Effect of Si/Al Ratio on the Performance of Mo/ZSM-5 Catalysts for Selective Catalytic Reduction of NO

Three Mo/ZSM-5 catalysts from different HZSM-5 were prepared by wet impregnation method and their catalytic activity has also been tested. The results showed that the catalytic performance for NO selective catalytic reduction over 1# catalyst which has the lowest value of Si/Al ratio is much better than 2# and 3# catalysts at the same experiment condition, its NO conversion reaches 94% at 530 ℃, while only 48% and 41% was given by 2# and 3# catalyst. To understand the effect of different Si/Al ratio on the activity of Mo/ZSM-5, the bulk-phase and surface compositions of the catalysts were determined by XRD, XPS and NO-TPD respectively. The results showed that Mo/ZSM-5 catalysts with different Si/Al ratio not only exhibits an obvious difference of catalytic activity for selective catalytic reduction of NO, but also results in the distinction of bulk phase structure and surface properties. Especially the different surface Mo contents may cause the difference in activity of three Mo/ZSM-5 catalysts.