copper loadings, but with the same Cu/Al ratio and, therefore, th e same copper exchange level have similar catalytic activity profiles for NO SCR. It was further observed that not all Cu cations exchanged into MFI catalysts have equivalent catalytic activity for NO SCR, whic h made the existence of different copper environments on CuMFI catalys ts evident, isolated Cu2+ ions being the most active species for NO SC R by propene. Moreover, the results showed an improvement of the CuMFI catalytic activity at low temperatures by increasing the catalyst cop per exchange level and, consequently, decreasing the number of Bronste d acid sites, which can be performed either by increasing the zeolite Si/Al ratio or copper loading.