Résumé
Copper K-offretite catalysts prepared by ion exchange were characterized by XRD, H2-TPR and evaluated in the selective catalytic reduction of NO (NO-SCR) by ammonia. Despite several successive exchanges, the quantity of copper introduced remains low and the exchange ratio does not exceed 50%. The NO conversion profiles have a sigmoid curve shape. Full NO conversion in N2 is reached above 340 C at a volume space velocity of 332,000 h 1. N2O formation at low temperature is due to the presence of small oxide particles generated by the successive copper exchanges during the preparation. The presence of K ions ‘‘blocks'' the cancrinite access to copper ions and maintains the deNOx efficiency over the whole range of temperature.