"NO abatement with CH4 in the presence of O2 on H-ZSM5 with Si/Al=15-200: the dependence of activity on the proton concentration"

The abatement of NO with methane in the presence of oxygen was studied on commercial H-ZSM5 samples with Si/Al = 15-200 in a conventional flow apparatus. H-ZSM5 samples were used in the acid form or after exchanging protons with sodium ions to various extents. Their catalytic activity was compared with that of commercial H-mordenite and H-Y. On all H-ZSM5 catalysts, reaction rates RNO and RCH4 (molecules s-1 g-1) increased proportionally to the proton concentration, showing that either all protons or a constant fraction of them were equally active. On sodium-exchanged H-ZSM5 samples with Si/Al = 15-17, both RNO and RCH4 nearly exponentially increased with the proton concentration. Conversely, on sodium-exchanged H-ZSM5 with Si/Al = 50, both RNO and RCH4 linearly increased with the proton concentration. At lower Si/Al ratios, replacing the H-ZSM5 protons with sodium ions partly inactivated the remaining protons.