NOX ABATEMENT IN LEAN EXHAUST-GAS CONDITIONS OVER METAL SUBSTRATED ZEOLITE CATALYSTS

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