NOx abatement in lean exhaust gas conditions over metal substrated zeolite catalysts

Metal substrated ZSM-5 zeolites ion-exchanged with copper are effective catalysts in the elimination of nitrogen oxides from lean automotive exhaust gases when propene works as a reductant. Some co-cations improve the catalytic activity of CU-ZSM-5. The critical temperature for the deactivation of Cu ZSM-5 catalysts is around 700 degrees C where the state of copper begins to change resulting in the decrease of the catalytic activity. The structure of the Cu-ZSM-5 zeolite collapses after thermal aging at temperatures above 800 degrees C. However, the coexistence of chromium in the zeolite increases the thermal stability of Cu-ZSM-5 considerably.